大锻件热成形可控机制的研究

本文采用热力模拟、微观模拟和计算机数值模拟相结合的模拟技术,根据变形条件、热力参数与成形精度和组织结构的相关性原理,以护环、曲轴大锻件为例,进行了热成形可控性的研究。

盲结肠膀胱术加强输出道可控机制的临床研究

目的 改进盲结肠膀胱术输出道手术方法 ,建立一种控尿可靠、插管方便、并发症少的可控输出道。 方法 对 4 7例膀胱癌患者行膀胱癌根治切除 ,37例采用去结肠带建立盲结肠贮尿囊 ,10例非管状化建立盲结肠贮尿囊 (改良Indianapouch) ,截取末端回肠 12～ 14cm ,剖开肠管重叠绕圈缝合成双层肠壁结构 ,回盲肠交界处浆肌层缝合 ,构筑回盲部小乳头状回肠套叠结构 ,建成长 12cm的输出道。盲肠端与盆腔腹壁缝合 ,远端与脐孔吻合 ,全长固定潜行于腹壁下贮尿囊和腹直肌之间。 结果 全部患者插管顺利 ,白天完全可控 4 5例 ,夜间完全可控 4 4例 ,术后 6个月输出道闭合压 4 0 .5～ 12 5 .6cmH2 O ,充盈状态输出道最大闭合压明显高于空虚状态 (P <0 .0 5 )。 结论 改进的缩窄末端回肠输出道是一种较理想的可控输出道。

初中生数学学习策略的可控心理影响机制

运用问卷调查和访谈的方法,探讨了主要可控心理因素对初中生数学学习策略的影响机制。结果表明,所纳入的可控心理因素具有良好的代表性;可控心理因素对初中生数学学习策略的影响机制主要体现为数学学习动机、策略意识、积极归因和困难应对感对数学学习策略有显著的直接效应。研究提示,数学学习策略的教学应重视可控心理因素的作用并处理好各因素之间的关系。

发展我国风险投资体制研究

我国在高科技产业竞争与风险投资业的国际竞争中处于明显的弱势 ,在这样的历史条件下如何发展我国风险投资业 ,我们认为 ,要建设好我国风险投资体制 。

关于发展风险投资体制的研究

知识经济时代的到来 ,世界许多国家都在全力发展高科技产业 ,而发展我国高科技产业 ,发展风险投资体制是金融支持高科技产业发展的重要保证。作者通过对国外风险投资业的考察与理论分析认为 ,要建设好我国的风险投资体制 ,关键是要建立起对科技创业企业的孵化机制和高科技企业集团对风险投资的可控机制。

《2018-2019机械工程学科发展报告(机械制造)》——展望(二)

非传统加工领域:研发多物理场、多工艺复合的激光、超声、电磁、射流、电子束等非传统加工的高精可控机制、技术与装备,实现新型难加工材料的微加工与复杂结构成形,研究3D打印的新方法等新技术与装备。

改良可控性回肠膀胱控尿机制的临床研究

目的探讨改良可控性回肠膀胱临床应用的效果.方法膀胱癌行根治性膀胱切除尿流改道患者12例,采用改良的回肠乳头瓣作为输出道,外口与脐孔作皮瓣嵌入防狭窄吻合,去管化回肠浆膜下隧道抗返流技术.结果12例随访14～50个月,昼夜控尿满意,尿动力学显示:储尿囊容量350～720(435±88)ml,充盈时内压15～32(20±5)cm H2O,储尿囊充盈时输出道最大闭合压力74～142(98±23)cm H2O,空虚时为49～105(68±20)cm H2O,2者差异有统计学意义(t=8.82,P<0.01);充盈过程中无收缩波出现.结论改良回肠乳头瓣输出道及去管化回肠浆膜下隧道抗返流技术是比较理想的可控技术改进.

Preparation of ultrafine silver powders with controllable size and morphology

The ultrafine silver powders were prepared by liquid reduction method using Arabic gum as dispersant.The effects of different dispersants,pH values,and temperature on the morphology and particle size of silver powders were investigated.It is found that Arabic gum can better adsorb on silver particles via chemical adsorption,and it shows the best dispersive effect among all the selected dispersants.The particle size of silver powders can be finely tuned from 0.34 to 4.09μm by adjusting pH values,while the morphology of silver powders can be tuned by changing the temperature.The silver powders with high tap density higher than 4.0 g/cm3 were successfully prepared in a wide temperature range of 21.8-70°C.Especially,the tap density is higher than 5.0 g/cm3 when the temperature is optimized to be 50°C.The facile process and high silver concentration of this method make it a promising way to prepare high quality silver powders for electronic paste.

