Ultrasmall CoS nanoparticles embedded in heteroatom-doped carbon for sodium-ion batteries and mechanism explorations via synchrotron X-ray techniques

Transition metal sulfides have been regarded as promising anode materials for sodium-ion batteries(SIB).However,they face the challenges of poor electronic conductivity and large volume change,which result in capacity fade and low rate capability.In this work,a composite containing ultrasmall CoS(~7 nm)nanoparticles embedded in heteroatom(N,S,and O)-doped carbon was synthesized by an efficient one-step sulfidation process using a Co(Salen)precursor.The ultrasmall CoS nanoparticles are beneficial for mechanical stability and shortening Na-ions diffusion pathways.Furthermore,the N,S,and O-doped defect-rich carbon provides a robust and highly conductive framework enriched with active sites for sodium storage as well as mitigates volume expansion and polysulfide shuttle.As anode for SIB,CoS@HDC exhibits a high initial capacity of 906 mA h g^(-1)at 100 mA g^(-1)and a stable long-term cycling life with over 1000 cycles at 500 mA g^(-1),showing a reversible capacity of 330 mA h g^(-1).Meanwhile,the CoS@HDC anode is proven to maintain its structural integrity and compositional reversibility during cycling.Furthermore,Na-ion full batteries based on the CoS@HDC anode and Na_(3)V_(2)(PO_(4))_(3)cathode demonstrate a stable cycling behavior with a reversible specific capacity of~200 m A h g^(-1)at least for 100 cycles.Moreover,advanced synchrotron operando X-ray diffraction,ex-situ X-ray absorption spectroscopy,and comprehensive electrochemical tests reveal the structural transformation and the Co coordination chemistry evolution of the CoS@HDC during cycling,providing fundamental insights into the sodium storage mechanism.

Applying Analytical Derivative and Sparse Matrix Techniques to Large-Scale Process Optimization Problems

The performance of analytical derivative and sparse matrix techniques applied to a traditional dense sequential quadratic programming (SQP) is studied, and the strategy utilizing those techniques is also presented.Computational results on two typical chemical optimization problems demonstrate significant enhancement in efficiency, which shows this strategy is promising and suitable for large-scale process optimization problems.

Tribological Behaviour of Aluminium/Alumina/Graphite Hybrid Metal Matrix Composite Using Taguchi’s Techniques

Tribological behaviour of aluminium alloy (Al-Si10Mg) reinforced with alumina (9%) and graphite (3%) fabricated by stir casting process was investigated. The wear and frictional properties of the hybrid metal matrix composites was studied by performing dry sliding wear test using a pin-on-disc wear tester. Experiments were conducted based on the plan of experiments generated through Taguchi’s technique. A L27 Orthogonal array was selected for analysis of the data. Investigation to find the influence of applied load, sliding speed and sliding distance on wear rate, as well as the coefficient of friction during wearing process was carried out using ANOVA and regression equations for each response were developed. Objective of the model was chosen as ‘smaller the better’ characteristics to analyse the dry sliding wear resistance. Results show that sliding distance has the highest influence followed by load and sliding speed. Finally, confirmation tests were carried out to verify the experimental results and Scanning Electron Microscopic studies were done on the wear surfaces.

Review on preparation techniques of particle reinforced metal matrix composites

This paper reviews the investigation status of the techniques for preparation of metal matrix composites and the research outcomes achieved recently. The mechanisms, characteristics, application ranges and levels of development of these preparation techniques are analyzed. The advantages and the disadvantages of each technique are synthetically evaluated. Lastly, the future directions of research and the prospects for the preparation techniques of metal matrix composites are forecasted.

A SPARSE MATRIX TECHNIQUE FOR SIMULATING SEMICONDUCTOR DEVICES AND ITS ALGORITHMS

A novel sparse matrix technique for the numerical analysis of semiconductor devicesand its algorithms are presented.Storage scheme and calculation procedure of the sparse matrixare described in detail.The sparse matrix technique in the device simulation can decrease storagegreatly with less CPU time and its implementation is very easy.Some algorithms and calculationexamples to show the time and space characteristics of the sparse matrix are given.

