Effect of fretting amplitudes on fretting wear behavior of steel wires in coal mines

Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation.     

Geometrically non-linear behavior of structural systems with random material property: An asymptotic spectral stochastic approach

An asymptotic spectral stochastic approach is presented for computing the statistics of the equilibrium path in the post-bifurcation regime for structural systems with random material properties. The approach combines numerical implementation of Koiter’s asymptotic theory with a stochastic Galerkin scheme and collocation in stochastic space to quantify uncertainties in the parametric representation of the load–displacement relationship, specifically in the form of uncertain post-buckling slope, post-buckling curvature, and a family of stochastic displacement fields. Using the proposed method, post-buckling response statistics for two plane frames are obtained and shown to be in close agreement with those obtained from Monte Carlo simulation, provided a fine enough spectral representation is used to model the variability in the random dimension.     

Mantle dynamics of the reactivating North China Craton:Constraints from the topographies of the 410-km and 660-km discontinuities

The topographies of the 410-km and 660-km discontinuities have important implications for mantle dynamics.Here we present high-resolution seismic imaging of the 410-km and 660-km discontinuities beneath the North China Craton (NCC) employing the receiver function method.Depth anomalies (deeper or shallower than the global average depths) at both discontinuities were detected by introducing a three-dimensional regional velocity model.The depressions of the 410-km discontinuity are mostly located in the easte...     

关于工程造价管理制度改革的思路

笔者结合工作实践,指出了现行工程造价管理制度存在的一些问题.提出现阶段过渡时期应健全有关招标、投标法规,包括招标范围、方式、规则,加快法制建设工程造价计价的方式方法尽可能与国际接轨等建议.     

长洲水利枢纽建坝后水流流态变化的可能性分析

长洲枢纽工程是一个低水头大流量的水力发电工程，河势及流态对枢纽建筑物的布置和调度进行都有较大的影响。本文根据枢纽整体水工模型试验成果，分析枢纽建成前后水流流态变化情况。     

1995年汛期长江流域长期水文气象预报及其验证分析

长江流域汛期长期水文气象预报成果是通过对气候背景的分析，前期天气气候征兆和重要物理因子的分析，最后经专家会商形成的，在预报方案制定过程中，坚持水文与气象，短中长期预报，科学研究与预报应用相结合，从定性上讲，无论时间和空间都基本吻合，对１９９５年长江汛期防洪发挥了重要的耳目作用。     

1993年汛期黄河下游河势遥感调查

利用ＭＥＲＩＤＩＡＮ遥感图象处理系统，通过ＴＭ图象最佳波段组合、线性拉伸放大、密度分割等处理手段，首次在黄河上进行了卫星遥感河势调查，其优势在于：（１）可以弥补目估河势的不足；（２）能够对河势流路、主流线位置、洪漫滩范围及水边线、生产堤、主要滩区洪水进出口门位置、进水和水围村庄等准确定位；（３）可以详细计算各类滩区面积与分布密度。     

抽吸方式对卷烟主流烟气氨释放量的影响

为考察抽吸方式对卷烟主流烟气中氨释放量的影响,采用ISO、Massachusetts和Health Canada 3种抽吸方案分别抽吸了15种国产卷烟,然后采用离子色谱法测定了这些卷烟主流烟气中氨的释放量.结果表明:①对于滤嘴打孔卷烟,与ISO抽吸方案相比,采用Massachusetts抽吸方案,混合型卷烟主流烟气中氨...     

A numerical study of hydrodynamic characteristics and hydrological processes in the coastal wetlands during extreme events

Providing accurate predictions of extreme water levels through numerical simulation has become essential for disaster prevention and damage mitigation in coastal wetland areas.This study applies the FVCOM model to simulate storm surges caused by several typhoons in the Bohai Sea and the North Huanghai Sea.The vegetation drag force caused by salt marsh plants is inserted into the FVCOM model for model improvement with vegetation effect by integrating RS and GIS technologies.A parametric typhoon model is coupled with background wind fields derived to acquire the spatio-temporal variations of wind and pressure fields in the computational domain.The simulation results reproduce the extreme storm surges induced by typhoon events very well.The modeling results are compared by validating with literature results to examine the effect of vegetation on tidal waves in tidal mud flats.Moreover,the coupled model is also applied to explore storm surge attenuation and land intrusion during Typhoon Winnie in the wetlands of the Liao River Estuary.The simulation results indicate that salt marsh plants can reduce the flow current with little impact on tide flooding/ebbing in vegetated regions.Furthermore,the results show that typhoon presence increases the inundation depth and extendes the flood time in the tidal wetlands of the study region.The FVCOM model incorporating the method with vegetation drag force can provide new insights to understand the comprehensive impact of tidal wetland plants on hydrodynamic characteristics in the Bohai Sea and other waters,hence presents a more accurate quantification of the hydrological process of storm surge in the tidal wetlands.     

气液固三相流化床流区及其过渡的混沌分析

运用确定性混沌分析技术、研究了气液固三相流化床内压力波动时间序列的混沌动力学行为,结果表明,非线性特征量最大Ｌｙａｐｕｎｏｖ指数可以用来定量表征三相流化床的流区及其过渡。并给出了以最大Ｌｙａｐｕｎｏｖ指数为基准的三相流区图,混沌分析还发现,三相流化床内存在着两混沌特性相差较大的塞状泡流区。