The War Between Mice and Elephants

Recent measurement based studies reveal that most of the Internet connections are short in terms of the amount of traffic they carry (mice), while a small fraction of the connections are carrying a large portion of the traffic (elephants). A careful study of the TCP protocol shows that without help from an Active Queue Management (AQM) policy, short connections tend to lose to long connections in their competition for bandwidth. This is because short connections do not gain detailed knowledge of the network state, and therefore they are doomed to be less competitive due to the conservative nature of the TCP congestion control algorithm. Inspired by the Differentiated Services (Diffserv) architecture, we propose to give preferential treatment to short connections inside the bottleneck queue, so that short connections experience less packet drop rate than long connections. This is done by employing the RIO (RED with In and Out) queue management policy which uses different drop functions for different classes of traffic. Our simulation results show that: (1) in a highly loaded network, preferential treatment is necessary to provide short TCP connections with better response time and fairness without hurting the performance of long TCP connections; (2) the proposed scheme still delivers packets in FIFO manner at each link, thus it maintains statistical multiplexing gain and does not misorder packets; (3) choosing a smaller default initial timeout value for TCP can help enhance the performance of short TCP flows, however not as effectively as our scheme and at the risk of congestion collapse; (4) in the worst case, our proposal works as well as a regular RED scheme, in terms of response time and goodput.

Rôle de la cyclo-oxygénase-2 constitutive dans la synthèse des prostaglandines et caractérisation de ses relations avec les prostaglandines synthases terminales

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

On Queues with Interruptions and Repeat or Resumption of Service

This thesis entitled' On Queues with Interruptions and Repeat or Resumption of Service' introduces several new concepts into queues with service interruption. It is divided into Seven chapters including an introductory chapter. The following are keywords that we use in this thesis: Phase type (PH) distribution, Markovian Arrival Process (MAP), Geometric Distribution, Service Interruption, First in First out (FIFO), threshold random variable and Super threshold random variable. In the second chapter we introduce a new concept called the 'threshold random variable' which competes with interruption time to decide whether to repeat or resume the interrupted service after removal of interruptions. This notion generalizes the work reported so far in queues with service interruptions. In chapter 3 we introduce the concept of what is called 'Super threshold clock' (a random variable) which keeps track of the total interruption time of a customer during his service except when it is realized before completion of interruption in some cases to be discussed in this thesis and in other cases it exactly measures the duration of all interruptions put together. The Super threshold clock is OIl whenever the service is interrupted and is deactivated when service is rendered. Throughout this thesis the first in first out service discipline is followed except for priority queues.

QoS Evaluation of BandwidthSchedulers in IPTV Networks OfferedSRD Fluid Video Traffic

Internet protocol TV (IPTV) is predicted to be the key technology winner in the future. Efforts to accelerate the deployment of IPTV centralized model which is combined of VHO, encoders, controller, access network and Home network. Regardless of whether the network is delivering live TV, VOD, or Time-shift TV, all content and network traffic resulting from subscriber requests must traverse the entire network from the super-headend all the way to each subscriber's Set-Top Box (STB).IPTV services require very stringent QoS guarantees When IPTV traffic shares the network resources with other traffic like data and voice, how to ensure their QoS and efficiently utilize the network resources is a key and challenging issue. For QoS measured in the network-centric terms of delay jitter, packet losses and bounds on delay. The main focus of this thesis is on the optimized bandwidth allocation and smooth datatransmission. The proposed traffic model for smooth delivering video service IPTV network with its QoS performance evaluation. According to Maglaris et al [5] First, analyze the coding bit rate of a single video source. Various statistical quantities are derived from bit rate data collected with a conditional replenishment inter frame coding scheme. Two correlated Markov process models (one in discrete time and one incontinuous time) are shown to fit the experimental data and are used to model the input rates of several independent sources into a statistical multiplexer. Preventive control mechanism which is to be include CAC, traffic policing used for traffic control.QoS has been evaluated of common bandwidth scheduler( FIFO) by use fluid models with Markovian queuing method and analysis the result by using simulator andanalytically, Which is measured the performance of the packet loss, overflow and mean waiting time among the network users.

QoS evaluation of bandwidth schedulersin IPTV networks offered SRD fluidvideo traffic: a simulation study

