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  • 301. Ali, Qasim
    et al.
    Haider, Muhammad Zulqurnain
    Iftikhar, Wasif
    Jamil, Sidra
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Department of Botany, Faculty of Science and Technology, Government College University, Faisalabad, Pakistan.
    Javed, M. Tariq
    Noman, Ali
    Iqbal, Muhammad
    Perveen, Rashida
    Drought tolerance potential of Vigna mungo L. lines as deciphered by modulated growth, antioxidant defense, and nutrient acquisition patterns2016In: Revista Brasileira de Botânica, ISSN 0100-8404, E-ISSN 1806-9959, Vol. 39, no 3, p. 801-812Article in journal (Refereed)
    Abstract [en]

    Water shortage is one of the major environmental constraints that hamper the crop productivity worldwide. The present study was aimed to examine the drought tolerance potential of seven cultivars/lines of Vigna mungo L. depending upon their germination behavior, seedling growth, antioxidative defense mechanism, and nutrient acquisition. An experiment was conducted in the growth chamber using petri-plates and laid out in a completely randomized design (CRD). Hoagland's nutrient solution supplemented with 12 % PEG-8000 (drought treatment) or without PEG-800 (control) was used. Drought stress significantly altered the germination attributes as well as biomass production of all the studied cultivars/lines. Least adversative effects of drought stress were recorded in lines M-01001-1 and M-6036-21, respectively. The studied cultivars/lines exhibited differential response for various biochemical attributes under drought stress. The maximum increase in MDA and SOD activities and protein content was recorded in line M-603621, while the maximum AsA was recorded in line M-01001-1. Drought stress resulted in a significant reduction of plant N, P, K, Ca, and Mg contents, while the plant iron (Fe) contents remained unaffected. Results revealed that cultivars/lines M-01001-1 and M-6036-21 exhibited enhanced performance in terms of nutrient acquisition when stressed by drought. Based upon seed germination behavior, plant biomass production, biochemical attributes and mineral elements, the cultivars/lines M-01001-1 and M-6036-21 were identified as drought tolerant, while M-97 and Arroj-II were identified as drought sensitive.

  • 302. Ali, S
    et al.
    Moslem, W.M.
    Shukla, P.K.
    Umeå University, Faculty of Science and Technology, Physics.
    Schlickeiser, R.
    Linear and nonlinear ion-acoustic waves in an unmagnetized electron-positron-ion quantum plasma2007In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 14, p. 82307-Article in journal (Refereed)
  • 303. Ali, S
    et al.
    Moslem, WM
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck Institut für extraterrestrische Physik, D-85741 Garching, Germany; GoLP/Instituto Superior Técnico, 1049-001 Lisbon, Portugal; CCLRC Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, UK; SUPA Department of Physics, University of Strathclyde, Glasgow G 40NG, UK.
    Wake potential with mobile positive/negative ions in multicomponent dusty plasmas2008In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 372, no 44, p. 6650-6652Article in journal (Refereed)
    Abstract [en]

    We employ the test charge approach to calculate the electrostatic potential for a test charge in a multicomponent dusty plasma, whose constituents are the Boltzmann distributed electrons, mobile positive and negative ions, and immobile positive/negative charged dust particles. By using the modified dielectric constant of the dust-ion-acoustic (DIA) waves, the Debye screening and wake potentials are obtained. It is found that the presence of mobile negative ions significantly modify the DIA speed and the wake potential. The present results are relevant to polar mesosphere and microelectronic in the context of charged particle attraction and repulsion.

  • 304. Ali, S
    et al.
    Shukla, P. K.
    Umeå University, Faculty of Science and Technology, Physics.
    Streaming instability in quantum dusty plasmas2007In: European Physical Journal D: Atomic, Molecular and Optical Physics, ISSN 1434-6060, E-ISSN 1434-6079, Vol. 41, p. 319-Article in journal (Refereed)
  • 305. Ali, S
    et al.
    Shukla, Padma K
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck Institut für extraterrestrische Physik, D-85741 Garching, Germany, GoLP/Instituto Superior Técnico, 1049-001 Lisbon, Portugal, Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, United Kingdom, and Department of Physics, University of Strathclyde, Glasgow, Scotland, United Kingdom .
    Dust acoustic solitary waves in a quantum plasma2006In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 13, no 2, article id 022313Article in journal (Refereed)
    Abstract [en]

    By employing one-dimensional quantum hydrodynamic (QHD) model for a three species quantum plasma, nonlinear properties of dust acoustic solitary waves are studied. For this purpose a Korteweg-de Vries (KdV) equation is derived, incorporating quantum corrections. The quantum mechanical effects are also examined numerically both on the profiles of the amplitude and the width of dust acoustic solitary waves. It is found that the amplitude remains constant but the width shrinks for different values of a dimensionless electron quantum parameter H-e=root(Z(d0)h(2)omega(2)(pd))/m(e)m(d)C(d)(4), where Z(d0) is the dust charge state, h is the Planck constant divided by 2 pi, omega(pd) is the dust plasma frequency, m(e) (m(d)) is the electron (dust) mass, and C-d is the dust acoustic speed.

  • 306. Ali, S
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck Institut für extraterrestrische Physik, D-85741 Garching, Germany; GoLP/Instituto Superior Técnico, 1049-001 Lisbon, Portugal; Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, United Kingdom; Department of Physics, University of Strathclyde, Glasgow, Scotland, United Kingdom.
    Dispersion properties of compressional electromagnetic waves in quantum dusty magnetoplasmas2006In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 13, no 5, article id 052113Article in journal (Refereed)
    Abstract [en]

    A new dispersion relation for low-frequency compressional electromagnetic waves is derived by employing quantum magnetohydrodynamic model and Maxwell equations in cold quantum dusty magnetoplasmas. The latter is composed of inertialess electrons, mobile ions, and immobile charged dust particulates. The dispersion relation for the low-frequency compressional electromagnetic modes is further analyzed for the waves propagating parallel, perpendicular, and oblique to the external magnetic field direction. It is found theoretically and numerically that the quantum parameter alpha(q)=(n(i0)/n(e0))h(2)/(4m(e)m(i)) affects the real angular frequencies and the phase speeds of the compressional electromagnetic modes. Here, n(i0) (n(e0)) is the equilibrium number density of the ions (electrons), m(e) (m(i)) is the electron (ion) mass, and h is the Plank constant divided by 2 pi.

