Forebody Compressibility Research of Hypersonic Vehicle

Three kinds of forebody model of hypersonic vehicles were studied with numerical simulation method. It shows that the two- order compressive ramp model is the best selection among the three for its good evaluative parameters value at the cowl of the inlet . This model can provide higher value of flux coefficient and total pressure recovery coefficient and lower average Mach number compared with those of the other two models . Simultaneously different compressive angles may have different effects . The configuration which the firstorder of compressive angle is 4°and the second 5°is the optimum combination. Furthermore factors such as attack angle were concerned. Better result may be obtained with a range of attack angles . Based on the work above the integrated design for forebodyPinlet of a hypersonic vehicle was performed. The numerical result shows that this integrated model provides good flow field quality for inlet and engine work.

Relay lens-free birefringence-customized stackable beam-steering modules for optical interconnects

A previously suggested birefringence-customized modular optical interconnect technique is extended for lens-free relay operation. Various lens-free relay imaging models are developed. We claim that the lens-free relay system is important in simplifying an optical interconnect system whenever the imaging conditions permit. To verify the validity of various proposed concepts, we experimentally implemented some 8 x 8 optical permutation modules. High-power efficiency and low channel cross talk were experimentally observed. In general, the larger the channel spacing, the less the cross talk. A quantitative cross-talk measurement of the lens-free relay system shows that, for a fixed channel width of 0.5 mm and channel spacings of 0.5, 1, and 2 mm, a less than -20-dB cross-talk performance can be guaranteed for lens-free relay distances of 40, 280, and 430 mm, respectively. (C) 1998 Optical Society of America.

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 10-bit 2GHz current-steering CMOS D/A converter

This paper presents a 2GS/s 10-bit CMOS digital-to-analog converter (DAC). This DAC consists of a unit current-cell matrix for 6MSBs and another unit current-cell matrix for 4LSBs, trading off between the precision and size of the chip. The Current Mode Logic (CML) is used to ensure high speed, and a double Centro-symmetric current matrix is designed by the Q(2) random walk strategy in order to ensure the linearity of the DAC. The DAC occupies 2.2 x 2.2 mm2 of die area, and consumes 790mw at a single 3.3V power supply.

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).

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 12bit 300MHz Current-Steering CMOS D/A Converter

The proposed DAC consists of a unit current-cell matrix for 8MSBs and a binary-weighted array for 4LSBs, trading-off between the precision, speed, and size of the chip. In order to ensure the linearity of the DAC, a double Centro symmetric current matrix is designed by the Q2 random walk strategy. To achieve better dynamic performance, a latch is added in front of the current switch to change the input signal, such as its optimal cross-point and voltage level. For a 12bit resolution,the converter reaches an update rate of 300MHz.

低β四分之一波长腔中的束流偏转的分析性研究(英文)；Analytical Study on Beam Steering in Low-β Superconducting Quarter Wave Resonators

目前加速速度范围在0.01c—0.3c的粒子的超导腔主要使用四分之一波长腔型。用于不同加速器上的频率范围在50—240MHz的四分之一波长腔在建造或者预研中。这种腔型的一个不足是其横向电磁成分会造成束流偏转效应,从而导致发射度的增长和束流的溢漏,在强流重离子加速器中这种效应尤为严重。对中国科学院近代物理研究所超导直线加速器中的频率为80.5和161MHz的四分之一波长腔的偏转效应进行了分析,计算结果表明,在四分之一腔体的设计时需要考虑到束流偏转的修正,这通常需要在漂移管端面上削适当大小的倾角来实现。

Counterions in polyelectrolyte multilayers: A vehicle for introducing functionalities

Counterions present at the surface of polyelectrolyte multilayers were utilized for the introduction of charged species into the multilayer via ion exchange. A typical polyelectrolyte multilayer film with Na+ counterions in the outermost layer was immersed in an AgNO3 aqueous solution and the rapid ion-exchange process was complete within 1 min. The silver ions thus introduced were then reduced in situ and silver nanoparticles were produced at the surface of the multilayer assembly. This example demonstrates that the counterions naturally occurring in every polyelectrolyte multilayer film can be a convenient vehicle for the introduction of various functionalities to the film.

Multi-sensors data acquisition and information fusion for manned submersible vehicle

本文介绍了一种用于载人潜水器的导航传感器的数据采集及信息融合技术。航行控制计算机通过基于工业以太网的数据通信系统对各传感器进行数据采集,采用卡尔曼滤波器完成对各传感器数据信息的融合,以便提高数据的精度和控制系统的性能,并将结果送给监控计算机,用于载人潜水器的姿态显示。

履带式移动机器人行动规划技术的研究

本文以８６３－５１２型号项目为背景，从运动特性、运动描述、运动控制以及运动规划等几个方面研究履带式移动机器人的行动规划技术；首先从理论上分析了履带式移动机器人的内在运动传递机理，指出了其区别于轮式移动载体的独特的运动特性，尤其是在其转向特性方面，得出了履带式移动机器人运动角速度几乎不可控原理、原地转弯转不准问题、以及履带式车辆行动规划时所要遵循的规则等重要结论，针对履带式移动机器人的纵向运动控制问题，讨论了其速度控制模型，提出了一种速度测量与控制的简单、准确、可靠的方法。在磺向运动方面，提出了一种基于ＦＭ－ＬＩＫＥ和ＡＭ－ＬＩＫＥ相结合的复合控制技术，解决了难度较大的方向控制问题。最后提供了实验结果，证明了上述方法与结论的正确性。上述方法与结论，作为８６３－５１２某型号任务的一部分，业已通过验收。