寿命服从威布尔分布的装备备件储备量确定

根据装备的寿命分布可准确地确定其所需备件量,对于寿命服从威布尔分布的装备,在确定了其寿命分布参数后,即可计算出其备件储备量。这种方法具有很好的实际应用价值。     

城市道路网可行性研究中CIVIL 3D应用浅谈

以武汉航空企业总部区域市政配套工程(四期)为例,采用AutoCAD Civil 3D计算道路和场地土石方,并与传统设计软件EICAD进行了比较。对Civil 3D的运用进行了简单的探索。     

乘用车车身水管理设计综述

为提升乘用车车身的防水能力,探讨了车身湿区的水管理方法和阻止车外的水进入车身干区的水管理方法.首先明确了车身湿区、干区的定义和车身湿区、干区的分界面,然后阐述了车身外部的导水、排水设计,后续章节重点分析了外界的水进入车身内部的各类途径,和各类进水途径的封堵方法,最后总结出与防水相关的试验是判定车身密封性能高低的依据.综...     

西津水利枢纽二线船闸下游引航道右岸支流汇入口消能设施设计

西津水利枢纽二线船闸工程是建设"西江亿吨级黄金水道"的重要举措之一。为研究二线船闸下引航道停泊段右岸西竹坑支流的汇入对二线船闸下引航道内通航水流条件的影响,通过水工模型试验研究在支流沟内布置消能设施对支流入汇口处流速、流态的影响,提出斜向导流坝、消力墩和消力池的工程措施,为类似工程提供借鉴。     

A dense water outflow from the Ross Sea, Antarctica: Mixing and the contribution of tides

We use hydrographic, current, and microstructure measurements, and tide-forced ocean models, to estimate benthic and interfacial mixing impacting the evolution of a bottom-trapped outflow of dense shelf water from the Drygalski Trough in the northwestern Ross Sea. During summer 2003 an energetic outflow was observed from the outer shelf ( 500 m isobath) to the  1600 m isobath on the continental slope. Outflow thickness was as great as  200 m, and mean speeds were  0.6 m s^− 1 relative to background currents exceeding  1 m s^− 1 that were primarily tidal in origin. No outflow was detected on the slope in winter 2004, although a thin layer of dense shelf water was present on the outer shelf. When the outflow was well-developed, the estimated benthic stress was of order one Pascal and the bulk Froude number over the upper slope exceeded one. Diapycnal scalar diffusivity (K_z) values in the transition region at the top of the outflow, estimated from Thorpe-scale analysis of potential density and measurements of microscale temperature gradient from sensors attached to the CTD rosette, were of order 10^− 3−10^− 2 m² s^− 1. For two cases where the upper outflow boundary was particularly sharply defined, entrainment rate w_e was estimated from K_z and bulk outflow parameters to be  10^− 3 m s^− 1 ( 100 m day^− 1). A tide-forced, three-dimensional primitive equation ocean model with Mellor-Yamada level 2.5 turbulence closure scheme for diapycnal mixing yields results consistent with a significant tidal role in mixing associated with benthic stress and shear within the stratified ocean interior.     

Two-dimensional numerical simulation and experiment on strongly nonlinear wave–body interactions

A constrained interpolation profile (CIP)-based Cartesian grid method for strongly nonlinear wave–body interaction problems is presented and validated by a newly designed experiment, which is performed in a two-dimensional wave channel. In the experiment, a floating body that has a rectangular section shape is used. A superstructure is installed on the deck and a small floating-body freeboard is adopted in order to easily obtain water-on-deck phenomena. A forced oscillation test in heave and a wave–body interaction test are carried out. The numerical simulation is performed by the CIP-based Cartesian grid method, which is described in this paper. The CIP scheme is applied in the Cartesian grid-based flow solver. New improvements of the method include an interface-capturing method that applies the tangent of hyperbola for interface capturing (THINC) scheme and a virtual particle method for the floating body. The efficiency of the THINC scheme is shown by a dam-breaking computation. Numerical simulations on the experimental problem for both the forced oscillation test and the wave–body interaction test are carried out, and the results are compared to the measurements. All of the comparisons are reasonably good. It is shown, based on the numerical examples, that the present CIP-based Cartesian grid method is an accurate and efficient method for predicting strongly nonlinear wave–body interactions.     

Mechanism of Tunnel Water Inflow Caused by Bending Failure of a Waterproof Dike Based on a Circular Thin Plate Mechanical Model北大核心CSCD

Water bursts during tunnel construction endanger construction, and it is therefore necessary to reserve a waterproof dike with the required thickness to avoid water bursts and to take reinforcement of the dike and treatment of the structure liable to trigger a water burst. Using the water burst at K5+398 of the Mingyueshan tunnel of the Shanghai-Chengdu expressway as an example, and considering the type of tunnel section and the upright mudstone of the dike, the waterproof dike at the work face is simplified as a round thin plate. A formula for the calculation of a minimum safety thickness for the critical waterproof dike is deduced by analyzing the force applied on the water-proof dike, and the minimum safety thickness for the water burst section at K5+398 of the Mingyueshan tunnel is cal-culated. The numerical simulation analysis demonstrates the critical thickness of waterproof dike at K5+398 of the Mingyueshan tunnel is 1.4-1.55 m, and the calculated water inflow and water burst basically agree with the actual condition. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

静态爆破法在深圳地铁施工中的应用

静态爆破是近年来发展起来的一种新型爆破施工技术,它可在无震动、无飞石,无噪音、无污染的条件下破碎或切割岩石或混凝土构筑物。深圳地铁2号线东延线土建工程安托山站—侨香站区间矿山法施工竖井系选用此工法在2 500 mm×3 000 mm雨水箱涵附近成功地进行了中、微风化花岗岩开挖施工,确保了雨水箱涵的安全性。     

垂直水幕作用下扩建地下水封油库布局方式研究

为研究垂直水幕对扩建地下水封油库布局方式的影响,以某大型地下水封洞库分期建设工程为依托,采用有限元数值模拟方法,对有、无垂直水幕条件下扩建洞库的布局方式进行研究。研究结果表明： 1）当两期洞库间距较小时,在两期洞库之间设置垂直水幕可有效削弱拟建洞库对已建洞库水封可靠性的影响,随两期洞库间距的增加,垂直水幕的影响性逐渐减弱; 2）拟建洞库轴线方向对水封可靠性的影响受地形等条件的影响较大,在两期洞库之间设置垂直水幕对水封可靠性的影响较小; 3）随拟建洞库埋深的增加,拟建洞库的水封可靠性逐渐增强,已建洞库的水封可靠性却呈逐步减小趋势,在两期洞库之间设置垂直水幕可有效减小埋深对两期洞库水封可靠性的影响。     

长洲水利枢纽坝下航道维护新问题及对策分析

文章通过分析长洲水利枢纽坝下水文条件改变给航道维护带来的影响,介绍广西梧州航道管理局针对维护新问题所采取的对策,指出今后该航段航道维护应重点注意的事项。