  • 307.
    Ali, Sabrina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Säker och effektiv insulinterapi hos barn med diabetes typ 1: En jämförelse mellan insulinpumpsbehandling och injektionsbehandling2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 308.
    Ali, Shahid
    Umeå University, Faculty of Science and Technology, Physics.
    Waves and instabilities in quantum plasmas2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The study of waves and instabilities in quantum plasmas is of fundamental importance for understanding collective interactions in superdense astrophysical objects, in high intense laser-plasma/solid-matter interactions, in microelectronic devices and metallic nanostructures. In dense quantum plasmas, there are new pressure laws associated with the Fermi-Dirac distribution functions and new quantum forces associated with the quantum Bohm potential and the Bohr magnetization involving electron ½ spin. These forces significantly alter the collective behavior of dense quantum plasmas. This thesis contains six papers, considering several novel collective modes and instabilities at quantum scales. In Paper I, we have used the quantum hydrodynamical (QHD) model for studying the one-dimensional dust-acoustic (DA) waves incorporating the Fermi pressure law and the quantum Bohm potential. The latter modifies the DA wave dispersion relation in a collisional plasma. In Paper II, we have calculated the electrostatic potential of a test charge in an unmagnetized electron-ion quantum plasma. It is found that the Debye-Hückel and oscillatory wake potentials strongly depend upon the Fermi energy at quantum scales. The results can be of interest for explaining the charged particle attraction and repulsion in degenerate quantum plasmas, such as those in semiconductor and microelectronic devices. Paper III presents the parametric study of nonlinear electrostatic waves in two-dimensional collisionless quantum dusty plasmas. A reductive perturbation method has been employed to the QHD equations together with the Poisson equation, obtaining the cylindrical Kadomtsev-Petviashvili (CKP) equations and their stationary localized solutions. We have numerically examined the quantum mechanical and geometrical effects on the profiles of nonplanar quantum dust-ion-acoustic (DIA) and DA solitary waves. The role of static as well as mobile (negatively or positively charged) dust particles on the low-frequency electrostatic waves has also been highlighted for metallic nanostructures. Paper IV introduces the nonlinear properties of the ion-sound waves in a dense electron-ion Fermi magnetoplasma. The computational analysis of the nonlinear system reveals that the Sagdeev-like potential and the ion-sound density excitations are significantly affected by the wave direction cosine and the Mach number at quantum scales. Paper V considers the nonlinear interactions of electrostatic upper-hybrid (UH), ion-cyclotron (IC), lower-hybrid (LH), and Alfvén waves in a quantum magnetoplasma. The nonlinear dispersion relations have been analyzed analytically to obtain the growth rates for both the decay and modulational instabilities involving the dispersive IC, LH, and Alfvén waves. In Paper VI, we have identified a new drift-like dissipative instability in a collisional quantum plasma. The modified unstable drift-like mode can cause cross-field anomalous ion-diffusion at quantum scales.

  • 309.
    Ali, Shahid
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Moslem, W. M.
    Kourakis, I.
    Shukla, Padma
    Parametric study of nonlinear electrostatic waves in two-dimensional quantum dusty plasmasManuscript (Other academic)
  • 310.
    Ali, Shahid
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Moslem, W. M.
    Shukla, Padma
    Kourakis, I
    Fully nonlinear ion-sound waves in a dense Fermi magnetoplasma2007In: Physics Letters A, ISSN 0375-9601, Vol. 366, no 9, p. 606-610Article in journal (Refereed)
  • 311.
    Ali, Shahid
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Shukla, Nitin
    Shukla, Padma
    Instability of drift-like waves and cross-field charged particle transport in a nonuniform collisional quantum magnetoplasma2007In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 78, no 4, p. 45001-Article in journal (Refereed)
  • 312.
    Ali, Shahid
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Shukla, Padma
    Potential distributions around a moving test charge in quantum plasmas2006In: Physics of Plasmas, ISSN 1070-664X, Vol. 13, no 10, p. 102112-Article in journal (Refereed)
  • 313.
    Ali, W
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Georgsson, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hellström, Thomas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Visual tree detection for autonomous navigation in forest environment2008In: IEEE Intelligent Vehicles SymposiumConference Location: Eindhoven, NETHERLANDS, 2008, , p. 1144-1149p. 1144-1149Conference paper (Refereed)
    Abstract [en]

    This paper describes a classification based tree detection method for autonomous navigation of forest vehicles in forest environment. Fusion of color, and texture cues has been used to segment the image into tree trunk and background objects. The segmentation of images into tree trunk and background objects is a challenging task due to high variations of illumination, effect of different color shades, non-homogeneous bark texture, shadows and foreshortening. To accomplish this, the approach has been to find the best combinations of color, and texture descriptors, and classification techniques. An additional task has been to estimate the distance between forest vehicle and the base of segmented trees using monocular vision. A simple heuristic distance measurement method is proposed that is based on pixel height and a reference width. The performance of various color and texture operators, and accuracy of classifiers has been evaluated using cross validation techniques.

  • 314.
    Alice, Berglund
    Umeå University, Faculty of Science and Technology, Umeå School of Architecture.
    Art for/by Youth2017Independent thesis Basic level (degree of Bachelor of Fine Arts), 10 credits / 15 HE creditsStudent thesis
  • 315.
    Ali-Eldin, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Capacity Scaling for Elastic Compute Clouds2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    AbstractCloud computing is a computing model that allows better management, higher utiliza-tion and reduced operating costs for datacenters while providing on demand resourceprovisioning for different customers. Data centers are often enormous in size andcomplexity. In order to fully realize the cloud computing model, efficient cloud man-agement software systems that can deal with the datacenter size and complexity needto be designed and built.This thesis studies automated cloud elasticity management, one of the main andcrucial datacenter management capabilities. Elasticity can be defined as the abilityof cloud infrastructures to rapidly change the amount of resources allocated to anapplication in the cloud according to its demand. This work introduces algorithms,techniques and tools that a cloud provider can use to automate dynamic resource pro-visioning allowing the provider to better manage the datacenter resources. We designtwo automated elasticity algorithms for cloud infrastructures that predict the futureload for an application running on the cloud. It is assumed that a request is either ser-viced or dropped after one time unit, that all requests are homogeneous and that it takesone time unit to add or remove resources. We discuss the different design approachesfor elasticity controllers and evaluate our algorithms using real workload traces. Wecompare the performance of our algorithms with a state-of-the-art controller. We ex-tend on the design of the best performing controller out of our two controllers anddrop the assumptions made during the first design. The controller is evaluated with aset of different real workloads.All controllers are designed using certain assumptions on the underlying systemmodel and operating conditions. This limits a controller’s performance if the modelor operating conditions change. With this as a starting point, we design a workloadanalysis and classification tool that assigns a workload to its most suitable elasticitycontroller out of a set of implemented controllers. The tool has two main components,an analyzer and a classifier. The analyzer analyzes a workload and feeds the analysisresults to the classifier. The classifier assigns a workload to the most suitable elasticitycontroller based on the workload characteristics and a set of predefined business levelobjectives. The tool is evaluated with a set of collected real workloads and a set ofgenerated synthetic workloads. Our evaluation results shows that the tool can help acloud provider to improve the QoS provided to the customers.

  • 316.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    El-Ansary, Sameh
    Nile University.
    Optimizing Replica Placement in Peer-Assisted Cloud Stores2011Conference paper (Refereed)
    Abstract [en]

    Peer-assisted cloud storage systems use the unutilizedresources of the clients subscribed to a storage cloudto offload the servers of the cloud. The provider distributesdata replicas on the clients instead of replicating on the localinfrastructure. These replicas allow the provider to providea highly available, reliable and cheap service at a reducedcost. In this work we introduce NileStore, a protocol forreplication management in peer-assisted cloud storage. Theprotocol converts the replica placement problem into a lineartask assignment problem. We design five utility functionsto optimize placement taking into account the bandwidth,free storage and the size of data in need of replication oneach peer. The problem is solved using a suboptimal greedyoptimization algorithm. We show our simulation results usingthe different utilities under realistic network conditions. Ourresults show that using our approach offloads the cloud serversby about 90% compared to a random placement algorithmwhile consuming 98.5% less resources compared to a normalstorage cloud.

  • 317.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    El-Ansary, Sameh
    Nile University.
    Replica Placement in Peer-Assisted Clouds: An Economic Approach2011In: Lecture Notes in Computer Science / [ed] Pascal Felber, Romain Rouvoy, Springer, 2011, p. 208-213Conference paper (Refereed)
    Abstract [en]

    We introduce NileStore, a replica placement algorithm based on an economical model for use in Peer-assisted cloud storage. The algorithm uses storage and bandwidth resources of peers to offload the cloud provider’s resources. We formulate the placement problem as a linear task assignment problem where the aim is to minimize time needed for file replicas to reach a certain desired threshold. Using simulation, We reduce the probability of a file being served from the provider’s servers by more than 97.5% under realistic network conditions.