IPTV is now offered by several operators in Europe, US and Asia using broadcast video over private IP networks that are isolated from Internet. IPTV services rely ontransmission of live (real-time) video and/or stored video. Video on Demand (VoD)and Time-shifted TV are implemented by IP unicast and Broadcast TV (BTV) and Near video on demand are implemented by IP multicast. IPTV services require QoS guarantees and can tolerate no more than 10-6 packet loss probability, 200 ms delay, and 50 ms jitter. Low delay is essential for satisfactory trick mode performance(pause, resume,fast forward) for VoD, and fast channel change time for BTV. Internet Traffic Engineering (TE) is defined in RFC 3272 and involves both capacity management and traffic management. Capacity management includes capacityplanning, routing control, and resource management. Traffic management includes (1)nodal traffic control functions such as traffic conditioning, queue management, scheduling, and (2) other functions that regulate traffic flow through the network orthat arbitrate access to network resources. An IPTV network architecture includes multiple networks (core network, metronetwork, access network and home network) that connects devices (super head-end, video hub office, video serving office, home gateway, set-top box). Each IP router in the core and metro networks implements some queueing and packet scheduling mechanism at the output link controller. Popular schedulers in IP networks include Priority Queueing (PQ), Class-Based Weighted Fair Queueing (CBWFQ), and Low Latency Queueing (LLQ) which combines PQ and CBWFQ.The thesis analyzes several Packet Scheduling algorithms that can optimize the tradeoff between system capacity and end user performance for the traffic classes. Before in the simulator FIFO,PQ,GPS queueing methods were implemented inside. This thesis aims to implement the LLQ scheduler inside the simulator and to evaluate the performance of these packet schedulers. The simulator is provided by ErnstNordström and Simulator was built in Visual C++ 2008 environmentand tested and analyzed in MatLab 7.0 under windows VISTA.

QoS evaluation of Bandwidth Schedulers in IPTV Networks Offered SRD Fluid Video Traffic

Internet protocol TV (IPTV) is predicted to be the key technology winner in the future. Efforts to accelerate the deployment of IPTV centralized model which is combined of VHO, encoders, controller, access network and Home network. Regardless of whether the network is delivering live TV, VOD, or Time-shift TV, all content and network traffic resulting from subscriber requests must traverse the entire network from the super-headend all the way to each subscriber's Set-Top Box (STB). IPTV services require very stringent QoS guarantees When IPTV traffic shares the network resources with other traffic like data and voice, how to ensure their QoS and efficiently utilize the network resources is a key and challenging issue. For QoS measured in the network-centric terms of delay jitter, packet losses and bounds on delay. The main focus of this thesis is on the optimized bandwidth allocation and smooth data transmission. The proposed traffic model for smooth delivering video service IPTV network with its QoS performance evaluation. According to Maglaris et al [5] first, analyze the coding bit rate of a single video source. Various statistical quantities are derived from bit rate data collected with a conditional replenishment inter frame coding scheme. Two correlated Markov process models (one in discrete time and one in continuous time) are shown to fit the experimental data and are used to model the input rates of several independent sources into a statistical multiplexer. Preventive control mechanism which is to be including CAC, traffic policing used for traffic control. QoS has been evaluated of common bandwidth scheduler( FIFO) by use fluid models with Markovian queuing method and analysis the result by using simulator and analytically, Which is measured the performance of the packet loss, overflow and mean waiting time among the network users.

Defence against code injection attacks

Code injection attacks are considered serious threats to the Internet users. In this type of attack the attacker injects malicious codes in the user programs to change or divert the execution flows. In this paper we explore the contemporary defence strategies against code injection attacks (CIAs) and underline their limitations. To overcome these limitations, we suggest a number of countermeasure mechanisms for protecting from CIAs. Our key idea relies on the multiplexing technique to preserve the exact return code to ensure the integrity of program execution trace of shell code. This technique also maintains a FIFO (first in first out) queue to defeat the conflict state when multiple caller method makes a call simultaneously. Finally, our technique can provide better performance, in terms of protection and speed, in some point compared to the CFI (control flow integrity) as well as CPM (code pointer masking) techniques.

Valorização dos estoques

A ferramenta de custos é importante do ponto de vista gerencial, auxiliando no controle de gastos e na tomada de decisões. Para demonstrar a classificação dos custos é dado o exemplo dos custos mensais de uma indústria, dividindo-os em custos fixos e custos variáveis. É apresentada também a relação dos custos diretos e indiretos com os custos fixos e variáveis. Como o estoque representa grande parte dos custos, são apresentadas três formas contábeis para valorização de estoques: PEPS (FIFO em inglês) primeiro a entrar, primeiro a sair; UEPS (LIFO em inglês) último a entrar, primeiro a sair e Custo Médio. Conta com exemplo de valorização de estoque usando as três técnicas.

Escalonamento de processos

Apresenta os principais conceitos de escalonamento de processos. Trata-se sobre filas de processos, a ordem como os recursos são alocados de acordo com a necessidade e/ou prioridade já estabelecida pelos processos, como essas prioridades são tratados para que tenham o máximo de utilização dos recursos como processador, memória, tempo de execução de cada processo já escalonado. Também são tratadas as políticas de escalonamento, os algoritmos que envolvem essas tarefas por parte do processador como algoritmos preemptivos, não preemptivos, escalonamentos de tempo real. O escalonamento de threads em Java também será abordado de forma resumidamente. Tais conteúdos são indicados aos alunos de graduação da área de Engenharia de Computação, Sistemas de Informação e correlatos.

