The effect of Laves phases and nano-precipitates on the electrochemical corrosion resistance of Mg-Al-Ca alloys under alkaline conditions

The electrochemical corrosion mechanisms of Mg alloys were extensively studied in previous investigations of different chemical com-positions,modified surface states and various electrolyte conditions.However,recent research focused on the active state of Mg dissolution,leading to unresolved effects of secondary phases adjacent to a stableα-solid solution passive layer.The present study investigates the fundamental electrochemical corrosion mechanisms of three different Laves phases with varying phase morphologies and phase fractions in the passive state of Mg-Al-Ca alloys.The microstructure was characterized by(transmission-)electron microscopy and synchrotron-based transmission X-ray microscopy.The electrochemical corrosion resistance was determined with a standard three-electrode setup and advanced in-situ flow cell measurements.A new electrochemical activity sequence(C15>C36>α-Mg>C14)was obtained,as a result of a stable passive layer formation on theα-solid solution.Furthermore,nm-scale Mg-rich precipitates were identified within the Laves phases,which tend to inhibit the corrosion kinetics.

Ganoderma lucidum:a comprehensive review of phytochemistry,efficacy,safety and clinical study

Ganoderma lucidum,one of the most well-known edible fungi,is believed to be very beneficial for longevity and vitality.A long usage history suggests that G.lucidum has various clinical therapeutic effects.And experimental studies have confirmed that G.lucidum has multiple pharmacological effects,including antitumor,anti-microbial,anti-HIV protease,and antidiabetic activity and so on.With the deepening of research,more than 300 compounds have been isolated from G.lucidum.There is an increasing population of G.lucidum-based products,and its international development is expanding.Currently,G.lucidum has drawn much attention to its chemical composition,therapeutic effect,clinical value,and safety.This paper provides a comprehensive review of these aspects to enhance the global promotion of G.lucidum.

In-situ 3D contour measurement for laser powder bed fusion based on phase guidance

In-situ layerwise imaging measurement of laser powder bed fusion(LPBF)provides a wealth of forming and defect data which enables monitoring of components quality and powder bed homogeneity.Using high-resolution camera layerwise imaging and image processing algorithms to monitor fusion area and powder bed geometric defects has been studied by many researchers,which successfully monitored the contours of components and evaluated their accuracy.However,research for the methods of in-situ 3D contour measurement or component edge warping identification is rare.In this study,a 3D contour mea-surement method combining gray intensity and phase difference is proposed,and its accuracy is verified by designed experiments.The results show that the high-precision of the 3D contours can be achieved by the constructed energy minimization function.This method can detect the deviations of common ge-ometric features as well as warpage at LPBF component edges,and provides fundamental data for in-situ quality monitoring tools.

钛合金固相渗硼-稀土渗硼机理研究

表面强化处理可以大幅提升钛合金的耐磨性,也有利于钛合金在高温环境中应用。钛合金高温固相渗硼是重要的表面强化方式,添加稀土提高渗硼效率是重要技术手段。为深入研究稀土的渗硼催化机制,本文开展了900~1050℃渗硼试验,重点分析了渗硼剂在试验后的相组成变化。结果表明,稀土可通过与硼源、氧发生化学反应,生成熔点较低的稀土硼酸盐。本文对该硼酸盐发挥的作用进行了解释,论述了稀土在渗硼反应过程中的作用。经过渗硼的钛合金表面形成了TiB/TiB2双相渗层,显微组织分析表明该渗层与基材结合紧密、无孔洞缺陷。本文还对渗硼钛合金的拉伸性能、表面摩擦系数、维氏硬度、高温洛氏硬度、结合力等基础力学性能进行了测试,结果表明,渗硼钛合金具有优良的综合力学性能。

硼化铪粉末制备研究

硼化铪(HfB2)具有优异的抗氧化性能,作为超高温材料在耐磨涂层、航空领域具有极高的应用价值,而纯度是影响其应用的关键因素。本文采用烧结工艺制备HfB2粉末,利用X射线衍射仪、扫描电子显微镜、X射线能谱仪等表征了粉末的结晶性能、形貌、元素分布等。研究了硼源、混料方式对HfB2粉末结构的影响,测定C、O等杂质含量,通过差减法计算得HfB2纯度。结果表明,碳化硼(B4C)作为硼源、混料采用机械混合的HfB2性能最佳,X射线衍射中仅有HfB2结晶峰,扫描电镜中均为HfB2紧密团聚形貌,通过化学分析测定杂质含量,差减法计算HfB2纯度可达到98.19%。

