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Zhou, Wei, Haoran Li, Shiya Wen, Lijuan Xie, Ting Wang, Yongzhong Tian i Wenping Yu. "Simulation of Soil Organic Carbon Content Based on Laboratory Spectrum in the Three-Rivers Source Region of China". Remote Sensing 14, nr 6 (21.03.2022): 1521. http://dx.doi.org/10.3390/rs14061521.
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Soil organic carbon (SOC) changes affect the land carbon cycle and are also closely related to climate change. Visible-near infrared spectroscopy (Vis-NIRS) has proven to be an effective tool in predicting soil properties. Spectral transformations are necessary to reduce noise and ensemble learning methods can improve the estimation accuracy of SOC. Yet, it is still unclear which is the optimal ensemble learning method exploiting the results of spectral transformations to accurately simulate SOC content changes in the Three-Rivers Source Region of China. In this study, 272 soil samples were collected and used to build the Vis-NIRS simulation models for SOC content. The ensemble learning was conducted by the building of stack models. Sixteen combinations were produced by eight spectral transformations (S-G, LR, MSC, CR, FD, LRFD, MSCFD and CRFD) and two machine learning models of RF and XGBoost. Then, the prediction results of these 16 combinations were used to build the first-step stack models (Stack1, Stack2, Stack3). The next-step stack models (Stack4, Stack5, Stack6) were then made after the input variables were optimized based on the threshold of the feature importance of the first-step stack models (importance > 0.05). The results in this study showed that the stack models method obtained higher accuracy than the single model and transformations method. Among the six stack models, Stack 6 (5 selected combinations + XGBoost) showed the best simulation performance (RMSE = 7.3511, R2 = 0.8963, and RPD = 3.0139, RPIQ = 3.339), and obtained higher accuracy than Stack3 (16 combinations + XGBoost). Overall, our results suggested that the ensemble learning of spectral transformations and simulation models can improve the estimation accuracy of the SOC content. This study can provide useful suggestions for the high-precision estimation of SOC in the alpine ecosystem.
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Xu, Yine, Qi Yu, Yan Zhang i Weichun Ma. "Numerical Study on the Plume Behavior of Multiple Stacks of Container Ships". Atmosphere 12, nr 5 (5.05.2021): 600. http://dx.doi.org/10.3390/atmos12050600.
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This paper showed different plume behaviors of exhausts from different number of stacks of the container ship, using CFD code PHOENICS version 6.0. The plume behavior was quantitatively analyzed by mass fraction of the pollutant in the exhaust and plume heights. Three simplified typical configurations were constructed by CFD according to the investigation of container ships. The configurations included a single main stack (BL1), one main stack and multiple auxiliary stacks (BL2), and two main stacks and multiple auxiliary stacks (BL3). All the main stacks had the same emission characteristics, and all the auxiliary stacks had the same emission characteristics. The results show that the transmission and diffusion characteristics of the exhaust from multiple stacks are different from those of the exhaust from a single stack. In BL2 and BL3 simulations, the maximum mass fraction of SO2 in the exhaust (C1max) of multiple stack emissions was approximately 329% and 269% higher than that of single stack emissions over the main stack, respectively, and the plume height of multiple stack emissions is higher than that of single stack emissions. In BL2 and BL3 simulations, the plume height of multiple stack emissions was 41% and 75% higher than that of single stack emissions, respectively. The increase of C1max, due to multiple stack emissions, is weakened as the distance of the stacks increase. The difference in plume behavior between multiple stack emissions and single stack emissions is of great significance for air quality management and pollution control in port areas.
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Cerbai, Giulio, Anders Claesson i Luca Ferrari. "Stack sorting with restricted stacks". Journal of Combinatorial Theory, Series A 173 (lipiec 2020): 105230. http://dx.doi.org/10.1016/j.jcta.2020.105230.
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Smith, Rebecca. "Two Stacks in Series: A Decreasing Stack Followed by an Increasing Stack". Annals of Combinatorics 18, nr 2 (8.05.2014): 359–63. http://dx.doi.org/10.1007/s00026-014-0227-8.
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Kim, Hanki, Jiyeon Choi, Namjo Jeong, Yeon-Gil Jung, Haeun Kim, Donghyun Kim i SeungCheol Yang. "Correlations between Properties of Pore-Filling Ion Exchange Membranes and Performance of a Reverse Electrodialysis Stack for High Power Density". Membranes 11, nr 8 (10.08.2021): 609. http://dx.doi.org/10.3390/membranes11080609.
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The reverse electrodialysis (RED) stack-harnessing salinity gradient power mainly consists of ion exchange membranes (IEMs). Among the various types of IEMs used in RED stacks, pore-filling ion exchange membranes (PIEMs) have been considered promising IEMs to improve the power density of RED stacks. The compositions of PIEMs affect the electrical resistance and permselectivity of PIEMs; however, their effect on the performance of large RED stacks have not yet been considered. In this study, PIEMs of various compositions with respect to the RED stack were adopted to evaluate the performance of the RED stack according to stack size (electrode area: 5 × 5 cm2 vs. 15 × 15 cm2). By increasing the stack size, the gross power per membrane area decreased despite the increase in gross power on a single RED stack. The electrical resistance of the PIEMs was the most important factor for enhancing the power production of the RED stack. Moreover, power production was less sensitive to permselectivities over 90%. By increasing the RED stack size, the contributions of non-ohmic resistances were significantly increased. Thus, we determined that reducing the salinity gradients across PIEMs by ion transport increased the non-ohmic resistance of large RED stacks. These results will aid in designing pilot-scale RED stacks.
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Toën, Bertrand. "Descente fidèlement plate pour les n-champs d’Artin". Compositio Mathematica 147, nr 5 (25.07.2011): 1382–412. http://dx.doi.org/10.1112/s0010437x10005245.
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AbstractWe prove two flat descent results in the setting of Artin n-stacks. First of all, a stack for the etale topology which is an Artin n-stack (in the sense of Simpson and Toën–Vezzosi) is also a stack for the flat (fppf) topology. Moreover, an n-stack, for the fppf topology, which admits a flat (fppf) n-atlas is an Artin n-stack (i.e. possesses a smooth n-atlas). We deduce from these two results a comparison between etale and fppf cohomologies (with coefficients in non-smooth group schemes and also non-abelian). This work is written in the setting of the derived stacks of Toën and Vezzosi, and all of these results are therefore also valid for derived Artin n-stacks.
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Halpern-Leistner, Daniel, i Anatoly Preygel. "Mapping stacks and categorical notions of properness". Compositio Mathematica 159, nr 3 (marzec 2023): 530–89. http://dx.doi.org/10.1112/s0010437x22007667.
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One fundamental consequence of a scheme $X$ being proper is that the functor classifying maps from $X$ to any other suitably nice scheme or algebraic stack is representable by an algebraic stack. This result has been generalized by replacing $X$ with a proper algebraic stack. We show, however, that it also holds when $X$ is replaced by many examples of algebraic stacks which are not proper, including many global quotient stacks. This leads us to revisit the definition of properness for stacks. We introduce the notion of a formally proper morphism of stacks and study its properties. We develop methods for establishing formal properness in a large class of examples. Along the way, we prove strong $h$ -descent results which hold in the setting of derived algebraic geometry but not in classical algebraic geometry. Our main applications are algebraicity results for mapping stacks and the stack of coherent sheaves on a flat and formally proper stack.
