Cross Point Assignment Algorithm Under Consideration of Very Long Nets

A cross point assignment algorithm is proposed under consideration of very long nets (LCPA).It is to consider not only the cost of connection between cross points and pins and the exclusive cost among cross points on the boundary of a global routing cell,but also the cost of displacement among cross points of the same net.The experiment results show that the quality and speed in the following detailed routing are improved obviously,especially for very long nets.

Cross Point Assignment Algorithm with Crosstalk Constraint

An algorithm to resolve the coupling effect problem is proposed during the cross point assignment (CPA) stage.In the algorithm,the priority queue concept and the rip-up and reroute strategy are combined to control crosstalk noise caused by interconnect coupling capacitance.First,the nets are arranged into different priority queues according to their weighted sum of their length and criticality.Then,the CPA problem for one queue of nets is translated into a linear assignment problem.After the assignment of one queue of nets,a post-CPA checking routine is performed to check and rip up the net pairs which violate the crosstalk noise constraint and then push them into the next queue to be reassigned.The algorithm is tested by a set of bench mark examples,and the experimental results are promising...

Crossing point temperature of coal

A further understanding of the self-heating of coal was obtained by investigating the crossing point temperature（CPT） of different ranks of coal.The tests were carried out using a self-designed experimental system for coal self-heating.50 g（±0.01 g） of coal particles ranging from 0.18 mm to 0.38 mm in size were put into a pure copper reaction vessel attached to the center of a temperature programmed enclosure.The temperature program increased the temperature at a rate of 0.8℃/min.Dry air was permitted to flow into the coal reaction vessel at different rates.The surrounding temperature and the coal temperature were monitored by a temperature logger.The results indicate that CPT is affected by coal rank,moisture,sulfur, and the experimental conditions.Higher ranked coals show higher CPT values.A high moisture content causes a delay phenomenon during the self-heating of the coal.Drying at 40℃decreases the effects of moisture.The reactivity of sulfur components in the coal is low under dry and low-temperature conditions. These components form a film that covers the coal surface and slightly inhibits the self-heating of the coal. The flow rate of dry air,and the heating rate of the surroundings,also affect the self-heating of the coal.The most appropriate experimental conditions for coal samples of a given weight and particle size were determined through contrastive analysis.Based on this analysis we propose that CPTs be determined under the same,or nearly the same conditions,for evaluation of the spontaneous combustion of coal.

Computation of the locus crossing point location of MC circuit

In this paper, the crossing point property of the i-v hysteresis curve in a memristor-capacitor （MC） circuit is analyzed. First, the ideal passive memristor on the crossing point property of i-v hysteresis curve is studied. Based on the analysis, the analytical derivation with respect to the crossing point location of MC circuit is given. Then the example of MC with linear memristance-versus-charge state map is demonstrated to discuss the drift property of cross-point location, caused by the frequency and capacitance value.

Regular-Singular Crossings on Nonlinear Systems with Turning Point

We consider in this paper the boundary value problems of nonlinear systems the form εY″=F(t,Y,Y′,ε), -1<t<1, Y(-1,ε)=A(ε), Y(1,ε)=B(ε). Supoosing some or all of the components of F , that is, f i satisfy 2 f y′ 2 i t =0 =0, we say that F possesses a generalized turning point at t =0. Our goal is to give sufficient conditions for the existence of solution of the problems and to study the asymptotic behavior of the solution when F possesses a generalized turning point at t =0. We mainly discuss regular singular crossings.

The asymptotic relation between the first crossing point and the last exit time of Gaussian order statistics sequences

In this paper,we study the asymptotic relation between the first crossing point and the last exit time for Gaussian order statistics which are generated by stationary weakly and strongly dependent Gaussian sequences.It is shown that the first crossing point and the last exit time are asymptotically independent and dependent for weakly and strongly dependent cases,respectively.The asymptotic relations between the first crossing point and the last exit time for stationary weakly and strongly dependent Gaussian sequences are also obtained.

