复杂地铁工程施工安全控制技术研究

北京地铁5号线崇文门站为国内首次在既有地铁隧道下方采用暗挖法施工的地铁车站,施工期间要保证既有地铁线路的正常运营,因此施工难度和风险极大。施工前对既有地铁结构进行了安全评估,根据评估结果并结合相关规范制定了既有线结构变形的安全控制标准。在施工风险分析的基础上,结合数值模拟计算确定了柱洞法施工方案,并辅以降水、超前大管幕和注浆等辅助技术措施,同时采用远程自动监测系统实时监控既有线的动态变化,对施工中既有线结构出现的异常变形进行了及时处理,最终地铁车站成功建成,并确保了既有地铁结构的安全和线路的正常运营。     

自动扶梯运行方式对地铁站台人员安全疏散的影响

地铁车站站台人员密集,客流量大,在火灾等应急条件下对人员安全疏散有较高的要求.目前自动扶梯在地铁车站中大量应用,其运行方式(上行、下行、停运、反转)对地铁车站内人员安全疏散有较大影响.利用人员疏散网络模拟软件EVACNT7对某地铁站台层人员向站厅层疏散进行数值模拟,研究了当自动扶梯正常上行时的输送能力,并与不同人流条件下的楼梯的输送能力进行了对比,得到动态折算系数.同时也研究了当自动扶梯停运作为疏散通道使用时的输送能力,并与人流条件优化时的疏散楼梯输送能力进行了对比得到静态折算系数.还研究了下行的自动扶梯在火灾等应急条件下反转上行以降低人员疏散时间,并给出了一种下行自动扶梯反转最迟完成时间的计算方法.研究工作可以为同类地铁站台人员安全疏散设计和应急预案制定提供参考.     

污泥停留时间对污泥减量化的影响

污泥停留时间不但决定系统剩余污泥的排放量,还直接影响到污泥的絮凝沉降性能及活性等。由实验可知:污泥停留时间延长,可导致微生物缺乏营养,减少污泥产生量;从而导致SVI升高,污泥负荷降低。因此,延长污泥停留时间减少剩余污泥量,可以节省尿素和KH2PO4投入量,从经济上节省运行成本。     

Temporal variability of groundwater chemistry in shallow and deep aquifers of Araihazar, Bangladesh

Samples were collected every 2-4 weeks from a set of 37 monitoring wells over a period of 2-3 years in Araihazar, Bangladesh, to evaluate the temporal variability of groundwater composition for As and other constituents. The monitoring wells are grouped in 6 nests and span the 5-91 m depth range. Concentrations of As, Ca, Fe, K, Mg, Mn, Na, P, and S were measured by high-resolution ICPMS with a precision of 5% or better; concentrations of Cl were measured by ion chromatography. In shallow wells <30 m deep, As and P concentrations generally varied by <30%, whereas concentrations of the major ions (Na, K, Mg, Ca and Cl) and the redox-sensitive elements (Fe, Mn, and S) varied over time by up to +/-90%. In wells tapping the deeper aquifers >30 m often below clay layers concentrations of groundwater As were much lower and varied by <10%. The concentrations of major cations also varied by <10% in these deep aquifers. In contrast, the concentration of redox-sensitive constituents Fe, S, and Mn in deep aquifers varied by up to 97% over time. Thus, strong decoupling between variations in As and Fe concentrations is evident in groundwaters from shallow and deep aquifers. Comparison of the time series data with groundwater ages determined by (3)H/(3)He and (14)C dating shows that large seasonal or inter-annual variations in major cation and chloride concentrations are restricted to shallow aquifers and groundwater recharged <5 years ago. There is no corresponding change in As concentrations despite having significant variations of redox sensitive constituents in these very young waters. This is attributed to chemical buffering due to rapid equilibrium between solute and solid As. At two sites where the As content of groundwater in existing shallow wells averages 102 microg/L (range: <5 to 648 microg/L; n=118) and 272 microg/L (range: 10 to 485 microg/L; n=65), respectively, a systematic long-term decline in As concentrations lends support to the notion that flushing may slowly deplete an aquifer of As. Shallow aquifer water with >5 years (3)H/(3)He age show a constant As:P molar ratio of 9.6 over time, suggesting common mechanisms of mobilization.     

