The Experts below are selected from a list of 21966 Experts worldwide ranked by ideXlab platform
Tianshou Zhao - One of the best experts on this subject based on the ideXlab platform.
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numerical investigations of effect of membrane electrode assembly structure on water crossover in a liquid feed direct methanol fuel cell
Journal of Power Sources, 2009Co-Authors: Weiwei Yang, Tianshou ZhaoAbstract:Abstract A two-phase mass-transport model is employed to investigate the water transport behaviour through the membrane electrode assembly (MEA) of a liquid-feed direct methanol fuel cell (DMFC). Emphasis is placed on examining the effects of each Constituent Component design of the MEA, including catalyst layers, microporous layers and membranes, on each of the three water crossover mechanisms: electro-osmotic drag, diffusion, and convection. The results show that lowering the diffusion flux of water or enhancing the convection flux of water (termed as the back-flow flux) through the membrane are both feasible to suppress water crossover in DMFCs. It is found that the reduction in the diffusion flux of water can be mainly achieved through optimum design of the anode porous layers, as the effect of the cathode porous region on water crossover by diffusion is relatively smaller. On the other hand, the design of the cathode porous layers plays a more important role in increasing the back-flow flux of water from the cathode to anode.
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numerical investigations of effect of membrane electrode assembly structure on water crossover in a liquid feed direct methanol fuel cell
Journal of Power Sources, 2009Co-Authors: Weiwei Yang, Tianshou ZhaoAbstract:Abstract A two-phase mass-transport model is employed to investigate the water transport behaviour through the membrane electrode assembly (MEA) of a liquid-feed direct methanol fuel cell (DMFC). Emphasis is placed on examining the effects of each Constituent Component design of the MEA, including catalyst layers, microporous layers and membranes, on each of the three water crossover mechanisms: electro-osmotic drag, diffusion, and convection. The results show that lowering the diffusion flux of water or enhancing the convection flux of water (termed as the back-flow flux) through the membrane are both feasible to suppress water crossover in DMFCs. It is found that the reduction in the diffusion flux of water can be mainly achieved through optimum design of the anode porous layers, as the effect of the cathode porous region on water crossover by diffusion is relatively smaller. On the other hand, the design of the cathode porous layers plays a more important role in increasing the back-flow flux of water from the cathode to anode.
Weiwei Yang - One of the best experts on this subject based on the ideXlab platform.
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numerical investigations of effect of membrane electrode assembly structure on water crossover in a liquid feed direct methanol fuel cell
Journal of Power Sources, 2009Co-Authors: Weiwei Yang, Tianshou ZhaoAbstract:Abstract A two-phase mass-transport model is employed to investigate the water transport behaviour through the membrane electrode assembly (MEA) of a liquid-feed direct methanol fuel cell (DMFC). Emphasis is placed on examining the effects of each Constituent Component design of the MEA, including catalyst layers, microporous layers and membranes, on each of the three water crossover mechanisms: electro-osmotic drag, diffusion, and convection. The results show that lowering the diffusion flux of water or enhancing the convection flux of water (termed as the back-flow flux) through the membrane are both feasible to suppress water crossover in DMFCs. It is found that the reduction in the diffusion flux of water can be mainly achieved through optimum design of the anode porous layers, as the effect of the cathode porous region on water crossover by diffusion is relatively smaller. On the other hand, the design of the cathode porous layers plays a more important role in increasing the back-flow flux of water from the cathode to anode.
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numerical investigations of effect of membrane electrode assembly structure on water crossover in a liquid feed direct methanol fuel cell
Journal of Power Sources, 2009Co-Authors: Weiwei Yang, Tianshou ZhaoAbstract:Abstract A two-phase mass-transport model is employed to investigate the water transport behaviour through the membrane electrode assembly (MEA) of a liquid-feed direct methanol fuel cell (DMFC). Emphasis is placed on examining the effects of each Constituent Component design of the MEA, including catalyst layers, microporous layers and membranes, on each of the three water crossover mechanisms: electro-osmotic drag, diffusion, and convection. The results show that lowering the diffusion flux of water or enhancing the convection flux of water (termed as the back-flow flux) through the membrane are both feasible to suppress water crossover in DMFCs. It is found that the reduction in the diffusion flux of water can be mainly achieved through optimum design of the anode porous layers, as the effect of the cathode porous region on water crossover by diffusion is relatively smaller. On the other hand, the design of the cathode porous layers plays a more important role in increasing the back-flow flux of water from the cathode to anode.
