低温液体罐车自增压汽化器的设计

本文介绍了低温液体汽车罐车自增压汽化器工作原理,影响汽化量的因素,换热管散热量的计算,从理论和实践角度探索低温液体罐车自增压汽化器的设计问题。     

Bipolar membranes in forward bias region for fuel cell reactors

Three bipolar membranes, two home-made composed of commercial cation (DuPont) and anion (FuMA-Tech) exchange membranes (called Nafion/FT-FAA and Nafion/FT-FAS) and a commercial one, BP-1 from FuMA-Tech, were investigated in order to characterize their suitability to use in a H₂/O₂ fuel cell intended to produce hydrogen peroxide on the cathode instead of water. The Nafion/FT-FAA and Nafion/FT-FAS membranes were prepared using a hot-pressing method. The optimal hot-pressing conditions were determined by measuring the ionic conductivity of the membranes. The latter was observed to depend on the relative humidity of the bipolar membrane. Of the studied bipolar membranes, Nafion/FT-FAA showed the best performance. The transport number of protons measured in a concentration cell was observed to depend on the direction of the proton diffusion flux through these membranes so that transport numbers of ca. unity were obtained when the cation exchange side faced the solution with higher proton concentration. In the opposite case, when the higher concentration faced anion exchange side, the transport number of proton was clearly lower, indicating the usefulness of the bipolar membranes for hydrogen peroxide production in the fuel cell.     

Modeling carbonation for corrosion risk prediction of concrete structures

Damage of reinforced concrete structures is often caused by corrosion of steel reinforcements due to carbonation. Although literature on carbonation has become vast, a comprehensive numerical model for quantitative prediction of the corrosion risk that allows for environmental influences such as temperature and humidity seems lacking. The aim of the present paper is the development of a theoretical model to predict carbonation of concrete structures. The model describes movement and retention of heat, moisture and carbon dioxide (CO₂) by means of balance equations and diffusion laws. The balance equations are coupled and take into account the interaction between different transport and storing processes. A new mathematical formulation of the function of moisture in balance faithfully represents the moisture-storing properties of a porous media. The evolutionary equation of the reaction of CO₂ is derived from reaction kinetics that are described by the Arrhenius' function. The model is solved by means of an efficient numerical method using a Finite Element concept and numerical time integration techniques. It is verified by using results from experimental tests reported in the literature. Taking into account changing atmospheric conditions, structures are investigated with respect to the corrosion risk of steel reinforcements. Together with threshold values taken from the literature, the numerical results give the corrosion risk of reinforced concrete structures.     

Control allocation and management of redundant control effectors based on bases sequenced optimal method

For an advanced aircraft, the amount of its effectors is much more than that for a traditional one, the functions of effectors are more complex and the coupling between each other is more severe. Based on the current control allocation research, this paper puts forward the concept and framework of the control allocation and management system for aircrafts with redundancy con-trol effectors. A new optimal control allocation method, bases sequenced optimal (BSO) method, is then presented. By analyz-ing the ph...     

基于AHP-SCE的城市公交线网综合评价

评价城市公交线网受多方面因素的影响,在考虑影响公交线网评价多种因素的基础上,建立AHP-SCE模型进行定量与定性分析结合的评价,使评价结果更加科学,该评价结果可以为改善公交线网提供重要的依据。本文以南昌市公交线网为例,对南昌市公交线网进行了综合评价,分析中发现南昌市公交线网主要存在线网密度低、平均站距大、线路分布不均衡等问题,为南昌市公交线网改进提供参考。     

试谈铁路交通运输改革与创新

铁路是一个国家的经济命脉,是国家和社会赖以发展的基础行业,而铁路运输则是其中最重要的一环,在国家交通体系中处于骨干位置。由于我国铁路行业整体基础薄弱、技术落后,使得铁路运输行业成了国企改制的重中之重。因此,本文介绍了我国铁路交通运输行业中存在的问题,并在借鉴国外铁路运输改革先进成果的基础上,对我国铁路运输行业改革的思路进行了初步探讨。并就铁路运输企业从技术、经营理念、内部管理方式等方面的创新进行了论述。     

MPSoC based on Transport Triggered Architecture for baseband processing of an LTE receiver

Wireless communication over LTE (long term evolution) brings several design challenges to industry and academia, due to its high throughput demand. Specially in the case of hand held mobile devices where the power budget is very limited and high throughput requires more computation power. On the other hand, the industry is struggling for flexible hardware solution, a Software Defined Radio (SDR), to amortize huge costs of hardware changes to suit the continued evolution in wireless standards. In this article, an MPSoC design has been presented for the baseband processing of a 20 MHz LTE system. Transport Triggered Architecture (TTA) has been preferred over conventional DSPs/VLIW architectures as processing element (PE) of MPSoC. Processing tasks are statically scheduled. Synchronization among the PEs is based on polling of a shared memory space. In addition an approach is presented to organize I/O buffer in such a way that the stalling probability of a PE should be reduced to exploit efficiently data and task level parallelism. The total power consumption by all the PEs synthesized on 130 nm technology at 200 MHz and 1.5 V is 105.04 mW. The total energy consumption to process one subframe including carrier recovery is 0.0767 mJ. Our study shows that TTA architecture brings several improvements in conventional SIMD/VLIW architectures. TTA as contrary to other run time designs has a guaranteed performance and lower energy consumption due to the fact that all the data dependency/independency issues are resolved at compile time. Further, it is also true due to the fact that TTA has a reduced register file (RF) traffic, number of RF ports and lower overall cycle count for a given task. To the best of author’s knowledge this article is among the first few published articles on LTE receiver implementation with published figures like time, frequency, power and perhaps the first article explaining further in detail about data access pattern to process an LTE subframe, memory organization, subsystem interconnection, and synchronization.     

Facilitated transport of carbon dioxide through an immobilized liquid membrane of K2CO3/KHCO3 aqueous solution

The facilitated transport of CO₂ through a hydrophilic polymeric membrane immobilized with K₂CO₃/ KHCO₃ buffer solution has been investigated. The reactions of dissolved CO₂ in electrolyzed alkaline solution must consider hydration of CO₂ with water, chemical reaction of CO₂ with OH^- and dissociation of HCO ₃ ^2- into CO ₃ ^2- . It is necessary to simplify these reactions as a simple model, which is used to analyze the transport system. From experiments in the liquid membrane with alkaline buffer solution, it is shown that the flux of CO₂ into K₂CO₃KHCO₃ aqueous solution can be enhanced by the presence of CO ₃ ^2- . A diffusion model with an overall reaction based on the film theory is proposed that predicts the experimentally observed facilitation factor with reasonable accuracy. The present model is compared with the rigorous diffusion model involving the complicated conventional chemical reactions.