A New Approach to Extensible Continuum Robot Control Using the Sliding-Mode

In this paper, the authors present a new control strategy for continuous backbone （continuum） ＂trunk and tentacle＂ robots. Control of this emerging new class of robots has proved difficult due to the inherent complexity of their dynamics. Using a recently established full dynamic model, the authors introduce a new nonlinear model-based control strategy for continuum robots. The approach is applicable to continuum robots which can extend/contract as well as bend throughout their structure. Results are illustrated using the mathematical model of a three-section, six-degree of freedom planar continuum robot.

Component-based Control Software Design for Flexible Manufacturing System

A new method that designs and implements the component-based distributed & hierarchical flexible manufacturing control software is described with a component concept in this paper. The proposed method takes aim at improving the flexibility and reliability of the control system. On the basis of describing the concepts of component-based software and the distributed object technology, the architecture of the component-based software of the control system is suggested with the Common Object Request Broker Architecture (CORBA). And then, we propose a design method for component-based distributed & hierarchical flexible manufacturing control system. Finally, to verify the software design method, a prototype flexible manufacturing control system software has been implemented in Orbix 2.3c, VC + + 6. 0 and has been tested in connection with the physical flexible manufacturing shop at the WuXi Professional Institute.

On stochastic optimal control of partially observable nonlinear quasi Hamiltonian systems

A stochastic optimal control strategy for partially observable nonlinear quasi Hamiltonian systems is proposed. The optimal control forces consist of two parts. The first part is determined by the conditions under which the stochastic optimal control problem of a partially observable nonlinear system is converted into that of a completely observable linear system. The second part is determined by solving the dynamical programming equation derived by applying the stochastic averaging method and stochastic dynamical programming principle to the completely observable linear control system. The response of the optimally controlled quasi Hamiltonian system is predicted by solving the averaged Fokker-Planck-Kolmogorov equation associated with the optimally controlled completely observable linear system and solving the Riccati equation for the estimated error of system states. An example is given to illustrate the procedure and effectiveness of the proposed control strategy.

Credibility and Security of Weighing System for Large Structure Object

The weighing system designed for large structure object is mainly composed of three parts. The part of hydraulic system is made up of hydraulic cylinders, high pressure hydraulic hoses and electric pumps; the part of computer controlling system comprises pressure sensors, displacement sensors, data acquisitions, RS 485 network and the computer controlling model; the part of loading system is composed of the fulcrum structure and the concrete girder. The measurement principle and composition of the weighing system are discussed in this paper. Credibility and security of the weighing system are fully considered during the design phase. The hydraulic system is controlled by pilot operated check valves in case of the sudden loss of system pressure. The states of all gauges and RS485 network are monitored by computer controlling system functioning in different modules. When the system is running incorrectly, it will be switched to manual mode and give alarm. The finite element method is employed to analyze fulcrum structure so that the system has enough intensity to be lifted. Hence the reliability of the whole system is enhanced.

Development of Independent Moving Puppet Robot

This paper is about the automation of the marionette performance. A method to solve the problem on the mobility of the automated marionette performance is proposed. Since it is difficult to control the marionette by hands, as an alternative, the automated marionette is studied. However, the automtic marionette performance is limited in the silence and mobility. Therefore, an independent shifter to move freely on the stage is required. The magnetic device which connects the movable robot and the marionette controlling robot is conceived. The magnetic device is improved and applied by considering the features of the marionette robot, which is the irregular movement of the marionette controller and of the parallel limited area. The burden of being trapped on the magnet is minimized by dividing the robot to the upper and lower parts of the marionette performance stage. The direction of the magnet is considered to make the mobile robot to move freely. Thus, the efficiency and safety of the device is confirmed by balancing the strength with the permanent magnet.