Tae Joo Shin - One of the best experts on this subject based on the ideXlab platform.
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Rational Design and Construction of Hierarchical Superstructures Using Shape-Persistent Organic Cages: Porphyrin Box-Based Metallosupramolecular Assemblies
2018Co-Authors: Younghoon Kim, Jaehyoung Koo, In-chul Hwang, Rahul Dev Mukhopadhyay, Soonsang Hong, Jejoong Yoo, Ajaz Ahmad Dar, Ikjin Kim, Dohyun Moon, Tae Joo ShinAbstract:We report a new approach to building hierarchical superstructures using a shape-persistent porous organic cage, which acts as a premade secondary building unit, and coordination chemistry. To illustrate the principle, a zinc-metalated porphyrin box (Zn-PB), a corner-truncated cubic porous cage, was connected by suitable dipyridyl terminated bridging ligands to construct PB-based hierarchical superstructures (PSSs). The PSSs were stabilized not only by the coordination bonds between Zn ions and bipyridyl-terminated ligands but also by π–π interactions between the corners of the Zn-PB units. By varying the length of the linker, we identified an optimum range of the linker length for construction of PSSs. The PSSs have large void volumes and an extrinsic surface area compared to the parent PBs, which can be exploited for the selective encapsulation and interior functionalization of the PSSs for various applications, including catalysis. We observed that singlet oxygen induced synthesis of the natural product, juglone, is more efficiently catalyzed by PSS-1 than its Constituent Component Zn-PB
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Rational Design and Construction of Hierarchical Superstructures Using Shape-Persistent Organic Cages: Porphyrin Box-Based Metallosupramolecular Assemblies
AMER CHEMICAL SOC, 2018Co-Authors: Younghoon Kim, Jaehyoung Koo, In-chul Hwang, Rahul Dev Mukhopadhyay, Soonsang Hong, Jejoong Yoo, Ajaz Ahmad Dar, Ikjin Kim, Dohyun Moon, Tae Joo ShinAbstract:We report a new approach to building hierarchical superstructures using a shape-persistent porous organic cage, which acts as a premade secondary building unit, and coordination chemistry. To illustrate the principle, a zinc-metalated porphyrin box (Zn-PB), a corner-truncated cubic porous cage, was connected by suitable dipyridyl terminated bridging ligands to construct PB-based hierarchical superstructures (PSSs). The PSSs were stabilized not only by the coordination bonds between Zn ions and bipyridyl-terminated ligands but also by ��-�� interactions between the corners of the Zn-PB units. By varying the length of the linker, we identified an optimum range of the linker length for construction of PSSs. The PSSs have large void volumes and an extrinsic surface area compared to the parent PBs, which can be exploited for the selective encapsulation and interior functionalization of the PSSs for various applications, including catalysis. We observed that singlet oxygen induced synthesis of the natural product, juglone, is more efficiently catalyzed by PSS-1 than its Constituent Component Zn-PB. (c) Copyright 2018 American Chemical Societ
Uhlemann Elisabeth - One of the best experts on this subject based on the ideXlab platform.
