陆态网络VLBI和SLR站的空间归心测量

为了实现多种地壳运动测量技术的综合应用,研究了对全球卫星导航定位系统（GNSS）、甚长基线干涉测量（VLBI）和卫星激光测距（SLR）基准站观测数据进行联合解算的关键技术——高精度的空间归心测量。首次全面地进行了对实时监测地球岩石圈、水圈和大气圈变化的中国大陆构造环境监测网络（CMONOC）中VLBI站和SLR站的归心测量,并给出了观测结果,这对于CMONOC的运行与维护具有非常重要的意义。     

HY-2卫星激光观测精密定轨技术

2011年8月16日发射的海洋二号(HY-2)卫星是中国第一颗海洋动力环境卫星,配备的卫星激光测距跟踪系统即作为HY-2卫星定轨基准系统,同时又是HY-2卫星定轨系统之一。本文较为详细地介绍了HY-2卫星激光观测、轨道预报和激光跟踪系统(SLR)定轨技术,并对SLR定轨结果进行了初步检验。     

PNT体系视角下卫星导航与不依赖卫星导航技术融合发展研究

卫星导航自问世以来以其全天候、全天时、低成本的优势，成为广泛使用的导航定位授时（PNT）方式；但在应用层面，为了规避对卫星导航单一手段的过度依赖，“不依赖卫星导航技术”概念被提出并受到重视，如何准确把握两者之间的关系成为现实而迫切的问题。本文概述了卫星导航技术特征与体系定位，进而基于PNT体系视角，对比分析了惯性导航、匹配导航、无线电导航（除卫星导航外）等典型不依赖卫星导航技术的性能、成本、应用场景；辨析了卫星导航与不依赖卫星导航的关系，明晰了卫星导航作为最大共性需求满足者、体系核心与基石的总体定位，量化分析了卫星导航与不依赖卫星导航技术融合的效能。我国PNT体系的科学发展，需要创新突破不依赖卫星导航技术，促进卫星导航和不依赖卫星导航技术深度融合，同时加快低轨导航系统建设，提升卫星导航性能并最大化体系贡献率。     

DDS在卫星定时基准源中的应用

本文介绍了直接数字频率合成器（DDS）的原理及其特性,以及在卫星定时基准源中的应用。实例表明利用DDS技术使卫星定时基准源满足通讯基准站时钟频率精确要求。DDS技术在时钟频率供给和卫星定位方面取得了高效和不错的成果。     

面向PHM技术验证的陀螺故障模拟软件设计

陀螺是卫星的典型部件,可以作为卫星故障预测与健康管理技术（PHM）研究的典型对象。重点研究了基于模型分析的单自由度液浮陀螺的故障模拟技术。工作内容如下：1）分析卫星故障模拟系统的结构,确定陀螺故障模拟器与外部的通信接口;2）分析陀螺的原理模型,研究陀螺的典型故障并提炼出故障模式,归纳可以用于故障模拟与分析的特征参数;3）开发具备硬件通信接口的陀螺故障模拟软件,可与嵌入式硬件设备进行联合仿真。开发的软件依照真实部件输出各类故障数据,为卫星PHM技术研究提供数据支持。     

全国北斗卫星导航标准化委员会成立

2014年4月28日,全国北斗卫星导航标准化技术委员会（以下简称“北斗标技委”）成立大会暨第一次全体工作会议在京召开。会上宣读了《国家标准委总装备部关于成立全国北斗卫星导航标准化技术委员会的通知》,听取了《北斗卫星导航标准化工作汇报》,并讨论了《全国北斗卫星导航标准化技术委员会章程》（草案）,     

美国陆军开发纳米成像卫星提供实时战术情报

美国陆军太空与导弹防御指挥部（USASMDC）/美国陆军战略司令部（ARSTRAT）向安德鲁斯航天公司授出了一个开发纳米卫星的合同,以求该卫星能够为美国作战人员提供实时的战术图像。     

中国的极轨气象卫星

气象卫星是具有巨大经济和社会效益的应用卫星，中国的极轨气象卫星经历了从试验阶段到业务应用阶段的发展历程。文章简要介绍了“风云一号”（FY-1）极轨气象卫星的发展概况和技术性能，星载十通道扫描辐射计和长寿命、高可靠极轨卫星平台取得的成功；重点介绍了中国新一代的极轨气象卫星“风云三号”（FY-3）的总体概况，归纳了卫星的技术特点。     