Cross-Correlation Detection of Point Sources in the WMAP First Year Data

We apply a Cross-Correlation （CC） method developed previously for detecting gamma-ray point sources to the WMAP first year data by using the Point-Spread Function of WMAP and obtain a full sky CC coefficient map. We find that the CC method is a powerful tool to examine the WMAP foreground residuals which can be further cleaned accord- ingly. Evident foreground signals are found in the WMAP foreground cleaned maps and the Tegmark cleaned map. In this process 101 point sources are detected, and 26 of them are new sources additional to the originally listed WMAP 208 sources. We estimate the flux of these new sources and verify them by another method. As a result, a revised mask file based on the WMAP first year data is produced by including these new sources.

An analytical model for the prediction of cross-section profile and mean roll radius in alloy bar rolling

In a round-oval-round pass rolling sequence, the cross-section profile of an outgoing workpiece was predicted first after getting the maximum spread. The concept ＂critical point on the contact boundary＂ was proposed and the coordinates of the critical point were solved. The equivalent contact section area was represented and the mean roll radius was determined. The validity of this model was examined by alloy bar rolling experiment and rigid-plastic FEM simulation. Compared with the existing models, the mean roll radius obtained by this model is similar to experiment data.

融合多注意力机制与PointRCNN的三维点云目标检测

针对三维不规则的点云格式和密度不均匀的问题,提出了一种融合多注意力机制与PointRCNN网络用于三维点云目标检测。本实验主要对PointRCNN两阶段网络分别进行改进,首先,把通道注意力与空间注意力机制串行通过调节输入到第一阶段各网络层的分布,批量归一化进一步快速识别三维特征;其次,引入交叉位置注意力机制到第二阶段网络为了避免交叉路径出现位置偏差,从而进一步精细化三维目标位置以进行特征提取。在KITTI数据集上实验结果表明:相比于PointRCNN检测网络,改进的网络在小汽车和行人测试上平均均值精度(mAP)分别提高了1.2%、1.9%。因此改进的方法在解决了点云格式不规则和密度不均匀问题的同时还保证了检测精度。

Surveying method of points on axis of cyllindrical pipe

To determine axes line of pipe or structural building which has a round normal section is recurrent in actual building works. The verticality measurement of chimney, TV tower and the deflection measurement of pipe are important to find out the deviation from design in construction, installation and completion. This pa- per discussed the measurement technique and data processing method for axes line of round normal section based on reflectorless distance measure. Simulation and practical results showed its feasibility and high effi- ciency.

Review of studies on target acquisition in virtual reality based on the crossing paradigm

Crossing is a fundamental paradigm for target selection in human-computer interaction systems.This paradigm was first introduced to virtual reality(VR)interactions by Tu et al.,who investigated its performance in comparison to pointing,and concluded that crossing is generally no less effective than pointing and has unique advantages.However,owing to the characteristics of VR interactions,there are still many factors to consider when applying crossing to a VR environment.Thus,this review summarizes the main techniques for object selection in VR and crossing-related studies.Then,factors that may affect crossing interactions are analyzed from the perspectives of the input space and visual space.The aim of this study is to provide a reference for future studies on target selection based on the crossing paradigm in virtual reality.

一种基于Cross-Validation的盲图像恢复方法

图像盲复原所面临的主要问题是可利用的信息不足,目前已有的图像盲复原算法一般都是有先验知识,如非负和有限支持域的限制。但在实际中目标的支持域是未知的。文中介绍了CV(cross validation)的基本原理,给出了一种基于CV原理的支持域确定方法的详细步骤;并针对计算大的问题提出了一定的改进。最后给出了实验结果,证明CV确定支持域的方法对于图像盲复原是有一定价值的。