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Bursztyn, Henrique, Francesco Noseda i Chenchang Zhu. "Principal Actions of Stacky Lie Groupoids". International Mathematics Research Notices 2020, nr 16 (5.07.2018): 5055–125. http://dx.doi.org/10.1093/imrn/rny142.
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Abstract Stacky Lie groupoids are generalizations of Lie groupoids in which the “space of arrows” of the groupoid is a differentiable stack. In this paper, we consider actions of stacky Lie groupoids on differentiable stacks and their associated quotients. We provide a characterization of principal actions of stacky Lie groupoids, that is, actions whose quotients are again differentiable stacks in such a way that the projection onto the quotient is a principal bundle. As an application, we extend the notion of Morita equivalence of Lie groupoids to the realm of stacky Lie groupoids, providing examples that naturally arise from non-integrable Lie algebroids.
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Wu, Chien-Chang, i Tsung-Lin Chen. "Dynamic Modeling of a Parallel-Connected Solid Oxide Fuel Cell Stack System". Energies 13, nr 2 (20.01.2020): 501. http://dx.doi.org/10.3390/en13020501.
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This study proposes novel simulation methods to model the power delivery function of a parallel-connected solid-oxide-fuel-cell stack system. The proposed methods are then used to investigate the possible thermal runaway induced by the performance mismatch between the employed stacks. A challenge in this modeling study is to achieve the same output voltage but different output current for each employed stack. Conventional fuel-cell models cannot be used, because they employ fuel flow rates and stack currents as the input variables. These two variables are unknown in the parallel-connected stack systems. The proposed method solves the aforementioned problems by integrating the fuel supply dynamics with the conventional stack models and then arranging them in a multiple-feedback-loop configuration for conducting simulations. The simulation results indicate that the proposed methods can model the transient response of the parallel-connected stack system. Moreover, for the dynamics of the power distribution, there exists an unstable positive feedback loop between employed stacks when the stack temperatures are low, and a stable negative feedback loop when the stack temperatures are high. A thermal runaway could be initiated when the dynamics of the stack temperature is slower than that of the current distribution.
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Defant, Colin, i Kai Zheng. "Stack-sorting with consecutive-pattern-avoiding stacks". Advances in Applied Mathematics 128 (lipiec 2021): 102192. http://dx.doi.org/10.1016/j.aam.2021.102192.
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Areephong, Jetsuda, Edvinas Orentas, Naomi Sakai i Stefan Matile. "Directional stack exchange along oriented oligothiophene stacks". Chemical Communications 48, nr 86 (2012): 10618. http://dx.doi.org/10.1039/c2cc35773a.
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Dronen, Blake, Aric Shorey, B. K. Wang i Leon Tsai. "Production Proven, High Precision Temporary Bond/De-bond Process". International Symposium on Microelectronics 2013, nr 1 (1.01.2013): 000861–65. http://dx.doi.org/10.4071/isom-2013-thp35.
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Wafer thinning represents a critical step in 2.5D and 3D-IC integration. Achieving low total thickness variation (TTV) of a bonded stack is essential since it directly impacts the TTV of the thinned device wafer. It is essential to understand and utilize appropriate processes and materials that provide precision bonded stacks prior to thinning operations in order to achieve high process yields. The 3M™ Wafer Support System and Corning's precision glass carrier wafers were used to produce bonded stacks. Leveraging metrology tools like the Flatmaster MSP-300 and low coherence interferometric probes allow for characterization of the TTV of each layer of a bonded stack and better understanding of the stack-up as well as how to minimize stack TTV. The ability to deliver stack TTV of < 2 um in a repeatable manner has been demonstrated.
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Ma, Zhiwen, Ramki Venkataraman i Mohammad Farooque. "Study of the Gas Flow Distribution and Heat Transfer for Externally Manifolded Fuel Cell Stack Module Using Computational Fluid Dynamics Method". Journal of Fuel Cell Science and Technology 1, nr 1 (28.06.2004): 49–55. http://dx.doi.org/10.1115/1.1794155.
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Uniform gas flow distribution in a fuel cell system is desired to attain maximum power operation potential. Two types of manifold systems are often used in fuel cell stacks; they are internal manifold system and external manifold system. This paper presents the modeling approach using the Computational Fluid Dynamics (CFD) method in analyzing fluid flow and heat transfer for the external manifold fuel cell stacks and stack module design. Computational models based on a Megawatt carbonate fuel cell stack module have been developed for investigating the fuel and oxidant flow distributions through the external manifold systems. This paper presents the modeling approaches and flow and temperature distribution results for externally manifolded fuel cell stack and stack module.
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Calderón, Antonio José, Francisco José Vivas, Francisca Segura i José Manuel Andújar. "Integration of a Multi-Stack Fuel Cell System in Microgrids: A Solution Based on Model Predictive Control". Energies 13, nr 18 (19.09.2020): 4924. http://dx.doi.org/10.3390/en13184924.
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This paper proposes a multi-objective model predictive control (MPC) designed for the power management of a multi-stack fuel cell (FC) system integrated into a renewable sources-based microgrid. The main advantage of MPC is the fact that it allows the current timeslot to be optimized while taking future timeslots into account. The multi-objective function solves the problem related to the power dispatch at time that includes criteria to reduce the multi-stack FC degradation, operating and maintenance costs, as well as hydrogen consumption. Regarding the scientific literature, the novelty of this paper lies in the proposal of a generalized MPC controller for a multi-stack FC that can be used independently of the number of stacks that make it up. Although all the stacks that make up the modular FC system are identical, their levels of degradation, in general, will not be. Thus, over time, each stack can present a different behavior. Therefore, the power control strategy cannot be based on an equal distribution according to the nominal power of each stack. On the contrary, the control algorithm should take advantage of the characteristics of the multi-stack FC concept, distributing operation across all the stacks regarding their capacity to produce power/energy, and optimizing the overall performance.
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Hou, Shuo, Xing Tan, Jincheng He, Xi Deng, Chen Xi, Guangyao Lu i Huan He. "Dynamic similarity analysis for a piezo-electromechanical system". International Journal of Applied Electromagnetics and Mechanics 64, nr 1-4 (10.12.2020): 103–10. http://dx.doi.org/10.3233/jae-209312.
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Most research about using piezoelectric stacks to suppress vibration of mechanical structures didn’t involve the similarity problem for the piezoelectric stacks. The goal of this paper is to investigate the dynamic similarity between a prototype piezo stack and a scaled up or down piezo stack, whilst discussing the feasibility of predicting the vibration of prototype structure which use the piezoelectric stacks for vibration control. To illustrate this problem concisely, a single-DOF system consists of a proof mass and a piezo stack shunted with a series RL circuit is considered. Firstly, the governing equation of such piezo-electromechanical system in frequency domain is derived. Next the dynamic similarity of prototype and model stack is analyzed by similitude theory. After that the scaling laws are derived. Finally, a numerical simulation and relative error analysis are given to demonstrate the scaling laws.
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Atig, Mohamed Faouzi, Benedikt Bollig i Peter Habermehl. "Emptiness of Ordered Multi-Pushdown Automata is 2ETIME-Complete". International Journal of Foundations of Computer Science 28, nr 08 (grudzień 2017): 945–75. http://dx.doi.org/10.1142/s0129054117500332.
