谈谈对引进产品中通用基础标准的贯彻

介绍了对引进产品中通用基础标准在南飞公司的贯彻情况。     

参考交流电压标准的维护

计量标准的维护对量值传递质量是至关重要的,针对本系统最高交流电压计量标准,说明了维护方法及多年维护考核的结果,提出了计量标准的量值和计量标准量值的不确定度等与计量标准维护相关的概念。     

IS-95 CDMA前向同步信道仿真

分别对IS-95码分多址标准和SystemView软件进行了介绍,概述了IS-95前向同步信道的基本特点和性能参数,给出了采用SystemView软件仿真IS-95码分多址标准前向同步信道的方法和仿真结果。     

多因素组合下发射载体出管速度偏差预估方法

运用极限偏差、合成标准差、统计分析、蒙特卡洛仿真等多种预估方法,对发射载体出管速度偏差进行对比分析。分析结果表明,极限偏差法工程应用成熟,但预估结果偏于保守,适用于影响因素尚未认知完全的工程型号;对于影响因素比较明确的系统,运用统计分析法、合成标准差法得到的发射载体出管速度预估值一致性好,方法简单,且具有较高的准确性;蒙特卡洛法计算过程复杂,可通过大量仿真计算获取出管速度的分布特性,得到对应不同指标的分布概率,相比其他几种方法,计算结果更加科学、合理。工程型号应用时,可根据实际需要组合使用上述方法进行发射载体出管速度偏差预估分析。     

频率标准用超导铌腔内表面处理工艺研究

频率标准用超导铌腔内表面的处理是影响超导腔Q值的最大因素。本文首先通过理论分析确定了超导腔Q与表面剩余电阻的关系,其次通过一系列的表面处理工艺来保证超导腔内表面的剩余电阻尽量小,最后通过实验得到了超导腔的Q值为1.9E9,与理论计算结果相近,证明了表面处理的有效性。     

多元化实验教学评估方法的研究与应用

实验课程教学评估体系对实验课程教学的组织与实施具有很强的导向和质量监控作用，但现行的实验课程教学评估体系还不健全、不完善，因此在实验课程教学改革中要确立新的教学评估理念，制定科学的教学评估内容和标准，灵活运用多种评估方法，形成在新的教学评估观指导下的多元化实验课程教学评估方法，真正发挥评估体系服务教学、指导学习的积极反拨作用。     

Physiologic and metabolic responses of wheat seedlings to elevated and super-elevated carbon dioxide

The metabolic consequence of suboptimal (400 μmol mol⁻¹ or ppm), near-optimal (1500 ppm) and supra-optimal (10,000 ppm) atmospheric carbon dioxide concentrations [CO₂] was investigated in an attempt to reveal plausible underlying mechanisms for the differential physiological and developmental responses to increasing [CO₂]. Both non-targeted and targeted metabolite profiling by GC–MS and LC–MS were employed to examine primary and secondary metabolites in wheat (Triticum aestivum, cv Yocoro rojo) continuously exposed to these [CO₂] levels for 14, 21 and 28 days. Metabolite profile was altered by both [CO₂] and physiological age. In general, plants grown under high [CO₂] exhibited a metabolite profile characteristic of older plants under ambient CO₂. Elevated [CO₂] resulted in higher levels of phosphorylated sugar intermediates, though no clear trend in the content of reducing sugars was observed. Transient starch content was enhanced by increasing [CO₂] to a much greater extent at 10,000 ppm CO₂ than at 1500 ppm CO₂. The percentage increase of starch content resulting from CO₂ enrichment declined as plants develope. In contrast, elevated [CO₂] promoted the accumulation of secondary metabolites (flavonoids) progressively to a greater extent as plants became mature. Elevated [CO₂] to 1500 ppm induced a higher initial growth rate, while super-elevated [CO₂] appeared to negate such initial growth promotion. However, after 4 weeks, there was no difference in vegetative growth between 1500 and 10,000 ppm CO₂-grown plants, both elevated CO₂ levels resulted in an overall 25% increase in biomass over the control plants. More interestingly, elevated atmospheric [CO₂] reduced evapotranspiration rate (ET), but further increase to the supra-optimal level resulted in increased ET (a reversed trend), i.e. ET at 1500 ppm < ET at 10,000 ppm < ET at 400 ppm. The differential effect of elevated and super-elevated CO₂ on plants was further reflected in the nitrogen dynamics. These results provide the potential metabolic basis for the differential productivity and stomatal function of plants grown under elevated and super-elevated CO₂ levels.     

夹具质量对标准测力仪的影响

分析了用试验机进行力学性能检定过程中，夹具的质量对标准测力仪造成的影响，并通过分析原因，给出消除或减小这种影响的方法。     

Secondary instability of separated shear layers

The process through which a laminar flow undergoes transition to turbulence is of great fundamental and practical interest. Such a process is hugely complex as there are many diverse routes for a laminar flow to become turbulent flow. The transition process is usually initiated by flow instabilities—a primary instability stage followed by a secondary instability stage. This forms a rational framework for the early stage of a transition process and it is crucially important to understand the physics of instabilities leading to turbulence. This article reviews the results of studies on secondary instability of separated shear layers in separation bubbles and summaries the current status of our understanding in this area.     

网络分析仪时域测量技术综述

矢量网络分析仪直接测量两端口网络的微波特性，是射频微波测量领域中应用最广泛的仪器之一。网络分析仪时域技术在故障点定位、多路径消除、不连续性测试等应用中有着非常重要的意义，但是如何合理选取时域模式和设置参数是困扰工程研究人员的难点。本文对网络分析仪时域测量模式、离散数据取样、频率截断、窗函数、归一化等时域测量理论进行详细介绍，给出了时域测量范围和分辨力的计算方法，并以开路器的时域响应为例，说明了时域测量相关参数的设置依据。