面向动目标围捕的Multi-UUV编队协调控制研究

针对动目标围捕过程对Multi-UUV编队结构的灵活性要求较高的问题,基于欠驱动UUV的数学模型,在目标轨迹能够准确预测的前提下,改进了协调编队运动控制器。协调编队运动控制器的控制目标是在Multi-UUV编队跟踪并围捕动目标过程中,避免Multi-UUV之间,UUV与障碍物以及UUV与动目标之间的碰撞并以稳定的编队结构围捕动目标。将控制器设计过程分解为运动学控制和动力学控制。在运动学控制部分,实现动目标跟踪、UUV之间避撞及UUV偏航角误差为零的控制目标。在动力学控制部分,应用反步法设计实际的控制输入。仿真案例验证了协调运动控制器在动目标围捕中的有效性。

Multi-ACO Application in Routing and Scheduling Optimization of Maintenance Fleet (RSOMF) Based on Conditions for Offshore Wind Farms

Reducing the operation and maintenance (O & M) cost is one of the potential actions that could reduce the cost of energy produced by offshore wind farms. This article attempts to reduce O & M cost by improving the utilization of the maintenance resources, specifically the efficient scheduling and routing of the maintenance fleet. Scheduling and routing of maintenance fleet is a non-linear optimization problem with high complexity and a number of constraints. A heuristic algorithm, Ant Colony Optimization (ACO), was modified as Multi-ACO to be used to find the optimal scheduling and routing of maintenance fleet. The numerical studies showed that the proposed methodology was effective and robust enough to find the optimal solution even if the number of offshore wind turbine increases. The suggested approaches are helpful to avoid a time-consuming process of manually planning the scheduling and routing with a presumably suboptimal outcome.

Time-resolved K-shell x-ray spectra of nanosecond laser-produced titanium tracer in gold plasmas

A study of a nanosecond laser irradiation on the titanium-layer-buried gold planar target is presented. The timeresolved x-ray emission spectra of titanium tracer are measured by a streaked crystal spectrometer. By comparing the simulated spectra obtained by using the FLYCHK code with the measured titanium spectra, the temporal plasma states, i.e.,the electron temperatures and densities, are deduced. To evaluate the feasibility of using the method for the characterization of Au plasma states, the deduced plasma states from the measured titanium spectra are compared with the Multi-1D hydrodynamic simulations of laser-produced Au plasmas. By comparing the measured and simulated results, an overall agreement for the electron temperatures is found, whereas there are deviations in the electron densities. The experiment–theory discrepancy may suggest that the plasma state could not be well reproduced by the Multi-1D hydrodynamic simulation, in which the radial gradient is not taken into account. Further investigations on the spectral characterization and hydrodynamic simulations of the plasma states are needed. All the measured and FLYCHK simulated spectra are given in this paper as datasets. The datasets are openly available at http://www.doi.org/10.57760/sciencedb.j00113.00032.

Fluvial reservoir characterization and identification:A case study from Laohekou Oilfield

Finding channel sandbodies is an important task in oil and gas exploration due to the importance of fluvial reservoirs. It is difficult to describe fluvial reservoirs in detail owing to their frequent changes and serious intersections, as well as limitations of S/N ratio and seismic data resolution. Based on the Laohekou 3D data in Shengli Oilfield, we analyze the general characteristics of fluvial reservoirs in this area, from which we find that they are characterized by strong amplitudes on seismic profiles, high continuity on time slices, and low frequency in the frequency domain. In addition, a cluster of strong string-bead- like reflections was found after color processing and detailed interpretation. To understand this observation, we conduct forward modeling to explain the mechanism. This provides a new way to identify ancient channels in similar areas. By using the multi-attribute fusion and RGB display techniques, channel incision is more obvious and the characteristics of the channel structures are manifested much better. Finally, we introduce and apply multi-wavelet detection technology to identify weaker fluvial reservoir signals.

基于MULTI2D-Z程序的Z箍缩动态黑腔形成过程模拟

对辐射流体力学程序MULTI-2D进行改造,增加磁场演化方程程序模块,自洽地在运动方程模块中增加洛伦兹力,在能量方程模块中增加欧姆加热,将它改造成辐射磁流体力学程序MULTI2D-Z.验证了新增磁场程序模块的可靠性,并发现温度和密度的增大会抑制磁场的扩散,负径向速度梯度的流体对流也会抑制磁场的扩散.利用改造好的MULTI2D-Z程序模拟了峰值为8 MA的脉冲电流驱动的钨丝阵Z箍缩动态黑腔形成过程.得到了X光功率(约30 TW)和能量(约300 k J)、泡沫辐射温度(约120 eV)、箍缩轨迹等模拟结果.在动态黑腔形成过程中,磁场主要分布在钨主体等离子体中;辐射向内传播,烧蚀泡沫柱而使它膨胀;辐射热波在被撞击的泡沫柱中传播,其传播速度比物质温度传播得快,当辐射热波传播到中心轴时泡沫柱中的辐射场变得比较均匀,并且除了冲击波处外辐射温度与物质温度基本上没有分离.这些模拟结果可增强人们对磁场扩散和对流规律以及动态黑腔形成机制的理解,同时表明了MULTI2D-Z程序可成为Z箍缩及其应用的新的程序模拟工具.

