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Software bugs can cost millions and affect people's daily lives. However, many bug detection tools are not always practical in reality, which hinders their wide adoption. There are three main concerns regarding existing bug detectors: 1) run-time overhead in dynamic bug detectors, 2) space overhead in dynamic bug detectors, and 3) scalability and precision issues in static bug detectors. With those in mind, we propose to: 1) leverage commodity hardware to reduce run-time overhead, 2) reuse metadata maintained by one bug detector to detect other types of bugs, reducing space overhead, and 3) apply programming idioms to static analyses, improving scalability and precision. We demonstrate the effectiveness of three approaches using data race bugs, memory safety bugs, and permission check bugs, respectively. First, we leverage the commodity hardware transactional memory (HTM) selectively to use the dynamic data race detector only if necessary, thereby reducing the overhead from 11.68x to 4.65x. We then present a production-ready data race detector, which only incurs a 2.6% run-time overhead, by using performance monitoring units (PMUs) for online memory access sampling and offline unsampled memory access reconstruction. Second, for memory safety bugs, which are more common than data races, we provide practical temporal memory safety on top of the spatial memory safety of the Intel MPX in a memory-efficient manner without additional hardware support. We achieve this by reusing the existing metadata and checks already available in the Intel MPX-instrumented applications, thereby offering full memory safety at only 36% memory overhead. Finally, we design a scalable and precise function pointer analysis tool leveraging indirect call usage patterns in the Linux kernel. We applied the tool to the detection of permission check bugs; the detector found 14 previously unknown bugs within a limited time budget. / Doctor of Philosophy / Software bugs have caused many real-world problems, e.g., the 2003 Northeast blackout and the Facebook stock price mismatch. Finding bugs is critical to solving those problems. Unfortunately, many existing bug detectors suffer from high run-time and space overheads as well as scalability and precision issues. In this dissertation, we address the limitations of bug detectors by leveraging commodity hardware and common programming patterns. Particularly, we focus on improving the run-time overhead of dynamic data race detectors, the space overhead of a memory safety bug detector, and the scalability and precision of the Linux kernel permission check bug detector. We first present a data race detector built upon commodity hardware transactional memory that can achieve 7x overhead reduction compared to the state-of-the-art solution (Google's TSAN). We then present a very lightweight sampling-based data race detector which re-purposes performance monitoring hardware features for lightweight sampling and uses a novel offline analysis for better race detection capability. Our result highlights very low overhead (2.6%) with 27.5% detection probability with a sampling period of 10,000. Next, we present a space-efficient temporal memory safety bug detector for a hardware spatial memory safety bug detector, without additional hardware support. According to experimental results, our full memory safety solution incurs only a 36% memory overhead with a 60% run-time overhead. Finally, we present a permission check bug detector for the Linux kernel. This bug detector leverages indirect call usage patterns in the Linux kernel for scalable and precise analysis. As a result, within a limited time budget (scalable), the detector discovered 14 previously unknown bugs (precise).

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Window decoding schedules are very attractive for message passing decoding of spatially coupled LDPC codes. They take advantage of the inherent convolutional code structure and allow continuous transmission with low decoding latency and complexity. In this paper we show that the decoding complexity can be further reduced if suitable message passing schedules are applied within the decoding window. An improvement based schedule is presented that easily adapts to different ensemble structures, window sizes, and channel parameters. Its combination with a serial (on-demand) schedule is also considered. Results from a computer search based schedule are shown for comparison.