Optimization of Friction and Wear Behaviour in Hybrid Metal Matrix Composites Using Taguchi Technique

Al-7075 alloy-base matrix, reinforced with mixtures of silicon carbide (SiC) and boron carbide (B4C) particles, know as hybrid composites have been fabricated by stir casting technique (liquid metallurgy route) and optimized at different parameters like sliding speed, applied load, sliding time, and percentage of reinforcement by Taguchi method. The specimens were examined by Rockwell hardness test machine, Pin on Disc, Scanning Electron Microscope (SEM) and Optical Microscope. A plan of experiment generated through Taguchi’s technique is used to conduct experiments based on L27 orthogonal array. The developed ANOVA and the regression equations were used to find the optimum wear as well as co-efficient of friction under the influence of sliding speed, applied load, sliding time and percentage of reinforcement. The dry sliding wear resistance was analyzed on the basis of “smaller the best”. Finally, confirmation tests were carried out to verify the experimental results.

Preparation technique of SiCp reinforced Al matrix composite

A new preparation technique-"block dispersal and cast" method is introduced, and three kinds of powder mixing methods, vertical, horizontal and inclining styles, are compared. The results demonstrate that the inclining style is the best way to mix powders. The Al and nano SiC powders are pressed into blocks, dipped into molten Al, stirred into mold so that SiC/Al matrix composites can be obtained at last. The microstructure of SiC particle reinforced Al matrix composite prepared by "block dispersal and cast" method have been studied using scanning electron microscopy (SEM). Phase analysis has also been conducted by means of X-ray diffraction (XRD). The results show that nano SiC particles can be dispersed uniformly in Al matrix. Thus, it is feasible to prepare SiC particle reinforced Al matrix composites by this method.

AINV AND BILUM PRECONDITIONING TECHNIQUES

It was proposed that a robust and efficient parallelizable preconditioner for solving general sparse linear systems of equations, in which the use of sparse approximate inverse (AINV) techniques in a multi-level block ILU (BILUM) preconditioner were investigated. The resulting preconditioner retains robustness of BILUM preconditioner and has two advantages over the standard BILUM preconditioner: the ability to control sparsity and increased parallelism. Numerical experiments are used to show the effectiveness and efficiency of the new preconditioner.

Correction of failure in antenna array using matrix pencil technique

In this paper a non-iterative technique is developed for the correction of faulty antenna array based on matrix pencil technique（MPT）. The failure of a sensor in antenna array can damage the radiation power pattern in terms of sidelobes level and nulls. In the developed technique, the radiation pattern of the array is sampled to form discrete power pattern information set. Then this information set can be arranged in the form of Hankel matrix（HM） and execute the singular value decomposition（SVD）. By removing nonprincipal values, we obtain an optimum lower rank estimation of HM. This lower rank matrix corresponds to the corrected pattern. Then the proposed technique is employed to recover the weight excitation and position allocations from the estimated matrix. Numerical simulations confirm the efficiency of the proposed technique, which is compared with the available techniques in terms of sidelobes level and nulls.

Novel stability criteria for fuzzy Hopfield neural networks based on an improved homogeneous matrix polynomials technique

The global stability problem of Takagi-Sugeno（T-S） fuzzy Hopfield neural networks（FHNNs） with time delays is investigated.Novel LMI-based stability criteria are obtained by using Lyapunov functional theory to guarantee the asymptotic stability of the FHNNs with less conservatism.Firstly,using both Finsler＇s lemma and an improved homogeneous matrix polynomial technique,and applying an affine parameter-dependent Lyapunov-Krasovskii functional,we obtain the convergent LMI-based stability criteria.Algebraic properties of the fuzzy membership functions in the unit simplex are considered in the process of stability analysis via the homogeneous matrix polynomials technique.Secondly,to further reduce the conservatism,a new right-hand-side slack variables introducing technique is also proposed in terms of LMIs,which is suitable to the homogeneous matrix polynomials setting.Finally,two illustrative examples are given to show the efficiency of the proposed approaches.

Taguchi Technique for the Simultaneous Optimization of Tribological Parameters in Metal Matrix Composite

Taguchi methods have proved to be successful over the last two decades for improvement of product quality and process performance. This study is carried out to simultaneously optimize the tribological properties: wear rate and frictional force of aluminum metal matrix composite. Al-Cu-Mg alloy reinforced with 6 Wt % of titanium dioxide was prepared using stir casting method. Dry sliding wear test was conducted to understand the tribological behavior of samples. The experiments were conducted as per the Taguchi design of experiment. The wear parameters chosen for the experiment were: sliding speed and load and sliding distance. Each parameter was assigned three levels. The experiment consists of 27 tests according to L27 orthogonal array. Signal to noise ratio analysis has been carried out to determine optimal parametric condition, which yields minimum wear rate and frictional force. Harrington’s desirability functional method is adopted for multifunctional optimization of tribological parameters and the confirmation experiments were conducted to verify the predicted model.

