High and stable conversion efficiency obtaining in single-stage multi-crystal optical parametric chirped pulse amplification system

An optical parametric chirped-pulse amplification system is demonstrated to provide 32.9% pump-to-signal conversion efficiency . Special techniques are used to make the signal and pump pulses match with each other in both spectral and temporal domains. The broadband 9.5-mJ pulses are produced at the repetition rate of 1 Hz with the gain of over 1.9 x 10(8). The output energy fluctuation of 7.8% is achieved for the saturated amplification process against the pump fluctuation of 10%.

A direct digital frequency synthesizer with single-stage delta-sigma interpolator and current-steering DAC

This paper presents a direct digital frequency synthesizer (DDFS) with a 16-bit accumulator, a 4th-order single-stage pipelined delta-sigma interpolator and a 300MS/s 12-bit current-steering DAC based on Q(2) Random Walk switching scheme. The delta-sigma interpolator is used to reduce the phase truncation error and the ROM size. The measured spurious-free dynamic range (SFDR) is greater than 80 dB for 8-bit phase value and 12-bit sine-amplitude output. The DDFS prototype is fabricated in a 0.35um CMOS technology with core area of 1.11mm(2).

基于电光材料的光学相控阵技术研究进展

综述了基于电光材料的光学相控阵(OPA)的研究进展。介绍了光学相控阵技术的基本原理以及不同电光材料(铌酸锂电光晶体,AlGaAs光波导,液晶和掺镧锆钛酸铅(PLZT)电光陶瓷)光学相控阵技术的基本构想和涉及的关键技术;着重介绍近年来基于PLZT电光陶瓷材料光学相控阵技术的发展情况以及在这方面的最新研究成果,包括单级相控阵、级联相控阵、不同电极结构(表面电极和上下电极结构)相控阵技术等;最后简要介绍了光学相控阵技术在激光雷达等军事领域中的应用。

A direct digital frequency synthesizer with fourth-order phase domain Delta Sigma noise shaper and 12-bit current-steering DAC

This paper presents a direct digital frequency synthesizer (DDFS) with a 16-bit accumulator, a fourth-order phase domain single-stage Delta Sigma interpolator, and a 300-MS/s 12-bit current-steering DAC based on the Q(2) Random Walk switching scheme. The Delta Sigma interpolator is used to reduce the phase truncation error and the ROM size. The implemented fourth-order single-stage Delta Sigma noise shaper reduces the effective phase bits by four and reduces the ROM size by 16 times. The DDFS prototype is fabricated in a 0.35-mu m CMOS technology with active area of 1.11 mm(2) including a 12-bit DAC. The measured DDFS spurious-free dynamic range (SFDR) is greater than 78 dB using a reduced ROM with 8-bit phase, 12-bit amplitude resolution and a size of 0.09 mm(2). The total power consumption of the DDFS is 200)mW with a 3.3-V power supply.

A direct digital frequency synthesizer with fourth-order phase domain Delta Sigma noise shaper and 12-bit current-steering DAC

This paper presents a direct digital frequency synthesizer (DDFS) with a 16-bit accumulator, a fourth-order phase domain single-stage Delta Sigma interpolator, and a 300-MS/s 12-bit current-steering DAC based on the Q(2) Random Walk switching scheme. The Delta Sigma interpolator is used to reduce the phase truncation error and the ROM size. The implemented fourth-order single-stage Delta Sigma noise shaper reduces the effective phase bits by four and reduces the ROM size by 16 times. The DDFS prototype is fabricated in a 0.35-mu m CMOS technology with active area of 1.11 mm(2) including a 12-bit DAC. The measured DDFS spurious-free dynamic range (SFDR) is greater than 78 dB using a reduced ROM with 8-bit phase, 12-bit amplitude resolution and a size of 0.09 mm(2). The total power consumption of the DDFS is 200)mW with a 3.3-V power supply.

