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The eventual goal is to construct three related “prismatization” functors from the category of p-adic formal schemes to that of formal stacks. This should provide a good category of coefficients for prismatic cohomology in the spirit of F-gauges. In this article we define and study the three versions of the prismatization of Spf Z p . [ABSTRACT FROM AUTHOR]

The objective of this article is to provide an in-depth exploration of the complex task of container storage at seaports, a problem characterized as one of the challenging NP (Non-Deterministic Polynomial time) problems. Seaports are faced with the dilemma of accommodating a finite number of containers due to the constrained surface area available, making the management of container storage operations a formidable task.

In the present study, the operational lifetime of a solid oxide fuel (SOFC) short stack is predicted by investigating the performance degradation of both the short stack and its cells throughout 1000 ​h at 800 ​°C. The short stack and integral cell voltages are continuously measured during the long-term test, with electrochemical impedance spectroscopy (EIS) conducted every 200 ​h. The short stack voltage decreased rapidly for the initial 200–300 ​h and afterwards, it decreased at a slow rate due to the increase in the Ohmic and polarization resistances in the same manner. Scanning electron microscopy results show that there is no delamination or cracking among constituent layers of the short-stack cells. The single degradation effects of the Ni coarsening in the anode, cation migration and surface segregation in cathode and oxide scale growth in metallic interconnect mesh are successfully integrated into a comprehensive lifetime prediction model. The experimentally measured voltage degradation data of the short stack fits well with the developed mathematical model and allows the successful prediction of the lifetime up to 50,000 ​h. • A lifetime prediction model for SOFC cell and stack is developed. • The model is based on real-time EIS and ex-situ image analysis-based modelling. • The prediction model integrates single degradation effects in SOFC electrodes. • The model is extendable to other materials systems for a wide range of applications. [ABSTRACT FROM AUTHOR]

To investigate flow uniformity within individual unit cells in internal manifold-type solid oxide fuel cell stacks with respect to electrical capacity and stack height variations, numerical analyses using computational fluid dynamics techniques were conducted on SOFC stack models with capacities of 1 kWe, 2 kWe, and 3 kWe. The results of these calculations reveal that while the inlet flow rate increases with an increase in the number of unit cells, the flow rate supplied to each unit cell remains largely consistent, resulting in a nearly uniform pressure drop in the core region. Nonetheless, the flow rate in the pipe and manifold regions increases proportionally to the inlet flow rate for 1 kWe, 2 kWe, and 3 kWe models, leading to a corresponding increase in pressure drop. Furthermore, the patterns of mass flow rate and pressure drop within unit cells are comparable. Particularly, the pressure drop within unit cell channels is primarily influenced by the pressure distributions in the outlet manifold regions. In summary, as the stack height increases, the uniformity of pressure and flow rate distributions among unit cells decreases. This effect is more pronounced in the cathode with a higher flow rate than the anode, and it has implications for achieving uniform flow rates while minimizing flow rates in individual unit cells. [ABSTRACT FROM AUTHOR]

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The levelized cost of electrochemical hydrogen remains significantly affected by stack replacement frequency, and therefore stack durability. Consequently, demonstrating relevant lifespans is paramount towards supporting the accelerating industrialization of solid oxide technology. Thus, two 30-cell electrolyte-supported stacks were tested in thermoneutral conditions, −0.52 A cm−2 and 70% steam conversion. The first stack comprised a variety of cells and over the 4.5 kh test sequence yielded a degradation rate of +22 mΩ cm2 kh−1, or +4.5 K kh−1. The second stack only included the best cell variant, and degraded at a much lower rate of +12 mΩ cm2 kh−1, or 2.5 K kh−1. The test lasted 9.5 kh, a record for full stacks operated in electrolysis mode. The present report details the testing equipment, the experimental conditions and procedures, and compares the performances and degradation rates recorded. In addition, special attention is given to the feed water quality over time. • The lifespan of two electrolyte-supported 30-cell stacks were evaluated. • Stack operation was in thermoneutral conditions at −0.52 A cm−2 and 70%SC. • The first test lasted 4.5 kh and degraded at +22 mΩ cm2 kh−1. • The second test lasted a record 9.5 kh and degraded at +12 mΩ cm2 kh−1. • Extrapolated lifespans at iso-performance were 6.8 and 11.5 kh. [ABSTRACT FROM AUTHOR]

