Дисертації з теми "FCBFS"

In the past 10 years, the bandwidths and processing capabilities of the networks have increased dramatically. The number of real-time applications using these networks has also increased. The large number of real-time packets might, in a switched multi-hop network, lead to unpredictable traffic patterns. This is not a problem when the traffic intensity is low, but if the same network is used by a large number of users simultaneously, the overall performance of the network degrades. In fact, unpredictable delays in the delivery of the message can adversely affect the execution of the tasks dependent on these messages, even if we take into account the soft real-time performance.

In this paper, we investigate the effect of traffic shapers on soft real-time performance. We will consider a switched multi-hop network with FCFS queues. We will implement two versions of the network simulator. One version will be without traffic shaper and the other version will use a traffic shaper. By comparing the results (for average delay, deadline miss ratio etc.) from both the versions, we will try to conclude if it is really beneficial to use traffic shapers for soft real-time performance. Leaky bucket and token bucket algorithms are the most popular ones for traffic shaper implementation. We will consider leaky bucket algorithm for our analysis. We analyse different versions of the leaky bucket and present the trade-off’s involved.

Les plateformes de calcul à grande échelle ont beaucoup évoluées dernières années. La réduction des coûts des composants simplifie la construction de machines possédant des multicœurs et des accélérateurs comme les GPU.Ceci a permis une propagation des plateformes à grande échelle,dans lesquelles les machines peuvent être éloignées les unes des autres, pouvant même être situées sur différents continents. Le problème essentiel devient alors d'utiliser ces ressources efficacement.Dans ce travail nous nous intéressons d'abord à l'allocation efficace de tâches sur plateformes hétérogènes composées CPU et de GPU. Pour ce faire, nous proposons un outil nommé SWDUAL qui implémente l'algorithme de Smith-Waterman simultanément sur CPU et GPU, en choisissant quelles tâches il est plus intéressant de placer sur chaque type de ressource. Nos expériences montrent que SWDUAL donne de meilleurs résultats que les approches similaires de l'état de l'art.Nous analysons ensuite une nouvelle méthode d'ordonnancement enligne de tâches indépendantes de différentes tailles. Nous proposons une nouvelle technique qui optimise la métrique du stretch. Elle consiste à déplacer les jobs qui retardent trop de petites tâches sur des machines dédiées. Nos résultats expérimentaux montrent que notre méthode obtient de meilleurs résultats que la politique standard et qu'elle s'approche dans de nombreux cas des résultats d'une politique préemptive, qui peut être considérée comme une borne inférieure.Nous nous intéressons ensuite à l'impact de différentes contraintes sur la politique FCFS avec backfilling. La contrainte de contiguïté essaye de compacter les jobs et de réduire la fragmentation dans l'ordonnancement. La contrainte de localité basique place les jobs de telle sorte qu'ils utilisent le plus petit nombre de groupes de processeurs appelés textit. Nos résultats montrent que les bénéfices de telles contraintes sont suffisants pour compenser la réduction du nombre de jobs backfillés due à la réduction de la fragmentation.Nous proposons enfin une nouvelle contrainte nommée localité totale, dans laquelle l'ordonnanceur modélise la plateforme par un fat tree et se sert de cette information pour placer les jobs là où leur coût de communication est minimal.Notre campagne d'expériences montre que cette contrainte obtient de très bons résultats par rapport à un backfilling basique, et de meilleurs résultats que les contraintes précédentes
The field of parallel supercomputing has been changing rapidly inrecent years. The reduction of costs of the parts necessary to buildmachines with multicore CPUs and accelerators such as GPUs are ofparticular interest to us. This scenario allowed for the expansion oflarge parallel systems, with machines far apart from each other,sometimes even located on different continents. Thus, the crucialproblem is how to use these resources efficiently.In this work, we first consider the efficient allocation of taskssuitable for CPUs and GPUs in heterogeneous platforms. To that end, weimplement a tool called SWDUAL, which executes the Smith-Watermanalgorithm simultaneously on CPUs and GPUs, choosing which tasks aremore suited to one or another. Experiments show that SWDUAL givesbetter results when compared to similar approaches available in theliterature.Second, we study a new online method for scheduling independent tasksof different sizes on processors. We propose a new technique thatoptimizes the stretch metric by detecting when a reasonable amount ofsmall jobs is waiting while a big job executes. Then, the big job isredirected to separate set of machines, dedicated to running big jobsthat have been redirected. We present experiment results that show thatour method outperforms the standard policy and in many cases approachesthe performance of the preemptive policy, which can be considered as alower bound.Next, we present our study on constraints applied to the Backfillingalgorithm in combination with the FCFS policy: Contiguity, which is aconstraint that tries to keep jobs close together and reducefragmentation during the schedule, and Basic Locality, that aims tokeep jobs as much as possible inside groups of processors calledclusters. Experiment results show that the benefits of using theseconstrains outweigh the possible decrease in the number of backfilledjobs due to reduced fragmentation.Finally, we present an additional constraint to the Backfillingalgorithm called Full Locality, where the scheduler models the topologyof the platform as a fat tree and uses this model to assign jobs toregions of the platform where communication costs between processors isreduced. The experiment campaign is executed and results show that FullLocality is superior to all the previously proposed constraints, andspecially Basic Backfilling

