基于马尔科夫的串联设计活动产品设计缺陷评估

为了有效管理产品设计缺陷,提出利用马尔科夫对设计活动产生的设计缺陷进行评估和预测。首先,从过程的角度分析每个设计活动的设计缺陷影响因素,构建设计缺陷影响因素矩阵。然后利用设计缺陷影响因素定义了产品设计缺陷的综合评价指标设计缺陷度,并由历史数据拟合了缺陷度和设计缺陷发生频率的关系,进而构建了基于马尔科夫的串联设计活动产品设计缺陷发生概率的评估预测模型。实际应用表明,该方法可用于串联设计活动的产品设计缺陷评估预测,从而为设计缺陷的控制管理提供有效支持。

阀门串联设计可靠性分析

本文通过对舰船动力系统中一道阀和二道阀串联设计时单元故障模式及失效情况的比较分析,论述了两种设计方法对系统可靠性的影响,并且作为分析机械可靠性的一种方法,也可为相关系统可靠性设计和安全分析提供参考。

并串联系统设计优化

建立了并串联系统设计优化的两类模型 ,提出了遗传算法与模式搜索。

负刚度扭转超结构力学性能研究

通过屈曲变形实现非损伤耗散能量的负刚度超结构,为可重复使用的缓冲防护器件提供了新的设计思路,但其耗散能力较弱、难以过载保护的缺点限制了实际应用.为增强耗能性能及最大允许变形量,将负刚度铰接梁与具有压扭效应的斜杆串联组合,设计了一种负刚度扭转超结构,通过引入扭转变形缓解了过载导致的应力集中.建立了负刚度扭转单元模型,通过刚度匹配设计实现了对力学性能的调控,使负刚度扭转超结构表现出突跳行为,产生加卸载曲线不重合的迟滞现象,从而极大地提高了能量耗散能力.通过结构参数及刚度关系的优化设计,负刚度扭转超结构的最大等效压缩应变可达71%,相同层数下,能量耗散能力可以达到传统屈曲梁超结构的两倍.

BIM技术在表皮和场地前期设计中的应用

BIM给行业带来的革命和优势已经逐渐显现,然而它从一开始就不仅仅是一个软件的功劳,而应该是全行业改革的方向:串联设计、施工、运维多方,打通行业间的隔阂与障碍,形成一个完整的建筑生命周期。然而眼下,相较于BIM施工、BIM运维等热门领域,BIM在设计前期的作用往往被人忽视,因而本文以此为切入口就BIM在前期设计中带来的优势与价值进行探讨。

一种特殊拖拉机传动箱设计开发

将梭式挡和爬行挡在同一个传动箱壳体中进行串联设计,同时实现梭式挡和爬行挡功能,增加拖拉机挡位,满足特殊作业需求。

串联式设计小容量MLCC的容量分析

为了研究两种不同内电极结构对串联式设计小容量(标称容量≤1 pF)MLCC的容量的影响,作出了这两种内电极结构的等效电路并进行分析,再对具有这两种内电极结构的MLCC的实际样品进行了测试以验证分析结论,结果发现两种样品的实际容量存在显著差异。这种差异可能不利于设计命中率,形成差异的主要原因是MLCC的外电极对具有这两种内电极结构的MLCC的容量的影响程度不同。

Optimization of lane assignment for signalized T-intersection based on VISSIM

In order to improve the performance of the signalized intersection,an unconventional scheme tandem design(TD)is proposed.A simulation experiment is conducted to evaluate the capacity and delay under the unconventional scheme and two conventional lane assignment schemes.First,the VISSIM is employed as microsimulation to obtain the delay of different designs at signalized T-intersections under different conditions of traffic flow and turning proportion.Secondly,a method based on discriminant analysis(DA)is proposed to determine the best design scheme using the flow and turning proportion as inputs.Finally,a case study in Changsha city,China is used to demonstrate the efficiency and accuracy of these findings.The results indicate that the traffic flow and turning proportion are the crucial factors in scheme selection of lane assignment.Different from the previous research,the TD has better performance over various traffic flow levels.Furthermore,a proper proportion of left turns makes TD an outstanding option,which can reduce the delay and decrease the average number of stops and queue length significantly.However,the proportion should not be too high or too low.The research results can help practitioners obtain a quantitative view of appropriate design schemes at signalized intersections when trying to relieve traffic congestion according to different traffic conditions.

Design and Implementation of a Digitally Controlled Photovoltaic System Using Series Connected Buck Converters

In PV （photovoltaic） power systems, a MPPT （maximum power point tracking） algorithm is vital in increasing their efficiency. But it is also vital to take into account the non ideal conditions resulting from complex physical environments in such PV power systems. To minimize the degradation of performances caused by these conditions, and therefore adding reliability and robustness, this paper presents an implementation of a digitally controlled system using a topology based on series connected DC-DC buck converters for a stand-alone PV power system applications, operating with local and autonomous controls, to track the maximum power points of PV modules in non ideal conditions. Simulations are carried out by using C-MEX S-functions under MATLAB-SIMULINK environment. A PV system of 1.44 kWc is described and simulation results are presented.

Design and experimental study of the SPKM165, a five-axis serial-parallel kinematic milling machine

A five-axis serial-parallel kinematic milling machine, the SPKM 165, is introduced. This machine consists of a three-degree of-freedom parallel module and a two-degree-of-freedom serial table. The SPKM 165 is capable of five-face machining. A discussion of the inverse kinematics of the five-axis control is provided. A dimensional synthesis procedure is presented in terms of motion/force transmissibility. Finite-element analysis was used to evaluate the stiffness of a CAD model before the machine was manufactured. Kinematic calibration was implemented to improve the accuracy of the end effector. The results of a calibration experiment are presented. The stiffness of the developed machine was then measured. Milling experiments were conducted, and the test piece showed that the developed machine has satisfactory performance.

