Ground-based and additional science support for SMILE

The joint European Space Agency and Chinese Academy of Sciences Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission will explore global dynamics of the magnetosphere under varying solar wind and interplanetary magnetic field conditions,and simultaneously monitor the auroral response of the Northern Hemisphere ionosphere.Combining these large-scale responses with medium and fine-scale measurements at a variety of cadences by additional ground-based and space-based instruments will enable a much greater scientific impact beyond the original goals of the SMILE mission.Here,we describe current community efforts to prepare for SMILE,and the benefits and context various experiments that have explicitly expressed support for SMILE can offer.A dedicated group of international scientists representing many different experiment types and geographical locations,the Ground-based and Additional Science Working Group,is facilitating these efforts.Preparations include constructing an online SMILE Data Fusion Facility,the discussion of particular or special modes for experiments such as coherent and incoherent scatter radar,and the consideration of particular observing strategies and spacecraft conjunctions.We anticipate growing interest and community engagement with the SMILE mission,and we welcome novel ideas and insights from the solar-terrestrial community.

我国4个大城市空气PM_(2.5)、PM_(10)污染及其化学组成

报告了 1 995～ 1 996年在中国的广州、武汉、兰州、重庆 4大城市 8个采样点 PM2 .5 、PM2 .5～ 1 0 和 PM1 0 的监测结果。结果表明 ,1 995年 PM2 .5 年均值浓度为 57～ 1 60 μg/m3,比美国 1 997年颁布的标准值 (1 5μg/m3)高 2 .8～ 9.7倍。PM1 0 年日均值为 95～ 2 73μg/m3。除武汉市 1个对照点外 ,其余 7个监测点的 PM1 0 均超过我国空气质量二极标准 (1 0 0μg/m3)2 8%～ 1 73 % ,比美国标准 (50μg/m3)超过更多 ,说明污染是相当严重的。用 XRF分析了 PM2 .5 、PM2 .5～ 1 0 中 4 2种化学元素 ,结果表明 ,燃煤、燃油和其它工业污染的元素 As、Pb、Se、Zn、Cu、Cl、Br、S在这些颗粒物中有明显富集 ,特别是在PM2 .5 中的富集倍数达数十倍至数万倍 。

广泛耐药革兰阴性菌感染的实验诊断、抗菌治疗及医院感染控制:中国专家共识

广泛耐药革兰阴性杆菌(XDR-GNB),是指除1~2类抗菌药物(主要指多黏菌素和替加环素)外,几乎对所有类别抗菌药物均不敏感的革兰阴性杆菌。XDR-GNB常见于肠杆菌科细菌、鲍曼不动杆菌、铜绿假单胞菌和嗜麦芽窄食单胞菌等。近年来,中国XDR-GNB的发生率呈不断上升趋势,由于缺乏有效的治疗药物,XDR-GNB感染成为公共卫生安全的一大威胁。我国有关感染的临床、微生物学及临床药理学专家们就XDR-GNB感染的实验室诊断、临床诊疗和医院感染控制等问题深入讨论,形成此共识。其中细菌药敏试验的抗菌药物品种及结果判定标准遵循美国临床和实验室标准化协会(CLSI)、欧洲抗菌药物敏感性试验委员会(EUCAST)或美国食品与药物监督管理局(FDA)的指南。研究提示长疗程使用广谱抗菌药物是引发XDR-GNB感染最重要的危险因素。根据现有的临床研究和实验室数据,共识提供治疗各种XDRGNB感染的联合用药推荐方案,其中常用的抗菌药物有替加环素、多黏菌素、碳青霉烯类、氨基糖苷类和磷霉素等。同时建议实行严格的感染控制措施,包括手卫生、接触隔离、主动筛查、环境消毒、去定植和抗菌药物应用管理等遏制XDRGNB感染的传播。

DIRECTIONALLY SOLIDIFIED MICROSTRUCTURE OF AN ULTRA-HIGH TEMPERATURE Nb-Si-Ti-Hf-Cr-Al ALLOY

The directionally solidified samples of an ultra-high temperature Nb-Si-Ti-Hf-Cr-Al alloy have been prepared with the use of an electron beam floating zone melting (EBFZM) furnace, and their microstructural characteristics have been analyzed. All the primary dendrites of Nb solid solution (Nbss), eutectic colonies of Nba, plus (Nb, Ti)3 Si/(Nb, Ti)5 Si3 and chains of (Nb, Ti)3 Si/(Nb, Ti)5 Si3 plates align along the growth direction of the samples. With increasing of the withdrawing rate, the microstructure is refined, and the amounts of Nbss+ (Nb, Ti)3 Si/(Nb, Ti)5 Si3 eutectic colonies and (Nb, Ti)3 Si/(Nb, Ti)5 Si3 plates increase. There appear nodes in the (Nb, Ti)3 Si/(Nb, Ti)5 Si3 plates.