La retine est a la fois la source et un tissu cible privilegie des formes acide et basique des fgfs (fibroblast growth factor). Ces facteurs stimulent la proliferation des neuroblastes, la differenciation des cellules gliales ainsi que leur survie. La retine neurale de poulet a la capacite de se transdifferencier en corps lentoidiens riches en cristallines et en cellules epitheliales pigmentees. Le but de ce travail a ete d'etudier les roles et implications des fgfs dans les processus de differenciation et transdifferenciation de la retine de poulet. Nous avons prealablement etudie par hybridation northern et hybridation in situ (his) la presence de deux types de recepteurs, fgf-r1 et fgf-r2 dans la retine de poulet pendant sa formation. Les etudes d'his montrent pour les deux recepteurs l'existence d'un marquage dans les trois couches nucleaires de la retine et la couche des segments internes des photorecepteurs. Nous avons ensuite effectue une recherche des marqueurs de differenciation des cellules de retine de poulet. Nous nous sommes ensuite attaches a l'etude de l'action directe de fgfa et fgfb sur des cultures de cellules dissociees de retine neurale et de retine epitheliale pigmentee d'embryons de poulet de differents stades. La proliferation cellulaire a ete evaluee par comptage et par incorporation de thymidine tritiee. Les populations cellulaires presentes ont ete identifiees par immunohistochimie. Les proteines accumulees et neosynthetisees dans ces cultures ont ete etudiees et plus particulierement la quantite de fgfa presente et l'activite acetylcholine esterase

Switched Ethernet is an Ethernet LAN that uses switches to connect individual nodes.

This is popular because of its effective and convenient way of extending the bandwidth of

existing Ethernets. Switched Ethernet is being considered by the industry community because

of its open standardization, cost effectiveness, and the support for higher data rates up to

10Gbps. Even though many special-purposed solutions were proposed to support time

constrained communication over Switched Ethernet, still there were some doubts about the

real time handling capability of Switched Ethernet. To achieve reliable transmission

guarantees for real time traffic over Switched Ethernet, it is important to measure the

performance of Switched Ethernet networks for real time communication. In this thesis work

we have observed the average end-to-end packet delay for real time traffic over a Switched

Ethernet by simulation, which is very much essential for real time communication in

industrial applications, where the communication is time-deterministic. In our thesis we used

FCFS priority queuing in both the source nodes and switch. In this thesis we also discussed

about the feasibility analysis for fixed sized frames and some traffic handling methods. We

used 100mbp/s single full duplex Ethernet switch for our simulation. Finally simulation

analysis and simulation results are discussed. Our purpose of simulation of Switched Ethernet

networks is of good importance for the real time industrial applications.

