SOA-based polarity-preserving all-optical wavelength conversion at 80Gbit/s: Wide conversion range, well dynamic characteristics and polarization insensitive

This letter presents the effective design of a tunable 80 Gbit/s wavelength converter with a simple configuration consisting of a single semiconductor optical amplifier (SOA) and an optical bandpass filter (OBPF). Based on both cross-gain and cross-phase modulation in SOA, the polarity-preserved, ultrafast wavelength conversion is achieved by appropriately filtering the blue-chirped spectral component of a probe light. Moreover, the experiments are carried out to investigate into the wavelength tunability and the maximum tuning range of the designed wavelength converter. Our results show that a wide wavelength conversion range of nearly 35 nm is achieved with 21-nm downconversion and 14-nm upconversion, which is substantially limited by the operation wavelength ranges of a tunable OBPF and a tunable continuous-wave laser in our experiment. We also exploited the dynamics characteristics of the wavelength converter with variable input powers and different injection current of SOA. (C) 2008 Wiley Periodicals, Inc.

A 10-bit 50-MS/s sample-and-hold circuit with low distortion sampling switches

A fully-differential switched-capacitor sample-and-hold (S/H) circuit used in a 10-bit 50-MS/s pipeline analog-to-digital converter (ADC) was designed and fabricated using a 0.35-μm CMOS process. Capacitor fliparound architecture was used in the S/H circuit to lower the power consumption. In addition, a gain-boosted operational transconductance amplifier (OTA) was designed with a DC gain of 94 dB and a unit gain bandwidth of 460 MHz at a phase margin of 63 degree, which matches the S/H circuit. A novel double-side bootstrapped switch was used, improving the precision of the whole circuit. The measured results have shown that the S/H circuit reaches a spurious free dynamic range (SFDR) of 67 dB and a signal-to-noise ratio (SNR) of 62.1 dB for a 2.5 MHz input signal with 50 MS/s sampling rate. The 0.12 mm~2 S/H circuit operates from a 3.3 V supply and consumes 13.6 mW.

A Compact Direct Digital Frequency Synthesizer for the Rubidium Atomic Frequency Standard

A compact direct digital frequency synthesizer （DDFS） for system-on-chip implementation of the high precision rubidium atomic frequency standard is developed. For small chip size and low power consumption, the phase to sine mapping data is compressed using sine symmetry technique, sine-phase difference technique, quad line approximation technique,and quantization and error read only memory （QE-ROM） technique. The ROM size is reduced by 98% using these techniques. A compact DDFS chip with 32bit phase storage depth and a 10bit on-chip digital to analog converter has been successfully implemented using a standard 0.35μm CMOS process. The core area of the DDFS is 1.6mm^2. It consumes 167mW at 3.3V,and its spurious free dynamic range is 61dB.

A novel polarization-insensitive semiconductor optical amplifier structure with large 3dB bandwidth

A novel approach to achieving a polarization-insensitive semiconductor optical amplifier is presented. The active layer consists of graded tensile strained bulk-like structure. which can not only enhance TM mode material gain and further realize polarization-insensitivity, but also get a large 3dB bandwidth due to different strain introduced into the active layer. 3dB bandwidth more than 40nm. 65nm has been obtained in die experiment and theory, respectively. The characteristics of such polarization insensitive structure have been analyzed, The influence of the amount of strain and of the thickness of strain layer on the polarization insensitivity has been discussed.

