一种离子聚合物金属复合材料拉伸试验研究

离子聚合物金属复合材料（IPMC）是一种新型的电致激活功能材料。为了研究IPMC的驱动特性,需要掌握其基本力学性能。通过化学镀方法,在一种与Nafion 117相似的离子交换膜表面镀金属铂（Pt）,制备了IPMC拉伸试样;测定了不同含水量情况下,IPMC试样尺寸的变化;通过拉伸试验和扫描电镜（SEM）形貌观察,研究IPMC含水量与拉伸性能之间、含水量与弹性模量之间的变化关系。研究表明：在聚合物基底溶胀状态下,试样各向尺寸变化相同,IPMC的弹性模量随其含水量的增加而降低,呈幂指数趋势下降;针对表面金属（Pt）镀层厚度为5~20 μm的IPMC试样,表层金属产生龟裂,且Pt元素在厚度方向上分布不均匀,若仍采用层合板理论对其弹性模量进行预测,将导致较大的误差。本文结果可为IPMC的力学建模、失效形式等研究提供有益的参考。     

飞机滑行下道基动静模量相关分析模型

为了建立飞机滑行下道基动静模量相关分析模型,结合飞机滑行下道基应力水平、典型道基压实度和含水率范围、飞机滑行时常见频率区间,通过动静三轴试验分析了应力水平、压实度、含水率和频率对道基动静模量的影响规律,发现动静模量均与压实度和围压成正相关,与含水率成负相关,其中动模量在频率低于3 Hz时变化较为显著;同时借助动静模量试验数据,建立并验证了基于多因素的飞机滑行下道基动静模量相关分析模型,为机场场道工程设计和检测提供参考。      

低烟耐烧蚀聚氨酯弹性体力学性能的研究

以1,6-六亚甲基二异氰酸酯(HDI)、聚氧化丙烯多元醇(PPG)、3,3/-二氯-4,4/-二氨基二苯甲烷(MOCA)为原料合成了聚氨酯弹性体,并进一步将消烟耐烧蚀反应型填料填充其中制得低烟耐烧蚀聚氨酯弹性材料。系统的研究了软段含量、交联度对产物力学性能的影响。结果表明:随软段长度的增加,HDI型聚醚弹性体的拉伸强度、邵氏硬度和回弹率降低,扯断伸长率增加;随着交联度的增加其扯断伸长率、邵氏硬度降低,拉伸强度则先降低后增加,回弹率却大幅增加。同时研究结果表明填充消烟耐烧蚀反应型填料的HDI型聚醚弹性体不仅具有优异的力学性能,还具有优异的低烟耐烧蚀性能。     

Night-time total electron content enhancements at equatorial anomaly region in China

This paper presents small scale (duration ?1 h, ΔTEC ? 1TECU) night-time total electron content (TEC) enhancements observed at the equatorial anomaly region in China, for the first time. The data is from a GPS receiver chain established in 2005 by Institute of Center for Space Science and Applied Research, Chinese Academy of Sciences and a GPS receiver of International GPS Service (IGS), located between Fuzhou (26.1°N, 119.3°E) and Nanning (22.8°N, 108.3°E). Two other GPS observations of IGS taken at higher latitude were also used to investigate the localization of such phenomenon. The characteristics of the night-time TEC enhancement are examined with two case studies. The TEC increases about 1–3TECU, intermittently. While the night-time TEC enhancement mainly occurs at the equatorial anomaly region, it can be observed at middle latitude as well. The spatial size of the enhancement region is less than 5° in longitude. The primary statistical study shows that the TEC enhancement is more often observed in spring and autumn, but rarely in summer. It has no dependence on geomagnetic activity. The enhancement can occur both before and after midnight.     

The effect of total solar eclipse of October 3, 2005, on the total electron content over Europe

GPS observations from EUREF permanent GPS network were used to observe the response of TEC (Total Electron Content) to the total solar eclipse on October 3, 2005, under quiet geomagnetic conditions of the daytime ionosphere. The effect of the eclipse was detected in diurnal variations and more distinctly in the variations of TEC along individual satellite passes. The trough-like variations with a gradual decrease and followed by an increase of TEC at the time of the eclipse were observed over a large region. The depression of TEC amounted to 3–4 TECU. The maximum depression was observed over all stations located at the maximum path of the solar eclipse. The delay of a minimum level of TEC with respect to the maximum phase of the eclipse was about 20–30 min.     