Embedded applications have become more and more complex, increasing the demands on the communication network. For reasons such as safety and usability, there are real-time constraints that must be met. Also, to offer high performance, network protocols should offer efficient user services aimed at specific types of communication. At the same time, it is desirable to design and implement embedded networks with reduced cost and development time, which means using available hardware for standard networks. To that end, there is a trend towards using switched Ethernet for embedded systems because of its hight bit rate and low cost. Unfortunately, since switched Ethernet is not specifically designed for embedded systems, it has several limitations such as poor support for QoS because of FCFS queuing policy and high protocol overhead. This thesis contributes towards fulfilling these requirements by developing (i) real-time analytical frameworks for providing QoS guarantees in packet-switched networks and (II) packet-merging techniques to reduce the protocol overhead. We have developed two real-time analytical frameworks for networks with FCFS queuing in the switches, one for FCFS queuing in the source nodes and one for EDF queuing in the source nodes. The correctness and tightness of the real-time analytical frameworks for different network components in a singel-switch neetwork are given by strict theoretical proofs, and the performance of our end-to-end analyses is evaluated by simulations. In conjunction with this, we have compared our results to Network Calculus (NC), a commonly used analytical scheme for FCFS queuing. Our comparison study shows that our anlysis is more accurate than NC for singel-switch networks. To reduce the protocol overhead, we have proposed two active switched Ethernet approaches, one for real-time many-to-many communication and the other for the real-time short message traffic that is often present in embedded applications. A significant improvement in performance achieved by using our proposed active networks is demonstrated. Although our approaches are exemplified using switched Ethernet, the general approaches are not limited to switched Ethernet networks but can easily be moified to other similar packet-switched networks.

Virtualisation is one of the underlying technologies that led to the success of cloud computing platforms (CCPs). The technology, along with other features such as multitenancy allows delivering of computing resources in the form of service through efficient sharing of physical resources. As these resources are provided through virtualisation, a robust agreement is outlined for both the quantity and quality-of-service (QoS) in a service level agreement (SLA) documents. QoS is one of the essential components of SLA, where performance is one of its primary aspects. As the technology is progressively maturing and receiving massive acceptance, researchers from industry and academia continue to carry out novel theoretical and practical studies of various essential aspects of CCPs with significant levels of success. This thesis starts with the assessment of the current level of knowledge in the literature of cloud computing in general and CCPs in particular. In this context, a substantive literature review was carried out focusing on performance modelling, testing, analysis and evaluation of Infrastructure as a Service (IaaS), methodologies. To this end, a systematic mapping study (SMSs) of the literature was conducted. SMS guided the choice and direction of this research. The SMS was followed by the development of a novel open queueing network model (QNM) at equilibrium for the performance modelling and analysis of an OpenStack IaaS CCP. Moreover, it was assumed that an external arrival pattern is Poisson while the queueing stations provided exponentially distributed service times. Based on Jackson’s theorem, the model was exactly decomposed into individual M/M/c (c ≥ 1) stations. Each of these queueing stations was analysed in isolation, and closed-form expressions for key performance metrics, such as mean response time, throughput, server (resource) utilisation as well as bottleneck device were determined. Moreover, the research was extended with a proposed open QNM with a bursty external arrival pattern represented by a Compound Poisson Process (CPP) with geometrically distributed batches, or equivalently, variable Generalised Exponential (GE) interarrival and service times. Each queueing station had c (c ≥ 1) GE-type servers. Based on a generic maximum entropy (ME) product form approximation, the proposed open GE-type QNM was decomposed into individual GE/GE/c queueing stations with GE-type interarrival and service times. The evaluation of the performance metrics and bottleneck analysis of the QNM were determined, which provided vital insights for the capacity planning of existing CCP architectures as well as the design and development of new ones. The results also revealed, due to a significant impact on the burstiness of interarrival and service time processes, resulted in worst-case performance bounds scenarios, as appropriate. Finally, an investigation was carried out into modelling and analysis of performance and security trade-offs for a CCP architecture, based on a proposed generalised stochastic Petri net (GSPN) model with security-detection control model (SDCM). In this context, ‘optimal’ combined performance and security metrics were defined with both M-type or GE-type arrival and service times and the impact of security incidents on performance was assessed. Typical numerical experiments on the GSPN model were conducted and implemented using the Möbius package, and an ‘optimal’ trade-offs were determined between performance and security, which are crucial in the SLA of the cloud computing services.
Petroleum technology development fund (PTDF) of the government of Nigeria Usmanu Danfodiyo University, Sokoto

