Review:Layer⁃Number Controllable Preparation of High⁃Quality Graphene for Wide Applications

Graphene, a well-known two-dimensional(2 D) material, has sparked broad enthusiasm in both scientific and industrial communities in these years, due to its exceptional electrical, thermal, mechanical, and versatile properties. However, many properties and applications of graphene are layer-number dependent. The preparation of high-quality graphene with controlled layer numbers is full of challenge, since the layer number varies much with the synthesis routes and relevant experimental conditions. Hence, there is an urgent need to improve the layer-number controllability of graphene preparation. Generally, graphene can be prepared by two complementary approaches: "top-down" and "bottom-up". Since they have their own advantages, the recent advances in the layer-number tunable preparation of high-quality graphene are separately studied from the two aspects in this review, especially those dedicated to single parameter. Some effective strategies are discussed in detail, mainly including 1) supercritical-CO2 assisted sonication, electrochemical exfoliation of graphite intercalation compounds, and layer-by-layer thinning with plasma or laser, for "top-down" graphene;2) chemical vapor deposition(CVD) on dual-metal substrate, ion-implantation CVD, layer-by-layer CVD, plasma-enhanced CVD, layered-double-hydroxides template-assisted CVD;and 3) graphite-enclosure assisted epitaxial growth and pulsed-magnetron-sputtering assisted physical vapor deposition for "bottom-up" graphene on various substrates. In addition, the respective advantages of graphene with different layer numbers in properties and applications are also presented. Finally, the contribution concludes with some important perspectives on the remained challenges and future perspectives.

Using modified Soil Conservation Service curve number method to simulate the role of forest in flood control in the upper reach of the Tingjiang River in China

To improve flood control efficiency and increase urban resilience to flooding,the impacts of forest type change on flood control in the upper reach of the Tingjiang River(URTR) were evaluated by a modified model based on the Soil Conservation Service curve number(SCS-CN) method. Parameters of the model were selected and determined according to the comprehensive analysis of model evaluation indexes. The first simulation of forest reconstruction scenario,namely a coniferous forest covering 59.35km^2 is replaced by a broad-leaved forest showed no significant impact on the flood reduction in the URTR. The second simulation was added with 61.75km^2 bamboo forest replaced by broad-leaved forest,the reduction of flood peak discharge and flood volume could be improved significantly. Specifically,flood peak discharge of 10-year return period event was reduced to 7-year event,and the reduction rate of small flood was 21%-28%. Moreover,the flood volume was reduced by 9%-14% and 18%-35% for moderate floods and small floods,respectively. The resultssuggest that the bamboo forest reconstruction is an effective control solution for small to moderate flood in the URTR,the effect of forest conversion on flood volume is increasingly reduced as the rainfall amount increases to more extreme magnitude. Using a hydrological model with scenarios analysis is an effective simulation approach in investigating the relationship between forest type change and flood control. This method would provide reliable support for flood control and disaster mitigation in mountainous cities.

Preliminary prediction of the control reproduction number of COVID-19 in Shaanxi Province,China

Objectives Firstly,according to the characteristics of COVID-19 epidemic and the control measures of the government of Shaanxi Province,a general population epidemic model is es-tablished.Then,the control reproduction number of general population epidemic model is obtained.Based on the epidemic model of general population,the epidemic model of general population and college population is further established,and the control reproduction number is also obtained.Methods For the established epidemic model,firstly,the expression of the control reproduc-tion number is obtained by using the next generation matrix.Secondly,the real-time reported data of COVID-19 in Shaanxi Province is used to fit the epidemic model,and the parameters in the model are estimated by least square method and MCMC.Thirdly,the Latin hypercube sampling method and partial rank correlation coefficient(PRCC)are adopted to analyze the sensitivity of the model.Conclusions The control reproduction number remained at 3 from January 23 to January 31,then gradually decreased from 3 to slightly greater than 0.2 by using the real-time reports on the number of COVID-19 infected cases from Health Committee of Shaanxi Province in China.In order to further control the spread of the epidemic,the following measures can be taken:(i)reducing infection by wearing masks,paying attention to personal hygiene and limiting travel;(i)improving isolation of suspected patients and treatment of symptomatic individuals.In particular,the epidemic model of the collge population and the general population is estab-lished,and the control reproduction number is given,which will provide theoretical basis for the prevention and control of the epidemic in the colleges.

