球状三嵌段共聚物在圆柱型受限空间的自组装

运用平均场动态密度泛函理论,对球状三嵌段共聚物在圆柱型受限空间的相行为进行了模拟研究。模拟结果表明:在不同的受限空间和表面场中,体系能够形成环绕表面的堆叠圆环、竖直的柱状相、有洞的层状相和同轴的层状相等不同于本体的有序微观结构。另外,新的序参量被定义,较好地反映了嵌段共聚物微观相分离的程度及相变情况。研究结果对实验制备新型高分子纳米材料提供了帮助。     

Admission control for a responsive distributed middleware using decision trees to model run-time parameters

The software in modern systems has become too complex to make accurate predictions about their performance under different configurations. Real-time or even responsiveness requirements cannot be met because it is not possible to perform admission control for new or changing tasks if we cannot tell how their execution affects the other tasks already running. Previously, we proposed a resource-allocation middleware that manages the execution of tasks in a complex distributed system with real-time requirements. The middleware behavior can be modeled depending on the configuration of the tasks running, so that the performance of any given configuration can be calculated. This makes it possible to have admission control in such a system, but the model requires knowledge of run-time parameters. We propose the utilization of machine-learning algorithms to obtain the model parameters, and be able to predict the system performance under any configuration, so that we can provide a full admission control mechanism for complex software systems. In this paper, we present such an admission control mechanism, we measure its accuracy in estimating the parameters of the model, and we evaluate its performance to determine its suitability for a real-time or responsive system.     

Flow control using the theory of zero sum Markov games

Considers the problem of dynamic flow control of arriving packets into an infinite buffer. The service rate may depend on the state of the system, may change in time, and is unknown to the controller. The goal of the controller is to design an efficient policy which guarantees the best performance under the worst service conditions. The cost is composed of a holding cost, a cost of rejecting customers (packets), and a cost that depends on the quality of the service. The problem is studied in the framework of zero-sum Markov games, and a value iteration algorithm is used to solve it. It is shown that there exists an optimal stationary policy (such that the decisions depend only on the actual number of customers in the queue); it is of a threshold type, and it uses randomization in at most one state     

Flow control valve for pneumatic actuators using particle excitation by PZT vibrator

This paper reports a new flow control valve for pneumatic actuators that has a lightweight and simple structure and uses particle excitation by PZT vibrator. The flow control valve in this report consists of an orifice plate which has plural orifices, PZT vibrator which is adhered on the orifice plate and iron particles. The valve is normally closed, because air flow carries the particles on to the orifice and particles seal the air flow. Because the orifice plate excitation by the PZT vibrator works to make the particles away from the orifice plate, the air flows through the orifices. It is driven at resonance mode and can be used as a variable speed controller for pneumatic actuators. The new flow control valve avoids the stopping shock of pneumatic actuators at the stroke ends while retaining the advantages of pneumatic actuators.     

Flow control in message-switched communications networks

A queueing network model is used to analyse the performance of flow-control techniques. Analytical expressions for throughput and mean end-to-end delay are derived. Numerical results show that, under isarithmic control, the total network throughput is degraded significantly when the demand from one user is increased. Throughput degradation can be avoided if an end-to-end or a two-level control is used. Of these two schemes, the two-level control gives a higher throughput to the user with increased demand. This often results in a higher total throughput. The mean end-to-end delay of the various flow-control techniques is also characterized.     

Flow control issues in a PAD

A packet assembly/disassembly (PAD) facility standard has been adopted by the CCITT to provide asynchronous terminal access to X.25-based packet networks. A PAD translates the character-by-character flow at the terminal interface into packet flow at the network interface. The paper describes the various control procedures necessary for dataflow within a PAD to prevent it from being congested. Topics discussed include character flow, packet flow, break signal handling, packet sequences, error messages, control messages, and echo buffering.     

An integrated agent-based approach for responsive control of manufacturing resources

Due to the dynamic fluctuation of customer demands in the global market, manufacturing enterprises are facing difficulties in rapidly responding to market changes. The aim of this research is to develop a system to integrate dynamic process planning and dynamic production scheduling for the purpose of increasing the responsiveness of adaptive manufacturing systems in accommodating dynamic market changes (rapidly changing demand patterns or product varieties). The concept of Multi-Agent Systems (MAS) has been adopted in this study. All of the tasks related to process planning, optimization and scheduling in this system are carried out by autonomous agents that are capable of interacting and negotiating with each other to bid for jobs and make decisions. On the one hand, this system optimizes the utilization of manufacturing resources and on the other hand, it also provides a platform where the reconfiguration of manufacturing systems can be assessed. This system has been implemented on a Java platform and a case study is provided to elaborate on this system and evaluate its implementation.     

