Design of a Noise-Canceling CMOS Wideband Receiver Front-End with Inherent Active Balun

This paper presents the design of an ESD-protected noise-canceling CMOS wideband receiver front-end for cognitive and ultra-wideband (UWB) radio-based wireless communications. Designed in a 0.13-μm CMOS technology, the RF front-end integrates a broadband low-noise amplifier (LNA) and a quadrature down-conversion mixer. While having ESD and package parasitics absorbed into a wideband input matching network, the LNA exploits a combination of a common-gate (CG) stage and a common-source (CS) stage to cancel the noise of the CG-stage and to provide a well balanced differential output for driving the double-balance mixer, which has a merged quadrature topology. A variable-gain method is developed for the LNA to achieve a large factor of gain switch without degrading the input impedance match and the balun function. Drawing 24 mA from 1.5 V, simulations show that the proposed front-end has a 3-dB bandwidth of around 10 GHz spanning from 1.8 GHz up to 11.8 GHz with a maximum voltage conversion gain of 30 dB and a noise figure of 4.3–6.7 dB over the entire band.     

Seasonal storage of electricity by hydrogen in benzene–water system

The use of hydrogen in benzene–water system which combines water electrolysis and hydrogenation in a polymer electrolyte cell was carried out as a means for seasonal storage of electricity. Gas diffusion electrodes were effective in improving coupled reactions of electrochemical benzene hydrogenation and water electrolysis. The reaction kinetics for the electrochemical hydrogenation process using gas diffusion electrodes was investigated by evaluating current efficiency and reaction rate. The results showed that the rate of hydrogen evolution was higher than the rate of benzene hydrogenation and the apparent activation energy of hydrogen evolution was lower than that of benzene hydrogenation. As the electrode potential increased, the hydrogen evolution rate increased. The benzene hydrogenation reaction rate reached a maximum at −0.8 V electrode potential, then decreased slightly. The current efficiency, however, reached its maximum at −0.7 V. Modifying electrodes by adding 0.2 wt% polyethylene glycol (PEG6000) reduced the mass transfer resistance of organic phase (cyclohexane/benzene) and improved the hydrogenation reaction rate.     

Enhancing separation of titanium and iron by three‐liquid‐phase extraction with 1,10‐phenanthroline as additive

BACKGROUND: A three‐liquid‐phase system (TLPS) composed of an organic solvent‐rich top phase, a polymer‐rich middle phase and a salt‐rich bottom phase is a newly emerging separation medium. Due to low affinity of the polymer‐rich phase for metals it is necessary and important to search for a suitable complexing agent that has a definite affinity for the polymer‐rich middle phase and a high selectivity for the metal ion of interest. RESULTS: Addition of 1,10‐phenanthroline (phen) is effective in enhancing the separation of titanium and iron from magnesium in the TLPS consisting of trialkylphosphine oxide (TRPO)‐PEG 2000‐(NH₄)₂SO₄. Hydrogen‐bonding interactions between PEG 2000 and phen molecules are the driving force for anchoring tri(phen)‐iron(II) sulfate complexes in the middle phase. Under the conditions (pH = 1.5, molar ratio of phen to iron(II) = 3.4:1), nearly 86% of titanium was extracted into the top phase while 100% of iron(II) was distributed in the middle phase, without any interference between the metal species. The separation factor of titanium and iron in the upper two phases was greater than 20 000. CONCLUSIONS: A single step of extraction and separation of titanium and iron from magnesium was realized in the TRPO‐PEG 2000‐(NH₄)₂SO₄ TLPS with phen as additive. It highlights the effectiveness of TLPS in dealing with multi‐metal solutions and suggests a potential use of TLPS in the separation of iron and other target metals. As iron is ubiquitous the separation of iron is often needed in both analytical processes and the hydrometallurgical industry. Copyright © 2012 Society of Chemical Industry     

锡铁山锌精矿稀散金属综合利用前景分析

锡铁山锌精矿产量丰富，伴生的稀散金属铟、锗、镓、镉的含量可分别达到175 g/t、18 g/t、20 g/t、3 713 g/t，普遍具有综合利用价值。从稀散金属的实用性和市场需求出发，结合稀散金属在锡铁山锌精矿中赋存的特点，分析计算铟、锗、镓、镉的潜在经济价值，阐述当前利用现状并展望综合利用前景。     

Comparison of Contract General Conditions between United States and China

In light of the fact that construction projects are expensive, complex, and time-consuming undertakings, a well-written contract that specifies each participant’s duties and obligations is required. Furthermore, a well-written contract with regard to business practice differences between the United States and China is unquestionably needed by American owners, design firms, and construction companies conducting business in China. In response to this industry need, general conditions of construction contracts commonly used in the United States (AIA-A201) and China (GF-1999-0201) have been analyzed and compared. The findings of this research reveal that the content of subclauses in AIA-A201 and GF-1999-0201 is different in several ways. These differences may have been caused by cultural, historical, geographical, political, and language variations that exist between the American and Chinese construction markets. Understanding these differences could help U.S. companies stay competitive and profitable in China.     