Performance of supersonic model combustors with staged injections of supercritical aviation kerosene

Supersonic model combustors using two-stage injections of supercritical kerosene were experimentally investigated in both Mach 2.5 and 3.0 model combustors with stagnation temperatures of approximately 1,750 K. Supercritical kerosene of approximately 760 K was prepared and injected in the overall equivalence ratio range of 0.5-1.46. Two pairs of integrated injector/flameholder cavity modules in tandem were used to facilitate fuel-air mixing and stable combustion. For single-stage fuel injection at an upstream location, it was found that the boundary layer separation could propagate into the isolator with increasing fuel equivalence ratio due to excessive local heat release, which in turns changed the entry airflow conditions. Moving the fuel injection to a further downstream location could alleviate the problem, while it would result in a decrease in combustion efficiency due to shorter fuel residence time. With two-stage fuel injections the overall combustor performance was shown to be improved and kerosene injections at fuel rich conditions could be reached without the upstream propagation of the boundary layer separation into the isolator. Furthermore, effects of the entry Mach number and pilot hydrogen on combustion performance were also studied.

Microwave-assisted hydrothermal synthesis of hydroxy-sodalite zeolite membrane

A high quality pure hydroxy-sodalite zeolite membrane was successfully synthesized on an alpha-Al2O3 support by a novel microwave-assisted hydrothermal synthesis (MARS) method. Influence of synthesis conditions, such as synthesis time, synthesis procedure, etc., on the formation of hydroxy-sodalite zeolite membrane by MAHS method was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and gas permeation measurements. The synthesis of hydroxy-sodalite zeolite membrane by MAHS method only needed 45 min and synthesis was more than 8 times faster than by the conventional hydrothermal synthesis (CHS) method. A pure hydroxy-sodalite zeolite membrane was easily synthesized by MAHS method, while a zeolite membrane, which consisted of NaX zeolite, NaA zeolite and hydroxy-sodalite zeolite, was usually synthesized by CHS method. The effect of preparation procedures had a dramatic impact on the formation of hydroxy-sodalite zeolite membrane and a single-stage synthesis procedure produced a pure hydroxy-sodalite zeolite membrane. The pure hydroxy-sodalite zeolite membrane synthesized by MARS method was found to be well inter-grown and the thickness of the membrane was 6-7 mum. Gas permeation results showed that the hydrogen/n-butane permselectivity of the hydroxy-sodalite zeolite membrane was larger than 1000. (C) 2004 Elsevier Inc. All rights reserved.

SOLVENT-EXTRACTION OF SC(III), ZR(IV), TH(IV), FE(III), AND LU(III) WITH THIOSUBSTITUTED ORGANOPHOSPHINIC ACID EXTRACTANTS

The solvent extraction of Sc(III), Zr(IV), Th(IV), Fe(III) and Lu(III) with Cyanex 302 (bis(2,4,4-trimethylpentyl)monothiophosphinic acid) and Cyanex 301 ( bis(2,4,4-trimethylpentyl) dithiophosphinic acid) in n-hexane from acidic aqueous solutions has been investigated systematically. The effect of equilibrium aqueous acidity on the extraction with these reagents was studied. The separation of Th(IV), Fe(III) and Lu(III) from Sc(III), or the separation of other metals from Lu(III) with Cyanex 302, can be achieved by controlling the aqueous acidity. However, Cyanex 301 exhibited a poor selectivity for the above metals, except for Lu(III). The extraction of these metals with Cyanex 272, Cyanex 302 and Cyanex 301 has been compared. The stripping percentages of Sc(III) for Cyanex 302 and Cyanex 301 in a single stage are near 78% and 75% with 3.5 mol/L and 5.8 mol/L sulphuric acid solutions, respectively. The effects of extractant concentration and temperature on the extraction of Sc(III) were investigated. The stoichiometry of the extraction of Sc(III) with Cyanex 302 was determined. The role of different components of Cyanex 302 in the extraction of Sc(III) was discussed.

