1,695 research outputs found
Numerical computation for parallel plate thermoacoustic heat exchangers in standing wave oscillatory flow
No full textA simplified computational method for studying the heat transfer characteristics of parallel plate thermoacoustic heat exchangers is presented. The model integrates the thermoacoustic equations of the standard linear theory into an energy balance-based numerical calculus scheme. Details of the time-averaged temperature and heat flux density distributions within a representative domain of the heat exchangers
and adjoining stack are given. The effect of operation conditions and geometrical parameters on the heat exchanger performance is investigated and main conclusions relevant for HX design are drawn as far as fin length, fin spacing, blockage ratio, gas and secondary fluid-side heat transfer coefficients are concerned. Most relevant is that
the fin length and spacing affect in conjunction the heat exchanger behaviour and have to be simultaneously optimized to minimize thermal losses localized at the HX-stack
junctions. Model predictions fit experimental data found in literature within 36% and 49% respectively at moderate and high acoustic Reynolds numbers
A portable stack-yard fence
No full textTitle from PDF caption (viewed on November 30, 2017).This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Mode of access: Internet from the Oregon Government Publications Collection.Text in English
Electrochemical transport in CuCl/HCl(aq) electrolyzer cells and stack of the Cu–Cl cycle
No full textThis paper develops a comprehensive predictive model for the CuCl/HCl(aq) electrolyzer stack in the electrochemical unit of the Cu–Cl cycle of hydrogen production. A strong aqueous anolyte is fed into the stack and forms complex speciation. The unit single cell is modeled to predict the decomposition voltage by applying the Gibbs energy minimization method (GEM). The kinetic correlations are incorporated to take into account the overpotential losses during the hydrogen generation process under a non-equilibrium condition with the stack under potential. To evaluate the single-cell contribution to the average performance of stack, a hydrodynamic analysis reveals the anolyte and catholyte flow distribution using a finite element method for solutions of the equation of mass and momentum conservation equations of the flow field. Using the simulated stack, the voltage spread across the individual cells in the stack, cell and stack voltage efficiency, and the sensitivity of stack performance under the operating conditions, are investigated. It is shown that the speciation model has good agreement with data in past literature. With an increase in the stack operating temperature from 25 °C to 65 °C, the average stack efficiency improves from 68% to 72%. Cells close to the anolyte or catholyte input ports possess a higher voltage efficiency than other cells. This is mainly due to less electrolyte received by the cells placed in the middle of the stack for the X-shape bipolar modules, resulting in less decomposition potential
Mining software testing knowledge from stack overflow
No full textThis paper aims to unveil and gather testing-related information from Stack Overflow, highlighting it as a valuable resource for practitioners seeking answers and guidance. The study aims to accumulate knowledge from real-life experiences shared on Stack Overflow and bridge the knowledge gap between industry practices and teaching practices.The paper explores different types of software testing, popular frameworks, temporal trends of testing-related technologies, controversial opinions, and recommended practices/advice/suggestions from Stack Overflow posts. The methodology involves determining search terms through literature, querying the Stack Exchange API, conducting frequency analysis of words from posts, and manually inspecting threads. Our results show that the most popular frameworks discussed are Selenium, Spring, JMeter, and React. Automated testing and JavaScript frameworks have shown an upward trajectory over the years. The recommendations made by practitioners were categorized based on the broad scope of topics covered. We draw comparisons and parallels with related previous research and discuss the technical limitations faced during the study.Overall, this paper uncovers valuable insights from Stack Overflow and provides practitioners with the current view on industry practices.CSE3000 Research ProjectComputer Science and Engineerin
RoCE based 100GbE RDMA network stack on FPGA hardware
No full textBig data analytics is one of the foundations for booming technologies such as machine learning, genetics/genomics, and computer vision. These big data applications require a large amount of data transfers for distributed and parallel processing. Networking is thus a crucial facilitator and could make big impact on big data processing.In a computing system with a common network stack such as the TCP/IP protocol suite, many expensive memory operations are necessary to process networking traffic. This means a large percentage of CPU resources are occupied by networking rather than data processing. The memory copying overhead introduced by networking not only reduces the throughput but also increases the latency. In this case, networking is becoming a major bottleneck for big data applications. This problem can be solved by applying Remote Direct Memory Access (RDMA) technology to the network stack. RDMA enables a zero-copy mechanism and has CPU bypass ability. With RDMA implemented, both the throughput and latency can be improved.In this work, we developed an open source 100 Gbps RDMA network stack on Field Programmable Gate Array (FPGA) hardware. The developed stack follows the RDMA over Converged Ethernet (RoCE) architecture and targets the Alveo FPGA platform. The stack includes a User kernel that can be customized for user applications. This means that computing applications can also be offloaded to this RoCE stack. Finally, we evaluate the stack and compare it with existing TCP/IP and RDMA stacks like the EasyNet and StRoM. The results show that the developed RDMA stack achieves a throughput of 100 Gbps and an RDMA READ operation latency around 4 us and an RDMA WRITE latency around 3.5 us for 64B data. It shows a great throughput advantage over the TCP/IP stack for message sizes smaller than 1 MB. The latency is also slightly lower than the TCP/IP stack.Big data analytics is one of the foundations for booming technologies such as machine learning, genetics/genomics, and computer vision. These big data applications require a large amount of data transfers for distributed and parallel processing. Networking is thus a crucial facilitator and could make big impact on big data processing.In a computing system with a common network stack such as the TCP/IP protocol suite, many expensive memory operations are necessary