组合白腐真菌预处理木质纤维素原料的研究

木质纤维素原料种类多、分布广、数量巨大，通过燃料乙醇生产技术、厌氧沼气发酵技术将其转化成乙醇、沼气等二次能源，一定程度上可以缓解化石能源的不断消耗所带来的能源危机，也解决了农林废弃物引起的环境污染问题。其中以木质纤维素原料生产燃料乙醇，还可以避免以淀粉类和糖类原料生产燃料乙醇时带来的“与人争粮”等一系列问题。因此具有重要的经济效益、环境效益和社会效益。 然而，木质纤维素原料结构致密，木质素包裹在纤维素、半纤维素外围，导致其很难被降解利用，必须进行适当的预处理，去除木质素，打破原有的致密结构，利于原料的后续利用。因此，预处理成为木质纤维素原料能源化利用的关键。而目前预处理环节的费用过于昂贵，于是寻找一种高效、低成本的预处理方法是当今研究的热点。 本论文采用组合白腐真菌对木质纤维素原料进行生物预处理研究，与其他物理化学法相比，该法有着专一性较强、反应温和、不造成环境污染、成本低等优势。白腐真菌主要通过分泌木质素降解酶对木质素进行降解，从而破坏原料的致密结构，提高后续利用效率。所以木质素降解酶酶活的高低是影响原料预处理效果的一个关键因素。于是本论文首先通过将白腐真菌进行组合的方式提高木质素降解酶（漆酶，Lac）酶活；接着对组合菌的菌株相互作用机理进行研究，阐明组合菌Lac 酶活提高的原因，为菌株组合提高Lac 酶活这种方法的应用提供理论依据，同时也为后续组合白腐真菌预处理木质纤维素原料提供指导；进一步采用固态发酵和木质素降解酶两种方式对木质纤维素原料进行预处理研究，最大化去除木质素成分，破坏原料的致密结构；最终对预处理后原料的酶解糖化进行初步研究，为原料后续的能源化应用奠定基础。具体研究结果如下： （1） 以实验室保存的三株主要分泌Lac 的白腐真菌为出发菌株，筛选得到一组Lac 酶活明显提高的组合菌55+m-6，其中菌株55 为Trametes trogii sp.，m-6 为Trametes versicolor sp.，组合后Lac 酶活较单菌株分别提高24.13倍和4.07 倍。组合菌的最适产酶条件为pH 6.5、C/N 16:1、Tween 80 添加量为0.01%，在该条件下组合菌的Lac 酶活峰值比未优化时提高4.11倍。 （2） 对组合菌55+m-6 菌株间相互作用机理进行研究，发现菌株之间不存在抑制作用；平板培养时，菌丝交界处Lac 酶活最高并分泌棕色色素；液体培养时，菌株m-6 对组合后Lac 酶活的提高起着更为重要的作用：菌株m-6的菌块、过滤灭菌胞外物以及高温灭菌胞外物均能明显刺激菌株55 的Lac产生；菌株55、m-6 进行组合后，同工酶种类未发生增减，但有三种Lac同工酶浓度有所提高；对菌株胞外物进行薄层层析和质谱分析，结果表明组合前后菌株胞外物中各物质在浓度上存在较大的变化。推测组合菌Lac酶活的明显提高，主要是由于菌株m-6 胞外物中的一些物质能刺激菌株55 分泌大量Lac 进行代谢，且这些刺激物质并非菌株m-6 特有，菌株55自身也可以代谢生成，但是适当的浓度才能刺激Lac 的大量分泌。 （3） 将组合菌55+m-6 用于固态发酵预处理木质纤维素原料，发现其对玉米秆的降解程度最大，在粉碎度40 目、含水率65%的最优处理条件下，处理至第15d，秸秆失重率为41.24%，其中木质素、纤维素、半纤维素均有降解，且Lac 和纤维素酶（CMC）酶活以及还原糖量均达到峰值。 （4） 对玉米秆进行木质素降解酶预处理，发现Lac/1-羟基苯并三唑（HBT）系统对玉米秆木质素的降解效果最好，在最优处理条件时，即HBT 用量0.2%、处理时间1d、Lac 用量50U/g，木质素降解率可达12.60%。预处理后玉米秆的致密结构被破坏，比表面积增大，利于后续酶与纤维素、半纤维素成分的结合。 （5） 对预处理后的玉米秆进行酶解糖化，其中组合菌固态发酵预处理后玉米秆的糖化率比对照高4.33 倍；Lac/HBT 系统预处理后玉米秆的糖化率比对照高2.99％，糖化液中主要含有木糖、葡萄糖两种单糖。 There are many kinds and large quantities of lignocellulosic biomass widely distributed on the earth. They can be converted into secondary energy such as fuel ethanol, biogas, et al., which can relieve the energy crisis caused by consumption of fossil energy resources and solve the problem of environmental pollution caused by agriculture and forestry waste. Meanwhile, the production of fuel ethanol from lignocellulosic biomass can ensure food supply to human kind instead of starch- and sugar-containing raw materials. So the energy conversion of lignocellulosic biomass contributes considerable economic, environment and social benefits. However, lignocellulosic biomass has the compact structure, in which lignin surrounds cellulose and hemicellulose, so it must be pretreated before energy usage and pretreatment is one of the most critical steps in the energy conversion of lignocellulosic biomass. At present, the cost of pretreatment is too expensive, so looking for an efficient and low-cost pre-treatment method is one of recent research hot spots. In this research, combined white rot fungi pretreatment method was used, which had some advantages in low cost, high specificity, mild reacting conditions and friendly environmental effects compared with the other physical and chemical methods. White rot fungi secrete lignin degrading enzymes to degrade the content of lignin and damage the contact structure of lignocellulosic biomass, so the activity of the lignin degrading enzymes is the key factor to the degradation effect of raw materials. Firstly, the combined fungi with high laccase activity were screened; secondly, the interaction mechanism between strains was studied, and the cause of higher laccase activity after strains combination