地震下RC空心墩弯‑剪数值模型及混合试验验证∗

地震作用下钢筋混凝土空心截面中高桥墩多发生弯剪破坏,而其弯剪耦合反应的数值模拟方法尚不完善。 针对当前弯剪串联模型中的剪切模型未考虑空心截面特征的问题,提出基于关键参数的剪切模型修正方法,并通过混合试验进行验证。分别从桥墩的剪跨比、混凝土开裂后剪切刚度、等效截面面积、桥墩有效高度与墩身混凝土斜裂缝倾角等参数入手,提出剪切模型关键参数的修正方法;基于修正的开裂剪切强度、开裂剪切位移、剪切极限承载力及其对应的剪切位移与剪切破坏位移,提出适用于空心桥墩剪切性能模拟的三折线型骨架曲线建立方法; 通过组合剪切模型与基于纤维单元的弯曲模型,建立空心墩弯剪耦合反应的数值模型;与一座空心高墩桥混合试验结果对比,其桥墩子结构的物理试验结果验证了数值模拟方法。分析表明：通过本文所提数值模拟方法得到的空心桥墩弯剪滞回曲线与真实地震加载路径下的试验曲线匹配良好,能够模拟空心墩在真实地震作用下的弯剪滞回行为。     

近断层地震动运动特征对长周期结构地震响应的影响分析

选择台湾集集近断层地震动记录作为地震动输入,系统考察了近断层地震动破裂方向性、上盘效应、脉冲效应等运动特征对双线性单自由度体系、长周期隔震建筑和斜拉桥结构地震响应的影响。计算结果表明,脉冲型地震动对结构的效应随双线性单自由度体系的初始自振周期增大而变大,在长周期段结构的脉冲效应最显著;地震动破裂方向性和上盘效应对单自由度体系位移需求的影响与体系周期有关。对于隔震建筑和大跨度斜拉桥等长周期结构,近断层地震动破裂方向性对结构的效应较显著;上盘效应对长周期结构的影响明显;地震动的速度脉冲运动特征总的来说放大了结构响应。     

Predicting work performance in nuclear power plants

Diagnosis and monitoring are the major tasks of an operator in main control room of nuclear power plants (NPPs). The operator’s mental workload influences his/her performance, and furthermore, affects the system safety and operations. This study investigated the operator’s mental workload and work performance of the NPP in Taiwan. An experiment including primary and secondary tasks was designed to simulate the reactor shutdown procedure of the fourth nuclear power plant (FNPP). The performance of the secondary tasks (error rate), subjective mental workload (NASA Task Load Index, NASA-TLX) as well as seven physiological indices were assessed and measured. The group method of data handling (GMDH) was applied to integrate these physiological indices to develop a work performance predictive model. The validity of the proposed model is very well with R² = 0.84 and its prediction capability is high (95% confidence interval). The proposed model is expected to provide control room operators a reference value of their work performance by giving physiological indices. Besides NPPs, the proposed model can be applied to many other fields, e.g. aviation, air transportation control, driving and radar vigilance, etc.     

现役火电机组拆除脱硫旁路挡板应对措施研究

根据“十二五”环境保护规划要求,现役火电机组大部分脱硫装置必须拆除旁路挡板。介绍了现役火电机组脱硫装置旁路烟道设置所发挥的作用,分析了现役火电机组脱硫装置拆除旁路挡板后对机组所产生的影响及存在问题,并提出了相应的改造、完善和运维管理措施,为现役火电机组拆除脱硫旁路挡板后的工作提供借鉴和帮助。     

