Synthesis of CdSe quantum dots via paraffin liquid and oleic acid

This paper reported an efficient and rapid method to produce highly monodispersed CdSe quantum dots (QDs), in which the traditional trioctylphosphine oxide (TOPO) was replaced by paraffin liquid as solvent and oleic acid as the reacting media. The experimental conditions and the properties of QDs had been studied in detail. The resulting samples were confirmed of uniform size distribution with transmission electronic microscopy (TEM), while UV-vis absorption and photoluminescence (PL) spectra clearly indicated that such synthesized QDs had good fluorescence properties.

Influence of stress path change on the resistance to plastic deformation of cold rolled sheets

Flat workpieces have been tested in order to investigate the influence of stress path change （loading mode） while keeping strain path unchanged. These investigations are pertinent to the testing of cold rolled strips and to subsequent forming. The workpieces which first compressed by plane strain compression in thickness direction were then tested in perpendicular direction in order to measure the influence of strain and stress path. The tension workpieces came from flat die compression test at different deformation histories. Two different materials were investigated： 18/8 Ti stainless steel and AW-1050 aluminium. The results show that the plastic flow by tension in lengthwise direction after pre-strain by compression in thickness direction will begin at an appreciably lower stress than that of the workpieces unloaded after pre-compression. Comparing with two materials, it can be seen that both 18/8 Ti stainless steel and AW-1050 aluminium behave similarly. The drop in yield stress is lower for AW-1050 aluminium than that for 18/8 Ti stainless steel. However, reloading in different directions than in the precious step results in significantly higher strain hardening.

Science Letters:The Moore’s Law for photonic integrated circuits

We formulate a “Moore’s law” for photonic integrated circuits (PICs) and their spatial integration density using two methods. One is decomposing the integrated photonics devices of diverse types into equivalent basic elements, which makes a comparison with the generic elements of electronic integrated circuits more meaningful. The other is making a complex compo- nent equivalent to a series of basic elements of the same functionality, which is used to calculate the integration density for func- tional components realized with different structures. The results serve as a benchmark of the evolution of PICs and we can con- clude that the density of integration measured in this way roughly increases by a factor of 2 per year. The prospects for a continued increase of spatial integration density are discussed.

Near-field characteristics of highly non-paraxial subwavelength optical fields with hybrid states of polarization

The vectorial structure of an optical field with hybrid states of polarization （SOP） in the near-field is studied by using the angular spectrum method of an electromagnetic beam. Physical images of the longitudinal components of evanescent waves are illustrated and compared with those of the transverse components from the vectorial structure. Our results indicate that the relative weight integrated over the transverse plane of the evanescent wave depends strongly on the number of the polarization topological charges. The shapes of the intensity profiles of the longitudinal components are different from those of the transverse components, and it can be manipulated by changing the initial SoP of the field cross-section. The longitudinal component of evanescent wave dominates the near-field region. In addition, it also leads to three-dimensional shape variations of the optical field and the optical spin angular momentum flux density distributions.

Design and fabrication of ultrasmall arrayed waveguide grating multiplexers based on Si nanowire waveguides

The large refractive index difference between Si and SiO2 makes it possible to realize ultrasmall photonic integrated circuits. A 5×5 ultracompact arrayed waveguide grating multiplexer based on 500×250 nm Si nanowire waveguides is designed and fabricated by using the technologies of E-beam writing and amorphous-Si deposition. The mea- sured channel spacing is about 1.5 nm (close to the design value) and the channel crosstalk is about –8 dB.

Copper Release Kinetics and Ageing of Insulation Paper in Oil-Immersed Transformers

The paper provides a general overview of chemical processes leading to the degradation of oil-paper insulation in oil-immersed electrical current transformers. Previous knowledge available in literature is complemented by new results placing a specific emphasis on the physicochemical factors which affect the copper release in the insulation oil and the oil oxidation kinetics. It is demonstrated that various ageing processes interact with each other, with one or another process dominating under specific conditions. Comprehensive but disjoint studies focusing on separate sub-processes may produce rather misleading results, and occasionally, lie behind rather irrelevant quality demands imposed on the insulating liquids.

MAGNETIC FIELD EFFECT ON PHOTOPOLYMERIZATION OF STYRENE MICROEMULSION

External magnetic field increases the photo-induced polymerization rate of styrene microemulsion.The type of photoinitiator plays an important role. The photoinitiators, used are dimethoxyphenyl acetophenone(DMPA), 1-hydroxycyclohexyl phenylketone (Irgacure 184) and dimethylhydroxyacetophenone (Darocur 1173). No magnetic effect was observed by using dibenzylketone (DBK) as photoinitiator. The molecular weight of the polymer is slightly affected by magnetic field. The influence of temperature has also been investigated.

