The Thesis focused on hardware based Load balancing solution of web traffic through a load balancer F5 content switch. In this project, the implemented scenario for distributing HTTPtraffic load is based on different CPU usages (processing speed) of multiple member servers.Two widely used load balancing algorithms Round Robin (RR) and Ratio model (weighted Round Robin) are implemented through F5 load balancer. For evaluating the performance of F5 content switch, some experimental tests has been taken on implemented scenarios using RR and Ratio model load balancing algorithms. The performance is examined in terms of throughput (bits/sec) and Response time of member servers in a load balancing pool. From these experiments we have observed that Ratio Model load balancing algorithm is most suitable in the environment of load balancing servers with different CPU usages as it allows assigning the weight according to CPU usage both in static and dynamic load balancing of servers.

Fires, with their sudden appearance and destructive character, cause property losses beside much more death and injury especially in cities. Providing fire safety is a multi-faceted context that is related with staff, vehicle, equipment, function, organization, technology, education and consciousness. These are related, indirectly, with spatial organization that is the other side of the issue: they affect space or they are affected from space. In research context, the fire stations are evaluated as a unit of emergency and land use element of urban space. By associating the concepts related to emergency management and to urban scale, the space-time relation is examined in urban areas. This research bases on the spatial deficiencies of fire stations in urban areas which are reasons of the fire losses. Level of laws and regulations in Turkey for spatial requirements are examined. Site selection and design criteria of fire stations are evaluated with available information about implications in Ankara case study. As a result of the interviews that have been made to top executive of fire station, it is found that process of site selection and design of fire stations is going on with subjective experiences in urban space. In conclusion of the research, it is displayed that the decisions about the site selection and design of the fire stations are related to not only population criterion, but also many issues in macro-meso-micro scales. It is considered that the set of multi-criteria that are reached in this regard will provide contribution in legal organization and developing the standards.

There are widely used computers in agricultural mobile technique, which show important parameters of work process and its quality in. It is important a good illumination of workplace for quick and correct information identification from the VDT’s. There are forming different levels of illumination in agricultural technique cabins when they are working at the field. Those levels are fluctuating and operator’s eye should adapt to them compulsory. Operator’s vision feels fatigue because of those processes and work becomes not so effective. There are assessed in the work, that luminance increase on the VDT screen, as do illumination level in the cabins of agricultural mobile technique and as a result of this process, contrast reduces and visibility become worse. In experiment, there was researched, that tasks were performed quicker, when illumination was 300 -500 lx, and slower, when - 900-1200 lx. There are assessed the response time dependence on illumination level model , which helps to calculate the duration of operator’s watching, which influences the results of work quality and safety.

The object of the study is young women's volleyball players' psychomotoric reaction. The work problem - the psychomotoric reaction changes in one-year workout cycle of young women's volleyball players - is being seen now as a rather new and almost unexplored both in theory and practice. The purpose of the work is to explore possibilities of establishing and developing psychomotoric factors of young women's volleyball players in one-year workout cycle. In order to solve this problem, the following tasks were set: · To explore motion velocity factors of young women's volleyball players right and left hands, depending on the complexity of exercises; · To compare specific features both of right and left hand psychomotoric reactions of the young women's volleyball players; · To evaluate changes in response time and motion velocity during one-year workout cycle. · To evaluate strategies of motion performance in respect of velocity. We have carried out a study with players from the Lithuanian young women's volleyball players' team who are preparing themselves for the European Volleyball Championship of the year 2007. In the first study, there were 17 members of the Lithuanian young women's volleyball players' team who participated in this research, and in the second study - 15 members. The age of young players ranges from 15 to 16 years. The average age of persons under the study (young women's volleyball players) during the first stage of the study is that of 15.58±0.12 years. The... [to full text]