论电子商务的特征及其发展趋势

从电子商务的内涵出发 ,指出了电子商务具有主动性、风险性等特征 ;在分析影响电子商务的有利因素和不利因素的基础上 ,阐明了电子商务的发展趋势。     

Temporal evolution analysis of storm-enhanced density during an intense magnetic storm on March 2015

An intense Storm Enhancement Density (SED) event with the magnetic storm occurred on 17–24 March 2015 has been investigated. The morphological character of the SED during different phase of the magnetic storm is examined and compared with the non-storm time. Three intensity indexes, i.e., “general” SED index, “heavy” SED index and “severe” SED index, are defined to represent the intensity of SED respectively represented by the numbers of the ionospheric total electron content (TEC) grids with TEC > 60 TECu, TEC > 80 TECu and TEC > 100 TECu. The temporal evolution of the SED intensity indexes during a time span covering the non-storm time and the magnetic storm time have also been investigated. The SED exhibits a shape with two parallel slender troughs in the middle and low latitudes during the non-storm time and then gradually develops into an ellipse structure as the development of magnetic storm. The intensity of SED and the fluctuation of the TEC evolution are generally corresponding to the fluctuation of Dst index. The analyzing results enrich our understanding of the temporal and spatial evolution of the ionospheric SED.     

On the detection of anomalous seismo-ionospheric behavior in the presence of space weather stimuli for large earthquakes

Anomalous behavior of ionospheric total electron content (TEC) prior to earthquake has been observed in many studies. Evidence of such seismo-ionospheric coupling effects suggests that it is plausible to rely on TEC signatures for early earthquake warning. However, the detection of pre-earthquake TEC anomalies (PETA) has not been adopted in practice due to two pertinent issues. Firstly, the effects of space weather activity can affect TEC levels and cause anomalous behavior in the TEC. Usually arbitrary thresholds are set for space weather indices to eliminate TEC anomaly due to space weather effects. Secondly, the choice regarding moving time-window length used to characterise background variation of TEC within the statistical envelope approach has an effect on detection of PETA. While the rule-of-thumb in selecting the moving window length is to have a time window capable of capturing background variability and short-term fluctuations, the length of the time window used in the literature varies with little justification. In this study, a critical examination is conducted on the statistical envelope approach and in particular, to eliminate the effect of space weather activity without the use of arbitrary space indices to detect PETA. A two-part PETA identification procedure is proposed, consisting of wavelet analyses isolating non-earthquake TEC contributions, followed by the statistical envelope method using a moving window length standardized based on observed periodicities and statistical implications is suggested. The approach is tested on a database of 30 large earthquakes (M?≥?7.0). The proposed procedure shows that PETA can be detected prior to earthquakes at higher confidence levels without the need to separately check for space weather activity. More importantly, the procedure was able to detect PETA for studies where it was previously reported that PETA could not be detected or detected convincingly.     

Near real-time PPP-based monitoring of the ionosphere using dual-frequency GPS/BDS/Galileo data

Ionosphere delay is very important to GNSS observations, since it is one of the main error sources which have to be mitigated even eliminated in order to determine reliable and precise positions. The ionosphere is a dispersive medium to radio signal, so the value of the group delay or phase advance of GNSS radio signal depends on the signal frequency. Ground-based GNSS stations have been used for ionosphere monitoring and modeling for a long time. In this paper we will introduce a novel approach suitable for single-receiver operation based on the precise point positioning (PPP) technique. One of the main characteristic is that only carrier-phase observations are used to avoid particular effects of pseudorange observations. The technique consists of introducing ionosphere ambiguity parameters obtained from PPP filter into the geometry-free combination of observations to estimate ionospheric delays. Observational data from stations that are capable of tracking the GPS/BDS/GALILEO from the International GNSS Service (IGS) Multi-GNSS Experiments (MGEX) network are processed. For the purpose of performance validation, ionospheric delays series derived from the novel approach are compared with the global ionospheric map (GIM) from Ionospheric Associate Analysis Centers (IAACs). The results are encouraging and offer potential solutions to the near real-time ionosphere monitoring.     

残余V元素对1Crl8Ni9Ti钢板组织与性能的影响

通过试验详细论述了1Crl8Ni9Ti钢中不同残余V含量对材料固溶状态的组织及400℃、500℃长期时效后对组织、晶间腐蚀和室温、高温性能的影响。从而得出结论适量V的存在对1Crl8Ni9Ti钢板组织影响不大,对抗晶间腐蚀性能稍有提高,对室温、高温抗拉强度、屈服强度稍有提高,塑性稍有降低。