Mantle plume:the dynamic setting of the origin of Early Paleozoic mafic dykes in Ziyang,Shaanxi Province,Southern Qinling Block,China

The mafic dykes(dolerites)during the Early Paleozoic are widely spread in Langao-Ziyang,southern Qiling Block,and the investigation on these dykes are very important.Previous studies have mainly focused on the Silurian mafic dykes;however,research on the Earlier Paleozoic mafic dykes is relatively weak at present.Therefore,the overall understanding of the mantle source and genetic dynamic setting during the Early Paleozoic in this area is lacking.To study the accurate age and origin of the Early Paleozoic mafic dykes in Ziyang,southern Shaanxi Province,the mafic dykes from dabacunand Qinmingzhai were selected and the petrology,zircon U-Pb chronology,geochemistry,and Sr-Nd-Hf isotopes were studied.Analysis indicates that the mafic dykes studied are mainly composed of dolerite,and they are the products of the Early Ordovician(475.8-480.7 Ma).Furthermore,the dolerites belong to alkaline rock series,and they are characterized by enrichment in LREE,Rb,Ba,Sr,Nb,(87Sr/86Sr)i=0.7020-0.7050,εNd(t)=3.0-4.0),εHf(t)=4.5-12.1,176Hf/177Hf=0.282681-0.282844.This suggests that the mafic dyke were derived from the partial melting of a depleted lithospheric mantle,and the genetic process is mainly controlled by the mantle plume based on the discussion of the genetic model.Furthermore,the genetic process experienced the separation and crystallization of olivine and clinopyroxene at the same time,with little crustal contamination.

Remaining Useful Life Estimation of Lithium-Ion Battery Based on Gaussian Mixture Ensemble Kalman Filter

The remaining useful life(RUL)prediction is a crucial indicator for the lithium-ion battery health prognostic.The particle filter(PF),used together with an empirical model,has become one of the most well-accepted techniques for RUL prediction.In this work,a novel filtering algorithm,named the Gaussian mixture model(GMM)-ensemble Kalman filter(EnKF)is proposed.It embeds the Gaussian mixture model in the EnKF framework to cope with the non-Gaussian feature of the system state space,and meanwhile address some of the major shortcomings of the PF.The GMM-EnKF and the PF are both applied on public data sets for RUL prediction and the simulation results show superiority of our proposed approach to the PF.

Optimal Dispatching Model Considering the Pumped Sto-rage Power Plant in Hunan

This paper made a research on the Intelligent Optimization Operating Modeling of Pumped Storage Power Station in Hunan Power Grid. First it introduces the characteristics of Hunan power grid and analysis the practical requirement of dispatching. Then it brings forward the intelligent optimization model and set up running model for pumped storage power station of Hei Mi-feng. At last, it introduces the application of pumped storage power station in Hunan power grid and proves the effectiveness of the optimization models.

Mechanism of capture section affecting an intake for atmosphere-breathing electric propulsion

Atmosphere-Breathing Electric Propulsion(ABEP)can compensate for lost momentum of spacecraft operating in Very Low Earth Orbit(VLEO)which has been widely concerned due to its excellent commercial potential.It is a key technology to improve the capture efficiency of intakes,which collect and compress the atmosphere for ABEP.In this paper,the mechanism of the capture section affecting capture efficiency is investigated by Test Particle Monte Carlo(TPMC)simulations with 3D intake models.The inner surface smoothness and average collision number are determined to be key factors affecting capture efficiency,and a negative effect growth model is accordingly established.When the inner surface smoothness is less than 0.2,the highest capture efficiency and its corresponding average collision number interval are independent of the capture section’s geometry and its mesh size.When the inner surface smoothness is higher than 0.2,the capture efficiency will decrease by installing any capture section.Based on the present results,the manufacturing process and material selection are suggested to be prioritized during the intake geometry design in engineering projects.Then,the highest capture efficiency can be achieved by adjusting the length and mesh size of the capture section.