微量样品钕-锶-铅同位素分析方法在黄河下游悬浮颗粒物及沉积物的应用

Aim in Rb-Sr-REE-Pb isotopic analysis of river material, a single-stage, highly efficient and rapid chemical separation method of Rb-Sr-REE-Pb has been established by a combination of the SR special resin and the RE resin. At the same time, Feasibility of high precision analysis on micro-size Nd samples，which were chemically separated by using the LN resin, were systematicly studied using the NdO+ technique in thermal ionization mass spectrometer (TIMS). Results show that high precision measurement of Nd isotopic ratios can be successfully achieved on micro-sample of 1 ng size lever, by systematic experiments on isobar interferences and optimizing separation and measurement conditions. This method will greatly extend the application prospect of the NdO+ technique. Sr-Nd-Pb isotopic composition of suspending particle material (SPM) and sediment and Sr isotopic composition of river water in the low reaches of the Yellow Rriver have been systematically analysed in this study. Results can indicate followings: (1) relative stable Sr isotopic ratios around 0.7112 of river water suggest great influcence from dissolution of carbonate component of loss material on Sr isotopic composition of river water; (2) Nd isotopic compositions of SPM and sediment of the Yellow river are is similar, mean εNd value of SPM around -11.5 and mean εNd value of sediment -12.7, slightly lower than that of SPM. Nd isotopic composition of the Yellow River material is simarlar to or slightly lower than loss material (-9.5); (3) evidence of Sr and Pb isotopic compositions of both SPM and sediment reveals a mixing trend of two endmembers. Sr isotopic ratios of SPM after leaching are significantly different that those without leaching, possibly suggesting strong alteration of river water. Pb isotopic ratios of SPM remain unchangable after leaching compared with unleached SPM; (4) Pb-contents of SPM are commonly higher than those of sediments, while Pb isotopic ratios of SPM are significantly lower. Pb isotopic composition of the Yellow River is relatively constant, which can be a useful provenance indicator between the Changjiang and Yellow Rivers.

Measurement of Microscopic Deformation in a Cualni Single Crystal Alloy by Nanoindentation with a Heating Stage

Thermally induced recovery of nanoindents in a CUAINi single crystal shape memory alloy was studied by nanoindentation in conjunction with a heating stage. Nanoindents formed by a Berkovich indenter at room temperature were heated to 40, 70 and 100 degrees C. Partial recovery was observed for the nanoindents. The recovery ratio depended on the heating temperature. Indentation of CuAlNi can induce inelastic deformation via dislocation motion and a stress-induced matensitic transformation. The percentages of dislocation-induced plastic strain would affect the thermal deformation of CuAlNi, because the induced dislocations could stabilize stress-induced martensite plates even when the temperature above austenite finish temperature, A(f). When the applied indentation load is low (less than 10,000 mu N), the shape recovery strain is predominant, compared with the dislocation-induced plastic strain. Therefore, the degree of indent recovery in the depth direction, delta(D), is high (about 0.7-0.8 at 100 degrees C).

Functional analysis of FP25K of Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus

The fp25k gene of Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus (HearNPV) was studied. HearNPV fp25k gene transcription was found starting from about 18 h post-infection, and protein could be detected from the same time with antiserum against FP25K. To study the function of HearNPV fp25k, a recombinant HearNPV (HaBacWD11) with an enhanced green fluorescent protein (GFP) gene replacing the fp25k was constructed using HaBacHZ8, a bacmid of HearNPV that lacks the polyhedrin gene. Growth curve analysis showed that HaBacWD11 produced higher titres of budded viruses (BVs) than its wild-type counterpart HaBacHZ8-GFP. Electron microscopic analysis indicated that at the late stage of infection, the number of intranuclear enveloped nucleocapsids in HaBacWD11-infected cells was much less than that of HaBacHZ8-GFP. A rescue recombinant virus HaBacWD14 was constructed by reintroducing fp25k gene into HaBacWD11. The growth curve and electron microscopic analysis of the rescued recombinant confirmed that the increase of BV yield and the decrease of the virion production in infected cells were the result of fp25k deletion. The expression of membrane fusion protein (Ha133) and ODV-E66 were studied using the FP25K mutants HaBacWD11 and HaBacHZ8-GFP. Unlike FP25K mutants in Autographa californica multicapsid NPV (AcMNPV), which caused an increase in the expression of membrane fusion protein GP64 and a decrease of ODV-E66, no obvious changes at the expression level of Ha133 and ODV-E66 were observed in HearNPV FP25K mutant.

Photoluminescence studies of GaAs/AlGaAs single quantum well intermixed by Ga+ ion implantation

Ga(+)ion implantation followed by rapid thermal annealing (RTA) was used to enhance the interdiffusion in GaAs/AlGaAs single Quantum Wells(SQWs). The extent of intermixing was found to be dependent on the well depth, number of implanted ions and annealing time. A very fast interdiffusion process occurs at the initial annealing stage. After that, the enhanced diffusion coefficient goes back to the umimplanted value. We propose a two-step model to explain the diffusion process as a function of the annealing time : a fast diffusion process and a saturated diffusion process. The interdiffusion coefficient of the fast diffusion was found to be of well depth dependence and estimated to be in the range of 5.4x10(-16) similar to 1.5x10(-15)cm(2)s(-1). Copyright (C) 1996 Published by Elsevier Science Ltd