一种精确的水声通信时间同步信号设计

提出了采用HFM（Hyperbolic Frequency Modulation,HFM）和CW（Continuous Wave,CW）构成的组合信号,实现精确的时间同步。根据HFM信号的匹配相关捕获同步信号,由CW信号的ZoomFFT算法估计Doppler扩展,再根据Doppler扩展的估计补偿时间同步误差。     

基于Lorenz混沌调频的水下正交波形集设计

针对网络水下航行器组联合探测情况下各网络节点间信号会互相干扰的问题,基于Lorenz混沌模型,提出一种混沌调频(Chaos Frequency Modulation,CFM)的正交波形集设计方法。首先建立基于Lorenz序列的CFM信号模型,对其进行相关特性分析和正交特性研究,包括CFM正交波形集的个数和波形长度对波形集正交性能的影响,提出对混沌序列进行加窗函数处理的CFM波形集正交性优化方法;然后构造网络水下航行器组分别发射线性调频(Linear Frequency Modulation,LFM)信号和CFM信号的回波模型,对比分析了匹配滤波器对回波信号的处理结果。仿真结果表明,该设计方法简便、灵活、高效,产生的CFM正交波形集性能良好,且相对于常规信号在水下信号检测方面具有明显的优势。     

基于分数阶功率谱熵的未知水声脉冲信号检测方法

水声侦察的核心问题是在无先验知识条件下捕获其他平台发射的脉冲信号,单频（Continuous Wave,CW）信号和调频（Frequency Modulation,FM）信号是常用的水声探测脉冲。功率谱熵算法能有效检测低信噪比的CW信号,但对FM信号性能不佳,分数阶傅里叶变换（Fractional Fourier Transform,FRFT）则能聚集FM信号能量。利用FRFT的性质,结合功率谱熵算法,设计了分数阶功率谱熵检测器,可在分数阶域实施未知脉冲信号检测。理论分析了FRFT对FM信号的能量聚集作用,优化了FRFT阶数搜索方法。仿真实验以及海试数据处理结果证实检测器对FM信号性能良好,且对CW信号的侦察检测性能无影响。通过门限学习,检测器可实现对未知水声脉冲信号的统一自动检测。     

基于Matlab的LFM脉冲压缩仿真

基于Matlab平台以线性调频信号为例通过仿真研究了雷达信号处理中的脉冲压缩技术。在对线性调频信号时域波形进行仿真的基础上介绍了数字正交相干检波技术。最后基于匹配滤波算法对雷达回波信号进行了脉冲压缩仿真,仿真结果表明采用线性调频信号可以有效地实现雷达回波信号脉冲压缩,提高雷达的距离分辨力。     

遗传算法在分数阶Fourier变换域极值优化中的应用

分数阶Fourier变换采用线性调频基,因此,线性调频（Linear Frequency Modulation,LFM）信号在分数阶Fourier域平面能够聚焦,并形成峰值。为了克服传统步进式搜索法在LFM信号峰值搜索中效率低下的缺点,将遗传算法引入到分数阶Fourier变换极值搜索中。仿真结果表明,该方法优于传统的步进式搜索法。     

毫米波调频步进雷达运动补偿方法研究

毫米波调频步进（chirp-step frequency , Chirp-SF）雷达是一种距离高分辨率雷达,但是存在严重的距离 速度耦合问题,所以实现运动目标的距离高分辨必须进行运动补偿。文章提出了一种把脉冲多普勒（Pulse Doppler）测速和基于Chirp-SF信号的时域相关法测速相复合的方法。仿真结果表明该方法测速精度高,算法简单,速度快。     

