Effect of Manufacturing Errors on Static Characteristics of Externally Pressurized Spherical Air Bearings

Externally pressurized spherical air bearings are the key component of the three-axis air bearing table, and the manufacturing errors of the bearing affects the performance of the air bearing table. However, the manufacturing errors are unavoidable, and the pursuit to enhance the manufacturing accuracy will increase the cost greatly. In order to provide some theoretical guideline for the tolerance choice in the design of the externally pressurized spherical air bearings with inherent compensation, the effects of several manufacturing errors on the static characteristics of the air bearing are studied. Due to the complex geometry of the computational domain, an unstructured meshing technology is used for mesh generation. A finite-volume method is adopted to discretize the three-dimensional steady-state compressible Navier-Stokes equations. A modified SIMPLE algorithm which is suitable for compressible flows is applied to solve the discretized governing equations. The effects of the dimension error and the roundness error of the ball head and the ball socket on the static characteristics are investigated. The investigation result shows that the positive dimension error and the oblate spheroid-type roundness error of the ball head as well as the negative dimension error and the prolate spheroid-type roundness error of the ball socket can improve the bearing capacity and static stiffness of the air bearings by reducing the mass flow. The calculation method proposed in this paper fits well for the general principle, which can be extended to the characteristics analysis of other air bearings.

China’s Agricultural Support Capacity and Dependence on Foreign Resources

To more accurately answer the questions “who will feed China?” and “whether Chinese people can feed themselves?”, we proposed a concept of agricultural support capacity, defined as the population that can be fed by energy, protein and fat from food, respectively, according to nutritional intake standards. In this study, we established models to measure this, based on analysis of China’s agricultural support capacity and how this changes under self-sufficiency and open conditions, in addition to the degrees of external dependence. Our results show that, since 2007, even without foreign resources, the energy, protein, superior protein and fat obtained from domestic agriculture had been able to feed the Chinese. However, the use of foreign resources increased and strengthened China’s agricultural support capacity, in addition to improving food diversity, optimizing nutrition, assisting in the regulation of food surplus and deficiency, and providing feed for the animal breeding industry. For the past decade, China’s degree of external dependence on energy from cereals has been relatively low, however, the degrees external dependence on superior protein and fat has increased steadily at a certain rate and have been over the national food security warning level. Therefore, China still has great demand for agricultural products from other regions of the world.

Mechanical Properties of Moso Bamboo Connections with External Clamp Steel Plates

The Moso bamboo,a renewable green building material used in various new green buildings,have received exten-sive attention with the promotion of the concept of green buildings.To explore the mechanical properties of Moso bamboo connections with external clamp steel plates,the 16 specimens were designed by changing the bolt diameters and the end distances of the bolt holes.Their static tension tests were conducted to investigate bearing capacities and failure modes of different connection configurations.Based on test results,three failure modes of these connections were obtained,including the shear failure of bolt shank,bearing failure of bolt hole and punch-ing shear failure of the Moso bamboo.The influence of bolt diameters and end distances of bolt holes on bearing capacities of the connections was quantitatively analyzed.Based on a simplified mechanical model,the analytical models were deduced for the bolt shear failure and the bearing failure of bolt holes.The results showed that the predictive values are in substantial agreement with the experimental results.Finally,the design and manufacturing suggestions are recommended for this Moso bamboo connections.

Factors of Pumping Capacity in Some Different Types of Channel Brownian Pumps

The motion of particles in different channel Brownian pumps can be described by Langevin equations,and the pumping capacity is a useful indicator to demonstrate the strength of a pump’s transportation ability.Via the simulation,there is always an optimal value of temperature and unbiased external force for different pumps which make the concentration ratio between the right tube and left tube derive its maximum and minimum in two asymmetric tubes respectively.Besides,the concentration ratio will keep 1 regardless of radius,temperature or magnitude of force in the tube in a symmetric tube.To obtain more information about pumping capacity,exploring the average probability current(APC) of tubes in different conditions is necessary.Results indicate that as the concentration ratio is 1,the change of the APC when x_(0)=0 is similar to that when x_(0)=π.Also,when the concentration ratio is more than 1,there are optimal values of temperature,radius and magnitude of force where the APC gains a maximum,and the maximum decreases as the concentration in the right tube increases when x_(0)=0.

The Research of Affecting Factors of absorption capacity in ERP implementation

a firm＇ s absorption capacity is a key factor to affect the knowledge transfer in ERP implementation, which influences the implementation of ERP By involving the subject - the ERP implementation of enterprise, ERP implementation is mainly the knowledge absorption of enterprise from the implementation service provider. It analyzes the factors that influence the absorption capacity in the implementation of Deluding the characteristics of the internal and external and knowledge itself, which promote the successful implementation of ERP.

