Recent advances in cobalt phosphide-based materials for electrocatalytic water splitting:From catalytic mechanism and synthesis method to optimization design

Electrochemical water splitting has long been considered an effective energy conversion technology for trans-ferring intermittent renewable electricity into hydrogen fuel,and the exploration of cost-effective and high-performance electrocatalysts is crucial in making electrolyzed water technology commercially viable.Cobalt phosphide(Co-P)has emerged as a catalyst of high potential owing to its high catalytic activity and durability in water splitting.This paper systematically reviews the latest advances in the development of Co-P-based materials for use in water splitting.The essential effects of P in enhancing the catalytic performance of the hydrogen evolution reaction and oxygen evolution reaction are first outlined.Then,versatile synthesis techniques for Co-P electrocatalysts are summarized,followed by advanced strategies to enhance the electrocatalytic performance of Co-P materials,including heteroatom doping,composite construction,integration with well-conductive sub-strates,and structure control from the viewpoint of experiment.Along with these optimization strategies,the understanding of the inherent mechanism of enhanced catalytic performance is also discussed.Finally,some existing challenges in the development of highly active and stable Co-P-based materials are clarified,and pro-spective directions for prompting the wide commercialization of water electrolysis technology are proposed.

Study on trifluoromethanesulfonic acid-promoted synthesis of daidzein: Process optimization and reaction mechanism

Daidzein has been widely used in pharmaceuticals,nutraceuticals,cosmetics,feed additives,etc.Its preparation process and related reaction mechanism need to be further investigated.A cost-effective process for synthesizing daidzein was developed in this work.In this article,a two-step synthesis of daidzein(Friedel–Crafts acylation and[5+1]cyclization)was developed via the employment of trifluoromethanesulfonic acid(TfOH)as an effective promoting reagent.The effect of reaction conditions such as solvent,the amount of TfOH,reaction temperature,and reactant ratio on the conversion rate and the yield of the reaction,respectively,was systematically investigated,and daidzein was obtained in 74.0%isolated yield under optimal conditions.Due to the facilitating effect of TfOH,the Friedel–Crafts acylation was completed within 10 min at 90℃ and the[5+1]cyclization was completed within 180 min at 25℃.In addition,a possible reaction mechanism for this process was proposed.The results of the study may provide useful guidance for industrial production of daidzein on a large scale.

Configuration Synthesis and Lightweight Networking of Deployable Mechanism Based on a Novel Pyramid Module

Deployable mechanism with preferable deployable performance,strong expansibility,and lightweight has attracted much attention because of their potential in aerospace.A basic deployable pyramid unit with good deployability and expandability is proposed to construct a sizeable deployable mechanism.Firstly,the basic unit folding principle and expansion method is proposed.The configuration synthesis method of adding constraint chains of spatial closed-loop mechanism is used to synthesize the basic unit.Then,the degree of freedom of the basic unit is analyzed using the screw theory and the link dismantling method.Next,the three-dimensional models of the pyramid unit,expansion unit,and array unit are established,and the folding motion simulation analysis is carried out.Based on the number of components,weight reduction rate,and deployable rate,the performance characteristics of the three types of mechanisms are described in detail.Finally,prototypes of the pyramid unit,combination unit,and expansion unit are developed to verify further the correctness of the configuration synthesis based on the pyramid.The proposed deployable mechanism provides aference for the design and application of antennas with a large aperture,high deployable rate,and lightweight.It has a good application prospect in the aerospace field.

Computer Aided Design and Performance Analysis of Inverse Fluidized Bed Biofilm Reactors with Special Reference to Bioplastic Synthesis

Poly Laevo Lactic Acid (PLLA), in spite of being an excellent bioplastic, has exorbitantly high market price due to the high cost of raw material (lactose, glucose, sucrose). Hence, its manufacture is being attempted starting from waste effluents such as cheese whey and molasses. Earlier studies on the same in fluidized bed and semifluidized bed biofilm reactors yielded encouraging results. The present study therefore involves design and analysis of inverse fluidized bed biofilm reactors for lactic acid synthesis. The performance features of the bioreactor have been studied both mathematically as well as experimentally. The inverse fluidized bed biofilm reactor has been found to provide more than 75% conversion of sucrose/lactose even at high capacities (high feed flow rates) exceeding 56,000 L/hr, within a reasonably low reactor volume. The fractional substrate conversion increases, though sluggishly, with increase in feed flow rate due to bed expansion and also with increase in cell mass concentration in biofilm due to enhancement in intrinsic rate of bioconversion. The inverse fluidized bed biofilm reactor of proposed design could be safely recommended for the commercial synthesis of polymer grade lactic acid from waste effluents such as cheese whey and molasses. The low operating cost of the bioreactor (due to downflow mode of operation) enhances the economy of the process. This would also help in significantly lowering the market price of the green plastic (PLLA) and shall promote its large scale manufacture and utilisation.