We consider a single-part, two-echelon supply chain problem for spare parts. The network consists of a single manufacturing plant, a set of service centers (SCs) and a set of customers. Both echelons keep spare parts using the base-stock replenishment policy. The plant behaves as an M/M/1 queueing system and has limited production and storage capacity. Demand faced by each SC follows an independent Poisson process. The problem is to determine optimal location-allocation and optimal base-stock levels at both echelons while satisfying the target service levels and customer preferences of SCs. We develop a mixed integer non-linear programming model and use cutting-plane method to optimize the inventory-location decisions. We present an exact solution procedure for the inventory stocking problem and demonstrate the limitations of using traditional inventory models like METRIC-like and Approximate in case of high utilization rates. We show the effectiveness of our proposed cutting-plane algorithm and provide important managerial insights for spare parts management.

Les temps de réponse dans une tache de reconnaissance d’objets visuels diminuent de façon significative lorsque les cibles peuvent être distinguées à partir de deux attributs redondants. Le gain de redondance pour deux attributs est un résultat commun dans la littérature, mais un gain causé par trois attributs redondants n’a été observé que lorsque ces trois attributs venaient de trois modalités différentes (tactile, auditive et visuelle). La présente étude démontre que le gain de redondance pour trois attributs de la même modalité est effectivement possible. Elle inclut aussi une investigation plus détaillée des caractéristiques du gain de redondance. Celles-ci incluent, outre la diminution des temps de réponse, une diminution des temps de réponses minimaux particulièrement et une augmentation de la symétrie de la distribution des temps de réponse. Cette étude présente des indices que ni les modèles de course, ni les modèles de coactivation ne sont en mesure d’expliquer l’ensemble des caractéristiques du gain de redondance. Dans ce contexte, nous introduisons une nouvelle méthode pour évaluer le triple gain de redondance basée sur la performance des cibles doublement redondantes. Le modèle de cascade est présenté afin d’expliquer les résultats de cette étude. Ce modèle comporte plusieurs voies de traitement qui sont déclenchées par une cascade d’activations avant de satisfaire un seul critère de décision. Il offre une approche homogène aux recherches antérieures sur le gain de redondance. L’analyse des caractéristiques des distributions de temps de réponse, soit leur moyenne, leur symétrie, leur décalage ou leur étendue, est un outil essentiel pour cette étude. Il était important de trouver un test statistique capable de refléter les différences au niveau de toutes ces caractéristiques. Nous abordons la problématique d’analyser les temps de réponse sans perte d’information, ainsi que l’insuffisance des méthodes d’analyse communes dans ce contexte, comme grouper les temps de réponses de plusieurs participants (e. g. Vincentizing). Les tests de distributions, le plus connu étant le test de Kolmogorov- Smirnoff, constituent une meilleure alternative pour comparer des distributions, celles des temps de réponse en particulier. Un test encore inconnu en psychologie est introduit : le test d’Anderson-Darling à deux échantillons. Les deux tests sont comparés, et puis nous présentons des indices concluants démontrant la puissance du test d’Anderson-Darling : en comparant des distributions qui varient seulement au niveau de (1) leur décalage, (2) leur étendue, (3) leur symétrie, ou (4) leurs extrémités, nous pouvons affirmer que le test d’Anderson-Darling reconnait mieux les différences. De plus, le test d’Anderson-Darling a un taux d’erreur de type I qui correspond exactement à l’alpha tandis que le test de Kolmogorov-Smirnoff est trop conservateur. En conséquence, le test d’Anderson-Darling nécessite moins de données pour atteindre une puissance statistique suffisante. / Response times in a visual object recognition task decrease significantly if targets can be distinguished by two redundant attributes. Redundancy gain for two attributes is a common finding, but redundancy gain from three attributes has been found only for stimuli from three different modalities (tactile, auditory, and visual). This study extends those results by showing that redundancy gain from three attributes within the visual modality is possible. It also provides a more detailed investigation of the characteristics of redundancy gain. Apart from a decrease in response times for redundant targets, these include a decrease in minimal response times and an increase in symmetry of the response time distribution. This study further presents evidence that neither race models nor coactivation models can account for all characteristics of redundancy gain. In this context, we discuss the problem of calculating an upper limit for the performance of race models for triple redundant targets, and introduce a new method of evaluating triple redundancy gain based on performance for double redundant targets. In order to explain the results from this study, the cascade race model is introduced. The cascade race model consists of several input channels, which are triggered by a cascade of activations before satisfying a single decision criterion, and is able to provide a unifying approach to previous research on the causes of redundancy gain. The analysis of the characteristics of response time distributions, including their mean, symmetry, onset, and scale, is an essential tool in this study. It was therefore important to find an adequate statistical test capable of reflecting differences in all these characteristics. We discuss the problem and importance of analysing response times without data loss, as well as the inadequacy of common methods of analysis such as the pooling of response times across participants (e.g. Vincentizing) in the present context. We present tests of distributions as an alternative method for comparing distributions, response time distributions in particular, the most common of these being the Kolmogorov-Smirnoff test. We also introduce a test yet unknown in psychology: the two-sample Anderson-Darling test of goodness of fit. We compare both tests, presenting conclusive evidence that the Anderson-Darling test is more accurate and powerful: when comparing two distributions that vary (1) in onset only, (2) in scale only, (3) in symmetry only, or (4) that have the same mean and standard deviation but differ on the tail ends only, the Anderson-Darling test proves to detect differences better than the Kolmogorov-Smirnoff test. Finally, the Anderson-Darling test has a type I error rate corresponding to alpha whereas the Kolmogorov-Smirnoff test is overly conservative. Consequently, the Anderson- Darling test requires less data than the Kolmogorov-Smirnoff test to reach sufficient statistical power.