  • 318.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ilyushkin, Alexey
    Ghit, Bogdan
    Herbst, Nikolas Roman
    Papadopoulos, Alessandro
    Losup, Alexandru
    Which Cloud Auto-Scaler Should I Use for my Application?: Benchmarking Auto-Scaling Algorithms2016In: PROCEEDINGS OF THE 2016 ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE'16), Association for Computing Machinery (ACM), 2016, p. 131-132Conference paper (Refereed)
  • 319.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Lund University.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Analysis and characterization of a Video-on-Demand service workload2015In: Proceedings of the 6th ACM Multimedia Systems Conference, MMSys 2015, ACM Digital Library, 2015, p. 189-200Conference paper (Refereed)
    Abstract [en]

    Video-on-Demand (VoD) and video sharing services accountfor a large percentage of the total downstream Internet traf-fic. In order to provide a better understanding of the loadon these services, we analyze and model a workload tracefrom a VoD service provided by a major Swedish TV broad-caster. The trace contains over half a million requests gener-ated by more than 20000 unique users. Among other things,we study the request arrival rate, the inter-arrival time, thespikes in the workload, the video popularity distribution, thestreaming bit-rate distribution and the video duration distri-bution. Our results show that the user and the session ar-rival rates for the TV4 workload does not follow a Poissonprocess. The arrival rate distribution is modeled using a log-normal distribution while the inter-arrival time distributionis modeled using a stretched exponential distribution. Weobserve the “impatient user” behavior where users abandonstreaming sessions after minutes or even seconds of startingthem. Both very popular videos and non-popular videos areparticularly affected by impatient users. We investigate ifthis behavior is an invariant for VoD workloads.

  • 320.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Dept. of Electrical and Information Technology, Lund University, Lund, Sweden.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Efficient provisioning of bursty scientific workloads on the cloud using adaptive elasticity control2012In: Proceedings of the 3rd workshop on Scientific Cloud Computing Date, Association for Computing Machinery (ACM), 2012, p. 31-40Conference paper (Refereed)
    Abstract [en]

    Elasticity is the ability of a cloud infrastructure to dynamically change theamount of resources allocated to a running service as load changes. We build anautonomous elasticity controller that changes the number of virtual machinesallocated to a service based on both monitored load changes and predictions offuture load. The cloud infrastructure is modeled as a G/G/N queue. This modelis used to construct a hybrid reactive-adaptive controller that quickly reactsto sudden load changes, prevents premature release of resources, takes intoaccount the heterogeneity of the workload, and avoids oscillations. Using simulations with Web and cluster workload traces, we show that our proposed controller lowers the number of delayed requests by a factor of 70 for the Web traces and 3 for the cluster traces when compared to a reactive controller. Ourcontroller also decreases the average number of queued requests by a factor of 3 for both traces, and reduces oscillations by a factor of 7 for the Web traces and 3 for the cluster traces. This comes at the expense of between 20% and 30% over-provisioning, as compared to a few percent for the reactive controller.

  • 321.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Rezaie, Ali
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Mehta, Amardeep
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Razroev, Stanislav
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Sjöstedt-de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Seleznjev, Oleg
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    How will your workload look like in 6 years?: Analyzing Wikimedia's workload2014In: Proceedings of the 2014 IEEE International Conference on Cloud Engineering (IC2E 2014) / [ed] Lisa O’Conner, IEEE Computer Society, 2014, p. 349-354Conference paper (Refereed)
    Abstract [en]

    Accurate understanding of workloads is key to efficient cloud resource management as well as to the design of large-scale applications. We analyze and model the workload of Wikipedia, one of the world's largest web sites. With descriptive statistics, time-series analysis, and polynomial splines, we study the trend and seasonality of the workload, its evolution over the years, and also investigate patterns in page popularity. Our results indicate that the workload is highly predictable with a strong seasonality. Our short term prediction algorithm is able to predict the workload with a Mean Absolute Percentage Error of around 2%.

  • 322.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Seleznjev, Oleg
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Sjöstedt-de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Measuring cloud workload burstiness2014In: 2014 IEEE/ACM 7th International Conference on Utility and Cloud Computing (UCC), IEEE conference proceedings, 2014, p. 566-572Conference paper (Refereed)
    Abstract [en]

    Workload burstiness and spikes are among the main reasons for service disruptions and decrease in the Quality-of-Service (QoS) of online services. They are hurdles that complicate autonomic resource management of datacenters. In this paper, we review the state-of-the-art in online identification of workload spikes and quantifying burstiness. The applicability of some of the proposed techniques is examined for Cloud systems where various workloads are co-hosted on the same platform. We discuss Sample Entropy (SampEn), a measure used in biomedical signal analysis, as a potential measure for burstiness. A modification to the original measure is introduced to make it more suitable for Cloud workloads.

  • 323.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    An adaptive hybrid elasticity controller for cloud infrastructures2012In: 2012 IEEE Network operations and managent symposium (NOMS), IEEE Communications Society, 2012, p. 204-212Conference paper (Refereed)
    Abstract [en]

    Cloud elasticity is the ability of the cloud infrastructure to rapidly change the amount of resources allocated to a service in order to meet the actual varying demands on the service while enforcing SLAs. In this paper, we focus on horizontal elasticity, the ability of the infrastructure to add or remove virtual machines allocated to a service deployed in the cloud. We model a cloud service using queuing theory. Using that model we build two adaptive proactive controllers that estimate the future load on a service. We explore the different possible scenarios for deploying a proactive elasticity controller coupled with a reactive elasticity controller in the cloud. Using simulation with workload traces from the FIFA world-cup web servers, we show that a hybrid controller that incorporates a reactive controller for scale up coupled with our proactive controllers for scale down decisions reduces SLA violations by a factor of 2 to 10 compared to a regression based controller or a completely reactive controller.

  • 324.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Lund University.
    WAC: A Workload analysis and classification tool for automatic selection of cloud auto-scaling methodsManuscript (preprint) (Other academic)
    Abstract [en]

    Autoscaling algorithms for elastic cloud infrastructures dynami-cally change the amount of resources allocated to a service ac-cording to the current and predicted future load. Since there areno perfect predictors, no single elasticity algorithm is suitable foraccurate predictions of all workloads. To improve the quality ofworkload predictions and increase the Quality-of-Service (QoS)guarantees of a cloud service, multiple autoscalers suitable for dif-ferent workload classes need to be used. In this work, we intro-duce WAC, a Workload Analysis and Classification tool that as-signs workloads to the most suitable elasticity autoscaler out of aset of pre-deployed autoscalers. The workload assignment is basedon the workload characteristics and a set of user-defined Business-Level-Objectives (BLO). We describe the tool design and its maincomponents. We implement WAC and evaluate its precision us-ing various workloads, BLO combinations and state-of-the-art au-toscalers. Our experiments show that, when the classifier is tunedcarefully, WAC assigns between 87% and 98.3% of the workloadsto the most suitable elasticity autoscaler.

  • 325.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Department of Electrical and Information Technology, Lund University, Lund, Sweden.
    Workload Classification for Efficient Auto-Scaling of Cloud Resources2013Manuscript (preprint) (Other academic)
    Abstract [en]

    Elasticity algorithms for cloud infrastructures dynamically change the amount of resources allocated to a running service according to the current and predicted future load. Since there is no perfect predictor, and since different applications’ workloads have different characteristics, no single elasticity algorithm is suitable for future predictions for all workloads. In this work, we introduceWAC, aWorkload Analysis and Classification tool that analyzes workloads and assigns them to the most suitable elasticity controllers based on the workloads’ characteristics and a set of business level objectives.

