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Search Results: 1 - 10 of 18 matches for " Schaffrath "
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Generalized and Resource-Efficient VNet Embeddings with Migrations
Gregor Schaffrath,Stefan Schmid,Anja Feldmann
Computer Science , 2010,
Abstract: This paper attends to the problem of embedding flexibly specified CloudNets, virtual networks connecting cloud resources (such as storage or computation). We attend to a scenario where customers can request CloudNets at short notice, and an infrastructure provider (or a potential itermediate broker or reseller) first embeds the CloudNet fast (e.g., using a simple heuristic). Later, however, long-lived CloudNets embeddings are optimized by migrating them to more suitable locations, whose precise definition depends on a given objective function. For instance, such migrations can be useful to reduce the peak resource loads in the network by spreading CloudNets across the infrastructure, to save energy by moving CloudNets together and switching off unused components, or for maintenance purposes. We present a very generic algorithm to compute optimal embeddings of CloudNets: It allows for different objective functions (such as load minimization or energy conservation), supports cost-aware migration, and can deal with all link types that arise in practice (e.g., full-duplex or even wireless or wired broadcast links with multiple endpoints). Our evaluation shows that such a rigorous optimization is even feasible in order to optimize a moderate-size CloudNet of full flexibility (e.g., a router site, a small physical infrastructure or virtual provider network).
Comparison of BMI Derived from Parent-Reported Height and Weight with Measured Values: Results from the German KiGGS Study
Anna-Kristin Brettschneider,Ute Ellert,Angelika Schaffrath Rosario
International Journal of Environmental Research and Public Health , 2012, DOI: 10.3390/ijerph9020632
Abstract: The use of parent-reported height and weight is a cost-efficient instrument to assess the prevalence of children’s weight status in large-scale surveys. This study aimed to examine the accuracy of BMI derived from parent-reported height and weight and to identify potential predictors of the validity of BMI derived from parent-reported data. A subsample of children aged 2–17 years (n = 9,187) was taken from the 2003–2006 cross-sectional German KiGGS study. Parent-reported and measured height and weight were collected and BMI was calculated. Besides descriptive analysis, linear regression models with BMI difference and logistic regression models with weight status misclassification as dependent variables were calculated. Height differences varied by gender and were generally small. Weight and BMI were under-reported in all age groups, the under-reporting getting stronger with increasing age. Overall, the proportion for overweight and obesity based on parental and measured reports differed slightly. In the youngest age group, the proportion of overweight children was overestimated, while it was underestimated for older children and adolescents. Main predictors of the difference between parent reported and measured values were age, gender, weight status and parents’ perception of the child’s weight. In summary, the exclusive use of uncorrected parental reports for assessment of prevalence rates of weight status is not recommended.
内蒙古羊草和大针茅草原下垫面水汽、CO2通量输送特征
王雷-,刘辉志,David Schaffrath,Christian Bernhofer
高原气象 , 2010,
Abstract: 利用涡动相关技术对2007年8月18日~9月12日在内蒙古羊草和大针茅草原样地上进行微气象观测, 比较了两种草原生态系统下垫面水汽、 CO2通量交换的差异, 结果表明: (1)羊草样地的气温、 地表温度和水汽压较小; 羊草和大针茅样地的地表反射率平均值分别为0.17和0.16; (2)受土壤水分胁迫控制, 羊草和大针茅样地的有效能量主要分配为感热通量, 平均波文比分别为3.70和2.69, 潜热通量在大针茅样地更大, 有随着土壤湿度持续减小而减小的趋势; (3)羊草和大针茅样地在观测期间表现为CO2的源, 日均释放率分别为0.97 g·CO2·m-2·d-1和0.43 g·CO2·m-2·d-1。受土壤水分胁迫和草地生理作用的控制, 日间羊草和大针茅样地都出现了CO2通量的衰减。