Type Synthesis of Lower Mobility Parallel Mechanisms: A Review

Type synthesis of mechanisms aims to systematically determine all possible structures for a specific mobility requirement. Numerous methods based on di erent theories were proposed for type synthesis of lower mobility parallel mechanisms in past decades. However, there does not exist a comprehensive review on these approaches. Therefore, the goal of this paper is to give such a review, classifying the approaches proposed in the literature into three groups, namely, motion-based methods, constraint-based methods, and other methods. The motion-based methods include the Lie group based method, the GF set method, the linear transformation method, the POC set method,and the finite screw method. The constraint-based methods involve the screw theory-based method, the virtual chain method, the method based on Grassmann line geometry and line graphs, and the motion constraint generator method. Other methods contain the enumeration approach based on the general CGK mobility formula and the graph theory method. Upon thoroughly analyzing the characteristics and/or limitations of each method, this review provides a well reference to help researchers find an e ective synthesis method for innovative design and further scientific investigations for mechanisms.

Designing the Instrument Crank-Coupler Mechanism of Linear Output with Least Transmission Ratio Error

Movement accuracy is the key factor to be considered in designing precision instrument linkage and mini-linkage mechanisms. Although manufacturing errors, elastic deformation, kinematic pair clearance and friction factors all will have synthesis effect on the position accuracy of the mechanical system, the essential factor to guarantee the movement precision remains the kinematic dimensions. Combining the classical theory of mechanical synthesis with the modern error theory and the numerical method, the authors put forward a systematic and complete process and method of computer aided design for the instrument crank-coupler mechanism in which the follower takes the linear displacement approximately within a certain limited domain, with the design result of least transmission ratio error.

THE APPLICATION OF THE COMPUTER AIDED ANALYSIS IN THE DESIGN OF COALMINE MACHINERY LINKAGES

This paper gives and verifies a mathematical model with only one argument which determines the movement parameters of any point in a plane four-bar linkage on the basis of the analysis of mining machinery linkages. C A A (computer aided analysis) based on the mathemetical model can be used to make not only the quick and accurate analysis and design of mining machinery linkages but also the movement analysis and optimization design of any other plane four-bar linkage.

Workshop Oriented Tolerance Synthesis for Spatial PKM

To promote the pose accuracy performance of a spatial parallel kinematic Mechanism( PKM) in service,a workshop oriented tolerance synthesis method based on design of experiment( DOE) is proposed,which involves two consecutive stages. In the first stage of DOE,the tolerance factor sensitivities are obtained according to initial tolerance settings with the consideration of the current manufacturing capacity,and the second stage of DOE makes use of them to produce multiple tolerance allocations which can adapt to current manufacturing capacity. A tolerance synthesis procedure is developed and integrated in tolerance design system for PKM. Comparing the results with peer method,the validity and practicability of this method is verified.

Study of Piezoresistive Micro Electro-Mechanical Accelerometer Design Platform

According to the inland micro electro-mechanical system （MEMS） process technique level, a design platform of piezoresistive micro electro-mechanical accelerometer is given. This platform is much more adaptable to the inland designer compared with the current MEMS CAD software. The design flow is presented in detail, and the key techique in the platform is analyzed amply. The structure design methodology is exemplified in the design of a piezoresistive accelerometer, and the accelerometer is the optimized structure for the given performance requirements. The accelerometer is now being manufactured.