Color-kinematics duality and dual conformal symmetry for a four-loop form factor in N=4 SYM

We obtain the integrand of full-color four-loop three-point form factor of the stress-tensor supermultiplet in N=4 SYM,based on the color-kinematics(CK)duality and generalized unitarity method.Our result not only manifests all dual Jacobi relations via CK duality but also contains 133 free parameters.This suggests the constructibility of the form factor at even higher loops via CK duality.We also find that the planar form factor has a hidden dual conformal symmetry in the lightlike limit of the operator momentum,which is checked up to four loops.

无中和器离子推力器的发展现状、关键技术及展望

离子推力器具有高比冲和高效率等优势,是目前应用最广泛的电推力器之一,但亦存在着系统结构复杂、关键部件繁多等缺点.无中和器离子推力器可以消除对中和器的依赖,实现离子推进系统结构的简化,从而减小推力器体积和重量并提高系统可靠性.本文首先归纳了传统离子推力器的原理、优势及限制,引出了无中和器离子推力器的概念,对其基本原理、技术优势及分类进行了介绍;随后从等离子体源的束流自中和技术出发,总结了无中和器离子推力器的发展现状;结合空间应用需求以及无中和器离子推力器的工作特点,分析了无中和器离子推力器的关键技术,提出应将工质选择、等离子体机理研究、磁过滤装置和栅极系统设计以及栅极射频电压灵活调控方法这四方面作为其研究重点,同时应该发展并完善新的推力器参数测量方法,进一步明确无中和器离子推力器的工作特性.

Dynamic compression behavior of TiZrNbV refractory high-entropy alloys upon ultrahigh strain rate loading

In this study,the dynamic compressive response behavior of a body-centered cubic(BCC)single-phase TiZrNbV refractory high-entropy alloy(RHEA)was investigated under impact at speeds of 313-1584 m s^(-1)using two-stage,gas-gun-driven,high-speed plate-impact experiments;recovery sample analysis;and theoretical calculations.The strain rate and pressure were approximately 10^(7) s^(−1) and 5.07-29.37 GPa,respectively.The results showed that the TiZrNbV RHEA had a Hugoniot elastic limit of 4.12-5.86 GPa and a spall strength of 1.84-2.03 GPa.The initial yield strength of the alloy showed a strong strain-rate dependence and could be described by the modified Zerilli-Armstrong model,while the phonon-damping effect was the main reason for its high strain-rate sensitivity.Microstructural analysis showed that the dynamic deformation of the TiZrNbV RHEA was controlled by the dislocation slip,dislocation proliferation,intersection of the deformation bands,and grain refinement.The analysis also showed that the intergranular,transgranular,and mixed-type cracks dominated the spall failure of the material.The dynamic Hall-Petch effect and pinning from the lattice distortion led to high dynamic yield strength.The critical strain rate for the phonon drag effect was positively related to the relative atomic mass and local strain field of the metals.Within the experimental loading range,the RHEA showed good structural stability,and simultaneously,the theoretical calculation method for the equation of state based on a cold-energy mixture could accurately predict its shock-response behavior.The valence-electron concentration(VEC)had a direct effect on the shock-compression properties of the HEAs;higher VEC implied more difficulty in compressing the HEAs.The findings of this study provide insights into understanding the mechanical response characteristics of RHEAs under extreme conditions such as high-speed impact and ultrahigh strain-rate loading.

High recoverable energy storage density of Na_(0.5)Bi_(0.5)TiO_(3) lead-free ceramics modified by Bi(Mg_(0.5)Hf_(0.5))O_(3)

Enhancing the availability and reliability of dielectric ceramic energy storage devices is of great importance.In this work,(1-x)Na_(0.5)Bi_(0.5)TiO_(3)-xBi(Mg_(0.5)Hf_(0.5))O_(3)(NBT-xBMH)lead-free ceramics were created utilizing a solid-state reaction technique.All NBT-xBMH ceramics have a single perovskite structure.With increasing BMH doping,the grain size shrinks drastically,which greatly enhances the breakdown electric field(310 kV/cm at x=0.25).Additionally,the relaxation behaviors of NBT-xBMH ceramics with high BMH content are more remarkable.Among all designed components,the NBT-0.25BMH ceramic exhibits the best energy storage performance with a high Wrec of 4.63 J/cm^(3) and anηof 75.1%at 310 kV/cm.The NBT-0.25BMH ceramic has exceptional resistance to fluctuations in both frequency(5-500 Hz)and temperature(30-100°C).Charge-discharge test shows that the NBT-0.25BMH ceramic has a quick discharge rate(t0.9<110 ns).With these properties,the NBT-0.25BMH ceramic may have applications in microdevices as well as in ultra-high power electronic systems.

