发射装置电路盒散热技术及其应用

设计电路盒结构时应使其产生的热量尽可能少,并可将工作中所产生的热量尽快散发出去,使电路盒的温度控制在正常工作范围内。阐述了散热性对发射装置电路盒工作性能的影响,分析了电路盒中热量的产生过程。通过散热技术在发射装置电路盒设计装配过程中的应用,提高了电路盒的可靠性。     

Role of attachment to surfaces on the prevalence and survival of Campylobacter through food systems

Campylobacter continues to be one of the bacterial pathogens most frequently associated with human gastrointestinal illness worldwide. Because Campylobacter primarily colonizes the intestines of animals used for food production, food products of animal origin can become contaminated with this pathogen and thus represent a significant risk factor. Despite application of numerous physical and chemical interventions to control Campylobacter during food processing, the high isolation rate of this pathogen from some retail meat products indicates that Campylobacter is able to persist from animal slaughterhouses through food systems. Given the fastidious growth requirements and high susceptibility of this pathogen to environmental conditions, the ability of Campylobacter to attach to food and food-related surfaces is likely to play an important role in food contamination and movement through food systems. This review was compiled to (i) describe how the attachment of Campylobacter to surfaces influences the prevalence and survival of the organism through food systems, (ii) examine the potential factors affecting the ability of Campylobacter to attach to surfaces, and (iii) suggest strategies for controlling this attachment process.     

Enhanced hot-carrier cooling and ultrafast spectral diffusion in strongly coupled PbSe quantum-dot solids

PbSe quantum-dot solids are of great interest for low cost and efficient photodetectors and solar cells. We have prepared PbSe quantum-dot solids with high charge carrier mobilities using layer-by-layer dip-coating with 1,2-ethanediamine as substitute capping ligands. Here we present a time and energy resolved transient absorption spectroscopy study on the kinetics of photogenerated charge carriers, focusing on 0-5 ps after photoexcitation. We compare the observed carrier kinetics to those for quantum dots in dispersion and show that the intraband carrier cooling is significantly faster in quantum-dot solids. In addition we find that carriers diffuse from higher to lower energy sites in the quantum-dot solid within several picoseconds.     

Anomalous independence of multiple exciton generation on different group IV-VI quantum dot architectures

Multiple exciton generation (MEG) in PbSe quantum dots (QDs), PbSe(x)S(1-x) alloy QDs, PbSe/PbS core/shell QDs, and PbSe/PbSe(y)S(1-y) core/alloy-shell QDs was studied with time-resolved optical pump and probe spectroscopy. The optical absorption exhibits a red-shift upon the introduction of a shell around a PbSe core, which increases with the thickness of the shell. According to electronic structure calculations this can be attributed to charge delocalization into the shell. Remarkably, the measured quantum yield of MEG, the hot exciton cooling rate, and the Auger recombination rate of biexcitons are similar for pure PbSe QDs and core/shell QDs with the same core size and varying shell thickness. The higher density of states in the alloy and core/shell QDs provide a faster exciton cooling channel that likely competes with the fast MEG process due to a higher biexciton density of states. Calculations reveal only a minor asymmetric delocalization of holes and electrons over the entire core/shell volume, which may partially explain why the Auger recombination rate does not depend on the presence of a shell.     

Diffusion coefficient of carbon in Fe–Ni alloy during synthesis of diamond under high temperature and high pressure

Synthetic diamond particles were prepared under high temperature and high pressure using arrayed seeds. A dense Fe–Ni alloy shell covered each diamond seed during synthesis; the growth of diamond particles was controlled by the diffusion of carbon through the metallic shell. The diffusion coefficient of carbon through Fe–Ni melt at 1600 K and 5.5 GPa is about 5×10^?6 cm²/s, with an activation energy for diffusion of 336 kJ/mol.     

Dramatic Enhancement of Photoluminescence Quantum Yields for Surface‐Engineered Si Nanocrystals within the Solar Spectrum

Substantial improvements of the absolute photoluminescence quantum yield (QY) for surfactant‐free silicon nanocrystals (Si‐ncs) by atmospheric pressure microplasma 3‐dimensional surface engineering are reported. The effect of surface characteristics on carrier multiplication mechanisms is explored using transient induced absorption and photoluminescence QY. Surface engineering of Si‐ncs is demonstrated to lead to more than 120 times increase in the absolute QY (from 0.1% up to 12%) within an important spectral range of the solar emission (2.3–3 eV). The Si‐ncs QY is shown to be stable when Si‐ncs are stored in ethanol at ambient conditions for three months.     

一种改进型ip-iq坐标变换电流谐波检测方法

针对现有的一些检测方法在三相电压不对称或畸变时存在的一些缺陷,根据通用瞬时无功功率理论,对传统的ip-iq坐标变换的谐波电流检测方法做了简单的改进。该方法从矢量分析角度出发,利用带通滤波器,根据三相电网电压和电流综合信息,获取ip-iq坐标变换矩阵来实现对谐波电流的检测,省去了三角函数计算和锁相环的使用,简化了计算。该方法既可适用于三相对称正弦电源系统,也可适用于不对称非正弦电源系统和电压畸变系统。仿真结果验证了该方法的正确性。     

Stationary points of a kurtosis maximization algorithm for blindsignal separation and antenna beamforming

Blind source separation has been the subject of extensive research. In particular, blind antenna beamforming is an effective signal separation technique for communication systems to combat co-channel interference. Among many potential candidate approaches, the simple constant modulus algorithm (CMA) has been widely studied and used in practice. The CMA is designed to capture and separate signals with negative kurtosis. However, when some signals have positive kurtoses, the CMA is unable to capture and separate these sources. We show that the kurtosis maximum algorithm (KMA) can capture signals with both the positive and negative kurtoses. Its global convergence proof is presented for noiseless systems with multiple signals sources and for systems with a single source and zero-kurtosis (such as Gaussian) additive noise     

辽河盆地红星地区浅层气藏成因及其勘探意义

通过分析辽河盆地红星地区浅层气的分布、控制因素与成藏特征,搞清了该区浅层气的成因,指出红星地区与驾掌寺生油洼陷紧邻,驾掌寺大断裂的晚期活动为深层油气在纵向上的调整提供了通道条件和圈闭条件,进而为浅层气藏的形成奠定了物质基础,同位素资料显示东营组浅层气为高成熟热解气,与深层油气藏具有亲缘关系,深部（沙一段）的原生油气藏被改造,导致部分油气沿断裂发生垂向运移至浅层,并沿断裂两侧聚集而形成浅层气藏。认为该区的浅层气已形成了一定规模的产能,在目前天然气勘探开发形势严峻的情况下,可为辽河油田天然气的勘探开发提供一个具体目标。