PROCESSINGTECHNIQUESANDCHARACTERIZATIONOFCERAMICFIBERREINFORCEDALUMINIUMCOMPOSITES

This paper relates to the fabrication of aluminium matrix composites with various amounts of Al 2O 3 fiber and SiC whiskers by rheocasting, powder metallurgy process and liquid metal infiltration process. To analyze wetting characteristics, the cross sections of composites are examined by scanning electron microscopy(SEM). The bending tests and microhardness tests are performed to evaluate mechanical properties of composites. The results show that the composites produced by liquid metal infiltration give better properties than those produced by rheocasting or powder metallurgy process, primarily due to the decrease of porosity and reinforcement cluster. For liquid metal infiltration composites, a good adhesion between the fiber and matrix is found. Three points bending test results show that there is an increase in flexural modulus with reinforcement contents. In addition, a series of microhardness tests are conducted to determine the effect of heat treatment on the mechanical property of Al 2O 3/Al composites.

基于TOPSIS法和波士顿矩阵的医院神经专科能力评估研究

目的通过对以神经科学集群建设为特色的三级甲等医院的神经专科能力进行评估,为国内医院的特色专科建设提供参考。方法从服务能力、技术能力、质量安全和服务效率4个维度建立神经外科、神经内科专科能力评估指标体系,通过优劣解距离(technique for order preference by similarity to ideal solution,TOPSIS)法纵向比较首都医科大学附属北京天坛医院神经专科2019—2023年发展趋势,并采用波士顿矩阵深入分析神经专科各亚专业建设情况。结果2019—2023年首都医科大学附属北京天坛医院神经专科TOPSIS综合得分指数呈上升趋势。神经外科以胶质瘤诊治为主的肿瘤专业1,在技术能力和质量安全方面得分指数最高;神经内科以脑血管病为主的亚专业,在技术能力和服务效率方面得分指数较高,以上两个亚专业在波士顿矩阵中均处于优势巩固区。结论2019—2023年首都医科大学附属北京天坛医院神经专科诊治能力不断提升。神经外科亚专业中,专科能力排名最高的为肿瘤专业1,诊疗技术难度较高,同时医疗质量负性事件发生率低。神经内科各亚专业中,脑血管专业诊疗技术难度高且服务高效。

3D打印技术用于经鼻蝶窦入路垂体腺瘤切除术应用效果及对血清MMP-9和IGF-1水平的影响

目的:探究3D打印技术在经鼻蝶窦入路垂体腺瘤(PA)切除术的应用效果及对血清基质金属蛋白酶-9(MMP-9)和胰岛素样生长因子-1(IGF-1)水平的影响。方法:选取2020年5月至2022年5月秦皇岛市第一医院收治的84例PA患者,按照随机数表法将其分为观察组和对照组,每组42例。对照组行经鼻蝶窦入路垂体腺瘤切除术,观察组行经鼻蝶窦入路垂体腺瘤切除术联合应用3D打印技术,比较两组肿瘤切除效果、围术期指标、视力改善情况、MMP-9和IGF-1水平,以及鼻腔功能的鼻气道阻力(NAR)、T&T嗅觉测试评分及并发症。结果:观察组肿瘤切除效果优于对照组,差异有统计学意义(U=2.286,P<0.05);观察组手术时间、术中出血量及住院时间均少于对照组,差异有统计学意义(t=4.780、11.438、11.842,P<0.05);术后3 d、7 d时观察组血清MMP-9和IGF-1水平低于对照组,差异有统计学意义(F=7.526、4.985,P<0.05);术后1个月、3个月时观察组NAR及T&T嗅觉测试评分低于对照组,差异有统计学意义(F=6.359、8.436,P<0.05);两组视力视野改善情况及并发症发生率比较,差异无统计学意义(P>0.05)。结论:3D打印技术用于经鼻蝶窦入路垂体腺瘤切除术可提高肿瘤切除效果,优化手术操作,减少创伤,有利于减轻疼痛,改善嗅觉功能与视力视野,并能降低血清MMP-9、IGF-1水平,且安全性较高。