Solid Oxide Fuel Cell (SOFC) stacks are one of the most critical modules in industrial SOFC energy conversion systems. Although the detailed multiphysics distribution has been elaborately studied with accurate 3-dimensional (3D) models, development and validation of agile stack model is yet inadequate. Due to slow and tedious meshing and simulation, fast prototyping of stacks remains a challenge. Therefore, a 30-cell stack was tested at varied temperatures and gas flowrates and a real-time transient layer-resolved stack model is established and calibrated using the measured data, which gives a Root-Mean-Square (RMS) prediction error of 2.21% for measured voltages and 1.53 °C for measured temperatures. With layer resolution, the stack model shows the voltage, average temperature, as well as fuel and air flowrates of each cell. Moreover, the stack model reveals the relation of voltage distribution at varied fuel flowrates with temperature distribution. Furthermore, the stack model is potentially applicable to stack scaling effects, or designing Balance of Plant (BoP). [Display omitted] • An accurate layer-resolved stack model for voltage/temperature distributions. • Low computational cost of the model enabling agile and real-time applications. • Explained the role of operating conditions on flowrate inhomogeneity. • Revealed strong impact of temperature on stack voltage distribution. [ABSTRACT FROM AUTHOR]

This article suggests a new waveguide design that utilizes a "walled" architecture. Instead of relying on conventional gap waveguide structures to create electronic bandgaps and prevent field leakage, the proposed design introduces a "walled" guiding mechanism. This technique preserves transmission while maintaining the multilayer approach and eliminates the need for nails or chemical bonds to attach the layers. Simulations were carried out in the W-band (75–110 GHz) and D-band (110–170 GHz) using several metals, and measurements were performed in the W-band using aluminum. The simulation results show that the reflection coefficient was less than −40 dB over the entire D-band. At the same time, the average insertion loss was around 0.0054 dB/mm and around 0.0065 dB/mm for silver and gold, respectively. Similarly, the reflection coefficient was less than −45 dB over the 75–110 GHz range, with an average insertion loss of 0.0018 dB/mm for silver and 0.003 dB/mm for gold, respectively. The aluminum model's reflection coefficient was less than −35 dB, and the average insertion loss was 0.0035 dB/mm. The experimental results achieved a reflection coefficient of less than –30 dB and the average transmission coefficient was −0.2 dB, with an insertion loss of 0.002 dB/mm. The simple stacking ability of the weightless walled metal plates and easy fabrication makes the proposed transmission line a promising technology in mmWave and Terahertz applications. [ABSTRACT FROM AUTHOR]

Foundation mathematics courses play a crucial role in allowing students who have not achieved the pre-requisite mathematics credits for tertiary studies to re-engage with STEM studies. This paper describes how targeting self-efficacy, skill development and social connectedness have influenced the design of a foundation mathematics course at a New Zealand university. These design goals are grounded in education literature, and the paper outlines how focusing on these goals has resulted in the design of a course that incorporates novel approaches to learning and assessment, including online and face-to-face components. These approaches include the use of large, automatically graded weekly quizzes; adaptive learning quizzes for essential skills such as fraction arithmetic; and an emphasis on face-to-face learning and connection through tutorials and collaborative problem-solving workshops. The paper concludes with reflections on the success of the course so far and raising questions for future investigation. [ABSTRACT FROM AUTHOR]

This study focuses on investigating the performance change of a high temperature proton exchange membrane fuel cell (HT-PEMFCs) stack at different operation modes. A HT-PEMFC stack consisting of 30 single cells was tested both at constant load (0.4 A cm−2) and dynamic load (0.05–0.4 A cm−2) conditions at a temperature of 160 ℃ and hydrogen as anode fuel. Besides, the effect of impurities on the stack was also investigated by feeding a methanol reformate mixture to the stack anode as fuel for both constant and dynamic operation. The results reveal that the stack performance was stable after 120 h of both constant and dynamic operation with hydrogen, while the stack performance decreased greatly when the stack was fed with dry reformate on the anode. Significant degradation rates of 94.4 µV h−1 for constant operation, while the degradation was 200 times higher in dynamic operation with reformate gas.

We present hidden abstract stack Markov models (HASMMs) with their learning process. The HASMMs we offer carry the more expressive nature of probabilistic context-free grammars (PCFGs) while allowing faster parameter fitting of hidden Markov models (HMMs). Both HMMs and PCFGs are widely utilized structured models, offering an effective formalism capable of describing diverse phenomena. PCFGs are better accommodated than HMMs such as for expressing natural language processing; however, HMMs outperform PCFGs for parameter fitting. We extend HMMs towards PCFGs for such applications, by associating each state of an HMM with an abstract stack, which can be thought of as the single-stack alphabet of pushdown automata (PDA). As a result, we leverage the expressive capabilities of PCFGs for such applications while mitigating the cubic complexity of parameter learning in the observation sequence length of PCFGs by adopting the bilinear complexity of HMMs.