Combinatory Spread－Spectrum Multiple－Access Based on Residue Number System：System and Performance

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Model Reduction Methods for High-Rise Buildings with Active Mass Damper Control Systems

To improve the performance of an active mass damper control system,the controller should be designed based on a reduced-order model. An improved method based on balanced truncation method was proposed to reduce the dimension of high-rise buildings,and was compared with other widely used reduction methods by using a framework with ten floors. This optimized method has improvement of reduction process and choice of the order. Based on the reduced-order model obtained by the improved method and pole-assignment algorithm,a controller was designed. Finally,a comparative analysis of structural responses,transfer functions,and poles was conducted on an actual high-rise building. The results show the effectiveness of the improved method.

Application of Sturm Theorem in the Global Controllability of a Class of High Dimensional Polynomial Systems

In this paper, the global controllability for a class of high dimensional polynomial systems has been investigated and a constructive algebraic criterion algorithm for their global controllability has been obtained. By the criterion algorithm, the global controllability can be determined in finite steps of arithmetic operations. The algorithm is imposed on the coefficients of the polynomials only and the analysis technique is based on Sturm Theorem in real algebraic geometry and its modern progress. Finally, the authors will give some examples to show the application of our results.

眼镜镜片尖边轮廓的五轴数控加工

为了改善和优化眼镜镜片的加工流程,避免镜片尖边加工过程中刀轴矢量变化剧烈、影响工件表面的加工质量,提出了一种基于UG NX的五轴数控加工路径。利用智能镜框扫描仪对镜框边缘进行扫描,获得镜框凹槽点云数据文件,编写相应程序对符合眼镜片加工标准的OMA文件中的球坐标数据进行坐标及格式转换等处理。基于NURBS曲线拟合算法,实现刀路轨迹的连续性并保证拟合曲线的精度。设计和建立一种控制刀轴矢量平滑变化的刀轴驱动约束方法,依靠曲线驱动刀轴及镜片曲面法向量约束刀轴使刀头平滑进给,并将刀轨文件经过后处理转换为NC文件。最后,对加工后的镜片进行误差测量,结果表明,通过点云数据拟合刀路曲线的方法提高了加工面的精确度和光滑性,有效缩减了加工流程,提高了加工效率。

某装备天线伺服系统算法研究

论文根据某装备伺服系统实际应用情况,考虑其实时跟踪目标特点,采用了快速最优算法+模糊PID算法相结合的控制策略,有效确保了天线的实时稳定运转。通过实验测试,采用快速最优算法+模糊PID算法的控制策略,天线稳定运行,全系统具有良好的动静态特性。

高速铁路连续大号码道岔应答器布置及功能实现

高速铁路大号码道岔是提升车站运输效率的重要基础设施,列控系统必须结合大号码道岔的布置特点,控制车地信息交互,以确保列车按规定速度经大号码道岔侧向运行。通过分析大号码道岔应答器的设置及报文发送原则,结合车载设备在特定码序下的控制逻辑,开展系统性研究,在不改变既有CTCS体系基本架构的前提下,通过理论分析、场景研究、仿真验证等方法,提出并充分验证高速铁路连续大号码道岔应答器的布置原则,以及大号码道岔应答器报文的控制方案。该方案有效提高了列车在“弯进弯出”场景下,经过连续大号码道岔侧向的运行效率,进一步扩展了列控系统在复杂运营场景中的控制能力。

机坪管制移交区域划设影响因素研究

论文针对机坪管制移交工作中责任边界划设问题,构建机坪管制移交区域划设影响因素体系,将灰数系统理论融入DEMATEL-AISM模型中,利用中心度与熵权法改进模型主观赋权问题,构建Grey-DEMATEL-AISM模型,探寻因素间耦合关系,划分因素层级结构,并根据成都双流国际机场机坪管制移交情况进行实例验证。结果表明:机坪管制移交区域划设影响因素共15个,其结构体系可划分为5个层次,机坪管制员负荷与空管塔台管制员负荷为原因度最小的结果因素,位于上层直观层;塔台位置、跑滑构型等12项因素位于中间过渡层;场面流量是原因度最大的原因因素,位于底层根源层。

