地下结构抗浮设防水位和浮力计算刍议

大量地下车库、下沉式广场等地下建筑的兴建,使抗浮问题非常突出。针对地下结构设计时抗浮设计水位的确定和水浮力计算问题,分析了地下水赋存状态与渗流特性、基础埋深与地下水层关系,介绍了设防水位的合理选取及水浮力实用计算方法,最后给出了工程算例。     

基于工业以太网的空压机远程监控系统设计

针对中小型企业压缩机的应用特点和监控要求,设计基于工业以太网络,以西门子S7-300可编程控制器为硬件核心,以组态软件Wincc为软件核心的远程监控系统,实现对压缩机运行状态的远程实时监测与控制,并与上级监控系统完成数据交换与信息共享,促进压缩机监控网络化、信息化与数字化.     

Nitrogen-, phosphorous- and boron-doped carbon nanotubes as catalysts for the aerobic oxidation of cyclohexane

Nitrogen-, phosphorous- and boron-doped carbon nanotubes (N-CNTs, P-CNTs and B-CNTs) were prepared by a chemical vapor deposition method using xylene as carbon source and aniline-NH₃, triphenyl phosphine and triethyl borate as nitrogen, phosphorous and boron precursors, respectively. By tailoring the composition of reactants and reaction atmosphere, N-CNTs with nitrogen contents from 0% to 4.36% and P-CNTs with phosphorous contents from 0.55% to 5.14% were synthesized. N- and P-CNTs are active for the oxidation of cyclohexane in the liquid phase with molecular oxygen as oxidant. The highest mass-normalized activity, 761 mmol g⁻¹ h⁻¹, was achieved over N-CNTs synthesized from aniline in an NH₃ atmosphere, while the highest surface-area-normalized activity, 28 mmol m⁻² h⁻¹, was observed over P-CNTs. B-doping does not improve the activity of CNTs. The effect of the number of nitrogen functionalities and defects was investigated to reveal the structure–activity relationship of the doped CNTs. By using the work function as an indicator of the electron donation of carbon, an exponential dependence of specific activity on work function was discovered for N- and P-CNTs, suggesting that the electron transfer on the surfaces of CNTs plays a central role in the CNT-catalyzed oxidation of cyclohexane.     

Molecular composition of soluble fraction from depolymerized cornstalk powder in supercritical methanol and ethanol

Cornstalk was depolymerized in supercritical methanol and ethanol, respectively. The depolymerization products were analyzed with FTIR and GC/MS. The results show that the products can be classified into methyl esters and dimethyl diesters, ethyl esters and diethyl phthalate, hydroxybenzenes and dihydroxybenzenes, ketones, methoxybenzene to trimethyoxybenzenes, hydrocarbons, nitrogen-containing organic compounds and other compounds. Most of the products are oxygen-containing species. Palmitate and octadec-9-enoate are the two most abundant products both with supercritical methanol and with supercritical ethanol. The fact that the cornstalk depolymerization in different solvents afforded many different products suggests that the two solvents played different roles in the cornstalk depolymerization.     

Study of the function of the insulation layer for treating water leakage in permafrost tunnels

Qinghai–Tibet Railway is one of the national momentous construction projects in the West Development Plan of China. Kunlun mountain tunnel is the key control engineering of the railway. But, according to the observation in-situ data, on May 22, 2003, water irruption took place in the construction joints at DK977 + 620 section (the sign DK is an abbreviation of distance kilometer, the number 977 expresses the 977 km, and the number 620 expresses 620 m), and the maximum flux of the water reached to about 200 m³/d(1 m³/d means one cubic meter per day), and the water pressure increased violently. In this paper, the status of water leakage of Kunlun mountain tunnel on Qinghai–Tibet railway is introduced by the time step. Based on the status of water leakage, the reason for water leakage in the tunnel is opened out. According to the basal theories of heat transfer and seepage, considering the coupled effect of seepage field and temperature field, a three-dimensional calculational model of the coupled problem are given, and the finite element formulae are obtained by Galerkin’s method, and the computer program is written. Using this model and program, three-dimensional nonlinear analysis for the coupled problem of the flat buried part from DK977 + 578 to DK977 + 682 in Kunlun mountain tunnel on Qinghai–Tibet Railway are made either with or without the insulation layer. The result shows that it is necessary for treating water leakage to fit the insulation layer between the two linings in Kunlun mountain tunnel.     

热电厂导汽管爆裂原因分析

对在运行条件为514℃、15．6MPa下爆裂的12Cr1MoV高温导汽管进行了失效分析。结果表明：钢中的珠光体球化、爆裂处附近的碳化物析出致使局部区域蠕变空洞连成串，形成了微裂纹造成了导汽管的失效。为防止再次出现爆裂，应严格控制导汽管的工作参数，避免在过高气压条件下运行，同时加强对管材的定期检测.     

发电厂机组螺栓断裂失效分析

发电厂机组螺栓在检修时发生断裂,因此对螺栓断裂原因进行了分析。结果表明,断裂的螺栓组织粗大不均,硫产生偏聚,螺栓材料严重脆化,不足以承受施加的载荷,而且外部载荷存在偏载,从而导致完全脆性断裂。     

白腐真菌对煤炭的降解转化试验

通过正交试验研究了白腐真菌在煤炭降解转化过程中煤样粒度、菌液用量、降解作用时间等各因素对其降解率的影响.还对白腐真菌对煤降解转化产物进行了元素分析，在此基础上探讨了白腐菌对煤生物降解转化的规律.实验结果表明，白腐真菌对经硝酸预处理后的义马褐煤样有较强的降解作用，15 d的时间能把粒度-0.2 mm的经硝酸预处理的义马褐煤降解41.54%，降解作用主要是白腐真菌在培养过程中释放出来的酶作用的结果.     

基于MgB2高温超导材料的吉瓦级远程直流输电研究

本文主要探究以具有成本效益和环保特性的新型高温超导材料(MgB_2)作为直流输电电缆,以液氢作为冷却剂,实现吉瓦级远程直流输电的可能性。首先分析超导直流输电的必要性及其优势,说明超导直流输电的基本模型,然后介绍MgB_2超导电缆和液氢制冷系统,接着阐述基于十二脉动换流器的直流输电控制策略。最后使用PSCAD软件完成超导直流输电系统仿真,在相同传输条件下进行MgB_2高温超导电缆和传统电缆的线路功率损耗比较,证明了超导直流输电系统具有线路损耗低,容量不受限制的优点,为MgB_2高温超导材料在超导直流输电领域的开发设计提供初步依据。