An Improved Double-Threshold Method Based on Gradient Histogram

This paper analyzes the characteristics of the output gradient histogram and shortages of several traditional automatic threshold methods in order to segment the gradient image better. Then an improved double-threshold method is proposed, which is combined with the method of maximum classes variance, estimating-area method and double-threshold method. This method can automatically select two different thresholds to segment gradient images. The computer simulation is performed on the traditional methods and this algorithm and proves that this method can get satisfying result. Key words gradient histogram image - threshold selection - double-threshold method - maximum classes variance method CLC number TP 391. 41 Foundation item: Supported by the National Nature Science Foundation of China (50099620) and the Project of Chenguang Plan in Wuhan (985003062)Biography: YANG Shen (1977-), female, Ph. D. candidate, research direction: multimedia information processing and network technology.

Control over hysteresis curves and thresholds of optical bistability in different semiconductor double quantum wells

The effects of optical field on the phenomenon of optical bistability(OB) are investigated in a K-type semiconductor double quantum well(SDQW) under various parametric conditions. It is shown that the OB threshold can be manipulated by increasing the intensity of coupling field. The dependence of the shift of OB hysteresis curve on probe wavelength detuning is then explored. In order to demonstrate controllability of the OB in this SDQW, we compare the OB features of three different configurations which could arise in this SDQW scheme, i.e., K-type, Y-type, and inverted Y-type systems. The controllability of this semiconductor nanostructure medium makes the presented OB scheme more valuable for applications in all-optical switches, information storage, and logic circuits of all optical information processing.

Cooperative Spectrum Sensing Based on Centralized Double Threshold in MCN

Cooperative spectrum sensing appears popular currently due to its ability to solve the issue of hidden terminal and improve detection performance in Cognitive Radio Networks. Meanwhile, double threshold based energy detector has attracted much attention for its low computational complexity and superior performance. Motivated by this, a cooperative spectrum sensing scheme is proposed in this paper based on centralized double threshold in the maritime communication networks(MCN), where the energy value of received signal in each cognitive node is forwarded to the fusion center for final decision based on double thresholds. Additionally, the proposed scheme is further optimized for the decisions that the energy is within the scope of maximum threshold and minimum threshold. Simulation experiments verify the performance of the proposed method.

A Double Threshold Energy Detection-Based Neural Network for Cognitive Radio Networks

In cognitive radio networks(CoR),the performance of cooperative spectrum sensing is improved by reducing the overall error rate or maximizing the detection probability.Several optimization methods are usually used to optimize the number of user-chosen for cooperation and the threshold selection.However,these methods do not take into account the effect of sample size and its effect on improving CoR performance.In general,a large sample size results in more reliable detection,but takes longer sensing time and increases complexity.Thus,the locally sensed sample size is an optimization problem.Therefore,optimizing the local sample size for each cognitive user helps to improve CoR performance.In this study,two new methods are proposed to find the optimum sample size to achieve objective-based improved(single/double)threshold energy detection,these methods are the optimum sample size N^(*)and neural networks(NN)optimization.Through the evaluation,it was found that the proposed methods outperform the traditional sample size selection in terms of the total error rate,detection probability,and throughput.

Crack spacing threshold of double cracks propagation for large-module rack

Large-module rack of the Three Gorges shiplift is manufactured by casting and machining, which is unable to avoid slag inclusions and surface cracks. To ensure its safety in the future service, studying on crack propagation rule and the residual life estimation method of large-module rack is of great significance. The possible crack distribution forms of the rack in the Three Gorges shiplift were studied. By applying moving load on the model in FRANC3 D and ANSYS, quantitative analyses of interference effects on double cracks in both collinear and offset conditions were conducted. The variation rule of the stress intensity factor(SIF) influence factor, RK, of double collinear cracks changing with crack spacing ratio, RS, was researched. The horizontal and vertical crack spacing threshold of double cracks within the design life of the shiplift were obtained, which are 24 and 4 times as large as half of initial crack length, c0, respectively. The crack growth rates along the length and depth directions in the process of coalescence on double collinear cracks were also studied.

Two-dimensional models of threshold voltage and subthreshold current for symmetrical double-material double-gate strained Si MOSFETs

The two-dimensional models for symmetrical double-material double-gate （DM-DG） strained Si （s-Si） metal-oxide semiconductor field effect transistors （MOSFETs） are presented. The surface potential and the surface electric field ex- pressions have been obtained by solving Poisson＇s equation. The models of threshold voltage and subthreshold current are obtained based on the surface potential expression. The surface potential and the surface electric field are compared with those of single-material double-gate （SM-DG） MOSFETs. The effects of different device parameters on the threshold voltage and the subthreshold current are demonstrated. The analytical models give deep insight into the device parameters design. The analytical results obtained from the proposed models show good matching with the simulation results using DESSIS.