    WAC has two main components, the analyzer and the classifier. The analyzer analyzes workloads to extract some of the features used by the classifier, namely, workloads’ autocorrelations and sample entropies which measure the periodicity and the burstiness of the workloads respectively. These two features are used with the business level objectives by the clas-sifier as the features used to assign workloads to elasticity controllers. We start by analyzing 14 real workloads available from different applications. In addition, a set of 55 workloads is generated to test WAC on more workload configurations. We implement four state of the art elasticity algorithms. The controllers are the classes to which the classifier assigns workloads. We use a K nearest neighbors classifier and experiment with different workload combinations as training and test sets. Our experi-ments show that, when the classifier is tuned carefully, WAC correctly classifies between 92% and 98.3% of the workloads to the most suitable elasticity controller.

  • 326.
    Ali-Eldin Hassan, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Workload characterization, controller design and performance evaluation for cloud capacity autoscaling2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis studies cloud capacity auto-scaling, or how to provision and release re-sources to a service running in the cloud based on its actual demand using an auto-matic controller. As the performance of server systems depends on the system design,the system implementation, and the workloads the system is subjected to, we focuson these aspects with respect to designing auto-scaling algorithms. Towards this goal,we design and implement two auto-scaling algorithms for cloud infrastructures. Thealgorithms predict the future load for an application running in the cloud. We discussthe different approaches to designing an auto-scaler combining reactive and proactivecontrol methods, and to be able to handle long running requests, e.g., tasks runningfor longer than the actuation interval, in a cloud. We compare the performance ofour algorithms with state-of-the-art auto-scalers and evaluate the controllers’ perfor-mance with a set of workloads. As any controller is designed with an assumptionon the operating conditions and system dynamics, the performance of an auto-scalervaries with different workloads.In order to better understand the workload dynamics and evolution, we analyze a6-years long workload trace of the sixth most popular Internet website. In addition,we analyze a workload from one of the largest Video-on-Demand streaming servicesin Sweden. We discuss the popularity of objects served by the two services, the spikesin the two workloads, and the invariants in the workloads. We also introduce, a mea-sure for the disorder in a workload, i.e., the amount of burstiness. The measure isbased on Sample Entropy, an empirical statistic used in biomedical signal processingto characterize biomedical signals. The introduced measure can be used to charac-terize the workloads based on their burstiness profiles. We compare our introducedmeasure with the literature on quantifying burstiness in a server workload, and showthe advantages of our introduced measure.To better understand the tradeoffs between using different auto-scalers with differ-ent workloads, we design a framework to compare auto-scalers and give probabilisticguarantees on the performance in worst-case scenarios. Using different evaluation cri-teria and more than 700 workload traces, we compare six state-of-the-art auto-scalersthat we believe represent the development of the field in the past 8 years. Knowingthat the auto-scalers’ performance depends on the workloads, we design a workloadanalysis and classification tool that assigns a workload to its most suitable elasticitycontroller out of a set of implemented controllers. The tool has two main components;an analyzer, and a classifier. The analyzer analyzes a workload and feeds the analysisresults to the classifier. The classifier assigns a workload to the most suitable elasticitycontroller based on the workload characteristics and a set of predefined business levelobjectives. The tool is evaluated with a set of collected real workloads, and a set ofgenerated synthetic workloads. Our evaluation results shows that the tool can help acloud provider to improve the QoS provided to the customers.

  • 327.
    Alin, Lars
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Object Tracking withIphone 3Gs2010Independent thesis Advanced level (degree of Master (One Year)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    In June of 2007 Apple Inc. released the smartphone Iphone. It was a groundbreaking success that set a new standard for what a smartphone should be able to do. Apple has improved the Iphone every year since then and the 3Gs is the newest Iphone model. As the phones have improved, both when looking at hardware and software, the applications have improved as well. The Iphone 3Gs provides the possibility to use the camera as an application background and with that the possibility to analyze the surroundings, making it possible to track objects that the phone is pointed towards.This thesis examines how object tracking can be implemented in applications for Iphone 3Gs as well as providing a survey of four different areas of use that have been implemented in Xcode: an augmented reality car game, a letter tracking application, a face recognition application and an object recognition application.

  • 328. Aljetlawi, A A
    et al.
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Leonardsson, K
    Effect of food and sediment pre-treatment in experiments with a deposit-feeding amphipod, Monoporeia affinis2000In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 249, no 2, p. 263-280Article in journal (Refereed)
    Abstract [en]

    We experimentally investigated the effects of different pre-treatments of the sediment, and the effect of daily addition of fresh phytoplankton, on the growth and survival of 1-year-old (1 +) individuals of the deposit feeder Monoporeia affinis (Amphipoda). We used three different types of sieved sediment: pre-frozen muddy clay, non-pre-frozen muddy clay, and fine sand. The muddy clay contained phytoplankton originating from the surface sediment sampled in the field during the late spring bloom. No phytoplankton was initially present in sand. The experiment lasted for 18 days. M. affinis responded to the daily phytoplankton addition by increasing growth. Phytoplankton addition had no significant effects on the survival of M. affinis. Upon phytoplankton addition, the sandy and non-frozen muddy clay gave similar growth and survival responses. In contrast, the pre-frozen sediment resulted in significantly lower growth and survival. The growth was negative in all treatments without phytoplankton. Thus, the high initial chlorophyll content in the muddy clay was not of sufficient quality or concentration to allow a positive growth response in M. affinis. The growth of M. affinis was significantly correlated with the reduction of the chlorophyll. Our results indicated that M. affinis is capable of assimilating settled phytoplankton with no, or only a few days' time delay. (C) 2000 Elsevier Science BN: All rights reserved.

  • 329. Aljetlawi, A A
    et al.
    Sparrevik, E
    Leonardsson, K
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Prey-predator size-dependent functional response: derivation and rescaling to the real world2004In: J. Animal Ecology, Vol. 73, p. 239-252Article in journal (Refereed)
  • 330.
    Alkhabbaz, Mohammed
    et al.
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506, USA.
    Abidakun, Olatunde
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506, USA.
    Valiev, Damir
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education of China, Department of Energy and Power Engineering, Tsinghua University, Beijing, China.
    Akkerman, V’yacheslav
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506, USA.
    Impact of the Lewis number on finger flame acceleration at the early stage of burning in channels and tubes2019In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 31, no 8, article id 083606Article in journal (Refereed)
    Abstract [en]

    For premixed combustion in channels and tubes with one end open, when a flame is ignited at the centerline at the closed end of the pipe and it propagates toward the open one, significant flame acceleration occurs at an early stage of the combustion process due to formation of a finger-shaped flame front. This scenario is tagged “finger flame acceleration” (FFA), involving an initially hemispherical flame kernel, which subsequently acquires a finger shape with increasing surface area of the flame front. Previous analytical and computational studies of FFA employed a conventional assumption of equidiffusivity when the thermal-to-mass-diffusivity ratio (the Lewis number) is unity (Le = 1). However, combustion is oftentimes nonequidiffusive (Le ≠ 1) in practice such that there has been a need to identify the role of Le in FFA. This demand is addressed in the present work. Specifically, the dynamics and morphology of the Le ≠ 1 flames in two-dimensional (2D) channels and cylindrical tubes are scrutinized by means of the computational simulations of the fully compressible reacting flow equations, and the role of Le is identified. Specifically, the Le > 1 flames accelerate slower as compared with the equidiffusive ones. In contrast, the Le < 1 flames acquire stronger distortion of the front, experience the diffusional-thermal combustion instability, and thereby accelerate much faster than the Le = 1 flames. In addition, combustion in a cylindrical configuration shows stronger FFA than that under the same burning conditions in a 2D planar geometry.