Export fluctuation and overcapacity in China’s manufacturing industry--The inspection of the causes of excess capacity from the perspective of external demand

Intuitively speaking,there is an inverse proportional relationship between exports and overcapacity,which means in export’s busy season enterprises would expand output and improve capacity utilisation rate but control yields to avoid dull sale in slack season,causing exacerbated excess capacity.However,this is just the reflections of“sales effect”on overcapacity by export fluctuation.For some enterprises,there is indeed“competition effect”which may alleviate overcapacity because enterprises face even more fierce domestic competition for the sake of weak exports and may increase the utilisation load of existing capacity in order to cut costs.A test is conducted in this paper to verify the relationship between export fluctuation and excess capacity based on data of China's manufacturing industry from 2001 to 2013.The overall results indicate that export fluctuation is not the significant cause for excess capacity.In the small and medium-sized enterprises or in industries with higher proportion of non-state capital,the negative relationship between exports and excess capacity is more obvious,with“sales effect”taking a dominant position.On the other hand,under the influence of“competition effect”,the relationship between the two may be positive.Thus,external demand shocks exert different influence on the alleviation of excess capacity of different industries,and extensively driven exports may not have anticipated effect on the dissolution of the excess capacity.To regulate overcapacity with the aid of external market,a fair and orderly competition environment should be provided to the export subjects of different size and ownerships.

基于自产热和外传热的锂离子电池热学模型参数辨识方法

锂离子电池热学模型参数(热容和热阻)的准确辨识对电池热电耦合建模及状态参数估计至关重要。然而传统测量方法成本高且测试周期长,如何利用充放电工况结合产热和传热机理研究快速热参数辨识方法具有重要意义。以8A×h软包锂离子电池为研究对象,建立分布式热路模型;设计双向脉冲工况实验,采用自适应粒子群算法(APSO)进行辨识;同时采用其他工况进行验证,实验和仿真温度误差小于0.1℃。另外,将热容和热阻转换为比热容和导热系数,并与其他文献中同类电池的参数进行比对,量级接近。研究结果表明,该方法可以有效解决层叠式软包锂离子电池热学模型参数辨识难的问题,且简便易行、成本低。

产能分享平台企业的盈利模式选择与定价研究

在分享经济背景下,考虑交叉网络外部性效用及平台匹配率,研究产能分享平台的盈利模式选择与定价问题。基于两阶段博弈方法,分析并比较了平台在利润最大化和社会福利最大化条件下选择服务费模式与注册费模式时获得的最大利润。研究发现,在目标时间段内,当平台以利润最大化为目标时,多数情况下选择注册费模式获得的最大利润高于选择服务费模式获得的利润。在特定条件下,也存在平台采取两种盈利模式会获得相同利润的情况。此外,平台最大利润在一定条件下与交叉网络外部性系数和平台对制造能力供应方的匹配率正相关,与对制造能力需求方的匹配率负相关。当平台以社会福利最大化为目标时,选择服务费模式获得的利润高于选择注册费模式时的利润。最后,通过数值算例对上述结果进行了验证。

面向质量和交货期的产能分享平台审核策略研究

通过构建双边市场模型探索产能分享平台的审核策略。研究表明:当产能需求方仅对质量敏感,排除低质量产能供应方比仅根据质量对产能供应方分级更利于平台盈利;当产能需求方对质量和交货期均敏感,设置两个维度的审核门槛能使平台获得更高利润;平台利润与双边用户交叉网络外部性、产能需求方对质量的敏感性正相关,与产能需求方对交货期的敏感性负相关;质量和交货期审核门槛受产能需求方对这两个维度的敏感性、双边用户网络外部性、平台审核成本系数相互作用影响。

