隧道竖井出渣孔孔径的确定及其稳定性分析

公路隧道竖井普遍采用反井法开挖,出渣孔孔径的确定及其稳定性对整个竖井工程至关重要。云南省墨江至临沧高速公路泰和隧道竖井为大直径深竖井反井开挖工程,围岩情况复杂,其出渣孔是否可以采用无支护的形式以及孔径的大小是决策的一个难题。采用理论分析以及有限元数值模拟等方法对竖井无支护出渣孔的孔径的选择及其稳定性进行了分析,确定了出渣孔合理经济的孔径。研究结果为施工中能够采用无支护的出渣孔及其孔径确定提供了依据。现场观察表明,出渣孔变形较小,能够正常使用。研究结果对设计和施工具有较好的指导作用。     

一种磁共振脑功能成像的头部移动校正方法

在磁共振脑功能成像（functional magnetic resonance imaging,fMRI)试验中，头部很小的移动就会对试验结果产生不良影响，因此在对数据统计分析之前要求进行移动校正。本文利用LMF（levenberg-mrquardt-fletcher)算法极小化参考图像和校正图像之间的残差平方和自动校正fMRI图像，根据多分辨率金字塔结构由粗到细地搜索最优解，既可以较快的收敛，又可以考虑较大的移动。     

利用铁酸镍控制二氧化钛结构相变提高其光催化性能研究

分别采用共沉淀法和溶胶-凝胶法制备铁酸镍和二氧化钛纳米粉体,探讨了铁酸镍纳米掺杂对二氧化钛"锐钛矿"→"金红石"的晶体结构转变及其光催化活性的影响.结果表明,铁酸镍的掺杂可抑制二氧化钛由"锐钛矿"到"金红石"的结构相变,显著提高其光催化活性,在最佳掺杂浓度时,其光催化降解曙红的效率可以提高约2倍.     

全身伽玛刀及其适形调强治疗

介绍了立体定向伽玛射线全身治疗系统(全身伽玛刀)的基本原理、关键技术及特点,推导了全身伽玛刀的剂量计算模型,并以此为基础探讨了其在适形调强放射治疗方面的应用.该设备采用多束伽玛射线旋转聚焦,能对肿瘤病灶自动定位、可在治疗过程自动更换焦点大小、对体部肿瘤病灶进行自动辐照,是一种自动化程度高、安全可靠、具有完全自主知识产权的大型放射治疗设备.在IMRT治疗计划系统配合下,能进行体部及其他部位肿瘤的精确适形调强治疗.该设备目前已在全国50多家医院使用,疗效显著.     

EAF steelmaking process with increasing hot metal charging ratio and improving slagging regime

A new electric arc furnace (EAF) steelmaking process with increasing hot metal charging ratio and improving slagging regime simultaneously was developed and applied in a 50 t electric arc furnace for more than a year at No. 1 Steelmaking Plant of Shanxi Taigang Stainless Corporation Limited. The essential fact of the new EAF steelmaking process was to charge hot metal in two portions or steps: firstly, 35wt%-40wt% hot metal was pretreated by blowing oxygen in a specially designed reactor for decar burization and improving hot metal temperature and melting premelted slag; secondly, 30wt% hot metal was charged into EAF with high basicity refining slags from ladle furnace (LF)-vacuum degassing furnace (VD) refining process. The results show that the hot metal charging ratio can reach to about 65wt%-70wt% for the new EAF steelrnaking process; meanwhile, the tap-to-tap time of a 50 t EAF can shorten by 5-10 min, the electricity consumption can decrease by 35-50 kW·h/t, the lime consumption can reduce by 10.5 kg/t of molten steel, and the content of harmful heavy metals in molten steel can be easily controlled to less than the upper limits of aimed steel specification or grade compared with the traditional EAF steelmaking process. In addition, the dephosphorization ability shows a slight strengthening, however, a small degree of lessening for desulphurization ability is observed for the new EAF steelmaking process, but the weakness of desulphurization ability cannot become an obstacle to its further application since a stronger desulphurization ability can be achieved during secondary refining of LF coupled with VD after EAF steelmaking process.     