Control Strategies for PM Synchronous Machine Controlled Rectifier Intended for Heavy-Duty Vehicle

In order to charge batteries and supply all the electrical devices like wheel-motors used in a heavy-duty hybrid electric vehicle, a solution consists in using an assembly permanent magnet generator driven by a diesel engine and a three-phase insulated gate bipolar transistor/diodes bridge controlled rectifier connected to the battery. In this work, hysteresis current control strategies combined with a judicious current sensing mode for the assembly permanent magnet synchronous machine-controlled rectifier are investigated. Main issues first concern the different kinds of transistors switching modes allowed by the proposed current sensing mode when the machine operates either as a generator or as a motor. Second, the modulated hysteresis method is presented, which merges the performances of robustness and dynamic of the classical hysteresis method and imposes the switching frequency alike pulsewidth modulation techniques. A test bench at reduced power permits to test the switching modes as well as classical and modulated hysteresis methods for both motor and generator operating modes and to validate the simulation predictions. The digital signal processor algorithm elaborated for the control strategy is flexible and adaptable to all kinds of transistor switchings and machine operating modes.

UV Wavelength Tunable Output System Controlled by Microprocessor

UV wavelength auto-tuned tuned output system is realized by the difference method. Controlled by the microprocessor, output wavelength auto- tracking is achieved.Besides, equipment self-checking auto-positioning and temperature correct are realized,The wavelength tuned output efficiency in the experiment is better than 97 %.

Control of Multiple PWM Servos by a Single Programmable Timer

An algorithm for control of several servo motors by a mi- crocontroller is presented. The limited ntanber of progranunable timers on the majority of micnocntrollers presents a problem for multiple generation of timing pulses. Two software approaches are discussed in the paper and experimental results given for operation of a set of small servos using a single timer.

Quasi Serializable Concurrency Control in Distributed Real-Time Database Systems

This paper formally defines and analyses the new notion of correctness called quasi serializability, and then outlines corresponding concurrency control protocol QDHP for distributed real-time databases. Finally, through a series of simulation studies, it shows that using the new concurrency control protocol the performance of distributed real-time databases can be much improved.

Compound control for speed and tension multivariable coupling system of reversible cold strip mill

To weaken the nonlinear coupling influence among the variables in the speed and tension system of reversible cold strip mill, a compound control(CC) strategy based on invariance principle was proposed. Firstly, invariance principle was used to realize static decoupling between the speed and tension of reversible cold strip mill. Then, considering the influence caused by the time variation of steel coil radius and rotational inertia of the left and right coilers, as well as the uncertainties, a CC strategy that is composed of extended state observer(ESO) and global sliding mode control(GSMC) with backstepping adaptive was proposed,which further realized dynamic decoupling and coordination control for the speed and tension system. Theoretical analysis shows that the resulting closed-loop system is global bounded stable. Finally, the simulation was carried out on the speed and tension system of a 1422 mm reversible cold strip mill by using the actual data, and through the comparison of the other control strategies, validity of the proposed CC strategy was shown by the results.

The Implementation of Decision Support System for Realizing Effective Usability of CNC Operator Knowledge Capturing System

This article describes experimental evaluations of the authors＇ previous studies on the knowledge-based system （KBS） aimed at capturing and managing CNC （Computer Numerical Control） operator knowledge. The proposed KBS follow thinking steps of CNC operators when they assess machining parameters described in the CAM （Computer Aided Manufacturing） file before proceeding to CNC machining processes. Also, the decision support system equipped with expert system （ES） has been proposed to realize efficient knowledge capturing system and effective usability of captured knowledge, and to recommend actions and decisions. From the viewpoint of providing useful information, the KBS should be aware of context or constraints in which the user has to deal with. In this study, the usefulness of DSS （Decision Support System） and ES is experimentally evaluated using real cases. Comparing the results of the testing participants with and without the DSS and ES, the effectiveness and usefulness were demonstrated. In addition, it was shown that the proposed system is also useful to narrow the discrepancies between CAM and CNC operators, focusing on CNC milling operations.

Visual Tracking System for Welding Seams

To track the narrow butt welding seams in container manufacture, a visual tracking system based on smart camera is proposed in this paper. A smart camera is used as the sensor to detect the welding seam. The feature extraction algorithm is designed with the consideration of the characteristics of the smart caraera, which is used to compute the error between the welding torch and the welding seam. Visual control system based on image is preseated, which employs a programmable controller to control a stepper motor to eliminate the tracking error detected by the smart camera. Experiments are conducted to demonstrate the effectiveness of the vision system.