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We consider ordered multi-pushdown automata, a multi-stack extension of pushdown automata that comes with a constraint on stack operations: a pop can only be performed on the first non-empty stack (which implies that we assume a linear ordering on the collection of stacks). We show that the emptiness problem for multi-pushdown automata is 2ETIME-complete. Containment in 2ETIME is shown by translating an automaton into a grammar for which we can check if the generated language is empty. The lower bound is established by simulating the behavior of an alternating Turing machine working in exponential space. We also compare ordered multi-pushdown automata with the model of bounded-phase (visibly) multi-stack pushdown automata, which do not impose an ordering on stacks, but restrict the number of alternations of pop operations on different stacks.
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Suo, Chun Guang, Wen Bin Zhang i Shi Su. "Fabrication of Micro DMFC Stack Using MEMS Technology". Advanced Materials Research 690-693 (maj 2013): 985–88. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.985.
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This paper presents two kinds of direct methanol fuel cell (μDMFC) stack in planar array. The silicon-based DMFC stack is designed in a flip-flop configuration using MEMS technology, and the stainless steel stack is fabricated using stamping technology. Compared to stainless steel stack, the flip-flop silicon-based stack may reduce the connection space and lower the contact resistance between the membrane electrode assembly and the plates. The electrical characterization of this μDMFC stack was carried out by tests. The experimental results showed the prototype was able to generate an open-circuit voltage of 2.7V and a maximum power density of 2.2mW/cm2 at room temperature, demonstrating the feasibility of this new configuration. Application of μDMFC stacks as portable power sources were demonstrated using small electric devices powered by this stack.
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Miller, FC, ER Harper i BJ Macauley. "Field examination of temperature and oxygen relationships in mushroom composting stacks dash consideration of stack oxygenation based on utilisation and supply". Australian Journal of Experimental Agriculture 29, nr 5 (1989): 741. http://dx.doi.org/10.1071/ea9890741.
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Temperature and oxygen concentration in Phase I composting stacks were investigated in the field. that both determine and are consequences of biological Investigations focused on various physical factors activity. Data indicate that oxygen concentrations in Phase I stacks are affected by convection, gaseous diffusion and utilisation rates, but that these rates vary significantly spatially and temporally. When stack temperatures exceed 60�C, biological rates of activity, and therefore oxygen uptake, decrease, allowing oxygen to penetrate well into the centres of stacks. While natural convection is commonly used to explain stack oxygenation, this is an over simplification that does not adequately describe stack oxygen concentrations.
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Bhatti, Umar Nawaz, Salem Bashmal, Sikandar Khan i Rached Ben-Mansour. "Numerical Modeling and Performance Evaluation of Standing Wave Thermoacoustic Refrigerators with a Multi-Layered Stack". Energies 13, nr 17 (24.08.2020): 4360. http://dx.doi.org/10.3390/en13174360.
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Thermoacoustic refrigerators have huge potential to replace conventional refrigeration systems as an alternative clean refrigeration technology. These devices utilize conversion of acoustic power and heat energy to generate the desired cooling. The stack plays a pivotal role in the performance of Standing Wave Thermoacoustic Refrigerators (SWTARs), as the heat transfer takes place across it. Performance of stacks can be significantly improved by making an arrangement of different materials inside the stack, resulting in anisotropic thermal properties along the length. In the present numerical study, the effect of multi-layered stack on the refrigeration performance of a SWTAR has been evaluated in terms of temperature drop across the stack, acoustic power consumed and device Coefficient of Performance (COP). Two different aspects of multi-layered stack, namely, different material combinations and different lengths of stacked layers, have been investigated. The combinations of four stack materials and length ratios have been investigated. The numerical results showed that multi-layered stacks produce lower refrigeration temperatures, consume less energy and have higher COP value than their homogeneous counterparts. Among all the material combinations of multi-layered stack investigated, stacks composed of a material layer with low thermal conductivity at the ends, i.e., RVC, produced the best performance with an increase of 26.14% in temperature drop value, reduction in the acoustic power consumption by 4.55% and COP enhancement of 5.12%. The results also showed that, for a constant overall length, an increase in length of side stacked material layer results in an increase in values of both temperature drop and COP.
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Sharma, Harshit, Vaibhav Garg, Sakshi ., Pankhuri Kalra i Dr Manjot Kaur Bhatia. "Why MERN Stack?" International Journal for Research in Applied Science and Engineering Technology 10, nr 12 (31.12.2022): 521–27. http://dx.doi.org/10.22214/ijraset.2022.47927.
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Abstract: In the past, web development was primarily based on the LAMP stack (Linux, Apache, MySQL, PHP, or Perl) and Java-based applications (Java EE, Spring). However, these stacks are made up of different programming languages and can be difficult for a single developer to understand. Advances in web technology over the last few years have allowed developers to participate in both the front-end and back-end processes of web applications. The main goal of this thesis was to explore the basic components of the very popular MREN stack. The MERN stack, which stands for MongoDB, Express.js, React.js, and Node.js, allows developers to easily integrate web development in a single programming language called JavaScript.
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Zou, Changwei, Xudong Wang, Yaoqing Gao i Jingling Xue. "Buddy Stacks: Protecting Return Addresses with Efficient Thread-Local Storage and Runtime Re-Randomization". ACM Transactions on Software Engineering and Methodology 31, nr 2 (30.04.2022): 1–37. http://dx.doi.org/10.1145/3494516.
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Shadow stacks play an important role in protecting return addresses to mitigate ROP attacks. Parallel shadow stacks, which shadow the call stack of each thread at the same constant offset for all threads, are known not to support multi-threading well. On the other hand, compact shadow stacks must maintain a separate shadow stack pointer in thread-local storage (TLS) , which can be implemented in terms of a register or the per-thread Thread-Control-Block (TCB) , suffering from poor compatibility in the former or high performance overhead in the latter. In addition, shadow stacks are vulnerable to information disclosure attacks. In this paper, we propose to mitigate ROP attacks for single- and multi-threaded server programs running on general-purpose computing systems by using a novel stack layout, called a buddy stack (referred to as Bustk ), that is highly performant, compatible with existing code, and provides meaningful security. These goals are met due to three novel design aspects in Bustk . First, Bustk places a parallel shadow stack just below a thread’s call stack (as each other’s buddies allocated together), avoiding the need to maintain a separate shadow stack pointer and making it now well-suited for multi-threading. Second, Bustk uses an efficient stack-based thread-local storage mechanism, denoted STK-TLS , to store thread-specific metadata in two TLS sections just below the shadow stack in dual redundancy (as each other’s buddies), so that both can be accessed and updated in a lightweight manner from the call stack pointer rsp alone. Finally, Bustk re-randomizes continuously (on the order of milliseconds) the return addresses on the shadow stack by using a new microsecond-level runtime re-randomization technique, denoted STK-MSR . This mechanism aims to obsolete leaked information, making it extremely unlikely for the attacker to hijack return addresses, particularly against a server program that sits often tens of milliseconds away from the attacker. Our evaluation using web servers, Nginx and Apache Httpd , shows that Bustk works well in terms of performance, compatibility, and security provided, with its parallel shadow stacks incurring acceptable memory overhead for real-world applications and its STK-TLS mechanism costing only two pages per thread. In particular, Bustk can protect the Nginx and Apache servers with an adaptive 1-ms re-randomization policy (without observable overheads when IO is intensive, with about 17,000 requests per second). In addition, we have also evaluated Bustk using other non-server applications, Firefox , Python , LLVM , JDK and SPEC CPU2006 , to demonstrate further the same degree of performance and compatibility provided, but the protection provided for, say, browsers, is weaker (since network-access delays can no longer be assumed).