黑麦草对水体中镉-壬基酚复合污染的生理响应及修复

探讨了黑麦草对水体中镉-壬基酚（Cd-NP）复合污染的生理响应及修复作用.结果表明,单一Cd污染情况下,高浓度Cd²⁺(10 mg·L^-1)对黑麦草的生物量和叶绿素含量均有显著的抑制作用,植株过氧化物酶（POD）和多酚氧化酶（PPO）活性显著增大.单一NP污染情况下,黑麦草的生物量、叶绿素含量和MDA含量均无显著性变化;高浓度NP(5 mg·L^-1)存在下,植株POD活性显著增大.当黑麦草受到复合污染胁迫时,高浓度NP的加入降低了Cd的抑制作用,使黑麦草的MDA含量有所回落,植株PPO活性有所下降.Cd²⁺浓度为1 mg·L^-1时,黑麦草对Cd²⁺有较好的去除效果,12 h的去除率达到了55.3%.吸收时间超过12 h,高浓度NP对黑麦草吸收Cd²⁺有较显著的促进作用.NP浓度对植株地下部分Cd²⁺吸收量有极显著影响,转移系数随着NP浓度增大而呈现上升趋势.NP浓度为5 mg·L^-1时,黑麦草对NP的吸收效果较好,24 h的吸收率为44.6%.低浓度Cd²⁺的加入对黑麦草去除NP无显著性影响,而高浓度Cd²⁺的加入对黑麦草吸收和降解NP均有极为显著的抑制作用.     

Beta-normal distribution in dose–response modeling and risk assessment for quantitative responses

To establish allowable daily intakes for humans from animal bioassay experiments, benchmark doses corresponding to low levels of risk have been proposed to replace the no-observed-adverse-effect level for non-cancer endpoints. When the experimental outcomes are quantal, each animal can be classified with or without the disease. The proportion of affected animals is observed as a function of dose and calculation of the benchmark dose is relatively simple. For quantitative responses, on the other hand, one method is to convert the continuous data to quantal data and proceed with benchmark dose estimation. Another method which has found more popularity (Crump, Risk Anal 15:79–89; 1995) is to fit an appropriate dose–response model to the continuous data, and directly estimate the risk and benchmark doses. The normal distribution has often been used in the past as a dose–response model. However, for non-symmetric data, the normal distribution can lead to erroneous results. Here, we propose the use of the class of beta-normal distribution and demonstrate its application in risk assessment for quantitative responses. The most important feature of this class of distributions is its generality, encompassing a wide range of distributional shapes including the normal distribution as a special case. The properties of the model are briefly discussed and risk estimates are derived based on the asymptotic properties of the maximum likelihood estimates. An example is used for illustration.

Microclimate influence in a physiological model of cattle-fever tick (Boophilus spp.) population dynamics

Since their official eradication from the US in 1943, the cattle-tick species Boophilus microplus and Boophilus annulatus, vectors of bovine babesiosis, frequently have penetrated a quarantine zone established along the Texas–Mexico border designed to exclude them. Inspection and quarantine procedures have eradicated reinfestations successfully within the US, but increasing acaricide resistance in Mexican B. microplus populations poses a threat to future eradication efforts. Better understanding of interrelationships among Boophilus populations, their hosts, and vegetation communities in south Texas could improve prediction of the behavior of reintroduced Boophilus populations and increase management options. To this end, we constructed a simulation model to evaluate how microclimate, habitat (i.e. vegetation) heterogeneity, and within-pasture cattle movement may influence dynamics of Boophilus ticks in south Texas. Unlike previous Boophilus tick models, this model simulates dynamics at an hourly time-step, calculates all off-host dynamics as functions of temperature and relative humidity, and runs with ground-level microclimate data collected bi-hourly in three different habitat types. Sensitivity analysis of the model showed that temperatures and relative humidities created by habitat type, as well as engorged female mass, influenced tick population dynamics most strongly. Host habitat selection, initial number of larvae per cow, and the number of cells into which the simulated pasture was divided also had a strong influence. Population dynamics appeared moderately sensitive to the proportion of Bos indicus in cattle genotypes and the larval attachment rate, while appearing relatively insensitive to factors such as mortality rate of engorged females. When used to simulate laboratory experiments from the literature, the model predicted most observed life-history characteristics fairly well; however, it tended to underestimate oviposition duration, incubation duration, and egg mortality and overestimate larval longevity, especially at low temperatures and high humidities. Use of the model to predict Boophilus population dynamics in hypothetical south Texas pastures showed that it reasonably generated qualitative patterns of stage-wise abundances but tended to overestimate on-host tick burdens. Collection and incorporation of data that appear not to exist for Boophilus ticks, such as larval lipid content and lipid-use rates, may improve model accuracy. Though this model needs refinements such as a smaller spatial resolution, it provides insight into responses of B. microplus or B. annulatus populations to specific weather patterns, habitat heterogeneity, and host movement.