光交联低密度聚乙烯绝缘材料研究Ⅰ——光交联特征、反应条件和某些性能

本文对光交联法研制LDPE绝缘材料作了初步探索:研究了LDPE熔融态光交联动力学特征,光引发体系强化交联的效率和机理;考察了温度、光强等反应条件对交联的影响;测定了光交联材料的交联密度、交联均匀性和某些物理性能。

冷轧材料的各向异性对断裂性能的影响

为研究材料在冷轧过程中产生各向异性现象对断裂性能的影响,本文通过Ⅰ,Ⅱ型复合到纯Ⅱ型加载及有限元计算,研究了冷轧材料的各向异性对裂纹初始扩展规律和断裂性能的影响。结果表明,这种弱各向异性确实会影响材料的断裂形态。在垂直和平行于轧制的方向上,材料具有不同的断裂力学性状,且当K_I/K_I>1时,2种不同取向的试样大致沿τ_(max)方向开裂;当K_I/K_I<1时,裂纹会发生尖锐转折并呈Ⅰ型方式断裂。文中也给出了利用复合加载下的P-CMOD曲线确定裂纹临界开裂点的一种简单实验方法。

Recent Progress,Challenges,and Prospects in Two‑Dimensional Photo‑Catalyst Materials and Environmental Remediation

The successful photo-catalyst library gives significant information on feature that affects photo-catalytic performance and proposes new materials.Competency is considerably significant to form multi-functional photo-catalysts with flexible characteristics.Since recently,two-dimensional materials(2DMs)gained much attention from researchers,due to their unique thickness-dependent uses,mainly for photo-catalytic,outstanding chemical and physical properties.Photo-catalytic water splitting and hydrogen(H2)evolution by plentiful compounds as electron(e−)donors is estimated to participate in constructing clean method for solar H2-formation.Heterogeneous photocatalysis received much research attention caused by their applications to tackle numerous energy and environmental issues.This broad review explains progress regarding 2DMs,significance in structure,and catalytic results.We will discuss in detail current progresses of approaches for adjusting 2DMs-based photo-catalysts to assess their photo-activity including doping,hetero-structure scheme,and functional formation assembly.Suggested plans,e.g.,doping and sensitization of semiconducting 2DMs,increasing electrical conductance,improving catalytic active sites,strengthening interface coupling in semiconductors(SCs)2DMs,forming nano-structures,building multi-junction nano-composites,increasing photo-stability of SCs,and using combined results of adapted approaches,are summed up.Hence,to further improve 2DMs photo-catalyst properties,hetero-structure design-based 2DMs’photo-catalyst basic mechanism is also reviewed.

在超常温度和压力下交联的橡胶圆柱形试样的压缩应力松弛性能

Frenkin早已在论文中提到在超常压力及温度下,对不饱和橡胶进行处理,而且不加任何交联剂而导致橡胶的硫化即“热硫化”。文献[1]认为乙烯基有助于产生这种热硫化。 本文将提出和讨论带有不同乙烯基含量的双烯烃橡胶热硫化后的测量结果。例如 ○ 100℃下的静态压缩应力松弛。 ○ 用扫描微分热测量仪测定T_g转变。 ○ 100℃下的压缩永久变形。 ○ 用溶胀试验法测量交联密度。

A tunable dual-broad-band branch-line coupler utilizing composite right/left-handed transmission lines

A tunable dual-broad-band branch-line coupler (BLC) utilizing composite right/left-handed (CRLH) transmission lines is presented. Two λ/4 segments consisting of CRLH transmission lines are added to each port to broaden the dual bands of the branch-line coupler. Numerical simulation and optimal design of the novel coupler are presented. The dual bands of the novel coupler are tunable and broad. The 1-dB bandwidth of each pass band is more than 16% of the central frequency.

A completely open cavity realized with photonic crystal wedges

A completely open cavity, which is formed by three 60-degree wedges of a photonic crystal with negative effective index, is introduced. Such a realizable design for a completely open cavity (i.e., without any reflective wall in the radial direction) is the first of its kind ever been reported. Due to the negative effective refraction index of the photonic crystal and the high transmission at the photonic crystal/air interfaces, a closed path with zero optical path is formed for the resonance. The present open cavity is very suitable for use as a biosensor as it has large air wedges into which a liquid measurand can flow easily.

Simultaneous negative permittivity and permeability in a coherent atomic vapour

A new quantum optical mechanism to realize simultaneously negative electric permittivity and magnetic permeability is suggested. In order to obtain a negative permeability, we choose a proper atomic configuration that can dramatically enhance the contribution of the magnetic-dipole allowed transition via the atomic phase coherence. It is shown that the atomic system chosen with proper optical parameters can give rise to striking electromagnetic responses （leading to a negative refractive index） and that the atomic vapour becomes a left-handed medium in an optical frequency band. Differing from the previous schemes of artificial composite metamaterials （based on classical electromagnetic theory） to achieve the left-handed materials, which consist of anisotropic millimetre-scale composite structure units, the left-handed atomic vapour presented here is isotropic and homogeneous at the atomic-scale level. Such an advantage may be valuable in realizing the superlens （and hence perfect image） with left-handed atomic vapour.