Rationally designed Ti_(3)C_(2) MXene/CaIn_(2)S_(4) Schottky heterojunction for enhanced photocatalytic Cr(VI) reduction:Performance,influence factors and mechanism

As a highly toxic heavy metal,Cr(VI)reduction by developing high-efficiency photocatalysts is of great significance.Herein,we firstly design few-layer Ti_(3)C_(2) MXene(FTM)by the hand-operated shaking,show-ing dual advantages of structural stability and more exposed reactive sites.Then,a refluxed process is performed to fabricate FTM/CaIn_(2)S_(4)(FTC) composites,where 2D CaIn_(2)S_(4)(CIS) nanoplates are closely con-nected with 2D FTM to form Schottky junction.The optimal 1-FTC with the FTM/CIS mass ratio of 1 wt.%exhibits the highest activity toward photocatalytic Cr(VI)reduction under visible light.It is well eluci-dated that the broadened light absorption range and promoted charge carrier separation rate induced by the introduction of FTM are responsible for improving photocatalytic activity of CIS.During Cr(VI)photoreduction,1-FTC possesses excellent photo-stability and reusability.The effects of catalyst mass,co-existing ions,water sources and pH values on the Cr(VI)photoreduction efficiency are investigated.Pho-togenerated•O_(2)^(−)and e−are the main radical species accounting for Cr(VI)photoreduction over 1-FTC.The photocatalytic mechanism along with Cr(VI)removal pathway is exploited.This work may provide some insights into constructing FTM-based Schottky junctions for the efficient water purification.

Enhanced thermoelectric properties of NbCoSn half-Heuslers through in-situ nanocrystallization of amorphous precursors during the consolidation process

Tailoring nanostructures is a general approach used to obtain enhanced thermoelectric properties for halfHeusler compounds because the wide areas of grain and phase boundaries could be scattering centers that lower lattice thermal conductivity.However,a common fabrication method based on the sintering of crystalline precursors crushed from as-cast alloy ingots has limitations in obtaining a homogeneous microstructure without microsized impurity phases,owing to residual elemental segregation from casting.In this study,we used amorphous NbCoSn alloys as a precursor for the sintered specimen to obtain a homogeneous NbCoSn bulk specimen without microsized impurity phases and segregation,which led to the enhanced Seebeck coefficient due to the high purity of the half-Heusler phase after crystallization.Moreover,superplasticity originating from amorphous features enabled the powders to be largely deformed during the sintering process,even at a low sintering temperature(953 K).This resulted in less oxidation at both,the grain boundary and the interior,as the O diffusion pathway was blocked during the sintering process.As a result,the NbCoSn0.95Sb0.05 specimen using an amorphous precursor exhibited an enhanced zT of 0.7,due to the increase in the power factor and a decrease in lattice thermal conductivity compared to the specimen using a crystalline precursor.

Achieving ultra-broadband electromagnetic absorption of Ag regulated hollow Ag/CuO@CuS through balancing conduction loss and impedance matching