Statistical moment-based structural damage detection method in time domain

A novel structural damage detection method with a new damage index,i.e.,the statistical moment-based damage detection（SMBDD） method in the frequency domain,has been recently proposed.The aim of this study is to extend the SMBDD method in the frequency domain to the time domain for building structures subjected to non-Gaussian and non-stationary excitations.The applicability and effectiveness of the SMBDD method in the time domainis verified both numerically and experimentally.Shear buildings with various damage scenarios are first numerically investigated in the time domain taking into account the effect of measurement noise.The applicability of the proposed method in the time domain to building structures subjected to non-Gaussian and non-stationary excitations is then experimentally investigated through a series of shaking table tests,in which two three-story shear building models with four damage scenarios aretested.The identified damage locations and severities are then compared with the preset values.The comparative results are found to be satisfactory,and the SMBDD method is shown to be feasible and effective for building structures subjected to non-Gaussian and non-stationary excitations.

Phase stability,elastic properties and electronic structures of Mg-Y intermetallics from first-principles calculations

The phase stability,elastic properties and electronic structures of three typical Mg-Y intermetallics including Mg_(24)Y_(5),Mg_(2)Y and MgY are systematically investigated using first-principles calculations based on density functional theory.The optimized structural parameters including lattice constants and atomic coordinates are in good agreement with experimental values.The calculated cohesive energies and formation enthalpies show that either phase stability or alloying ability of the three intermetallics is gradually enhanced with increasing Y content.The single-crystal elastic constants C_(ij) of Mg-Y intermetallics are also calculated,and the bulk modulus B,shear modulus G,Young's modulus E,Poisson ratio v and anisotropy factor A of polycrystalline materials are derived.It is suggested that the resistances to volume and shear deformation as well as the stiffness of the three intermetallics are raised with increasing Y content.Besides,these intermetallics all exhibit ductile characteristics,and they are isotropic in compression but anisotropic to a certain degree in shear and stiffness.Comparatively,Mg_(24)Y_(5) presents a relatively higher ductility,while MgY has a relatively stronger anisotropy in shear and stiffness.Further analysis of electronic structures indicates that the phase stability of Mg-Y intermetallics is closely related with their bonding electrons numbers below Fermi level.Namely,the more bonding electrons number below Fermi level corresponds to the higher structural stability of Mg-Y intermetallics.

Enhancing mechanical behavior of micaceous soil with jute fibers and lime additives

Micaceous soils are common in many tropical countries and regions,and in some locations with moderate climate.The soils are spongy and unstable when loaded and are not considered suitable as construction material in earth structures.To resolve the issue,this work examined performance of micaceous soil reinforced with a combination of jute fibers,hydrated lime or slag-lime.A total of 28 sample sets were prepared at various dosages.Unconfined compression tests were conducted on the samples cured for 7 d and 28 d,respectively.The test results suggested that the unconfined compressive strength(UCS)and material stiffness were increased with the inclusion of up to 1%fiber and decreased if additional fibers were used.The ductility was improved consistently with up to 1.5%fiber content.The inclusions of fibers combined with hydrated lime or slag-lime further enhanced strength and stiffness of micaceous soil,and the improvement depended on the dosages used.For the dosages examined,jute fibers outweighed lime and slag in gaining ductility,and the optimal fiber content was 1%where strength and ductility were considered.

VISCO-PLASTIC CONSTITUTIVE MODEL FOR UNIAXIAL AND MULTIAXIAL RATCHETING AT ELEVATED TEMPERATURES

Based on the experimental results of the ratcheting for SS304 stainless steel, a new visco-plastic cyclic constitutive model was established to describe the uniaxial and multiaxial ratcheting of the material at room and elevated temperatures within the framework of unified visco-plasticity. In the model, the temperature dependence of the ratcheting was emphasized, and the dynamic strain aging occurred in the temperature range of 4 00-600℃ for the material was taken into account particularly. Finally, the prediction capability of the developed model was checked by comparing to the corresponding experimental results.

