An evaluation of force-based design vs.direct displacement-based design of jointed precast post-tensioned wall systems

The unique features of jointed post-tensioned wall systems, which include minimum structural damage and re-centering capability when subjected to earthquake lateral loads, are the result of using unbonded post-tensioning to attach the walls to the foundation, along with employing energy dissipating shear connectors between the walls. Using acceptance criteria defined in terms of inter-story drift, residual drift, and floor acceleration, this study presents a multiplelevel performance-based seismic evaluation of two five-story unbonded post-tensioned jointed precast wall systems. The design and analysis of these two wall systems, established as the direct displacement-based and force-based solutions for a prototype building used in the PREcast Seismic Structural Systems （PRESSS） program, were performed at 60% scale so that the analysis model could be validated using the PRESSS test data. Both buildings satisfied the performance criteria at four levels of earthquake motions although the design base shear of the direct displacement-based jointed wall system was 50% of that demanded by the force-based design method. The study also investigated the feasibility of controlling the maximum transient inter-story drift in a jointed wall system by increasing the number of energy dissipating shear connectors between the walls but without significantly affecting its re-centering capability.

Dynamic Event-Triggered Consensus Control for Input Constrained Multi-Agent Systems With a Designable Minimum Inter-Event Time

This paper investigates the consensus control of multi-agent systems(MASs) with constrained input using the dynamic event-triggered mechanism(ETM).Consider the MASs with small-scale networks where a centralized dynamic ETM with global information of the MASs is first designed.Then,a distributed dynamic ETM which only uses local information is developed for the MASs with large-scale networks.It is shown that the semi-global consensus of the MASs can be achieved by the designed bounded control protocol where the Zeno phenomenon is eliminated by a designable minimum inter-event time.In addition,it is easier to find a trade-off between the convergence rate and the minimum inter-event time by an adjustable parameter.Furthermore,the results are extended to regional consensus of the MASs with the bounded control protocol.Numerical simulations show the effectiveness of the proposed approach.

基于Geomagic Design Direct的残缺数据实体重构

面向实物的逆向工程技术是近几年来研究和发展的热点,已广泛应用于产品设计、文物保护和零件修复等领域。报告了对模型的残缺表面数据进行曲面和实体重构的研究现状,以及结合正向和逆向建模软件进行实体模型重构的局限性。介绍了应用软件Geomagic Design Direct进行实体模型重构的优势以及对残缺表面数据实体模型重构的一般流程。提出了基于软件Geomagic Design Direct的特征识别与提取功能,对残缺表面数据进行实体重构的解决方案,并以某一零部件的残缺表面数据为例进行实体重构验证了该方案的可行性和便利性。

基于Geomagic Design Direct的截面特征提取与逆向建模

当前逆向工程已成为一种消化、吸收先进技术,实现产品的创新设计和快速开发的重要技术手段。随着各种特征技术的不断发展和引进,基于特征的逆向建模方法逐渐成为逆向工程新的发展方向。根据已有的建模方法,提出一种在二维草图模式下截面特征轮廓线提取与参数化设计的逆向建模新思路。并以Geomagic Design Direct软件为平台,实现了二维草图模式下特征轮廓线的提取与参数化再设计的逆向建模方法,为产品的快速建模和创新设计提供了一种新的途径。

DIRECT DIGITAL DESIGN AND SIMULATION OF MESHING IN WORM-GEAR DRIVE

A direct digital design method （DDDM） of worm-gear drive is proposed. It is directly based on the simulation of manufacturing process and completely different from the conventional modeling method. The loaded tooth contact analysis （LTCA） method is analyzed, in which the advanced surface to surface searching technique is included. The influence of misalignment errors and contact deformations on contact zone and transmission error （TE） is discussed. Combined modification approach on worm tooth surface is presented. By means of DDDM and LTCA, it is very conven- ient to verify the effect of worm-gear drive＇s modification approach. The analysis results show that, the modification in profile direction reduces the sensitivity of worm-gear drive to misalignment errors and the modification in longitudinal direction decreases the TE. Thus the optimization design of worm-gear drive can be achieved prior to the actual manufacturing process.

