低温度系数标准电阻器的研制

主要介绍了低温度系数标准电阻器的研制,包括采用的电阻合金材料、电阻合金材料的筛选、匹配与加工制作,低温度系数标准电阻器的技术参数、温度系数测量方法,减小温度系数采用的补偿方法,测试结果分析。     

A comprehensive study of the 2016 Mw 6.0 Italy earthquake based on high-rate (10 Hz) GPS data

The 2016 M_w 6.0 Italy earthquake is successfully recorded by the near-field 10?Hz GPS and 200?Hz Strong Motion (SM) stations, providing valuable data for this study. A comprehensive study of this earthquake is carried out based on GPS data, which contains coseismic deformations analysis, noise analysis, seismic wave picking, and magnitude determination. The noise of most GPS-derived displacement waveforms can be described as a combination of white noise, flicker noise, and random walk noise after the earthquake occurrence, and the spectral indices vary significantly for most stations, implying that the seismic signals have affected the noise characteristic of GPS-derived displacement waveforms. S-transform is employed to assess the GPS capability to detect the seismic arrival time. The SM station AMT and the GPS station AMAT are in good agreement in seismic wave picking, and the difference is only 1.2?s in the north component, suggesting that the outcome of seismic wave picking using GPS data is reliable. Then, a classic empirical formula is employed to determine the moment magnitude. A robust moment magnitude (Mw 5.90) can be estimated by the nine GPS stations with about 23.9?s. If four GPS stations near the epicenter is chosen to determine the magnitude, it only take 13.0?s to retrieve a reliable preliminary (Mw 5.82) magnitude, which is 5.4?s ahead of nine stations. In addition, Cross Wavelet Transform (XWT) is adopted to measuring the correlation and phase relationship between GPS and SM records. The result of XWT analysis indicates 10?Hz GPS is capable of capturing reliable and accurate coseismic dynamic deformations, as evidenced by the XWT-based semblance being close to 1 between GPS and SM records. The above results confirm the capability of 10?Hz GPS to capture coseismic dynamic deformations, detect seismic arrival time, and determine earthquake magnitude. Moreover, rapid magnitude determination based on 10?Hz GPS data can be regarded as an important supplement to Earthquake Early Warning (EEW).     

一种温度动态调节方法及其动态性能仿真研究

航空气源模拟试验台主要用于模拟不同飞行状态时发动机给空气管理系统的供气,由于飞机爬升、降落时发动机供气参数会急剧变化,因此航空气源模拟试验台需具备动态能力.基于一种温度动态调节方法,在合理简化的基础之上采用NHT方法对其温度动态性能进行了仿真研究,仿真结果表明该温度动态调节方法能够满足温度动态性能需求,对动态航空气源模拟试验台的设计选型有较高的参考价值.     

Spectroscopy peculiarities of thermal plasma of electric arc discharge between electrodes with Zn admixtures

Plasma of the free burning electric arc between Ag–SnO₂–ZnO composite electrodes as well as brass electrodes were investigated. The plasma temperature distributions were obtained by Boltzmann plot method involving Cu I, Ag I or Zn I spectral line emissions. The electron density distributions were obtained from the width and from absolute intensity of spectral lines. The laser absorption spectroscopy was used for measurement of copper atom concentration in plasma. Plasma equilibrium composition was calculated using two independent groups of experimental values (temperature and copper atom concentration, temperature and electron density). It was found that plasma of the free burning electric arc between brass electrodes is in local thermodynamical equilibrium. The experimental verification of the spectroscopic data of Zn I spectral lines was carried out.     

Grinding temperature and energy ratio coefficient in MQL grinding of high-temperature nickel-base alloy by using different vegetable oils as base oil

Vegetable oil can be used as a base oil in minimal quantity of lubrication(MQL). This study compared the performances of MQL grinding by using castor oil, soybean oil, rapeseed oil, corn oil, sunflower oil, peanut oil, and palm oil as base oils. A K-P36 numerical-control precision surface grinder was used to perform plain grinding on a workpiece material with a high-temperature nickel base alloy. A YDM–III 99 three-dimensional dynamometer was used to measure grinding force,and a clip-type thermocouple was used to determine grinding temperature. The grinding force, grinding temperature, and energy ratio coefficient of MQL grinding were compared among the seven vegetable oil types. Results revealed that(1) castor oil-based MQL grinding yields the lowest grinding force but exhibits the highest grinding temperature and energy ratio coefficient;(2) palm oil-based MQL grinding generates the second lowest grinding force but shows the lowest grinding temperature and energy ratio coefficient;(3) MQL grinding based on the five other vegetable oils produces similar grinding forces, grinding temperatures, and energy ratio coefficients, with values ranging between those of castor oil and palm oil;(4) viscosity significantly influences grinding force and grinding temperature to a greater extent than fatty acid varieties and contents in vegetable oils;(5) although more viscous vegetable oil exhibits greater lubrication and significantly lower grinding force than less viscous vegetable oil, high viscosity reduces the heat exchange capability of vegetable oil and thus yields a high grinding temperature;(6) saturated fatty acid is a more efficient lubricant than unsaturated fatty acid; and(7) a short carbon chain transfers heat more effectively than a long carbon chain. Palm oil is the optimum base oil of MQL grinding, and this base oil yields 26.98 N tangential grinding force,87.10 N normal grinding force, 119.6 °C grinding temperature, and 42.7% energy ratio coefficient.     