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Degefa, Tolera G., Andrzej Wróbel i Marek Płaczek. "Modelling and Study of the Effect of Geometrical Parameters of Piezoelectric Plate and Stack". Applied Sciences 11, nr 24 (14.12.2021): 11872. http://dx.doi.org/10.3390/app112411872.
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The piezoelectric stack is employed as an actuator and a sensor in a variety of technical applications. The dynamic modelling of piezoelectric plates and stack is used to investigate and search for new applications in mechatronics systems that are based on various loading frequencies. Stacks are composed of series of the same size and whose plates feature the same material properties and are layered by dielectric sheets. This enables increased displacements to be achieved while freeing up more space. The major aim of this study was to investigate the feasibility of using differently modulated piezoelectric plates in a single stack. Mathematical modelling and the study of the characteristics of piezoelectric plates, as well as the stack, with respect to various geometrical parameters, enhances the utilization of the plate in mechatronics systems. The work focuses on the ability of piezoelectric stacks to generate complex vibration spectra comprising numerous frequencies. This is accomplished by utilizing different piezoelectric plates in the stack or by stimulating each plate with a distinct carrier frequency. The plate responses at a wide frequency of piezoelectric plates were investigated using several modeling environments and, finally, experimental findings were obtained. In addition to generating the hypothesis of triggering the plate in a single stack with a varied frequency spectrum, the experiment performed was employed for parameter identification. The experiment demonstrated that it is possible to increase the flexibility of systems by employing piezoelectric stacks as a mode of actuation and that piezo stacks can be used in systems that require precise actuation over a wide frequency range.
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Kajurek, Jakub, i Artur Rusowicz. "Experimental Investigation on the Thermoacoustic Effect in Easily Accessible Porous Materials". Energies 14, nr 1 (25.12.2020): 83. http://dx.doi.org/10.3390/en14010083.
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Thermoacoustic devices are the systems which use acoustic power to transport heat through a stack in a resonance tube. The stack is one of the most important parts of the thermoacoustic systems. It can have different geometries, like parallel plates, circular pores, or pin arrays. However, the fabrication of stacks with regular geometries is sometimes impractical due to material and assembly costs. These problems can be solved by using stack fabricated with random and easily accessible porous materials. In this paper an experimental investigation on the thermoacoustic effect in easily accessible porous materials is presented. The measurements with the stacks were made in a standing wave device filled with air at atmospheric pressure. The reported results confirm that some of the materials with high porosity can be an alternative to a traditional stack geometries and materials.
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Smolana, Mateusz, i Krzysztof Gromysz. "Effect of Eccentricity of Applied Force and Geometrical Imperfections on Stiffness of Stack of Cuboidal Steel Elements". Materials 13, nr 14 (16.07.2020): 3174. http://dx.doi.org/10.3390/ma13143174.
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Experimental tests were performed on a stack of cuboidal steel elements and its mathematical model was developed. Each cuboidal element was made of rolled profiles. Such stacks are the part of temporary supports that can be used to eliminate deflections of buildings. Stacks were loaded eccentrically through the inaccurate position of a jack. Moreover, two types of geometrical imperfections could be noticed. They included inaccurate contact between the stack elements and initial relative displacements of profiles that formed cuboidal elements. A mathematical model was developed to describe deformations of the stack and its parameters were determined by analysing test results. The eccentricity of the applied force had a slight impact on the stack stiffness, which was considerably reduced by geometrical imperfections. The imperfection covering initial relative displacements of rolled profiles inside cuboidal elements had the greatest impact on the stiffness. It could cause even a 10-fold drop in the stack stiffness when compared with the theoretical stiffness resulting from the stiffness of the stack section, and the stiffness dropped by ca. 3.5 times when the imperfection included the inaccurate contact between the cuboidal elements. Finally, the occurrence of both types of geometrical imperfections generated the real stiffness more than ten times lower than the theoretical stiffness that did not take into account imperfections.
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Tsviatkou, V. Yu. "LIFO-STACK SIZE DETERMINATION FOR GROWING OF THE IMAGE REGIONS". Doklady BGUIR 18, nr 2 (31.03.2020): 45–52. http://dx.doi.org/10.35596/1729-7648-2020-18-2-45-52.
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This paper considers the problem of memory allocation for the organization of the LIFO-stack in the algorithm for image segmentation based on growing regions is considered. Segmentation divides the image into regions with identical or similar properties and is the most demanding process for the capacity of RAM. The cultivation of areas begins with the neighborhoods of pre-selected initial growth pixels and uses stacks to store the coordinates of adjacent pixels attached to the cultivated region. Stack loading is maximized when the segment size matches the size of the YX image. In the absence of an expression for the exact determination of the size of the stack, it is possible to guarantee the stable operation of the algorithm for growing regions, eliminating the overflow of the memory allocated for processing if the stack size is assumed equal to YX. However, this approach does not take into account the fact that filling the coordinate stacks is also accompanied by a selection of them, which makesthe stack size always smaller than YX. The article proposes an expression that allows one to increase the accuracy of determining the required size of the LIFO-stack for storing the coordinates of adjacent pixels depending on the image size. The expression takes into account the conditions of the maximum load of the LIFO-stack when: a) the segmentation of the square region with the initial growth pixel in the corner of this region is carried out; b) in the scan window, adjacent pixels are always selected in order with the first selectable pixel located in the corner of the scan window. Using the proposed expression to calculate the required capacity of the LIFO-stack under conditions of its maximum load in the image segmentation algorithm based on growing regions provides a 2-fold reduction in the number of LIFO-stack memory cells.
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Linderoth, Søren, Peter Halvor Larsen, M. Mogensen, Peter V. Hendriksen, N. Christiansen i H. Holm-Larsen. "Solid Oxide Fuel Cell (SOFC) Development in Denmark". Materials Science Forum 539-543 (marzec 2007): 1309–14. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.1309.
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The SOFC technology under development at Risø National Laboratory (RISØ) and Topsoe Fuel Cell A/S (TOFC) is based on an integrated approach ranging from basic materials research on single component level over development of cell and stack manufacturing technology to system studies and modelling. The effort also comprises an extensive cell and stack testing program. Systems design, development and test is pursued by TOFC in collaboration with various partners. The standard cells are thin and robust with dimensions of 12 x 12 cm2 and cell stacks are based on internal manifolding. Production of cells is being up-scaled continuously. The durability of the standard stack design with standard cells has been tested for more than 13000 hours including nine full thermal cycles with an overall voltage degradation rate of about 1% per 1000 hours. Recently, the degradation rate has been significantly reduced by introduction of improved stack component materials. 75-cell stacks in the 1+ kW power range have been tested successfully. Stacks have been delivered in a pre-reduced state to partners and tested successfully in test systems with natural gas as fuel. The consortium of TOFC and RISØ has an extended program to develop the SOFC technology all the way to a marketable product. Stack and system modelling including cost optimisation analysis is used to develop multi kW stack modules for operation in the temperature range 700-850oC. To ensure the emergence of cost-competitive solutions, a special effort is focused on larger anode-supported cells as well as a new generation of SOFCs based on porous metal supports and new electrode and electrolyte materials. The SOFC program comprises development of next generation of cells and multi stack modules for operation at lower temperature with increased durability and mechanical robustness in order to ensure long-term competitiveness.
