英国科学家发明革命性的超声波清洗装置

英国南安普顿大学的一个科研团队在长期基础研究之上．开发出新型超声波清洗装置。该装置能大幅度降低使用高压水枪清洗装置时的耗水和耗电．能广泛用于医疗卫生领域、食品加工、机械制造业、核工业等领域。     

Project risk management and design flexibility: Analysing a case and conditions of complementarity

We explore how risk management and design flexibility interplay in major (infrastructure) projects, using the £4.2bn Terminal 5 project to expand London's Heathrow airport. By juxtaposing these two conceptual frames, we unearth the conditions under which they can be complements for managing the tension between efficiency and effectiveness central to these projects. Building design flexibility - through modular or safeguarded integral architectures - increases adaptability to accommodate evolving requirements which is necessary to attain effectiveness. Efficiency, in turn, demands risk management to deliver the project ‘on time, within budget’. We explain variation in the interplay between the two approaches, highlighting the moderating role of the developer's relationship with the customer. Strong co-operation, particularly in a stable environment, encourages investments in design flexibility. Risk management practices prevail when co-operation breaks down. Another insight is that co-location and continuity of key project staff are themselves inadequate conditions to sustain co-operation.     

Muscle-fiber array inspired,multiple-mode,pneumatic artificial muscles through planar design and one-step rolling fabrication

Advances in development of artificial muscles have enabled creation of soft robots with biological dexterity and self-adaption in unstructured environments; however, production of scalable artificial muscles with multiple-mode actuations remains elusive. Inspired by muscle-fiber arrays in muscular hydrostats, we present a class of versatile artificial muscles called MAIPAMs (muscle-fiber array inspired pneumatic artificial muscles), capable of multiple-mode actuations (such as parallel elongation-bending-spiraling actuations, 10 parallel bending actuations and cascaded elongation-bending-spiraling actuations). Our MAIPAMs consist of active 3D elastomer-balloon arrays reinforced by a passive elastomer membrane, achieved through a planar design and one-step rolling fabrication approach. We introduce prototypical designs for the MAIPAMs and demonstrate their muscle-mimic structures and versatility, as well as their scalable ability to integrate flexible but non-stretchable layers for contraction and twisting actuation modes and compliant electrodes for self-sensing. We further demonstrate that this class of artificial muscles shows potential for versatile robotic applications, such as carrying a camera for recording videos, gripping or manipulating objects, and climbing a pipe-line.     

Robust control of a system with a pneumatic spring

Recently, series elasticity has been realized using pneumatics in human-robot interaction systems. Pneumatic circuits provide not only a flexible power transmission, but also the elastic element in a series elastic actuator (SEA). Pneumatic series elastic systems involve more than twice the number of parameters that influence system behaviors in comparison with rigid robotic systems. In this study, a position controller that eliminates the need of identifying a system model by employing the time delay estimation (TDE) technique is proposed for pneumatic SEA systems. The TDE technique is effective in compensating for system dynamics and all uncertainties involved in system behaviors without imposing computation load. TDE error is cancelled out through a learning way, which improves control performance and leads to asymptotic stability. A simulation study demonstrates the robustness of the proposed controllers against uncertainties imposed on the motor system as well as uncertainties on the end-effector. The simulation shows the efficacy of the learning compensation for TDE error.     

Improvement of rectification effects in diffuser/nozzle structures with viscoelastic fluids

This paper reports the improvement of rectification effects in diffuser∕nozzle structures with viscoelastic fluids. Since rectification in a diffuser∕nozzle structure with Newtonian fluids is caused by inertial effects, micropumps based on this concept require a relatively high Reynolds numbers and high pumping frequencies. In applications with relatively low Reynolds numbers, anisotropic behavior can be achieved with viscoelastic effects. In our investigations, a solution of dilute polyethylene oxide was used as the viscoelastic fluid. A microfluidic device was fabricated in silicon using deep reactive ion etching. The microfluidic device consists of access ports for pressure measurement, and a series of ten diffuser∕nozzle structures. Measurements were carried out for diffuser∕nozzle structures with opening angles ranging from 15° to 60°. Flow visualization, pressure drop and diodicity of de-ionized water and the viscoelastic fluid were compared and discussed. The improvement of diodicity promises a simple pumping concept at low Reynolds numbers for lab-on-a-chip applications.     

Adiabatic flow of hydrogen gas through a rocket nozzle with and without composition change

A procedure is described for determining the characteristics of adiabatic flow through a rocket nozzle with and without composition change. The method of calculation is illustrated for the expansion of pure hydrogen gas from a chamber temperature of 306° K. and a pressure of 20.42 atm. to atmospheric pressure.The study indicates that the exhaust velocity and temperature are highest for flow where complete equilibrium is reached at each temperature with respect to the reaction

$\text{H}{}_2\text{?2H}$

Flow with composition change requires a nozzle exit to nozzle throat area ratio somewhat greater than that determined for adiabatic flow without composition change for the same ratio of chamber pressure to exit pressure.The residence time in a given temperature range is computed as a function of gas temperature for the two types of flow. The results of this calculation may be used to determine the minimum required reaction rates which allow composition changes during flow through the nozzle.     