基于中介理论与交通特性的终端区态势评价

终端区交通态势的准确度量是制定并实施流量管理措施的重要依据之一。通过提取终端区宏观与微观的交通特性,从进离场及总量3个维度构建态势的指标描述,并进一步采用中介理论中的真值程度度量与熵权法建立了一种客观的终端区飞行区交通态势模糊综合评价方法,实现客观、准确的交通态势判别与样本间量化比较。选取国内典型繁忙终端区的实测数据,验证了评价方法与特性指标的有效性。     

柴油发动机热管理系统的高度特性

基于空中和高原环境的特点,研究了柴油发动机散热器传热性能的高度特性;进一步建立了发动机热管理系统的流动和传热模型,研究了热管理系统的高度特性;给出了基于最小功耗原则的热管理系统运行参数匹配方法.在固定系统热负荷条件下的计算结果表明:随着海拔高度的增加,在空中环境下,散热器的散热性能先上升后下降,热管理系统中冷却液和润滑油温度先下降后上升,热管理系统所需的最小功耗先减小后增加;在高原环境下,散热器的散热性能随高度增加大幅下降,热管理系统中冷却液和润滑油温度大幅上升,发动机出现过热问题,为了给发动机提供足够的散热能力,热管理系统所需要的最小功耗随着海拔高度的增加而大幅增加.      

液化天然气作为航空燃料的发展趋势及特点分析

为研究液化天然气(LNG)作为航空燃料的可行性,对LNG的特点、发展趋势及作为航空燃料存在的问题进行了分析.采用了横向比较的方法,将LNG与新的航空替代燃料和传统航空燃料进行了比较和计算分析.结果表明:与新的航空替代燃料相比,LNG具有来源广泛、经济性好、发动机适应性强等优点.与传统航空燃料相比,LNG的储量大,可使用100年以上;可燃极限宽、污染物排放低,NOx排放仅为航空煤油的1/4;单位质量能量密度高、成本低,其燃料成本仅为航空汽油的一半,航空煤油的1/3;同时还具有可用于发动机高温部件冷却用的冷能,是一种极富潜力的航空燃料.指出在LNG作为航空燃料方面急需开展动力系统与飞机结构的匹配、燃料相态的有效转化及不同燃料在燃烧室内的反应特性等方面的研究工作.      

温度对飞机燃油射流泵工作特性影响

建立了射流泵数学模型,采用数值计算方法对其工作特性进行了模拟,搭建了实验台,采用RP-3燃油,通过实验数据验证了模型的正确性.在此基础上,分别选择了RP-3和JET-A两种燃油,计算了从-40℃~40℃温度下,不同操作压力对射流泵流量比的影响.结果表明:燃油温度高于0℃时,温度对射流泵工作特性影响并不明显,随着温度的降低,射流泵性能与标准温度下（20℃）偏差越来越大,且压比越高此偏差越明显.当温度高于0℃时,采用RP-3和JET-A燃油性能相差不大,RP-3燃油性能略优于JET-A燃油,但是在低温下,RP-3燃油性能远高于JET-A燃油.因此当燃油温度较低且压比较高时,必须充分考虑温度对射流泵特性的影响.      

Al/Ni含能多层膜在Al2O3陶瓷/不锈钢焊接中的应用

采用磁控溅射设备,生长AuSn合金做焊料层、Al/Ni含能多层膜做热量提供层,实现了不锈钢和Al_2O_3间的异质材料自蔓延高温扩散焊。利用SEM、XRD和DSC等测试手段表征AuSn合金和Al/Ni含能多层膜的微观形貌、相成分和放热量;用万能试验机测试焊接接头的力学性能。结果表明,AuSn合金的质量比基本达到80∶20,而多层膜的层状结构清晰,反应热达到1 239 J/g。焊接实验结果表明,仅使用AuSn焊料时,剪切强度仅为46 MPa,在增加Al/Ni含能多层膜后,其剪切强度可达90 MPa,强度提高了约一倍。焊接接头的界面显微形貌和相结构研究表明,剪切强度的增强主要是Al/Ni多层膜提供了额外能量使得界面处的反应剧烈,陶瓷金属化层与中间层的反应加剧,形成了新的反应生成物。