音频信号测量技术研究

该文详细地阐述音频激励信号的产生、信号电平测量、失真度测量的实现方法。重点论述了激励信号的产生、电平测量方案的选择以及失真度测量设计等。     

中厚板轧机二级过程控制系统模型的研究与优化

舞钢公司第二轧钢厂轧机二级过程控制系统是新宽厚板生产线的重要组成部分。结合实际生产过程,对该二级系统的温度模型、轧制力模型、扭矩模型以及双机架轧制匹配模型等进行了参数优化调整,进一步提高了系统模型预测数据的准确性,保证双机架轧制模式的稳定运行。     

Approximating the Poisson Scan and (λ–σ) acoustic detection model with a Random Search formula

In this study, we develop a MATLAB simulation of area search with acoustic sensors modeled by the Poisson Scan model and the Lambda–Sigma (λ–σ) model. Detection time results are compared to those given by the much simpler Random Search formula. Random Search was found to closely approximate the more complex models if detection range was selected correctly. Guidelines for selecting the Random Search detection range were developed.     

Large-scale App privacy governance

Recently, the problem of mobile applications (Apps) leaking users’ private information has aroused wide concern. As the number of Apps continuously increases, effective large-scale App governance is a major challenge. Currently, the government mainly filters out Apps with potential privacy problems manually. Such approach is inefficient with limited searching scope. In this regard, we propose a quantitative method to filter out problematic Apps on a large scale. We introduce Privacy Level (P-Level) to measure an App’s probability of leaking privacy. P-Level is calculated on the basis of Permission-based Privacy Value (P-Privacy) and Usage-based Privacy Value (U-Privacy). The former considers App permission setting, whereas the latter considers App usage. We first illustrate the privacy value model and computation results of both values based on real-world dataset. Subsequently, we introduce the P-Level computing model. We also define the P-Level computed on our dataset as the PL standard. We analyze the distribution of average usage and number of Apps under the levels given in the PL standard, which may provoke insights into the large-scale App governance. Through P-Privacy, U-Privacy, and P-Level, potentially problematic Apps can be filtered out efficiently, thereby making up for the shortcoming of being manual.     

Some Multivariate Tests of Independence Based on Ranks of Nearest Neighbors

Several parametric and nonparametric tests of independence between two random vectors are available in the literature. But, many of them perform poorly for high-dimensional data and are not applicable when the dimension exceeds the sample size. In this article, we propose some tests based on ranks of nearest neighbors, which can be conveniently used in high dimension, low sample size situations. Several simulated and real datasets are analyzed to show the utility of the proposed tests. Codes for implementation of the proposed tests are available as supplementary materials.     

On testing the equivalence of treatments using the measure of range

A studentized range test is proposed to test the hypothesis of average equivalence of treatments in terms of the distance between means against the alternative hypothesis of inequivalence. A least favorable configuration (LFC) of means to guarantee the maximum level at a null hypothesis and a LFC of means to guarantee the minimum power at an alternative hypothesis are obtained. The level and power of the test are fully independent of the unknown means and variances. For a given level and a given power, the critical value and the required sample size for an experiment can be simultaneously determined, and the tables of critical values and sample sizes are provided for practitioners. A real numerical example to demonstrate the use of the test procedure is provided. In situations where the common population variance is unknown and the equivalence is the actual distance between means without standardization, a two-stage sampling procedure can be employed to find these solutions. It proves to be a quite feasible solution for practitioners.     