连续波声呐中的调频信号设计方法及性能分析

相对传统的短时脉冲波主动声呐而言,连续波主动声呐是一种新型体制的声呐设备,允许在扫描周期内发射高占空比的信号,并且在发射信号的同时进行侦听,由此可以对水下目标实现连续照射,消除距离盲区。由于发射和接收机制的不同,连续波主动声呐对发射信号的波形和处理方法也各有差异,一是要考虑到"直达波"抑制问题,二是要在时间带宽积和对目标的照射时间间隔两者之间进行折中。针对上述两个问题,设计了一种在连续波主动声呐中发射的新型脉冲串信号,该类信号由多个相互正交的广义正弦调频信号串组成,以此在频域上消除回波与拷贝信号的相关性;后置处理中对接收回波提供了三种不同的方案,在时间带宽积和照射时间间隔两者之间择优选择最佳检测效果。计算机仿真结果表明:该类信号波形以及相应的处理方法可以有效地抑制直达波干扰并给出目标的速度-距离信息。     

一种多普勒宽容的多址波形

提出了一种具有多址特性、对多普勒宽容的主动波形．HFM-Costas波形。这种波形是通过将宽带双曲调频波形在时间上切分为子脉冲,再根据Costas阵列编码重新排列而成．它结合了Costas编码的多址特性和双曲调频信号的多普勒宽容性。这种波形适于采用相干．非相干混合接收机进行处理,接收机结构简单,计算量小,检测鲁棒性好。详细说明了这种波形的生成方法、相应混合接收机结构,并分析了该波形的主要特性。最后．通过湖上试验进行了验证。     

基于双曲调频距离误差的目标跟踪修正算法

双曲调频信号的多普勒不变性可使运动目标匹配滤波输出的能量损失达到最小，在运动目标检测与参数估计中具有独特优势，已广泛应用于新型主动声呐。然而其多普勒不变性在提高检测能力的同时，会引入目标距离估计误差，从而影响主动声呐跟踪性能。文章在分析双曲调频信号距离估计误差的基础上，提出了目标跟踪算法的误差修正方法，通过将距离估计误差公式与传统观测方程及滤波算法进行融合，实现目标跟踪算法的误差补偿，显著提高了算法的跟踪性能，尤其是对快速运动目标的跟踪性能。     

基于瞬时频率的双曲调频信号距离估计误差分析

双曲调频信号的多普勒不变性可使运动目标匹配滤波输出的能量损失达到最小,从而可对运动目标有很高的检测能力,在运动目标检测与参数估计中具有独特优势,但同时也给目标距离的估计带来一定误差。在双曲调频信号模糊函数、多普勒不变性和匹配滤波特性的基础上,对距离分辨力和测距误差进行了分析,提出了基于瞬时频率的距离误差计算公式,可直接应用于目标距离的补偿以及目标跟踪中量测方程的校正,提高声呐的工作性能。     

凝固科学技术与材料

从凝固科学与实践发展的角度介绍了当前凝固材料体系的基本框架和凝固科学主要发展阶段的基本理论。作为材料科学与工程的基本组成，凝固科学技术正在现代科学理论的基础上针对传统材料的改性提高和新材料的发展需求，以控形、控构、控性为目标开展优质铸件的定向、晶体生长、快凝、深过冷及各种新型和超常领域凝固过程的研究，并介绍了其中某些方面和展望了可能的发展趋势。     

Development and challenges of planning and scheduling for petroleum and petrochemical production

Production planning and scheduling are becoming the core of production management, which support the decision of a petrochemical company. The optimization of production planning and scheduling is attempted by every refinery because it gains additional profit and stabilizes the daily production. The optimization problem considered in industry and academic research is of different levels of realism and complexity, thus increasing the gap. Operation research with mathematical programming is a conventional approach used to address the planning and scheduling problem. Additionally, modeling the processes, objectives, and constraints and developing the optimization algorithms are significant for industry and research. This paper introduces the perspective of production planning and scheduling from the development viewpoint.     