Excellent impedance matching and high conduction loss are important factors for the preparation of high-performance electromagnetic wave(EMW)absorbing materials,but these two properties are of-ten contradictory.In this work,three absorbers with unique hollow structures,H-Ag/CuO@CuS,H-O-Ag/CuO@CuS,and H-P-Ag/CuO@CuS,are designed and synthesized by adopting hollow CuO@CuS with double shell as carrier and silver nitrate as the structural regulator.The more voids coming from hol-low structures,window-opened structures,and stacked pores improve the impedance matching of these absorbers,and the introduction of elemental Ag effectively regulates the conduction loss.Therefore,a balance between impedance matching and conduction loss is achieved to improve the reflection loss(RL)value and broadens the absorbing band of the absorbers.In comparison to H-Ag/CuO@CuS and H-O-Ag/CuO@CuS(hollow structure with open window)in which elemental Ag is uniformly dispersed in the CuO layer,H-P-Ag/CuO@CuS exhibits more excellent EMW absorption performance due to more voids and an optimized conductive network arising from Ag/CuO pieces distributed between the hol-low Ag/CuO@CuS particles and Ag distributed in the CuS layer.When the thickness is 2.3 mm,H-P-Ag/CuO@CuS provides an ultra-wide electromagnetic absorption band of 8.56 GHz(9.44-18 GHz),in which the RL<-10 dB and the minimum reflection loss of-41 dB.

Slotless dispersion-flattened waveguides with more than five zero-dispersion wavelengths

We propose a new type of dispersion-flattened waveguide without a slot-assisted structure that can obtain an ultra-flat group velocity dispersion profile with five or six zero-dispersion wavelengths in the mid-infrared region.The dispersion profile becomes less sensitive to the waveguide dimensions due to the absence of the slot-assisted structure,making waveguide fabrication more friendly.The dispersion profile varies between−0.472 and 0.365 ps/(nm·km)over a 2665 nm bandwidth from 2885 nm to 5550 nm with a flatness of 3183.99 nm2·km/ps.Two different combinations of materials are demonstrated for dispersion flattening of the proposed waveguide structures.We also provide design guidance for the proposed waveguide structures with other combinations of materials.

Implementing a “free” tuberculosis (TB) care policy under the integrated model in Jiangsu, China: practices and costs in the real world

Background:In the 1990s,China introduced a“free”tuberculosis(TB)care policy under the national TB control program.Recently,as a part of a new TB diagnosis and treatment model,it has been recommended that the integrated model scale up.This paper examines whether or not TB designated hospitals in the selected project sites have provided TB care according to the national and local guidelines,and analyzes the actual practices and expenditures involved in completing TB treatment.It also explores the reasons why“free”TB care in China cannot be effectively implemented under the integrated model.Methods:This study was conducted in three counties of Zhenjiang city,Jiangsu province.Mixed methods were used,which comprised reviewing the national and local TB control guidelines,conducting TB patient surveys,collecting TB inpatient and outpatient hospital records,and conducting qualitative interviews with stakeholders.Descriptive statistics were used for quantitative data analysis across counties and in order to compare patients who received only outpatient care and those who received both outpatient and inpatient care.The chi-square test and analysis of variance were performed where necessary.Qualitative data were analyzed using the framework approach.Results:Although the national TB care guidelines recommend outpatient care as a basis for TB treatment in China,we found high hospital admission rates for TB patients ranging from 39%in Yangzhong county to 83%in Dantu county.Almost all outpatient TB patients paid for lab tests and over 80%paid for liver protection drugs and around 70%paid for image examinations.These three components accounted for three-quarters of the total outpatient expenditure.For patients who received only outpatient care,the total expenditure upon completion of TB treatment was on average 1,135 Chinese yuan.For patients who received outpatient and inpatient care,the total expenditure upon completion of TB treatment was 11,117 Chinese yuan.Conclusion:The“free”TB care policy under the integrated model has not been effectively implemented in China.There has been substantial spending on non-recommended services,examinations,and drugs for TB treatment.

Silver-catalyzed decarboxylative C-H functionalization of cyclic aldimines with aliphatic carboxylic acids

Silver-catalyzed decarboxylative C–H alkylation of cyclic aldimines with abundant aliphatic carboxylic acids has been realized under mild reaction conditions generating the corresponding products in moderate to good yields(32%–91%).In addition,a gram-scale reaction,late-stage modification of drug,synthetic transformation of the product,and further application of the catalytic strategy were also performed.Preliminary studies indicate that the reaction undergoes a radical process.

The Weighted Morrey Boundedness of Multilinear Singular Integral Operators on RD-Spaces

An RD-space X is a space of homogeneous type in the sense of Coifman and Weiss,which is equipped with a measure satisfying an additional reverse doubling property.In this paper we study the boundedness of multilinear singular integral operators in weighted Morrey spaces within the framework of RD-spaces.