  • 331. Allakhverdiev, Suleyman I.
    et al.
    Zharmukhamedov, Sergey K.
    Rodionova, Margarita V.
    Shuvalov, Vladimir A.
    Dismukes, Charles
    Shen, Jian-Ren
    Barber, James
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Govindjee,
    Vyacheslav (Slava) Klimov (1945-2017): A scientist par excellence, a great human being, a friend, and a Renaissance man2018In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 136, no 1, p. 1-16Article in journal (Other academic)
    Abstract [en]

    Vyacheslav Vasilevich (V.V.) Klimov (or Slava, as most of us called him) was born on January 12, 1945 and passed away on May 9, 2017. He began his scientific career at the Bach Institute of Biochemistry of the USSR Academy of Sciences (Akademy Nauk (AN) SSSR), Moscow, Russia, and then, he was associated with the Institute of Photosynthesis, Pushchino, Moscow Region, for about 50 years. He worked in the field of biochemistry and biophysics of photosynthesis. He is known for his studies on the molecular organization of photosystem II (PSII). He was an eminent scientist in the field of photobiology, a well-respected professor, and, above all, an outstanding researcher. Further, he was one of the founding members of the Institute of Photosynthesis in Pushchino, Russia. To most, Slava Klimov was a great human being. He was one of the pioneers of research on the understanding of the mechanism of light energy conversion and of water oxidation in photosynthesis. Slava had many collaborations all over the world, and he is (and will be) very much missed by the scientific community and friends in Russia as well as around the World. We present here a brief biography and some comments on his research in photosynthesis. We remember him as a friendly and enthusiastic person who had an unflagging curiosity and energy to conduct outstanding research in many aspects of photosynthesis, especially that related to PSII.

  • 332. Allan, Mohammed
    et al.
    Le Roux, Gael
    De Vleeschouwer, Francois
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Blaauw, Maarten
    Piotrowska, Natalia
    Sikorski, Jaroslaw
    Fagel, Nathalie
    High-resolution reconstruction of atmospheric deposition of trace metals and metalloids since AD 1400 recorded by ombrotrophic peat cores in Hautes-Fagnes, Belgium2013In: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 178, p. 381-394Article in journal (Refereed)
    Abstract [en]

    The objective of our study was to determine the trace metal accumulation rates in the Misten bog, Hautes-Fagnes, Belgium, and assess these in relation to established histories of atmospheric emissions from anthropogenic sources. To address these aims we analyzed trace metals and metalloids (Pb, Cu, Ni, As, Sb, Cr, Co, V, Cd and Zn), as well as Pb isotopes, using XRF, Q-ICP-MS and MC-ICP-MS, respectively in two 40-cm peat sections, spanning the last 600 yr. The temporal increase of metal fluxes from the inception of the Industrial Revolution to the present varies by a factor of 5-50, with peak values found between AD 1930 and 1990. A cluster analysis combined with Pb isotopic composition allows the identification of the main sources of Pb and by inference of the other metals, which indicates that coal consumption and metallurgical activities were the predominant sources of pollution during the last 600 years.

    (c) 2013 Elsevier Ltd. All rights reserved.

  • 333. Allard, Christina
    et al.
    Axelsson, Per
    Umeå University, Faculty of Arts, Centre for Sami Research.
    Brännlund, Isabelle
    Umeå University, Faculty of Arts, Centre for Sami Research.
    Cocq, Coppélie
    Umeå University, Faculty of Arts, Department of language studies.
    Hjortfors, Lis-Mari
    Umeå University, Faculty of Arts, Department of language studies. Umeå University, Faculty of Arts, Centre for Sami Research.
    Jacobsson, Lars
    Umeå University, Faculty of Medicine, Department of Clinical Sciences.
    Ledman, Anna-Lill
    Umeå University, Faculty of Arts, Centre for Sami Research.
    Löf, Annette
    Umeå University, Faculty of Arts, Centre for Sami Research.
    Johansson Lönn, Eva
    Umeå University, Faculty of Arts, Department of culture and media studies.
    Moen, Jon
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Lena Maria
    Umeå University, Arctic Research Centre at Umeå University.
    Nordin, Gabriella
    Umeå University, Arctic Research Centre at Umeå University.
    Nordlund, Christer
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies.
    Norlin, Björn
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies.
    Outakoski, Hanna
    Umeå University, Faculty of Arts, Department of language studies.
    Reimerson, Elsa
    Umeå University, Faculty of Social Sciences, Department of Political Science.
    Sandström, Camilla
    Umeå University, Faculty of Social Sciences, Department of Political Science.
    Sandström, Moa
    Umeå University, Faculty of Arts, Centre for Sami Research. Umeå University, Faculty of Arts, Department of language studies.
    Sehlin MacNeil, Kristina
    Umeå University, Faculty of Arts, Department of culture and media studies.
    Sköld, Peter
    Umeå University, Faculty of Arts, Centre for Sami Research.
    Stoor, Krister
    Umeå University, Faculty of Arts, Department of language studies.
    Storm Mienna, Christina
    Umeå University, Faculty of Arts, Centre for Sami Research.
    Svonni, Charlotta
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies.
    Vinka, Mikael
    Össbo, Åsa
    Umeå University, Faculty of Arts, Department of language studies.
    Rasbiologiskt språkbruk i statens rättsprocess mot sameby2015In: Dagens Nyheter, ISSN 1101-2447Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Statens hantering av forskningsresultat i rättsprocessen med Girjas sameby utgör ett hot mot Sverige som rättsstat och kunskapsnation. Åratal av svensk och internationell forskning underkänns och man använder ett språkbruk som skulle kunna vara hämtat från rasbiologins tid. Nu måste staten ta sitt ansvar och börja agera som en demokratisk rättsstat, skriver 59 forskare.

  • 334.
    Allard, Ingrid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Achieving building energy performance: requirements and evaluation methods for residential buildings in Sweden, Norway, and Finland2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Building energy performance has always been important in the cold climate of Sweden, Norway and Finland. To meet the goal that all new buildings should be nearly zero-energy buildings by 2020, set in the EU directive 2010/31/EU [1] on the energy performance of buildings (EPBD recast), the building sector in Europe now faces a transition towards buildings with improved energy performance. In such a transition, a discussion is needed about the objective of the improvement – why, or to what end, the building energy performance should be improved. The objective of improving building energy performance is often a political decision, but scientific research can contribute with knowledge on how the objectives can be achieved.

    This thesis addresses how the indicators used in the requirements used to achieve building energy performance in Sweden, Norway, and Finland, and the methods used to evaluate these requirements, reflect building energy performance. It also addresses difficulties in achieving comparable and verifiable indicators in evaluations of building energy performance. The research objective has two parts: to review, compare, and discuss (i) requirements and (ii) evaluation methods used to achieve energy performance of residential buildings in Sweden, Norway and Finland. The work in this thesis includes reviews of the requirements used in national building codes and passive house criteria to achieve building energy performance, of methods used to evaluate compliance with such requirements, and of methods used specifically to evaluate the indicator Envelope Air Tightness.

    The results show that different sets of indicators are used to achieve building energy performance in the studied building codes and passive house criteria. The methods used to evaluate compliance with requirements used to achieve building energy performance are also different, but calculation methods are generally more often used than measurement methods. The calculation- and measurement methods used are often simple. A methodology to analyze the deviation between predictions- and measurements of building energy performance (the performance gap) was developed, to investigate the effects of different evaluation methods on different indicators used to achieve building energy performance. The methodology was tested in a case-study. This study indicated that the choice of method affects which parts of the performance gap reflected in the indicators Supplied Energy (see Terminology), Net Energy (see Terminology), and Overall U-value. Among the reviewed methods to evaluate air tightness, the Fan/Blower Door Pressurization is well known and preferred by professionals in the field. The results in this thesis may be useful when choosing indicators and evaluation methods to achieve different objectives of improving building energy performance and in the quest towards comparable and verifiable indicators used to achieve building energy performance.