Solid oxide electrolysis is considered an efficient technology to produce hydrogen. To deploy electrolysers at the GW scale, an increase in the individual component size (cells and stacks in particular) is required. The integration of larger cells (200 cm2 active area) into 25‐cell stacks has been successfully performed. Performances were in the range of –0.8 to –0.9 A cm−2 at 1.3 V at 700°C. The number of cells has also been increased to 50 and 75 cells. For this latter 75‐cell stack, the assembly of three 25‐cell substacks was considered. Good gastightness and high performances were achieved, although connections between substacks add a serial resistance that affects the stack total performances. Nevertheless, a current density of more than –0.8 A cm−2 was obtained at 1.3 V and 700°C, consistent with individual substack performances. Finally, a stack made of 50 200 cm2 cells has been assembled. Although a stack deformation was visible due to individual component thickness scattering, a good gastighness was achieved and a current density of –0.9 A cm−2 at 1.3 V and 700°C was measured. The low voltage scattering highlighted a good homogeneity of the fluidic distribution and of the electrical contacts within the stack. [ABSTRACT FROM AUTHOR]

In the current landscape of high temperature electrolysis, mainly two solid oxide cell (SOC) technologies are being used: electrolyte‐supported and cathode‐supported SOCs. The geometrical differences, namely the thickness of the electrolyte, can lead to vastly different operating temperatures. Since most phenomena affecting performance and durability remain thermally activated, comparing stack technologies can be a difficult endeavor at best. While the most visible goal of the European project MultiPLHY consists of Sunfire GmbH building the first multi‐megawatt solid oxide electrolyzer, a work package is being dedicated to stack testing in a laboratory environment. A harmonized protocol was first elaborated to allow comparing different stack technologies. It includes the recording of performance maps, several galvanostatic steps in thermoneutral conditions, as well as load point and thermal cycles. Subsequently, Sunfire operated a pile‐up of two 30‐cell electrolyte‐supported stacks for over 8200 h, while a 25‐cell cathode‐supported stack was tested at CEA for 6800 h. The present article aims at presenting the findings gathered during the implementation of the protocol. This benchmark study puts forward performance maps as well as voltage and stack temperature profiles over time, and discusses some of the difficulties inherent to long‐term testing. [ABSTRACT FROM AUTHOR]

In this work, we present a case where electrochemical impedance spectroscopy (EIS) on stack level enabled the identification of degradation and failure mechanisms in a 75‐cell solid oxide electrolysis cell (SOEC) stack from Topsoe. In a blind test, a defective stack (stack not passing the quality control specifications) prone to degradation was investigated with EIS. The type of stack defects was not known a priori. The purpose of the stack EIS experiment was hence to serve as a proof‐of‐concept of using EIS on the stack level for identifying degradation mechanisms. An appropriate equivalent circuit model was applied and fitted to the experimentally obtained EIS data, which enabled the quantification of the different electrochemical contributions. We hereby identified which electrochemical contribution(s) to the overall stack resistance caused the stack to degrade. Furthermore, the data was plotted in a degradation space format, which further strengthened the identification of the cause of degradation. In this work, we are exploring and utilizing the potential of advanced EIS characterization and analysis; thereby successfully identifying some of the degradation and failure mechanisms taking place in the SOEC stack. This detailed type of degradation analysis has, to the best of my knowledge, not previously reported on the commercial stack level. [ABSTRACT FROM AUTHOR]

E-Learning platforms such as Moodle, Blackboard and Canvas have got reasonable attention in teaching and learning processes. However, when it comes to assessment and interactive learning activities they offer little service to science, engineering, and mathematics e-learners. In this work, we present the application of the System for Teaching and Assessment using Computer Algebra Kernel (STACK) as a plugin in a Learning Management System (LMS) to address the issue. Different features of STACK are demonstrated and discussed. As an LMS plugin, STACK can be used for interactive delivery of content as well as an assessment tool. Here, examples from mathematics, physical sciences and engineering are demonstrated. The use of STACK extends the applicability of LMS for a wider range of subjects to address existing inability to handle higher level mathematical and computational skills. Additionally, the use of STACK in an LMS is useful in handling tutorials for large classes especially when a blended delivery mode is preferred. [ABSTRACT FROM AUTHOR]