岩棉复合保温外模板承载力及温度效应分析

为了提高建筑外围护结构施工效率及解决传统外保温系统长期存在的易脱落和易着火问题,提出了一种集保温和建筑模板于一体的岩棉复合保温外模板(RW-CIEF)体系。RW-CIEF由内到外依次为内侧加强层、岩棉保温芯材、黏结层、保温过渡层以及外侧加强层。以哈尔滨市为例,基于全寿命周期成本(life cycle cost,C lc)确定了岩棉保温芯材的最佳厚度。采用有限元分析与理论计算相结合的方法探求了RW-CIEF在工程中的可行性,分析了RW-CIEF的抗弯性能、施工承载力及温度效应下的应力和变形,讨论了开槽形式、开槽宽度、开槽深度以及开槽间距对RW-CIEF抗弯性能的影响。结果表明:RW-CIEF的抗弯性能理论计算结果与有限元分析结果有较高的一致性;开槽处理可有效提高RW-CIEF的抗弯性能,综合抗弯性能、热工特性及加工角度,建议开槽形式选用对应开井字槽或对应开纵槽,开槽深度和宽度均为10 mm,开槽间距为150 mm;设计的RW-CIEF满足施工承载力,可保证外围护结构保温工程施工质量;由温度效应产生的最大拉应力和压应力均未超过RW-CIEF的外侧加强层承载力,反映出RW-CIEF出现夏季空鼓或冬季开裂现象的可能性极小。提出的RW-CIEF体系可为外围护结构保温工程及建筑模板工程未来研究方向提供一种新的思路和方法。

体外预应力UHPC无腹筋梁抗剪性能试验研究

为研究体外预应力超高性能混凝土(Ultra-high Performance Concrete,UHPC)无腹筋梁的抗剪性能,设计了3片体外预应力UHPC无腹筋梁,剪跨比分别为1.44、2.56、3.67,采用四点加载的方式进行抗剪性能试验,获得了试验梁的荷载-位移关系、荷载-应变关系、破坏形态以及极限抗剪承载力。试验结果表明:体外预应力UHPC无腹筋梁的抗剪破坏方式均表现为脆性破坏,随着剪跨比的增大,试验梁破坏形态依次表现为斜压破坏、剪压破坏、剪拉破坏;剪跨比越大,斜裂缝的数量越少、倾角越小,试验梁的极限抗剪承载力越小,且减小趋势变缓。基于极限平衡法推导了体外预应力UHPC无腹筋梁的抗剪承载力计算公式,验算了14片无黏结预应力UHPC梁的抗剪承载力,该公式适用性良好。

预应力混凝土拱板屋架检测鉴定与加固

预应力混凝土拱板屋架结构在我国粮食仓储领域扮演着举足轻重的角色,作为主要的粮仓顶部结构形式,对其检测鉴定进行研究具有重要的实际指导意义。从我国研究现状来看,大多数研究都聚焦于施工工艺和施工设计,在检测鉴定及加固技术方面的探讨相对较少。选取罗山国家粮食储备库的预应力混凝土拱板屋架作为研究对象,从工程检测、承载力验算、数值模拟及加固设计等多个环节开展研究,最后,针对不符合承载力要求的下弦板,提出体外预应力加固的设计方案。这一系列研究成果不仅对预应力拱板的检测鉴定提供科学可靠的理论基础及参数化模型,也为同类工程的加固设计提供新的借鉴。

基于“等级-网络”双维度下的福建省县级单元对外服务能力空间格局演化

基于城市流强度模型和改进的引力模型,从“等级-网络”双维度下的对外服务能力空间关系,开展福建省县级单元对外服务能力格局演变的分析。结果表明:(1)第二、三产业对外服务能力均持续增强的同时,工业与商务商贸成为职能部门的“双子星”。(2)对外服务能力空间格局整体表现出沿海高于内陆的特征,各职能分工定位与发展态势逐步明晰。(3)对外服务能力网络格局中第二、三产业勾勒出以沿海高等级联系为主导并向内陆辐射延展的放射状网络;工业职能部门在内陆与沿海分别形成倒“T”型与“钻石型”主干网络。

高速铁路隧道接触网外置槽道整治方案及受力分析

为解决高速铁路隧道接触网下锚处预埋槽道质量缺陷,以湖杭高速铁路(湖州—杭州西)工程为依托,提出外置槽道整治方案。利用有限元软件建立外置槽道数值模型,分析外置槽道和后置锚栓的受力和变形。结果表明:在规定荷载作用下,外置槽道最大应力为104.1 MPa,最大变形为0.032 mm;后置锚栓最大轴力和剪力分别为9.65、1.08 kN;外置槽道和后置锚栓的受力、变形均满足规范要求。将外置槽道方案应用于湖杭高速铁路槽道缺陷整治工程,实施效果良好,可在其他铁路隧道接触网预埋槽道缺陷整治工程中推广应用。