Flow control in integrated local area networks

The modeling and optimal flow control in integrated local area networks is investigated. A generic integrated local area network with a double bus architecture, an adaptive TDMA access protocol, and a heterogenous community of users is considered. The class of control algorithms studied regulates the data flow between a pair of communicating stations. Since the data flow in the network exhibits transient behavior, dynamic optimal flow control strategies on a finite horizon are analyzed. It is shown that an adaptive window flow control mechanism maximizes the average throughput under an average system time delay constraint. The window size dynamically adapts to changes in the integrated traffic load that belongs to the other users accessing the network. Based on this analysis, a flow control mechanism is proposed for implementation that is asymptotically optimum. Simulation results showing the dynamics o of the window process and the effectiveness of the asymptotically optimum control scheme are also presented.     

A thermally actuated microvalve using paraffin composite by induction heating

Microsystem Technologies - A new induction-heating-based microvalve using paraffin composite is successfully demonstrated in this paper. The microvalve consists of a polydimethylsiloxane (PDMS)...     

Leveraging stimuli responsive hydrogels for on/off control of mixing

Microfluidic mixers are an important component in microfluidic devices. This paper presents a micromixer which can control mixing with responsive hydrogel actuators to modulate mixing between two adjacent fluids dependant on the chemistries of the fluid. This is achieved by the responsive hydrogels swelling or contracting under different stimuli, which alters the mixing between the two fluids. We present this device using standard pH responsive hydrogels for two different device designs and demonstrate altered mixing profiles based on the pH of the fluid streams. For the T-shaped device an increase in mixing efficiency from 18.3% to 34.5% is observed between the contracted and expanded hydrogel states. For the modified T-shaped device mixing efficiency in the contracted state is 25.0% while in the expanded state efficiency increases to 72.9%. This can be used as a mixer that has on/off functionality of an active mixer, based on the pH of the mixing streams, with the advantages a passive mixer offers. Other responsive hydrogel chemistries could be substituted into the device to achieve many different triggers for mixing.     

Water simulation using a responsive surface tracking for flow-type changes

The realistic simulation of fluids largely depends on a temporally coherent surface tracking method that can deal effectively with transitions between different types of flows. We model these transitions by constructing a very smooth fluid surface and a much rougher, splashy surface separately, and then blending them together in proportions that depend on the flow speed. This allows creative control of the behavior of the fluids as well as the visual results of the simulation. We overcome the well-known difficulty of obtaining smooth surfaces from Lagrangian particles by allowing them to carry normal vectors as well as signed distances from the level set surface and by introducing a new surface construction algorithm inspired by the moving least-squares method. We also implemented an adaptive form of the fluid-implicit-particle method that only places particles near visually interesting regions, which improves performance. Additionally, we introduce a novel subgrid solver based on the material point method to increase the amount of detail produced by the FLIP method. We present several examples that show visually convincing water flows.     

Flow scheduling and endpoint rate control in GridNetworks

In grid networks, distributed resources, computing or storage elements as well as scientific instruments are interconnected to support computing-intensive and data-intensive applications. To facilitate the efficient scheduling of these resources, we propose to manage the movements of massive data set between them. This paper formulates the bulk data transfer scheduling problem and presents an optimal solution to minimize the network congestion factor of a dedicated network or an isolated traffic class. The solution satisfying individual flows’ time and volume constraints can be found in polynomial time and expressed as a set of multi-interval bandwidth allocation profiles. To ensure a large-scale deployment of this approach, we propose, for the data plane, a combination of a bandwidth profile enforcement mechanism with traditional transport protocols. The paper examines several solutions for implementing such a mechanism in a Linux kernel. The experimental evaluation shows that packet pacing performed at IP level offers a simple yet valuable and TCP-compatible solution for accurate bandwidth profile enforcement at very high speed.     

Flow control for limited buffer multicast

Analyses a multiround flow control algorithm that attempts to minimize the time required to multicast a message to a group of recipients and receive responses directly from each group member. Such a flow control algorithm may be necessary because the hurry of responses to the multicast can overflow the buffer space of the process that issued the multicast. The condition that each recipient directly respond to the multicast prevents the use of reliable multicast protocols based on software combining trees or negative-acknowledgments. The flow control analysed algorithm directs the responding processes to hold their responses for some period of time, called the backoff time, before sending them to the originator. The backoff time depends on the number of recipients that respond, the originator's available buffer space and buffer service time distribution, and the number of times that the originator is willing to retransmit its message. This paper develops an approximate analysis of the service time distribution of the limited-buffer preemptive queuing process that occurs within the protocol processing layers of a multiprogrammed operating system. It then uses this model to calculate multicast backoff times. The paper reports experimental verification of the accuracy of this service time model and discusses its application to the multicast flow control problem     