E-learning is seen as a new philosophy of education that encompasses all existing forms of education, including full-time education. Currently, there is a wide variety of software for developing interactive content. The aim of this study is to improve students' learning of Linear Algebra I using STACK (the system for teaching and assessment using a computer algebra kernel) at Bahir Dar University. The experience of using STACK questions has shown that their application helps students of all forms of education in learning Linear Algebra I and greatly facilitates the learning process of students, allowing them to master the contents of Linear Algebra I. In a mastery quiz, students try different algebra content repeatedly until they understand the concept. After students have mastered the content, they take a test quiz. Moreover, STACK helps teachers in a scoring (cumulative) system of knowledge assessment, makes the learning outcomes more visible and convenient for analysis. In addition, it is noted in the research that the STACK tasks allow students to review analytical solutions to complex types of problems and organize hints that help them to solve tasks. The approach saves the teacher's time to check solutions at any time and give students individual options for tasks. As part of the study, the STACK tasks were analysed, which revealed a greater number of advantages of learning and assessment compared to its disadvantages and revealed the possibility of its application in the educational process. It is recommended that educational policy makers must integrate STACK into a curriculum of Mathematics. [ABSTRACT FROM AUTHOR]

Management of large classes' tutorials is a known problem in Mathematics. Engineering mathematics classes enrol around 1000 students at the University of Dar es Salaam. For effective learning, each tutorial session should register not more than 40 students. This requires at least 25 sessions of tutorials per week, which may not be feasible due to both scarce human resources and venues. In this work, we developed online Mathematics exercises based on the System for Teaching and Assessment using Computer Algebra Kernel (STACK). About 300 STACK questions in linear algebra, calculus, complex numbers, and numerical analysis were constructed for weekly tutorials and quizzes. Students were given an unlimited number of attempts in tutorials and only one attempt for quizzes. The quality of the questions was analysed by examining their facility indices and discriminative efficiencies. Majority of the questions (87%) were within acceptable region. The questions, therefore, provided reasonable insight as appropriate alternative to classical practice. Competent authoring of STACK questions can improve the quality of teaching and learning of Mathematics and save scarce human and material resources required to serve large classes. This can also address the issue of running online programmes in Mathematics and computational subjects to support distance learning. [ABSTRACT FROM AUTHOR]

In the context of carbon neutrality, conversion of CO2 into CO is an effective way for negative carbon emission. Electrochemical reduction is a novel developed pathway, among which, solid oxide co-electrolysis technology is promising for its high efficiency and low electricity demand. Researches concerning the large-size cell and stack of application level are important. This review, targeting at the not yet fully understood reaction mechanism and the most concerning issue of durability, details the reported factors playing important roles in the reaction mechanism and durability of co-electrolysis. It is found that the operating conditions such as inlet mixtures and applied current significantly affect the reaction mechanism of co-electrolysis and the experiments on button cells can not reflect the real reaction mechanism on industrial-size cells. Besides, the durability test of large-size single cells and stacks at high current with high conversion rate and the potential of solid oxide co-electrolysis combing with intermittent renewable energy are also reviewed and demonstrated. Finally, an outlook for future exploration is also offered.

Fuel cell electric vehicles represent a possible solution to meet the objectives of the energy transition currently underway, which sees the replacement of combustion vehicles with low environmental impact vehicles. For this reason, this market is expected to markedly grow in the coming years. Currently, the most suitable fuel cell technology for both light and heavy transport applications is the Proton Exchange Membrane fuel cell. This review provides a comprehensive description of the state of the art of fuel cell electric vehicles at different levels: vehicle configuration, fuel cell stack, and all the necessary operation systems. The current advantages and limits of the mentioned technology are highlighted, referring to recent studies aimed at optimizing the efficiency of the system and providing future perspectives. [ABSTRACT FROM AUTHOR]

In undergraduate mathematics education, students' collaborations have gained a reputation as a 'good' learning practice. A more complex image emerges once collaborations are construed as an arena where cognitive, social, and affective matters intertwine in ways that can fuel and impede learning. In this study, I take a close look at a twenty-minute-long interaction between two first-year students who engaged in a sequence of routine problems about dot products presented in a computer-based learning-support system. The commognitive analysis of the interaction revealed an asymmetrical structure: one student led the mathematizing, while his partner followed and invested considerable efforts to avoid making a mathematical contribution. The leader's attempts to switch positions and inquiry into the follower's recurrent refusals to mathematize entailed loaded exchanges that took a toll on both students in terms of identity and affect. I compare these findings to previous studies with school students to discuss possible sources of ineffective communication in situations where students are expected to learn through collaborations. [ABSTRACT FROM AUTHOR]