was also preliminary clarified; under the guidance of the mechanism, lignocellulosic biomass was pretreated by the combined fungi; lastly, the enzymatic hydrolysis of pretreated lignocellulosic biomass was also preliminary studied; all of the researches could lay the foundation for the energy application of lignocellulosic biomass. The specific research results were as follows: (1) The combined fungi 55+m-6 with significant higher laccase activity were screened from the three white rot fungi stored in our lab which mainly secreted laccase. Strain 55 and strain m-6 were Trametes trogii sp. and Trametes versicolor sp., respectively. The laccase activity of combined fungi was 24.13 and 4.07-fold than strain 55 and strain m-6, respectively. The optimized condition for laccase production of the combined fungi in liquid medium was pH 6.5, C/N 16:1 and Tween 80 0.01%. In this optimized condition, the laccase activity of combined fungi was 4.11-fold higher comparing with which in non-optimized medium. (2) The interaction mechanism between strain 55 and strain m-6 was further studied, and no inhibition effect was observed. Brown pigment was secreted on the junction of the two strains on the plate, where the highest laccase activity was detected. Strain m-6 was much important to boost laccase activity of combined fungi in liquid medium, and strain 55 was stimulated by fungal plug, filter sterilized extracellular substances and high temperature sterilized extracellular substances of strain m-6 to produce laccase. The types of laccase isozymes did not change after combining strain 55 and strain m-6, but the concentrations of three types increased. Mass Spectrometry and TLC analysis of extracellular substances of each strain showed that concentration of some substances considerably changed after strains were combined. It was supposed that the cause of higher laccase activity of combined fungi was mainly due to some extracellular substances of strain m-6 with the appropriate concentration which stimulated laccase secretion of strain 55 and generated not only by strain m-6 but also by strain 55. (3) Combined fungi 55+m-6 were used to lignocellulosic biomass pretreatment with the type of solid-state fermentation. The highest degree of degradation of corn straw was obtained, including the rate of weight loss was 41.24% and the lignin, cellulose and hemicellulose were degraded partially under the optimized condition of 40 mesh, 65% water content on 15th day. Laccase, CMCase activities and content of reducing sugar reached the maximum value on that day. (4) Lignin degrading enzymes from combined fungi 55+m-6 were used for corn straw pretreatment. The most remarkable degradation of lignin in corn straw with Lac/1-hydroxybenzotriazole (HBT) system was observed, and the 12.60% lignin degradation was obtained under the optimized condition of 0.2% HBT, 50 U/g laccase for 1 d. After pretreated by Lac/HBT, the tight structure of corn straw was demolished and specific surface area increased, which had advantages for accessible of enzyme to cellulose and hemicellulose. (5) The corn straws pretreated by combined fungi 55+m-6 with the type of solid-state fermentation and Lac/HBT were used for enzymatic hydrolysis, and the saccharification rates of each pretreatment type were 4.33 times and 2.99% higher than CK, respectively. The enzymatic hydrolysis liquid of corn straw pretreated by Lac/HBT mainly contained xylose and glucose.

