隧洞开挖网络进度的优化研究

本文以单项工程为研究对象,以隧洞工程为例,研究了单项工程施工所需用的时间。文中以施工单位所具有的资源,结合施工工作环境、作业空间为约束条件,以费用最小为目标函数,建立了优化模型。由资源的工作性能指标,利用模糊数学原理,对资源间的匹配程度作了定量分析,并进一步推出了不同匹配程度的资源对作业时间的影响的计算式。并从影响各工序完工时间的因素的随机性出发,利用数理统计理论,由各工序的细分活动的规律推出了各工序的完工需用时间的概率表达式,解决了工期与置信度间的关系。最后结合工程实例,求出了一定置信度下,不同资源供应时的最优工期。     

变频调速节能改造方案的经济性评价和比较

本文详细介绍了变频调速节能改造方案的经济性评价方法。静态分析法包括投资回收期法、抵偿年限法和年计算费用法；动态分析法则包括净现值法、内部回收率法、总费用现值法和最小年费用法。     

浅谈不同时期南非政府办公建筑的发展特征

南非的社会发展经历了殖民主义统治时期，种族主义统治时期和民主政府统治时期3个历史阶段。社会体制的变化深深影响了南非建筑的发展。尤其体现在政府办公建筑的形式上，本文按照历史发展的顺序，通过列举实例的方式，分别对这3个时期政府办公建筑的风格与布局牲进行了的探讨。     

按件供应模式应用研究

对进口件（即KD件）按件供应与成组供应模式进行了对比分析，结合按件供应在启动、运行期间的工作特点，对神龙公司按件供应管理模式进行了分析和探讨，分析了KD件按件供应中MRPⅡ与JIT的结合应用以及按件供应模式的信息组织方式，提出了缩短订货期、降低库存、提高市场需求响应度的具体建议，并在实际运用中取得了显著的经济效益和管理效应。     

基于Copula函数的洪水峰量联合设计方法研究

为明晰洪水峰量联合设计的特点,以岗南水库洪水为例,基于Gumbel Copula函数,分析了AND、OR、Kendall、生存Kendall 4种重现期的优缺点,采用极大似然法、同频率法、条件最可能组合法3种方法计算了联合设计值。结果表明: ①AND和OR重现期在危险域和安全域的识别上存在局限性;相对而言,Kendall重现期更合理,但其安全域是无界的,这与实际不符;生存Kendall重现期则界定了有界的安全域,使得重现期的概念在逻辑上更科学合理。② 3种设计值计算方法的差别不大,但从简单实用角度出发,推荐采用同频率法计算设计值。③不同重现期标准的设计值差别比较明显,基于OR重现期计算的设计值总是最大的,生存Kendall、Kendall重现期设计值次之,AND重现期设计值最小。④推荐采用生存Kendall重现期进行两变量洪水设计,因其有比较严谨的理论基础,且设计结果兼顾了安全性与经济性。⑤两变量联合设计值与单变量设计值的差异受变量间相关性的影响较大,且变量相关性越弱,差异越大。研究显示,基于生存Kendall重现期、采用同频率法计算设计值是目前较为科学合理的洪水峰量联合设计途径。     

Influence of rainfall on the performance of bioretention systems modified with activated carbon and biochar

The use of bioretention areas is common in urban stormwater management, but their performance varies significantly depending on rainfall characteristics and design conditions. In this study, a pilot experiment using bioretention columns with different media (commercial activated carbon and river sediment-derived biochar) investigated the influence of rainfall on bioretention performance. The results indicated that the runoff volume retention ratio (R_v), which included the runoff purified and discharged at the bottom of the column, and the runoff retained in media during rainfall event, decreased significantly with increases in the rainfall event return period (p < 0.05). The R_v of the activated carbon and biochar columns decreased with a 2-yr return period and then fell further with a 50-yr return period. Porous material has been shown to improve the water-holding capacity of bioretention media, but it did not result in an improved R_v under heavy rain that exceeded the 2-yr return period. With the increase of the return period from two to 50 yr, the mass removal efficiency (R_L) of total phosphorus and phosphate illustrated a clear decreasing trend in all columns. The total nitrogen, ammonia and nitrate removal did not show a clear trend with return periods because of transformations among different forms of nitrogen and similar saturation periods during the different rainfall events. The influence of the return period on chemical oxygen demand (COD) removal was related to whether the inflow COD reached maximum COD removal capacity of the bioretention media. Under a rainfall event with a specific return period, there were no significant differences in the R_L of all nitrogen species and COD among the different columns (p > 0.05). The addition of adsorptive material, such as activated carbon and biochar, may not be the key factor for improving nitrogen and COD removal under heavy rain that exceeds the 2-yr return period. The bioretention performance of phosphorus removal from urban stormwater runoff could be improved by replacing or adding media with high adsorption capacity, but these improvements would not be significant under heavy rain that exceeds the 2-yr return period. The results provide some reference for evaluating bioretention performance and optimizing bioretention design in the future.     

地区电网新能源消纳困难时段研究

文章主要研究了某实际电网新能源消纳困难时段。通过负荷特性分析,得出地区电网低谷负荷出现季节和典型日负荷特性,通过风电场、光伏电站出力特性分析,得出风电、光伏季节分布特性及日出力特性。在地区电网新能源消纳的困难时段分析基础之上,对困难时段负荷概率进行统计,得出困难时段的负荷取值,为新能源接纳能力分析提供重要的数据支撑。     

关于贝氏体形核和台阶机制的讨论--与徐祖耀院士等商榷

一些合金固溶化(或淬水)后在预贝氏体(孕育)期内等温淬火(或时效)，既保持高温时形成的晶体缺陷，又产生新的晶体缺陷。母相中由于溶质原子扩散而在缺陷处发生偏聚，则形成贫／富溶质微区，即类拐点(spinoclal—like)分解。当贫溶质微区成分作为Ms，其温度等于或高于等温淬火(或时效)温度时，贝氏体将以马氏体样切变形核，故贝氏体是在溶质原子扩散控制下切变形核。在TEM温台试验中未发现台阶生长机制，界面上巨型台阶是贝氏体增宽(厚)速度差异所致。     

Texaco煤气化装置长周期运行影响因素分析

介绍了Texaco煤气化工艺流程,从原料煤种、水煤浆浓度、操作工艺、关键设备等几个方面讨论了影响装置长周期运行的因素,提出了延长气化装置运行周期的措施。     

Increasing urea-N efficiency for transplanted lowland rice by pneumatic injection: Yield and economics at the farm level

To increase the fertilizer-N efficiency in lowland rice (Oryza sativa L.) cultivation, new management practices are needed. Main cause of the present low efficiency is the low N recovery by plants, as a considerable part of the N applied is lost; deep placement techniques improve the recovery. A pneumatic injector, with which urea prills can be point-placed at a depth of 5–10 cm in paddy soils, was tested in 38 on-farm trials in 1989/90, mostly during the wet season. The experiments, located in Africa and Asia, focussed on differences in grain yield between conventional methods of broadcasting urea and injection by the pneumatic injector, at recommended N-rates. The study shows that the pneumatic injector is effective as a tool to improve the N fertilizer efficiency. The average yield increases per region, resulting from the use of the injector, ranged from about 250 to 1300 kg grain ha^–1. The value of the yield increase would allow most farmers to recover the costs of the injector within one season, even if labour was hired to carry out the injections. The average labour requirement of the injector was 40 hours ha^–1. In Indonesia, injection of prilled urea gave yields similar to those obtained with urea briquettes.