Selective catalytic reduction of NO x by hydrogen over modified Pd/TiO2-Al2O3 catalyst under lean-burn conditions

A series of Ni, Sn and Ca modified Pd/TiO2-Al2O3 catalysts were prepared by the incipient wetness impregnation method and their catalytic performance for the selective catalytic reduction of NOx by H2 was evaluated. The results showed that the NOx conversion and N2 selectivity were improved over Pd-Sn/TiO2-Al2O3 and Pd-Ni/TiO2- Al2O3 catalysts above 200 ℃. More importantly, the N2 selectivity and high-temperature activity of Pd-Sn/TiO2- Al2O3 catalyst was far superior to the single Pd/TiO2-Al2O3 catalyst. The optimal Sn loading was 2 wt.%. X-ray diffrac- tion （XRD） results showed that the interaction between Pd and Sn promotes the dispersion of Pd over TiO2-Al2O3. Temper- ature-programmed reduction （Ha-TPR） results demonstrated that the addition of Sn contributes to the formation of PdO and improving the redox property of Pd/TiOz-Al2O3. The addi- tives of Ni and Sn also facilitated the absorption of NOx and the oxidation of NO to NOa, which play important roles in the selective catalytic reduction of NOx by hydrogen.     

基于联合概率分布的最优再保险策略

在保险公司和再保险公司的风险管理中,基于优化准则确定最优保险和再保险策略始终是保险学术界广泛关注的话题.许多已有研究大多都是从保险公司角度出发,考虑保险公司的最优再保险策略,然而保险公司的最优策略可能并不是再保险公司的最优选择,甚至不被再保险公司所接受.鉴于此,基于联合概率分布同时考虑保险公司和再保险公司双方的利益,探讨了基于期望值原则的最优比例再保险策略和最优停止损失再保险策略,在此基础上,进一步考虑了一般保费原则和更广泛的再保险合同类下的最优再保险策略,这些研究将对保险公司和再保险公司的风险管理及战略决策起到重要作用.     

高压直流输电工程微机型阀控系统在线模拟试验研究

作者研制的高压直流输电工程（简称ＨＶＤＣ）阀控系统装置在引进的瑞士ＡＢＢ公司交直流模拟系统上进行了两换流站之间直流系统的试验研究，本文着重介绍正常启动、停机、负载功率输送调节，系统工况变化时控制特性转换、故障紧急停机和电流参考值的协调控制软件；以及对调试中出现的电流电压振荡等不稳定现象所采取的对策和试验方法及经验。     

银川平原城市竞争力评价

考察了银川平原现状,对银川平原城市竞争力进行实证研究,在确立城市竞争力模型的基础上,构建了评价指标体系,运用综合评价方法中的均方差法对银川平原城市竞争力进行了评价研究.结果表明,银川平原各城市竞争力强弱明显,表现出一定的层次梯度,资源型和新兴工业城市排名靠前.     

加快三元催化器起燃的HEV混合驱动控制策略

针对冷起动阶段三元催化器起燃特性对整车排放影响显著的问题,提出了应用于混合驱动工况下以加快三元催化器起燃为目的、通过降低发动机输出功率来提高发动机排气温度的模糊控制策略以及基于极小值原理的起燃时间最优控制策略.依据传热学原理,利用集总热容法建立三元催化器动力学模型,在此基础之上,在Matlab/simulink环境下建立了整车动力学模型并进行了仿真计算,分析了上述2种控制策略对油耗和排放性能的影响,最后将仿真与试验结果进行了比较.结果表明:2种控制策略均能增大废气传递给三元催化器的热量,缩短催化器起燃时间,有效改善混合动力汽车冷起动阶段的排放.