H桥斩波电源的小信号数学模型及其数字化控制器的实现

A brief summary of H bridge non-isolated DC-DC converter and operation principles is presented in this paper. A small signal model of the ideal converter in continuous current mode is proposed and simulation results of the converter are given. The hardware structure of digital power supply controller based on TMS320F2808 MCU is introduced. 中文摘要：概括了加速器 H 桥非隔离式电源的运行原理与特点，在简化运行方式基础上建立了理想状态下电源连续工作模式的数学模型，并给出了仿真分析结果，介绍了基于 TMS320F2808MCU 实现的数字化电源控制器结构。

Monte Carlo studies of micromegas as a neutron detector and its track reconstruction

In this paper a two dimensional readout micromegas detector with a polyethylene foil as converter was simulated on GEANT4 toolkit and GARFIELD for fast neutron detection. A new track reconstruction method based on time coincidence technology was developed in the simulation to obtain the incident neutron position. The results showed that with this reconstruction method higher spatial resolution was achieved.

Longitudinal scaling property of the charge balance function in Au plus Au collisions at root s(NN)=200 GeV

We present measurements of the charge balance function, from the charged particles, for diverse pseudorapidity and transverse momentum ranges in Au + Au collisions at root S-NN = 200 GeV using the STAR detector at RHIC. We observe that the balance function is boost-invariant within the pseudorapidity coverage vertical bar-1.3, 1.3 vertical bar. The balance function properly scaled by the width of the observed pseudorapidity window does not depend on the position or size of the pseudorapidity window. This scaling property also holds for particles in different transverse momentum ranges. In addition, we find that the width of the balance function decreases monotonically with increasing transverse momentum for all centrality classes. (c) 2010 Elsevier B.V. All rights reserved.

不同轮作施肥对土壤有机氮分解特征的影响

在各长期轮作施肥系统中,耕层土壤矿化培养过程的pH及剖面矿化势的变化,说明了长期不同的轮作和施肥方式引起土壤有机氮数量和性质的变化。pH变化具有一共同特征,在0~4 周,各处理间差异显著;而后期变化趋势趋于一致,向微碱性环境发展。各处理的剖面矿化势的变化反映了有机氮可矿化数量的改变。小麦连作施肥和苜蓿连作施肥均说明施用有机肥对土壤有机氮水平有较好的提高作用。粮豆轮作3 a对土壤供氮能力的提高作用大于粮饲轮作4 a和裸地处理。

Footwear for Gender Recognition

Conventionally, biometrics resources, such as face, gait silhouette, footprint, and pressure, have been utilized in gender recognition systems. However, the acquisition and processing time of these biometrics data makes the analysis difficult. This letter demonstrates for the first time how effective the footwear appearance is for gender recognition as a biometrics resource. A footwear database is also established with reprehensive shoes (footwears). Preliminary experimental results suggest that footwear appearance is a promising resource for gender recognition. Moreover, it also has the potential to be used jointly with other developed biometrics resources to boost performance.

A method for quantitative analysis of nitrogen oxides and N2 by means of mass spectrometry with the assistance of a catalytic technique for the reduction of NO with CO or hydrocarbons

Mass spectrometry is not able to differentiate NOx and N2 from other interferences (e.g. CO and C2H4) in the deNOx reactions. In the present study, a quantitative method for analysis of NOx and N2 simultaneously in these reactions with an assisted converter operated at higher temperature under O2-rich condition, which eliminates the interferences, is developed. The NOx conversion from this method is comparable to the one from an Automotive Emission Analyser equipped with NOx electrochemical sensor. Two types of deNOx reactions are tested in terms of selectivity of N2 production. The application of this method is discussed.

