高场磁体用RRP Nb3Sn股线的研制

采用Rod Restack Process(RRP)研制了单根线长大于1500m的高场磁体用Nb3Sn股线,股线选用Nb作为扩散阻隔层,分布于各亚组元周围。在热处理时Nb阻隔层不但可以阻止Sn向稳定体Cu区的扩散,防止稳定体的Sn扩散污染,确保股线具有较高的剩余电阻率(RRR),同时,靠近Sn源内侧的Nb参与固态扩散反应生成A15相Nb3Sn,贡献临界电流。在股线的制备过程中,采用Nb-47%Ti(质量分数)芯代替部分Nb芯的方式添加元素Ti,达到了Ti元素添加目的,该方法因为使用了已经商业化的Nb-47%Ti而有效控制了制作成本。对该股线进行热处理以及超导性能测试研究表明:640℃,60h热处理条件下,股线在12T,4.2K,0.1μV/cm下的Ic为514A,股线的RRR为148,具有良好的绝热稳定性;在650℃,100h下股线的Ic为599A,RRR=3.77。股线扩散阻隔层以及添Ti方式的成功选择,为获得长线打下了基础,为股线性能的初步研究及后续的实验提供了直接参考。     

Design of RT Equal Channel Angular Pressing Pure Titanium Workpiece by Finite Element Simulation

为了优化室温下等通道转角挤压纯钛工件的几何形状,采用三维有限元软件模拟了纯钛工件的变形行为。通过对比分析工件形状和尺寸对损伤因子、挤压力以及剪切带处应变速率分布等参数的影响,获得了工件最佳几何形状。仿真结果表明,方条形工件的损伤因子大于圆棒型工件,且高于纯钛材料的临界损伤因子,表明方条形工件不利于变形,易产生表面裂纹。3D模拟结果表明,直径为15 mm的圆棒型工件具有最小的损伤因子,适中的挤压载荷以及相对均匀的应变分布。依据仿真结果提供的最佳工件,即直径为15 mm的圆棒型工件,室温下成功挤压出直径15 mm的纯钛圆棒。挤压后样品截面上硬度分布均匀,与3D仿真所预示的均匀应变分布相一致。     

丰田3.8L轿车曲轴淬火裂纹分析

对丰田3.8L曲轴裂纹进行了形貌及能谱分析。结果表明,裂纹为淬火裂纹,主要原因是由于铸造时铁水均匀性差,元素沿晶界偏析,造成大量残留奥氏体和网状渗碳体。沿残留奥氏体晶界分布的网状渗碳体对基体起割裂作用;淬火冷却后期和回火时仍然有残留奥氏体转化为马氏体,曲轴体积发生膨胀,使表面承受过大的张应力,当张应力超过材料强度时,导致工件表面开裂。     

Influence of Mg Contents on Aging Precipitation Behavior of Al-3.5Cu-xMg Alloy

The influence of Mg content on the microstructures and mechanical properties at room temperatures of Al-3.5Cu-(0.71-1.81)Mg alloys was studied.Precipitation phases in the alloys were identified by TEM and HRTEM.The results show that when Mg contents increase from 0.71 to 1.81 wt%,the precipitates are transformed from S,S″,Ω,and θ' phases to Sand S′phases,and Ω phase is first observed in Al-3.48Cu-0.71 Mg alloy with Cu/Mg mass ratio of 5 during the conventional aging heat treatment(190 ℃/12 h).Regard to aging hardness effect of the tested alloys,the hardness of the alloys improves with the increase of Mg content,but the increases become slow when Mg content is greater than 1.35 wt%.     

Ni-GDC阳极的制备及其孔隙率研究

采用缓冲溶液法制备出NiO—GDC复合粉末，该粉末压制、烧结后再经氰气气氛还原得到Ni—GDC金属陶瓷阳极。使用XRD，TEM，SEM对NiO—GDC和Ni—GDC的物相、形貌进行了观察分析，测定了阳极还原前后的相对密度、总孔隙率及开孔隙率。实验结果表明，由于NiO转变为Ni，有O的火上，使得还原后试样的相对密度明显下降，而孔隙率由15．4％提高到29．6％，且开孔隙率达到23．1％，可满足阳极作为燃料扩散通道的作用。多孔结构的Ni—GDC金属陶瓷阳檄有望成为中混固体氧化物燃料电池的阳极材料。     