Kinderwunsch bei PCO-Patientinnen
Seufert R,Passuello V,Schaffrath M,Fischl F
Journal für Fertilit?t und Reproduktion , 2006,
Abstract:
Inhibine und Aktivine - Hormonelle Faktoren mit gro er Bedeutung für die Frauenklinik
Seufert R,Fischl F,Pollow K,Schaffrath M
Journal für Fertilit?t und Reproduktion , 2005,
Abstract: Die Existenz der Inhibine als nicht-steroidale hochwirksame Botenstoffe mit hypophys rer Suppressionswirkung auf Gonadotropine wurde bereits 1932 von McCullagh im Zusammenhang mit Versuchen von wasserl slichen Gonadenextrakten bei kastrierten Ratten postuliert. Nach Isolierung und Charakterisierung wurden sie wegen ihrer starken Hemmung der FSH-Sekretion im vorderen Hyphophysenlappen als Inhibine bezeichnet. Neben der direkten hyphophys ren Wirkung sind mittlerweile weitere, überwiegend im Zusammenhang mit reproduktiven Funktionen stehendende Wirkungen bekannt, die die Inhibine als hochaktive Substanzen auszeichnen. Aus der mittlerweile gro en Zahl bekannter parakriner Effekte ist die Bedeutung von Inhibin B für die Selektion des dominanten Follikels besonders interessant, w hrend das Inhibin A unmittelbar vor der Ovulation deutlich ansteigt und dann im Corpus luteum weiter synthetisiert wird. Weitere Beobachtungen zeigen Ver nderungen für eine gro e Zahl pathophysiologischer Vorg nge z. B. die deutlich erh hten Serumkonzentrationen bei Schwangerschaftshochdruck und dem HELLP-Syndrom, sowie bei Vorliegen eines Down-Syndroms. Die Inhibine sind exzellente Marker der ovariellen Stimulation unter rFSH und k nnten mit ihren erh hten Serumspiegeln bei Patientinnen mit PCO-Syndrom die oft sehr niedrigen FSH-Serumspiegel erkl ren. Die Inhibinforschung stellt zur Zeit ein sehr interessantes und aktuelles Arbeitsgebiet der experimentellen und klinischen Reproduktionsbiologie dar, mit vielen neuen Einblicken und interessanten Anwendungsm glichkeiten. Wenn es gelingen sollte, die Inhibin- bzw. Aktivinwirkung pharmakologisch zu nutzen, k nnten v llig neuartige pharmakologische Ans tze m glich werden, die aktuell erforscht werden.
Online Strategies for Intra and Inter Provider Service Migration in Virtual Networks
Dushyant Arora,Marcin Bienkowski,Anja Feldmann,Gregor Schaffrath,Stefan Schmid
Computer Science , 2011,
Abstract: Network virtualization allows one to build dynamic distributed systems in which resources can be dynamically allocated at locations where they are most useful. In order to fully exploit the benefits of this new technology, protocols need to be devised which react efficiently to changes in the demand. This paper argues that the field of online algorithms and competitive analysis provides useful tools to deal with and reason about the uncertainty in the request dynamics, and to design algorithms with provable performance guarantees. As a case study, we describe a system (e.g., a gaming application) where network virtualization is used to support thin client applications for mobile devices to improve their QoS. By decoupling the service from the underlying resource infrastructure, it can be migrated closer to the current client locations while taking into account migration cost. This paper identifies the major cost factors in such a system, and formalizes the corresponding optimization problem. Both randomized and deterministic, gravity center based online algorithms are presented which achieve a good tradeoff between improved QoS and migration cost in the worst-case, both for service migration within an infrastructure provider as well as for networks supporting cross-provider migration. The paper reports on our simulation results and also presents an explicit construction of an optimal offline algorithm which allows, e.g., to evaluate the competitive ratio empirically.