Evaluation of Effects of Bivalent Cations on the Formation of Purine-rich Triple-Helix DNA by ESI-FT-MS

The GGA triplet repeats are widely dispersed throughout eukaryotic genomes. (GGA)n or (GGT)n oligonucleotides can interact with double-stranded DNA containing (GGA:CCT)n to form triple-stranded DNA. The effects of 8 divalent metal ions (3 alkaline-earth metals and 5 transition metals) on formation of these purine-rich triple-helix DNA were investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-MS). In the absence of metal ions, no triplex but single-strand, duplex, and purine homodimer ions were observed in mass spectra. The triple-helix DNA complexes were observed only in the presence of certain divalent ions. The effects of different divalent cations on the formation of purine-rich triplexes were compared. Transition-metal ions, especially Co2+ and Ni2+, significantly boost the formation of triple-helix DNA, whereas alkaline-earth metal ions have no positive effects on triplex formation. In addition, Ba2+ is notably beneficial to the formation of homodimer instead of triplex.

Observations on the spawning behavior of artificially matured Japanese eels Anguilla japonica in captivity

Spawning behavior of artificially matured Japanese eels Anguillo japonica in captivity was investigated using a DVD Video image system. Following a routine hormone treatment technique for this fish, female eels were artificially matured by weekly intramuscular injections of salmon pituitary extracts (SPE) at a dosage of 40 mg kg(-1) BW for a total of 7-11 doses to induce ovarian maturation, while male eels received weekly intramuscular injections of human chorionic gonadotropin (HCG) at a dosage of 1000 IU kg(-1) BW for a total of 6-11 doses at 18 degrees C to induce testicular maturation in a separate aquarium. In this experiment, three pairs of such hormone-treated matured eels were acclimatized in seawater in 1.5 m(3) experimental aquaria with or without shelters at 20 degrees C for 24 h. Twenty four hours after the acclimatization terminated, the females received SPE injections to boost maturation and ovulation. Twenty four hours following these injections, the females received injections of HCG (1000 IU per fish, HCG injection) and 17 alpha-hydroxyprogesterone (2 mg per fish) to induce ovulation, while males were given HCG injections (1000 IU per fish, HCG injection) to induce spermiation. Video taping started after the 24 h acclimatization terminated and last for a total of 96 h. Before the HCG injections, both sexes were inactive, staying on the bottom or in shelters if available. Following these HCG injections, they became active and frequently left the bottom swimming in the water column. During the 24 h following HCG injections, activity accounted for 67% and 45% of the total activity in no shelter treatment for females and males, respectively, in comparison with 77% and 78% in shelter treatment. Activity was significantly more pronounced during this phase than during other phases for each sex in either shelter treatment. Egg release and sperm ejection occurred in the water column around the time eels' activity reached peaks. Eels either returned into the shelters or stayed motionlessly on the bottom of the aquaria after egg release and sperm ejection. Eight out of nine (89%) females in no shelter treatment spontaneously released eggs with a total of 11 batches 14-18 h following HCG injections, in contrast with four out of nine (44%) females releasing eggs for 4 batches 16-20 h in shelter treatment. Males arrived at activity peaks 11-13 h following HCG injections in no shelter treatment, 2-4 h ahead of the females (14-16 h), in comparison with 8-11 h in shelter treatment with 5-6 h ahead of the females (14-17 h). Courtship behavior indicative of spawning such as pairing, chasing and touching bodies was not observed in the eels in this study. However, on many occasions, eels of both sexes (male-female or female-female) were found to "cruise together" in water column for a short time period or frequently come together prior to releasing eggs and ejecting sperm, suggesting the possibility of group mating in artificially matured Japanese eels. (c) 2007 Elsevier B.V. All rights reserved.

基于MAX5307和DSP的多回路测控系统设计

提出了一种多回路测控系统的设计方案。该方案仅使用一个DSP(数字信号处理器)及一个多通道集成的D/A转换器件MAX5307,不仅同时保证了多个测控回路的实时性及控制精度,而且实现简单,成本低廉。文中结合实际系统,给出了其具体的硬件和软件实现。该方法具有广泛的适用性,对类似系统的设计具有参考价值。

空间对接缓冲试验台助推装置研究

设计了一种用于空间对接缓冲试验台的新型高动态响应助推力模拟装置。介绍了助推装置的机构组成和原理,计算了助推气动系统的响应时间,并分析了助推运动过程。研究表明:该助推装置的响应速度快、精度高,助推力方向实时通过模拟飞行器的质心,满足设计要求。