This paper explores the relationship between two emerging technologies, WebAssembly (Wasm) and the Internet of Things (IoT). It examines the complementary roles of these technologies and their impact on modern web applications. First, it delves into the capabilities of Wasm as a high-performance binary format that allows developers to leverage low-level languages for computationally intensive tasks. Second, it seeks to explain why integration of IoT and Wasm is important. Third, it discusses the strengths and limitations of various tools and tool chains that are crucial for Wasm development and implementation, with a special focus on IoT. Fourth, it presents the state-of-the-art with regard to advances that combine both technologies. Fifth, it discusses key challenges and provides future directions. Lastly, it provides an in-depth elaboration of the future aspects of Wasm, with a strong focus on IoT, concluding that IoT and Wasm can provide developers with a versatile toolkit that enables them to balance productivity and performance in both web and non-web development scenarios. The collaborative use of these technologies opens up new possibilities for pushing the boundaries of web application development in terms of interactivity, security, portability, scalability, and efficient computational capabilities. As web and non-web embeddings continue to evolve, the integration of IoT and Wasm will play a crucial role in shaping the future of innovative application development. The key findings of this extensive review work suggest that existing tool sets can be easily conglomerated together to form a new era in WebAssembly–IoT infrastructure for low-power, energy-efficient, and secure edge–IoT ecosystems with near-native execution speed. Furthermore, the expansion of edge–IoT ecosystems can be augmented with prospective cloud-side deployments. However, there remains a strong need to more cohesively advance the amalgamation of Wasm and IoT technologies in the near future. [ABSTRACT FROM AUTHOR]

In this study, thin molybdenum‐containing, nickel‐based metal‐supported solid oxide fuel cells (MS‐SOFCs) were fabricated through atmospheric plasma spraying and then characterized. We investigated the change in cell performance associated with the reduction of the Ni–Mo support layer thickness from 200 to 80 µm and reduction of the substrate sintering temperature from 1200 to 1000°C. At a cell voltage of 0.6 V, the measured maximum power density values of a 50 × 50 mm2 MS‐SOFC were 313, 581, 890, and 1098 mW cm−2 at 600, 650, 700, and 750°C, respectively. A 100 × 100 mm2 (commercial‐size) MS‐SOFC and an assembled single‐cell MS‐SOFC stack exhibited electric output power values of approximately 33 and 39 W at 700 and 750°C, respectively, and an effective electrode area of 81 cm2. In a long‐term stability test, the commercial‐size cell and single‐cell stack exhibited a degradation rate of approximately 1% after 1000 h of operation at a current density of 250–300 mA cm−2 and temperature of 700°C. Moreover, a five‐cell MS‐SOFC stack demonstrated a stack power of 180.85 W at 3.792 V (446.5 mW cm−2 at 0.758 V) and 750°C. [ABSTRACT FROM AUTHOR]

We prove a rigidity result for automorphisms of points of certain stacks admitting adequate moduli spaces. It encompasses as special cases variations of the moduli of G-bundles on a smooth projective curve for a reductive algebraic group G. For example, our result applies to the stack of semistable G-bundles, to stacks of semistable Hitchin pairs, and to stacks of semistable parabolic G-bundles. Similar arguments apply to Gieseker semistable G-bundles in higher dimensions. We present two applications of the main result. First, we show that in characteristic 0 every stack of semistable decorated G-bundles admitting a quasiprojective good moduli space can be written naturally as a G-linearized global quotient Y/G, so the moduli problem can be interpreted as a GIT problem. Secondly, we give a proof that the stack of semistable meromorphic G-Higgs bundles on a family of curves is smooth over any base in characteristic 0. [ABSTRACT FROM AUTHOR]

The successful introduction of the technology of copper production using a dump leaching method is associated with low capital investments, low cost of copper extraction, quick payback, high labor productivity, and the absence of energy- and material-intensive operations. The experience of implementing dump leaching technology has shown that negative temperatures significantly worsen the conditions and the rate of migration of metal-bearing solutions, resulting in freezing of blocks in winter. Therefore, the main task of increasing the efficiency of dump leaching in Kazakhstan is to enable the successful use of the process under winter conditions in a sharply continental climate (at a temperature of –25°C). The article describes the commercial implementation of the model of winter leaching of copper from the overburden dumps of spent sulfide ores at the Kounrad mine at negative ambient temperatures. The method is applied to mature dumps of various heights, while employing a surface irrigation device and facilitating collection of the product solutions into a pit equipped with a secondary containment berm. In this case, the bottom of the pit and the sides of the berm are covered with a waterproof layer of clay and a geosynthetic screen. In order to organize a sustainable leaching process during winter, the evaporation surfaces of the leaching blocks are covered with a geocomposite having thermal insulation and waterproofing properties. Efficient and continuous flow of the dump-based production process throughout the calendar year is ensured by maintaining a process-favorable temperature regime of the solutions and dump surfaces under extreme winter temperatures and high winds. It was shown that the temperature of the solution supplied for leaching can be reduced by 3°C due to better thermal insulation properties of the geocomposite. The pressure drop in the lines of the block covered with geocomposite during the entire period of pilot tests did not exceed 0.5 MPa, which indicates excellent efficiency of the geocomposite and a large margin in terms of performance parameters of the block at extremely low temperatures. [ABSTRACT FROM AUTHOR]

