Performance analysis of a threshold-based discrete-time queue using maximum entropy

The provision of guaranteed QoS for various Internet traffic types has become a challenging problem for researchers. New Internet applications, mostly multimedia-based, require differentiated treatments under certain QoS constraints. Due to a rapid increase in these new services, Internet routers are facing serious traffic congestion problems. This paper presents an approximate analytical performance model in a discrete-time queue, based on closed form expressions using queue threshold, to control the congestion caused by the bursty Internet traffic. The methodology of maximum entropy (ME) has been used to characterize closed form expressions for the state and blocking probabilities. A discrete-time GGeo/GGeo/1/{N₁, N₂} censored queue with finite capacity, N₂, external compound Bernoulli traffic process and generalised geometric transmission times under a first come first serve (FCFS) rule and arrival first (AF) buffer management policy has been used for the solution process. To satisfy the low delay along with high throughput, a threshold, N₁, has been incorporated to slow the arrival process from mean arrival rate λ₁ to λ₂ once the instantaneous queue length has been reached, otherwise the source operates normally. This creates an implicit feedback from the queue to the arrival process. The system can be potentially used as a model for congestion control based on the Random Early Detection (RED) mechanism. Typical numerical experiments have been included to show the credibility of ME solution against simulation for various performance measures and to demonstrate the performance evaluation of the proposed analytical model.     

响应面法微波降解EGCG制备EGC研究

目的 为探究微波降解EGCG方法制备EGC的效果,以EGC得率最大化为目标,探究微波降解的最佳工艺参数,并建立反映各参数间关系的二次多元方程模型。方法 本研究采用EGCG溶液为原料,运用微波加热降解EGCG制备EGC,通过梯度设置EGCG浓度、微波时长、微波强度三个工艺参数,进行单因素实验、响应面分析及最佳工艺组合验证实验,优化确定EGCG微波降解制备EGC的最佳工艺参数。结果 综合单因素实验及响应面分析,得到的最佳微波降解参数为：EGCG浓度5mg/ml、微波时长3.5min、微波强度为400W,且利用响应面法建立了EGC得率(Y)与EGCG浓度(A)、微波时长(B)、微波强度(C)的二次多元方程模型：Y=59.52+8.38*A+5.38*B+3.53*C-4.04*AB+6.92*AC-9.19*BC-9.99A2⁺0.0786*B2^-15.36*C2^,模型中,EGC得率最高可达62.08%。对最佳微波降解工艺参数进行验证实验,EGC得率为63.40%,与模型预测值接近。结论 运用微波降解EGCG制备EGC具有操作简单,可行性高的优势,且EGC得率稳定性高。     

Adaptive fault-tolerant control for a class of flexible air-breathing hypersonic vehicles

In this paper, a novel adaptive fault-tolerant control (FTC) scheme is proposed for a class of flexible air-breathing hypersonic vehicles with unknown inertial and aerodynamic parameters and even input constraints. The fault model under consideration covers the case that all actuators suffer from unknown time-varying faults. In the controller design and stability analysis, we introduce new Lyapunov functions, some differentiable auxiliary functions, a bound estimation approach, and a Nussbaum function, which help us successfully circumvent the obstacle caused by the faults, input constraints, and flexible modes. In addition to higher reliability, the proposed scheme is able to ensure that all closed-loop signals are globally uniformly bounded and to steer the tracking errors of altitude and velocity into predefined arbitrarily small residual sets. As a result, the tracking accuracy can be designated in advance. Simulation results illustrate the effectiveness of the proposed scheme.     

Testing Transverse Sensitivity of Linear Single-Axis Pendulous Accelerometer with Double Turntable Centrifuge

Current ISO standard methods for testing transverse sensitivity of accelerometers are vibration-based. They have difficulties in producing low-frequency vibration for various reasons. This paper introduces a double turntable centrifuge (DTC) to test the accelerometer transverse sensitivity at low frequencies (from 0.01 to 10 Hz). The proposed method can avoid limitations of traditional vibration-based schemes for transverse sensitivity test. In this paper, a theoretical analysis of the method is followed by a presentation of the experimental set-up, and the measurement procedure of a linear single-axis pendulous accelerometer. According to the theoretical analysis and experimental results, it is practicable to test the low-frequency transverse sensitivity with a DTC. The method proposed here can test accelerometer transverse sensitivity at low-frequency with large amplitudes (up to 700 m/s²), and directly measure the angle of the transverse sensitivity with high resolution. It can be a supplement to the standard methods for testing accelerometer transverse sensitivity at low-frequency.     

加强计量信息化建设,提高企业计量管理水平

网络化的计量管理信息系统在技术上的实用性和维护性上面都有其可靠性,对计量管理工作采用信息化管理可以真正实现完全意义上的信息共享,使我们管理的计量装置、计量器具准确可靠的运行。     

新一代液晶显示系统设计与实现

随着时代的演进和科技的进步,液晶显示已经在现代科技产品中得到广泛应用,为了提高液晶显示系统在带有电容触摸技术的现代电子产品中开发与应用,文章中采用新一代8位STM8S208系列MCU和ET-12864F液晶显示模块,设计了一种新型的液晶显示系统;同时介绍了STM8S208单片机的优越性和ET-12864F液晶显示模块的具体操作方法,并给出了单片机STM8S208与液晶显示模块ET-12864F构建的硬件接口电路和程序设计;经实践应用,该液晶显示系统应用开发成本低,效率高具有较好的项目应用参考价值。     

基于二阶梯度的图像增强算法研究

针对PCB图像的特点对图像进行增强处理,使得图像的边缘更加突出,灰度的对比度增加,同时滤除靠近边缘的噪声,为后续图像分割时更有效的选取阈值打下良好基础。使用二阶梯度算子获得图像的增强效果,实验表明,不仅解决了边缘附近噪声去除问题,而且有效地突出了边缘信息,图像的黑白对比分明,尤其是目标图像靠近边缘部分灰度值明显高于其他的非边缘区域。     

Synchronization of complex dynamical networks under recoverable attacks

In this paper, the synchronization of complex dynamical networks (CDNs) under ‘successful’ but recoverable attacks is studied by utilizing the framework of switching systems. ‘Successful’ attacks refer to a class of attacks that break a network into a group of isolated clusters. Recoverable attacks refer to a class of attacks that the network can recover from after a period of time. To facilitate the investigation of the synchronization of a CDN under ‘successful’ but recoverable attacks, the attack frequency and the average recovering time are introduced. By using a piecewise Lyapunov function, the upper bounds of the attack frequency and the average recovering time are obtained to ensure that the whole network can achieve global synchronization under attacks.     

嵌入式系统芯片的软硬件协同仿真环境设计

针对嵌入式系统芯片SoC开发验证阶段的需求,介绍了一种通用的SoC软硬件协同仿真平台。软件仿真由C／C＋＋和汇编语言编写,硬件仿真基于VMM验证方法学所搭建,SoC设计代码由RTL代码编写而成。将SoC设计代码中的ARM由DSM模型替代,通过VCS编译器将软硬件协同起来进行信息交互,实现一种速度快、真实性高、调试方便的...