Optimization of hole-boring radiation pressure acceleration of ion beams for fusion ignition

In contrast to ion beams produced by conventional accelerators,ion beams accelerated by ultrashort intense laser pulses have advantages of ultrashort bunch duration and ultrahigh density,which are achieved in compact size.However,it is still challenging to simultaneously enhance their quality and yield for practical applications such as fast ion ignition of inertial confinement fusion.Compared with other mechanisms of laser-driven ion acceleration,the hole-boring radiation pressure acceleration has a special advantage in generating high-fluence ion beams suitable for the creation of high energy density state of matters.In this paper,we present a review on some theoretical and numerical studies of the hole-boring radiation pressure acceleration.First we discuss the typical field structure associated with this mechanism,its intrinsic feature of oscillations,and the underling physics.Then we will review some recently proposed schemes to enhance the beam quality and the efficiency in the hole-boring radiation pressure acceleration,such as matching laser intensity profile with target density profile,and using two-ion-species targets.Based on this,we propose an integrated scheme for efficient high-quality hole-boring radiation pressure acceleration,in which the longitudinal density profile of a composite target as well as the laser transverse intensity profile are tailored according to the matching condition.

Superconductivity Observed in Tantalum Polyhydride at High Pressure

We report experimental discovery of tantalum polyhydride superconductor.It was synthesized under highpressure and high-temperature conditions using diamond anvil cell combined with in situ high-pressure laser heating techniques.The superconductivity was investigated via resistance measurements at pressures.The highest superconducting transition temperature T_(c)was found to be~30 K at 197 GPa in the sample that was synthesized at the same pressure with~2000 K heating.The transitions are shifted to low temperature upon applying magnetic fields that support the superconductivity nature.The upper critical field at zero temperatureμ_0H_(c2)(0)of the superconducting phase is estimated to be~20 T that corresponds to Ginzburg-Landau coherent length~40 A.Our results suggest that the superconductivity may arise from 143d phase of TaH_(3).It is,for the first time to our best knowledge,experimental realization of superconducting hydrides for the VB group of transition metals.

Preparation and growth mechanism of nickel nanowires under applied magnetic field

Nickel nanowires with large aspect ratio of up to 300 have been prepared by a hydrazine hydrate reduction method under applied magnetic field. The diameter of nickel nanowires is about 200 nm and length up to 60 μm. The role of magnetic field on the growth of magnetic nanowires is discussed and a magnetic nanowire growth mechanism has been proposed. Nickel ions are firstly reduced to nickel atoms by hydrazine hydrates in a strong alkaline solution and grow into tiny spherical nanoparticles. Then, these magnetic particles will align under a magnetic force and form linear chains. Furthermore, the as-formed chains can enhance the local magnetic field and attract other magnetic particles nearby, resulting finally as linear nanowires. The formation and the size of nanowires depend strongly on the magnitude of applied magnetic field.

Mitigating parametric instabilities in plasmas by sunlight-like lasers

Sunlight-like lasers that have a continuous broad frequency spectrum,random phase spectrum,and random polarization are formulated theoretically.With a sunlight-like laser beam consisting of a sequence of temporal speckles,the resonant three-wave coupling that underlies parametric instabilities in laser–plasma interactions can be greatly degraded owing to the limited duration of each speckle and the frequency shift between two adjacent speckles.The wave coupling can be further weakened by the random polarization of such beams.Numerical simulations demonstrate that the intensity threshold of stimulated Raman scattering in homogeneous plasmas can be doubled by using a sunlight-like laser beam with a relative bandwidth of∼1%as compared with a monochromatic laser beam.Consequently,the hot-electron generation harmful to inertial confinement fusion can be effectively controlled by using sunlight-like laser drivers.Such drivers may be realized in the next generation of broadband lasers by combining two or more broadband beams with independent phase spectra or by applying polarization smoothing to a single broadband beam.

Nonlinear static and dynamic responses of an electrically actuated viscoelastic microbeam

On the basis of the Euler-Bernoulli hypothesis, nonlinear static and dynamic responses of a viscoelastic microbeam under two kinds of electric forces [a purely direct current （DC） and a combined current composed of a DC and an alternating current] are studied. By using Taylor series expansion, a governing equation of nonlinear integro-differential type is derived, and numerical analyses are performed. When a purely DC is applied, there exist an instantaneous pull-in voltage and a durable pull-in voltage of which the physical meanings are also given, whereas under an applied combined current, the effect of the element relaxation coefficient on the dynamic pull-in phenomenon is observed where the largest Lyapunov exponent is taken as a criterion for the dynamic pull-in instability of viscoelastic microbeams.