to process networking traffic. This means a large percentage of CPU resources are occupied by networking rather than data processing. The memory copying overhead introduced by networking not only reduces the throughput but also increases the latency. In this case, networking is becoming a major bottleneck for big data applications. This problem can be solved by applying Remote Direct Memory Access (RDMA) technology to the network stack. RDMA enables a zero-copy mechanism and has CPU bypass ability. With RDMA implemented, both the throughput and latency can be improved.In this work, we developed an open source 100 Gbps RDMA network stack on Field Programmable Gate Array (FPGA) hardware. The developed stack follows the RDMA over Converged Ethernet (RoCE) architecture and targets the Alveo FPGA platform. The stack includes a User kernel that can be customized for user applications. This means that computing applications can also be offloaded to this RoCE stack. Finally, we evaluate the stack and compare it with existing TCP/IP and RDMA stacks like the EasyNet and StRoM. The results show that the developed RDMA stack achieves a throughput of 100 Gbps and an RDMA READ operation latency around 4 us and an RDMA WRITE latency around 3.5 us for 64B data. It shows a great throughput advantage over the TCP/IP stack for message sizes smaller than 1 MB. The latency is also slightly lower than the TCP/IP stack.Electrical Engineerin
Comparison of post-stack and pre-stack seismic inversion methods
No full textIn this paper I review some seismic inversion methods. This methods of seismic inversion can be divide in two group: post-stack inversion and pre-stack inversion. The most recent approach of seismic inversion use pre-stack data. The earliest methods of seismic inversion use post-stack data. The author present comparison of two methods: resursive inversion and simultaneous inversion.W prezentowanej pracy opisano metody inwersji sejsmicznej, realizowanej przed i po procedurze składania. Przedstawiono wyniki obliczeń inwersji po procedurze składnia z wykorzystaniem metody inwersji rekursywnej. Uzyskane wyniki zestawiono z wynikami inwersji przed składaniem – inwersji symultanicznej. Następnie przy pomocy wykresów krzyżowych wykonano analizę służącą wskazaniu potencjalnych obszarów złożowych.praca magistersk
First Impressions of Using Stack Overflow for Education in a Computer Science Bachelor Programme
No full textCommunity Question Answering (CQA) platforms like Stack Over- flow enable gamified and moderated community-driven knowledge creation. We report on our experiences of introducing Stack Over- flow in our Computer Science BSc programme and explore whether these platforms can (1) reduce the workload of lecturers in answer- ing questions in large-scale classrooms, and (2) create a community of learners in the large-scale setting of ∼1600 students.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Software EngineeringComputer Science & Engineering-Teaching Tea
Stack Computers: the new wave
No full textPublished in 1989, this was the first book to explore the new breed of stack computers led by the introduction of the Novix NC4016 chip. The author commences with an overview of how stacks are used in computing, and a taxonomy of hardware stack support which includes a survey of approximately 70 stack machines past and present. Detailed descriptions, including block diagrams and instruction set summaries, are given for seven new stack processors from Harris Semiconductor, Novix, Johns Hopkins University/APL, MISC, WISC Technologies, and Wright State University. Major topics covered also include architectural analysis of stack machines, software issues, application areas, and potential for future development.</p
Investigating the usefulness of stack traces in bug triaging
No full textIn software engineering, resources such as time, money and developers, are limited. Often when bugs are found in the software developed, bug triaging is used to prioritise bug reports and allocate resources to it. When the number of bugs is considerable, this will require a vast amount of time and effort. The goal of this research is to investigate the usefulness of stack traces in bug reports for the assessment of bug report properties, using existing metrics of bug reports and files, being severity, priority and time-to-fix. In order to investigate the usefulness of stack traces, a research framework and methodology are developed. Overall, we can conclude that stack traces can be used to link software artifacts. Also, stack traces can be a valuable input for prediction models, for example using metrics of related bugs and source files.Software EngineeringSoftware TechnologyElectrical Engineering, Mathematics and Computer Scienc
Dynamic modeling of reversible solid oxide cell stack and control strategy development
No full textSolid oxide cell systems (SOCs) are increasingly being considered for electrical energy storage and as a means to boost the use of renewable energy and improve the grid flexibility by power-to-gas electrochemical conversion. The control of several variables (e.g., local temperature gradients and reactant utilization) is crucial when the stacks are used in dynamic operation with intermittent electrical power sources. In the present work, two 1D models of SOC stacks are established and used to investigate their dynamic behavior and to select and tune a suitable control strategy. Subsequently, safe operating ranges were determined to meet the thermal constraints of the stack by analysing not only the fuel cell (SOFC) and electrolyzer (SOEC) individual modes but also the switching between the two modes when the stack operates reversibly. The dynamic analysis shows that the control loops of our multi-input (reactant molar flow rates), multi-output (reactant utilization and maximum local temperature gradients) control system are strongly decoupled. Therefore, a proportional integral control strategy can be used to prevent dangerous stack operating conditions in dynamic operation. Finally, the controllers were tuned, and their transfer functions were reported. Convective heat transfer via air flow allows controlling the temperature of the solid structure of the cell/stack component, thus avoiding issues related to temperature variation during transient operation. Moreover, the reactant utilization controllers can avoid component fracture or degradation owing to fuel starvation under dynamic operation. The process can be approximated by two first order transfer functions. It can help in the design of more complex control systems in the future if necessary, with embedded process models, such as model predictive control. Results in the simulation environment are preparatory to the programming phase of an actual controller in real-world applications.Accepted Author ManuscriptEnergy Technolog
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