Bayesian structure selection for vector autoregression model

A vector autoregression (VAR) model is powerful for analyzing economic data as it can be used to simultaneously handle multiple time series from different sources. However, in the VAR model, we need to address the problem of substantial coefficient dimensionality, which would cause some computational problems for coefficient inference. To reduce the dimensionality, one could take model structures into account based on prior knowledge. In this paper, group structures of the coefficient matrices are considered. Because of the different types of VAR structures, corresponding Markov chain Monte Carlo algorithms are proposed to generate posterior samples for performing inference of the structure selection. Simulation studies and a real example are used to demonstrate the performances of the proposed Bayesian approaches.     

Effect of hydrogen on the friction and wear of Ni-P coatings

The effects of charging and outgassing on the friction and wear of Ni-P amorphous and nanocrystalline coatings were studied under ambient humidity and temperature. The results indicate that hydrogen charging can greatly decrease the volume loss during friction and increase the wear durability. However, the wear durability can be restored after outgassing. There are many cracks on the brittle nanocrystalline before charging, and no crack appears after charging, but there are only a few cracks on the outgassed sample. This indicates that hydrogen charging can inhibit the crack formation during friction for the brittle Ni-P nanocrystalline. For the charged sample, after the surface layer was removed by polishing, the wear track and the friction coefficient are consistent with those of an uncharged sample. The friction coefficient of the charged amorphous coating is very small within the first 140 s and then increases suddenly to the value corresponding to the uncharged sample. The absorbed surface layer lubricates the surface, reduces the friction coefficient, and improves the wear durability.     

Effect of sintering temperature on the microstructure and thermal conductivity of Al/diamond composites prepared by spark plasma sintering

Spark plasma sintering was used to fabricate Al/diamond composites. The effect of sintering temperature on the microstructure and thermal conductivity (TC) of the composites was investigated with the combination of experimental results and theoretical analysis. The composite sintered at 550℃ shows high relative density and strong interfacial bonding, whereas the composites sintered at lower (520℃) and higher (580–600℃) temperatures indicate no interfacial bonding and poor interfacial bonding, respectively. High relative density and strong interfacial bonding can maximize the thermal conductivity of Al/diamond composites, and taking both effects of particle shape and inhomogeneous interfacial thermal conductance into consideration can give a fairly good prediction of composites’ thermal conduction properties.     

星敏感器图像显示验证VGA接口设计

设计了星敏感器图像验证VGA显示接口,采用单片FPGA实现了输入图像数据处理、VGA时序产生等功能.实验仿真表明,该系统逻辑时序设计正确,能很好地完成对星敏感器星点定位、星图识别等功能测试的监视工作.     

Iron speciation in cherts from the Laobao Formation, South China: Implications for anoxic and ferruginous deep-water conditions

Cherts in the Laobao Formation in the Silikou section, South China were deposited in terminal Ediacaran deep-water. The speciations of iron in cherts, such as pyrite Fe (Fe_P), HCl-extractable Fe (Fe_H), and total Fe (Fe_T), and their interrelationships, are proxies for distinguishing oxic, anoxic but ferruginous, and sulfidic conditions, which is an effective method for studying the terminal Ediacaran ocean environment. For chert samples from the Laobao Formation, pyrite concentrations are generally low (<0.56%), degree of pyritization (DOP) ranges from <0.01 to 0.78 and most are <0.45; (Fe_P+Fe_H)/Fe_T ratios are between 0.27 and 0.84 and most exceed 0.38, and most of FeT/Al ratios range from 0.55 to 5.87 (averaging 1.1). Relatively high content of highly reactive Fe and low content of pyrite indicate a scarcity of H₂S and Fe-enriched deep-water. These features suggested that the deposition setting of Laobao cherts was anoxic and ferruginous. Terminal Ediacaran deep-water in the South China Basin was most likely anoxic and ferruginous, which played a key role in the emergence and evolution of early multicellular life.     

Re-Os isotopic constraint to the age of in komatiites in the Neoarchean Guyang greenstone belt, North China Craton

The 2.5 Ga Guyang greenstone belt is a major lithological unit in the northwestern part of the North China Craton. Komatiites have recently been identified to occur within the lower part of the meta-volcanic sedimentary sequence of the greenstone belt. The biggest komatiite near Guyang has been mapped out, which is 500 m long and 50 m wide lenticular block. Re-Os isotopic compositions of 9 samples were analyzed to date the komatiites. The Os contents are from 0.88 to 2.63 ppb, identical with typical komatiites, and slightly lower than the normal mantle. The ¹⁸⁷Os/¹⁸⁸Os ratios are from 0.1115 to 0.1197, which are lower enough to exclude the origin of Phanerozoic magma as widely developed in adjacent areas. The calculated Re depletion model ages (T _RD) are from 1346 to 2454 Ma, among them the oldest age of 2454 Ma gives the minimum evaluation for the formation age of the Guyang komatiite. Therefore, the komatiites are a part of the Guyang greenstone belt, indicating high degree melting of mantle during ～2.5 Ga crustal growth event.     

从银行业自助服务发展看创新服务模式

对银行业自助服务模式的发展状况进行了分析,阐述了银行业自助服务的优点,同时对银行营业网点能更好地为客户服务提出合理化建议.     

基于损伤累积的大跨度隧道（硐库）爆破振动传播规律

为研究损伤累积效应对隧道内爆破振动波传播与衰减规律的影响,利用萨道夫斯基公式对某大跨硐库施工过程中测得的爆破振动波结果进行拟合分析.结果表明:在单次爆破作用下,爆破振速与主频均随测点与爆破中心距离的增大而减小;在多次爆破作用影响下,测点爆破振速与主频均随爆破次数增加不断衰减;随着爆破次数的增加,衰减系数(α)缓慢增长,场地系数(K)逐渐衰减.现场爆破振动波的变化规律与室内试验结果相一致,且质点振动主频与峰值振速在变化规律方面存在较高对应关系.在进行振动波传播与衰减规律研究、爆破振动安全标准制定和振动危害效应评价时,应考虑损伤累积效应的影响.     

Sperm chromatin proteomics identifies evolutionarily conserved fertility factors

Male infertility is a long-standing enigma of significant medical concern. The integrity of sperm chromatin is a clinical indicator of male fertility and in vitro fertilization potential: chromosome aneuploidy and DNA decondensation or damage are correlated with reproductive failure. Identifying conserved proteins important for sperm chromatin structure and packaging can reveal universal causes of infertility. Here we combine proteomics, cytology and functional analysis in Caenorhabditis elegans to identify spermatogenic chromatin-associated proteins that are important for fertility. Our strategy employed multiple steps: purification of chromatin from comparable meiotic cell types, namely those undergoing spermatogenesis or oogenesis; proteomic analysis by multidimensional protein identification technology (MudPIT) of factors that co-purify with chromatin; prioritization of sperm proteins based on abundance; and subtraction of common proteins to eliminate general chromatin and meiotic factors. Our approach reduced 1,099 proteins co-purified with spermatogenic chromatin, currently the most extensive catalogue, to 132 proteins for functional analysis. Reduction of gene function through RNA interference coupled with protein localization studies revealed conserved spermatogenesis-specific proteins vital for DNA compaction, chromosome segregation, and fertility. Unexpected roles in spermatogenesis were also detected for factors involved in other processes. Our strategy to find fertility factors conserved from C. elegans to mammals achieved its goal: of mouse gene knockouts corresponding to nematode proteins, 37% (7/19) cause male sterility. Our list therefore provides significant opportunity to identify causes of male infertility and targets for male contraceptives.