深潜救生艇的现状及发展趋势

本文首先介绍了潜艇失事后的各种救援方式,并结合目前世界各国所拥有的深潜救生艇和存在的问题,分析了深潜救生的技术现状,并基于国际援救界的形势预测了其发展趋势,即REMORA救生潜器的作业模式将逐渐取代现有的深潜救生模式.     

Numerical investigation of concrete-filled double skin steel tubular (CFDST) structure subjected to underwater explosion loading

With the increasing applications in the offshore industry such as oil and gas jackets, submarine pipelines and wind turbine foundations, concrete-filled double skin steel tubular (CFDST) structures are encountering the ever-increasing risk of threats to underwater explosions (UNDEX). This study presents a systematical investigation on the structural behaviors and design recommendations of the CFDST structures subjected to UNDEX loadings through finite element analysis (FEA) approaches. Finite element models have been developed, where the non-linear material properties of the constitutive steel and concrete parts and the composite actions in-between have been considered. The FEA models are verified against the experimentally determined shock wave pressure history, the deformation shapes, and the residual strength. The full-range analyses were firstly carried out on the structural responses of CFDST structures, including the typical damage patterns and residual strength of the specimen after UNDEX. Then, the parametric studies show that the cross-section hollow ratio, charge weight, and explosion distance play great roles in determining the residual strengths. Thereafter, damage indexes considering the parameter of the hollow ratio and the scaled explosion distance has been formulated, and design recommendations have been suggested accordingly.     

关于自治水面艇导航控制的探索研究

通过对自治水面艇在各领域的应用以及当今国内外研究现状的介绍,出于自治水面艇非线性特征,在模糊控制技术的指导下,提出了模糊控制自治水面艇的导航控制理念,并对在未来的研究当中如何进一步改善和发展自治水面艇作了分析和展望,自治水面艇在不久的将来无疑更引起大家的关注。     

国六轻型车排气污染物中甲烷的不确定度评定

本文介绍了汽车排气污染物中甲烷的生成机理,阐明了甲烷排放的危害和测量的必要性,在评定其不确定度的过程中,按GB18352.6-2016《轻型汽车污染物排放限值及测量方法(中国第六阶段)》中Ⅰ型试验流程开展试验,对底盘测功机和稀释采样系统等设备、环境条件、标准物质、人为操作等可能会影响排放结果的因素进行了评估,计算排气污...     

Turbulence in coastal fronts near the mouths of Block Island and Long Island Sounds

Measurements of turbulence were performed in four frontal locations near the mouths of Block Island Sound (BIS) and Long Island Sound (LIS). These measurements extend from the offshore front associated with BIS and Mid-Atlantic Bight Shelf water, to the onshore fronts near the Montauk Point (MK) headland, and the Connecticut River plume front. The latter feature is closely associated with the major fresh water input to LIS. Turbulent kinetic energy (TKE) dissipation rate, ε, was obtained using shear probes mounted on an autonomous underwater vehicle. Offshore, the BIS estuarine outflow front showed, during spring season and ebb tide, maximum TKE dissipation rate, ε, estimates of order 10^− 5 W/kg, with background values of order 10^− 6 to 10^− 9 W/kg. Edwards et al. [Edwards, C.A., Fake, T.A., and Bogden, P.S., 2004a. Spring–summer frontogenesis at the mouth of Block Island Sound: 1. A numerical investigation into tidal and buoyancy-forced motion. Journal of Geophysical Research 109 (C12021), doi:10.1029/2003JC002132.] model this front as the boundary of a tidally driven, baroclinically adjusted BIS flow around the MK headland eddy. At the entrance to BIS, near MK, two additional fronts are observed, one of which was over sand waves. For the headland site front east of MK, without sand waves, during ebb tide, ε estimates of 10^− 5 to 10^− 6 W/kg were observed. The model shows that this front is at the northern end of an anti-cyclonic headland eddy, and within a region of strong tidal mixing. For the headland site front further northeast over sand waves, maximum ε estimates were of order 10^− 4 W/kg within a background of order 10^− 7–10^− 6 W/kg. From the model, this front is at the northeastern edge of the anti-cyclonic headland eddy and within the tidal mixing zone. For the Connecticut River plume front, a surface trapped plume, during ebb tide, maximum ε estimates of 10^− 5 W/kg were obtained, within a background of 10^− 6 to 10^− 8 W/kg. Of all four fronts, the river plume front has the largest finescale mean-square shear, S² ~ 0.15 s^− 2. All of the frontal locations had local values of the buoyancy Reynolds number indicating strong isotropic turbulence at the dissipation scales. Local values of the Froude number indicated shear instability in all of the fronts.     