意法半导体芯片跟踪伽利略系统测试成功

近日,横跨多重电子应用领域、全球领先的半导体供应商意法半导体宣布,TeseoⅡ单片卫星跟踪IC使用欧洲自主卫星导航系统伽利略（Galileo）卫星进行首次地面定位测试取得成功。此次测试是意法半导体与欧洲航天局（ESA）联合进行的测试。     

基于双频组合观测值的GNSS全球电离层建模比较

为了比较当前不同斜路径电子含量（STEC）提取方法对全球电离层图（GIM）精度的影响,本文利用多个系统,包括全球定位系统（GPS）、格洛纳斯卫星导航系统（GLONASS）、伽利略卫星导航系统（Galileo）、北斗卫星导航系统（BDS）这4个系统的全球导航卫星系统（GNSS）的观测值,基于相位平滑伪距（CCL）和非差非组合精密单点定位（PPP）技术提取STEC建立相应GIM并对其精度进行评估。试验结果表明,与CCL相比,采用非差非组合PPP建立的全球电离层模型精度提升0.11 TECu。在南半球和北半球低纬度地区,非差非组合PPP解算的电离层模型精度提升率为6.3%～45.7%,而在45°N以上的北半球中高纬度地区,两者精度相当。     

Rasch measurement in developing faculty ratings of students applying to graduate school

The Standardized Letter of Recommendation (SLR), a 28-item form, was created by ETS to supplement the qualitative rating of graduate school applicants' nonacademic qualities with a quantitative approach. The purpose of this study was to evaluate the following psychometric properties of the SLR using the Rasch rating scale model: dimensionality, reliability, item quality, and rating category effectiveness. Principal component and factor analyses were also conducted to examine the dimensionality of the SLR. Results revealed (a) two secondary factors underlay the data, along with a strong higher order factor, (b) item and person separation reliabilities were high, (c) noncognitive items tended to elicit higher endorsements than did cognitive items, and (d) a 5-point Likert scale functioned effectively. The psychometric properties of the SLR support the use of a composite score when reporting SLR scores and the utility of the SLR in higher education and in admissions.     

Mapping Sea Level Rise Behavior in an Estuarine Delta System: A Case Study along the Shanghai Coast

Sea level rise (SLR) is a major projected threat of climate change that is expected to affect developing coastal cities located in estuarine delta regions. Shanghai is one such city, being located in the Yangtze River Delta (YRD). It is difficult, however, for decision-makers to implement adaptation due to the uncertain causes, magnitudes, and timings of SLR behaviors. This paper attempts to map the causes and magnitudes of SLR behaviors on a decadal scale. We analyze the tidal level records from 11 tidal gauge stations and the corresponding bathymetry measurements around these stations since 1921. We identify three new SLR behaviors along the Shanghai coast due to anthropogenic geomorphologic changes (AGCs), besides the well-known eustatic sea level rise (ESLR), tectonic subsidence (TS), and urban land subsidence (ULS). The first new behavior is regional sea level rise (RSLR), which occurs as a result of land reclamation and deep waterway regulation. The second is regional sea level fall (RSLF), which occurs because the channel bed is eroded due to sediment supply decline in the river catchment. The last SLR behavior is local tidal datum rise (LTDR). Thus, we project that the magnitude of SLR for the Shanghai coast ranges from 10 cm to 16 cm from 2011 to 2030. Clarifying SLR behaviors is important to aid local decision-makers in planning structural and non-structural measures to combat escalating flood damage costs in an estuarine delta system; this field is full of future challenges.     

Investigation of Spin-Lattice Relaxation in the Photoexcited Triplet States of Fullerene Crystal C60

The spin-lattice relaxation (SLR) of photoexcited triplet states in fullerene C₆₀ crystal is investigated at low temperatures and high magnetic fields. The mixing of translatjional motions of the molecule and vibrational motions of the nuclei (TVM Relaxation mechanism) is chosen as the majo phenomenon, leading to the coupling of spin system with acoustic vibrations. The general expressions of SLR rates for the direct one-phonon processes are obtained using the atom-atom potentials and ab initio molecular orbitals (MO) methods. The influence of dynaijnic Jahn-Teller (JT) effect in a molecule C₆₀ on the SLR rates is analyzed. A comparison of calculated values for SLR time with available experimental data is carried out.     