Políticas de escalonamento de processos e threads

O material apresenta políticas de escalonamento de processos e threads. O escalonamento de processos (ou Escalonamento do processador) trata da decisão sobre qual processo será executado em um determinado instante e por qual processador. O material apresenta também algoritmos de escalonamento relevantes, incluindo exemplos de algoritmos preemptivos e não-preemptivos, objetivos e critérios do escalonamento e diferentes tipos de escalonamentos: Escalonamento FIFO (first-in first-out), Escalonamento circular RR (Round-Robin ), Escalonamento SPF (Shortest Process First), Escalonamento SRT (Shortest Remaining Time), Escalonamento FSS (Fair Share Scheduling), Escalonamento de tempo real, Escalonamento de threads Java – JVM, Escalonamento no Windows XP e UNIX.

Escalonamento de Processos

A videoaula apresenta o escalonamento de processos, com foco para as políticas de escalonamento do processador. Destaca o escalonamento com prioridades (estática ou dinâmica), o funcionamento do escalonamento de threads em Java, os níveis de escalonamento (alto nível, nível intermediário, baixo nível) e os critérios que são levados em conta pelo algoritmo de escalonamento. Apresenta também os objetivos e critérios do escalonamento e seus seguintes tipos: Escalonamento FIFO (first-in first-out), Escalonamento circular RR (Round-Robin ), Escalonamento SPF (Shortest Process First), Escalonamento SRT (Shortest Remaining Time), Escalonamento FSS (Fair Share Scheduling) - Escalonamento por fração justa, Escalonamento de tempo real, Escalonamento de threads Java – JVM, Escalonamento no Windows XP e UNIX.

Dentistry for babies: Caries experience vs. Assiduity in clinical care

Aim: This study analyzed and compared the experience of dental caries in 300 children aged 0 to 48 months, who were participants and non-participants of a preventive program 'Dentistry for babies', as well as the correlation between assiduity of dental visits and experience of dental caries. Methods: The subjects were randomly selected and divided into two groups: G1 'Non participant children of the Program' (n=100) and G2 'Participant Children of the Program' (n=200). Each group was subdivided in two subgroups: 0-24 months and 25-48 months. The collected data from G2 were analyzed, relating the variation of the dmft index (dmft refers to primary teeth: d = decayed, m = missing/extracted due to caries, f = filled, t = teeth) (C) and dental caries prevalence (P) with the influence of assiduity factor in each subgroup. To collect data, clinical examinations were performed using tactile and visual criteria by a single calibrated examiner. The data were statistically analyzed using the 'paired t-test', 'Mann-Whitney' and 'Chi-Squared' tests (p<0.05). Results: It was found that prevalence and dmft index were statistically significant (P=0.0001) with the greatest values observed in G1 (p=0.0001). The values were: PG1 (73%), PG2 (22%), CG1 (3.45±3.84), CG2 (0.66±1.57). Assiduity was significant in G2 (p=0.0001). The values observed were: P-Assiduous (2%), P-Non-assiduous (42%), C-Assiduous (0.04±0.31), and C-Non-assiduous (1.29±2.01). Conclusions: The participation in the program had a positive influence on the oral health of babies. Complete assiduity to the program resulted in the lowest rates and prevalence of dental caries.

QoS management in smart grids: a Markovian approach

In Smart Grids, a variety of new applications are available to users of the electrical system (from consumers to the electric system operators and market operators). Some applications such as the SCADA systems, which control generators or substations, have consequences, for example, with a communication delay. The result of a failure to deliver a control message due to noncompliance of the time constraint can be catastrophic. On the other hand, applications such as smart metering of consumption have fewer restrictions. Since each type of application has different quality of service requirements (importance, delay, and amount of data to transmit) to transmit its messages, the policy to control and share the resources of the data communication network must consider them. In this paper Markov Decision Process Theory is employed to determine optimal policies to explore as much as possible the availability of throughput in order to transmit all kinds of messages, considering the quality of service requirements defined to each kind of message. First a non-preemptive model is formulated and after that a preemptive model is derived. Numerical results are used to compare FIFO, non-preemptive and preemptive policies.

Investigação química e biológica dos metabólitos secundários derivados de macroalgas marinhas e microrganismos associados

Pós-graduação em Química - IQ

Dental caries in children participating in a dentistry for infants program

To assess the impact of the "Dentistry for Infants" early dental care program run by Jacareí County (SP) by comparing the caries of individuals participating and not participating in this program. Methods: In total, 300 children between 0 and 48 months old were assessed in the following two groups: infants not participating in the program (G1, n = 100) and infants participating in the program (G2, n = 200). Each group was further divided according to age in subgroups of 0 to 24 months and 25 to 48 months. All children were clinically assessed for carious lesions using the visual-tactile method. The data were statistically analyzed using a paired Student's t-test, Mann-Whitney test, and c 2 test at a 5% significance level. Results: There was a significant difference in the prevalence (P) and mean index of deciduous teeth (deft) (C) that were decayed, indicated for extraction and filled, and the highest values were observed in G1 (p < 0.0001). The values were as follows: PG1, 73%; PG2, 22%; CG1, 3.45 ± 3.84; and CG2, 0.66 ± 1.57. Conclusion: Participating in the program positively impacted the infants' oral health.