In critical real-time systems, any faulty behavior may endanger lives. Hence, system verification and validation is essential before their deployment. In fact, safety authorities ask to ensure deterministic guarantees. In this thesis, we are interested in offering temporal guarantees; in particular we need to prove that the end-to-end response time of every flow present in the network is bounded. This subject has been addressed for many years and several approaches have been developed. After a brief comparison between the existing approaches, the Trajectory Approach sounded like a good candidate due to the tightness of its offered bound. This method uses results established by the scheduling theory to derive an upper bound. The reasons leading to a pessimistic upper bound are investigated. Moreover, since the method must be applied on large networks, it is important to be able to give results in an acceptable time frame. Hence, a study of the method's scalability was carried out. Analysis shows that the complexity of the computation is due to a recursive and iterative processes. As the number of flows and switches increase, the total runtime required to compute the upper bound of every flow present in the network understudy grows rapidly. While based on the concept of the Trajectory Approach, we propose to compute an upper bound in a reduced time frame and without significant loss in its precision. It is called the Scalable Trajectory Approach. After applying it to a network, simulation results show that the total runtime was reduced from several days to a dozen seconds.

Embedded systems are becoming ubiquitous in our daily life. Due to close interaction with physical world, embedded systems are typically subject to timing constraints. At design time, it must be ensured that the run-time behaviors of such systems satisfy the pre-specified timing constraints under any circumstance. In this thesis, we develop techniques to address the timing analysis problems brought by the increasing complexity of underlying hardware and software on different levels of abstraction in embedded systems design. On the program level, we develop quantitative analysis techniques to predict the cache hit/miss behaviors for tight WCET estimation, and study two commonly used replacement policies, MRU and FIFO, which cannot be analyzed adequately using the state-of-the-art qualitative cache analysis method. Our quantitative approach greatly improves the precision of WCET estimation and discloses interesting predictability properties of these replacement policies, which are concealed in the qualitative analysis framework. On the component level, we address the challenges raised by multi-core computing. Several fundamental problems in multiprocessor scheduling are investigated. In global scheduling, we propose an analysis method to rule out a great part of impossible system behaviors for better analysis precision, and establish conditions to guarantee the bounded responsiveness of computing tasks. In partitioned scheduling, we close a long standing open problem to generalize the famous Liu and Layland's utilization bound in uniprocessor real-time scheduling to multiprocessor systems. We also propose to use cache partitioning for multi-core systems to avoid contentions on shared caches, and solve the underlying schedulability analysis problem. On the system level, we present techniques to improve the Real-Time Calculus (RTC) analysis framework in both efficiency and precision. First, we have developed Finitary Real-Time Calculus to solve the scalability problem of the original RTC due to period explosion. The key idea is to only maintain and operate on a limited prefix of each curve that is relevant to the final results during the whole analysis procedure. We further improve the analysis precision of EDF components in RTC, by precisely bounding the response time of each computation request.

