碳化砂浆轴向冲击动态力学特性与破碎形态分析

为保证长期使用砂浆在动载作用下的安全性,采用非金属超声波检测仪测量不同碳化龄期试件的纵波波速,引入碳化增强因子η表征碳化深度大小,并利用直径50 mm变截面分离式Hopkinson 压杆试验装置开展不同碳化龄期砂浆冲击动态压缩试验,研究碳化后砂浆的动态力学特性与破碎形态,分析砂浆动态应力—应变曲线、峰值应力和破碎形态随碳化龄期变化规律。结果表明:随着碳化龄期的增长,试件波速呈增大趋势,碳化增强因子η增大,碳化深度增加;碳化龄期相同时,砂浆的动态峰值应力、峰值应变都随着冲击气压的增大而增大;冲击气压相同时,砂浆的动态峰值应力随着碳化龄期的增长而增加;试件的破坏形态主要呈现为压碎破坏与劈裂拉伸。     

氯氧化锆生产排放废硅渣中锆资源的回收

开展了氯氧化锆生产排放废硅渣中锆资源的回收工艺研究,结果表明,当废硅渣在50℃条件下溶解废碱液时,硅渣中夹带的未熔锆英砂可以沉积,回收率可达到98.5%以上。继续加热溶硅碱液,可溶锆可与硅产生凝聚,形成锆富集物沉淀,锆富集物中湿基的ZrO2含量最高可达6.5%,可溶锆的回收率在97%以上。回收得到的未熔砂和锆富集物可直接返回氯氧化锆主流程中再利用,从而实现硅渣中锆的资源化利用。     

Influence of pedestrian age and gender on spatial and temporal distribution of pedestrian crashes

Objectives: Every year, about 1.24 million people are killed in traffic crashes worldwide and more than 22% of these deaths are pedestrians. Therefore, pedestrian safety has become a significant traffic safety issue worldwide. In order to develop effective and targeted safety programs, the location- and time-specific influences on vehicle–pedestrian crashes must be assessed. The main purpose of this research is to explore the influence of pedestrian age and gender on the temporal and spatial distribution of vehicle–pedestrian crashes to identify the hotspots and hot times.

Methods: Data for all vehicle–pedestrian crashes on public roadways in the Melbourne metropolitan area from 2004 to 2013 are used in this research. Spatial autocorrelation is applied in examining the vehicle–pedestrian crashes in geographic information systems (GIS) to identify any dependency between time and location of these crashes. Spider plots and kernel density estimation (KDE) are then used to determine the temporal and spatial patterns of vehicle–pedestrian crashes for different age groups and genders.

Results: Temporal analysis shows that pedestrian age has a significant influence on the temporal distribution of vehicle–pedestrian crashes. Furthermore, men and women have different crash patterns. In addition, results of the spatial analysis shows that areas with high risk of vehicle–pedestrian crashes can vary during different times of the day for different age groups and genders. For example, for those between ages 18 and 65, most vehicle–pedestrian crashes occur in the central business district (CBD) during the day, but between 7:00 p.m. and 6:00 a.m., crashes among this age group occur mostly around hotels, clubs, and bars.

Conclusions: This research reveals that temporal and spatial distributions of vehicle–pedestrian crashes vary for different pedestrian age groups and genders. Therefore, specific safety measures should be in place during high crash times at different locations for different age groups and genders to increase the effectiveness of the countermeasures in preventing and reducing vehicle–pedestrian crashes.     

Estimation of the accumulation rates and health risks of heavy metals in residential soils of three metropolitan cities in China

Heavy metal concentrations in urban soils are likely to increase over time because of continuous urbanization and heavy metal emissions. To estimate the accumulation rates of heavy metals in urban soils, we collected soil samples from residential areas with different building ages in the metropolitan cities of Shanghai, Shenzhen, and Beijing, China. Heavy metal concentrations in the soils varied among the cities and were primarily affected by soil parent material and the intensity of anthropogen...     

Determining the age of cyclomorphic rodents: Functional-ontogenetic determination,ecological aspects

Functional-ontogenetic determination of age-dependent dental changes (ADCs) in voles has been demonstrated. The relationship between ADCs and the functional state of animals has been analyzed. A scheme and a table for determining individual chronological and biological ages in the bank vole (Clethrionomys glareolus Sch.) are proposed, which markedly improve the accuracy of results. Cases of rodent maturation and breeding in winter are considered.     