Periodic maintenance of stack aviation lamps was taken up in the Compact Reprocessing of Advanced Fuels in Lead Cells reprocessing plant in Kalpakkam. The entire ventilation system of the plant had to be shut down during this maintenance work. When the ventilation system is switched off, natural radioactivity will build up in the working environment. The increased magnitude of the natural radioactivity concentration was estimated by counting the air samples (AS) at predetermined intervals to ensure no long-lived radionuclide (LLR) was present in the AS. The extent of the natural radioactivity rose to a factor of 100, and no LLR was present in the collected AS. In addition, the collected AS and data analysis of the same revealed that there was no breach of containment during the work. [ABSTRACT FROM AUTHOR]

A shrouded air sampling probe was designed and fabricated to meet the effluent monitoring requirements of an upcoming reprocessing facility at IGCAR. Performance evaluation of the probe was carried out using standard polydisperse aerosols up to 2 µm at the high-efficiency particulate air filter test facility. Its performance was also verified for higher size particles till 10 µm using the "Deposition 2001a" code. Based on the results, the shrouded probe was found to qualify the air sampling requirements and the same was fixed at the sampling point in the exhaust duct. This paper describes the details of design, testing, and installation of the shrouded probe. [ABSTRACT FROM AUTHOR]

This article is about the design, development and validation of a new monitoring architecture for individual cells and stacks to facilitate the study of proton exchange fuel cells. The system consists of four main elements: input signals, signal processing boards, analogue-to-digital converters (ADCs) and a master terminal unit (MTU). The latter integrates a high-level graphic user interface (GUI) software developed by National Instruments LABVIEW, while the ADCs are based on three digital acquisition units (DAQs). Graphs showing the temperature, currents and voltages in individual cells as well as stacks are integrated for ease of reference. The system validation was carried out both in static and dynamic modes of operation using a Ballard Nexa 1.2 kW fuel cell fed by a hydrogen cylinder, with a Prodigit 32612 electronic load at the output. The system was able to measure the voltage distributions of individual cells, and temperatures at different equidistant points of the stack both with and without an external load, validating its use as an indispensable tool for the study and characterization of these systems. [ABSTRACT FROM AUTHOR]

The seismic reflection method is the primary tool to provide detailed information on the near‐surface. This paper proposes a common receiver correlation stack method. A towed seismograph is used to perform the rapid acquisition with small geophone spacing and a high sample rate, while broadband (from 1 Hz to 1000 Hz) seismic data are collected. Results of modelled and measured data indicate that the proposed stack method: (1) does not need normal move‐out velocity; (2) does not lose shallow information; and (3) improves the stacking fold by twice as much as the conventional stack method. Compared with the conventional stack method, the proposed method can suppress surface waves better and improve the quality of the final sack section, especially for high‐frequency data. Combined with the towed seismograph, the proposed stack method can perform the rapid collection and enhance the accuracy of stack imaging of near‐surface seismic data. [ABSTRACT FROM AUTHOR]

The rapid growth of urbanization and industrialization cause the world face with the most important environmental issues of air pollution in many cities and industrial zones. In the present research, air pollution due to the emission of pollutants air quality is studied. Emission and dispersion of NOx from a stack located in an industrial zone are simulated based on the meteorological data. The geometry of the stack and surrounding area are selected from a power plant data. The analysis is individually performed for four seasons using the wind field and direction. It is shown that wind direction significantly affects the pollutants circulation zone. The pollutants inversion are unpreventable occurred in winter because of the mixing area is not well altitudinal extended. [ABSTRACT FROM AUTHOR]

Crop mapping and its health monitoring are of key importance for a country like Pakistan where a considerable share of the GDP originates from agricultural production. Currently, extensive capital and human resource are utilized to record the crop types and monitor crop health due to variations in crop pattern and intercropping practices being observed in many parts of the country. Satellite Remote Sensing, however, can be utilized very efficiently to identify crop types and estimate acreage by using unique phenological cycles derived from NDVI thresholds. In this research, we proposed a semi-automated, efficient and cost-effective state-of-the-art technique for crop classification using satellite remote sensing datasets and GIS techniques to replace outdated conventional survey-based crop estimations procedures. This research was conducted in Sahiwal district, Pakistan to categorise several crop types using two major inputs: satellite (Sentinel-2, 10m) imagery and local crop calendar. The research adopted a semi-automatic approach to find the main crops of Rabi (winter) and Kharif (summer) using orthorectified and atmospherically corrected Level-1C images to extract phenological information based on Normalized Difference Vegetation Index (NDVI). The complete phenological life cycle of crops including sowing, growing, and harvesting stages were deeply analyzed with the help of crop calendar and NDVI profiles. Then this information passed through iterative selforganizing (ISO Data Model) of unsupervised classification technique in the form of temporal stacked images. The NDVI profiles of each crop were synchronized with the crop calendar of the study area to develop the crop categorization procedure. The results were validated with the statistics of the agriculture department Lahore and field samples gave about 85% and 88% accuracy for Rabi and Kharif cropping seasons respectively. It is concluded from the research that the tested methodology is capable of providing a fast, cost-efficient, and reliable solution for crop mapping instead of conventional survey-based crop area assessment techniques (conventional Girdawri) which requires a vast number of resources and time, and it can be replicated in different areas with minor changes. [ABSTRACT FROM AUTHOR]

