基于图像块的滞留物/移取物的检测方法

背景减法是智能视频监控系统中一种常用的运动目标检测方法.本文在均值化背景更新模型的基础上提出了一种滞留物或移取物检测方法.首先,将图像划分成大小相同的图像块,以图像块为研究对象建立均值背景更新模型;然后,采用背景减法,累加前景像素点对应记分板上的积分的方法,检测目标物的出现;最后,运用边缘匹配的方法识别出前景物体是滞留物还是移取物,并且根据识别结果采用不同策略更新目标物所在的背景图像块.实验结果表明,在复杂的室外多运动物的场景中,本文方法与传统基于运动目标跟踪的方法相比较,在正确率和CPU利用情况方面表现出较好的性能.

超标量处理器中寄存器别名表恢复方法的改进研究

寄存器重命名是超标量处理器用于提升指令集并行度的重要方法,其基本实现方式是通过寄存器别名表来记录逻辑寄存器和物理寄存器的映射关系,当发生分支预测错误时需要对寄存器别名表中的内容进行恢复。针对于现有的恢复方法没有利用重命名的局部性特征,在处理器的指令窗口增加时暴露出实现代价过大的问题,提出了一种基于区间进行寄存器别名表恢复的改进型恢复方法,通过对walk方法的改造,使用区间计分板来确定需要扫描的地址范围,并精确地控制每个区间的扫描,可以大大减小资源浪费。通过对逻辑综合结果和性能进行分析,相比于检查点恢复的传统设计,这种方法使用更少的面积和功耗,达到与检查点方式恢复接近的性能,也具有更好的扩展潜力。

基于CDIO工程背景下的《单片机原理及应用》实验改革研究

以地方普通高校工科专业改革为导向,分析了地方本科高校试点改革学院《单片机原理及应用》课程的实验教学中存在的问题,借鉴CDIO工程教育理念中“做中学”经验,提出了“做中学”战略下的单片机原理及应用实验改革的新思路,文中以蓝牙技术篮球计分板为案例,以任务式教学方式对实验课程中知识点进行设计,设计了实验内容体系,实施了实验教学过程,讨论了实验成绩考核,并对传统实验教学与改革实验教学成效进行了对比。实践表明,经过实验教学改革后,学生的动手实践能力和学习积极性均得到了较大的提高,成绩优秀比率也有显著增加。

Temperature Stress Analysis of Prestressed Concrete Box Girder with Corrugated Steel Webs

To figure out the distribution of temperature gradient along the girder height of steel-concrete composite box girder, combined with the mechanical characteristics of prestressed concrete composed box girder with corrugated steel webs, the calculation formulas of cross-sectional temperature stress along the span in a simply-supported beam bridge with composite section were derived under the conditions of static equilibrium and deformation compatibility of the beam element. The methods of calculating the maximum temperature stress value were discussed when the connectors are assumed rigid or flexible. Theoretical and numerical results indicate that the method proposed shows better precision for the calculation of temperature self-stress in both the top and the bottom surfaces of the box girder. Moreover, the regularity of temperature stress distribution at different locations along the girder span is that the largest axial force of the top or the bottom plate of the box girder is located in the midspan and spreads decreasingly until zero at both supported ends, and that the greatest longitudinal shear density in steel-concrete interface appears at both supported ends and then reduces gradually to zero in the midspan.

Numerical Analysis of the Flow Field in a Sloshing Tank with a Horizontal Perforated Plate

Liquid sloshing is a type of free surface flow inside a partially filled water tank.Sloshing exerts a significant effect on the safety of liquid transport systems;in particular,it may cause large hydrodynamic loads when the frequency of the tank motion is close to the natural frequency of the tank.Perforated plates have recently been used to suppress the violent movement of liquids in a sloshing tank at resonant conditions.In this study,a numerical model based on OpenF OAM(Open Source Field Operation and Manipulation),an open source computed fluid dynamic code,is used to investigate resonant sloshing in a swaying tank with a submerged horizontal perforated plate.The numerical results of the free surface elevations are first verified using experimental data,and then the flow characteristics around the perforated plate and the fluid velocity distribution in the entire tank are examined using numerical examples.The results clearly show differences in sloshing motions under first-order and third-order resonant frequencies.This study provides a better understanding of the energy dissipation mechanism of a horizontal perforated plate in a swaying tank.