Measurement of local electric field in microdevices for low-voltage electroporation of adherent cells

In this study, we present the measurement of the local electric field in a microdevice designed for electroporation of adherent cells. The microdevice mainly consists of a coverslip that has a transparent conductive layer and an insulating layer. The insulating layer has small cylindrical holes that focus the field lines to reduce the voltage required for electroporation. We estimated the local electric field at the cells by analyzing the ionic current based on a simple equivalent circuit model and investigated the correlation between the field strength and the efficiency of electroporation. We prepared various designs with matrices of electrodes with diameters ranging from 5 to 10 μm and center-to-center distances between adjacent electrodes ranging from 20 to 75 μm to perform systematic and statistical investigations. Furthermore, we discussed the efficiency of the electrode design in terms of the degree of field focusing, the applicability of optical observations, and the probability of positioning cells on the electrodes.     

High-purity control of internal thermally coupled distillation columns based on nonlinear wave model

Internal thermally coupled distillation column (ITCDIC) is a frontier of energy saving distillation researches, which is a great improvement on conventional distillation column (CDIC). However its high degree thermal coupling makes the control design a bottleneck problem, where data-driven model leads to obvious mismatch with the real plant in the high-purity control processes, and a first-principle model which is comprised of complex mass balance relations and thermally coupled relations could not be directly used as control model for the bad online computing efficiency. In the present work, wave theory is extended to the control design of ITCDIC with variable molar flow rates, where a general nonlinear wave model of ITCDIC processes based on the profile trial function of the component concentration distribution is proposed firstly; combined with the thermally coupled relations, a novel wave model based generic model controller (WGMC) of ITCDIC processes is developed. The benzene-toluene system for ITCDIC is studied as illustration, where WGMC is compared with another generic model controller based on a data-driven model (TGMC) and an internal model controller (IMC). In the servo control and regulatory control, WGMC exhibits the greatest performances. Detailed research results confirm the efficiency of the proposed wave model and the advantage of the proposed WGMC control strategy.     

Feedforward water quality control by artificial aeration of a thermally and organically polluted stream

The non-linear feedforward control theory is employed in the present work for determining the artificial aeration control policies of a thermally and/or organically polluted stream. A dispersion water quality model is used for describing the stream temperature, biochemical oxygen demand, and dissolved oxygen distributions along the stream. The artificial aeration control policy is determined such that the dissolved oxygen concentration can bo maintained at its original steady state level in the presence of thermal and/or organic waste discharges. Both step and pulse thermal and organic waste disturbances are considered. Effects of different amounts of thermal and organic waste discharges and the Peclet number on the artificial aeration rate are investigated.     

Flow velocity measurement in microchannels using temperature-dependent fluorescent dye

The size of microfluidic channels prevents the use of conventional methods for flow velocity measurement. This paper presents and evaluates a method of flow velocity measurement using a temperature dependent fluorescent dye and a microheater. The microheater applied a heat pulse to the dye flowing in a glass capillary, resulting in a plug of fluid of lower fluorescent intensity. By tracking this low intensity region, the velocity of the heat pulse travelling with the flow was determined and used to calculate average flow velocity using correlations. The method was verified by measuring a range of flow velocities in two different sized glass capillaries.     

Multi-phase current control using finite-state model-predictive control

The use of finite-state model-predictive controllers for current control of multi-phase machines is investigated. The basic setup is comprised a predictive model and an exhaustive optimizer that minimizes a predefined cost function for the next sampling period. The output of the predictive controller is a vector of gating signals to be applied to a voltage source inverter. The inverter can accommodate just a finite number of configurations and hence the name of finite-state. The use of predictive controllers, already proposed for three-phase drives, is applied here to multi-phase drives. Some implementation issues are discussed along, including the choice of the cost function, the switching frequencies applied to the inverter and the computation time needed for optimization. Simulation and experimental results are provided illustrating various aspects of the control scheme using an asymmetrical dual three-phase AC motor drive as a test bed.     

基于网络流的嵌入式互联网中流量控制与优化

针对嵌入式互联网中实时应用的受限问题,本文提出优化网络资源,平衡网络流量的解决问题思路.基于此,采用图论中的最大流最小割定理,在最小物理网络拓扑结构中构建流量控制模型,并提出一种动态离散粒子群优化算法(DDPSO). DDPSO通过优化模型中的最大流函数继而优化控制网络流量.仿真实验证明:本文提出的DDPSO算法在定义域内具有较好的收敛性;当采用分级优化策略优化控制网络流量时,本文提出的优化策略可以有效优化网络流量,充分利用网络资源,以保证实时应用要求.