A significant part of the population in Serbia relies on central heating systems during the winter months, with around fifty heating plants in operation across the country. Common fuels used in these plants primarily include fossil fuels such as fuel oil and natural gas. Combustion of some of these fuels leads to significant emissions of air pollutants. This study evaluates the impact on the air quality of the two heating boilers at the Valjevo city, Serbia, heating plant. Air emissions were measured separately for two heating boilers in the facility using standard reference methodology. The AERMOD air dispersion model was used to estimate the dispersion of various pollutants. A combination of topographical and meteorological data was used to set up a receptor grid exposed to air pollution within a 10 km radius around the heating plant. It was found that the resulting distribution and concentration gradient of pollutant gases and particles were less inclined towards the city center and instead spread eastwards into the surrounding villages. The health risk from the fuel oil boiler was shown to be significantly higher than that caused by the natural gas-fuelled boiler. Nevertheless, the calculated carcinogenic and non-carcinogenic health risks were within acceptable limits. However, further research is required to adequately assess the cumulative health risk generated by other surrounding emitters. [ABSTRACT FROM AUTHOR]

In this study, a new cooling strategy for a proton exchange membrane (PEM) fuel cell stack is investigated using a three-dimensional (3D) multiphase non-isothermal model. The new cooling strategy follows that of the Honda's Clarity design and further extends to a cooling unit every five cells in stacks. The stack consists of 5 fuel cells sharing the inlet and outlet manifolds for reactant gas flows. Each cell has 7-path serpentine flow fields with a counter-flow configuration arranged for hydrogen and air streams. The coolant flow fields are set at the two sides of the stack and are simplified as the convective heat transfer thermal boundary conditions. This study also compares two thermal boundary conditions, namely limited and infinite coolant flow rates, and their impacts on the distributions of oxygen, liquid water, current density and membrane hydration. The difference of local temperature between these two cooling conditions is as much as 6.9 K in the 5-cell stack, while it is only 1.7 K in a single cell. In addition, the increased vapor concentration at high temperature (and hence water saturation pressure) dilutes the oxygen content in the air flow, reducing local oxygen concentration. The higher temperature in the stack also causes low membrane hydration, and consequently poor cell performance and non-uniform current density distribution, as disclosed by the simulation. The work indicates the new cooling strategy can be optimized by increasing the heat transfer coefficient between the stack and coolant to mitigate local overheating and cell performance reduction.

In this study, a new cooling strategy for a proton exchange membrane (PEM) fuel cell stack is investigated using a three-dimensional (3D) multiphase non-isothermal model. The new cooling strategy follows that of the Honda's Clarity design and further extends to a cooling unit every five cells in stacks. The stack consists of 5 fuel cells sharing the inlet and outlet manifolds for reactant gas flows. Each cell has 7-path serpentine flow fields with a counter-flow configuration arranged for hydrogen and air streams. The coolant flow fields are set at the two sides of the stack and are simplified as the convective heat transfer thermal boundary conditions. This study also compares two thermal boundary conditions, namely limited and infinite coolant flow rates, and their impacts on the distributions of oxygen, liquid water, current density and membrane hydration. The difference of local temperature between these two cooling conditions is as much as 6.9 K in the 5-cell stack, while it is only 1.7 K in a single cell. In addition, the increased vapor concentration at high temperature (and hence water saturation pressure) dilutes the oxygen content in the air flow, reducing local oxygen concentration. The higher temperature in the stack also causes low membrane hydration, and consequently poor cell performance and non-uniform current density distribution, as disclosed by the simulation. The work indicates the new cooling strategy can be optimized by increasing the heat transfer coefficient between the stack and coolant to mitigate local overheating and cell performance reduction.

