Die urbane Wärmebelastung unter Einfluss lokaler Faktoren und zukünftiger Klimaänderungen

Hinsichtlich der Klimaerwärmung kommt der Quantifizierung der Wärmebelastung eine bedeutende Rolle zu. Deshalb werden die Anzahl, Andauer und Stärke von Wärmebelastungen für Deutschland anhand eines Ensembles regionaler Klimasimulationen untersucht; dabei werden auch die Zusammenhänge mit Wetterlagen für vergangene und zukünftige Dekaden dargestellt. Auf lokaler Ebene werden die urbanen Effekte von Karlsruhe und Freiburg auf Wärmebelastungen mittels hoch aufgelöster Modellierung analysiert

UTCI climatology and its future change in Germany – an RCM ensemble approach

n the present study, the quantity, duration and intensity of heat stress events in Germany as well as their future change and relation with weather types were investigated. A small ensemble of regional climate simulations with the regional climate model (RCM) COSMO-CLM driven by four general circulation models (GCMs) was used to calculate the Universal Thermal Climate Index (UTCI); the UTCI is a well-accepted thermal comfort index which we use here to quantify thermal stress. The variables entering the UTCI were bias corrected with a method that preserves their interdependencies. The projected climate changes cause a significant increase of both the mean UTCI and the number, duration and intensity of heat stress events between the control period (1981–2000) and the projection period (2031–2050). The projected future hourly frequency distribution of the UTCI at a location can be described by a shift to higher UTCI values with an almost constant shape of distribution. The investigations of the projected changes in weather types show no significant changes between the periods covered, with a few exceptions. An exception concerning heat stress events is the increase of summer anticyclonic weather types. Although more anticyclonic weather types in summer lead to an increase in heat stress events, they are not the primary cause of the projected increases. Rather, it turns out that the characteristics of the air masses associated with the weather types change towards warmer and more humid conditions

Multiprogrammed Parallel Application Scheduling in NUMA Multiprocessors

The invention, acceptance, and proliferation of multiprocessors are primarily a result of the quest to increase computer system performance. The most promising features of multiprocessors are their potential to solve problems faster than previously possible and to solve larger problems than previously possible. Large-scale multiprocessors offer the additional advantage of being able to execute multiple parallel applications simultaneously. The execution time of a parallel application is directly related to the number of processors it is allocated and, in shared-memory non-uniform memory access time (NUMA) multiprocessors, which processors it is allocated. As a result, efficient and effective scheduling becomes critical to overall system performance. In fact, it is likely to be a contributing factor in ultimately determining the success or failure of shared-memory NUMA multiprocessors. The subjects of this dissertation are the problems of processor allocation and application placement. ..

Lower Bounds for Two-Terminal Network Reliability

One measure of two-terminal network reliability, termed probabilistic connectedness, is the probability that two specified communication centers can communicate. A standard model of a network is a graph in which nodes represent communications centers and edges represent links between communication centers. Edges are assumed to have statistically independent probabilities of failing and nodes are assumed to be perfectly reliable. Exact calculation of two-terminal reliability for general networks has been shown to be #Pcomplete. As a result is desirable to compute upper and lower bounds that avoid the exponential computation likely required by exact algorithms. Two methods are considered for computing lower bounds on two-terminal reliability in polynomial time. One method uses subgraph counting techniques and estimates of subgraph counts to obtain the Kruskal-Katona bounds. The development of the KruskalKatona bounds is outlined along with a method for improving the bounds. The other met..