Wireless Sensor Network (WSN) finds vast real-world applications in the field of energy control, security, health care, defense, and environment monitoring. WSNs are subdued by limited power with a specific battery backup. Due to the large distance between Sensor Nodes (SNs) and the sink, more power consumption occurs in the sensors. The limited energy of SNs is a major drawback to empower a large network coverage area. Therefore, the battery life and location of Cluster Heads (CHs) play an important role in increasing the efficiency and lifetime of SNs for long-term operation in WSNs. Researchers face significant challenges in developing more energy-efficient and secure clustering and routing protocols for WSNs. The bulk of existing routing protocols focuses on CH election while disregarding other important aspects of routing including cluster formation, data aggregation, and security, among others. Nature-inspired algorithms like Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Ant Colony Optimization (ACO), Gray Wolf Optimization (GWO), and Butterfly Optimization Algorithm (BOA) have been used for addressing important challenges in WSNs, such as sensor lifespan, transmission distance, and energy consumption. The introduction of hybrid techniques has proven to be more effective. Hybrid techniques like GA PSO, PSO-ACO, PSO-GWO, etc. have gained traction as viable solutions for bio inspired algorithms to improve the energy efficiency of WSNs. Such techniques have been found more optimum in comparison to the conventional techniques. The present thesis focuses on comparative analysis of hybridization techniques with conventional techniques for improving the energy efficiency of WSNs. In addition, an Improved Butterfly Optimization Algorithm (IBOA) has been proposed for global optimization problems in WSNs. Lastly, the present thesis focuses on addressing threats and security issues in WSNs through a feature selection and Machine Learning (ML) based intrusion detection pipeline. The Fast Correlation based Feature Selection (FCBFS) has been utilized as the feature selection method. The ML classifiers include Decision Tree (DT), Random Forest (RF), ix Naïve Bays (NB), Extra Tree (ET), and Extreme Gradient Boosting (XG-Boost). The contributions presented in this thesis are outlined below: • We propose a comprehensive review of Bio-inspired Hybrid Optimization Algorithms for Energy-Efficient WSN. We have aimed to discuss and compare various newly implemented, conventional, and hybrid methodologies for establishing a robust energy-efficient WSN wherein parameters like packet loss, energy, throughput, delay, and overhead have been utilized. Various open issues and challenges in WSN development using bio-inspired optimization techniques such as network stability, network dynamic character, secure transmission lines, methods to improve QoS, etc., have been addressed. • We propose a variable sensor modality IBOA for global optimization problems. The modified optimization approach focuses on unconstrained issues, performs on restricted problems, and remains the future scope of this work. • We propose an FCBFS method with XG-Boost for the National Security Laboratory-Knowledge Discovery Dataset (NSL-KDD) intrusion detection benchmark dataset to address the threats and security issues in a complicated WSN for IoT applications. Evaluation metrics such as accuracy, precision, recall, and F1-Score have been calculated to gauge the performance and robustness of the proposed research work. A classic accuracy score of 99.84% is achieved in the case of the XG-Boost classifier, wherein the best ten obtained features were selected after applying the proposed FCBFS. The proposed technique, which has ten features, outperforms the existing techniques in the literature for the NSL-KDD dataset. Experimental analysis has been done extensively to prove the efficacy of the developed solutions.