Multivariable Control Performance Assessment Based on Generalized Minimum Variance Benchmark

This paper is concerned with the control performance assessment based on the multivariable generalized minimum variance benchmark.An explicit expression for the feedback controller-invariant(the generalized minimum variance)term of the multivariable control system is obtained,which is used as a standard benchmark for the assessment of the control performance for multi input multi output(MIMO)process.The proposed approach is based on the multivariable minimum variance benchmark.In comparison with the minimum variance benchmark, the developed method is more reasonable and practical for the control performance assessment of multivariable systems.The approach is illustrated by a simulation example and an industrial application.

Magnetoelastic combined resonance and stability analysis of a ferromagnetic circular plate in alternating magnetic field

The nonlinear combined resonance problem of a ferromagnetic circular plate in a transverse alternating magnetic field is investigated. On the basis of the deformation potential energy, the strain potential energy, and the kinetic energy of the circular plate, the Hamilton principle is used to induce the magnetoelastic coupling transverse vibration dynamical equation of the ferromagnetic circular plate. Based on the basic electromagnetic theory, the expressions of the magnet force and the Lorenz force of the circular plate are presented. A displacement function satisfying clamped-edge combined with the Galerkin method is used to derive the Duffing vibration differential equation of the circular plate. The amplitude-frequency response equations of the system under various combined resonance forms are obtained by means of the multi-scale method, and the stability of the steady-state solutions is analyzed according to the Lyapunov theory. Through examples, the amplitude-frequency characteristic curves with different parameters, the amplitude of resonance varying with magnetic field intensity and excitation force, and the time-course response diagram, phase diagram, Poincar′e diagram of the system vibration are plotted, respectively. The effects of different parameters on the amplitude and stability of the system are discussed. The results show that the electromagnetic parameters have a significant effect on the multi-valued attribute and stability of the resonance solutions, and the system may exhibit complex nonlinear dynamical behavior including multi-period and quasi-periodic motion.

An RKDG finite element method for the one-dimensional inviscid compressible gas dynamics equations in a Lagrangian coordinate

In this paper,Runge-Kutta Discontinuous Galerkin（RKDG） finite element method is presented to solve the onedimensional inviscid compressible gas dynamic equations in a Lagrangian coordinate.The equations are discretized by the DG method in space and the temporal discretization is accomplished by the total variation diminishing Runge-Kutta method.A limiter based on the characteristic field decomposition is applied to maintain stability and non-oscillatory property of the RKDG method.For multi-medium fluid simulation,the two cells adjacent to the interface are treated differently from other cells.At first,a linear Riemann solver is applied to calculate the numerical ？ux at the interface.Numerical examples show that there is some oscillation in the vicinity of the interface.Then a nonlinear Riemann solver based on the characteristic formulation of the equation and the discontinuity relations is adopted to calculate the numerical ？ux at the interface,which suppresses the oscillation successfully.Several single-medium and multi-medium fluid examples are given to demonstrate the reliability and efficiency of the algorithm.

Target estimation using MIMO radar with multiple subcarriers

This paper analyzes the effect of waveform parame- ters on the joint target location and velocity estimation by a non- coherent multiple input multiple output （MIMO） radar transmitting multiple subcarriers signals. How the number of subcarriers in- fluences the estimation accuracy is illustrated by considering the joint Cramer-Rao bound and the mean square error of the maxi- mum likelihood estimate. The non-coherent MIMO radar ambiguity function with multiple subcarriers is developed and investigated by changing the number of subcarriers, the pulse width and the frequency spacing between adjacent subcarriers. The numerical results show that more subcarriers mean more accurate estimates, higher localization resolution, and larger pulse width results in a worse performance of target location estimation, while the fre- quency spacing affects target location estimation little.

MIMO-DCSK communication scheme and its performance analysis over multipath fading channels

The differential chaotic shift keying （DCSK） communication in multiple input multiple output （MIMO） multipath fading chan- nels is considered. A simple MIMO-DCSK communication scheme based on orthogonal multi-codes （OMCs） and equal gain combination （EGC） is proposed, in which OMCs are used to spread the same information bit at each transmitting antenna and the infor- mation bit is detected by EGC at receiving antenna. The OMCs are constructed from one chaotic sequence by means of othogo- nal space-time block coding （OSTBC）. The output signal-to-noise ratio （SNR） after EGC is given based on central limit theory （CLT）, and it can effectively exploit the spatial diversity of the underlying MIMO system. Simulation results show that the full spatial diversity gain is achieved without channel estimation in the MIMO-DCSK communication scheme and it performs better than MC-EGC for a large number of transmitting antennas.