A simplified design method for metallic dampers used in the transverse direction of cable-stayed bridges

The aseismic design of cable-stayed bridges in the transverse direction with newly proposed metallic dampers that can accommodate both longitudinal and transverse movement of the deck has recently been considered.This work focuses on developing a simplified method to design an appropriate metallic damper.The seismic performance of cablestayed bridges with different damper stiffness,main span lengths,tower shapes and types of deck in the transverse direction are investigated.The transverse displacement of the deck of a cable-stayed bridge increases significantly with the increment of the damper stiffness,which proves that the design of the damper stiffness is crucial.A simplified model considering the damper stiffness,cable system and tower in the transverse direction is developed to evaluate the period and lateral displacement of a complicated cable-stayed bridge.Based on the simplified model,a design method is proposed and assessed using two cable-stayed bridges as examples.The results show that metallic dampers can be designed with high efficiency,and the optimal ductility of the damper can be selected.

Optimum Design of Tilt Angle and Horizontal Direction of Solar Collectors under Obstacle’s Shadow for Building Applications

Solar collectors can provide clean, renewable, and domestic energy. The tilt angle and horizontal direction of solar collectors significantly affect its efficiency. There are many good methods to search the optimum tilt angle and horizontal direction to realize the maximum total radiation on the solar collector within a particular day or a specific period. However, it is hard to realize it when solar collectors are placed under obstacle’s shadows;especially when some obstacles, such as trees, have irregular shapes. This paper presents algorithms to achieve the best tilt angle and horizontal direction for solar collector’s performance under the free-form surfaces 3D obstacle’s shadow. The solution process is composed of 4 steps. First, it creates a 3D scene, in which a unique color is given to the solar collector. Second, it employs orthographic projection from the point of view to get an image of the scene. Third, the number of pixels is used to represent the efficiency of the solar collector by counting the pixels of the unique color. Fourth, the efficiency of solar collector in each direction in a period of time is calculated with many images to further select the best direction.

MoM Analysis and Design of a Compact Coaxial-to-Microstrip Directional Coupler

In order to overcome the main drawbacks of coaxial, waveguide, and stripline couplers, the analysis and the design of a compact coaxial-to-microstrip directional coupler convenient for power and antenna control application, are presented using the method of moments (MoM) in two dimensions. This technique is adapted to study the complex configuration of the line’s system, which does not have a simple analytical solution. The modeling of this structure consists in analyzing the primary inductive and capacitive matrices ([L] and [C]). When these matrices are determined, it is possible to calculate the inductive and capacitive coupling coefficients (kL and kC) and estimate the resulting scattering parameters of the coupler using an adapted numerical model. The coupler can be integrated into a printed circuit board (PCB) and operates over 17 to 35 dB coupling coefficients and is always compensated. The compensation is achieved by the proper displacement of a tuning ground plane with respect to the edge of the PCB from 0.1 to 3.3 mm. As an application, we present the design of a compact coupler with 7.5 × 4.8 × 25.8 mm of size and having approximately 20 dB of coupling coefficient at 2 GHz and a minimum directivity of 23.3 dB in the frequency range [0.1 - 4] GHz. In order to check our numerical calculations by the MoM we made simulations in 3D by using CST MICROWAVE STUDIO software for the same geometrical and physical parameters of our designed coupler. The results obtained by the two numerical models (MoM and CST) show a good agreement of the frequency responses of the coaxial-to-microstrip directional coupler. The studied structure represents a great improvement for high power measurement systems, since it has broad-band, good directivity, and can be easily designed and fabricated.

微小流量旋转直驱伺服阀传控特性分析与优化

针对无人机、战术弹、支线民航等小型飞行器航空发动机燃油计量系统与推力矢量系统微小流量的伺服控制需求,就旋转直驱伺服阀偏心球副传动接口与非全周节流阀口等关键结构进行了尺寸约束设计分析,并就节流阀口宽度、球副偏心距以及驱动电机转动惯量等重要参数进行了优化分析,给出了伺服阀结构设计的优化区间。在此基础上,研究提出了电机转角与电流双闭环控制方法,幅频响应实测结果与理论分析较为一致,200 Hz以上高频响应满足实际需求,且双闭环控制方法大幅降低了伺服阀响应超调并提升了稳定性。