碩士
國立清華大學
資訊科學研究所
85
Multiple services with heterogeneous Quality Of Services (QoS) requirements are supported in ATM networks. The cell scheduling discipline is needed to utilize the network resources efficiently and guarantee the QoS requirements. FCFS is the simplest and easiest scheme for hardware implemeyntation. However, because of its lack of support of prioritizing scheme and inefficiency of buffer usage, it is not suitable to support QoS -guarantee servics .Therefore, a modified FCFS scheme with QoSguarantee is proposed in this paper. Inheriting the simplicity of FCFS, we modify the FIFO by adding adaptive queues for priority handing to satisfy the diverse QoS requirements. The buffer sizes of the adaptive queues could be decided by the traffic load and cell delay constraint to grarantee the cell loss rate. As a result, the proposed modified FIFO scheme is simple in hardware implementation, while it has the ability to handle multiple QoS priorities. The performance evaluation shows that the accessible offered load in our proposed scheme is better than the others proposed before.

碩士
中華大學
資訊工程學系碩士班
91
Bluetooth networks, based on the transmission technology of frequency-hopping spread spectrum, support both voice and data services. In Bluetooth MAC layer, a single Bluetooth device (Master) dynamically allocates time slots to all other individual Bluetooth devices (Slaves). The Master polls each Slave in a Round-Robin (RR) fashion. In this paper, we propose a new scheduling scheme. Master polls Slaves according to the state of the Master''s packet transmitting queue. When the queue is not empty, Master polls Slaves according to packet arrival order : a FCFS (or FIFO) scheme. When the queue is empty, RR scheme is used. We simulated and analyzed the performance of scheduling scheme in terms of channel utilization, packet delay and queue length. Existing schemes are simulated under the assumption symmetric and uniform traffic. We conducted simulations under various traffic conditions (uniform, non-uniform, symmetric, and asymmetric). The results show that our scheme has good performance under the symmetric and uniform traffic & the asymmetric (when master traffic is high) and uniform traffic. And it works stably in symmetric and non-uniform traffic. Though our scheme combines RR with FCFS, unexpectedly our scheme has lower packet delay than the others.

碩士
國立臺灣科技大學
電機工程系
89
DOCSIS (data over cable service interface specification) is developed for data transmission over the HFC (hybrid fiber coaxial) network. The latest version of the new specification, known as DOCSIS 1.1, defines the new functionality that allows cable operators to provide the guaranteed bandwidth, i.e., quality of service (QoS), to cable modem customers. It defines five upstream service flow scheduling services. Scheduling services are designed to improve the efficiency of the poll/grant process. By specifying a scheduling service and its associated QoS parameters, the cable modem termination system (CMTS) can anticipate the throughput and latency needs of the upstream traffic and provides polls and/or grants at the appropriate times. However, the QoS parameters may be violated if the same interval is assigned to several flows. In this paper, we introduce a new mini-slots assignment algorithm, which is called mini-slot-based FCFS (first come first serve) assignment algorithm, to reduce the QoS violation. We will simulate it by several different VoIP algorithms and analyze the performance. By 10% of the limitation of QoS violation boundary, G.723 and G.729 can accommodate the maximum VoIP data flows in the system. Meanwhile, we also find the fewer data rate of VoIP data flows will reduce the utilization of the system because there are too many data flows in the system simultaneously. Therefore, we should limit the upper boundary of the system when using advanced VoIP coders to increase the system utilization.

碩士
國立臺北科技大學
能源與冷凍空調工程系
107
In this research, Data mining is applied to the fault diagnosis of Centrifugal Chiller. Then verify the research method through ASHRAE RP-1043[1] Centrifugal Chiller operational data, and make effective data classification by data mining. When the R software is applied for data mining, to imporve classification efficieny of large data amount and multiple variables, Dimension Reduction is applied to data before data analysis. Therefore, the Fast Correlation Based Filter for Feature Selection（FCBF） is used in this research to retrieve optimal feature subset, and develop Fault Detection and Diagnosis（FDD） of Centrifugal Chiller by Gradient Boosting Decision Tree（GBDT） to undertake the Fault Detection and Diagnosis of seven common Centrifugal Chiller faults. The results show that the diagnostic rate using the Fast Correlation Based Filter for Feature Selection（FCBF） combined with the Gradient Boosting Decision Tree （GBDT) is 20.89% higher than the Linear Discriminant Analysis（LDA） combined with the Support Vector Machine（SVM）.