再论Devaney混沌的随机性质

拓扑动力系统相关动力性质(如弱混合、拓扑弱混合、敏感性)之间的关系一直是动力系统研究的主要问题。证明利用相关函数定义的弱混合拓扑动力系统必为拓扑弱混合。以此为基础,得到的系统是multi-敏感的和初值敏感依赖的。从而改进了相关文献的主要结果。

Method of Judging Potential Failure States of Electronic Instruments

Potential failures of electronic instrument are very common in the engineering practice.In this paper,potential failure state model is analyzed based on dynamic characteristics of electronic instrument at work and a comprehensive method of judging multi-state reliability is put forward.Then,a multi-state electronic instrument reliability analysis model is built based on Bayesian Networks(BN).Considering the failure-potential failure-normal work states,the model is built to estimate reliability of the system and the conditional probability of the elements.Finally,the model is proved corrective and effective by examples.

Influences of Catalytic Combustion on the Ignition Timing and Emissions of HCCI Engines

The combustion processes of homogeneous charge compression ignition （HCCI） engines whose piston surfaces have been coated with catalyst （rhodium or platinum） were numerically investigated. A singlezone model and a multi-zone model were developed. The effects of catalytic combustion on the ignition timing of the HCCI engine were analyzed through the single-zone model. The results showed that the ignition timing of the HCCI engine was advanced by the catalysis. The effects of catalytic combustion on HC, CO and NOx emissions of the HCCI engine were analyzed through the multi-zone model. The results showed that the emissions of HC and CO （using platinum （Pt） as catalyst） were decreased, while the emissions of NOx were elevated by catalytic combustion. Compared with catalyst Pt, the HC emissions were lower with catalyst rhodium （Rh） on the piston surface, but the emissions of NOx and CO were higher.

Choice and Changes of Contraceptive Methods after Primiparous Delivery in Shanghai

Totally, 3 701 prim iparousw om en in Shanghaiw ere follow ed up for 15 m onths after delivery to assess their initialand subsequent changes in choice of contraceptive m ethods. Results show ed that 15 m onths after delivery, 95.46of w om en had al- ready used a contraceptive m ethod. The leading firstchoice of contraceptive m ethods am ong urban w om en w asthe condom (50.72) or IUD(29.09), w hile the leading firstchoice am ong ruralw om en w asIUD(56.65) or the condom (30.60). Within 15 m onths after delivery, w om en w hose first choice had been the condom tended to sw itch usually to an IUD. Butfew er w om en w hosefirstm ethod w asan IUD sw itched to other m ethods. Atthe 15th m onth follow -up, 94.54of w om en w ere all using a m ethod, w ith 60.76of urban w om en and 71.07of rural w om en using IUDs. Multinom inal logistic regression analysis suggests that w om en's characteristics influ- ence the choice of m ethods. Urban, w ell-educated w om en w ere m ore likely to choose condom and rhythm , and lesslikely to chooseOC. Older w om en tended to use condom and rhythm m ore often than younger w om en. Breastfeeding w om en w ere lesslikely to use OC. Wom en w ho received recom m endations regarding postpartum contraception from fam ily planning w orkers w ere m ore likely to use IUD. It w as concluded that fam ily planning w orkers should increase w om en's aw areness of the advantages and disadvantagesof differentm ethods, dispelmythsand rum orsaboutsom em ethodsand improve w om en'sknow ledge of inform ed choice.

Drug Discovery Enters A New Era with Multi-Target Intervention Strategy

In the past century, as medical research has become increasingly precise, it has become clear that the incidence and progression of many diseases involve multiple factors and pathologies; this is particularly true for the degenerative and metabolic diseases facing industrialized societies. At the same time, it becomes increasingly clear that single-target action drugs cannot effectively treat these diseases. Researchers are looking toward the chemical industry as well as traditional herbal medicines to find multi-target interventions. Thus, a new era in drug discovery has begun. Specifically, three approaches have proven effective in seeking multi-target drugs. These are： （1） designing drugs with multiple components; （2） discovering drugs through the study of synergistic compound-compound interactions in medicinal herbs or among chemical drugs and herbal components; and （3） developing drugs to tackle complex multi-component diseases. The authors conclude that there is an increasing need for multi-component remedies to treat the complex chronic diseases afflicting modern populations. Given this situation and the growing body of evidence that these new approaches are effective, multi-target intervention appears to have great potential for discovering, designing, and developing effective new drugs for today＇s diseases.