FCC催化剂传质强化活性位利用效率的可视化分析

流化催化裂化(FCC)催化剂传质性能抑制活性位利用效率是影响其催化性能的关键因素,选用6种不同基质材料制备的FCC催化剂样品,在系统分析催化孔结构和酸性质的基础上,利用激光共聚焦荧光显微成像技术和吸附穿透曲线法模拟考察了重油大分子的传质扩散行为;并运用单分子荧光成像技术,以B酸中心催化噻吩低聚反应生成低聚物的数量作为判据考察了系列催化剂的活性位利用效率。研究发现,相比于传统的高岭土和拟薄水铝石作为基质材料,本课题组设计开发的大孔富B酸的基质材料(APM-9)明显优化了大分子在FCC催化剂上的传质性能,从而显著提升了活性位的利用效率。发展了一种新颖的FCC催化剂结构参数与其传质性能、酸中心利用效率构效关系建立的方法,可为催化剂基质材料的设计和优化提供数据支撑和理论指导。

Exact Tail Asymptotics for a Queueing System with a Retrial Orbit and Batch Service

This paper discusses a queueing system with a retrial orbit and batch service, in which the quantity of customers’ rooms in the queue is finite and the space of retrial orbit is infinite. When the server starts serving, it serves all customers in the queue in a single batch, which is the so-called batch service. If a new customer or a retrial customer finds all the customers’ rooms are occupied, he will decide whether or not to join the retrial orbit. By using the censoring technique and the matrix analysis method, we first obtain the decay function of the stationary distribution for the quantity of customers in the retrial orbit and the quantity of customers in the queue. Then based on the form of decay rate function and the Karamata Tauberian theorem, we finally get the exact tail asymptotics of the stationary distribution.

CLEFIA动态密码结构的零相关线性区分器构造研究

随着分组密码应用研究的不断深入,研究者发现,“动态可变”分组密码设计可有效提升分组密码算法的应用灵活性和部署安全性。CLEFIA算法遵循“动态可变”思想,一些学者对CLEFIA算法的线性变换层加以改进,使得第6t(t≥1)轮中的扩散层可以从{0,1}4上的多个线性双射变换中任意选取。为分析评估CLEFIA动态密码结构的安全性能,文章主要采取零相关线性分析理论,利用中间相错技术和矩阵表示方法,分析构造CLEFIA动态密码结构的零相关线性区分器。研究证明,在轮函数为双射的前提条件下,CLEFIA动态密码结构动态线性层控制参数μ_(i)∈F_(2),(0≤i≤4)无论取何值,总存在8轮零相关线性区分器;当控制参数μ_(0)=0时,存在9轮零相关线性区分器。

基于压电筒状叠堆的无线金属腐蚀探针设计及性能研究

基于压电筒状叠堆和压电阻抗技术提出了一种由压电筒状叠堆和金属杆组成的新型金属腐蚀探针。建立了多层结构探针纵向振动的传递矩阵模型,导出了电学阻抗方程,求得了第一阶谐振频率和反谐振频率,并与已有文献的特例结果进行了对比,验证了理论求解的正确性。此外,采用理论分析、人造定量腐蚀试验、温度敏感试验、加速腐蚀试验和无线阻抗测试试验系统地研究了探针的性能。研究结果表明:探针的第一阶谐振频率和反谐振频率随着杆长减小而增大,随着腐蚀天数的增加而增大,随着温度的增大而减小;无线阻抗系统测量的阻抗谱与传统阻抗分析仪的测量结果一致性较好。研究成果为开发无线定量测量的新型金属腐蚀探针提供重要参考。

An Evaluation of the Critical Success Factors in Sustainable Food Supply Chains in Developing Countries

Food is one of the biggest industries in developed and underdeveloped countries. Supply chain sustainability is essential in established and emerging economies because of the rising acceptance of cost-based outsourcing and the growing technological, social, and environmental concerns. The food business faces serious sustainability and growth challenges in developing countries. A comprehensive analysis of the critical success factors (CSFs) influencing the performance outcome and the sustainable supply chain management (SSCM) process. A theoretical framework is established to explain how they are used to examine the organizational aspect of the food supply chain life cycle analysis. This study examined the CSFs and revealed the relationships between them using a methodology that included a review of literature, interpretative structural modeling (ISM), and cross-impact matrix multiplication applied in classification (MICMAC) tool analysis of soil liquefaction factors. The findings of this research demonstrate that the quality and safety of food are important factors and have a direct effect on other factors. To make sustainable food supply chain management more adequate, legislators, managers, and experts need to pay attention to this factor. In this work. It also shows that companies aiming to create a sustainable business model must make sustainability a fundamental tenet of their organization. Practitioners and managers may devise effective long-term plans for establishing a sustainable food supply chain utilizing the recommended methodology.