基于等效渗透系数计算衬砌水压力方法研究

对于设置防水板和排导系统的复合式衬砌,由于防水板的隔水作用,围岩渗水主要通过防水板背后的盲管、反滤层及二次衬砌边墙底部排水孔排入隧道底部排水沟.这种地下水排导系统的设置,使得衬砌水压力的计算很难通过简化的解析方法求得.文章从工程实用化角度出发,提出了复合式衬砌等效渗透系数的概念和确定方法,其主要是通过引入虚拟的二次衬砌等效渗透系数“k1”,将设置防水板和排导系统的复合式衬砌的透水能力用等效渗透系数“k1”来表示.在复合式衬砌等效渗透系数的基础上,可以利用整体式衬砌结构的水压力计算方法估算衬砌水压力,等效渗透系数“k1”为复合式衬砌水压力的简化计算提供了有利条件.最后,通过算例验证了这种方法的合理性、有效性.     

碎石桩复合地基在软土路基处理中的应用

通过新铁高速公路项目碎石桩工程实例,对碎石桩复合地基的设计、施工、质量检测等方面进行了详细论述。     

包覆防护系统在高桩码头钢管桩维护中的设计与应用

结合我国华南地区处于海水环境的某码头工程钢管桩的维护,分析钢管桩的腐蚀特点,对比选择防腐蚀措施,最终在钢管桩腐蚀最严重的浪溅区及水位变动区选用了包覆防护系统设计并进行工程实践论证。有效解决了该区域传统措施防护年限不足的难题,取得优异的防护效果,为类似工程的设计及施工提供参考。     

The maximum approximate composite marginal likelihood (MACML) estimation of multinomial probit-based unordered response choice models

The likelihood functions of multinomial probit (MNP)-based choice models entail the evaluation of analytically-intractable integrals. As a result, such models are usually estimated using maximum simulated likelihood (MSL) techniques. Unfortunately, for many practical situations, the computational cost to ensure good asymptotic MSL estimator properties can be prohibitive and practically infeasible as the number of dimensions of integration rises. In this paper, we introduce a maximum approximate composite marginal likelihood (MACML) estimation approach for MNP models that can be applied using simple optimization software for likelihood estimation. It also represents a conceptually and pedagogically simpler procedure relative to simulation techniques, and has the advantage of substantial computational time efficiency relative to the MSL approach. The paper provides a “blueprint” for the MACML estimation for a wide variety of MNP models.     

用％ IR评价防腐层缺陷的使用方法和注意事项

用DCVG检测管道防腐层缺陷时,常用％IR这个指标对缺陷点的尺寸和严重程度等级进行评估和分级,但同时它又是非常容易被误解与错误使用的指标.文中从DCVG的原理和检测方法入手,并根据％IR的物理意义,介绍了DCVG单独测试和与CIPS联合测试时的计算方法,同时指出使用％ IR的一些注意事项.     

22MnB5钢热冲压高温防氧化涂层

22MnB5钢是目前国内外汽车制造行业最常用的热冲压用钢,但它的耐腐蚀性能稍差.针对这一问题制备了一种耐高温防氧化保护涂层,在950℃保温5min的热冲压工艺条件下,研究了所制备涂层的宏观形貌、表面形貌和防氧化作用,测试了该涂层的性能,并通过超高强钢防撞梁热成型试验验证了涂层的高温防氧化效果.结果表明,该涂层能均匀地覆盖在基体表面,无开裂,导热性好,满足了热冲压工艺的防氧化要求.     

Automated manufacture of optimised shape-adaptive composite hydrofoils with curvilinear fibre paths for improved bend-twist performance

Composite marine propellers improve hydrodynamic efficiency by inducing bend-twist coupling and allowing for passive pitch changes. One critical limitation, however, is the extent to which a composite propeller blade can deform and cause a pitch change without incurring structural failure. Recent numerical studies showed that curvilinear tows could improve the structural response of a composite blade by lowering its deflection or stress and strain required to induce a pitch change, but no experimental validation has been carried out before. The current study, thus, presents the manufacture of composite sandwich hydrofoils made with steered tows using automated fibre placement and validates the curvilinear tow benefits. Two hydrofoils were optimised with straight and curved fibre path layups, respectively and were manufactured for mechanical testing. The manufacturing complications arising from steering curvilinear tows in a three-dimensional convex mould are also discussed in the paper. The study found that significant tow buckling occurred near the tool cavity edge due to excessive steering radius during manufacture. The follow-up structural cantilevered tests showed that the experimental results were consistent with the FE predictions despite the presence of some manufacturing defects. The experiment agreed that the hydrofoil manufactured with curved tows achieved a similar tip twist but a significant reduction in deflection and critical principal strains compared to the hydrofoil made with straight tows. The use of a foam core reduced the overall weight of the sandwich hydrofoils by about 25% compared to that of a fully-carbon composite hydrofoil, and the numerical analysis showed that the core shear failure induced by transverse shear stresses was unlikely to occur.     

Collapse of composite-repaired cylinders with internal metal loss subjected to external hydrostatic pressure

The present study investigates the collapse performance of composite-repaired cylinders with internal metal loss subjected to external pressure. Three groups of intact, thinned, and repaired cylinders were designed, analytically verified, fabricated, geometrically measured, externally tested, and numerically modeled. Each group had three nominally identical cylinders to ensure the repeatability of experiments. The cylinders had the same end closure, effective length, total length, external radius, and intact thickness for an equivalent comparison. The thinned cylinder was considered as the intact cylinder with internal metal loss, whereas the repaired cylinder was considered as the thinned cylinder with composite reinforcement. The results indicated that the external loading capacity of cylinders with internal metal loss could be fully restored and even enhanced by composite reinforcement. Composite-repaired cylinders are much less sensitive to initial geometrical imperfections than intact cylinders.     

城市污水处理厂混凝土结构防腐要点与设计实例

调查表明[1],很多城市污水处理厂运行未达到设计使用寿命,水处理构筑物结构已经出现严重腐蚀现象.现从结构设计角度,简要分析污水对混凝土结构腐蚀作用的机理,提出分级防腐的设计方法,并列举一座典型城市污水处理厂的防腐设计.     

修造船VOCs治理体系

提出船舶挥发性有机物(Volatile Organic Compounds, VOCs)治理体系的总体要求，分析船舶涂装VOCs排放量。探讨船舶VOCs治理措施，从低VOCs环保船舶涂料开发与应用研究、修造船涂装作业的过程控制和VOCs末端治理技术等3个方面展开系统论述，并提出国内船坞区域涂装作业和VOCs控制技术的发展方向。