Weibull Statistics in Dielectric Strength of Oil-impregnated Pressboard under Ramped AC and DC Voltages

AC and DC breakdown tests were performed on large populations of oil-impregnated pressboard samples. The effect of voltage ramp rate on dielectric strength has been investigated. A statistical analysis of breakdown data was carried out using the Weibull distribution. The 90% confidence intervals of Weibull graphs were calculated. The study shows that dielectric strength and shape parameter change versus ramp rate. The variations are attributed to the size and number of defects. Discharges occur from the oil to the oil-pressboard interface and lead to breakdown. DC dielectric strength is larger than that corresponding to AC voltage. This is ascribed to the dissipated energy difference under the two types of field and the fatigue produced by the alternating voltage. This phenomenon is related to space charge. Under DC stress, dielectric strength is higher under negative polarity. It is assigned to the different quantities of space charge accumulated under the two polarities.

CFD Simulation of Orifice Flow in Orifice-type Liquid Distributor

In this study,a suitable CFD(computational fluid dynamics)model has been developed to investigate the influence of liquid height on the discharge coefficient of the orifice-type liquid distributors.The orifice flow in different diameters and liquid heights has been realized using the shear stress transport(SST)turbulence model and the Gamma Theta transition(GTT)model.In the ANSYS CFX software,two models are used in conjunction with an automatic wall treatment which allows for a smooth shift from a wall function(WF)to a low turbulent-Re near wall formulation(LTRW).The results of the models coupled with LTRW are closer to the experimental results compared with the models with WF,indicating that LTRW is more appropriate for the prediction of boundary layer characteristics of orifice flow.Simulation results show that the flow conditions of orifices change with the variation of liquid height.With respect to the turbulence in orifice,the SST model coupled with LTRW is recommended.However,with respect to the transition to turbulence in orifice with an increase in liquid height,the predictions of GTT model coupled with LTRW are superior to those obtained using other models.

Modeling porous structure of oil-pressboard interface and its effect on electric field distribution

The oil-pressboard insulation is a typical composite insulation system widely used in the design and manufactory of large power apparatus. The implement of oil-pressboard insulation may lead to surface electrification and discharge at the interface under certain condition. It is of significant importance to take an insight into the phenomenon occurring at the interface. Through experiment, the pressboard is found as a porous material. The interface changes abruptly from bulk pressboard to the bulk oil as a result of the porous structure. A new model is proposed which divides the interface into bulk oil region, transition region, and bulk pressboard region. The width of the transition region is decided according to the microtome figure. The effective permittivity of the transition region is calculated using a new model based on fractal theory. The model is validated and compared with previous calculation model. The effect of the existence of transition region on the electric field distribution is discussed.

规则问答

Q关于计分板的争论 在一场双打比赛中,比分来到第三盘抢七8-8,我冲到网前暴打了一记近网球。不过在球两跳之前,我碰到了绑在网柱上的记分板。但我绝对没有碰到球网和网柱。

ESTIMATION IN A SEMI-VARYING COEFFICIENT MODEL FOR PANEL DATA WITH FIXED EFFECTS

This paper considers a semi-varying coefficient model for panel data with fixed effects,proposes the profile-likelihood-based estimators for the parametric and nonparametric components,and establishes convergence rates and asymptotic normality properties for both estimators.Simulation results show that the proposed estimators behave well in finite sample cases.

Template-directed assembly of pentacene molecules on epitaxial graphene on Ru（0001）

The template-directed assembly of planar pentacene molecules on epitaxial graphene grown on Ru（0001） （G/Ru） has been investigated by means of low-temperature scanning tunneling microscopy （STM） and density functional theory （DFT） calculations. STM experiments find that pentacene adopts a highly selective and dispersed growth mode in the initial stage. By using DFT calculations including van der Waals interactions, we find that the configuration with pentacene adsorbed on face-centered cubic （fcc） regions of G/Ru is the most stable one, which accounts for the selective adsorption at low coverage. Moreover, at high coverage, we have successfully controlled the molecular assembly from amorphous, local ordering, to long-range order by optimizing the deposition rate and substrate temperature.

An analysis of Chinese urban residents＇ consumer demand employing a dynamic semi-parametric panel data model

Using data for China for the years 1991 to 2005 by province and employing the semi- parametric panel data model estimation method developed by Horowitz （2004） and Henderson et al. （2006） and Hubler＇s non-parametric generalized method of moments （GMM） estimation （2005）, this article constructs a dynamic semi-parametric panel data model and describes the dynamic changing trajectory of the effect on consumption of income disparity among urban residents. Our findings show that there is a significant ＂ratchet effect＂ in the consumption of urban residents; that income disparity among urban residents has a clear negative influence on consumption; and that the trajectory of this influence shows a roughly bimodal curve.

