EVALUATION OF SURFACE FORCE-PORE FLOW AND MODIFIED SURFACE FORCE-PORE FLOW MODELS FOR REVERSE OSMOSIS TRANSPORT

The surface force-pore flow (SF-PF) model of reverse osmosis transport and the extended and modified form (the MD-SF-PF model) have been employed to predict the performance of four aromatic polyamide (FilmTec, FT30)reverse osmosis membranes. The evaluation is based on a comparison of model predictions with experimental data. Dilute sodium chloride-water solution experimental data were used to estimate model parameters. The models are then used to predict flux and separation at various operating pressures and concentrations. Membrane performance (i.e., separation and permeate flux) can be well predicted by the MD-SF-PF model while the SF-PF model predicts the performance for the sodium chloride system less satisfactorily.     

Characterization of catalysts and membrane in DMFC lifetime testing

The lifetime and performance of a direct methanol fuel cell (DMFC) were investigated to understand the correlation between the structure of catalysts/membrane and cell performance versus time. The cell polarization and performance curves were obtained during the DMFC operation with the time. The catalysts and Nafion^® membrane of the membrane electrode assembly (MEA) from the lifetime test were comprehensively examined by XRD, HRTEM, FTIR and Raman spectroscopy techniques. The results revealed that there was significant performance degradation during the first 200 h operation; while the degradation was slowing down between 200 and 704 h operation. The degradation became worse after 1002 h operation. The increases of the catalyst particle size from both anode and cathode catalysts were observed after the DMFC lifetime test. The changes of microstructure, surface composition, the interfacial structure of the MEA, and the aging of Nafion^® under the DMFC lifetime tests were also observed.     

Direct laser fabrication of thin-walled metal parts under open-loop control

Direct laser fabrication (DLF) is an advanced manufacturing technology, which can build full density metal parts directly from CAD files without using any modules or tools. The investigation on the fabrication of thin-walled parts of nickel alloy using open-loop DLF process is introduced in this paper. The experimental setup consisted of a CO₂ laser, a 3-axis CNC table, a coaxial powder nozzle and a powder recycler. The 3D-CAD file of a thin-walled metal part was converted into the STL file format and imported into software HUST-RP to generate ‘pseudo-random’ scanning paths of laser beam. The influence of process parameters on the build height of thin-walled metal parts was studied by 1–10 layered single-bead stacks of nickel alloy. The result shows that the interference factors which affect the build height of thin-walled metal parts occur randomly during the process. For open-loop DLF process, thin-walled metal parts can achieve much better shape quality if the process parameters are suitable. Multilayer single-bead walls were built up with different scanning velocity to obtain the optimal process parameters of thin-walled parts of nickel alloy. It shows that thin walls of nickel alloy with uniform height can be built up layer by layer in a certain range of specific energy. However, it is difficult to control the build height of complex thin-walled metal parts in an accurate manner just using optimal parameters. A special coaxial powder nozzle was designed in this paper. In a certain range, the deposition thickness of the nozzle is nearly linearly increased with increase in the standoff distance between the powder focusing point of the nozzle and the deposition substrate. By means of the nozzle, a novel method to control the build height of thin-walled metal parts using open-loop DLF process was introduced. The difference in build height of a thin-walled part can be compensated automatically in one or several layers during the process. It is proved that the build height of a thin-walled metal part can be accurately controlled in theory using the nozzle. A complex single-bead part of nickel alloy whose geometry was designed to be the well-known Chinese ‘FU’ was fabricated and explained in this paper. The result shows that the shape quality of the sample is quite good, and actual build height of the sample is 53.54 mm while the designed value is 54 mm.     

快速直接还原法生产金属化球团工艺的探讨

研究开发了冷固结含碳铁矿球团的还原工艺，它与环形转底炉相结合，形成快速直接还原新工艺，生产金属此球团，具有一系列优点，如：设备简单，生产效率高、能耗低等等。     

无线多用户投影网关切换技术设计与实现

针对目前无线投影网关多用户切换技术研究的缺失及必要性,为了减少切换带来的延迟、抖动,提出了多用户的切换协议。通过实现基于Wi-Fi Direct的无线投影网关系统,模拟多用户使用场景,给出了详细的切换流程、数据结构,同时分析了延迟产生的原因,提出了数据预缓冲技术,进一步对多用户切换进行改进,最后通过实验测试证明其在减少切换延时的有效性。     

直接和间接的笔倾斜输入性能对比

越来越多的笔式设备通过增加笔倾斜输入来提高其输入能力。但在直接输入设备和间接输入设备上执行笔的倾斜操作时,由于操作环境和视觉反馈的不同,往往会导致操作性能产生差异。本研究以探索笔倾斜输入在直接设备和间接设备上的性能差异为目的,以实证手段考察在两种设备上获取不同角间距下的不同笔倾斜目标时的操作速度、稳定性和准确性,讨论导致直接设备和间接设备笔倾斜性能不同的原因,并提出适用的角间距和倾斜目标位置。实验结果表明,在直接设备和间接设备上操作笔倾斜角时,在操作速度上直接设备优于间接设备,但在稳定性和准确性上,间接设备优于直接设备。20°的角间距对两种设备来说都呈现较好的性能,若需要在更小角间距内完成目标选择操作,在间接设备上的效果更好。最后,对两种设备的用户使用习惯进行了总结,为基于笔倾斜角的用户界面设计提供了帮助和参考。     

反渗透处理高含盐废水的实验研究与膜污染分析

试验以经过混凝-超滤预处理后的高含盐废水为研究对象,考察了一级两段反渗透处理工艺对CODcr、TDS等的去除效果以及操作压力、温度、pH等因素对反渗透去除效果的影响。研究表明:在最佳工艺条件下,CODcr的去除率大于90%,TDS的去除率大于99%。反渗透处理后出水达到工业循环冷却水水质要求(GB50330-2002)。膜受污染后采用化学清洗和水力清洗相结合的方法可使膜的透水量恢复97.53%。     

网格域间信任评估模型的研究

在网格域划分的基础上,提出一种域间信任关系评估模型,具有同时兼顾服务的上下文和信任的时衰性的特点,并针对网格环境中的恶意节点和恶意推荐行为,给出相应的应对机制。实验表明,该模型能够有效地解决网格环境中的恶意行为,对恶意节点进行惩罚。     

基于直接连接的分布式数据库查询优化实现方法研究

首先对分布式数据库查询执行代价模型进行分析,然后对直接连接中的连接运算的方法、连接关系的传输方法和执行场地等问题进行研究,并计算所有评估方法的执行代价,从中选择出最小执行代价的执行方法,最终确定了执行的场地、连接的方法和传输方法.     

卫星信号模拟器CBOC中频信号设计与实现

GNSS卫星信号模拟器对于GNSS系统及用户接收机的研究和设计起着非常重要的作用。本文主要研究针对Galileo系统E1频点CBOC中频信号的产生方法及数字处理技术,在基于PCIE+DSP+FPGA+DAC架构的中频板卡上完成了与PC上位机通信、波形控制参数计算和更新、副载波生成、基带信号调制以及模拟中频信号的产生;最后给出了频谱、相关峰、定位误差等测量结果,验证了信号的质量和正确性。