Role of Nuclear Coulomb Attraction in Nonsequential Double Ionization of Argon Atom

The microscopic recollision dynamics in strong-field nonsequential double ionization of Ar atoms is in- vestigated using three-dimensional classical ensembles. By adjusting the nuclear Coulomb potential, we can excellently reproduce the experimental results both within the laser intensity regimes well above the reeollision threshold and well below the recollision threshold quantitatively. More importantly, our trajectory analysis clearly reveals the particular electronic dynamics in recollision process： the momentum of the recolliding electron encounters a sudden change both in magnitude and in direction when it approaches the nucleus closely, which show that the nuclear Coulomb attraction plays a key role in the recollision process of nonsequential double ionization of Ar atoms.

Fragmentation dynamics of electron-impact double ionization of helium

We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V to 1 ke V for comparative study. At the lowest excess energy, i.e., close to the double-ionization threshold, it is found that the projectile momentum is totally transferred to the recoil-ion while the residual energy is randomly partitioned among the three outgoing electrons, which are then most probably emitted with an equilateral triangle configuration. Our results agree well with experiments as compared with early quantum-mechanical calculation as well as classical simulation based on a two-dimensional Bohr's model. Furthermore, by mapping the final momentum vectors event by event into a Dalitz plot,we unambiguously demonstrate that the ergodicity has been reached and thus confirm a long-term scenario conceived by Wannier. The time scale for such few-body thermalization, from the initial nonequilibrium state to the final microcanonical distribution, is only about 100 attoseconds. Finally, we predict that, with the increase of the excess energy, the dominant emission configuration undergoes a transition from equilateral triangle to T-shape and finally to a co-linear mode. The associated signatures of such configuration transition in the electron–ion joint momentum spectrum and triple-electron angular distribution are also demonstrated.

PMF+双门限Tong检测的北斗B1I信号捕获算法

针对传统Tong检测算法检测时间长、漏警概率大的问题,提出将PMF+双门限Tong检测算法应用于北斗B1I信号的捕获中。首先,将射频前端模块处理得到的中频信号下变频至基带,对基带信号进行降速等预处理;然后,利用部分匹配滤波(PMF)算法计算相关值,通过PMF算法将数据信号分成几个均等片段,对每一段信号都分别计算相关值,会出现三组具有同相位的相关结果;最后,利用双门限Tong检测算法对PMF算法计算得到的相关结果检测,达到捕获B1I信号的目的。仿真结果表明,利用该算法捕获北斗B1I信号,有效提高了捕获时的检测概率并缩短了检测时间,提高了捕获B1I信号的速度。

透射电镜样品制备评定系统设计与应用

为了实现透射电镜样品制备的质量评定,选择影响电解双喷的主要实验工艺参数,制备TC4钛合金、DC56D+Z钢和AA6451铝合金的透射电镜样品,以薄区形貌图像为分析对象,设计了透射电镜样品制备的定量分析和定性评价系统。该系统主要包括灰度测量与统计、阈值分割以及颗粒特征与分析模块。根据薄区形貌图像的灰度特征,选择某一个灰度级进行阈值分割,二值化图像后提取薄区孔洞轮廓,并定量统计薄区孔洞面积,从而分析对样品制备质量的影响规律;选取合适的灰度级范围,对其像素数平均值进行统计,选择并确定样品制备质量合格与否的临界值。在较高倍数下,通过透射电镜观察评定合格的样品微观形貌,以验证样品制备评定系统的准确性。通过以上标准化透射电镜样品制备的实验工艺和评定分析流程,可以优化制备工艺参数和提高测试分析效率。

基于灰度均值的自适应FAST角点检测优化算法

光照不均、突变引起的灰度变化会影响图像特征检测效果。为此,设计一种基于灰度均值的自适应FAST-9-12角点检测算法。首先,利用特征点的延展性设计一种小面积双重检测模板,减少像素点与中心点的比较次数,提高区域正检率和检测速度;其次,依据图像局部灰度均值,在每个像素点检测模板内自适应调整阈值,避免灰度变化影响检测效果;最后,根据柔性非极大值抑制的思想设计角点半径抑制原则,筛选鲁棒性更强的角点。在Inria遥感影像数据集上的实验结果表明,FAST-9-12角点检测速度比FAST-12-16,FAST-9-16两种模板提高22%左右,因自适应阈值的提取方式不易受光照影响,检测准确率分别提高4.16和3.11个百分点,实现了图像特征快速和精准检测。