Preparation,characterization and hydrotreating performances of ZrO2–Al2O3-supported NiMo catalysts

A series of Al₂O₃–ZrO₂ composite supported NiMo catalysts with various ZrO₂ contents were prepared. Several techniques including XRD, SEM, N₂ physisorption, H₂-TPR, and UV–vis DRS were used for typical physico-chemical properties characterization of the ZrO₂–Al₂O₃ composite supports and their NiMo/ZrO₂–Al₂O₃ catalysts. The test results showed that the composite supports prepared by the chemical precipitation method existed as amorphous phase in the samples with insufficient contents of ZrO₂, and the incorporation of ZrO₂ into supports provided a better dispersion of NiMo species, which made their reductions become easier. The pyridine-adsorbed FT-IR results indicated that the Lewis acid sites of catalysts increased significantly by the introduction of ZrO₂ into the supports. The activities of these catalysts for diesel oil hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) were evaluated in a high pressure micro-reactor system. The results showed that the ZrO₂–Al₂O₃-supported NiMo catalysts with suitable ZrO₂ contents exhibited much higher catalytic activities than that of Al₂O₃-supported one, and when the ZrO₂ contents were 15% and 5%, the NiMo/Al₂O₃–ZrO₂ catalysts presented the highest HDS and HDN activities, respectively.     

香港理工大学纺织及制衣专业实验室的特色

介绍香港理工大学纺织及制衣学系的实验室和工作室在传统与创意、科技与创新、管理与自主结合方面的特色，以期为发展具有中国内地特色的纺织服装教育提供借鉴与参考。     

一种新的通用概念层次编码方法

概念层次是目前数据挖掘和知识发现的前沿性方法。为了把概念层次用于数据挖掘,需要解决如何从现有数据集自动生成概念层次,如何存储和处理网状概念层次结构及如何提高概念层次结构的搜索效率等问题。文章提出适用于任何数据挖掘功能的通用编码方法——基于层次域的概念层次实数编码法,该方法有效地解决了概念层次的存储和检索问题,并在微机电系统领域进行了与典型算法的对比分析。     

Electrochemical hydrogenation of organic sulfides

Electrochemical reduction desulfurization is a low cost, environmental friendly technology which is capable of achieving a high degree of automation. Electrochemical coupling reactions of organic sulfur hydrogenation and water electrolysis on the C/Nafion electrodes were performed. The electrochemical desulfurization was determined by cyclic voltammetry (CV), bulk electrolysis with coulometry (BEC) and electrochemical impedance spectroscopy (EIS) techniques. Thiophene and benzyl mercaptan were used as model organic sulfur compounds. The results of cyclic voltammetry showed that the electrochemical hydrogenation reduction reaction of thiophene occurred at about ?0.35 V. The process included proceeding chemical reaction and electrochemical reaction. The currents generated from thiophene hydrogenation reactions increased with the reaction temperature and the H⁺ concentration of the electrolyte acidity of anode. Under the same reaction conditions, the desulfurization efficiency of benzyl mercaptan was significantly higher than that of thiophene. From the products of electrolytic reactions, the mechanisms of electrochemical hydrogenation of thiophene were proposed, consisting of two pathways: ring opening followed by hydrogenation and directly hydrogenation followed by ring opening. The proposed reaction mechanisms were consistent with the EIS results, indicating the predominant reactions were ring opening followed by hydrogenation. The reaction products and EIS results suggested that the reaction mechanisms of electrochemical hydrogenation of benzyl mercaptan were by breaking CS bond to form H₂S and toluene.     

A theoretical study of fault coupling

Fault coupling is the phenomenon whereby a test set is able to detect faults when they occur in isolation, but fails to do so when they occur in combination. It is widely regarded as a nuisance in fault‐based approaches to software testing, which focus on the detection of single faults and normally neglect multiple faults. This paper presents a theoretical study of fault coupling, based on a simple model of fault‐based testing. This provides for the presence of two faults that interact with each other and thus includes the possibility of fault coupling between them. The model is analysed mathematically, the conclusion reached being that fault coupling only occurs infrequently. This result provides support for current approaches to fault‐based testing, but it is not quite enough to conclude that they are thereby validated. In effect, the paper generalizes the results of a previous paper that dealt with the restricted case where the functions underlying programs are bijective as well as finite. The restriction that functions be bijective is lifted here, but they are still required to be finite. Though the same theoretical framework is used in both cases, and more or less the same results are obtained, the techniques employed to arrive at the results in the general case are quite different. Copyright © 2000 John Wiley & Sons, Ltd.