洪涝灾害灾情时间变化特性分析——以中国1736～1911年主要大江大河流域变化序列分析为例

利用已经建立的全国1736～1911年洪涝灾害时间序列,拟合了各个区域的洪涝灾害长期变化趋势,并通过功率谱分析了时间序列的波动规律;同时,分析了气温,降水等自然因素的变化和人口总量变化、人口空间迁移以及土地利用变化等人文因素变化与灾害增减之间的关系。结果表明,洪涝灾害的波动主要由气候变化等自然因素的波动所引起,而人类活动增强并不断向高风险区扩展是洪涝灾害持续增长的主要原因,最终使洪涝灾害表现为在波动中持续增长。     

Sex ratio and oviposition responses to host age and the fitness consequences to mother and offspring in the parasitoid wasp Spalangia endius

In the parasitoid wasp Spalangia endius more offspring and a greater proportion of daughters were oviposited in, and emerged from 0-day-old versus 3-day-old hosts. Offspring that developed on the younger hosts (1) were larger at adulthood, (2) developed more quickly, (3) had higher survivorship to adulthood, and (4) were more often able to chew their way out of the host. Sons and daughters did not differ in how host age affected their size, development rate, or survivorship. The greater proportion of daughters from the younger hosts may be adaptive, as described by the host quality model (a variant of the Trivers and Willard hypothesis). It is adaptive if greater size or more rapid development has a more positive effect on a daughter’s than a son’s fitness and the positive effect is large enough to compensate for sons being trapped disproportionately to daughters in the older hosts. Despite greater success at drilling the younger hosts, mothers did not try to drill them sooner or more often. Having previously oviposited on the older rather than the younger hosts had no detrimental effect on the mother’s subsequent longevity or offspring production. Received: 8 March 2000 / Revised: 9 June 2000 / Accepted: 24 June 2000     

四种竞争与环境可持续性

本文提出了人类生产与消费活动所造成的环境功能的数量竞争、质量竞争、空间竞争和时间竞争的概念,系统地阐述了各自的内涵及其相互关系。     

Short-term wind speed forecasting: Application of linear and non-linear time series models

This study forecasts day-ahead wind speed at 15 minute intervals at the site of a wind turbine located in Maharashtra, India. Wind speed exhibits non-stationarity, seasonality and time-varying volatility clustering. Univariate linear and non-linear time series techniques namely MSARIMA, MSARIMA-GARCH and MSARIMA-EGARCH have been employed for forecasting wind speed using data span ranging from 3 days to 15 days. Study suggests that mean absolute percentage error (MAPE) values first decrease with the increase in data span, reaches its minima and then start increasing. All models provide superior forecasting performances with 5 days data span. It is further evident that ARIMA-GARCH model generates lowest MAPE with 5 days data span. All these models provide superior forecasts with respect to current industry practices. This study establishes that employing various linear and non-linear time series techniques for forecasting day-ahead wind speed can benefit the industry in terms of better operational management of wind turbines and better integration of wind energy into the power system, which have huge financial implications for wind power generators in India.     

畜禽养殖废水生物处理剩余污泥臭氧减量过程中的重金属释放

采用臭氧氧化污泥减量法对畜禽养殖废水SBR中的剩余污泥进行处理。当臭氧反应时间控制在30min时,污泥的溶解比例在30％左右（以MLSS计）。上清液中一定量的SCOD溶出可为生物处理单元提供充足的碳源,同时在上清液中,TN、TP及水相重金属浓度增加有限,臭氧氧化后的污泥液回流污水处理系统后造成的N、P处理负荷较小,重金属对污泥微生物的活性抑制风险较低。若继续延长臭氧的反应时间,上清液SCOD、TN、TP以及重金属cu、Pb的释放速率明显增加,同时上清液的C／N降低,臭氧化后的污泥液回流反而不利于生物单元的脱氮处理。综合考虑TN、TP及水相重金属浓度增加的危害性,臭氧反应时间应控制在30min,臭氧实际投加量应为123．1mg O3／gSS。     

Simplified heating time calculation using the Schmidt graphical method for PCB-contaminated capacitors undergoing the vacuum thermal recycling process

We discuss the use of the Schmidt graphical method to calculate the time required to heat a polychlorinated biphenyl (PCB)-contaminated capacitor in the vacuum thermal recycling process to the processing temperature of 400°C, and we evaluate the results of the heating time calculation by comparing the calculated values with the corresponding experimental values. The thermal conductivity and specific heat of the insulating paper and the carbonized paper in the capacitor were unknown, so we determined their values from experimental data obtained during the vacuum thermal recycling process. The capacitor element is a multilamination of aluminum foil and insulating paper, so we used an equation for a multilayer plane wall to calculate the value of the thermal conductivity. For the thermal conductivity and specific heat of the insulating paper impregnated with PCBs, we used values calculated from the mass ratios and thermal conductivities and specific heats of the individual materials. In addition, the physical properties vary according to the treatment because of the evaporation of PCBs and the carbonization of the insulating paper, so we modified the values of the thermal conductivity, specific heat, and density at the boiling point of the PCB and the carbonization point of the insulating paper before performing the calculations. Our calculated heating times were almost the same as, or were above, the experimental values, so we concluded that our method can be used as a simple calculation of the heating time.