ANNEXATION OF TWO KINDS OF SOLUTION IN BINARY METALLIC MELTS

After investigation on the thermodynamic properties of a small number of binarymetallic melts, the structural units of which cannot be wholly determined by the cor-responding phase diagrams, it was found that they can be determined by the principleof annexation of two kinds of solutions in binary metallic melts. According to theprinciple of annexation, calculating models of mass action concentrations for severalbinary metallic melts have been formulated. The calculated results agree well withpractice, showing that this principle is a reliable basis for determination of the struc-tural units for some binary metallic melts.

热辅助磁存储介质高性能润滑薄膜研究

一种具有良好热稳定性的新式润滑剂被开发并应用于在热辅助磁存储(HAMR)介质,达到存储面密度在1 Tb/in2或更高。与当前所通用的商业润滑剂相比,这种新近开发的润滑剂薄膜能够经受激光照射而不损坏,而Z–dol膜在相同的实验条件下被完全破坏。摩擦因数和浸润性也优于其它用于热辅助磁存储(HAMR)介质保护材料。

A COMPONENT-SPECIFIC ALLOY DESIGN OF TiAl INTERMETALLICS

The metallographic observation and analyses of TiAl alloy cast ingots revealed that the preferably arranged γ/α_2 lamellar microstructure can be obtained in columnar dendritic cast ingot through controlling the Ti/Al atomic ratio. The experiments conf irmed that the preferably arranged γ/α_2 lamellar microstructure has excellent tensile strength and fracture toughness and tolerant tensile plasticity when the stress is applied parallel to the γ/α_2 interface.Based on these results and the working condition of the turbine blades,a component-specific alloy design has been suggested.

Optimizing micaceous soil stabilization using response surface method

Micaceous soil is a problematic soil due to its low strength and poor ductility.In this context,the performances of micaceous soils were improved by applying a combination of granulated blast furnace slag,fiber and polymer additive.The dosages examined included 0%e30%mica,3%e15%slag and 0.25%e1.25%fiber by weight,and 0.1e0.5 g/L polymer additive.Most of the combinations were found to increase the material strength and ductility,yet to be optimized.To refine the dosage,response surface method was used to conduct experimental design and develop predictive models for material strength.The developed models formulate the material strength as a nonlinear function of dosages and,by interrogating it,can optimize additive contents in terms of target requirements.The models were verified through trials and can be used to determine dosages to upscale micaceous soils to field conditions.

ARTIFICIAL NEURAL NETWORKS BASED GEARS MATERIAL SELECTION HYBRID INTELLIGENT SYSTEM

An artificial neural networks(ANNs) based gear material selection hybrid intelligent system is established by analyzing the individual advantages and weakness of expert system (ES) and ANNs and the applications in material select of them. The system mainly consists of tow parts: ES and ANNs. By being trained with much data samples, the back propagation (BP) ANN gets the knowledge of gear materials selection, and is able to inference according to user input. The system realizes the complementing of ANNs and ES. Using this system, engineers without materials selection experience can conveniently deal with gear materials selection.

FORMATION OF SILICONIZED LAYER ON TiAl-BASED ALLOY AND THE OXIDATION RESISTANCE

The Ti-48Al alloy was pack siliconized with 15%Si+85%Al2O3. The microstructure of the siliconized coating on the TiAl-based alloy was analyzed and its effect on oxidation resistance was investigated. The specimens before and after cycle oxidation were examined by XRD and SEM equipped with XEDS. The results showed that the coating is composed of a thin Al2O3 outer layer and a composite inner layer of Ti5Si3 with an appropriate amount of Al2O3 dispersed in. Cycle oxidation tests showed that the high temperature oxidation resistance of TiAl-based alloy was greatly improved by forming such composite coating. No spaliation and crack happened and the weight gain was very small after cycle oxidation at 900℃ for 314h.

HIGH-TEMPERATURE TENSILE FRACTURE BEHAVIOR OF DIRECTIONALLY SOLIDIFIED Ni,Cr,Al-TaC EUTECTIC SUPERALLOY

The high-temperature tensile fracture behavior of the Ni, Cr, Al-TaC eutectic superal-loy directionally solidified under high temperature gradient is investigated. The high-temperature tensile fracture of this in situ composite has ductile character with lots of ductile nests whose diameters decrease with the increasing solidification rates. The maximum σb and δ are respectively 668.5MPa and 19.6%. There is α TaC whisker in the center of each nest, and the deformation of γ' and TaC is uneven. The high-temperature tensile behavior cannot be explained by the rule of mixtures but is decided by the formation of the plastic deformation band. The crack extension model is given.