设计参数对水下机械手控制机构性能的影响

为研究设计参数对水下机械手的控制及操作性能的影响,以水下液压机械手单关节执行机构为研究对象,确定了下机械手的初始参数;基于流量连续性方程及力平衡方程,建立活塞输出位移对阀输入位移的传递函数以及负载力扰动的传递函数,并以速度放大系数,液压固有频率及液压阻尼比作为水下机械手控制机构的性能指标,详细分析各设计参数对水下液压机械手控制机构性能的影响。研究表明：减小控制阀的位移,增大弹性模量,减小控制阀两端的压差,可以改善控制机构的响应速度和稳定性,提高机械手的控制和操作性能。     

水下航行体机械噪声的工程预报方法

本文针对机械设备、隔振装置、基座、壳板以及水介质组成的声学系统,讨论了机械设备传输给壳体的结构声功率,以及计算结构声功率所涉及的设备振动强度——自由速度、隔振装置的传递函数和基座面阻抗。又综述了给定输入声功率下,壳体振动响应空间均方值的计算方法,以及辐射效率和模态密度的估算公式,形成了航行体机械设备产生的水下噪声的全过程预报方法,并对第一个环节得出了开展相关研究的建议。     

一种新的鱼雷垂直命中目标的制导方法

该文针对鱼雷采用前视角声纳和旁视声纳识别和跟踪目标,引入了初始导引段跟踪虚拟目标的概念,提出一种新的精确制导方法,给出了导引跟踪和垂直命中弹道的数学模型。经仿真和分析表明：该制导方法对攻击目标的初始态势几乎没有限制,即使目标为逃避攻击进行转向机动,也能垂直命中目标。     

车联网环境对城市快速路驾驶安全的影响评价

为明确不同情形下车联网对城市快速路交通安全的影响程度,首先,在分析车联网对快速路驾驶行为影响的基础上,对车联网和常规驾驶环境下的驾驶模型参数进行了标定;然后,选取累计碰撞时间（Time Exposed Time-to-collision, TET）和积分碰撞时间（Time Integrated Time-to-collision,TIT）指标对快速路纵向驾驶行为进行安全评价,选取侧向碰撞风险（Sideswipe Crash Risk, SSCR）作为快速路横向换道驾驶安全的评价指标;最后,基于VISSIM设计快速路进行仿真试验,考虑车联网和常规驾驶环境,研究不同渗透率和饱和度条件下网联车对纵向追尾和横向换道驾驶行为的安全影响程度。研究结果表明：车联网环境下网联车渗透率对快速路驾驶行为的影响呈现出缓慢提升（0～50%）、快速提升（50%～75%）及显著提升（75%～100%）三阶段,其中TET指标分别对应降低14.57%, 30.10%和49.01%;车联网环境下,交通饱和度对快速路的交通安全影响则呈现出先快后慢的改善趋势。当网联车渗透率超过75%之后,交通安全提升程度最为明显;车联网环境中,当快速路交通饱和度低于0.8时,交通安全改善程度更为显著。     

基于激光雷达的SLAM和融合定位方法综述

基于激光雷达的同步定位和建图(SLAM)及融合定位技术是无人驾驶的关键技术.激光雷达可以从环境中获取精确的距离及强度信息,被广泛应用于高精度地图构建及基于地图的匹配定位,可有效增强基于卫星定位在弱GNSS区域的鲁棒性.基于当前无人驾驶背景下激光SLAM及融合定位方法的研究现状,对应用于无人驾驶车辆的激光SLAM和融合定...