The relevance of the problem of increasing the efficiency of using the metallic mineral resources extracted from the bowels on the earth's surface is explained by the increasing demand of industrial metals to meet the vital queries of the human. The aim of the study is to develop environment-friendly and resource-saving technologies of extracting metals from sub-standard raw materials in underground mining of metallic mineral deposits. Research methodology includes a set of methods that collectively define the feasibility of involvement in production of non-conforming metallic resources using hydrometallurgical technologies and increasing the extraction of metals compared to traditional washing technology. The main method is semi-experimental leaching of uranium ore in the pile. The results of the research allow us to optimize the organization of work on leaching metals by controlling the process parameters at all stages of leaching of off-grade mineral raw materials in the stacks with a differentiated assessment of the influence of major processes on leaching rates. The paper introduces the data on consumption of reagents and materials, extraction of metals into solution and out of solution and neutralization of the mother liquor. It is shown that leaching in the pile does not radically improve performance of traditional methods of extraction of metals, but only reduces the metal content in the secondary tails. The paper identifies the deficiencies of existing methods of assessing the impact of mining on the environment. The conclusion from the results of the study is that leaching in a stack does not solve the problem of non-waste, essentially increasing the exposure time of chemically hazardous products to living matter.

As an efficient energy converter, the proton exchange membrane fuel cell (PEMFC) is developed to couple various applications, including portable applications, transportation, stationary power generation, unmanned underwater vehicles, and air independent propulsion. PEMFC is a complex system consisting of different components that can be influenced by many factors, such as material properties, geometric designs operating conditions, and control strategies. The interaction between components and subsystems could affect the performance, durability, and lifespan of PEMFC system. To design a high performance, long lifespan, high durability PEMFC, it's essential to comprehensively understand the coupling effect of different factors on the overall performance and durability of PEMFCs. This review will present existing research on basis of four aspects, involving fuel cell stack design, subsystems design and management, mass transfer enhancement, and system integration. Firstly, the multi-physics intergradation and component design of PEMFC are reviewed with the designing mechanisms and recent progress. Besides, mass transfer enhancement methods are discussed by bipolar plate design and membrane electrode assembly optimization. Then, water management, thermal management, and fuel management are summarized to provide design guidance for PEMFC. The specifications design and system management for various engineering applications are briefly presented. • The key components, systems, control strategy of PEMFC were reviewed in terms of theory and model. • The guideline for designing a high performance, long lifespan, high durability PEMFC was provided. • Different applications and system of PEMFCs were expressed by drawing extension. [ABSTRACT FROM AUTHOR]

Thermoacoustic devices are converters of thermal energy into acoustic energy and vice versa. Although these machines contain simple components, the design of these machines is very challenging. In order to predict the behavior and optimize the efficiency of a standing-wave thermoacoustic engine designed to drive a thermally driven thermoacoustic refrigerator, considering changes in geometrical parameters and operating conditions, two analogies have been presented in this paper. The first analogy is based on a CFD simulation carried out to investigate the influence of stack parameters, working gas and boundary conditions on the thermoacoustic process. The second analogy is performed by the use of an optimization algorithm based on the simplified linear thermoacoustic theory to design and optimize the parameters investigated by the CFD study. Stack of parallel plates of normalized stack center positions of 0.007 to 0.26, normalized stack lengths of 0.018 to 0.11, and several gaps and thicknesses of plates and working gases are used. The results from the algorithm give the ability to design any thermoacoustic engine with high efficiency by picking the appropriate parameters. Simulation results show that decreasing thickness and position of the plates gives a significant efficiency. However, there are optimum values for length of the stack and the gap between two plates. The material chosen for the construction of plates should have a low thermal conductivity and gases with higher ratios of specific heats and lower Prandtl numbers are well suitable for thermoacoustic systems. [ABSTRACT FROM AUTHOR]

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the complex product research and experimental development project, activities overlapping is usually used to shorten project duration. Currently, most meth- ods for resource constrained project scheduling problem with activities overlapping are based on heuristic algorithm. This method has the advantages of fast-speed conver- gence and large-scale calculation, but cannot obtain the optimal solution. The accurate algorithm is an effective method to solve the optimal solution of the above problem. Therefore, a branch and bound method is designed to obtain the optimal solution according to examine the impact of overlapping activities on project scheduling. Firstly, the optimality of the algorithm is proved in theory. The optimal solution can be obtained only by considering the minimum delay substitution set, and cut set domination rule and left shift domination rule in pruning operation is proved. Secondly, in the algorithm design, the data structure{stack is used to store the node information on the search tree, and for the activities overlapping constraint, a new decision point and a new representation method of the search tree node are defined. Finally, the feasibility and effectiveness of the algorithm are verified by a large number of instances. In conclusion, the proposed algorithm has high research value with mature theoretical significance and accurate calculation results. [ABSTRACT FROM AUTHOR]