VEGETATION植被指数数据预处理方法

VEGETATION数据的植被指数,受云雾影响,含有大量的噪声信号,使用之前必须进行去噪声处理.结合实例数据介绍了半中值滤波法、半均值滤波法、等间隔极大值法用于植被指数的去噪声处理,效果良好;该处理方法同样适用于NOAA和MODIS等数据的植被指数预处理.     

波浪作用下半潜式养殖网箱水动力特性

半潜式深远海养殖网箱在波浪作用下会发生变形与运动。为保证网箱结构的稳定性,需对其水动力特性进行分析。本研究基于有限元法建立了波浪作用下一种半潜式网箱的数值模型,通过仿真计算求解网箱的锚绳受力与运动情况。首先,将计算机模拟值与物理水槽试验值进行比较,验证数值模型的准确性。然后,分别研究了半潜式网箱在3种压载状态下的动力响应情况,分析比较了不同波浪条件下网箱锚绳张力、垂荡、纵荡和纵摇的计算结果。结果显示,计算值与试验值基本吻合,二者的相对误差在5%左右。当波高一定时,网箱迎浪侧和背浪侧锚绳受力与波浪周期改变无明显关联;当周期一定时,两侧锚绳受力均随波高的增加而增大。网箱的垂荡、纵荡及纵摇值均与波高呈正相关,随着半潜式网箱吃水的增加,网箱的垂荡、纵荡及纵摇值基本呈减小趋势。网箱在3种压载状态下最大垂荡值和纵荡值分别为12.67 m和10.59 m,网箱在空载状态下的最大纵摇值≤15°,表明半潜式网箱结构具有较好的稳定性。研究结果可为我国深远海养殖网箱设计提供理论参考。     

深圳市抛石填海强夯地基的瑞雷波法检测

介绍了瑞雷波勘探的基本原理和工作方法及瑞雷波勘探在抛石填海强夯地基检测中的实际应用。瑞雷波法能全面、直观和快速地检测强夯地基的加固效果，缩短地基检测周期。     

Numerical study on wave attenuation inside and around a square array of biofouled net cages

In this study, waves propagating through a square array of 16 net cages with different levels of biofouling are numerically studied using a three-dimensional computational fluid dynamics (CFD) model. A porous-media fluid model is adopted to simulate both clean and biofouled netting of a cage array in waves. A numerical wave tank is built, and the oscillating-boundary method is adopted to generate waves. The flow motion is solved by the Navier-Stokes equations, and the free water surface is captured using the volume of fluid (VOF) method. The numerical model is validated by comparing the numerical data with corresponding experimental measurements of a net-cage model with clean netting. To analyze wave attenuation, a numerical analysis of wave elevation both inside and around the cage arrays is presented, which considers the effect of biofouling. Based on the results of the present study, the effect of biofouling on wave elevation is noticeable; the damping effect of the cage array increases with increasing level of biofouling. Furthermore, the incident angle of waves has a noticeable effect on the wave field inside and around the cage array.     

基于不同风场的台风浪数值模拟

为了检验FVCOM海洋模式模拟台风浪的效果,分别以CCMP风场和WRF模式模拟风场构建驱动台风浪的海面风场模型,基于FVCOM海洋模式,以2010年的"凡比亚"台风为例进行台风浪数值模拟,并用站点浮标资料进行了模拟结果检验。结果表明,FVCOM海洋模式模拟的水位、有效波高结果与实际观测结果的整体误差较小,模拟效果较好;受到风场与地形的影响,最大增水与减水的区域分别位于台风中心的左侧沿岸和右侧沿岸;风场与表面流场的模拟结果也符合台风过程中的风生流分布特征,即风场与表面流场方向、大小存在一致性。此外,对比分析2种不同海面风场模型下的台风浪模拟结果发现,二者均能较好地模拟此次台风过程,但存在一定的差异,增加WRF模式模拟风场作为强迫驱动风场模拟的有效波高更接近观测值。     

东亚夏季风年代际变化的波能影响特征

利用NCEP再分析资料,通过波包传播诊断的方法,分析了波包传播对东亚夏季风年代际强弱的影响,结果表明：在东亚夏季风表现出年代际强弱变化的同时,波包的传播也随之发生了一定的变化;波包在低层传播比较明显,越往高层越微弱;以850hPa研究层为对象,在20°N～50°N、70°E～120°E区域里,波包大值在20世纪80年代和90年代,由80°s传到赤道,强季风年代,波包大值由北太平洋中部传向东北太平洋北部,在弱季风年代,由东北太平洋北部传向北太平洋中部。在30°S～25。N、100°E～160°E区域里,波包大值在90年代由90°S传到30°S,从东太平洋传向西太平洋。在25。S～40°N、0°～60°E区域内．波包大值从大西洋传到太平洋中部,又从东太平洋传到太平洋中部。     

关于气候变化问题及其研究的几点意见

通过对大量与气候变化有关的研究和相关的佐证资料整理及综合分析,提出了在气候变化及其研究问题上几个值得关注的问题,并根据农业上的气象灾害时间分布特点重点探讨了波动说理论,重点是让人们对气候变化问题引起关注并在研究中要注意做到客观、公正、严谨。     

Design development of porous collar barrier for offshore floating fish cage against wave action,debris and predators

This paper presents a design concept of a porous collar barrier for a novel floating open-net fish cage that is integrated with a floating spar wind turbine (referred to as COSPAR fish cage). The COSPAR fish cage has an octagonal shape with each side length of 30m. The collar barrier, having an array of rectangular cut-outs with round corners, is installed at the top portion of the cage to attenuate wave transmission inside the cage as well as to protect fish from external predators and debris. Single and double collar barrier designs corresponding to single net and double net cages are studied. The wave transmission, reflection and energy-loss coefficients of barriers are determined from numerical analysis based on the linear potential wave theory and the eigenfunction expansion method. Various underwater heights (2m ≤ h ≤ 8m) and porosity (0.25≤ ε ≤ 0.75) of the collar barriers are examined with the view to obtaining the barrier design for minimal transmission coefficient and energy-loss coefficient. Without a collar barrier, the single net and double net cage can only provide average wave transmission coefficients of 0.9 and 0.8, respectively. This study finds that the transmission coefficient could be reduced below 0.4 by having a single collar barrier with h = 4m and ε = 0.25. On the other hand, the transmission coefficient could be further reduced below 0.3 by a double collar barrier with the same h and ε. In addition, the double collar barrier gives lower energy-loss coefficient and better proofing against fish escape, biosecurity and predator intrusion than the single collar barrier. A double collar barrier design with porosity combination of ε₁ = 0.25, ε₂ = 0.5 is recommended for the COSPAR fish cage as it yields competitive wave scattering performances and saves collar material by 25 % when compared with the best performing porosity combination of ε₁ = ε₂ = 0.25.     

不同钻孔方向对热压板传热和能耗的影响

从传热学的角度分析了热压板不同钻孔方向对热压板传热和能耗的影响，得出横向钻孔的热压机压板有利于传热和减少能耗。     

电容换相电压型逆变电路中晶闸管电流有效值的分析与计算

通过逆变电路中晶闸管电流的波形分析，导出了电流有效值的计算公式．它对于准确选择晶闸管及换流电感具有重要意义