Solidworks应用于《机械设计课程设计》课程教学

在《机械设计课程设计》课程教学中引入计算机辅助设计软件Solidworks作为辅助教学手段,通过该软件特有的运动仿真功能,建立闭式齿轮传动、锥齿轮传动、开式齿轮传动、链轮绞盘机构的虚拟模型,装配各传动机构,检查、优化设计方案,实现了传动装置的运动仿真,完成了该锚机系缆装置的模拟设计,锻炼了学生的软件使用技能,增强了学生对理论知识的深入理解和应用,激发了学生对机械课程深入学习的兴趣,提高了学生的机械设计水平,同时有助于培养学生工程实践和综合应用能力,达到了预期的教学效果。

数字化技术在机械制造中的应用

随着数字化技术的不断发展,传统的机械制造方式正在迎来革命性的变革,计算机辅助设计(CAD)、计算机辅助制造(CAM)、计算机辅助工程(CAE)等为机械制造行业带来了巨大的变革,推动了制造业向智能、高效、可持续的方向发展。该文以机械制造过程中的数字化生产线、精密制造技术及数字化机床仿真技术为案例,深入探讨了数字化技术在机械制造中的应用,重点分析数字化生产线的建设及精密制造技术在数字化时代的发展趋势,最后聚焦于数字化机床仿真技术的研究。数字化技术为精密制造提供了更精准的工艺控制和质量监测手段,通过数字化仿真,制造企业可以在实际生产之前对机床性能进行精准评估,提高了设备的利用率和产品质量,为制造过程的优化提供了有力支持。

Design of a novel side-mounted leg mechanism with high flexibility for a multi-mission quadruped earth rover BJTUBOT

Earth rover is a class of emerging wheeled-leg robots for nature exploration.At present,few methods for these robots’leg design utilize a side-mounted spatial parallel mechanism.Thus,this paper presents a complete design process of a novel 5-degree-of-freedom(5-DOF)hybrid leg mechanism for our quadruped earth rover BJTUBOT.First,a general approach is proposed for constructing the novel leg mechanism.Subsequently,by evaluating the basic locomotion task(LT)of the rover based on screw theory,we determine the desired motion characteristic of the sidemounted leg and carry out its two feasible configurations.With regard to the synthesis method of the parallel mechanism,a family of concise hybrid leg mechanisms using the 6-DOF limbs and an L1F1C limb(which can provide a constraint force and a couple)is designed.In verifying the motion characteristics of this kind of leg,we select a typical(3-UPRU&RRRR)&R mechanism and then analyze its kinematic model,singularities,velocity mapping,workspace,dexterity,statics,and kinetostatic performance.Furthermore,the virtual quadruped rover equipped with this innovative leg mechanism is built.Various basic and specific LTs of the rover are demonstrated by simulation,which indicates that the flexibility of the legs can help the rover achieve multitasking.

口腔种植修复中钛基底氧化锆基台的制作和力学性能

背景:随着计算机辅助设计和计算机辅助制造技术的发展,钛基底氧化锆基台因具备良好的应用优势被广泛运用于临床,但仍存在一些问题,尚缺乏共识性的设计标准。目的:综述钛基底氧化锆基台的制作方法及基台连接、穿龈设计、基台角度和粘接对钛基底氧化锆基台各类力学性能的影响。方法:检索Pub Med数据库和中国知网2010-2023年发表的相关文献,检索词为“zirconia abutment,titanium base;氧化锆基台,钛基底”,部分经典文献延长检索时间限制,通过纳入和排除标准获取相关文献,对57篇符合标准的文献进行综述。结果与结论:建议临床医生尽量选择具有抗旋结构的基台连接或是具有莫氏锥度的非抗旋连接,当运用钛基底氧化锆基台时,种植体应放置在正确的轴向角度(植体轴向向唇侧倾斜角度不超过15°或略向腭侧倾斜);当植体轴向向唇侧倾斜角度≥30°时,应当适当降低咬合力,以降低种植体、基台及修复体机械并发症和生物并发症的风险;应尽可能选择穿龈高度较高的钛基底,并且其穿龈角度不应超过40°。Multilink Hybrid Abutment可以作为氧化锆基台与钛基底口外粘结的首选粘接剂。

机械设计课程传动组合教具的创新设计

机械设计课程包含多种机械结构,若只是依靠以往的教学方式,往往很难使学生系统化掌握专业知识,而且机械设计课程所编写的有关机械传动内容,大多是从工作原理、传动结构特性,到强度计算、教具应用和维护的编写顺序,尤其是强度计算内含大量复杂公式与参数,还有各种表格与图形,具有较大的学习难度。组合传动机构的创新设计,能够系统巧妙地结合零散的机械设计教具,与机械设计课程理论、实践学习要求相符合,而且可以将学生对机械设计课程学习的热情全面激发出来,有助于提高学生的机械创造力。

The design and synthesis of Prussian blue analogs as a sustainable cathode for sodium-ion batteries

Sodium-ion batteries(SIBs)present great appeal in various energy storage systems,especifically for stationary grid storage,on account of the abundance of sources and low cost.Unfortunately,the commercialization of SIBs is mainly limited by available electrode materials,especially for the cathodes.Prussian blue analogs(PBAs),emerge as a promising alternative for their structural feasibility in the application of SIBs.Decreasing the defects(vacancies and coordinated water)is an effective strategy to achieve superior electrochemical performance during the synthetic processes.Herein,we summarize crystal structures,synthetic methods,electrochemical mechanisms,and the influences of synthesis conditions of PBAs in detail.This comprehensive overview on the current research progresses of PBAs will give guides and directions to solve the existing problems for their application in SIBs.