Nanophotonics and negative ε materials

The feasibility of using metal optics or negative ε materials, with the aim of reducing the transversal extent of waveguided photonic fields to values much less than the vacuum wavelength, in order to achieve significantly higher densities of integration in integrated photonics circuits that is possible today is discussed. Relevant figures of merit are formulated to this end and used to achieve good performance of devices with today＇s materials and to define required improvements in materials characteristics in terms of decreased scattering rates in the Drude model. The general conclusion is that some metal based circuits are feasible with today＇s matals. Frequency selective metal devices will have Q values on the order of only 10-100, and significant improvements of scattering rates or lowering of the imaginary part of e have to be achieved to implement narrowband devices. A photonic ＂Moore＇s law＂ of integration densities is proposed and exemplified.

利用遥感与地理信息系统（GIS）研究厄立特里亚中部高地的地下水

通过遥感、数字高程模型评估（DEM）、地理信息系统（GIS）和实地测量技术的综合应用研究厄立特里亚地下水条件。对遥感数据进行解译以绘制岩性图和线性构造图。利用数字高程模型（DEM）绘制线性构造图和地貌图。通过实地研究开展构造研究，并把这些构造与线性构造解译相关联。在现场根据钻井记录和抽水试验数据，对泉和水井的水文地质背景开展调查。在地理信息系统中集成和分析了所有专题图层。研究结果表明，地下水的存在受到岩性、构造和地形的控制。由于原生孔隙度和次生孔隙度致使玄武岩的出水量最高。高出水量的水井和泉一般与大规模线性构造、交叉线性构造以及相应的构造特征有关。在崎岖地形的变质岩和火成侵入岩中，地下水主要存在于拥有河谷堆积物的排泄通道内。地下水潜力巨大区域一般为上覆于红土化结晶岩的玄武岩层、拥有密集线性构造的平坦地形以及在结构上受限并含有河谷堆积物的排泄通道。所有研究结果证实，遥感和地理信息系统是研究地下水资源和开发相应的勘探计划的有效手段。

Integrated photonics in the 21st century

We review the emergence and development of integrated photonics and its status today.The treatise is focused on information and communications technology(ICT)applications,but the technology is generically employable for a wealth of other applications,such as sensors.General properties of the waveguides that form the basis of integrated photonics are reviewed,and several examples of integrated photonics based on silicon and plasmonics are presented.The all-important development of integrated low-power nanophotonics is discussed and current challenges and prospects of the field are elucidated.The treatment is focused on the photonic fabric between source and detector.

The materials genome and CALPHAD

The mapping of the human genome is an important basis for the development of new medicals and medical treatments.Consequently,it has attracted tremendous research funding over the last decade.On June2011,the Materials Genome Initiative was announced by the US President Obama as collaboration on modeling and advanced materials databases.Unfortunately,the materials genome was given a rather vague definition in the announcement.However,the materials genome should be defined in analogy with biological genomes and one may then conclude that:at any moment,the performance of a specific material depends on its chemical composition(inherent property stored in its genome)and its environment(external interactions–processing–conditions during usage).The materials genome should thus be defined as a set of information encoded in the language of thermodynamics obtained by careful assessment of experimental data and quantum mechanical calculations from which certain conclusions about the material can be drawn.The CALPHAD databases contain the thermodynamic and kinetic properties of a materials system.Such databases allow the prediction of materials structure as well as its response to processing and usage conditions,and are major parts of integrated computational materials engineering.

Technology challenges for monolithically integrated waveguide demultiplexers

A short overview of integrated waveguide demultiplexers for different applications in future highly integrated optical communication systems is presented. Some fabricated devices based on amorphous silicon nanowire technology are described.

基于Budyko假设评估洮儿河流域中上游气候变化的径流影响

洮儿河流域中上游为我国东北典型生态敏感地区,近几十年来由于受到人类活动与气候变化的综合影响,一系列生态问题开始凸显。为更好的进行水资源管理,迫切需要准确评估气候变化及人类活动对径流的影响。本文基于Penman-Monteith公式计算研究区及其周边气象站点的潜在蒸散发,采用非参数Mann-Kendall检验及滑动T检验识别径流、降水及潜在蒸散发的趋势及突变点。发现作为整个研究区控制站点,洮南站年径流具有明显上升趋势并以1985年为突变点,据此将研究时段划分为基准期及变化期。然后利用降水及潜在蒸散数据,基于6种Budyko公式评估气候变化对年径流影响,结果表明气候因素约占45%。研究结论证实了人类活动对流域水文过程的确具有显著影响,增进了对该区水文水资源的认识。