承船厢吊耳的局部应力分析研究

承船厢是升船机系统中的一个重要结构物,该结构物中的关键结构吊耳是否有足够的强度,应力分布是否合理将直接影响升船机系统工作的可靠性。在对吊耳进行光弹性试验基础上,对吊耳的光弹性模型进行有限元分析,通过结果的分析比较,确定承船厢吊耳的局部结构的计算可靠程度     

垂直加速度对SⅡ型海洋重力仪的影响及消除

根据海洋重力测量的实际情况,结合SⅡ型海洋重力仪的结构特点,分析垂直加速度对SⅡ型海洋重力仪的影响,进而采取强阻尼的措施减弱这种影响,对于测量船实时航行状态操纵,提高作业效率具有很重要的作用。     

Study of total column atmospheric aerosol optical depth,ozone and precipitable water content over Bay of Bengal during BOBMEX-99

The spatial and temporal variations in aerosols and precursor gases over oceanic regions have special importance in the estimation of radiative forcing parameters and thereby in the refinement of general circulation models. Extensive observations of the columnar aerosol optical depth (AOD), total column ozone (TCO) and precipitable water content (PWC) have been carried out using the on-line, multi-band solar radiometers onboard ORV Sagar Kanya (Cruise # SK 147B) over Bay of Bengal during 11th–28th August 1999. Aerosol optical and physical properties (optical depth and angstrom parameter) have been estimated at six wavelengths covering from UV to NIR (380–1020 nm) while TCO and PWC have been determined using the UV band around 300 nm and NIR band around 940 nm, respectively. Added, concurrent meteorological and satellite observations during this field phase of BOBMEX-99 have been utilized to investigate spectral-temporal variations of AOD, TCO and PWC in marine environment. The results indicate lower AODs (around 0.4 at characteristic wavelength of 500 nm) and size distributions with abundance of coarse-mode particles as compared to those aerosols of typical land origin. An interesting result that is found in the present study is the significant reduction in AOD at all wavelengths from initial to later part of observation period due to cloud-scavenging and rain-washout effects as well as signature of coastal aerosol loading. The clear-sky daytime diurnal variation of TCO shows gradual increase during post-sunrise hours, broad maximum during afternoon hours and gradual decrease during pre-sunset hours, which is considered to be due to photochemical reactions. The diurnal variation curve of PWC showed maximum (~ 4 cm) during morning hours and gradual decrease (~ 3.5 cm) towards evening hours, which are found to be greater as compared to typical values over land. Another interesting feature observed is that although the PWC values are very high, there was no proportionate or appreciable enhancement in AOD—a feature that can be utilized to infer composition of aerosols over the study region.     

卫星视频舰船目标检测方法

舰船目标检测是进行海上目标监管,保障海上权益的重要手段.本文在SSD(single shot multibox detector)算法的基础上,利用残差网络(ResNet,residual network)作为骨干网络构建SSD模型,将改进后的SSD算法应用于卫星视频舰船目标检测,该算法采用残差连接替换原本的级联方式,...     

Simulation of Kelvin wakes in optical images of rough sea surface

Kelvin wake is one of the common wakes generated by moving ships and contains rich information about ships. In this paper, free wave elevations of Kelvin wake are calculated based on the Michell thin ship theory combined with a point source perturbation model. The probability density function of sea surface slopes is introduced to calculate the specular reflection of sunlight and skylight and the refraction of scattered light underwater. Satellite-detected Kelvin wakes are then simulated by adding surface specular reflectance and water-leaving reflectance. Simulation results agree well with satellite measurements. The specular reflection of sunlight is the decisive factor affecting the features of Kelvin wakes according to the simulation results. The main factors that influence the specular reflection of sunlight, such as the incident direction and observation direction, ship parameters, and background environment, are discussed. This study is helpful for wake detection and provides a preliminary theoretical method for the retrieval of ship information.     

船舶减纵摇方法研究

针对现有减小船舶纵摇的方法和装置进行总结和分析,并在此基础之上详细介绍一种新型十字型的被动式抗纵摇舵.通过对比分析,抗纵摇舵对于船舶具有明显地减小纵摇的减摇效果.     

Single Particle Analysis of Aerosols, Observed in the Marine Boundary Layer during the Monterey Area Ship Tracks Experiment (MAST), with Respect to Cloud Droplet Formation

The chemical composition of individual particles >0.2 m sampled duringthe MAST-experiment wereanalysed by SEM-EDX, in combination with multivariatetechniques. The objective of this experiment was toidentify the mechanisms responsible for themodification of marine stratocumulus clouds byemissions from ships and in a wider sense to provideinformation on the global processes involved inatmospheric modification of cloud albedo. Aerosolswere examined under different MBL pollution levels(clean, intermediately polluted and moderatelypolluted) in five different reservoirs: backgroundbelow-cloud and above-cloud aerosol; background clouddroplet residual particles; below-cloud ship plumeaerosol and ship track cloud droplet residualparticles.In this study a relation was provided between theaerosol emitted from the ship's stack to an effect incloud. Additionally, a large fraction of the ambientaerosol was found to be composed of organic materialor other compounds, consisting of low Z-elements,associated with chlorine. Their number fraction waslargest in clean marine boundary layers, and decreasedwith increasing pollution levels. The fraction of`transformed sea salt' (Na, Cl, S), on the other hand,increased with the pollution level in the MBL. Only20% of the particles fell within the detectable rangeof the analysis.     

Design of the roll stabilization controller, using fin stabilizers and pod propellers

Ships experience roll motion due to waves in a seaway. Therefore, fin stabilizers are installed to stabilize such roll motion. A fin stabilizer is effective at reducing the roll motion at moderate speeds but not at low speeds. Recently, pod propellers have been used with fin stabilizers for roll stabilization. In the paper, a MIMO (multi-input multi-output) optimal control system that has two control inputs such as fin stabilizers and pod propellers is designed. The LQR (linear quadratic regulator) control algorithm is applied to reduce the roll motion of cruise ships in regular waves. Also, the nominal plant and the frequency-weighted LQR are applied to reduce the roll motion in irregular waves. The roll motion of cruise ships is effectively reduced when the fin and pod propeller are used as the control actuators at low speeds. The optimal control gain is easily found when the frequency-weighted LQR is applied.     

水下运动源内波尾迹海面作用量谱扰动分析

应用作用量守恒理论,对二维作用量谱平衡方程的波流作用机理及源(汇)函数进行分析,并对水下运动源内波尾迹在自由面(水面)形成的辐聚和辐射流场引起的作用量谱扰动进行了数值仿真,模拟出不同的配置条件下作用量谱扰动可能存在的"不对称性"。根据海面微波散射及雷达海面成像理论及作用量谱扰动的数值仿真结果,认为内波尾迹雷达散射的不对称可能是源自于作用量谱扰动的"不对称性"。