机械零部件的测绘和CAD制图技术

随着现代工业的不断发展,机械零部件的测绘及计算机辅助设计(Computer Aided Design,CAD)制图研究成为工程设计中不可或缺的一环。以机械零部件测绘概述为基础,分析机械零部件测绘流程,详细讨论CAD制图技术在机械零部件测绘中的应用。经过实践证明,机械零部件测绘准确性对于工程设计的成功至关重要,而CAD制图技术应用则能大幅度提高测绘效率。

基于近似综合法的空间刚体导引机构尺度综合

目前空间连杆机构尺度综合是机构综合研究的难点问题之一。首先,通过分析空间RCCC刚体导引机构输出的数学模型,提出了空间刚体导引机构综合的分步式降维综合方法;然后,将21维的机构设计问题分4步进行求解,降低了优化变量维度,推导出了机构实际尺寸的计算公式;最后,通过实际算例证明了所提方法的有效性。所研究结果为非整周期设计要求的空间RCCC机构刚体导引综合问题的求解提供了一种可行的方法。

Innovative Group-Decoupling Design of a Segment Erector Based on G_F Set Theory

The segment erector is a key part of the shield machines for tunnel engineering. The available segment erectors are all of serial configuration which is suffering from the problems of low rigidity and accumulative motion errors. The current research mainly focuses on improving assembly accuracy and control performance of serial segment erectors. An innovative design method is proposed featuring motion group-decoupling, based on which a new type of segment erector is developed and investigated. Firstly, the segment installation manipulation is analyzed and decomposed into three motion groups that are decoupled. Then the type synthesis for the 4-DOF motion group is performed based on the general function（GF） set theory and a new configuration of （1T？1R？1PS3UPS） is attained according to the segment manipulation requirements. Consequently, the kinematic models are built and the reducibility and accuracy are analyzed. The dexterity is verified though numerical simulation and no singular points appear in the workspace. Finally, a positioning experiment is carried out by using the prototype developed in the lab that demonstrates a 13.1% improvement of positioning accuracy and the feasibility of the new segment erector. The presented group-decoupling design method is able to invent new type of hybrid segment erectors that avoid the accumulative motion error of erecting.

瞬心无穷远近似直线导向机构综合及解域寻优方法

对连杆平面瞬心趋向无穷远的一类平面四杆直线导向机构,在给定理想直线点位与机架一定铰点位置的设计条件下,提出一套通用机构综合模型。推导了机构综合解析求解公式,给出了机构综合及寻优方法示例。该方法可综合得到无穷多满足理想直线点位要求的直线机构,并可根据设计需求施加运动学约束,计算可行机构解域,绘制解域上感兴趣的运动性能分布图;设计者可准确快捷地从无穷多设计方案中找出满足约束的全局最优直线机构。综合示例表明,所提方法为瞬心无穷远直线机构综合这一类问题提供了新的解决思路;综合过程简单直观、通用性强,适用于瞬心无穷远具有2阶、3阶密切直线机构的计算机辅助设计,有利于这类机构设计质量的提升并有效压缩设计周期。

“土力学课程设计”任务书生成辅助软件研制与应用体会

“土力学课程设计”属于实践环节内容,是培养学生综合运用专业知识、工程实践能力和创造精神的关键环节。文章分析了传统“土力学课程设计”开展过程中遇到的一系列问题以及所开发的“土力学课程设计”任务书生成辅助软件。利用该软件,可以很方便地创建、管理和重复利用课程设计的基础数据信息,可以选择课程设计主题、设计任务、工程场地条件与建筑物规模,自主组合课程设计任务,满足不同基础、不同学习兴趣与钻研深度的学生进行课程设计的需求。利用该软件,可以快速生成与导出“土力学课程设计”任务书,并避免数据与任务不匹配等错误的发生,方便实现学生一人一题,从而解决传统课程设计的弊端,具有推广价值。