Experimental investigation of the strength and stability of submarine pressure hulls with and without artificial corrosion damage

A submarine may have to operate for a period of time with local corrosion damage in the pressure hull if a suitable repair method is unavailable or too expensive for implementation. This paper describes collapse tests on twenty ring-stiffened aluminium cylinders, which were conducted to study the effect of corrosion damage on hull strength and stability. Artificial hull thinning was found to reduce the collapse strength of experimental models through high local stresses in the corroded region, leading to early onset of yielding and inelastic buckling. Bending associated with the eccentricity due to one-sided thinning was found to further increase the local stresses in the hull. Overall collapse pressures were more severely affected by corrosion damage than interframe collapse pressures. The percentage reduction in overall collapse pressure, compared with intact experimental models, was found to be closely related to the percentage depth of thinning. The accuracy of conventional collapse pressure predictions for the experimental models was significantly better for intact than for corroded cylinders.     

A multiple transfer function model for air traffic control systems

This paper considers the problem of modeling dynamic fluctuations in aircraft concentration within a group of air traffic control sectors. Using simultaneous time series recorded for each of the sectors, a multiple transfer function noise model is constructed. The modeling procedure demonstrates a data-dependent approach to ATC systems analysis which does not rely on describing the movement of individual aircraft.     

沈山线小跨度混凝土梁裂纹分析及整治措施

本文根据对沈山线小跨度梁重点调查的情况,分别分析阐述了老龄钢筋混凝土梁和八十年代更换的钢筋混凝土梁病害形成的原因以及病害整治措施。可供其它类似桥梁养护维修借鉴。     

呼准铁路建设与水土保持

呼准铁路位于内蒙古自治区中西部,新线全长117km。铁路所经区域,地貌类型复杂多样,且土壤侵蚀强烈,水蚀、风蚀并存,生态环境脆弱。本文结合呼准铁路的实际情况,对该项目建设可能引发的水土流失问题和水土保持工作进行了分析的探讨,提出了工程设计和施工中水土保持工作的重点与措施。     

Hydrodynamic loads on ice-class propellers during propeller-ice interaction

Hydrodynamic loads on a propeller blocked with simulated ice were studied using a cavitation tunnel. Comparative predictions were made using a panel method. The propeller was a model of the Canadian Coast Guard's R-class icebreake propeller, and the ice block was simulated using a solid blockage. Experimental results show the open water performance of the propeller, its performance behind a blockage, and the effects of cavitation in these conditions, as well as the loading on the simulated ice block. Panel method predictions were made of the time series propeller performance in the blocked flow. Cavitation during propellerice interaction resulted in a reduction of mean suction load on the ice block. Block load measurements indicated an increase in the oscillation about the mean value of the loads, with a variation in the phase of the loading with respect to blade position as compared with the non-cavitating results. Comparisons of panel method results with the measured block loads support the reliability of the dynamic measurements.List of symbols D propeller diameter - F block drag load - K _T thrust coefficient,T/(n ² D ⁴) - K _B block load coefficient,F/(n ² D ⁴) - K _Q torque coefficient,Q/(n ² D ⁵) - Q propeller torque - T propeller thrust - n propeller rotational speed - J propeller advance coefficientV _A/(nD) - P _A ambient pressure at propeller - P _ATM atmospheric pressure - P _V vapour pressure of water - V _A propeller advance speed - dissolved gas content - _s saturated dissolved gas content at atmospheric pressure - _o open water propeller efficiency - cavitation number, (P _A –P _V )/(0.5(nD)²) - density of water     

基于B—P神经网络的混凝土软化模型

本文探讨应用神经网络技术模拟材料本构行为的若干问题，并用Ｂ－Ｐ神经网络建立开裂混凝土的软化模型。     

北京地铁西单车站初期支护试验

通过模型试验分析浅埋大跨度洞室采用双侧壁导坑法施工中不同开挖阶段，不同开挖部位的地表沉陷表现，得出后开挖一侧洞室是引起整个洞室地表沉陷迅速增长的关键，为工程的安全施工提供了参考。     

涵洞水流流态判别式浅析

本文分析了影响涵洞水流流态的各种因素,根据水力模型试验成果讨论涵洞结构形态变化对过涵水流流态判别式的影响,提出了对现行判别式中Ｋ值的修正方法。     

铁路桥梁的可靠度评估

本文基于结构可靠性理论,对铁路桥梁设计规范的校准进行了探讨.从满足可靠度推 算出发,选定出合理的列车活载概率模型。对常用铁路桥梁的既有可靠指标进行了推 算。按所校准范围和一简化的验算式,初步选择出分项安全系数。      

用预钻式旁压试验结果推算地基土变形模量

本文主要介绍由预钻式旁压试验结果推求地基土变形模量的几种常用方法。并结合 粘性土层旁压试验实例,推求适用于某地区粘土的剧凡的比值.