The role of eye movements in the size-speed illusion of approaching trains

Recent research on the perceived speed of large moving objects, compared to smaller moving objects, has revealed the presence of a size-speed illusion. This illusion, where a large object seems to be moving more slowly than a small object travelling at the same speed may account for collisions between motor cars and trains at level crossings, which is a serious safety issue in New Zealand and worldwide. One possible reason for the perceived size-speed difference may be related to the movement of our eyes when we track moving vehicles. In order to investigate this, we tested observers’ relative speed perception of moving objects (both abstract and more detailed objects) moving in depth towards the observer, presented on a computer display and eye movements recorded with an eyetracker. Experiment 1 confirmed first the size-speed illusion when the observers were situated further away (18, 36 m) from the simulated rail crossing or intersection. It also revealed that the eye movement behaviour of our participants was different when they judged the speeds of the small and large objects; eye fixations were localised around the visual centroid of longer objects and hence were further from the front of the moving large objects than the smaller ones. Experiment 2 found that manipulating eye movements could reduce the magnitude of the illusion. When observers tracked targets (dots) that were placed at corresponding locations at the front of the small object and the long object respectively, they perceived the speeds of the two objects as equal. When target dots were placed closer to the visual centroid, observers perceived the larger object to be moving slower. These results demonstrate that there is a close relationship between eye movement behaviour and our perceived judgement of an approaching train's speed.     

非牛顿流体非等温充模过程的Level Set方法模拟(英文)

A non-isothermal injection molding process for a non-Newtonian viscous pseudoplastic fluid is simulated. A conservative interface capturing technique and the flow field solving method are coupled to perform a dynamic simulation. The validity of the numerical method is verified by a benchmark problem. The melt interface evolution versus time is captured and the physical quantities such as temperature, velocity and pressure at each time step are obtained with corresponding analysis. A “frozen skin” layer with the thickness increasing versus time during the injection process is found. The fact that the “frozen skin” layer can be reduced by increasing the injection velocity is numerically verified. The fountain flow phenomenon near the melt interface is also captured. Moreover, comparisons with the non-isothermal Newtonian case show that the curvatures of the interface arcs and the pressure con-tours near the horizontal mid-line of the cavity for the non-Newtonian pseudoplastic case is larger than that for the Newtonian case. The velocity profiles are different at different positions for the non-Newtonian pseudoplastic case, while in the case of Newtonian flow the velocity profiles are parabolic and almost the same at different positions.     

云环境下基于服务等级协议的信任评估模型

针对用户在交互过程中对云服务商缺乏信任的问题,提出了一个基于服务等级协议(SLA)的云计算信任模型。在该模型中,云服务商在向服务中心--可信的第三方平台注册时,首先提交自身的实力评估报告,说明其实力、运营、技术及提供的服务属性等,服务中心根据相关的评价标准对该云服务商进行评估,得到系统信任;其次把系统信任引入到传统的声誉机制中,把系统信任、直接信任和间接信任作为评估一个云服务提供商的三个重要因素,并计算出云服务商的综合信任度;最后用户根据云服务商提供的服务和综合信任度与其进行SLA协商,确定最终交互对象,屏蔽掉不诚实或信誉较低的云服务商。实验结果表明,在基于服务等级协议的信任模型中,由于引入了系统信任,云服务商综合信誉的获得更全面准确、有效地防止了云服务商的不诚信行为,提高了交互的成功率。     

分簇VLIW DSP上支持单双字模式选择的SIMD编译优化

BWDSP100是一款采用超长指令字(VLIW)和单指令多数据流(SIMD)架构的针对高性能计算领域而设计的32位静态标量数字信号处理器,其指令级并行(ILP)主要是通过其特殊的分簇体系结构和SIMD指令来实现,然而现有的编译框架无法对这些特殊的SIMD指令提供支持。由于BWDSP100拥有丰富的SIMD向量化资源,且其所运用的雷达数字信号处理领域对程序的性能要求极高,因此针对BWDSP100结构的特点,在传统Open64编译器中SIMD编译优化框架的基础上提出并实现了一种支持单双字模式选择的SIMD编译优化算法,通过该算法可以显著提高一些在DSP上有着广泛运用计算密集型程序的性能。实验结果表明,与优化前相比,该算法方案在BWDSP编译器上的实现能够平均取得5.66的加速比。