CP-PMTT:一个基于控制流模式的过程模型转换工具

目前大多数过程模型转换方法采用基于元类映射的转换规则,鉴于因不同过程建模语言在建模符号和语法约束上的差异,而使基于元类映射的转换规则在应对过程模型转换时存在明显局限,提出一种基于控制流模式的过程模型转换框架,转换框架包括一个支持用户自定义控制流模式的控制流模式定义框架,控制流模式定义框架是转换框架的转换核心。通过建立源语言、目标语言和转换核心的映射关系,生成源语言到目标语言的转换规则。基于上述框架实现了一个过程模型转换工具。通过业务流程建模标记到另一种工作流语言的转换场景,对转换工具进行了验证。

过程模型中控制流反模式的定义和检测方法

提出一种过程模型中控制流反模式的定义和检测方法,抽取不同过程模型中的控制流结构并将其规约为语言无关的过程结构树,基于不同控制流反模式的CAPDL定义,在过程结构树上查找与之对应的控制流反模式。该方法既支持不同的过程建模语言,也允许用户自定义控制流反模式。基于215个实际BPMN过程模型的反模式检测试验表明,该方法可以有效地检测用户自定义的控制流反模式,与已有方法相比,该方法极大地提高了反模式检测的检测效率。

一种基于双模式虚拟机的多态Shellcode检测方法

近年来,Shellcode攻击通常利用多态技术进行自我加密来绕过网络层设备的检测,而现有检测方法无法区分多态Shellcode与加壳保护代码.提出了一种基于双模式虚拟机的多态Shellcode检测方法,该方法改进了现有的GetPC定位机制,实现了Shellcode的初步定位,通过IA-32指令识别对网络流量的进行进一步过滤,利用有限自动机及其判别条件实现虚拟机控制流模式和数据流模式之间的切换,并通过结合现有的特征匹配技术实现对多层加密的多态Shellcode的检测.实验结果表明,针对大量真实的网络数据,该方法在保证高检测召回率的同时,能够实现对多态Shellcode与加壳保护软件的有效区分,避免了对正常流量的误报行为,并且时间开销介于静态分析与动态模拟之间,为网络层检测多态Shellcode提供了一种有效方法.

Analysis and design of DSP-based dual-loop controlled UPS inverters

This paper presents a novel digital dual-loop control scheme of the PWM(PUlse width modulate)inverter. Deadbeat control technique are employed to enhance the performance. Half switching period delayed sampling and control timing strategy is used to improve the system dynamic response. Simulation and experimental results presented in the paper verified the validity of the proposed control scheme.

Improving Residence Time Distribution in Glass Melting Tanks Using Additionally Generated Lorentz Forces

Continuous glass melting tanks represent thermo-chemical reactors with very complex flow patterns. Controlling the flow patterns within the glass melting tanks with the aim of improving their performance is one of the glass industry primary challenges. The tank performance is basically determined by the RTD （residence time distribution） of the glass melt, which directly impacts the glass quality and energy distribution. In the present work, numerical simulations are carried out on the electromagnetic flow control to investigate how well the flow can be controlled by externally generated electromagnetic （Lorenz） forces that are added to the glass melt. Furthermore, the melting tanks are equipped with supplementary electric heating systems called ＂electric boosters＂. The desired result would be an improved RTD. The electromagnetic flow control is called ＂electromagnetic boosting＂ and can be realized by exposing the glass bath to an external magnetic field generating Lorentz forces on the glass melt as an additional flow component. The numerical simulations of the present study require coupled calculations of electromagnetic field, flow field, and temperature field, because the material properties of glass melt are strongly temperature-dependent. The computational results show that electromagnetic boosting is an excellent way of improving the RTD in glass melting tanks, ultimately resulting in better glass quality and increased productivity. Of course, the glass industry is highly interested in achieving exactly this result.

Loop Compensator Design for DCM Peak-Current-Mode Control DC-DC Buckboost Converter

An analytic closed-form based loop compensator for direct current-direct current （DC-DC） buckboost converter in discontinuous conduction with peak current-mode control is proposed to increase efficiency of the desired process through systemization. As a result, the process saves a lot of computation time that can be translated into design cost savings. Finally, the output voltage regulation in the presence of audio susceptibility and output impedance is shown for verifying.

Constant Ripple Current Control for Switching DC-DC Converter

The adapted DC-DC converters should be smaller in size and have a small output current ripple to meet the increasing demand for low voltages with high performance and high density micro processors for several microelectronic load applications. This paper proposes a DC-DC converter using variable on-time and variable switching frequency control enhanced constant ripple current control and reduced magnetic components. The proposed converter is realized by making the turn-offtime proportional to the on-time of the converter, according to the input and output voltage, thereby reducing the corresponding current ripple on output voltage in the continuous conduction mode. A Buck DC-DC converter using the proposed control strategy is analyzed in detail, along with some experimental results to show the performance and effectiveness of this converter.

Modelling and Predictive Control of a Buck-Boost DC-DC Converter

A predictive current control algorithm for the Buck-Boost DC-DC converter is presented in this paper. The continuous time model of the system is properly introduced, then, by imposing a proper PWM modulation pattern, its discrete time model is achieved. This last one is successfully employed in determining the steady state locus of the Buck-Boost converter, both in CCM （continuous conduction mode） and DCM （discontinuous conduction mode）. A novel continuous time equivalent circuit of the converter is introduced too, with the aim of determining a ripple free representation of the state variables of the system, over both transient and steady state operation. Then, a predictive current control algorithm, suitable in both CCM and DCM, is developed and properly checked by means of computer simulations. The corresponding results have highlighted the effectiveness of the proposed modelling and of the predictive control algorithm, both in CCM and DCM.