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Treumann, David. "Stacks similar to the stack of perverse sheaves". Transactions of the American Mathematical Society 362, nr 10 (1.10.2010): 5395. http://dx.doi.org/10.1090/s0002-9947-2010-04958-x.
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Joyce, D. "MOTIVIC INVARIANTS OF ARTIN STACKS AND 'STACK FUNCTIONS'". Quarterly Journal of Mathematics 58, nr 3 (29.05.2007): 345–92. http://dx.doi.org/10.1093/qmath/ham019.
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Thorson, Jeffrey R., i Jon F. Claerbout. "Velocity‐stack and slant‐stack stochastic inversion". GEOPHYSICS 50, nr 12 (grudzień 1985): 2727–41. http://dx.doi.org/10.1190/1.1441893.
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Normal moveout (NMO) and stacking, an important step in analysis of reflection seismic data, involves summation of seismic data over paths represented by a family of hyperbolic curves. This summation process is a linear transformation and maps the data into what might be called a velocity space: a two‐dimensional set of points indexed by time and velocity. Examination of data in velocity space is used for analysis of subsurface velocities and filtering of undesired coherent events (e.g., multiples), but the filtering step is useful only if an approximate inverse to the NMO and stack operation is available. One way to effect velocity filtering is to use the operator [Formula: see text] (defined as NMO and stacking) and its adjoint L as a transform pair, but this leads to unacceptable filtered output. Designing a better estimated inverse to L than [Formula: see text] is a generalization of the inversion problem of computerized tomography: deconvolving out the point‐spread function after back projection. The inversion process is complicated by missing data, because surface seismic data are recorded only within a finite spatial aperture on the Earth’s surface. Our approach to solving the problem of an ill‐conditioned or nonunique inverse [Formula: see text], brought on by missing data, is to design a stochastic inverse to L. Starting from a maximum a posteriori (MAP) estimator, a system of equations can be set up in which a priori information is incorporated into a sparseness measure: the output of the stochastic inverse is forced to be locally focused, in order to obtain the best possible resolution in velocity space. The size of the resulting nonlinear system of equations is immense, but using a few iterations with a gradient descent algorithm is adequate to obtain a reasonable solution. This theory may also be applied to other large, sparse linear operators. The stochastic inverse of the slant‐stack operator (a particular form of the Radon transform), can be developed in a parallel manner, and will yield an accurate slant‐stack inverse pair.
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Salleh, Khairol Amin Mohd, Abdul Rahim Ahmad i Roslan Ismail. "Preventing Stack Overflow Using Alternative Stack Approaches". International Journal of Engineering & Technology 7, nr 4.35 (30.11.2018): 239. http://dx.doi.org/10.14419/ijet.v7i4.35.22739.
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Buffer overflow marks a phenomenon of a malicious technique employed by attackers, as reported in the NIST statistics. This paper presents a method of implementing a dual stack approach using software to protect the data stack from experiencing the attack by using 3 types of architecture, ranging from parallel program, multi-threading to a simple sequential subroutine. The current research on dual stack may require new hardware or a modified version of compiler which may complicate the implementation. These implementations spark some major issues in code backward compatibility with some changes in the language semantics especially in handling the movement of data to and from the dual stack. This paper discusses the implementation of Alternative Stack prototypes in 3 types of architecture and observation on its behavior during the performance and security test. The test has been benchmarked against the programs that are compiled with Microsoft Security Cookie. The Alternative Stack Architecture 3 prototype displayed a significant performance against the benchmarked programs whilst maintaining the confidentiality, integrity and availability of the programs.
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Brysk, Henry, i Douglas W. McCowan. "A slant‐stack procedure for point‐source data". GEOPHYSICS 51, nr 7 (lipiec 1986): 1370–86. http://dx.doi.org/10.1190/1.1442187.
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The proper implementation of the τ-p method for surface data excited by a point source requires a cylindrical slant stack. Usually the common (Cartesian) slant stack is computed instead as an approximation to the geometrically correct procedure. Here we describe a formulation of the cylindrical slant stack as a weighted sum of Cartesian slant stacks; our cylindrical slant stack is computationally efficient to perform. We show how, although the usefulness of the slant stack is most easily seen with Cartesian coordinates, it can also be used with Fourier‐Bessel transforms. An example of the method shows results computed from data recorded on the West Florida Shelf. Severe edge‐effect noise which overwhelms the Cartesian slant stack is attenuated by the cylindrical slant‐stacking. Applications of the cylindrical slant stack to other seismological calculations, such as Lamb’s problem, are also discussed. In particular, we prove that the plane‐wave reflection coefficients apply exactly in the τ-p domain; hence an amplitude‐versus‐offset analysis is unambiguous in that domain.
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Simon Araya, Samuel, Sobi Thomas, Andrej Lotrič, Simon Lennart Sahlin, Vincenzo Liso i Søren Juhl Andreasen. "Effects of Impurities on Pre-Doped and Post-Doped Membranes for High Temperature PEM Fuel Cell Stacks". Energies 14, nr 11 (21.05.2021): 2994. http://dx.doi.org/10.3390/en14112994.
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In this paper, we experimentally investigated two high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) stacks for their response to the presence of reformate impurities in an anode gas stream. The investigation was aimed at characterizing the effects of reformate impurities at the stack level, including in humidified conditions and identifying fault features for diagnosis purposes. Two HT-PEMFC stacks of 37 cells each with active areas of 165 cm2 were used with one stack containing a pre-doped membrane with a woven gas diffusion layer (GDL) and the other containing a post-doped membrane with non-woven GDL. Polarization curves and galvanostatic electrochemical impedance spectroscopy (EIS) were used for characterization. We found that both N2 dilution and impurities in the anode feed affected mainly the charge transfer losses, especially on the anode side. We also found that humidification alleviated the poisoning effects of the impurities in the stack with pre-doped membrane electrode assemblies (MEA) and woven GDL but had detrimental effects on the stack with post-doped MEAs and non-woven GDL. We demonstrated that pure and dry hydrogen operation at the end of the tests resulted in significant recovery of the performance losses due to impurities for both stacks even after the humidified reformate operation. This implies that there was only limited acid loss during the test period of around 150 h for each stack.
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Kumar, M. Arul, Sivasambu Mahesh i P. Venkitanarayanan. "A Rate-Independent 'Stack' Model of a Polycrystalline Aggregate". Materials Science Forum 702-703 (grudzień 2011): 192–95. http://dx.doi.org/10.4028/www.scientific.net/msf.702-703.192.