The Candela and Photometric and Radiometric Measurements

The national measurement system for photometric and radiometric quantities is presently based upon techniques that make these quantities traceable to a high-accuracy cryogenic radiometer. The redefinition of the candela in 1979 provided the opportunity for national measurement laboratories to base their photometric measurements on optical detector technology rather than on the emission from high-temperature blackbody optical sources. The ensuing technical developments of the past 20 years, including the significant improvements in cryogenic radiometer performance, have provided the opportunity to place the fundamental maintenance of photometric quantities upon absolute detector based technology as was allowed by the 1979 redefinition. Additionally, the development of improved photodetectors has had a significant impact on the methodology in most of the radiometric measurement areas. This paper will review the status of the NIST implementation of the technical changes mandated by the 1979 redefinition of the candela and its effect upon the maintenance and dissemination of optical radiation measurements.     

江澳两地高校文创设计的协同研究与商业实践

目的 探索江门世遗文化的传承、发展和转化的新思路,践行国家在《粤港澳大湾区发展规划》纲要中要求江门承担与港澳地区文化创意合作与开发任务的分工。方法 与澳门高校紧密合作,开展专业培训课程,以开平碉楼为例,从人文视角开展设计研究,梳理开平碉楼的文化脉络,把世遗文化的元素和其背后的文化融入文创产品中,提升文创产品的附加值,推动当地文创产业结构的变革。结果 两地高校构建了稳定的科研团队,开设长期有效的设计培训课程,与景区建立了研究协作关系,帮助景区构建了一套产销研的商业模式。结论 以跨区域高校合作为平台,以文创产品为抓手,依托江澳两地的资源优势,可以构建江门世遗文化全新的品牌形象,最终推动开平世遗文化的活化。     

PSD和PWELCH函数的分析改进及应用

针对MATLAB中两个内建功率谱密度计算函数psd()和pwelch()计算结果迥异的现象,在功率谱密度估计理论的基础上,根据经典的周期图理论和Welch平均周期图方法,通过详细分析源程序,解析计算方法,发现psd()计算的并不是工程单边功率谱密度,而是采样信号双边谱,故与pwelch()结果迥异,另外pwelch()不能对分段信号数据进行预处理。就上述不足提出了相应的改进措施,比较验证表明改进措施行之有效。     

Creation and motion of dislocations and fracture in metal and silicon crystals

By making a step on one surface ( ) of a rectangular small paralellepiped copper crystal, dislocations could be created by the molecular dynamic method. The dislocation created was not a complete edge dislocation but a pair of Heidenreich-Shockley partial dislocations. Each time a dislocation was created, the stress on the surface was released. Small copper crystals having a notch were pulled (until fracture), compressed and buckled by use of the molecular dynamic method. An embedded atom potential was used to represent the interaction between atoms. Dislocations were created near the tip of the notch. A very sharp yield stress was observed. The results of high speed deformations of pure silicon small crystals using the molecular dynamics are presented. The results suggest that plastic deformation may be possible for the silicon with a high speed deformation even at room temperature. Another small size single crystal, the same size and the same surfaces, was compressed using molecular dynamic method. The surfaces are {110}, {112} and {111}. The compressed direction was [111]. It was found that silicon crystals are possible to be compressed with a high speed deformation. This may suggest that silicon may be plastically deformed with high speed deformation.     

Miniature and MEMS-type vacuum sensors and pumps

In the paper, the observable trends of the actual research and development of selected types of miniature and MEMS-type vacuum sensors are presented. Some information about the new types of active vacuum gauges, which are offered by the leading manufacturers of the vacuum measurement instruments, is given. Next, the list of MEMS devices that need vacuum for proper operation is presented. Some aspects of vacuum-encapsulation of MEMS devices, on wafer level and package level are shown. The new conceptions of obtaining and maintenance of high and ultra-high vacuum in MEMS devices are described. They concern the conception of integration of a miniature orbitron pump on-chip with MEMS-type device or with vacuum part of the portable advanced instruments such as electron microscope, ion mass spectrometer, and free electron laser.     

Density and viscosity of tetralin and trans-decalin

New measurements are reported for the density and viscosity of tetralin and trans-decalin. The density was determined from room temperature to 60°C for tetralin and to 95°C for trans-decalin. The kinematic viscosity was measured up to temperatures slightly above 100°C. Our results improve upon the values recommended by the American Petroleum Institute for these liquids.