设计教育视域下手绘研究的可视化分析

分析设计教育视域下手绘研究的发展脉络,探究设计手绘教育的发展向度。以CNKI收录的3533篇论文作为研究对象,运用Citespace信息可视化软件对研究机构、高被引文献、关键词、研究热点等方面进行深入分析研究。目前,我国关于手绘研究多集中在手绘历史沿革及发展、计算机信息技术和手绘工具3个方面。各研究机构应该提升手绘研究重视度并加强合作;同时,在研究方法上由传统的质性研究拓展至量化研究,制定量规,提供不同维度的研究数据,逐步完善手绘体系,促进手绘均衡发展。

砾砂地层盾构切削大直径群桩的刀具研究

刀盘刀具是盾构机实现切削功能并保证其顺利推进的主要部件,合适的刀具选型与设计在保证盾构机成功切削大直径钢筋混凝土群桩的过程中至关重要。依托沈阳地铁4号线盾构切桩工程,结合盾构穿越砾砂地层的工程特点以及切削大直径钢筋混凝土群桩的工程需求,对刀盘刀具进行选型,采用LS-DYNA软件模拟不同刃宽、刃角及前角的贝壳刀切削钢筋的效果。将分析结果应用于该工程,通过对比切桩前后既有隧道沉降变化规律论证刀具选型设计的合理性,并根据切桩后的贝壳刀磨损规律及盾构机排出钢筋情况,评估刀盘刀具切削效果,从而优化刀盘的刀具布置。研究结果表明:盾构刀盘采用面板+辐条复合式直角刀盘,切桩刀具采用前角-45°零后角、5 mm刃宽、90°刃角的双面刃贝壳刀,可提升盾构切桩效果;盾构切桩过程中既有隧道的变形波动控制在1.1 mm内,切桩完成后既有隧道的最大沉降仅为1.96 mm,未对既有隧道造成明显影响;刀盘布置贝壳刀时,应增加高度为210 mm的贝壳刀数量,尤其需要避免单个辐条上仅有1把高度为210 mm贝壳刀的情况,可有效提高刀盘刀具切削钢筋的能力并降低崩刃风险。刀具选型设计结果成功应用于沈阳地铁4号线切桩工程,可为今后类似工程提供参考。

极近距离煤层开采无煤柱自成巷控制方法研究

极近距离煤层传统长壁开采,受上层遗留煤柱和采空区垮落等因素的影响,下煤层开采过程中应力环境复杂、矿压显现剧烈,易诱发巷道围岩大变形。为解决上述问题,提出了极近距离条件下巷道定向切顶–约束高强支护无煤柱自成巷控制方法。通过顶板定向预裂切顶,主动改变顶板悬臂结构,切断采空区向巷道顶板的应力传递。充分利用矿山压力和岩体碎胀特性,取消煤柱留设,结合高强支护加强巷道顶板整体性,共同实现切顶自成巷。建立了极近距离煤层开采覆岩结构模型,计算了下煤层切顶自成巷巷旁支护阻力。以典型极近距离煤层为工程背景,开展了不同开采方法的数值试验对比研究,结果表明,提出的自成巷控制方法使巷道围岩应力降低59.8%,巷道顶板变形减少70.8%,并明确了极近距离煤层开采无煤柱自成巷控制机理。在此基础上,开展了典型极近距离煤层工程设计及现场应用研究,结果表明该方法有效降低了矿压显现程度,保证了自成巷的安全稳定控制。