湘中丘陵区不同经营目标毛竹林年龄结构、生物量分配与碳贮量格局

经营模式对毛竹林生物量、碳贮量具有重要影响。研究了湘中丘陵区毛竹笋用林(Ⅰ)、笋材兼用林 (Ⅱ)和材用林(Ⅲ) 3种不同经营目标下的竹林年龄结构、生物量分配及碳贮量格局。结果表明：应减少1～2 a、增加5～6 a生竹的留养比例,控制达到1～2 a、3～4 a、5～6 a各占1/3左右的立竹年龄结构。不同层次生物量表现为乔木层＞凋落物层＞林下植被层,毛竹笋用林经营有利于增加乔木层生物量。乔木层生物量及所占比例分别为5183～5566 t/hm2、8895%～9293%,林下植被层生物量及所占比例分别为154～258 t/hm2、258%～443%,凋落物层生物量及所占比例分别为269～386 t/hm2、449%～662%。毛竹林总碳贮量排队顺序为Ⅱ（14263 t/hm2）＞Ⅰ（13389 t/hm2）＞Ⅲ（13004 t/hm2）,笋材兼用林有利于提高竹林碳贮能力。不同层次碳贮量排列顺序总体均表现为土壤层＞乔木层＞凋落物层＞林下植被层。湘中丘陵区毛竹林生物量、碳贮量较低,应提高集约经营水平     

Timing of phosphate application affects arsenic phytoextraction by Pteris vittata L. of different ages

The effects of timing in phosphate application on plant growth and arsenic removal by arsenic hyperaccumulator Pteris vittata L. of different ages were evaluated. The hydroponic experiment consisted of three plant ages (A45d, A90d and A180d) and three P feeding regimens (P200+0, P134+66 and P66+134) growing for 45 d in 0.2-strength Hoagland-Arnon solution containing 145 microg L(-1) As. While all plants received 200 microM P, P was added in two phases: during acclimation and after arsenic exposure. High initial P-supply (P200+0) favored frond biomass production and plant P uptake, while split-P application (P134+66 and P66+134) favored plant root production. Single P addition favored arsenic accumulation in the roots while split-P addition increased frond arsenic accumulation. Young ferns (A45d) in treatment P134+66 were the most efficient in arsenic removal, reducing arsenic concentration to below 10 microg L(-1) in 35 d. The results indicated that the use of young ferns, coupled with feeding of low initial P or split-P application, increased the efficiency of arsenic removal by P. vittata.     

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     

大气挥发性有机物的日变化特征及在臭氧生成中的作用——以广州夏季为例

为了得到实时的大气挥发性有机物(VOCs)浓度组成和日变化特征,2006年夏季在广州市区内高约55m的楼顶采用在线的气相色谱仪进行了为期一个月的观测.结果表明,影响城市VOC含量的物种以及对臭氧生成有重要贡献的典型物种的日变化存在不同的特征.烷烃类和烯烃类物种出现早晚高峰值,估计主要与机动车排放有关,芳香烃除了与交通排放有关,还受到溶剂挥发的影响,早晨的峰值晚于交通高峰时间.异戊二烯在正午时间出现一天的单峰值,主要来自于天然源排放.乙苯和间对二甲苯的比值被用来表征采样点上气团光化学反应的进程,通常情况下,广州市区点气团经历的光化学进程越久,臭氧浓度越高.     

不同铅暴露区人体离体牙铅含量和年龄关系及指示意义

人体牙釉质是记录环境铅(Pb)暴露信息的较好载体。本研究采用微波消解-电感耦合等离子体质谱仪(ICP-MS)联用的方法测定来自高Pb暴露区(铅锌冶炼厂地区)和Pb暴露对照区(农业种植区)附近长期居住 /不同年龄段人体离体牙的Pb含量,结果显示：高Pb暴露区离体牙表现出Pb含量高且随居民年龄增长而增高的趋势,离体牙Pb含量从6—12岁儿童的(60.8±15.3) μg·g^-1增加到65岁以上老年人的(200.1±30.5) μg·g^-1;而铅暴露对照区人体离体牙Pb含量低且基本随年龄增长变化不大。Pb主要通过呼吸道和消化道进入人体并在牙齿中富集,因此,牙齿中的Pb含量与生活环境密切相关。研究结果表明：生活在高Pb暴露区的人群,环境中的Pb可能通过各种介质(空气、水、实物等)不断进入人体,其牙齿不断蓄积环境来源的Pb。因此人体离体牙Pb有可能作为人体长期Pb暴露生物标志物。