“双碳”目标下再生资源利用的碳减排效应及作用机制研究

再生资源利用的碳减排效应对推动形成适合中国国情的差异化减排路径和实现“双碳”目标具有重大意义。在此背景下,深入探讨和评估再生资源利用的碳减排效应及作用机制,是学界亟待厘清的重要课题。文章作者首先将再生资源对原生资源的替代利用看作是一种环境反污染活动,并构造社会效用函数,基于最优控制理论模型,推导再生资源利用对碳减排效应的影响机制。理论推导结果表明:再生资源利用碳减排效应是否存在取决于再生资源利用过程消耗资源的系数,当再生资源替代减少的碳排放大于再生资源回收利用过程中新消耗资源的碳排放,即再生资源替代减碳的“收益”大于“成本”,此时存在再生资源的碳减排效应。其次,运用2005—2019年中国省级面板数据,实证考察再生资源利用水平对碳排放的综合影响,并进一步开展了作用机制分析、门槛效应检验以及异质性讨论。实证检验结果表明:从总体上看,我国再生资源的利用水平与二氧化碳排放表现为负相关关系,再生资源利用能够有效抑制碳排放强度,再生资源减碳的“收益”是大于“成本”的。从作用机制上看,绿色技术创新效应和产业升级结构效应是再生资源利用影响碳排放的重要作用渠道,再生资源替代可以通过推动绿色技术创新和提升产业结构高级化水平抑制区域碳排放强度。门槛效应检验发现,选取再生资源利用水平和经济发展水平作为门槛变量时,再生资源利用水平在影响碳排放时存在一定门槛效应,超过特定门槛值时再生资源利用的碳减排效应越明显,结果表明再生资源替代与碳减排之间的关系并非线性的。进一步通过异质性分析发现地理区位特征和循环经济发展水平的差异使再生资源利用碳减排效应呈现异质性特征。东部地区(相较于西部地区)、南方地区(相较于北方地区)、循环经济发展水平越高的地区,再生资源利用的碳减排效应越明显。结合以上研究结果,文章提出提升再生资源利用水平和经济发展质量、加强技术创新活动扶持、推动产业链升级、制定差异化再生资源利用策略等政策建议。

数字经济发展对我国省级电力行业碳排放影响研究

基于2013—2022年我国30个省份的面板数据,运用双固定效应模型和面板门槛模型实证分析了数字经济发展对我国省级电力行业碳排放的影响。研究发现:(1)数字经济具有减排红利,可以显著降级电力行业的碳排放;(2)数字经济对电力行业碳排放的影响存在区域异质性,对中西部地区的抑制作用强于东部地区;(3)门槛效应表明,数字经济对电力行业碳排放的影响呈现边际效应递增的规律。研究结果对我国省级电力行业实现差异化碳减排具有一定的参考价值,能够促进“双碳”目标的实现。

基于深度强化学习和隐私保护的群智感知动态任务分配策略

在移动群智感知(Mobile Crowd Sensing,MCS)中,动态任务分配的结果对提高系统效率和确保数据质量至关重要。然而,现有的大部分研究在处理动态任务分配时,通常将其简化为二分匹配模型,该简化模型未充分考虑任务属性与工人属性对匹配结果的影响,同时忽视了工人位置隐私的保护问题。针对这些不足,文章提出一种基于深度强化学习和隐私保护的群智感知动态任务分配策略。该策略首先通过差分隐私技术为工人位置添加噪声,保护工人隐私;然后利用深度强化学习方法自适应地调整任务批量分配;最后使用基于工人任务执行能力阈值的贪婪算法计算最优策略下的平台总效用。在真实数据集上的实验结果表明,该策略在不同参数设置下均能保持优越的性能,同时有效地保护了工人的位置隐私。

基于改进切尾均值的矿井图像去噪算法

现有矿井图像去噪算法对于复杂噪声的去除效果有限,且处理速度不能满足实时监控需求。针对该问题,提出一种基于改进切尾均值的矿井图像去噪算法。首先,采用切尾均值滤波器对图像噪声进行初步滤除,同时引入二次检验机制处理残留的噪声点,通过引入离散系数提升算法对不同像素的区分能力,增强去噪性能;其次,采用基于极值数量的分类处理及再次检验机制,有效减少残留噪声问题;然后,在小波函数中引入新的控制变量优化软阈值函数和硬阈值函数,构建双阈值函数,结合Radon变换增强对线性特征的处理,增强对矿井图像的检测能力;最后,采用均方误差(MSE)与峰值信噪比(PSNR)进行图像质量评价。实验结果表明:相较于切尾均值算法、硬阈值算法、软阈值算法,基于改进切尾均值的矿井图像去噪算法处理的图像的MSE增长相对缓慢,MSE最小,图像去噪效果最好;引入离散系数后,去噪图像的MSE相较于引入前低300 dB左右,PSNR相较于引入前高20 dB左右,引入离散系数能有效减少噪声点对算法的影响;相较于卡尔曼遗传优化算法、变换域图像去噪算法、交叉分支卷积去噪网络,基于改进切尾均值的矿井图像去噪算法处理的图像MSE分别降低了27,21,13 dB,PSNR分别提升了8,6,3 dB,去噪耗时分别缩短了0.20,0.16,0.14 s。