基于α-截集三角模糊数和攻击树的CTCS网络安全风险评估方法

针对工业控制系统网络安全风险评估影响因素的不确定性和指标量化困难问题,提出一种基于模糊理论和攻击树的方法评估工业控制系统风险,并将它应用于中国列车控制系统(CTCS)的风险评估。首先,基于CTCS可能面临的网络安全威胁和系统自身的脆弱性建立攻击树模型,使用α-截集三角模糊数(TFN)计算攻击树叶节点和攻击路径的区间概率;其次,利用层次分析法(AHP)建立安全事件损失数学模型,最终得出风险评估值。实验结果表明,所提方法可以有效评估系统风险,预测攻击路径,降低主观因素对风险评估过程的影响,使评估结果更契合实际,为安全防护策略的选择提供参考和依据。

基于语法协议的指控系统间数据互操作方法研究

针对目前异构指控系统间作战筹划方案数据结构、要素、种类关联显性度低,导致实现数据共享难度增大,作战方案互操作困难的问题,在梳理和吸收国内外现有指控系统间数据互操作的流程和数据结构的基础上,将当前互操作模式分为三类并举例分析。研究基于C-BML(Coalition Battle Management Language)框架结构提出了一种具有普遍适用性的数据互通协议格式,对解决异构指控系统间作战筹划方案数据传输困难的问题进行了探索。

基于物联网数控的机械机电自动化控制系统设计研究

基于物联网数控的机械机电自动化控制系统要求将传感器、执行器及通信模块等设备互联,控制机械机电设备运行状态监测、生产流程控制以及运行数据。基于此,分析基于物联网数控的机械机电自动化控制系统的设计需求、框架等,从软件和硬件两个维度分析自动化控制系统的设计。

Stabilization of CSTR w ith Self-tuning Sliding Mode Controller Using T-S Fuzzy Linearization

A self-tuning reaching law based sliding mode control(SMC)theory is proposed to stabilize the nonlinear continuous stirred tank reactor(CSTR).T-S fuzzy logic is used to build a global fuzzy state-space linear model.Combing the traits of SMC and CSTR,three fuzzy rules can meet the requirements of controlled system.The self-tuning switch control law which can drive the state variables to the sliding surface as soon as possible is designed to ensure the robustness of uncertain fuzzy system.Lyapunov equation is applied to proving the stability of the sliding surface.The simulations show that the proposed approach can achieve desired performance with less chattering problem.

海洋石油安全风险监测预警体系构建与系统应用

在国家推进“工业互联网+安全生产”,实施风险分级管控和隐患排查治理双重预防数智化建设的大背景下,为降低海洋油气生产平台安全生产风险,保障“一线平台-作业公司-分(子)公司-总部”对风险预警信息获取的即时性、准确性,构建了“风险→隐患→事故”链条式海洋石油安全风险监测预警体系,开发了以风险动态监测和分级管控为目的的海洋石油安全风险监测预警系统,充分利用海洋油气生产平台原有监测监控系统对各类安全风险进行监测,通过风险实时计算综合预警模型进行风险的预测预判,实现风险识别、风险预警、风险监控、风险处理、处理结果反馈的标准化风险闭环管控,有效提升了海洋平台安全风险管控能力。

Generation of minimally persistent circle formation for a multi-agent system

In this paper, two methods of generating minimally persistent circle formation are presented. The proposed methods adopt a leader-follower strategy and all followers are firstly motivated to move into the leader＇s interaction range. Based on the information about relative angle and relative distance, two numbering schemes are proposed to generate minimally persistent circle formation. Distributed control laws are also designed to maintain the desired relative distance between agents. The distinctive features of the proposed methods are as follows. First, only 2n - 3 unilateral communication links for n agents are needed during the circle formation process and thus the communication complexity can be reduced. In addition, the formation topology is kept fixed for the whole motion and achieves a self-stability property. Finally, each follower keeps a regualr interval with its neighbors and the formation converges to a uniform circle formation. Simulation results are also provided to demonstrate the effectiveness of the proposed methods.

Global Transmission Dynamics of a Schistosomiasis Model and Its Optimal Control

Drug treatment, snail control, cercariae control, improved sanitation and health education are the effective strategies which are used to control the schistosomiasis. In this paper, we consider a deterministic model for schistosomiasis transmission dynamics in order to explore the role of the several control strategies. The global stability of a schistosomiasis infection model that involves mating structure including male schistosomes, female schistosomes, paired schistosomes and snails is studied by constructing appropriate Lyapunov functions. We derive the basic reproduction number R0 for the deterministic model, and establish that the global dynamics are completely determined by the values of R0. We show that the disease can be eradicated when R0?≤1;otherwise, the system is persistent. In the case where ?R0?>1, we prove the existence, uniqueness and global asymptotic stability of an endemic steady state. Sensitivity analysis and simulations are carried out in order to determine the relative importance of different control strategies for disease transmission and prevalence. Next, optimal control theory is applied to investigate the control strategies for eliminating schistosomiasis using time dependent controls. The characterization of the optimal control is carried out via the Pontryagins Maximum Principle. The simulation results demonstrate that the insecticide is important in the control of schistosomiasis.