Experimental investigation on control of vortex shedding mode of a circular cylinder using synthetic jets placed at stagnation points

Control of flow around a circular cylinder by synthetic jets has been experimentally investigated in a water tunnel with particle image velocimetry(PIV) technique.The synthetic jets are positioned at both the front and rear stagnation points.With power spectrum analysis,proper orthogonal decomposition(POD) method and other techniques for data processing,particular attention is paid to the control of vortical structures around the circular cylinder,in which the excitation frequency f e is one to three times of the natural frequency f0 and the cylinder Reynolds number and the excitation amplitude are fixed.The influenced-scope of the synthetic jet enlarges as the excitation frequency increases,and thus the synthetic jet dominates the global flow field gradually.For the natural case and the control case at fe/f0=1,the distributions of the first two POD modes and the power spectra for their POD coefficients all exhibit the characteristics of the natural shedding with antisymmetric mode.For fe/f0=2 and fe/f0=3,the variations in the third and fourth POD modes and the corresponding power spectra indicate that the wake vortex shedding mode changes and the dominant frequency becomes the excitation frequency.For fe/f0=2,the wake vortex sheds downstream with either the antisymmetric or the symmetric mode;for fe/f0=3,the synthetic jet vortex pair interacts with the near wake shear layers from both sides to induce a pair of the symmetric wake vortices,which is gradually converted into an antisymmetric mode when shedding downstream.

On the feasibility and efficacy of control traffic protection in software-defined networks

Software Defined Networking （SDN） is an emerging networking paradigm that assumes a logically centralized control plane separated from the data plane. Despite all its advantages, separating the control and data planes introduces new challenges regarding resilient communications between the two. That is, disconnec- tions between switches and their controllers could result in substantial packet loss and performance degradation. This paper addresses this challenge by studying the issue of control traffic protection in SDNs with arbitrary numbers of controllers. Specifically, we propose a control traffic protection scheme that combines both local rerouting and constrained reverse path forwarding protections, through which switches can locally react to fail- ures and redirect the control traffic using standby backup forwarding options. Our goal is then to find a set of primary routes for control traffic, called protected control network, where as many switches as possible can benefit from the proposed protection scheme. We formulate the protected control network problem, prove its NP-hardness, and develop an algorithm that reconciles proteetability and performance （e.g., switch-to-control latency）. Through extensive simulations based on real topologies, we show that our approach significantly im- proves protectability of control traffic. The results should help further the process of deploying SDN in real-world networks.

Control of the Asymmetric Flow in Rocket Nozzles

In some rocket nozzle flows, the existence of the transition from FSS to RSS and the occurrence of asymmetric flow are known in previous researches. As a result, the transition causes excessive side-loads that may damage the nozzle. Thus, it is important to investigate the method in order to control the asymmetric flow separation. In the present study, the relationship between the asymmetric separation and the rate of change of the pressure ratio with time was investigated from the point of view of the transition from FSS to RSS in the supersonic nozzle experimentally. Further, change of the flow separation by using step and cavity, and the possibility of the control was demonstrated. As a result, it was shown that the method using a cavity was effective for the control of the separation pattern.

Entrance Effects in Microchannel Gas Flow

Motivation of this work has its origin in the boundary layer control for aeronautics and turbomachinery. For thatpurpose boundary layer can be modified by perforated plates with holes of specific sizes. The questions whichrise in such configuration are related to the existence of optimal size of the holes and the influence of microscalephenomena on the global flow patterns. This paper concentrates on the issue of the entrance effects on the microchannelflow. It is shown that mass flow rate is only insignificantly influenced by slip effects. Global parameterssuch as pressure difference and geometrical shape in more pronounced way alter flow behavior. In this paper weconcentrate on the numerical investigation of the microchannel flow for Kn < 0.01 and Re < 500. The channellength is finite. Hence, entrance and outlet effects on microchannel flow can be studied.

On-chip boost regulator with projected off- and on-time control

The boost type power supplies are widely used in portable consumer electronics to step up the input voltage to adapt for the high voltage applications like light-emitting diode(LED) driving and liquid crystal display(LCD) biasing.In these applications,a regulator with small volume,fewer external components and high efficiency is highly desired.This paper proposes a projected off-and on-time boost control scheme,based on which a monolithic IC with an on-chip VDMOS with 0.2 Ω on-state resistance RDS-ON was implemented in 1.5 μm bipolar-CMOS-DMOS(BCD) process.A 12 V,0.3 A boost regulator prototype is presented as well.With projected off-time and modulated on-time in continuous conduction mode(CCM),a quasi fixed frequency,which is preferred for ripple control,is realized.With projected on-time and modulated off-time in discontinuous conduction mode(DCM),pulse frequency modulation(PFM) operation,which is beneficial to light load efficiency improvement,is achieved without extra control circuitry.Measurement results show that an efficiency of 3% higher than that of a conventional method under 0.5 W output is achieved while a step load transient response comparable to that of current mode control is maintained as well.