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The 'stack' model of a rate-independent rigid-plastic polycrystalline material is developed. In the 'stack' model, stacks of N neighboring sub-grain domains collectively accommodate the imposed macroscopic deformation while enforcing the velocity and traction continuity condition with its neighbors. The developed 'stack' model is applied to simulate the two-dimensional polycrystalline aggregate under macroscopically imposed plane-strain tension. The effect of inter- and intra-grain interactions on qualitative and quantitative variations in the predicted macroscopic stress-strain response and texture evolution are presented. The diminishing trend of constraint on individual sub-grain domains and texturing rate with stack size N, and saturation for large N also given.
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Kraft, Juergen, Michael T. Y. Paul i Michael Goetz. "(Invited) Automated Production of High Performance PEMFC Stacks and Components According to Automotive Requirements". ECS Meeting Abstracts MA2022-02, nr 45 (9.10.2022): 1693. http://dx.doi.org/10.1149/ma2022-02451693mtgabs.
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EKPO Fuel Cell GmbH was founded in 2021 by two parent companies, ElringKlinger and Plastic Omnium, whom both are strong and established automotive suppliers with mass manufacturing capabilities and strategic approaches to hydrogen and the fuel cell businesses. The aim of EKPO is the development and production of proton exchange membrane fuel cell stack components and stack modules. Drawing from the experiences of the pilot automated production line since 2016, a fully optimized automated production, with improved production technologies and products, was developed by EKPO in 2021 to achieve an output capability of 10,000 stacks per year. The line was designed with a modular and scalable approach that allows flexibility as well as increased capacity by parallelization. The implementation is successful of producing EKPO’s various stack platforms while maintaining a high level of quality and production standard for the automotive industry. Since EKPO offers a wide range of products, the automated line can cover stack power ranges from 10 kW up to > 200 kW. As a prerequisite for excellent technical performance, in addition to function quality measures were set as key targets from the start of the development. EKPO has thus established consistent and stringent quality process flows and processes for all production steps. These measures include the early involvement of measurability and manufacturability assessment on all process and analysis steps on the different levels (i.e., components and stack). The feedback from each workflow can then continuously improve products, processes, and documentation regarding product specific codes standards and regulations (CSR). The accumulative knowledge from two decades of activity of fuel cell component and stack development enabled EKPO to establish a production range starting from cell and stack components (i.e., bipolar plates, sealings, and plastic end plate modules) to fuel cell stacks and modules produced by fully automated MEA and stack assembly and end-of-line testing. The automated production covers all processes from bipolar plate manufacturing and assembly, CCM and GDL roll good cutting, MEA-assembly, stacking, and the final compression and characterization of the fuel cell stack. The quality matrixes include inspecting performance key figures as well as quality and geometries of the stack and its components. The incoming materials are typically supplied as roll goods, (i.e., GDL, CCM, and metal coil) or as raw material (i.e., plastic granules). As the incoming materials and finished components are very sensitive to environmental conditions and particle contamination, the entire MEA processing and stack assembly process takes place in a cleanroom with controlled climate for maximum process stability and reliability. With a key approach of “design to manufacture” and deep understanding of stack technology and component requirements, EKPO is able to deliver two best in class stacks, namely the NM5 evo and NM12 single and twin platforms.
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Shentu, Junchao, i Dong Wang. "Notes on algebraic log stack". International Journal of Mathematics 27, nr 10 (wrzesień 2016): 1650081. http://dx.doi.org/10.1142/s0129167x16500816.
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Let [Formula: see text] be a stack over the category of fine log schemes. If [Formula: see text] has a representable fppf covering, then, it has enough compatible minimal objects. As a consequence, we prove the equivalence between two notions of log moduli stacks which appear in literatures. Also, we obtain several fundamental results of algebraic log stacks.
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Smara, Anis, Thomas Reis, Vicente Climente-Alarcon i Bartek A. Glowacki. "Magnetization reduction by varying normal field in stacks of composite superconductors in an electrical motor". European Physical Journal Applied Physics 92, nr 2 (listopad 2020): 20902. http://dx.doi.org/10.1051/epjap/2020200034.
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Trapped field magnets of superconducting stacks could be an alternative to conventional magnets in electrical machine applications. A conceptual design of an electrical motor using these stacks was proposed in [1,2]. Superconducting stacks offer many advantages; however, they can be demagnetized when exposed to the varying field present in electrical motors during operation. This varying field can be generated by salient magnetic circuit or generated from the armature winding as harmonics. To study this demagnetization effect, we carried out an experiment on a superconducting stack in an electrical machine, exposing it to different levels of varying cross and normal fields. The experimental measurements recorded a demagnetization of the stack. In this work, the analyses of the reduction of magnetization of the superconducting stack by an alternating normal field and the comparison of the results with experimental measurements in the electrical motor are presented.
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Dudek, Magdalena, Bartłomiej Lis, Andrzej Raźniak, Mariusz Krauz i Michał Kawalec. "Selected Aspects of Designing Modular PEMFC Stacks as Power Sources for Unmanned Aerial Vehicles". Applied Sciences 11, nr 2 (12.01.2021): 675. http://dx.doi.org/10.3390/app11020675.
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Two types of air-cooled modular polymer membrane fuel cells (PEMFC) stacks with full equipment were constructed and investigated as components of hybrid power sources. The first, a 2-kW PEMFC stack, was assembled from two 1-kW PEMFC modules electrically connected in parallel and compared with a commercial PEMFC stack built from one 2-kW PEMFC module. The second, a 500-W PEMFC stack, was assembled with three modules connected in parallel. It was found that the two-module PEMFC stack was capable of operation with nominal power of 2 kW. Analysis of the distribution of the air cooling system in both modules was also conducted. The two-module PEMFC stack reduced hydrogen consumption compared to the reference 2-kW PEMFC stack consisting of only one module. The elaborated two-module PEMFC stack was successfully tested in a propulsion system designed to supply an electrical engine with a propeller. The electrical performance of the three-module PEMFC stack was tested separately as well as in a hybrid system in connection with a 5 s Li-Pol battery. It was found that the elaborated PEMFC stack was capable of operation with nominal power of 500 W and variable rapid dynamic electrical loads. It was also successfully tested as a power source to supply servomechanisms and other auxiliary devices.
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Xu, Yu, Anton Kukolin, Daifen Chen i Wei Yang. "Multiphysics Field Distribution Characteristics within the One-Cell Solid Oxide Fuel Cell Stack with Typical Interdigitated Flow Channels". Applied Sciences 9, nr 6 (20.03.2019): 1190. http://dx.doi.org/10.3390/app9061190.
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Generally, the manufacturing technology of fuel cell units is considered to satisfy the current commercialization requirements. However, achieving a high-performance and durable stack design is still an obstacle in its commercialization. The solid oxide fuel cell (SOFC) stack is considered to have performance characteristics that are distinct from the proton exchange membrane fuel cell (PEMFC) stacks. Within the SOFC stack, vapor is produced on the anode side instead of the cathode side and high flow resistance within the fuel flow path is recommended. In this paper, a 3D multiphysics model for a one-cell SOFC stack with the interdigitated channels for fuel flow path and conventional paralleled line-type rib channels for air flow path is firstly developed to predict the multiphysics distribution details. The model consists of all the stack components and couples well the momentum, species, and energy conservation and the quasi-electrochemical equations. Through the developed model, we can get the working details within those SOFC stacks with the above interdigitated flow channel features, such as the fuel and air flow feeding qualities over the electrode surface, hydrogen and oxygen concentration distributions within the porous electrodes, temperature gradient distribution characteristics, and so on. The simulated result shows that the multiphysics field distribution characteristics within the SOFC and PEMFC stacks with interdigitated flow channels feature could be very different. The SOFC stack using the paralleled line-type rib channels for air flow path and adopting the interdigitated flow channels for the fuel flow path can be expected to have good collaborative performances in the multiphysics field. This design would have good potential application after being experimentally confirmed.
