北京中心镇工业用地规划的调查和反思

随着改革开放的深化,我国城市化进程逐步加快,这给广大村镇的发展带来了无限生机。在北京,市政府于2000年确定了郊区33个条件较好的小城镇作为中心镇进行重点建设,这使得中心镇的地位和作用越发显得重要,并逐渐成为了联系农村与城市发展中的关键一环。当前,北京中心镇的集聚功能、经济带动、辐射功能和吸纳农村富余劳动力、带动农民增收这三大功能得到一定发挥。但与此同时,北京中心镇的建设又存在着一些问题:如发育程度低、规模小,集聚程度低,经济实力较弱,产业层次不高,发展不平衡等问题突出。尤其在产业发展和工业用地规划等方面的问题值…     

地域——一种文化的空间与视阈

在当代建筑活动中,全球化与地域性构成了一种双向互动,提出了一系列“现代性”问题。有关全球化与地域性的争论似乎不可调和,然而其中却普遍存在着对于这两个概念的误解,这导致我们难于深入地域建筑文化的本质。本文试图对此论题进行深入探讨。     

农村及偏远地区饮用水除氟研究

研究了农村及偏远地区地下饮用水的除氟方法及其工艺流程、发展中的除氟新方法及新材料;分析了现有饮用水除氟设施存在的问题及其原因;提出了适合于农村及偏远郊区的除氟方法及其设施的发展方向.     

单-双极运行方式转换直流电力电子变压器的启动策略研究

直流电网技术的各类场景,均存在实现各类功能的直流型电力电子变压器。分布式/集中式的新能源电站自身的单极性直流输出,与外部连接的双极性电网之间,需要一种专用的单-双极运行方式转换直流电力电子变压器,用以匹配两者运行方式的差异。本文基于双向有源全桥电路,给出一种应用于该场景下的具体实现方案。在分析其电路拓扑、工作原理、控制策略基础上,设计出一套功率30k W,输入150V转换为±150V的单-双极运行方式转换直流电力电子变压器。针对不同的工况下外部条件不同以及控制目标差异,对变压器启动过程进行研究,并设计相应的启动控制策略。仿真与实验结果均证明了理论分析的正确性和有效性。     

Investigation on the cold-strip breakage of SUS445J2 ultra-pure ferritic stainless steel during rolling process

In this work,the cause of the cold-strip breakage of SUS445J2 ultra-pure ferritic stainless steel was investigated using optical microscopy,energy dispersive spectroscopy,and electron backscatter diffraction technique.Results show that during cold rolling,the breakage of the stainless steel strip was mainly caused by massive niobium-rich(Nb-rich)carbides present in the center of the strip.Furthermore,cracks initiated at these carbides in the central layer.The massive carbide precipitates resulted from the segregation and enrichment of Nb,titanium(Ti),and carbon(C)in the central layer during the subsequent solidification stage of SUS445J2 stainless steel.Additionally,the banded structure and coarse ferrite grains in the central layer reduced the plasticity of the material,causing cracks to propagate along these grains and finally leading to cold-strip breakage.By reducing the solidification cooling rate of the billet,increasing the pouring temperature,discretizing Nb,Ti,and C enrichment via electromagnetic stirring,and forming equiaxed crystals in the central layer,the precipitation of harmful massive Nb-rich carbides in the central layer could be effectively avoided.     

Bearing behavior and failure mechanism of squeezed branch piles

The current practice for the design of squeezed branch piles is mainly based on the calculated bearing capacity of circular piles. Insufficient considerations of the load-transfer mechanism, branch effect and failure mechanism, as well as overreliance on pile load tests, have led to conservative designs and limited application. This study performs full-scale field load tests on instrumented squeezed branch piles and shows that the shaft force curves have obvious drop steps at the branch position, indicating that the branches can effectively share the pile top load. The effects of branch position, spacing, number and diameter on the pile bearing capacity are analyzed numerically. The numerical results indicate that the squeezed branch piles have two types of failure mechanisms, i.e. individual branch failure mechanism and cylindrical failure mechanism. Further research should focus on the development of the calculation method to determine the bearing capacities of squeezed branch piles considering these two failure mechanisms.     

Role of molecular structure on bioelectrochemical reduction of mononitrophenols from wastewater

The effect of nitro-substituent on mononitrophenol (o-nitrophenol (ONP), m-nitrophenol (MNP) and p-nitrophenol (PNP)) reduction in a bioelectrochemical system (BES) was investigated in this study. The results show that the removal of all three nitrophenols was significantly enhanced with more negative cathode potential and shortened hydraulic retention time in the BESs. Moreover, the reduction of the three nitrophenols followed in the order of ONP > MNP > PNP in the BESs. Both quantum chemical calculation using density function theory and cyclic voltammetry analysis confirmed the reductive sequence of the three nitrophenols. In addition, the acute toxicity of nitrophenol effluent significantly decreased while its biodegradability was enhanced after treatment in the BES. Therefore, the BES technology offers bright prospects for efficient treatment of nitrophenol-containing wastewater.     

苏丹SOBA大桥桩基础旋挖钻机水上施工工艺分析

本文主要介绍了旋挖钻机水上桩施工工艺。实践证明了清水平衡水压钻进方法的可行性,并且具有保护环境、缩短施工工期、减轻施工强度、减少施工成本等优点。     

公路工程混凝土裂缝的防治研究

混凝土作为我国目前公路工程建设中最主要的结构形式,在使用过程中却经常发生裂缝问题,这对公民行驶的安全造成了极为不良的影响。本文就工程混凝土裂缝的防治问题展开了深入地探讨。