現今資訊科技發展突飛猛進、通訊工具與網際網路日益普及，深深影響了人類的經濟活動，從傳統商務活動中，延展了物流、金流、資訊流的範圍，電子化提升了處理速度，改變使用模式，進而改變企業經營模式、人類思考模式與生活習慣。加上金融自由化、金融全球化等衝擊，除金融產業有擴大規模、擴大範疇之變革，金融服務亦為了因應客戶需求，趨向多元化與個人化。時至今日，商務活動中以金流的進展為最待加強，其中支付工具之電子化尤為重要。本論文研究電子票據之整體發展方向，探討電子票據能否成為安全、便利、有效、低成本之電子支付工具。 票據為支付工具之一種，其使用已久亦廣，為了能將其改進並予以電子化應用，乃有「電子票據」之電子支付工具產生。本研究旨在以票據之使用及電子票據之規劃設計機制，以我國之經濟、社會、技術、制度面等不同層面需求考量，參考歐美國家文獻與實務資料，從電子支付之角度，安全性、規模度、可靠度、低交易成本、用戶基礎等關鍵因素分析，針對電子票據發展趨勢探討，分析現行紙本票據與電子票據之優缺點，並進行電子票據與其他支付工具之比較，且比較國內外電子票據之差異性，期能對現行電子票據流程及架構提供改善及建議。此外，本研究亦研擬電子票據實施之程序及所需相關資源的配合，期能提供主管機關管理電子票據業務等之參考，進而更提昇電子支付之效率。 / Nowadays the rapid development and population of the information technology, the media, and the Internet has deeply affected all the economical movements of the human beings. The traditional commercial activities have expanded in the areas of distribution, finance, and information, because the entire entrepreneurial management strategies along with the ways that people think and live have all changed with the electronicalization that accelerates and modifies the process and usage. In addition, the financial deregulation and globalization forces the finance industry to expand in size and areas. Moreover, the financial services have become more and more various and personalized to respond the demands of their customers. Up to the present day, the development in finance area has been the one that needs to be strengthened most, especially the electronicalization of the payment tools. This essay is to study the entire development focus of the electronic note, and to find out whether the electronic note could be a safe, convenient, effective, and low-cost e-payment tool. Note is one of the payment tools and has been widely used for a long time. The so-called “electronic note” is produced in order to improve and electronicalize the traditional note. This study refers to the national documentation and practical data of the European and American countries and the different demands of Taiwan’s economics, society, technology, and regulations. It analyzes the electronic note’s design and usage in terms of safety, standard, credibility, low-cost, and user’s backgrounds. Furthermore, it discusses the development trend of the electronic note and demonstrates the pros and cons of the paper-note and electronic note. By the comparison between the electronic note and other payment tools and exploring the differences of the electronic note’s usage in Taiwan and in other countries, it is expected to come out some advice for improving the current electronic note infrastructure and the required resources. It maybe provides helpful suggestions for many financial organizations and increases the effectiveness of the e-payment systems.

Concerning the importance and the necessity of fitting food services to actual lawmaking and knowing the difficulty found in it, the present paper aimed to systemize a Tool (Evaluation List, Plan of Action and Touching Collaborators) to support Good Practices. The present study was realized in twenty three, 23, downtown food services, in Santa Maria, Rio Grande do Sul, through a proportional stratified sample of eight restaurants, eleven snack bars and four bakeries. A List of Evaluation of Good Practices for Food Services (LEGPFS) was made, specific for RDC 21604 ANVISA. This list was applied for a professional technician and for the company, in March and October, respectively. After that, a simple Plan of Action to facilitate the process of fitting was suggested. Samples of swabs to verify Staphylococcus coagulase positive and total count of mesophyll aerobics microorganisms and were collected from manipulators and from surfaces after hygiene, before and after the use of the tool. All collaborators were invited to participate of a touching concerning microbiological analysis and formulary applied to participants, evaluated by the results of LEGPFS. The results showed a significant difference (p<0,05) after the application of LEGPFS such for the technician as to the company, according to the fitting percentage. It was observed a significant improve (p<0,05) in following lawmaking after the use of the tool. The touching was considered efficient and there was a fitting to the process of hands and surfaces hygiene. In conclusion, the tool elaborated was valid to support food services in fitting actual lawmaking. / Tendo em vista a importância e a necessidade de adequação dos serviços de alimentação à legislação vigente e sabendo-se da dificuldade encontrada, objetivou-se, com este trabalho, sistematizar uma Ferramenta (Lista de Avaliação, Plano de Ação e Sensibilização de colaboradores) de apoio às Boas Práticas. O presente estudo foi realizado em 23 serviços de alimentação do Bairro Centro, da cidade de Santa Maria-RS, a partir de uma amostra estratificada proporcional de 8 restaurantes, 11 lanchonetes e 4 padarias/ confeitarias. Elaborou-se uma Lista de Avaliação de Boas Práticas para Serviços de Alimentação (LABPSA), específica para RDC 216/04 - ANVISA. Ela foi aplicada por profissional técnico e pela empresa, em março e outubro de 2006, respectivamente. Após a aplicação da LABPSA, sugeriu-se um modelo simples de Plano de Ação para facilitar o processo de adequação. Realizaram-se coletas de swabs nas mãos dos manipuladores e nas superfícies, após a higienização, para verificação de Staphylococcus coagulase positiva e contagem total de microrganismos aeróbios mesófilos, antes e após o uso da Ferramenta. Todos os colaboradores foram convidados a participar de uma sensibilização, avaliada pelos resultados da LABPSA, das análises microbiológicas e de formulário aplicado aos participantes. Constatou-se diferença significativa (p< 0,05) após a aplicação da LABPSA tanto técnica quanto pela empresa, de acordo com o percentual de adequação. Houve também uma melhora significativa (p< 0,05) no atendimento à legislação após a utilização da ferramenta. A sensibilização foi considerada eficaz e houve adequação no processo de higienização das mãos e superfícies. Em suma, a ferramenta elaborada foi válida para apoiar os serviços de alimentação nas adequações exigidas pela legislação atual.

One of the objectives of the master´s thesis is to summarize types of most used check valves and their constructions. These check valves have specific static and dynamic properties. One of dynamic properties is vibration of closing member of lift check valve. Due to these vibrations, the added effects of fluid may result. This thesis deals with explanation and computation of these added effects.