水下爆炸船体结构响应间断伽辽金法数值模拟

为求解水下爆炸强间断流场,采用Level Set方法定位多相流界面位置,应用虚拟流体方法处理邻近界面两侧物理量,并用RKDG方法进行空间和时间的离散,求解流场的Euler方程,并进行一维、二维评价,计算结果能够较好地反映水下爆炸冲击波产生、传播、反射和爆炸产物的膨胀等现象.最后,结合大型非线性有限元软件ABAQUS,模拟了船体板在水下爆炸载荷作用下的变形和响应特征.模拟结果表明,间断迦辽金法能够实现对水下爆炸船体结构响应精确模拟,板架结构响应与爆心距离成反比.     

Trajectory Simulation for Underwater Vehicle with Power-Lunched

The motion of combustion gas bubble produced by underwater ignition was developed based on Rayleigh-Plesset equation. Combining the bubble motion equation with the underwater launched vehicle motion equation in the longitudinal plane, a trajectory simulation model with power-launched was established. The hydrodynamic characteristics of underwater ignition at different depths and the trajectory analysis of the underwater vehicle with power-launched were given by simulation. The simulation results have a good agreement with experimental results, and show that the thrust peak caused by underwater ignition and the stable thrust both decrease slightly with the increase of the water depth, and the thrust peak will decline obviously by enlarging the initial radius of gas bubble; the thrust peak generated at the instant of ignition and the low-frequency oscillation of the stable thrust have no significant influence on the trajectory of underwater vehicle.     

Head Orientation Stability of Underwater Snake-Like Robot Swimming

In prior research,the orientation of head of the snake-like robot is changed according to the sinusoidal wave. To solve this problem,we propose Central Pattern Generator( CPG)-based control scheme with head-controller to stabilize the head of the underwater snake-like robot. The advantage of the CPG-based control scheme with head-controller is that the head of the underwater snake-like robot is direct to the target orientation during swimming. The relation between CPG parameters and orientation stability of head is discussed.The adaptation of the proposed method to environment changes is tested. The influences of CPG parameters and hydrodynamic forces on the orientation offset of head are investigated. The target orientation( the input of headcontroller) with an experimental optimization is calculated through a convenient method. To prove the feasibility of the proposed methodology,the different swimming modes have been implemented in our simulation platform.The results show that the oscillation of head’s orientation is inhibited effectively,and the proposed method has strong adaptation to environment and CPG parameters changes.     

基于灰度化权值调整的水下彩色图像分割

针对传统自适应阈值法在水下图像分割过程中存在目标与背景粘连等问题,提出一种基于灰度化权值调整的水下彩色图像分割方法。区别于传统阈值分割方法中灰度化权值固定且研究如何确定合适阈值的思路,研究灰度化权值调整方法。本文方法利用统计得到的图像灰度信息来确定不同通道内目标与背景间灰度级差异性的大小,提高差异性较大通道的比例,以增强灰度化后图像中目标与背景的对比度,同时减小差异性较小通道的比例,以降低其对灰度化结果的干扰,对灰度化后的图像进行阈值分割得到最终分割结果。针对水下作业的时序列图像,设计了两步序列图像处理方式来降低耗时。通过4组水下对比实验以及耗时实验对方法的有效性进行了验证。     

水下滑翔机李雅普诺夫稳定性分析

水下滑翔机作为一种新型的水下机器人利用了水平固定翼将净重力转换为前进驱动力,从而降低了水下机器人的功耗,在海洋科学研究、环境监测、资源探测和军事侦察等方面都具有广阔的应用前景。为了得到实际水下滑翔机稳定性与设计参数和控制参数之间的关系,将已建立的水下滑翔机一般数学模型应用于具体的实际水下滑翔机上。在此基础上将模型线性化,结合李雅普诺夫稳定性第一定理和第二定理,分析出水下滑翔机定常运动的动态稳定性随设计参数(初稳性高)和控制参数(姿态调节控制量)变化的规律。为水下滑翔机器人的设计和控制提供理论依据。     

水下火箭弹头部空化流场的数值仿真研究

对火箭弹头部的局部空化流场的研究可作为头部敏感装置安装位置设计和选择的依据。研究了利用RANS(针对定常分析)和LES(针对非定常分析)湍流模型对水下火箭弹弹体头部空化流场进行仿真分析的方法,并与实验结果进行对比验证。通过仿真分析了在零攻角/小攻角下弹体头部周围定常、非定常流场空化区域和不同速度、加速度下空化区的变化;比较了相同空化数下不同速度对空化区域的影响。结果发现,小攻角情况下的火箭弹头部背流面空化流场存在较强的非定常特性,头部流场空化区受到加速度的影响且存在速度比尺效应。     

AUV水声跳频通信调制解调器的设计与实现

在复杂时变水声通信环境中非相干FH-FSK调制解调技术是一种较为稳健、可靠的通信方式,适合于低速、高可靠的水声设备遥控等应用场合,如水面船遥控高速运动的水下智能机器人(autonomous underwater vehicle,AUV)。但也面临着以下困难:1)高速运动带来的多普勒会严重恶化通信系统性能;2)为节省能耗,AUV依据通信需求可对通信单元进行经常性的上电与断电操作,导致异步单工工作模式下水面与水下通信节点之间很难协调工作。针对以上问题,提出了采用脉冲对技术进行可靠多普勒估计,并采用线性插值技术进行高效多普勒补偿;结合通信节点板载高精度时钟以及设计的声链路同步机制有效地解决了AUV和水面控制船之间的双向链路建立与数据传输工作。基于OMAP-L138双核处理器平台设计与实现了FH-FSK的水声调制解调器的样机,湖上实验结果表明提出的传输控制协议可保证通信节点之间的通信链路随机建立和断开,结果证明所设计的样机稳定、可靠。     

对联合战役装备保障训练考核评估问题的思考

考核评估是联合战役装备保障训练的关键环节之一,对于提高联合战役装备保障训练质量、推动联合战役装备保障训练健康发展具有重要意义。分析了联合战役装备保障训练考核评估存在的主要问题,提出了联合战役装备保障训练考核评估的基本思路,构建了联合战役装备保障训练考核评估指标体系,阐述了联合战役装备保障训练考核评估的实施方法。     

A general framework and optimization models for the scheduling of continuous chemical processes

We present a framework for the formulation and solution of continuous process scheduling problems. We focus on modeling transient operations such as startups, shutdowns, and transitions between steady states. First, we show how the concept of processing tasks can be generalized to represent continuous processes, including their transient operations. Second, we discuss how to systematically calculate the parameters describing material consumption/production and utility consumption during transient operations. Finally, we present new mixed-integer linear programming formulations for the scheduling of continuous chemical production.     

Optimizing the use of dry cutting in rough turning steel operations

The main objective of using cutting fluids in machining operations is the reduction of temperature in the cutting region to increase tool life. However, the advantages offered by cutting fluids have been strongly debated because of their negative effects on the economic aspect, the environment and the health of workers using them. A trend to solve these problems is cutting without fluid, a method named dry cutting, which has been made possible due to technological innovations. This work aims to seek conditions in which dry cutting is satisfactory compared with the flood of fluid (called here wet cutting) usually used. Aiming at this goal, several experiments were carried out varying parameters such as cutting speed, feed, depth of cut and tool material in rough turning of ABNT 1045 steel in dry and wet cutting. The analysis of the results showed that wet turning is, as expected, better for tool life. The second conclusion is that dry cutting cannot be used with large depth of cut. But the main conclusion is that, if the tool material is changed to a more wear resistant one, dry cutting can be used with results very similar to those obtained with a flood of fluid.