钢桁腹-混凝土组合箱梁局部外接节点静载试验及极限承载力计算研究

为了解钢桁腹-混凝土组合箱梁(顶、底板为混凝土结构,腹杆为钢结构)外接节点在水平荷载作用下的受力性能,以某钢桁腹-混凝土组合箱梁桥方案为背景,选取钢腹杆轴力最大节点设计、制作缩尺比为1∶3的钢桁腹-混凝土组合箱梁局部外接节点试件(由混凝土弦杆、方形钢腹杆、节点板组成,原混凝土板简化为混凝土弦杆)并开展静载试验,分析外接节点试件静载试验现象及破坏模式、荷载~位移曲线,以及混凝土弦杆、节点板和钢腹杆的应力分布规律,并基于有效宽度法及撕裂面法与最大强度准则提出外接节点极限承载力计算方法。结果表明:外接节点试件的破坏模式为节点板拉剪断裂失效,极限承载力为设计荷载的5.71倍,承载能力满足要求;混凝土弦杆压应力沿加载方向逐渐减小,沿竖直方向从上往下逐渐增大;节点板应力沿加载方向总体上先增后减,外露节点板是节点受力的关键构件;外接节点极限承载力由节点板和钢腹杆中较弱者控制,采用所提出的计算方法得到的外接节点极限承载力计算值与试验结果相差小于6%。

多轮次蒸汽吞吐水平井套管射孔参数优选方法研究

针对多轮次蒸汽吞吐水平井在确保套管安全寿命前提下,有利实现储层产能最大化释放的套管射孔参数优选问题,开展了射孔参数对产能影响和对套管安全性影响研究,建立了水平套管井表皮因子计算模型及产能预测模型。在此基础上提出了在满足储层产能最大化释放的射孔参数范围内,结合套管安全性校核结果优选射孔参数的方法。通过该方法设计的渤海某稠油油田的射孔参数可知,该井目前已完成超3轮次蒸汽吞吐过程,产能达到配产的同时,套管处于安全服役的状态。该方法可为多轮次蒸汽吞吐水平井套管射孔参数优选提供依据。

不同植被下土壤有机质含量的测定

土壤有机质(soil organic matter,SOM)是一项评判土壤质量状况的重要因子,其含量的高低对农业生产活动具有重要作用。本文采集了江南地区三种不同植被下的土壤样品,在实验室使用重铬酸钾外加热容量法测定土壤有机质含量。结果发现,原始树林土壤有机质含量为11.6 g/kg,茶田为19.2 g/kg,竹林为36.8 g/kg。

厦门市自动体外除颤器空间配置、覆盖能力及可达性分析

基于核密度、缓冲区地理空间分析方法和高斯两步移动搜索模型,结合厦门市人口分布、兴趣点以及地理信息数据,探究厦门市自动体外除颤器的空间配置、覆盖能力和可达性。结果表明:厦门市自动体外除颤器呈现出多级中心-圈层状空间分布形态,中心城区与起步发展区间的设施密度存在明显差异,空间分布不均衡;厦门市自动体外除颤器分布场所类型广,整体空间覆盖能力较好,可达性水平和人口密度之间存在负相关现象,约65.39%的统计区域为可达性盲区。建议厦门市对自动体外除颤器的配置实施因地制宜分区施策、因时制宜适度超前、以风险评估为导向的优化策略,进一步提升其覆盖能力和可达性。

外部搜寻、关系强度与吸收能力对新产品开发绩效的影响

从知识基础观出发,研究外部搜寻宽度和深度对新产品开发绩效的影响,并引入关系强度和吸收能力作为情境变量。通过281家中国企业样本问卷调查,发现搜寻宽度有利于新产品创新性的提升,而搜寻深度有利于新产品开发速度的提升。关系强度负向调节搜寻宽度与新产品创新性的关系,而正向调节搜寻深度与开发速度的关系。另外,关系强度和吸收能力有协同调节作用,二者的协同作用负向调节搜寻宽度与新产品创新性的关系,而正向调节搜寻深度与开发速度的关系。

中国式现代化进程中的外交机制能力建设

外交能力现代化是中国式现代化的重要组成部分,也是影响统筹“两个大局”的重要因素。在外交能力的诸多要素中,外交机制能力极为重要,是外交能力建设的制度性保障。完善对外工作体制机制,需要加强外交机制能力建设。这也是促进外交能力现代化,增强海外利益维护,体现中国大国担当等的必由之路。新时代以来,中国通过加强对外工作顶层设计、推动涉外机构改革、完善外交法规和提升国际制度性权力,持续提升了外交机制能力。面对实现中华民族伟大复兴和构建人类命运共同体的重要任务,需持续加强中国外交机制能力,完善外交协调机制、促进外交法规的国际接轨、优化外交机制的科技赋能和增强国际制度性权力。