Professional Doctorate - Doctor of Business Administration (DBA)
This study analyses the relationship between knowledge sharing, family controlled businesses (FCBs), training for workers, incentive systems and trust in Hong Kong’s Clothing Industry (HKCI). The study contributes by investigating the impact of the ability, motivation and opportunity (AMO) paradigm focusing on training for workers(A), incentive systems(M) and trust(O) and the moderating effects of Family control businesses (FCBs) on knowledge sharing in Hong Kong’s clothing industry. Such an investigation is timely and relevant when a number of Chinese family businesses are facing the dilemma of succeeding their businesses through appropriate governance structures, operations and systems so as to continue their entrepreneurial spirit and effectively manage the generational transitions in Hong Kong (HK) (Au, K et al. 2013).These challenges result in failure of some family control businesses from managing succession and intergenerational leadership Issues (Chua et al., 2003; Long & Chrisman, 2014). Thus, sharing key knowledge by people in FCBs through appropriate people management practices is important for sustained succession in FCBs. The AMO paradigm has received considerable research attention in the field of Human Resource Management (HRM) in the last two decades. The AMO model offers a useful framework for studying how certain HRM practices can impact knowledge sharing performance outcomes. Based on a review of literature, a conceptual model showing the constructs of AMO was developed and six hypotheses were then generated and tested in this research. The findings of the research suggest that incentive systems and trust have a significant impact on knowledge sharing but training for workers does not have any significant impact on knowledge sharing. The findings also revealed that variables of training for workers, incentive systems, and trust have a significant and negative impact for FCBs. Overall, the findings from this study have implications for theory and practice. The results highlight the relationships among the AMO components and Knowledge sharing performance in a new context, especially by analysing the moderating impact of FCBs. In terms of managerial implications for practice, this research highlights that FCBs need to focus strategically on AMO components that contribute most in enhancing a firm’s knowledge sharing performance.

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.

The present dissertation tried to provide an answer to the need of high-quality evaluations of theoretically grounded antibullying interventions (Baldry & Farrington, 2007; Ttofi & Farrington, 2011). Literature of the last ten years shows that aggressive behaviours carried out by peers may be experienced in both face-to-face and online interactions (Tokunaga, 2010; Wingate, Minney, & Guadagno, 2013); for this reason adopting a specific focus both on bullying and cyberbullying appears to be more suitable (Menesini, 2012). The general aim of the present dissertation was to evaluate Noncadiamointrappola! program 3rd Edition by adopting an evidence-based approach in analyzing aspects related to the intervention’s efficacy. Three empirical studies are presented. They cover three main issues: 1) measurement of the cyberbullying constructs; 2) efficacy of the Noncadiamointrappola! program in reducing bullying, cyberbullying, and internalizing symptoms; 3) mediational mechanisms involved in the explanation of the efficacy of the program in reducing cybervictimization. In the first study we analyzed the psychometric properties of a revised instrument (FCBVSs; Menesini, Nocentini, & Calussi, 2011) devoted to measure cybervictimization and cyberbullying constructs. The analyses were conducted on a sample of 1142 adolescents (54.5% males) enrolled in 9th, 10th 11th grades of high schools in Tuscany. Results support a gender-invariant model based on 14 items and four factors both for cybervictimization and cyberbullying. The subscales cover four types of behaviours and describe different attacks made by peers in the cyber context (written-verbal, visual, impersonation and exclusion). The second order CFA confirmed that a “global”, second-order measure of cyberbullying and cybervictimization fits well with data. Overall the scales showed both good validity (construct, concurrent and convergent) and reliability (internal consistency and test-retest). In the second study we evaluated the effects of the Noncadiamointrappola! program in two quasi-experimental trials that involved different samples of adolescents attending the first year of Italian high schools. We found that the program in the experimental group significantly predicted a decrease in all targeted variables (victimization, bullying, cybervictimization, and 4 cyberbullying) in both quasi experimental trials. Looking at the first quasi experimental trial results (Control group, N=171; Experimental group, N=451), we found significant long-term effects of the program (six months); the outcomes did not decay over time. At the same time, we found that the program was efficacious in reducing internalizing symptoms in the experimental group through the decrease in cybervictimization above and beyond the mediational effect of the decrease in victimization. In the second independent trial (Control group, N=227; Experimental group, N=234) we tested for potential moderating effects of gender; we found that it did not have interactive effects with the efficacy of the program. In the third study, using data about the first quasi experimental trial, we analyzed the mediational mechanisms that explain the efficacy of the program in reducing cybervictimization. We found that the program predicted the increase over time in seeking support coping strategy, both on informational and instrumental aspects (distal advice) and on the more emotional way of getting help from people (close support). Noncadiamointrappola! program had significant indirect effects, through distal advice and close support, in reducing cybervictimization. Results are discussed highlighting their contributions to the literature both on evidence-based interventions and on bullying and cyberbullying phenomena. Finally, the overall strengths, limitations and implication for future studies are pointed out.