  • 335.
    Allard, Ingrid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nära-nollenergibyggnader2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The new EU directive EPBD2, Energy Performance of Buildings Directive (recast), adopted 2010, specifies that all new buildings must be so-called nearly-zero-energy-buildings by year 2021. A nearly-zero-energy-building is a building with very high energy performance, which is provided with renewable energy to a large extent. How this should be interpreted and where the requirement is to be placed on energy usage is up to each country to decide. There is currently a debate about this going on in Sweden, and the Swedish Energy Agency has been asked to design a strategy to meet the goals for nearly-zero-energy-buildings. The environmental goal for reducing the carbon footprint by 2020 and 2050 is also closely linked to this question. In order to set a reasonable level of requirement for energy use, both economic-, technical- and environmental aspects must be taken into account. This report studies a new building area in Västra Sörhaga, Alingsås, to find out how to build it in order to achieve the standard for nearly-zero-energy-buildings. A wider study is also made to find out where it is reasonable to set the level of requirements for energy use for nearly-zero-energybuildings throughout the country. The energy calculation software VIP-energy is used for simulating four buildings, off different sizes, and studying their energy consumption.

    Where the system boundary is placed has a big impact on the outcome of the measurement of a building's energy use. EPBD2 determines that the building's energy performance should be a priority, before the supply of renewable energy sources. In order to attain a building with a high energy performance, an optimized construction performance is first required, with an airtight and highly insulated building envelope and a ventilation system with heat recovery, and then an efficient energy system and an efficient energy supply should be ensured. When this is reached, the focus can then be put on making sure that the energy supplied is renewable to as large extent as possible. It is therefore important to optimize the building performance first and then take the energy supply system and energy sources into account, whereby the building also has a low primary energy use and is supplied with as much renewable and environmentally friendly energy as possible.

    The Swedish Energy Agency’s proposes an energy requirement of half the current energy requirements as a goal for nearly-zero-energy-buildings. One example of energy reducing measures that would result in achieving this standard for a cottage in Kiruna is: elimination of thermal bridges, heat exchange of the ventilation air with 90 % efficiency, windows with a heat transfer coefficient of 0.7 W/m2K and doors with 0.6 W/m2K, airtightness of 0.2 l/s,m2 and a window proportion of 10 %. This is a stretch of what is possible to achieve with today’s technology. Heat exchangers with an efficiency of 90 % exist today, but since they require defrosting in cold climate, which decreases the real efficiency, it could be difficult to achieve in Kiruna. However, with future technological developments and experiences of building low energy buildings, this would be a reasonable standard for nearly-zero-energy-buildings throughout the country. It would also be advantageous to divide the country into more climate zones, or at least divide them more equally. The variation in energy use for a building is today much larger in the most northern climate zone than in the southernmost.

    thermal bridges, heat exchange of the ventilation air with 90 % efficiency, windows with a heat transfer coefficient of 0.7 W/m2K and doors with 0.6 W/m2K, airtightness of 0.2 l/s,m2 and a window proportion of 10 %. This is a stretch of what is possible to achieve with today’s technology. Heat exchangers with an efficiency of 90 % exist today, but since they require defrosting in cold climate, which decreases the real efficiency, it could be difficult to achieve in Kiruna. However, with future technological developments and experiences of building low energy buildings, this would be a reasonable standard for nearly-zero-energy-buildings throughout the country. It would also be advantageous to divide the country into more climate zones, or at least divide them more equally. The variation in energy use for a building is today much larger in the most northern climate zone than in the southernmost.

    It would be possible to use the passive house standard requirements for nearly-zero-energybuildings in the southern parts of Sweden, but it is not recommended in the north. Especially small buildings are very difficult to build in the passive house standard in cold climates today. To reach passive house standard for a small building in the northern most part of Sweden could require an indoor temperature no higher than 20°C and an airtightness of 0.1 l/s,m2. This is not reasonable, mostly because it is common to have a higher indoor temperature in Sweden and because this very high air tightness cannot be guaranteed today. The area in Västra Sörhaga, Alingsås, is realistic to build with requirements of passive house standard because it is in climate zone III, and that would almost certainly also satisfy the standard for nearly-zero-energy-buildings. If the area was built in the passive house standard it would result in a total specific energy consumption of around 50 kWh/m2 per year, which is 45 % of the energy use for the same area built to meet today’s energy requirements.

    The national board of housing’s proposed energy requirements for the revision of the construction rules for 2011 are deemed not to be ambitious enough and makes it very difficult to achieve environmental objectives by 2020. Further studies need to be made on the economic viability of buildings with low energy use, and in order to assess the amount of energy in a uniform manner, primary energy factors need to be developed. These should include both efficiency in manufacturing, energy form and energy sources. Energy sources, in turn, should be judged by the degree of renewability, access and storage capacity. Construction of low-energy buildings requires a large change in the existing construction market and energy structure. We have to start now to achieve this by 2021!

  • 336.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hassan, Osama
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energy evaluation methods for  residential buildings in Nordic countries2012In: Proceeding of the Technoport Conference, Elsevier, 2012Conference paper (Refereed)
    Abstract [en]

    To meet the goals of the directive 2010/31/EU on the energy performance of buildings, the building sector in Europe now faces a transition towards more energy efficient buildings. Research and development of new energy solutions and technology will be necessary for the transition and the importance of measuring and evaluating building energy performance increases. This paper attempts to review and evaluate different methods that are commonly used to analyze energy performance in residential buildings in Nordic countries, primarily in Sweden, Norway and Finland. A short international review of regulations is also included. Some advantages and disadvantages of each method are discussed, as well as commonly used methods in the three countries. Although the three Nordic countries have similar climate conditions and building traditions, the study shows that there exist relatively large variations in defining parameters related to energy performance in residential buildings, such as energy use, heated area, and climate zones. The outcome of the regulations could be investigated by adapting the codes on a selected set of buildings. Common analyzing methods, or parts of methods, are found to be used in several countries. These aspects may be considered in further work to develop more accurate and easily comparable methods to evaluate energy performance for residential buildings in cold climate.

  • 337.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hassan, Osama
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Methods for air tightness analysis for residential buildings in Nordic countries2012In: Methods for air tightness analysis forresidential buildings in Nordic countries, Southampton: WIT Press, 2012, p. 311-322Conference paper (Refereed)
    Abstract [en]

    Envelope air tightness is one factor that has impact on the energy performance ofbuildings. The goals of the directive 2010/31/EU, on energy performance ofbuildings, raise the importance of building energy performance analysis in theprocess. Measurements of air tightness can be useful both when evaluatingbuilding energy performance and developing new building techniques. The aimof this paper is to review and evaluate methods to measure air tightness in bothnew and existing residential buildings in Sweden, Norway and Finland, based onan international literature study and a survey. The methods are categorized basedon a number of criteria to determine their suitability in different situations.Advantages and disadvantages of the methods are discussed, as well ascommonly used methods in the three countries. The review shows that thestandard ISO 9972 is used for verification in all three countries, but alternativesexist that might be more suitable in certain situations. Simpler methods are usedin the building process to increase air tightness. To achieve a comparablemeasurement, both common methods and commonly defined units are needed.