Stereo Matching of Planar Curves Composed of Time Stamped Points

Matching features such as curve segments in stereo images play a very important role in scene recomtruction. In this paper, a stereo matching algorithm for the trajectories composed of time stamped points is proposed. Based on time stamped points, planar curve match measurements are given first, such as time constraint, cross-ratio invariant constraint and eplpolar geometry constraint; then, a trajectory matching method is proposed based on epipolar geometry constraint and cross-ratio invariant constraint. In order to match the planar curve segments projected by perspective projection system, the curve start time and end time are selected first to prepare match candidates. Then, the epipolar equation is used to discard the unmatched curve segment candidates. At last, a cross ratio invariant constxaint is used to find the most matched curve segments. If their match measurement is higher than the specialized threshold, a candidate with the least cross ratio difference is then selected as the match result; otherwise, no match is found. Unlike the conventional planar curve segments matching algorithm, this paper presents a weakly calibrated binocular stereo vision system which is based on wide baseline. The stamped points are obtained by targets detecting method of flying objects from image sequences. Due to wide baseline, there must exist the projection not in epipolar monotonic order or the curve segments located in very short distance and keeping the epipolar monotonic order. By using the method mentioned above, experiments are made to match planar curve segments not only in epipolar monotonic order but also not in epipolar monotonic order. The results show that the performance of our curve matching algorithm is effective for matching the arc-like planar trajectories composed of time stamped points.

煤自燃程序升温实验及其在实验教学中的应用

该文利用程序升温实验系统,对三种氧气浓度(20.9%、10%和7%)所代表的采空区散热带、氧化带、窒息带进行了煤样自燃发火实验,采集了不同温度阶段的气体产物,分析了温度及氧气浓度对气体产物浓度的影响,并对指标气体进行了详细分类和评估。实验结果表明:交叉点温度CPT随着氧气浓度的升高而降低,干空气的交叉点温度为144.6℃,由经验关系计算得到的CPT值与实验数据相差仅6.08%;氧气浓度越高,临界温度越低,所产生的气体浓度越高;CO气体在不同的含氧环境下都是主要的氧化产物,可作为判断煤自燃发火的主要指标,C_(2)H_(4)和C_(3)H_(6)的产生表示煤体进入加速氧化状态,可作为判断煤自燃发火的辅助指标。

图像语义特征引导与点云跨模态融合的三维目标检测方法

受到场景的复杂性和目标尺度变化、遮挡等影响,三维目标检测仍面临着诸多挑战.虽然跨模态特征融合图像和激光点云信息能够有效地提升三维目标检测性能,但在融合效果和检测性能上仍有待提升,为此,提出图像语义特征引导与点云跨模态融合的三维目标检测方法.首先设计图像语义特征学习网络,采用双分支自注意力并行计算方式,实现全局语义特征增强,降低目标错误分类;然后提出图像语义特征引导的局部融合模块,采用元素级数据拼接将检索的图像局部语义特征引导融合点云数据,更好地解决跨模态信息融合存在的语义对齐问题;提出多尺度再融合网络,设计融合特征与激光雷达点云交互模块,学习融合特征和不同分辨率特征间的再融合,提高网络的检测性能;最后采用4种任务损失实现anchor-free的三维目标检测.在KITTI和nuScenes数据集中与其他方法进行对比,针对三维目标检测准确率达87.15%,并且实验结果表明,文中方法优于对比方法,具有更优的三维检测性能.

基于多通道交叉注意力融合的三维目标检测算法

针对现有单阶段三维目标检测算法对点云下采样特征利用方式单一、特征对长程上下文信息的聚合程度无法满足算法性能提升需求的问题,本文提出了基于多通道交叉注意力融合的单阶段三维目标检测算法。首先,设计通道交叉注意力模块用于融合下采样特征,可基于交叉注意力机制在通道层面上增强多尺度特征对不同感受野下长程空间信息的表达能力;然后,提出级联特征激励模块,结合原始下采样特征对通道交叉注意力加权特征进行级联激励,提升算法对关键空间特征的学习能力。在公共自动驾驶数据集KITTI上进行了大量实验并与主流算法对比,本文算法作为单阶段目标检测算法,在车辆类别3个难度级别上的检测准确率分别为91.34%、79.85%和75.98%,较基线算法分别提升了4.83%、3.26%和3.32%。实验结果证明了本文算法及所提模块在三维目标检测任务上的有效性和先进性。