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Xiang, Yi, i Yanzhuang Wang. "GRASP55 and GRASP65 play complementary and essential roles in Golgi cisternal stacking". Journal of Cell Biology 188, nr 2 (18.01.2010): 237–51. http://dx.doi.org/10.1083/jcb.200907132.
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In vitro studies have suggested that Golgi stack formation involves two homologous peripheral Golgi proteins, GRASP65 and GRASP55, which localize to the cis and medial-trans cisternae, respectively. However, no mechanism has been provided on how these two GRASP proteins work together to stack Golgi cisternae. Here, we show that depletion of either GRASP55 or GRASP65 by siRNA reduces the number of cisternae per Golgi stack, whereas simultaneous knockdown of both GRASP proteins leads to disassembly of the entire stack. GRASP55 stacks Golgi membranes by forming oligomers through its N-terminal GRASP domain. This process is regulated by phosphorylation within the C-terminal serine/proline-rich domain. Expression of nonphosphorylatable GRASP55 mutants enhances Golgi stacking in interphase cells and inhibits Golgi disassembly during mitosis. These results demonstrate that GRASP55 and GRASP65 stack mammalian Golgi cisternae via a common mechanism.
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Naik, Megavath Venkatesh, i Paulson Samuel. "Analytical Comparision between Single and Modular Fuel Cell Stack: Uniform Modular Cell Approch". International Journal of Advances in Applied Sciences 6, nr 2 (1.06.2017): 89. http://dx.doi.org/10.11591/ijaas.v6.i2.pp89-97.
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A single fuel cell (FC) produces a very small voltage of about 0.6 -0.8 V under normal operating condition, and hence several individual cells are connected in series as a stack to get higher voltages suitable for practical loads. The stacks are then connected in series to get required values of DC voltage. The FC performance varies with the operating parameters such as temperature, humidity, fuel flow rate, ageing and fuel non uniform concentration. The FC stack underperforms when there is presence of bad cell in it. The Presence bad cell in a stack limits the current handling capacity of other healthy cells when it’s connected as a conventional single stack. This can be overcome by connecting the fuel cells in uniform modular cell configuration. In this paper a Uniform Modular Cell Configuration (UMCC) is proposed to gain the maximum power from the stack and the conventional Single or Uni Stack Configuration (USC) is compared with the proposed structure. A detail mathematical analysis of comparing both methods is described. Further the superiority of the proposed method is proven by carrirying out the simulations under steady state operating condition of a FC stack feeding to a constant current load.
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ALDROVANDI, ETTORE, i A. EMIN TATAR. "Notes on weak units of group-like 1- and 2-stacks". Mathematical Proceedings of the Cambridge Philosophical Society 164, nr 2 (9.11.2016): 205–20. http://dx.doi.org/10.1017/s0305004116000931.
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AbstractThe weak units of strict monoidal 1- and 2-categories are defined respectively in [15] and [14]. In this paper, we define them for group-like 1- and 2-stacks. We show that they form a contractible Picard 1- and 2-stack, respectively. We give their cohomological description which provides for these stacks a representation by complexes of sheaves of groups. Later, we extend the discussion to the monoidal case. We consider the (2-)substack of cancelable objects of a monoidal 1-(2-)stack. We observe that this (2-)substack is trivially group-like, its weak units are the same as the weak units of the monoidal 1-(2-)stack, and therefore we can recover the contractibility results in [15] and [14] by analysing it.
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de Haart, Ute, Felix Kunz i Rüdiger-A. Eichel. "Investigation of the Stability of SOC Stacks By Thermo Cycles". ECS Meeting Abstracts MA2022-02, nr 50 (9.10.2022): 2552. http://dx.doi.org/10.1149/ma2022-02502552mtgabs.
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In recent years different research institutes and companies have developed anode supported cells (ASCs) with an LSC ((La,Sr)CoO3δ) oxygen electrode for solid oxide cells (SOCs), which showed an improved performance in comparison to ASCs with an LSCF electrode. Until now, the SOC-stacks by Forschungszentrum Jülich GmbH (FZJ) used ASCs with LSCF on the oxygen side. To minimize undesired effects which might occur due to the inter-diffusion of the constituting cations between adjacent layers, the contact layer on the oxygen side was made of the same LSCF composition. One mayor concern accompanying the use of LSC layers in ASCs and stacks is the thermal expansion coefficient (TEC) of the LSC material, which is almost a factor two higher than the TECs of the other materials of the cells and in the stacks (La0.6Sr0.4CoO3: 20.5·10-6 K-1 [1], La0.6Sr0.4Co0.2Fe0.8O3: 17.5·10-6 K1 [1], 8mol% Y2O3 stabilized ZrO2 (8YSZ): 9.3·10-6 K-1 [2], 30vol% Ni – YSZ cermet: 11.6·10-6 K-1 [3], CroFer 22 APU: 11.6·10-6 K-1 [4]). This large difference may lead to cracking in the layers or in the worst case to delamination between the layers. To meet this concern and demonstrate the stability and robustness of ASCs with LSC on the oxygen side of SOC-stacks performance tests were done with three F-10 stacks by FZJ, each consisting of four repetitive units (RU). The first stack (stack#1) used ASCs with LSCF as electrode and contact layer on the oxygen side and was taken as reference. Then, replacing LSCF by LSC was performed step wise. First only the cells with LSCF were replaced by cells with LSC, leaving all other components of the stack the same, including the LSCF contact layer on the oxygen side (stack#2). In the second step also the contact layer on the oxygen side was manufactured from the same LSC composition (stack#3). Thereby, commercially available cells were used resulting in additional differences between stack#1 (30 µm oxygen electrode, 5 µm oxygen barrier, 10 µm electrolyte, 7 µm fuel electrode and 300 µm fuel electrode support layer) and stack#2 as well as stack#3 (30 µm oxygen electrode, 2 µm oxygen barrier, 3 µm electrolyte, 10 µm fuel electrode and 400 µm fuel electrode support layer). Each stack was characterized in fuel cell mode and investigated by thermo cycles. The performance enhancement of stack#2 due to the introduction of LSC electrodes can be reported. At an operating temperature of 700 °C with 20% humidified hydrogen as fuel, current densities well over 1.2 A/cm² could be obtained at a cell voltage of 700 mV. This is a substantial increase in performance compared to the reference stack, stack#1, with LSCF electrodes on the oxygen side for which only 0.7 A/cm² at 700 mV could be reached. An initial analysis of impedance spectra recorded showed that this improvement could be attributed a lower ohmic resistance, mainly due to the thinner electrolyte layer, and a lower polarization contribution of the ASCs with LSC electrode. After this initial characterization all three stacks were subjected to thermo cycles from the operating temperature of 700 °C down to 200 °C and backwards. After 21 initial thermo cycles both, stack#2 and stack#3 were subjected to even more severe thermo cycles down to below 100 °C and back to 700 °C. From OCV, IV and EIS measurements during each cycle the stability of all three stacks could be shown for up to 50 thermo cycles with voltage losses from 0.2 to 0.5 mV/cycle despite the introduction of LSC layers in two of these stacks. Compared to ASCs with LSCF electrodes on the oxygen side an enhancement in performance was achieved by using ASCs with LSC electrodes and LSC contact layers on the oxygen side in the FZJ F10-design. Also, the stability of performance was demonstrated for up to 50 thermo cycles despite the higher TEC of LSC compared to the other stack materials. References [1] H. Ullmann, N. Trofimenko, F. Tietz, D. Stöver, A. Ahmad-Khanlou, Correlation between thermal expansion and oxide ion transport in mixed conducting perovskite-type oxides for SOFC cathodes, Solid State Ionics 138(1) (2000) 79 – 90 [2] H. Hayashi, T. Saitou, N. Maruyama, H. Inaba, K. Kawamura, M. Mori, Thermal expansion coefficient of yttria stabilized zirconia for various yttria contents, Solid State Ionics 176(5 – 6) (2005) 613 – 619 [3] S. T. Aruna, M. Muthuraman, K. C. Patil, Synthesis and properties of Ni-YSZ cermet: anode material for solid oxide fuel cells, Solid State Ionics 111(1 – 2) (1998) 45 – 51 [4] VDM® Crofer 22 APU Datasheet: https://www.vdm-metals.com/fileadmin/user_upload/Downloads/ Data_Sheets/Data_Sheet_VDM_Crofer_22_APU.pdf Figure 1
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Kruusenberg, Ivar, Kush Chadha i Taarini Atal. "High Power Density Fuel Cell Systems for Portable Electric Generators". ECS Meeting Abstracts MA2022-01, nr 26 (7.07.2022): 1234. http://dx.doi.org/10.1149/ma2022-01261234mtgabs.