Spin–Lattice Relaxation of Mn Ions in Nanostructures with Semiconductor Quantum Dots

We use the combination of nonequilibrium phonon and exciton luminescence techniques to study the spin dynamics in diluted magnetic semiconductor structures with (Cd,Mn)Te and (Cd,Mn)Se quantum dots (QDs). We show that the spin–lattice relaxation (SLR) of Mn ions in these structures differs strongly from the SLR in quantum wells. We explain the results by a model where SLR process in structures with QDs is modified by the spin diffusion on Mn ions from the QD to a wetting layer.     

HY-2卫星双频GPS精密定轨技术

海洋二号(HY-2)卫星双频全球定位跟踪系统(GPS)接收机获取的GPS数据是基于非差简化动力学方法应用于HY-2卫星精密轨道确定。差分GPS载波相位数据可以消除钟差,同时利用GPS数据获得HY-2卫星轨道和GPS卫星轨道。GPS数据确定的轨道利用激光测距进行了检核,并与法国太空总署确定的轨道以及综合定轨策略确定的轨道进行了比较,HY-2卫星基于GPS数据精密轨道径向成分优于3cm。     

Quantitative approaches for the integration of production and distribution planning in the supply chain: a systematic literature review

Production and distribution are the two primary internal elements of the supply chain. This paper presents a systematic literature review (SLR) of quantitative approaches for the integration of production and distribution planning (IPDP) in the supply chain. We provide a classification framework with eight dimensions and give a brief overview of the quantitative approaches such as modelling approaches and solution approaches for the IPDP problem in the supply chain. The SLR has been carried out using two basic search databases Scopus and Web of Science. In all, we identify relevant articles in the period from 2000 to 2019. We also highlight certain research opportunities, suggestions, and research gaps for possible future research by assessing the current knowledge on the quantitative approaches for IPDP problems in the supply chain.     

Effect of Close-Coupled Bends in Pneumatic Conveying

Pressure drop in a close-coupled double bend in pneumatic conveying of fly ash is studied. Tests are carried out with a 6.35 cm (2.5 in) diameter 169.8 m (557 ft) long pipeline with various combinations of airflow, ash flow, phase density, and conveying velocity. The pressure drop across two close-coupled 90-degree bends is compared to the pressure drop in an isolated single 90-degree bend. Six ash samples of different physical and chemical compositions are used in the tests. Resulting bend pressure drops are correlated to the corresponding phase density and superficial air velocity at the bend inlet. The correlation pattern represented by the relationship {\Delta P_{solids} \over {SLR}} = Y1 \cdot V^{Y2} is established and found to vary with ash properties. For both single and close-coupled double bends and operating test conditions with \Delta {\rm P}_{\rm solids} / {\rm SLR} 0.15 at the bend entry, 86% of the measured test points fall within the range of - 20% of the \Delta {\rm P}_{\rm solids} / SLR calculated point. Below this threshold, the test results show that the pressure drops due to solids flow through a close-coupled double bend and single bends are often indistinguishable. Consequently, the loss through a close-coupled double bend cannot be considered as the cumulative effect of two isolated single bends.     

Deformation behavior of a TiZr-based metallic glass composite containing dendrites in the supercooled liquid region

The deformation behavior of a TiZr-based bulk metallic glass composite(BMGC) was characterized in the supercooled liquid region(SLR) from 623 K to 693 K. It was observed that the alloy exhibits the deformation behavior from work softening at low temperatures to work hardening at high temperatures.The yield stress and overshoot stress decrease remarkably with the increase of temperature, accompanied by superplasticity. The results showed that the crystallization occurred in the amorphous matrix for the post-deformation samples and the volume fraction of the corresponding crystallization products increased with increasing testing temperature. It is implied that the work hardening behavior was closely associated with the crystallization of the amorphous matrix. The tensile stress can accelerate the crystallization of amorphous matrix and the martensitic transformation of dendrite phases, which implies that the thermal stability of the alloy decreases under tension. These findings shed light on designing new BMGCs with high mechanical performance as well as the good SLR formability.     

大起大落重又崛起的APS

ＡＰＳ单反相机在１９９７年问世，ＡＰＳ表现出优良的画面质量，使得消费者在对它冷落一段时间之后不得不进行重新评价。另外，提出了ＡＰＳ在中国所遇到问题，如缺少冲扩店，胶卷价格贵等。