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Adaptive Concatenated Coding for Wireless Real-Time Communications
Chalmers University of Technology Göteborg, 2004Co-Authors: Uhlemann ElisabethAbstract:The objective of this thesis is to improve the performance of real-time communication over a wireless channel, by means of specifically tailored channel coding. The deadline dependent coding (DDC) communication protocol presented here lets the timeliness and the reliability of the delivered information constitute quality of service (QoS) parameters requested by the application. The values of these QoS parameters are transformed into actions taken by the link layer protocol in terms of adaptive coding strategies. Incremental redundancy hybrid automatic repeat request (IR-HARQ) schemes using rate compatible punctured codes are appealing since no repetition of previously transmitted bits is made. Typically, IR-HARQ schemes treat the packet lengths as fixed and maximize the throughput by optimizing the puncturing pattern, i.e. the order in which the coded bits are transmitted. In contrast, we define an IR strategy as the maximum number of allowed transmissions and the number of code bits to include in each transmission. An approach is then suggested to find the optimal IR strategy that maximizes the average code rate, i.e., the optimal partitioning of n-k parity bits over at most M transmissions, assuming a given puncturing pattern. Concatenated coding used in IR-HARQ schemes provides a new array of possibilities for adaptability in terms of decoding complexity and communication time versus reliability. Hence, critical reliability and timing constraints can be readily evaluated as a function of available system resources. This in turn enables quantifiable QoS and thus negotiable QoS. Multiple concatenated single parity check codes are chosen as example codes due to their very low decoding complexity. Specific puncturing patterns for these Component codes are obtained using union bounds based on uniform interleavers. The puncturing pattern that has the best performance in terms of frame error rate (FER) at a low signal-to-noise ratio (SNR) is chosen. Further, using extrinsic information transfer (EXIT) analysis, rate compatible puncturing ratios for the Constituent Component code are found. The puncturing ratios are chosen to minimize the SNR required for convergence. The applications targeted in this thesis are not necessarily replacement of cables in existing wired systems. Instead the motivation lies in the new services that wireless real-time communication enables. Hence, communication within and between cooperating embedded systems is typically the focus. The resulting IR-HARQ-DDC protocol presented here is an efficient and fault tolerant link layer protocol foundation using adaptive concatenated coding intended specifically for wireless real-time communications
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Adaptive Concatenated Coding for Wireless Real-Time Communications
Göteborg : Chalmers tekniska högskola, 2004Co-Authors: Uhlemann ElisabethAbstract:The objective of this thesis is to improve the performance of real-time communication overa wireless channel, by means of specifically tailored channel coding. The deadlinedependent coding (DDC) communication protocol presented here lets the timeliness and thereliability of the delivered information constitute quality of service (QoS) parametersrequested by the application. The values of these QoS parameters are transformed intoactions taken by the link layer protocol in terms of adaptive coding strategies.Incremental redundancy hybrid automatic repeat request (IR-HARQ) schemes usingrate compatible punctured codes are appealing since no repetition of previously transmittedbits is made. Typically, IR-HARQ schemes treat the packet lengths as fixed and maximizethe throughput by optimizing the puncturing pattern, i.e. the order in which the coded bitsare transmitted. In contrast, we define an IR strategy as the maximum number of allowedtransmissions and the number of code bits to include in each transmission. An approach isthen suggested to find the optimal IR strategy that maximizes the average code rate, i.e., theoptimal partitioning of n-kparity bits over at most M transmissions, assuming a givenpuncturing pattern. Concatenated coding used in IR-HARQ schemes provides a new arrayof possibilities for adaptability in terms of decoding complexity and communication timeversus reliability. Hence, critical reliability and timing constraints can be readily evaluatedas a function of available system resources. This in turn enables quantifiable QoS and thusnegotiable QoS. Multiple concatenated single parity check codes are chosen as examplecodes due to their very low decoding complexity. Specific puncturing patterns for theseComponent codes are obtained using union bounds based on uniform interleavers. Thepuncturing pattern that has the best performance in terms of frame error rate (FER) at a lowsignal-to-noise ratio (SNR) is chosen. Further, using extrinsic information transfer (EXIT)analysis, rate compatible puncturing ratios for the Constituent Component code are found.The puncturing ratios are chosen to minimize the SNR required for convergence.The applications targeted in this thesis are not necessarily replacement of cables inexisting wired systems. Instead the motivation lies in the new services that wireless real-time communication enables. Hence, communication within and between cooperatingembedded systems is typically the focus. The resulting IR-HARQ-DDC protocol presentedhere is an efficient and fault tolerant link layer protocol foundation using adaptiveconcatenated coding intended specifically for wireless real-time communications.Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie, 2198, Technical report. D, 29,
Viсtor Nikitevich Khudyakov - One of the best experts on this subject based on the ideXlab platform.
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об одном содержательном компоненте модели подготовки будущих управленческих кадров about one Constituent Component of the future managers training model
Social Science Research Network, 2014Co-Authors: Viсtor Nikitevich KhudyakovAbstract:Russian Abstract: Одной из актуальнейших задач образования является поиск эффективной модели подготовки управленческих кадров для государственной и муниципальной модели, безусловно, является её содержательная сторона. В которой, особое место занимает лингвистическая компетентность. English Abstract: One of the most urgent problems of education is the search of effective model of training state and municipal managers and the Constituent Component of this model – linguistic competence.