一种基于经验模式分解的结构损伤预警方法

提出了一种基于经验模式分解的结构损伤预警方法。首先,将结构反应信号用经验模式分解方法分解成一系列固有模态函数;然后,利用固有模态函数在结构损伤前后的能量分布变化来表征结构因损伤引起的动力特性改变;最后,计算结构的损伤预警指标。应用该方法对健康监测Benchmark模型结构进行分析,采集模型在锤击激励下结构损伤前后的动力响应,计算了结构损伤预警参数及其损伤预警指标。试验数据分析表明,基于经验模式分解的结构损伤预警指标具有良好的损伤预警能力,能够准确地判断结构初期损伤的发生。     

根据水区压力变化特征辨识高含硫边水气藏水侵规律

高含硫气藏产地层水严重影响生产,其安全清洁开发要求准确掌握水侵规律。储层非均质性强的边水气藏通常在某些方向水侵强度更大,表现出局部活跃水侵特征。经典水驱物质平衡分析方法基于全气藏平均地层压力进行计算分析,对局部水侵动态敏感性弱,早期研判和预测这类水侵影响较困难。为此,以水侵通道上水区观察井压力变化分析为重点,研究形成了诊断水侵特征、估算气藏开发全过程潜在水侵量大小的方法。与过去利用靠近水侵前缘的生产气井压力恢复数据分析局部水侵特征方法比较,围绕观察井录取动态资料作分析对气藏生产影响小且测压数据几乎不受生产制度变化的干扰。结论认为,多种方法配合能深入认识水侵规律,增强气藏开发治水提高采收率的针对性。     

A novel covert speech communication system and its implementation

In this paper, a Covert Speech Telephone （CST） is designed and implemented based on the information hiding technique, which works on the internet. To solve the large embedding capacity problem for real-time information hiding, a steganographic system combined with a watermarking scheme is proposed, which skillfully transfers the secret speech into watermarking information. The basic idea is to use the speech recognition to significantly reduce the size of information that has to be transmitted in a hidden way. Furthermore, an improved DFT watermarking scheme is proposed which adaptively chooses the embedding locations and applies the multi-ary modulation technique. Based on the GUI （Graphical User Interface） software, the CST operates on both ordinary and secure mode. It is a completely digital system with high speech quality. Objective and subjective tests show that the CST is robust against normal signal processing attacks and steganalysis. The proposed scheme can be used in terms of military applications.     

钛合金仿莲房特征芯体夹层结构钎焊组织与性能

针对TC4钛合金仿莲房特征芯体与面板钎焊工艺,采用TiZrCuNi钎料,开展了钎焊工艺研究,并分析了主要钎焊工艺参数对钎焊界面组织和夹层结构力学性能的影响。结果表明：钎焊温度920℃,保温时间90min时, TC4钛合金仿莲房特征芯体夹层结构钎焊后界面焊合率良好,界面显微组织为均匀针状α组织和界面金属间化合物,夹层结构平压强度均值为15.14MPa。钎焊保温时间对TC4钛合金仿莲房特征芯体钎焊界面显微组织影响显著,当钎焊保温时间较短时(15min),钎料熔化后,液态钎料中Cu和Ni元素与母材反应时间较短,钎料中Cu和Ni向母材中的扩散反应不充分,钎缝区局部Cu和Ni元素富集导致Cu和Ni元素含量超过共晶成分点,钎焊保温结束后液态钎缝凝固时发生共晶反应,生成块状金属间化合物,钎焊界面主要为含有块状金属间化合物的凝固钎料组织和针状α组织;随着钎焊保温时间的增加,液态钎料中Cu和Ni元素与母材反应时间增加,钎料中Cu和Ni元素向母材中扩散反应深度显著增加,从而Cu和Ni元素在液态钎料中的含量显著降低,元素含量小于共晶成分点,钎焊保温结束后液态钎缝凝固时Cu和Ni元素固溶于β相中,避免大量块状金属化合物生成,随后β相向α相的固态相变时,共析反应生成针状α相,在针状α组织界面处生成金属间化合物。钎焊时间保温时间从15min升至90min时,由于钎焊界面金属间化合物减少,TC4钛合金仿莲房特征芯体夹层结构的平压强度逐渐增加。     

DESIGN OF TERNARY CURRENT-MODE CMOS CIRCUITS BASED ON SWITCH-SIGNAL THEORY

By applying switch-signal theory, the interaction between MOS transmission switch-ing transistor and current signal in current-mode CMOS circuits is analyzed, and the theory oftransmission current-switches which is suitable to current-mode CMOS circuits is proposed. Thecircuits, such as ternary full-adder etc., designed by using this theory have simpler circuit struc-tures and correct logic functions. It is confirmed that this theory is efficient in guiding the logicdesign of current-mode CMOS circuits at switch level.