The growing interest towards wireless communication services over the recent years has increased the demand for radio spectrum. Inefficient spectrum management together with the scarcity of the radio spectrum is a limiting factor for the development of modern wireless networks. As a solution, the idea of cognitive radio networks (CRNs) is introduced to use licensed spectrum for the benefit of the unlicensed secondary users. However, the preemptive priority of the licensed users results in random resource availabilities at the secondary networks, which makes the quality-of-service (QoS) support challenging. With the increasing demand for elastic/interactive data services (internet based services) and wireless multimedia services, QoS support becomes essential for CRNs. This research investigates the voice and elastic/interactive data service support over CRNs, in terms of their delay requirements. The packet level requirements of the voice service and session level delay requirements of the elastic/interactive data services are studied. In particular, constant-rate and on-off voice traffic capacities are analyzed over CRNs with centralized and distributed network coordination. Some generic channel access schemes are considered as the coordination mechanism, and call admission control algorithms are developed for non-fully-connected CRNs. Advantage of supporting voice traffic flows with different delay requirements in the same network is also discussed. The mean response time of the elastic data traffic over a centralized CRN is studied, considering the shortest processor time with and without preemption and shortest remaining processor time service disciplines, in comparison with the processor sharing service discipline. Effects of the traffic load at the base station and file length (service time requirement) distribution on the mean response time are discussed. Finally, the relationship between the mean response times of interactive and elastic data traffic is studied.

This dissertation is concerned with the tail asymptotics of queueing networks with subexponential service time distributions. Our objective is to investigate the tail characteristics of key performance measures such as cycle times and waiting times on a variety of queueing models which may arise in many applications such as communication and manufacturing systems. First, we focus on a general class of closed feedforward fork and join queueing networks under the assumption that the service time distribution of at least one station is subexponential. Our goal is to derive the tail asymptotics of transient cycle times and waiting times. Furthermore, we argue that under certain conditions the asymptotic tail distributions remain the same for stationary cycle times and waiting times. Finally, we provide numerical experiments in order to understand how fast the convergence of tail probabilities of cycle times and waiting times is to their asymptotic counter parts. Next, we consider closed tandem queues with finite buffers between stations. We assume that at least one station has a subexponential service time distribution. We analyze this system under communication blocking and manufacturing blocking rules. We are interested in the tail asymptotics of transient cycle times and waiting times. Furthermore, we study under which conditions on system parameters a stationary regime exists and the transient results can be generalized to stationary counter parts. Finally, we provide numerical examples to understand the convergence behavior of the tail asymptotics of transient cycle times and waiting times. Finally, we study open tandem queueing networks with subexponential service time distributions. We assume that number of customers in front of the first station is infinite and there is infinite room for finished customers after the last station but the size of the buffer between two consecutive stations is finite. Using (max,+) linear recursions, we investigate the tail asymptotics of transient response times and waiting times under both communication blocking and manufacturing blocking schemes. We also discuss under which conditions these results can be generalized to the tail asymptotics of stationary response times and waiting times. Finally, we provide numerical examples to investigate the convergence of the tail probabilities of transient response times and waiting times to their asymptotic counter parts.