项目柔性及其模拟与估值方法--风险调整贴现率法与期权估值法的比较研究

源于经营管理的灵活性，投资项目通常是具有柔性的，允许继续等待或相机进行战略调整而不是立刻决定是否要进行投资。通过等待，可获得更多有用信息并占有延期决策期间所具有的资金时间价值，这使得投资者可以尽可能减小项目失败的风险，获得最大收益。因此，项目柔性是具有价值的。本文探讨了项目柔性及其模拟与估值方法，并对风险调整贴现率法与期权估值法这两种方法进行了比较研究。本文认为，期权定价和决策分析方法是两种互补的模拟方法，两者可以很好地结合起来。最后，本文介绍了一种把决策分析和动态过程方法结合起来的简便的期权估值方法。     

利用UML进行BBS论坛系统分析与设计

BBS俗称论坛系统,是互联网上一种交互性极强、网友喜闻乐见的信息服务形式。根据相应的权限,论坛用户可以进行浏览信息、发布信息、回复信息、管理信息等操作,从而加强不同用户间的文化交流和思想沟通。本文利用UML统一建模语言对BBS论坛系统进行了面向对象的分析与设计,主要内容包括用例建模、静态建模和动态建模。在具体建模过程中,给出了系统用例图、管理模块类图、管理用户类图、登录时序图和增加板块时序图。     

Second order sliding mode output feedback control with switching gains—Application to the control of a pneumatic actuator

This paper proposes a switching gains output feedback controller, which is a sample-based second order sliding mode one. First, constructive convergence conditions are established for the controller, in the unperturbed and perturbed cases. Then, a gain adjustment mechanism of the gain, based on the aforementioned convergence conditions, allows us to reduce gain magnitude, and then to reduce the chattering effect. This new algorithm is experimentally applied for the position control of an electropneumatic actuator.     

Perspective of drug design with high-performance computing

In recent decades,the development of high-performance computing (HPC)continues to follow Moore's law,with many computational methods in drug design experiencing...     

Discrete-time nonlinear observer design with general criteria

A class of discrete-time nonlinear system and measurement equations having incrementally conic nonlinearities and finite energy disturbances is considered. A linear matrix inequality-based design approach is presented, which guarantees the satisfaction of a variety of performance criteria ranging from simple estimation error boundedness to dissipativity. Some simulation examples are included to illustrate and provide support to the proposed design methodology.     

Manipulating liquid plugs in microchannel with controllable air vents

An air venting element on microchannel, which can be controlled externally and automatically, was demonstrated for manipulating liquid plugs in microfluidic systems. The element's open and closed statuses correspond to the positioning and movement of a liquid plug in the microchannel. Positioning of multiple liquid plugs at an air venting element enabled the merging and mixing of the plugs. Besides these basic functions, other modes of liquid plug manipulations including plug partitioning, multiple plug mixing, and spacing adjustment between liquid plugs, were realized using combination of multiple elements. The structure, operation, and some functions of the element were demonstrated with a microfluidic chip application. The performances of the element including its failure modes, threshold flow rate, and structural optimization were also discussed.     

薄板坯连铸机在线软压下浅析

本文介绍了扇形段软压下在薄板坯连铸机上的应用及技术特点,分析了该技术对铸坯质量的作用和影响,给出了软压下技术工艺参数控制的优化结果。     

中国特色的政府绩效审计模式设计

随着我国服务型政府的确立,开展政府绩效审计,强化政府受托责任具有重要的现实意义.在剖析了我国推行绩效审计的制约因素基础上,提出从改革审计体制入手,建立问责和风险预警机制,从而构建具有中国特色的绩效审计模式.     

Sliding manifold design for linear systems with unmatched disturbances

This paper offers an efficient sliding manifold design method that minimizes the impact of unmatched disturbances onto SM dynamics and system accuracy. System sensitivity upon unmatched constant or slowly varying external disturbance vector is evaluated by the steady-state dependent criterion function. An infinite set of sliding manifolds that minimize the chosen optimization criterion is determined and a way of selecting a manifold out of that set that provides adopted SM dynamics is suggested. The proposed approach has been demonstrated on numerical examples and verified by simulations.     

Analysis and design of multi-input-multi-priority buffering systems with binomial feedback

The buffer design problem is studied for the cases where there exist single- and multiple-input lines with Poisson or Poisson bursts arrivals, periodic block or batch type removals, and binomial feedback.Using traffic intensity σ, block size c, and the feedback probability P_a as parameters, the analytical expressions concerning the average fractional information loss, the channel utilization and the average buffering delay in relation to the buffer length are derived. These relationships are computed for a set of parameter values and are plotted to be used as a basis for the buffer design. The present study should be valuable in designing engineering systems such as time sharing computer systems, information compression systems, computer networks, road traffic simulators, telephone exchanges etc. An illustrative example of a single-input buffer system of the type considered is fully discussed.     

Passive fuzzy controller design for nonlinear systems with multiplicative noises

This paper proposes a passive fuzzy controller design methodology for nonlinear system with multiplicative noises. Applying the Itô's formula and the sense of mean square, the sufficient conditions are developed to analyze the stability and to design the controller for stochastic nonlinear systems which are represented by the Takagi-Sugeno (T-S) fuzzy models. The sufficient conditions derived in this paper belong to the Linear Matrix Inequality (LMI) forms which can be solved by the convex optimal programming algorithm. Besides, the passivity theory is applied to discuss the effect of external disturbance on system. Finally, some numerical simulation examples are provided to demonstrate the applications of the proposed fuzzy controller design technique.     

Direct data-driven design of LPV controllers with soft performance specifications

If only experimental measurements are available, direct data-driven control design becomes an appealing approach, as control performance is directly optimized based on the collected samples. The direct synthesis of a feedback controller from input-output data typically requires the blind choice of a reference model, that dictates the desired closed-loop behavior. In this paper, we propose a data-driven design scheme for linear parameter-varying (LPV) systems to account for soft performance specifications. Within this framework, the reference model is treated as an additional hyper-parameter to be learned from data, while the user is asked to provide only indicative performance constraints. The effectiveness of the proposed approach is demonstrated on a benchmark simulation case study, showing the improvement achieved by allowing for a flexible reference model.