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It is of utmost importance to develop light weight fuel cell stacks and find the ways to integrate these to light weight and low temperature fuel cell systems. In order to meet the future energy demands non-polluting, compact, transportation and portable applications are required. Current energy systems have lower power density (kW/kg) resulting in optimized power only at higher overall weight. Systems with higher power density demands higher initial setup costs. Low temperature PEMFC, on other hand offers various advantages but fails to provide the required output without exceeding the weight of the fuel cell stack and thereby fuel cell systems. A fuel cell system consists of a fuel cell stack, compressed gas in cylinder, pressure relief valves, regulators, water pump, sensors and cvm. A fuel cell stack is the main component consisting of one of the devices with maximum weight and cost contribution. In such case, developing a system with stack having higher power density reduces overall weight and increases power density (kW/kg). PowerUP Energy Technologies has developed light weight fuel cell stack to achieve higher power density. Experiments considering flow field designs, recirculation strategy, different anode configuration has been a subject of study. Dead-end anode, closed cathode configuration of fuel cell stack further improves fuel utilization. Recirculation line of hydrogen if further added can improve in overall fuel utilization. Counter flow arrangement for reactant distribution further removes the necessity of humidifying the gases. This result in removal of humidifiers and thereby reducing the weight of the fuel cell system in total. Portable fuel cell systems have flexibility for ease in transportation and stationery solutions. Furthermore, lighter fuel cell stacks add advantage for higher output power at lower overall weights. This stack developed is further optimized with improved flow field designs and design of manifold. These fuel cell stacks are used in PowerUP’s portable fuel cell electric generators that are more efficient and sustainable than the currently used fossil fuel based solutions.
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Borges, Renata Coura, Letícia Mombrini Marques, Cláudio Fernando Mahler i Alfredo Victor Bellido Bernedo. "Determination of the concentration of Ce, La, Sm and Eu in a phosphogypsum stack, in Imbituba city, Santa Catarina, Brazil". Eclética Química Journal 43, nr 3 (10.10.2018): 37. http://dx.doi.org/10.26850/1678-4618eqj.v43.3.2018.p37-44.
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Phosphate fertilizer industry produces phosphoric acid from phosphate rocks, and as a byproduct, it produces phosphogypsum, also known as agricultural gypsum. This material was stock an open-air stacks near the producing units. In order to determine levels of rare-earth elements in phosphogypsum stacks, located in Imbituba, Brazil. Samples of 1000 grams of phosphogypsum were collected in nine different points in stack 1. The concentration of rare-earth elements was determined through neutron activation analysis and results indicate significant values of rare earth elements in the phosphogypsum from Imbituba, when compared to the values of the Earth’s crust.
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Kan, Ankang, Jin Hu, Zhipeng Guo, Chuang Meng i Chen Chao. "Impact of Cargo Stacking Modes on Temperature Distribution Inside Marine Reefer Containers". International Journal of Air-Conditioning and Refrigeration 25, nr 03 (wrzesień 2017): 1750020. http://dx.doi.org/10.1142/s2010132517500201.
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The refrigerated/chilled quality of marine cargo is vitally influenced by the temperature distribution inside reefer container. The stacking mode is a key factor affecting temperature distribution. CFD method is employed to model and simulate a 20-ft standard reefer container, in which seven cargo stacking modes are emulated to numerically analyze the internal temperature distribution inside the container. The stacking cargo is assumed as solid stack without heat release and the variables, such as stack number, height, length and gap, are considered in seven simulation cases. The results show that the temperature distributions become disordered along with increase in the stack height; the temperature difference increase along with increase in the stack length; the temperature tends to be isothermal when the gap of the stacks or the space between the stack and sidewall surface is enlarging. The simulation results are in very good agreement with the experimental results.
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Jardine, J. F. "COSIMPLICIAL SPACES AND COCYCLES". Journal of the Institute of Mathematics of Jussieu 15, nr 3 (10.11.2014): 445–70. http://dx.doi.org/10.1017/s1474748014000358.
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Standard results from non-abelian cohomology theory specialize to a theory of torsors and stacks for cosimplicial groupoids. The space of global sections of the stack completion of a cosimplicial groupoid $G$ is weakly equivalent to the Bousfield–Kan total complex of $BG$ for all cosimplicial groupoids $G$. The $k$-invariants for the Postnikov tower of a cosimplicial space $X$ are naturally elements of stack cohomology for the stack associated to the fundamental groupoid ${\it\pi}(X)$ of $X$. Cocycle-theoretic ideas and techniques are used throughout the paper.
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Pulvertaft, Guy, i Robert Robins. "Graham Stack". Journal of Hand Surgery 12, nr 1 (luty 1987): 3. http://dx.doi.org/10.1016/0266-7681_87_90042-8.
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Wendt, P., E. Coyle i N. Gallagher. "Stack filters". IEEE Transactions on Acoustics, Speech, and Signal Processing 34, nr 4 (sierpień 1986): 898–911. http://dx.doi.org/10.1109/tassp.1986.1164871.
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Fournet, Cédric, i Andrew D. Gordon. "Stack inspection". ACM SIGPLAN Notices 37, nr 1 (styczeń 2002): 307–18. http://dx.doi.org/10.1145/565816.503301.
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Yantovski, E. I. "Stack downward". Energy Conversion and Management 37, nr 6-8 (czerwiec 1996): 867–77. http://dx.doi.org/10.1016/0196-8904(95)00270-7.
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