Design and Optimization of Tandem Arranged Cascade in a Transonic Compressor

This study proposed a design and optimization strategy for a tandem arranged cascade using the Non-dominated Sorting Genetic Algorithm(NSGA) Ⅱ multi-objective optimization algorithm and Back Propagation(BP) neural network technology. The NASA Stage 35 was employed as the initial bench mark in the present study and five geometric control parameters were working as the optimization parameters aiming to enhance the aerodynamic performance in terms of total pressure rise and efficiency. Results showed that the feasibility and capability of the proposed optimization strategy was successfully examined. In view of the fact that the initial tandem cascade(directly scaling down from NASA Stage 35) cannot guarantee the aerodynamic performance, first optimization trial was conducted to optimize the initial design. Results showed that the optimum can improve the flow quality whereas the separation on the blade is decayed or even eliminated particularly at the tip and root regions. However, compared with the initial tandem design, the enhancement in total pressure ratio(0.47%) and efficiency(1%) are too small to be noticed. Second investigation was particularly emphasizing on a high turning tandem compressor with an increment by 28°. The pressure rise and efficiency were augmented by 1.44% and 2.34%(compared to the initial tandem design), respectively. An important conclusion can be drawn that the optimization strategy is worthy to be used in high turning compressors with a considerable performance improvement.

Numerical Investigation & Comparison of a Tandem-Bladed Turbocharger Centrifugal Compressor Stage with Conventional Design

Extensive numerical investigations of the performance and flow structure in an unshrouded tandem-bladed centrifugal compressor are presented in comparison to a conventional compressor.Stage characteristics are explored for various tip clearance levels,axial spacings and circumferential clockings.Conventional impeller was modified to tandem-bladed design with no modifications in backsweep angle,meridional gas passage and camber distributions in order to have a true comparison with conventional design.Performance degradation is observed for both the conventional and tandem designs with increase in tip clearance.Linear-equation models for correlating stage characteristics with tip clearance are proposed.Comparing two designs,it is clearly evident that the conventional design shows better performance at moderate flow rates.However;near choke flow,tandem design gives better results primarily because of the increase in throat area.Surge point flow rate also seems to drop for tandem compressor resulting in increased range of operation.

Design of a new tandem wings hybrid airship

It is scientifically important science value and engineering promising to develop the buoyancy-lift integrated hybrid airship for high attitude platform.Through the numerical method,a new tandem wings hybrid airship with both higher utility value and economy efficiency was obtained and its total performance and technical parameters were analyzed in detail.In order to further improve the lift-drag characteristics,we implemented the optimization design for aerodynamic configuration of tandem wings hybrid airship via the response surface method.The results indicate that the tandem wings hybrid airship has considerable volume efficiency and higher aerodynamic characteristics.After optimization,the lift-drag ratio of this hybrid airship was increased by 6.08%.In a given gross lift condition,tandem wings hybrid airship may provide more payload and specific productivity.Furthermore,the size of tandem airship is smaller so the demand for skin flexible materials can be reduced.Results of this study could serve as a new approach to designing buoyancy-lifting integrated hybrid airship.

Powertrain design and energy management of a novel coaxial series-parallel plug-in hybrid electric vehicle

For a series plug-in hybrid electric vehicle,higher working efficiency can be achieved by the drive system with two small motors in parallel than that with one big motor alone.However,the overly complex structure will inevitably lead to a substantial increase in the development cost.To improve the system price-performance ratio,a new kind of series-parallel hybrid system evolved from the series plug-in hybrid system is designed.According to the technical parameters of the selected components,the system model is established,and the vehicle dynamic property and pure electric drive economy are evaluated.Based on the dynamic programming,the energy management strategy for the drive system under the city driving cycle is developed,and the superiority validation of the system is completed.For the studied vehicle driven by the designed series-parallel plug-in hybrid system,compared with the one driven by the described series plug-in hybrid system,the dynamic property is significantly improved because of the multi-power coupling,and the fuel consumption is reduced by 11.4%with 10 city driving cycles.In a word,with the flexible configuration of the designed hybrid system and the optimized control strategy of the energy management,the vehicle performance can be obviously improved.

Tandem nanocatalyst design: putting two step-reaction sites into one location towards enhanced hydrogen transfer reactions

Efficient tandem reactions on a single catalytic nanostructure would be beneficial to improving chemical transformation efficiency and reducing safety implications. It is imperative to identify the active sites for each single step reaction so that the entire reaction process can be optimized by designing and integrating the sites. Herein, hydrogen transfer reaction is taken as a proof-of-concept demonstration to show that the spatial integration of active sites is important to the catalytic efficiency of the entire process in tandem reactions. We identified specific active sites (i.e., various sites at faces versus corners and edges) for formic acid decomposition and alkene/nitrobenzene hydrogenation-the two steps in hydrogen transfer reactions, by employing three different shapes of Pd nanocrystals in tunable sizes. The investigation reveals that the decomposition of formic acid occurs preferentially at the edge sites of cubic nanocrystal and the plane sites of octahedral/ tetrahedral nanocrystals, while the hydrogenation takes place mainly at the edge sites of both cubic and octahedral/ tetrahedral nanocrystals. The consistency of active edge sites during different step reactions enables cubic nanocrystals to exhibit a higher activity than octahedral nanocrystals in hydrogen transfer reactions, although octahedrons offer comparable activities to cubes in formic acid decomposition and hydrogenation reactions. Guided by these findings, we further improved the overall performance of tandem catalysis by specifically promoting the limiting step through nanocatalyst design. This work provides insights into the rational design of heterogeneous nanocatalysts in tandem reactions.