Competitive and Deterministic Embeddings of Virtual Networks
Guy Even,Moti Medina,Gregor Schaffrath,Stefan Schmid
Computer Science , 2011,
Abstract: Network virtualization is an important concept to overcome the ossification of today's Internet as it facilitates innovation also in the network core and as it promises a more efficient use of the given resources and infrastructure. Virtual networks (VNets) provide an abstraction of the physical network: multiple VNets may cohabit the same physical network, but can be based on completely different protocol stacks (also beyond IP). One of the main challenges in network virtualization is the efficient admission control and embedding of VNets. The demand for virtual networks (e.g., for a video conference) can be hard to predict, and once the request is accepted, the specification / QoS guarantees must be ensured throughout the VNet's lifetime. This requires an admission control algorithm which only selects high-benefit VNets in times of scarce resources, and an embedding algorithm which realizes the VNet in such a way that the likelihood that future requests can be embedded as well is maximized. This article describes a generic algorithm for the online VNet embedding problem which does not rely on any knowledge of the future VNet requests but whose performance is competitive to an optimal offline algorithm that has complete knowledge of the request sequence in advance: the so-called competitive ratio is, loosely speaking, logarithmic in the sum of the resources. Our algorithm is generic in the sense that it supports multiple traffic models, multiple routing models, and even allows for nonuniform benefits and durations of VNet requests.
A Federated CloudNet Architecture: The PIP and the VNP Role
Ernesto Abarca,Johannes Grassler,Gregor Schaffrath,Stefan Schmid
Computer Science , 2013,
Abstract: We present a generic and flexible architecture to realize CloudNets: virtual networks connecting cloud resources with resource guarantees. Our architecture is federated and supports different (and maybe even competing) economical roles, by providing explicit negotiation and provisioning interfaces. Contract-based interactions and a resource description language that allows for aggregation and abstraction, preserve the different roles' autonomy without sacrificing flexibility. Moreover, since our CloudNet architecture is plugin based, essentially all cloud operating systems (e.g., OpenStack) or link technologies (e.g., VLANs, OpenFlow, VPLS) can be used within the framework. This paper describes two roles in more detail: The Physical Infrastructure Providers (PIP) which own the substrate network and resources, and the Virtual Network Providers (VNP) which can act as resource and CloudNet brokers and resellers. Both roles are fully implemented in our wide-area prototype that spans remote sites and resources.
On the Benefit of Virtualization: Strategies for Flexible Server Allocation
Dushyant Arora,Anja Feldmann,Gregor Schaffrath,Stefan Schmid
Computer Science , 2010,
Abstract: Virtualization technology facilitates a dynamic, demand-driven allocation and migration of servers. This paper studies how the flexibility offered by network virtualization can be used to improve Quality-of-Service parameters such as latency, while taking into account allocation costs. A generic use case is considered where both the overall demand issued for a certain service (for example, an SAP application in the cloud, or a gaming application) as well as the origins of the requests change over time (e.g., due to time zone effects or due to user mobility), and we present online and optimal offline strategies to compute the number and location of the servers implementing this service. These algorithms also allow us to study the fundamental benefits of dynamic resource allocation compared to static systems. Our simulation results confirm our expectations that the gain of flexible server allocation is particularly high in scenarios with moderate dynamics.
内蒙古羊草和大针茅草原下垫面水汽、CO2通量输送特征
王雷-,刘辉志,David,Schaffrath,Christian,Bernhofer
高原气象 , 2010,
Abstract: 利用涡动相关技术对2007年8月18日~9月12日在内蒙古羊草和大针茅草原样地上进行微气象观测,比较了两种草原生态系统下垫面水汽、CO2通量交换的差异,结果表明:(1)羊草样地的气温、地表温度和水汽压较小;羊草和大针茅样地的地表反射率平均值分别为0.17和0.16;(2)受土壤水分胁迫控制,羊草和大针茅样地的有效能量主要分配为感热通量,平均波文比分别为3.70和2.69,潜热通量在大针茅样地更大,有随着土壤湿度持续减小而减小的趋势;(3)羊草和大针茅样地在观测期间表现为CO2的源,日均释放率分别为0.97g·CO2·m-2·d-1和0.43g·CO2·m-2·d-1。受土壤水分胁迫和草地生理作用的控制,日间羊草和大针茅样地都出现了CO2通量的衰减。
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