Dynamics of a two-group model for assessing the impacts of pre-exposure prophylaxis,testing and risk behaviour change on the spread and control of HIV/AIDS in an MSM population

Although much progress has been made in reducing the public health burden of the human immunodeficiency virus(HIV),which causes acquired immunodeficiency syndrome(AIDS),since its emergence in the 1980s(largely due to the large-scale use and availability of potent antiviral therapy,improved diagnostic and intervention and mitigation measures),HIV remains an important public health challenge globally,including in the United States.This study is based on the use of mathematical modeling approaches to assess the population-level impact of pre-exposure prophylaxis(PrEP),voluntary testing(to detect undetected HIV-infected individuals),and changes in human behavior(with respect to risk structure),on the spread and control of HIV/AIDS in an MSM(men-who-have sex-with-men)population.Specifically,a novel two-group mathematical model,which stratifies the total MSM population based on risk(low or high)of acquisition of HIV infection,is formulated.The model undergoes a PrEP-induced backward bifurcation when the control reproduction number of the model is less than one if the efficacy of PrEP to prevent a high-risk susceptible MSM individual from acquiring HIV infection is not perfect(the consequence of which is that,while necessary,having the reproduction number of the model less than one is no longer sufficient for the elimination of the disease in the MSM population).For the case where the efficacy of PrEP is perfect,this study shows that the disease-free equilibrium of the two-group model is globally-asymptotically stable when the associated control reproduction number of the model is less than one.Global sensitivity analysis was carried out to identify the main parameters of the model that have the highest influence on the value of the control reproduction number of the model(thereby,having the highest influence on the disease burden in the MSM population).Numerical simulations of the model,using a plausible range of parameter values,show that if half of the MSM population considered adhere strictly to the specified PrEP regimen(while other interventions are maintained at their baseline values),a reduction of about 22%of the new yearly HIV cases recorded at the peak of the disease could be averted(compared to the worst-case scenario where PrEP-based intervention is not implemented in the MSM population).The yearly reduction at the peak increases to about 50%if the PrEP coverage in the MSM population increases to 80%.This study showed,based on the parameter values used in the simulations,that the prospects of elimination of HIV/AIDS in the MSM community are promising if high-risk susceptible individuals are no more than 15%more likely to acquire HIV infection,in comparison to their low-risk counterparts.Furthermore,these prospects are significantly improved if undetected HIV-infected individuals are detected within an optimal period of time.

超大封闭TBS对黔中地区农田害鼠的控制效果

TBS灭鼠技术是我国近年农田害鼠绿色防控的核心技术之一,目前推广应用的是标准的60 m围栏的矩形或线形TBS,超大TBS的灭鼠效果未有报道。本文在息烽县比较了2020年不同月份600 m超大封闭式、60 m矩形和60 m直线型TBS捕获害鼠的种类组成、捕获数量、不同月份捕鼠量以及控制效果。3种TBS围栏共捕鼠393只,7个鼠种。各不同类型TBS捕获鼠种组成比例无明显差异,均以黑线姬鼠为优势种,占总捕鼠量的45.04%;不同类型TBS捕鼠数的月份变化趋势相同,均呈现单峰型,高峰期为5—6月。3种类型TBS控制效果为66.67%~70.00%,效果良好。但600 m超大封闭式TBS,控害面积大,较常规TBS劳动成本投入减少,在贵州山区具有良好的推广价值。

二回路系统控制棒失步仿真与处置策略研究

核动力系统主机降工况时反应堆控制棒失步是二回路系统的一类特有危险故障,一旦发生会造成主蒸汽管路系统压力迅速上升,进而造成一系列故障响应,严重影响核动力系统的安全运行。论文通过分析故障发生时总管压力,蒸汽发生器压力,喷嘴流量的变化情况,研究了此故障模式下PID和乒乓开关两种不同的泄放阀控制策略对系统的影响,并进行了仿真试验验证;得出了乒乓开关策略的响应速度要高于传统PID控制,在极端状况下可以快速降低总管压力;而PID控制虽然响应速度较慢,但调节稳定性较好的结论,对实际装备研究有一定的参考价值。