  • 338.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hassan, Osama A. B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Methods for energy analysis of residential buildings in Nordic countries2013In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 22, p. 306-318Article, review/survey (Refereed)
    Abstract [en]

    To meet the goals of the directive 2010/31/EU on the energy performance of buildings, the building sector in Europe now faces a transition towards more energy efficient buildings. Research and development of new energy solutions and technology will be necessary for the transition and the importance of analyzing building energy performance increases. This paper aims to review and evaluate different methods that are commonly used to analyze energy performance in residential buildings in Nordic countries, primarily in Sweden, Norway and Finland. A short international review of regulations is also included. The goal is to find commonly used methods and possibilities for the future. The introduced methods are summarized, categorized and compared based on their advantages and disadvantages. Although the three Nordic countries have similar climate conditions and building traditions, the review shows relatively large variations in the definitions of energy performance for residential buildings, as well as variations in how measurements and calculations are used in the methods for energy performance analysis. In the conducted review, methods, or parts of methods, are also found to be used. The methods used to analyze energy performance are found to be more similar than the concepts of energy performance itself in the three countries. These aspects may be considered in further work to develop an international policy practice for energy performance of residential buildings in cold climate.

  • 339.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nair, Gireesh
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energy evaluation of residential buildings: Performance gap analysis incorporating uncertainties in the evaluation methods2018In: Building Simulation, ISSN 1996-3599, E-ISSN 1996-8744, Vol. 11, no 4, p. 725-737Article in journal (Refereed)
    Abstract [en]

    Calculation and measurement-based energy performance evaluations of the same building often provide different results. This difference is referred as "the performance gap". However, a large performance gap may not necessarily mean that there are flaws in the building or deviations from the intended design. The causes for the performance gap can be analysed by calibrating the simulation model to measured data. In this paper, an approach is introduced for verifying compliance with energy performance criteria of residential buildings. The approach is based on a performance gap analysis that takes the uncertainties in the energy evaluation methods into consideration. The scope is to verify building energy performance through simulation and analysis of measured data, identifying any performance gap due to deviations from the intended design or flaws in the finished building based on performance gap analysis. In the approach, a simulation model is calibrated to match the heat loss coefficient of the building envelope [kWh/K] instead of the measured energy. The introduced approach is illustrated using a single-family residential building. The heat loss coefficient was found useful towards identifying any deviations from the intended design or flaws in the finished building. The case study indicated that the method uncertainty was important to consider in the performance gap analysis and that the proposed approach is applicable even when the performance gap appears to be non-existing.

  • 340.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nair, Gireesh
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energy performance indicators in the Swedish building procurement process2017In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 9, no 10, article id 1877Article in journal (Refereed)
    Abstract [en]

    In Sweden, all new buildings need to comply with the National Board of Housing, Building and Planning’s requirement on specific purchased energy (kWh/m2). Accordingly, this indicator is often used to set design criteria in the building procurement process. However, when energy use is measured in finished buildings, the measurements often deviate significantly from the design calculations. The measured specific purchased energy does not necessarily reflect the responsibility of the building contractor, as it is influenced by the building operation, user behavior and climate. Therefore, Swedish building practitioners may prefer other indicators for setting design criteria in the building procurement process. The aim of this study was twofold: (i) to understand the Swedish building practitioners’ perspectives and opinions on seven building energy performance indicators (envelope air leakage, U-values for different building parts, average U-value, specific heat loss, heat loss coefficient, specific net energy, and specific purchased energy); and (ii) to understand the consequences for the energy performance of multi-family buildings of using the studied indicators to set criteria in the procurement process. The study involved a Delphi approach and simulations of a multi-family case study building. The studied indicators were discussed in terms of how they may meet the needs of the building practitioners when used to set building energy performance criteria in the procurement process.

  • 341.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    A methodology to investigate the building energy performance gap2015In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118Article in journal (Other academic)
    Abstract [en]

    In order to evaluate compliance with requirements on building energy performance, it is necessary to find strategies to process discrepancies from the results of forward simulations in the design stage and of measurements in the operated stage. The gap between designed performance and measured performance is referred to as the “performance gap”. It can be divided into a procurement gap (between intended design and verified performance) and an operational gap (between verified performance and non-normalized measurements).  

    In this work we introduced a methodology for performance gap analysis, based on separating the procurement- and operational gap. An important component to do this is calibrations of calculations using measured data. The suggested methodology allows for more detailed verifications of building energy performance and can be used to study how indicators reflect the performance gap. The proposed methodology is tested using data from a well-documented and measured operated single family building, in sub-arctic climate in Sweden.

    The indicators studied in the verification were carefully analyzed. The methodology was found reliable based on the obtained results and a sensitivity analysis. An overall observation is that the applicability of the methodology depends on the accuracy of the hybrid method. The accuracy of the performance gap analysis per definition depends on the available information of the operated building, and consequently to access to extensive measured data.

  • 342.
    Allberg, Nina
    Umeå University, Faculty of Science and Technology, Umeå School of Architecture.
    Agrihome: The vertical ommunity2019Independent thesis Basic level (degree of Bachelor of Fine Arts), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Have you ever thought about how dependent you are of the systems in society - the government, the municipalities, and the economy in an everyday life perspective? Probably you have, but have you thought about how much? Imagine a day when it is -20°C outside and the power goes off. What do you do?

    If you are not prepared - like most Swedes aren’t - you soon have no way of heating your home, put on the lights, cook food or take a warm shower. Today you are supposed to be able to survive without governments help for one week in case of a crisis. Most of us can’t manage that.

    I think it’s absurd how much we all depend on these systems. It’s scary. The population of the world is growing and by 2050, 75% of the population will be living in and around cities. Today 42% of the worlds land surface is used for farmland. Can we expect that the government will provide food for all of us? We need to be able to be self-sufficient within the borders of the city, and not only in the countryside.

    My project is not about going off the grid and being 100% self-sufficient. It’s an experiment to see if it is possible for people to live without governments help to provide power, food, water and heat in a city environment, both in the everyday life and in case of crises.  It´s about taking small steps for helping the environment, ourselves and society. Being self-sufficient doesn’t mean you can’t keep your job or your hobbies; today the technology is so developed, making it possible to be self-sufficient without having to give up our time. The project will be placed on a vertical scale to make the footprint as small as possible and to see how many people it is possible to host in that limited area.

    The programs in the project are divided into three categories: food production, technology, and social programs. In my research, I’ve mainly focused on food production using both vertical farming and traditional farming. Other systems that I also focused on are the technological aspects for creating a passive building and a bioclimatic design using passive solar systems.

    The site that I have chosen is on Ön, an island in central Umeå. For several decades, several generations of politicians in Umeå have discussed the future of the island but have now proposed a new city plan with a total of 3600 apartments. The planning is based on building ecologically, economically, technically as well as socially sustainable, which I’m hoping to achieve with my project. My plan is to take over a small block for my project, thus the design is adapted to the site and its conditions.

  • 343.
    Allegrini, Elisa
    et al.
    Technical University of Denmark, Department of Environmental Engineering.
    Boldrin, Alessio
    Tech Univ Technical University of Denmark, Department of Environmental Engineering.
    Jansson, Stina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundtorp, Kasper
    Babcock & Wilcox Vølund A/S, Göteborg, Sweden.
    Fruergaard Astrup, Thomas
    Technical University of Denmark, Department of Environmental Engineering.
    Quality and generation rate of solid residues in the boiler of a waste-to-energy plant2014In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 270, p. 127-136Article in journal (Refereed)
    Abstract [en]

    The Danish waste management system relies significantly on waste-to-energy (WtE) plants. The ash produced at the energy recovery section (boiler ash) is classified as hazardous waste, and is commonly mixed with fly ash and air pollution control residues before disposal. In this study, a detailed characterization of boiler ash from a Danish grate-based mass burn type WtE was performed, to evaluate the potential for improving ash management. Samples were collected at 10 different points along the boiler's convective part, and analysed for grain size distribution, content of inorganic elements, polychlorinated dibenzo-. p-dioxins and dibenzofurans (PCDD and PCDF), and leaching of metals. For all samples, PCDD and PCDF levels were below regulatory limits, while high pH values and leaching of e.g. Cl were critical. No significant differences were found between boiler ash from individual sections of the boiler, in terms of total content and leaching, indicating that separate management of individual ash fractions may not provide significant benefits. 