深层、超深层定向钻井中若干基础研究进展与展望

深层、超深层定向钻井具有“垂深大与水平延伸远”的双重特征,受到复杂地层、高温高压、超长裸眼等多重因素约束,其安全高效作业面临着更大的全方位技术挑战。为此,着眼于深层、超深层定向钻井的提速提效问题,系统总结了定向钻井的发展概况与技术特点,选取了深层、超深层定向钻井中力学方面的几个重要基础问题,分析了国内外专家学者的相关研究进展和最新研究成果,最后展望了深层、超深层定向钻井基础理论研究发展趋势并提出相关建议。研究结果表明:①大小偏差融合控制算法兼顾了井眼轨迹的控制精度、光滑度等多目标约束,适应于深层、超深层条件下井眼轨迹实时控制要求;②合理优化振动减阻工具个数、安放位置及其激励力幅值,可显著降低井下管柱摩阻,并有效提高机械钻速;③基于误差补偿机制的机械钻速融合预测模型既保留了机理模型的可解释性,又具有较高的预测精度;④套管复合磨损预测模型突破了经典“单月牙”模式的局限性,实现了复合模式下套管磨损形状与深度的同步预测。结论认为,深层、超深层定向井和水平井是未来油气井工程的重要发展方向之一,需要加强多因素耦合机理、钻井延伸极限、机理与数据融合驱动等方面的基础研究,以推动复杂油气井工程基础理论的创新与发展,为深层、超深层钻井工程技术进步提供必要的基础理论支撑。

新能源汽车的驱动电机系统研究和设计

通过改变新能源汽车的能源消耗方式,能提高节能减排工作效果,促进新能源开发利用工作顺利进行,保证社会经济实现可持续发展。科学技术的发展决定着新能源汽车的研发进程,驱动电机系统作为新能源汽车的关键点,涉及新能源汽车研发的核心技术,相关人员要注重新能源汽车的驱动电机系统研究和设计,提高设计的合理性。

半乳糖氧化酶的生物学改造研究进展

半乳糖氧化酶是一种重要的生物催化剂,具有催化效率高和绿色环保的特点,在生物传感器、食品、医疗和化工等领域得到广泛应用。然而,天然的半乳糖氧化酶存在稳定性差、催化效率低、回收成本高等缺陷,限制了其在食品安全和生物医学等领域的应用。随着基因工程和蛋白质工程的发展,人们可以对半乳糖氧化酶进行有目的的改造,以提高酶的性能或者获得新功能的重组酶。因此,追求具有重要催化能力和强大功能的半乳糖氧化酶成为该领域的研究热点。本文综述了半乳糖氧化酶的分子结构、催化机理等基本信息,并分析总结了半乳糖氧化酶进行生物学改造的相关案例,旨在为半乳糖氧化酶相关研究者提供新的思路和方法。

轮胎阶梯式直压硫化内模具的运动学仿真研究

对225/40R18轮胎的阶梯式直压硫化内模具(简称内模具)进行运动学仿真研究。通过设定连杆和运动副以及用STEP函数控制内模具的运动,进行仿真分析得到了在活塞外杆、活塞内杆、宽鼓瓦、窄鼓瓦中心位置设置的观测点的位移情况。结果表明,阶梯式内模具的运动平稳、连续,且不会发生干涉。

高阿丁枫人工中龄林生长对坡向和密度的响应

为了解高阿丁枫人工林的生长过程,2021年对林龄21 a的高阿丁枫人工林进行每木检尺,以胸径作为标准木选择的依据,西南坡不同密度中各选择1株,南坡不同密度中各选择3株高阿丁枫标准木作为解析木,分析不同坡向和造林密度组合的林木生长差异。结果表明:林龄21 a时,不同坡向和造林密度组合的高阿丁枫林木的平均胸径、树高和材积分别为17.60~20.78 cm、25.73~28.51 m和0.3186~0.4293 m3,林木尚处于旺盛的生长阶段;处理组合间以上生长量均呈现极显著的差异。林龄1~9、1~10、8~16 a期间分别是胸径、树高和材积的速生期,其连年生长量最高分别达2.19 cm/a、2.74 m/a和4.3966×10^(-2)m^(3)/a。坡向、密度及其交互作用显著或极显著地影响高阿丁枫林木的生长。高阿丁枫隶属热区长寿命大径材树种,速生期延续较长,其生长对立地和密度较为敏感。优质高效的高阿丁枫人工林培育应选择最适宜的立地和造林密度,并且适时开展密度的动态调控。综上所述,造林密度通过影响树高生长从而影响材积生长,南坡采用3 m×2 m×5 m非均匀密度造林的单株总材积最大。研究结果可应用于生产实践中高阿丁枫优质高效人工林培育的立地选择和密度控制。