A comprehensive general simulation of small twin screw displacement hull boats with validation

A comprehensive general simulation of small twin screw displacement hull boats is developed as a tool to estimate ship and actuator responses in support of developing and tuning of control systems. The general form of this model allows many small displacement hull vessels to be rapidly simulated by specifying a set of 17 vessel parameters. The response of the vessel in the surge, sway and yaw degrees of motion are estimated from parametric equations and data compiled from literature and, when not found in literature, inferred from sea trials. Model validation and tuning of the coefficients not found in literature is accomplished using manoeuvring and response data obtained in a series of sea trials. The parametric model proved to be accurate and, when compared with the sea trial data, model estimates have rms errors over the vessel operational range of 0.09 m/s and 0.02 m/s for surge velocity when moving in a straight line in forward and reverse, respectively. For rotating on a fixed point, the simulation overestimates the rotational velocity by 7.6% and has an rms error of 0.27°/s. Open loop circle tests show that with both propellers rotating at 580 rpm, the simulated vessel has a minimum turning radius of 24.4 m and can complete a circle in 44 s, which is 18% smaller and 8% faster than during sea trials. Simulated rotation with the engines in opposite gears at similar RPMs of 500 result in a complete revolution in 68 s, 3 s faster than during sea trials.     

An eco-friendly efficient extractor

A microscale solid-liquid Pyrex extractor is described. The extractor has a novel detachable extraction vessel (H) containing a filter paper cylinder (C) over the reservoir. A filter paper cylinder (C) is firmly placed in the socket (E) with a plug (G) on which the cylinder has been placed. The sample is directly weighed in the extraction vessel (H) and the vessel is clamped (F) to the body (B). Contents in the extraction reservoir (H) are stirred (I) with a magnetic stirrer (J) and heated sufficiently (e.g. at 84.8 °C in using water) by the solvent vapor (D). Easy filtration (C) and continuous outflow (D) of the filtrates out of the reservoir (H) keeps a stable boiling condition (K), rather than batchwise conditions operative in a Soxhlet; this results in rapid and exhaustive extraction. The present extractor (8.0 mL extraction reservoir (H) capacity) equipped with a 25 mL solvent flask (K) was applied to fat extraction from powdered peanut by using 18 mL of ether. The extraction was complete in 30-60 min depending on reflux rate; in contrast, extraction with a commercial micro-Soxhlet device (23.9 mL extraction reservoir capacity) equipped with a 25 mL flask by using 34 mL of the solvent was incomplete in 120 min. Unlike filter paper thimbles used in Soxhlet devices, filter paper cylinder (C) in the new extractor could be reused many times and results in significant savings of the filter paper cylinders. Small reservoir and flask capacities of the new extractor minimize the use of organic solvents. The present apparatus permits fast and efficient extraction, sharply reduces waste, minimizes solvent consumption, and thus should find wide use aiming at the Green Solutions to Global Problems.     

Endothelium-derived Relaxing Factor Activates Calcium-activated Potassium Channels of Resistance Vessel Smooth Muscle Cells

Direct observation was made by using the patch-clamp technique with a specially designed microperfusion system to investigate the effect of acetylcholine (Ach 10~(-6) mol/L) elicited endothelium-derived relaxing factor (EDRF) on the calcium-activated potassium channel (IK(Ca))in the smooth muscle cells of mesenteric resistance vessels in Wistar rats. Activation of IK(Ca) was firstly observed by inducing the elicited EDRF or sodium nitroprusside (SNP 10~(-8) mol/L) under various clamping voltages in cell-attached configuration. While the pipette solution contained KCl 126 mmol/L and the bath solution contained KCl 5.9 mmol/L, two types of conductances of calcium-activated potassium current being 76.4±2.3 pS(mean±S.E. n = 7) and 160.3±7.5 pS (mean±S.E. n= 7) were recorded during the EDRF activation, one type of conductance being 100.5±2.8 pS (mean±S.E. n = 6) was activated by nitric oxide (NO) which is an effective component from SNP. Differences in kinetic characteristics of these channels between     

Membrane solid-phase extraction with closed vessel microwave elution for the determination of phenolic compounds in aqueous matrices