Firm real time system with Poisson arrival process, iid exponential service times and iid deadlines till the end of service of a job, operated under the First Come First Served (FCFS) scheduling policy is well studied. In this thesis, we present an exact theoretical analysis of a similar (M/M/1 + G queue) system with exact admission control (EAC). We provide an explicit expression for the steady state workload distribution. We use this solution to derive explicit expressions for the loss ratio and the sojourn time distribution. An exact theoretical analysis of the performance of an M/M/1 + G queue with preemptive deadlines till the end of service, operating under the Earliest Deadline First (EDF) scheduling policy, appears to be difficult, and only approximate formulas for the loss ratio are available in the literature. We present in this thesis similar approximate formulas for the loss ratio in the present of an exit control mechanism, which discards a job at the epoch of its getting the server if there is no chance of completing it. We refer to this exit control mechanism as the Early job Discarding Technique (EDT). Monte Carlo simulations of performance indicate that the maximum approximation error is reasonably small for a wide range of arrival rates and mean deadlines. Finally, we compare the loss ratios of the First Come First Served and the Earliest Deadline First scheduling policies with or without admission or exit control mechanism, as well as their counterparts with deterministic deadlines. The results include some formal equalities, inequalities and some counter-examples to establish non-existence of an order. A few relations involving loss ratios are posed as conjectures, and simulation results in support of these are reported. These results lead to a complete picture of dominance and non-dominance relations between pairs of scheduling policies, in terms of loss ratios.

Firm real time system with Poisson arrival process, iid exponential service times and iid deadlines till the end of service of a job, operated under the First Come First Served (FCFS) scheduling policy is well studied. In this thesis, we present an exact theoretical analysis of a similar (M/M/1 + G queue) system with exact admission control (EAC). We provide an explicit expression for the steady state workload distribution. We use this solution to derive explicit expressions for the loss ratio and the sojourn time distribution. An exact theoretical analysis of the performance of an M/M/1 + G queue with preemptive deadlines till the end of service, operating under the Earliest Deadline First (EDF) scheduling policy, appears to be difficult, and only approximate formulas for the loss ratio are available in the literature. We present in this thesis similar approximate formulas for the loss ratio in the present of an exit control mechanism, which discards a job at the epoch of its getting the server if there is no chance of completing it. We refer to this exit control mechanism as the Early job Discarding Technique (EDT). Monte Carlo simulations of performance indicate that the maximum approximation error is reasonably small for a wide range of arrival rates and mean deadlines. Finally, we compare the loss ratios of the First Come First Served and the Earliest Deadline First scheduling policies with or without admission or exit control mechanism, as well as their counterparts with deterministic deadlines. The results include some formal equalities, inequalities and some counter-examples to establish non-existence of an order. A few relations involving loss ratios are posed as conjectures, and simulation results in support of these are reported. These results lead to a complete picture of dominance and non-dominance relations between pairs of scheduling policies, in terms of loss ratios.