  • 344. Allgardsson, Anders
    et al.
    Andersson, C. David
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Akfur, Christine
    Worek, Franz
    Linusson, Anna
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ekström, Fredrik
    An unusual dimeric inhibitor of acetylcholinesterase: cooperative binding of crystal violet2017In: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 22, no 9, article id 1433Article in journal (Refereed)
    Abstract [en]

    Acetylcholinesterase (AChE) is an essential enzyme that terminates cholinergic transmission by a rapid hydrolysis of the neurotransmitter acetylcholine. AChE is an important target for treatment of various cholinergic deficiencies, including Alzheimer's disease and myasthenia gravis. In a previous high throughput screening campaign, we identified the dye crystal violet (CV) as an inhibitor of AChE. Herein, we show that CV displays a significant cooperativity for binding to AChE, and the molecular basis for this observation has been investigated by X-ray crystallography. Two monomers of CV bind to residues at the entrance of the active site gorge of the enzyme. Notably, the two CV molecules have extensive intermolecular contacts with each other and with AChE. Computational analyses show that the observed CV dimer is not stable in solution, suggesting the sequential binding of two monomers. Guided by the structural analysis, we designed a set of single site substitutions, and investigated their effect on the binding of CV. Only moderate effects on the binding and the cooperativity were observed, suggesting a robustness in the interaction between CV and AChE. Taken together, we propose that the dimeric cooperative binding is due to a rare combination of chemical and structural properties of both CV and the AChE molecule itself.

  • 345. Allgardsson, Anders
    et al.
    Berg, Lotta
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Akfur, Christine
    Hörnberg, Andreas
    Worek, Franz
    Linusson, Anna
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ekström, Fredrik J.
    Structure of a prereaction complex between the nerve agent sarin, its biological target acetylcholinesterase, and the antidote HI-62016In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 113, no 20, p. 5514-5519Article in journal (Refereed)
    Abstract [en]

    Organophosphorus nerve agents interfere with cholinergic signaling by covalently binding to the active site of the enzyme acetylcholinesterase (AChE). This inhibition causes an accumulation of the neurotransmitter acetylcholine, potentially leading to overstimulation of the nervous system and death. Current treatments include the use of antidotes that promote the release of functional AChE by an unknown reactivation mechanism. We have used diffusion trap cryocrystallography and density functional theory (DFT) calculations to determine and analyze prereaction conformers of the nerve agent antidote HI-6 in complex with Mus musculus AChE covalently inhibited by the nerve agent sarin. These analyses reveal previously unknown conformations of the system and suggest that the cleavage of the covalent enzyme-sarin bond is preceded by a conformational change in the sarin adduct itself. Together with data from the reactivation kinetics, this alternate conformation suggests a key interaction between Glu202 and the O-isopropyl moiety of sarin. Moreover, solvent kinetic isotope effect experiments using deuterium oxide reveal that the reactivation mechanism features an isotope-sensitive step. These findings provide insights into the reactivation mechanism and provide a starting point for the development of improved antidotes. The work also illustrates how DFT calculations can guide the interpretation, analysis, and validation of crystallographic data for challenging reactive systems with complex conformational dynamics.

  • 346.
    Alm, Johannes
    Umeå University, Faculty of Science and Technology, Umeå School of Architecture.
    There is a Time and Place for Spontaneity2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 347.
    Almfelt, Josephine
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Plastic acceleration of metamorphosis in the common frog (Rana temporaria) in response to pool drying: the effect of geographical isolationStudent thesis
  • 348.
    Almgren, Mattias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Effekten av dagsljus- och närvarostyrd LED-belysning i en befintlig kontorsbyggnad ur energi-, ekonomi- och ljusmiljösynpunkt2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    An important measure to reduce buildings’ environmental impact is to make the artificial lighting more effective, which is the biggest electricity consumer of Swedish office buildings and accounts for more than 30 % of the total electricity consumption.A case study has been carried out in this master thesis as a part in an existing project with ÅF Lighting, where new strategic avenues has been explored in which to combine day- and electrical light in office landscapes in a smarter, more energy-efficient manner and at the same time improve the lighting environment.Two office spaces at the own head office of ÅF in Solna, Stockholm has been used in the case study, where two different LED lighting solutions got installed. One with pendant luminaries, desk lamps and downlights, and one with only recessed luminaires.Through several computer simulations, electricity and light measurements, questionnaires, interviews etc., it has been investigated how the heat and cooling load, electricity consumption, lighting quality and operating costs has been affected of the change of the lighting system. The lighting environment, daylight conditions, heat and cooling load, economical savings and electricity consumption for the two offices has been investigated in diaLUX, DIVA-for-Rhino, IDA ICE 4.7, ecoCALC and Mitec Monitor, respectively. The electricity measurements showed that the lighting solutions’ electricity consumption got reduced with 71,6 % on floor 5 and 68,1 % on floor 10 with the new LED lighting solutions and control systems during the investigated month.Through the IDA ICE energy simulations over a year it was shown that the total yearly cooling load to floor 5 and floor 10 got reduced with 19 % and 17 %, which can be explained by the lesser heat gain from the more energy efficient lighting and the controlling of this. Though a small increase in heating load, the total energy consumption got reduced with around 12-14 % on both floors. The simulations also showed that the total electricity consumption of the lighting got reduced with 70 % for floor 5 and 63 % for floor 10 after the change to the new LED lighting solutions and implementation of control systems.The LCC for the new lighting solutions showed that these have a higher investment cost than the total operation cost for the existing solution over the life cycle. However, the costs to run the LED solutions are less than a third of the operation costs for the existing solution, and after the exchange the carbon dioxide emissions can be reduced with close to 70 %.Through this case study it has been shown that the energy consumption from lighting can be highly reduced with the installation of energy efficient lighting in combination with smart control systems, and it can also have a positive effect on the lighting environment. However, the high investment costs of the LED solutions lead to the conclusion that installation of these solutions today is not economically justifiable.

  • 349.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    SESSION 3, Chemical neuroscience and selected short talks: Pilicides & curlicides –antibacterial agents targeting bacterial virulence2011Conference paper (Other academic)
  • 350.
    Almqvist, Fredrik
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Manner, Sophie
    Thornqvist, Viveca
    Berg, Ulf
    Wallin, Margareta
    Frejd, Torbjörn
    Umeå University, Faculty of Science and Technology, Chemistry.
    Spirobicyclo[2.2.2]octane derivatives: mimetics of baccatin III and paclitaxel (Taxol)2004In: ORGANIC & BIOMOLECULAR CHEMISTRY, ISSN 1477-0520, Vol. 2, no 21, p. 3085-90Article in journal (Refereed)
    Abstract [en]

    The formylated spirobyclic alcohol 8a was computer modeled to be a mimetic of paclitaxel. In this model, the formyl group was used as a truncated paclitaxel side chain in order to reduce the computational work. Compound 8c, carrying the paclitaxel side chain, was synthesized in six steps from optically active 1,3-diketone 12. Microtubule stabilization was not observed for 8c, indicating that the model needs to be adjusted.

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