Preconcentration of phenolic compounds was carried out with Empore C₁₈ membrane disks, which were eluted with a closed-vessel microwave extraction system. The optimum microwave-elution conditions were obtained by optimizing the elution solvent, elution temperature, duration of elution and volume of elution solvent. The recoveries of eleven phenolic compounds spiked at 10 and 500 g/L levels into water, using the optimum conditions, were all above 85% with relative standard deviations between 4.0 and 10.0%, except for phenol and 4-nitrophenol. Extraction of an industrial waste water sample suspected of containing phenolic compounds by SPE-CVME showed similar recoveries of phenol (the only phenolic compound detected) when compared with LLE and C₁₈ SPE cartridge techniques. Analysis of phenolic compounds was carried out using liquid chromatography coupled to a UV detection system.     

微量元素与脑血管疾病的关系

报道了９７例脑血管疾病患者血清中铜、锌、锂、硒等四种微量元素含量的测定，并设立对照组５０例，用以探索这些元素与脑血管疾病发病之间的关系，观察结果发现两组血清微量元素含量不同，疾病组明显低于对照组，呈现高度显著性差异。     

肌型血管生物数学模型的非线性状态反馈同步

用非线性状态反馈方法研究肌型血管生物数学模型的同步问题,利用驱动系统与响应系统的误差信号,通过施加反馈控制,设计一个单变量非线性反馈控制器,使响应系统跟踪驱动系统,即误差系统渐近稳定到平衡点,从而实现了两个混沌系统在单变量驱动的情况下,消耗更少的能量达到同步,从理论上验证了处于痉挛状态下的血管运动可以与正常血管运动同步,为有效防治和治疗心肌梗塞等疾病提供一定的理论依据.仿真结果表明了此方法的有效性.     

基于相似性测度和似然模型的血管造影图像分割新方法

由于造影图像中的血管具有复杂的形态结构,经典的基于跟踪的一类方法在进行分割时容易丢失目标,因此其自动化程度和鲁棒性受到了严重的影响。提出了一种鲁棒的最大似然血管跟踪模型,该模型是建立在多种局部相似性测度和智能知识引导的基础上的,能够精确估计出血管轴线,并能正确判断分支点位置。实验结果表明,该模型具有很高的稳定性,能够为血管三维重建和临床诊断提供正确的依据。     

摄像测量在舰船变形测量中的应用研究

针对舰船不同安装基座间相对变形的高精度测量要求,提出了一种利用单摄像机三维姿态测量原理和亚像素定位法,通过若干台摄像机进行传递测量船体变形的方法,来解决对两个或多个不通视安装基座之间相对变形进行高精度测量的问题。分别对单摄像测量和多级摄像传递测量进行了测量精度分析,采用4台2K×2K分辨率的摄像机进行传递测量,测量精度优于23″。该方法在舰船上较易实施,且精度较高。     

Structural and acoustic responses of a fluid-loaded cylindrical hull with structural discontinuities

This paper studies the low frequency vibrational behaviour and radiated sound of a submarine hull under axial excitation. The submarine is modelled as a fluid-loaded cylindrical shell with internal bulkheads and ring-stiffeners and closed at each end by circular plates. A smeared approach is used to model the ring stiffeners. The external pressure acting on the hull due to the fluid loading is calculated using an infinite model and is shown to be a good approximation at low frequencies. The radiated sound pressure is obtained by considering the finite cylindrical hull to be extended by two semi-infinite rigid baffles. The sound pressure is then only due to the radial displacement of the cylindrical shell, without taking into account the scattering at the finite ends. The main aim of this paper is to observe the influence of the various complicating effects such as the bulkheads, ring-stiffeners and fluid loading on the structural and acoustic responses of the finite cylindrical shell. Results from the analytical models presented in this paper are compared to the computational results from finite element and boundary element models.     

弹／粘塑性压力容器的塑性失稳破坏

依据压力容器拉伸塑性失稳破坏特征,计算了旋转薄壁壳压力容器在弹/粘塑性材料下的塑性失稳破坏,文中就圆柱壳形、圆球壳形、抛物线壳形封头等压力容器的失稳状态,分别求出它们的应力应变。