A critical CAE analysis of the bottom shape of a multi stepped air cavity planing hull

One of the most important aspects, in the ACS and multi stepped hull design, is the choice of the geometrical shape of the cavity and the steps. In this article a complete experimental and numerical campaign on a multi stepped ACS has been carried out, varying the velocity and the air flow rate under the hull. The experimental tests have been conducted in an ITTC Towing Tank allowing to validate the numerical simulations obtained by means of a CFD U-RANSe (Unesteady Reynolds Averaged Navier-Stokes equations) code. The CFD setup is described in detail. From this campaign a critical analysis of the Froude number influence on the air cushion shape has been argued. The authors identified four different behaviours, from low to very high Froude numbers. The use of CFD has allowed to observe quantities of difficult evaluation by means of traditional experimental test, as e.g. the frictional component of the resistance, the airflow path lines and the volume of fraction in transversal and longitudinal sections. The results have been discussed.     

GPS和GLONASS系统下RAIM空洞预报

接收机自主完好性监测（RAIM）是卫星导航系统完好性监测的方法之一。一定时空条件下的RAIM可用性,可以通过RAIM空洞直观的反映出来,可以为飞行提供预警;利用不同期GPS、GLONASS实际星座,仿真分析了单星座以及GPS／GLONASS组合星座RAIM可用性,绘制了RAIM空洞图,具有一定的参考价值。     

城市导线测量一体化程序设计

主要阐述利用QBASIC语言开发城市导线测量一体化程序设计的编程思想和实现过程(含程序主模块).     

我国核电厂设计中考虑的自然灾害综述与建议

我国是目前世界在建核电机组最多的国家,总装机容量世界第三,是名副其实的核大国,核安全是国家安全的重要内容,被提到了前所未有的高度.同时,我国也是世界上自然灾害最严重的国家之一,包括核电厂在内的重大工程建设高度重视自然灾害防御设计.日本311地震海啸引起福岛核事故后,核电厂设计中增强了对超设计基准自然灾害的考虑.本文对核...     

Some statistical characteristics of large deepwater waves around the Korean Peninsula

The relationship between significant wave height and period, the variability of significant wave period, the spectral peak enhancement factor, and the directional spreading parameter of large deepwater waves around the Korean Peninsula have been investigated using various sources of wave measurement and hindcasting data. For very large waves comparable to design waves, it is recommended to use the average value of the empirical formulas proposed by Shore Protection Manual in 1977 and by Goda in 2003 for the relationship between significant wave height and period. The standard deviation of significant wave periods non-dimensionalized with respect to the mean value for a certain significant wave height varies between 0.04 and 0.21 with a typical value of 0.1 depending upon different regions and different ranges of significant wave heights. The probability density function of the peak enhancement factor is expressed as a lognormal distribution, with its mean value of 2.14, which is somewhat smaller than the value in the North Sea. For relatively large waves, the probability density function of the directional spreading parameter at peak frequency is also expressed as a lognormal distribution.     

A joint distribution of significant wave height and characteristic surf parameter

The paper provides a joint distribution of significant wave height and characteristic surf parameter. The characteristic surf parameter is given by the ratio between the slope of a beach or a structure and the square root of the characteristic wave steepness in deep water defined in terms of the significant wave height and the spectral peak period. The characteristic surf parameter is used to characterize surf zone processes and is relevant for e.g. wave run-up on beaches and coastal structures. The paper presents statistical properties of the wave parameters as well as an example of results corresponding to typical field conditions.     

SEDIMENT TRANSPORT OF LOW CONCENTRATION IN PIPES

The study of Sediment transport of low concentration in pipes bas been applied in the design of a self-cleansing storm sewer. An alternative criterion is suggested as op- posed to the widely used single flow velocity approach. A conceptual model which simu- lates the condition in a storm sewer is developed and tested against experimental data. The results proved that the volumetric sediment concentration, pipe diameter and sedi- ment size have to be taken into consideration to produce a self-cleansing storm sewer. It also shows that the slope obtained by this alternative criterion is lower than the single flow velocity approach.     

顺便伽玛测量在水化普查中的找铀效果

在铀矿普查中,伽玛测量具有经济、快速、轻便、连续测量的特点。在水化普查中作顺便伽玛测量,投资少、收效快,并可直接发现供详查揭露的矿化点。在生产布置上与水化测量相互适应。通过一遍工作之后,可取得2套各具特点的资料。在资料解释及运用上,二者可互为补充。对无水地段,水化测量为空白区,可用伽玛测量补其不足。伽玛测量可为水化异常解释提供资料,水化异常的规模及浓度的高低又是推测深部矿化情况的依据。从统计结果证实,比例尺为上1:2.5万的顺便伽玛测量与1:1万的正规伽玛测量比较,发现异常机率可达60％。可见将顺便伽玛测量资料在测量精度上降一级使用,是可以满足精度要求的。     

浅谈自动气象站的防雷设计要点

运用当代防雷领域中的有关理论，对自动气象站容易遭受雷击的原因和途径进行分析，提出了自动气象站的防雷设计要点。