Structural bionic design for high-speed machine tool working table based on distribution rules of leaf veins

High-speed machine tool working table restrains the machining accuracy and machining efficiency,so lightweight design of the table is an important issue.In nature,leaf has developed a plate structure that maximizes the surface-to-volume ratio.It can be seen as a plate structure stiffened by veins.Compared with a high-speed machine tool working table,leaf veins play a role of supporting part which is similar to that of stiffening ribs,and they can provide some new design ideas for lightweight design of the table.In this paper,distribution rules of leaf veins were investigated,and a structural bionic design for the table was achieved based on regulation of leaf veins.First,statistical analysis on geometric structure of leaf veins was carried out,and four distribution rules were obtained.Then,relevant mechanical models were developed and analyzed in finite element software.Based on the results from mechanical analysis on those relevant models,the four distribution rules were translated into the design rules and a structural bionic design for the working table was achieved.Both simulation and experimental verifications were carried out,and results showed that the average displacement of the working table was reduced by about 33.9%.

Statistical analysis of vibration and sound radiation of submerged stiffened rectangular plates

In order to extend the statistical energy analysis(SEA) method to predict the vibration and sound radiation of underwater structures,we mainly analyze the effect of water loading on the key parameters in SEA and propose the approximate expressions of modal density and mean square velocity of submerged plates.With the radiation efficiency of submerged plates previously proposed by us,the modified SEA solutions of the radiated sound power and mean square velocity of submerged stiffened rectangular plates are established.Numerical examples show that the modified SEA solutions are more close to the theoretical solutions than the present SEA solutions,and reflect the mean value or trend of the theoretical solution much better,especially at lower frequencies.An experiment of point-exciting submerged plates was done in a lake.The experiment values show that for both un-stiffened and stiffened plates,the modified SEA solutions have a good agreement while the present SEA solution has considerable error,which validates the established statistical model.

Utility of Doppler ultrasonography for predicting improvement of platelet count after transjugular intrahepatic portosystemic shunt

Objective.Portal pressure gradient(PPG)after transjugular intrahepatic portosystemic shunt(TIPS)<12mmHg has been reported as the only factor predictive of increase in platelet count.As flow velocities measured on Doppler ultrasound are related to pressure gradient based on the Bernoulli equation,we used this parameter to predict increased platelet count after TIPS placement.Methods.A total of 161 consecutive patients who underwent TIPS placement entered this retrospective study.The platelet count was measured before,one week after and one month after TIPS placement.Clinically significant thrombocytopenia was defined as platelet count≤100000.Pre-and post-TIPS PPGs were measured.The velocity of blood flow in the proximal,mid and distal TIPS stent was measured using Doppler ultrasound,and the difference in the highest and lowest measured velocity was entitled flow velocity gradient(FVG),which was considered normal when≤100 cm/s.Results.In 121 patients with pre-TIPS thrombocytopenia,the mean platelet count one week and one month after TIPS placement increased 25.7×10^(3) and 35.0 × 10^(3) in 90 patients with PPG≤12mmHg(P=0.028 and P=0.015),while there was no significant change in platelet count in patients with a PPG>12mmHg(P=0.098 and P=0.075).Platelets increased significantly when FVG≤100 cm/s(n=95)vs FVG>100 cm/s(n=26)one week(37.0×10^(3) vs 11.0×10^(3);P=0.005 vs 0.07)and one month after TIPS placement(17.0×10^(3) vs 5.2×10^(3);P=0.01 vs 0.21).Conclusion.FVG>100 cm/s is not associated with increase in post-TIPS platelet count.On the other hand,findings suggestive of proper TIPS function(FVG≤100 cm/s and PPG≤12mmHg)predict a significant increase in post-TIPS platelet count.

Weighted Profile Least Squares Estimation for a Panel Data Varying-Coefficient Partially Linear Model

This paper is concerned with inference of panel data varying-coefficient partially linear models with a one-way error structure. The model is a natural extension of the well-known panel data linear model （due to Baltagi 1995） to the setting of semiparametric regressions. The authors propose a weighted profile least squares estimator （WPLSE） and a weighted local polynomial estimator （WLPE） for the parametric and nonparametric components, respectively. It is shown that the WPLSE is asymptotically more efficient than the usual profile least squares estimator （PLSE）, and that the WLPE is also asymptotically more efficient than the usual local polynomial estimator （LPE）. The latter is an interesting result. According to Ruckstuhl, Welsh and Carroll （2000） and Lin and Carroll （2000）, ignoring the correlation structure entirely and ＂pretending＂ that the data are really independent will result in more efficient estimators when estimating nonparametric regression with longitudinal or panel data. The result in this paper shows that this is not true when the design points of the nonparametric component have a closeness property within groups. The asymptotic properties of the proposed weighted estimators are derived. In addition, a block bootstrap test is proposed for the goodness of fit of models, which can accommodate the correlations within groups illustrate the finite sample performances of the Some simulation studies are conducted to proposed procedures.