高速切换场景下的双门限判决算法研究

传统的越区切换算法无法应对高速列车提速带来的通信质量需求增长,本文提出一种基于双门限判决的位置触发切换算法,以提升越区切换时的通信质量。选择大小双门限值,能够有效减少信号强度波动带来的影响。在接收信号强度波动较小时采用双门限中的较小值,波动较大时则采用较大值,针对每次测量结果实时进行连续双判决。仿真结果表明:相较于传统切换算法,双门限判决算法能够使得切换发生位置更靠近基站重叠区域的中点,进而降低切换掉话率和切换失败率。同时双判决减小了平均切换次数,使通信体验得到了极大提升。

融合自适应步长与地图匹配的智能手机PDR室内定位算法

针对经典的PDR算法中步长估算模型无法适应不同个体之间差异以及手机内部传感器航向角估算不准确的问题,提出了一种融合自适应步长与地图匹配的智能手机PDR室内定位算法。该算法在Weinberg模型的基础上,引入相邻波峰时间差函数以提高步长模型的适应性。采用双阈值法进行步频检测,并利用卡尔曼滤波优化地图匹配后的航向角,最终实现室内行人的精确定位。实验数据显示,所提算法总路程的闭环误差为0.58%,与仅使用自适应步长相比下降了73.29%,与仅使用地图匹配相比下降了59.21%,行程72 m的累积误差为4.484 m,相较于经典的PDR算法下降了28.21%。改进后的算法定位精度显著提高,且闭环误差和累积误差更小。实验结果表明,该算法具有良好的工程应用价值。

“双一流”建设政策对城市创新能力的影响及其门槛效应研究

服务国家区域发展战略、引领区域经济社会创新发展是“双一流”建设的重要内容,也是其成效评价的重要方面。基于资源依赖理论,采用我国283个城市2012—2020年面板数据,构建双重差分模型和门槛效应模型实证研究“双一流”建设政策对城市创新能力的复杂影响机制。结果表明:“双一流”建设政策显著提升了建设高校所在城市的创新能力;资本投入水平和人力资本集聚水平对“双一流”建设政策促进建设高校所在城市的创新能力有门槛效应,在最优区间内可以实现“双一流”建设政策城市创新效应的最大发挥;资本投入水平和人力资本集聚水平对“双一流”建设政策促进建设高校所在城市的创新能力的门槛效应因区域不同而存在显著差异。鉴于此,相关部门应加强产学研协同创新,完善动态调整和竞争机制;优化经费投入和保障机制,加大基础研究支持力度;建立健全人才合理有序流动机制,促进人才结构与产业结构相匹配。

双闭环PID应用下投篮机器人路径跟踪控制研究

投篮机器人路径图像噪声会影响机器人路径跟踪控制效果,导致投篮机器人偏离正常轨迹,为此提出双闭环PID应用下投篮机器人路径跟踪控制方法。分析投篮机器人架构,利用OpenMv视觉识别方法采集投篮机器人路径图像,结合小波阈值算法对采集到的图像实施去噪处理,从而获取清晰的投篮机器人路径图像。根据图像去噪处理结果,将曲线拟合法与特征点检测法相结合,实现投篮机器人路径识别。根据投篮机器人路径识别结果确定路径实际偏移量,结合推动器实现位置、移动速度建立的双闭环PID控制器,从而实现投篮机器人路径跟踪控制。实验结果表明,该方法的投篮机器人路径图像去噪熊效果好、跟踪控制效果好,充分验证了该方法的有效性。

双芯微胶囊法自修复混凝土冻融试验研究

寒区水工混凝土长时间遭受冻融破坏和水流冲刷会形成联合破坏,修复难度较大、成本高、效果不理想,最终影响工程安全运行,而微胶囊自修复技术可实现混凝土自我修复。通过以E51型环氧树脂为内芯材,以固化剂PETMA为外芯材,以尿素和甲醛制备的脲醛树脂为壁材,采用原位聚合法制备出双芯微胶囊,研究结果表明:双芯微胶囊呈球状,粒径分布在40μm左右,表面饱满圆润,芯材含量为24.3%,包覆率为48.6%,热稳定性较好;混凝土在掺入双芯微胶囊后,在受到冻融破坏时能及时破裂,并释放出修复剂和固化剂对混凝土进行修复,混凝土抗冻等级也有效提高,最大可提高38.5%;双芯微胶囊掺量阈值为3%,掺量超过阈值后,修复效果会减弱。