Collaborative Network Security in Multi-Tenant Data Center for Cloud Computing

A data center is an infrastructure that supports Internet service. Cloud comput the face of the Internet service infrastructure, enabling even small organizations to quickly ng is rapidly changing build Web and mobile applications for millions of users by taking advantage of the scale and flexibility of shared physical infrastructures provided by cloud computing. In this scenario, multiple tenants save their data and applications in shared data centers, blurring the network boundaries between each tenant in the cloud. In addition, different tenants have different security requirements, while different security policies are necessary for different tenants. Network virtualization is used to meet a diverse set of tenant-specific requirements with the underlying physical network enabling multi-tenant datacenters to automatically address a large and diverse set of tenants requirements. In this paper, we propose the system implementation of vCNSMS, a collaborative network security prototype system used n a multi-tenant data center. We demonstrate vCNSMS with a centralized collaborative scheme and deep packet nspection with an open source UTM system. A security level based protection policy is proposed for simplifying the security rule management for vCNSMS. Different security levels have different packet inspection schemes and are enforced with different security plugins. A smart packet verdict scheme is also integrated into vCNSMS for ntelligence flow processing to protect from possible network attacks inside a data center network

Atomic Decomposition and Boundedness Criterion of Operators on Multi-parameter Hardy Spaces of Homogeneous Type

The main purpose of this paper is to derive a new （p,q）-atomic decomposition on the multi-parameter Hardy space HP（X1 × X2） for 0 〈 po 〈 P ≤ 1 for some po and all 1 〈 q 〈 ∞, where X1 ×X2 is the product of two spaces of homogeneous type in the sense of Coifman and Weiss. This decomposition converges in both L^q（X1 × X2） （for 1 〈 q 〈 ∞） and Hardy space HP（X1× X2） （for 0 〈 p _〈 1）. As an application, we prove that an operator T, which is bounded on Lq（X1× X2） for some 1 〈 q 〈 ∞, is bounded from H^p（X1 × X2） to L^p（X1 × X2） if and only if T is bounded uniformly on all （p, q）-product atoms in LP（X1 × X2）. The similar boundedness criterion from HP（X1 × X2） to HP（X1 × X2） is also obtained.

Conflict-Resolution in Multi-ES Cooperation System

In the so called “Group Problem” (we would like to term it “Group-Consulting Type Cooperation”), ESs of the same cooperating group may have different views towards the same problem, and the differences may sometimes be very great. For the circumstance of those ESs with relatively closer views, we present in this paper three methods of consistency treatment and a method for calcula- ting the maximal deviation of the confidence value about the cooperating group's common view based on the consistency degree of those different views. For the circumstance of those views being not very close to each other and also not very different from each other, we designed two synthesis functions for synthesizing multiple views. These two circumstances are formally defined in this paper. A comparison be- tween these two functions and the combining function in is also demonstrated. In the last section of this paper, we present a discussion about some further research topics of conflict-resolution in the group problem.

Optimization methods for regularization-based ill-posed problems： a survey and a multi-objective framework

Ill-posed problems are widely existed in signat processing. In this paper, we review popular regularization models such as truncated singular value decomposi- tion regularization, iterative regularization, variational regularizafion. Meanwhile, we also retrospect popular optimiza- tion approaches and regularization parameter choice meth- ods. In fact, the regularization problem is inherently a multi- objective problem. The traditional methods usually combine the fidelity term and the regularization term into a single- objective with regularization parameters, which are difficult to tune. Therefore, we propose a multi-objective framework for ill-posed problems, which can handle complex features of problem such as non-convexity, discontinuity. In this framework, the fidelity term and regularization term are optimized simultaneously to gain more insights into the ill-posed prob- lems. A case study on signal recovery shows the effectiveness of the multi-objective framework for ill-posed problems.

Design of a 0.5 V CMOS cascode low noise amplifier for multi-gigahertz applications

This paper presents the design of 0.5 V multi-gigahertz cascode CMOS LNA for low power wireless communication. By splitting the direct current through conventional cascode topology, the constraint of stacking- MOS structure for supply voltage has been removed and based on forward-body-bias technology, the circuit can operate at 0.5 V supply voltage. Design details and RF characteristics have been investigated in this paper. To verify the investigation, a 0.5 V 5.4 GHz LNA has been fabricated through 0.18 μm CMOS technology and measured. Measured results show that it obtains 9.1 dB gain, 3 dB NF with 0.5 V voltage and 2.5 mW power dissipation. The measured IIP3 is -3.5 dBm. Compared with previously published cascode LNA, it achieves the lowest supply voltage and lowest power dissipation with competitive RF performances.