基于SWAT模型的南方水稻灌区全生育期面源污染特征及控制模拟

为了解水稻生育期内灌区面源污染的输出特征及其对下游控制断面水质的影响,选取某典型南方水稻灌区为研究对象,基于SWAT模型构建田沟塘控制断面的面源污染全过程数值模拟模型,量化分析水稻全生育期9种污染控制方案下控制断面水质动态响应。结果表明:退水和氮、磷污染物均呈脉冲式排放,水稻生育期前半段,即移植返青期、分蘖期和拔节孕穗期是稻田面源污染发生的高峰期;控制灌溉、生态工程和控制排水措施在水稻生育期前半段对氮、磷污染物的削减效果较好,实施综合措施后削减效果显著提升,对TN和TP全生育期的削减率超过90%;单项措施的水质提升效果有限,施肥管理导致分蘖期出现更多脉冲式TN质量浓度峰值,综合措施可显著提升水质达标率,其中施肥管理、控制排水、生态工程的组合措施和控制灌溉、施肥管理、控制排水、生态工程的组合措施可以实现TN和TP质量浓度稳定达标。

基于多尺度时空特征和篡改概率改善换脸检测的跨库性能

目前大多DeepFake换脸检测算法过于依赖局部特征,尽管库内检测性能尚佳,但容易出现过拟合,导致跨库检测性能不理想,即泛化性能不够好。有鉴于此,文中提出一种基于多尺度时空特征和篡改概率的换脸视频检测算法,目的是利用假脸视频中广泛存在的帧间时域不连续性缺陷来解决现有检测算法在跨库、跨伪造方式和视频压缩时性能明显下降的问题,改善泛化检测能力。该算法包括3个模块:为检测假脸视频在时域上留下的不连续痕迹,设计了一个多尺度时空特征提取模块;为自适应计算多尺度时空特征之间的时空域关联性,设计了一个三维双注意力机制模块;为预测随机选取的像素点的篡改概率和构造监督掩膜,设计了一个辅助监督模块。将所提出的算法在FF++、DFD、DFDC、CDF等公开大型标准数据库中进行实验,并与基线算法和近期发布的同类算法进行对比。结果显示:文中算法在保持库内平均检测性能优良的同时,跨库检测和抗视频压缩时的综合性能最好,跨伪造方法检测时的综合性能中等偏上。实验结果验证了文中算法的有效性。

MIT测井数据的点云转换及井筒形变诊断

针对多臂井径仪(MIT)采集井筒内壁空间位置参数可视化需求,现提出将其转换为点云数据,再通过对数据模型诊断分析得到井筒的形变类型。建立MIT测井过程可视化模型,通过引入柱面坐标来标定每个测点三维坐标;将每个测点的空间位置信息由极坐标转换为直角坐标,形成点云模型。采用所提方法将SH54井风险段处MIT数据成功转换为点云数据,并对该井470~471 m处的点云模型以类似CT横断扫描诊断的方式进行平铺展开,利用曲线拟合、面积计算得到SH54井在470~471 m处每个横断面的实际轮廓线和实际面积。结果表明:利用该方法生成的点云模型通过图表对比分析,可推断出该井段产生了非对称挤压缩径形变。

基于断面水边线定向的视频测流摄像机标定

针对现有基于直接线性变化法(DLT)的图像法测流技术依赖于地面控制点,存在效率低、风险高、宽断面天然河流操作难度大等问题,该文提出一种基于断面水边线定向的摄像机姿态角标定方法(CSWO)。该方法将标定过程分解为实验室内参标定和现场外参标定两步,其中后者又被划分为摄像机定位和定向两个环节。定向环节中首先在摄像机安装时将光轴与断面方向对齐,使方位角置零。然后利用无畸变图像中人工标注的平直断面水边线的斜率计算出横滚角。接下来通过计算水边线与图像纵轴交点作为其亚像素像方坐标。最后依据透视投影成像模型,联合水位与插值断面高程求得的物方坐标解算出俯仰角。该方法应用于时空图像测速法(STIV),实现了200 m宽河流的免像控表面流速测量。结果表明:起点距的最大绝对误差为0.59 m,最大相对误差为0.45%,表面流速的最大相对误差小于6.3%。