北电网络安全路由技术

北电网络提供的Contivity解决方案不仅可以使用户建立各种类型的VPN，而且还可以把这些VPN集成到未来的融合话音和数据的网络中。该方案已实现了安全路由选择；可通过多种技术支持鉴权功能，从而实现安全接入；允许用户使用其各自的安全性配置文件设置；其设计中没有“后门”，重点介绍了Contivity 2700网关的主要特征及其优势。     

Effects of hydrogen addition on the high temperature deformation behavior of TC21 titanium alloy

The true stress-strain curves of TC21 titanium alloy charged with up to 0.7 wt.% hydrogen were obtained by the isothermal hot compression tests which were carried out on an Instron 5500 machine at 1023 to 1223 K and 0.001 to 0.1 s⁻¹. The dependence of the steady state flow stress on hydrogen content was determined. The results showed that with the increase of hydrogen content flow stress decreased at lower hydrogen content and then increased at higher hydrogen content. Suitable hydrogen addition can significantly decrease the flow stress and improve the hot workability of TC21 titanium alloy. The flow stress behaviors and the dependence of hydrogen content on flow stress were clarified by microstructural observation. The optimum hydrogen content at different deformation temperature was determined.     

硼化物原位自生增强TiAl基复合材料的组织演化、热变形行为及加工工艺设计（英文）

硼元素添加造成的相转变和硼化物析出等因素会对原位TiAl基复合材料显微组织演化及热变形行为产生影响。利用等温压缩实验、扫描电子显微技术以及透射电子显微技术等研究材料的动态再结晶和动态回复机制,并计算出其表现变形激活能为691.506 k J/mol。在1100～1200℃温度区间,再结晶γ和α晶粒的形核长大分别主导α₂→α相转变温度上、下的热变形行为。α相的动态回复主导材料在1250℃低应变速率下的热变形行为;同时,硼元素会提高α相含量,降低γ→α和α₂→α相转变温度,进而促进加载过程中回复α相晶粒的形核长大。根据新建的本构模型,对TiAl基复合材料的变形机制和加工工艺进行详细阐述.     

WCDMA中LMS自适应天线阵的硬件实现

本文针对WCDMA的特点设计了一种利用LMS算法的自适应天线阵。实现时DSP采用TI公司的TMS320C6701,并采用了零中频I/Q调制解调技术,工作于1.95GHz。该天线阵结构简单,复杂度低。     

Standby supply voltage minimization for deep sub-micron SRAM

Suppressing the leakage current in memories is critical in low-power design. By reducing the standby supply voltage (V_DD) to its limit, which is the data retention voltage (DRV), leakage power can be substantially reduced. This paper models the DRV of a standard low leakage SRAM module as a function of process and design parameters, and analyzes the SRAM cell stability when V_DD approaches DRV. The DRV model is verified using simulations as well as measurements from a 4 KB SRAM chip in a 0.13 μm technology. Due to a large on-chip variation, DRV of the 4 KB SRAM module ranges between 60 and 390 mV. Measurements taken at 100 mV above the worst-case DRV show that reducing the SRAM standby V_DD to a safe level of 490 mV saves 85% leakage power. Further savings can be achieved by applying DRV-aware SRAM optimization techniques, which are discussed at the end of this paper.     

利用51单片机实现对激光器电流的精度控制

讨论了一种大功率半导体激光控制器的设计方案,能够对激光器提供一个稳定的受控电流,并能实时监视、控制激光器的温度,以达到保护激光器的目的。主控器采用MCS-51单片机来实现对整个系统的精确控制,对电流的监控达到毫安级,温度可达0.1℃。激光二极管热电制冷器驱动电路采用高效、大功率H桥驱动集成块DRV592。与当前普遍采用分立元件设计相比,简化了80%的设计。     

A spectrophotometric method for quantitative determination of xylose in fermentation medium

Monitoring the consumption of sugars during fermentation is a key to optimizing product formation and maintaining a healthy environment for microorganisms. Difficulty arises in the availability of a rapid, inexpensive and sensitive method for the detection of sugars because fermentation media are a complex mix of nutrients, cell debris, waste and target products. A method involving reaction-based UV-Vis spectrophotometry for the quantitative determination of xylose as the target sugar was developed. Factors affecting xylose concentration measurements such as hydrochloric acid concentration, heating time and the amount of Fe³⁺ catalyst were investigated. A continuous scan revealed the working wavelength to be 671 nm. The effect of other components in the fermentation broth was found to be negligible. Absorbance shows a linear relationship with xylose concentration within a range of 0.1-0.5 g/L. Xylose concentrations from fermentation samples obtained at specific time intervals (0-168 h) were determined with the method and compared with YSI 2700, an enzyme electrode, HPLC-ELSD method, currently a common technique for measuring xylose and GC aldononitrile sugar derivatization method. Dilution is necessary for comparable xylose concentrations with YSI 2700 and HPLC-ELSD. Xylose concentration measurements obtained with the UV-Vis spectrophotometric method although quantitatively comparable to HPLC-ELSD xylose measurements were easily and conveniently obtained compared to YSI 2700, HPLC-ELSD and GC derivatization methods.     

RXL8-2700型重锤脉冲震源性能分析

RXL8-2700型重锤脉冲震源,集机械、液压、电控为一体。本文简要介绍了其工作原理,同时结合野外采集情况,从同步精度、出力、资料品质等方面系统地分析了其性能。分析结果显示,RXL8-2700型重锤脉冲震源能够作为井炮震源的补充震源,满足村庄、学校、教堂等一些敏感区域施工的HES要求。     

电机驱动芯片DRV8823在XBT自动投放系统中的应用

DRV8823是TI公司推出的4H桥电机驱动芯片。在介绍XBT自动投放系统应用背景的基础上,阐述了系统使用的电机驱动芯片DRV8823的组成、应用原理和软硬件实现方案,并给出了软件流程和部分关键代码。最后,叙述了DRV8823在工程应用中的价值和意义。     

Effect of powder preparation technology on the hot deformation behavior of HIPed P/M nickel-base superalloy FGH96

In this paper, the hot deformation characteristics of P/M nickel-base superalloy FGH96 prepared by different powder preparation technologies were studied in the deformation temperature range from 1000 °C to 1100 °C and the strain rate range from 0.001 s⁻¹ to 1 s⁻¹ using hot compression tests. The peak stress vs. deformation temperature curves and the peak stress vs. strain rate curves were established, respectively. The results show that the specimens prepared by plasma rotation electric pole (PREP) powder were more sensitive to deformation temperature and strain rate. On the basis of the dynamic material model, the processing maps for hot working were developed. The activation energies and Zener-Hollomon parameters were obtained by linear statistical regression method. For the specimens prepared by PREP powder, the peaks of power dissipation mainly located in lower temperature domain (1000-1030 °C), and the efficiencies of power dissipation (EPD) obtained in the strain range from 0.1 to 0.7 were essentially similar. This indicated that strain had a slight influence on processing maps. For the specimens prepared by argon atomization (AA) powder, the effects of strain on EPD and instability domains were significant. The lower activation energies and Z values indicated that the workability of the specimens prepared by AA powder is better than that prepared by PREP powder. Moreover, it was found that effects of the heat treatment time on activation energy and Zener-Hollomon parameter were significant. With the increase of heat treatment time, the dislocation density and the volume fraction of precipitation phase gradually decreased. Microstructural observation demonstrated that the phenomenon of recrystallized grains coarsening existed in the specimens prepared by longer heat treatment time. The heat treatment time of the specimens prepared by AA powder should be appropriately shortened in order to prevent recrystallized grains coarsening.