不同土地利用方式下北京城区土壤的重金属累积特征

对不同土地利用方式下城市土壤的采样调查表明,北京市城市土壤Cd、Cu、Pb和Zn含量显著高于其相应的土壤背景值,As、Ni与背景值无显著差异.在工业、住宅、商贸、交通边缘带(道路)、公园、城市广场和校园7种土地利用方式下,工业区土壤Cd、Cu、Ni、Pb和Zn含量均居首位,且Cu、Pb和Zn含量达到污染等级;公园土壤的As水平最高,但仍处于清洁水平.As、Cd、Cu、Ni、Pb和Zn综合累积程度由高到低的顺序为工业区公园商贸区≈校园住宅区≈城市广场交通边缘带.工业区土壤总体表现为重金属轻度污染;公园、商贸区、校园和住宅区土壤重金属处于尚清洁水平;城市广场和交通边缘带土壤重金属处于清洁水平.不同土地利用方式对城市土壤的重金属含量有一定影响.     

基于YOLOv3的电网作业人员安全帽佩戴检测

为了有效监测电网作业人员不规范佩戴安全帽行为,提出1种基于YOLOv3的电网作业现场安全帽佩戴检测方法.针对安全帽佩戴规范性问题,构建正确佩戴、不正确佩戴和未佩戴安全帽3种情况下的图像样本库;并利用该数据库对YOLOv3模型进行训练与测试,结合模型参数、样本比例及算法对比分析,开展电网作业人员安全帽佩戴检测算例.结果表...     

个体防护装备在受限空间作业中的选择配备与使用管理

近年来,受限空间伤害事故频发,已引起各相关部门的重视。个体防护装备的合理正确选用在避免受限空间伤害事故的发生上起着至关重要的作用。本文通过典型案例,仅从个体防护装备的配备和管理角度分析事故的致因,并根据受限空间内所存在的各种危害类别及形式探讨个体防护装备的选配以及合理的使用与管理,以期能够有效地防止或减少受限空间内作业伤害事故的发生。     

Energy consumption analysis of ABS plastic parts injected in a hybrid injection moulding machine

The energy analysis of injection moulding processes is influenced by complex interactions amongst the moulded part, its material, the injection machine, the process parameters and the environmental conditions. The availability of energy usage analyses that comprehend information on specific materials and machine kind is limited. This paper reports a study that estimates and analyses the power usage profile (PUP), the specific energy consumption (SEC), and the energy distribution at an operation level of two different injected parts made of acrylonitrile-butadiene-styrene and produced in a hybrid injection moulding machine. The methodology followed by the authors incorporates an experiment carried out in an industrial facility. A large sample size, and data-acquisition and data post-processing processes to obtain an accurate PUP and SEC are used. A breakdown of the energy consumed by the injection moulding process of the parts studied at an operation level using Sankey diagrams is discussed. The study results are used to identify strategies to reduce the energy consumed by the processes. The methodology employed, and the strategies reported could be used with other plastic parts regardless of the material and machine used. The results reported are new experimental data useful input for theoretical models.     

辐射制冷技术在安全帽上的应用研究*

为缓解夏季配戴安全帽导致的头部高温不适,采用具有光谱选择特性的辐射降温涂料对安全帽表面光学性能进行改性,经光学测试,安全帽的太阳辐射反射率由45%提升至89%,大气窗口发射率由92%提升至95%。对安全帽进行降温效果测试,并基于测试结果建立热力学模型。结果表明:在阳光直射下,改性安全帽内部温度低于普通白色安全帽,温差最大12.2 ℃;在热力学模型中,即使在夏季最热时间段（12∶00～14∶00）,改性安全帽内部温度仍可比普通安全帽低8 ℃,预测平均评价值由普通安全帽的3.5降低至1.0,预测不满意百分比从100%降低至20%。     

Influence of ATD versus PMHS reference sensor inputs on computational brain response in frontal impacts to advanced combat helmet (ACH)

ABSTRACT

Objective: This study analyzed the influence of reference sensor inputs from anthropomorphic test devices (ATDs) versus postmortem human subjects (PMHSs) on simulations of frontal blunt impacts to the advanced combat helmet (ACH).

Methods: A rigid-arm pendulum was used to generate frontal impacts to ACHs mounted on ATDs and PMHS. An appropriately sized ACH was selected according to standard fitting guidelines. The National Operating Committee on Standards for Athletic Equipment (NOCSAE) head was selected for ATD tests due to shape features that enabled a realistic helmet fit. A custom procedure was used to mount a reference sensor internally near the center of gravity (CG) of the PMHS. Reference sensor data from the head CG were used as inputs for the Simulated Injury Monitor (SIMon). Brain responses were assessed with the cumulative strain damage measure set at 10%, or CSDM(10).

Results: Compared to ATD tests, PMHS tests produced 18.7% higher peak linear accelerations and 5.2% higher peak angular velocities. Average times to peak for linear accelerations were relatively similar between ATDs (5.5?ms) and PMHSs (5.8?ms). However, times to peak for angular velocities were higher by a factor of up to 3.4 for PMHSs compared to ATDs. Values for were also higher by a factor of up to 13.1 when PMHS inputs were used for SIMon.

Conclusions: The preliminary findings of this work indicate that small differences in ATD versus PMHS head kinematics could lead to large differences in strain-derived brain injury metrics such as CSDM.     

Sperm usage in honey bees

Sperm usage was investigated in a naturally mated honey bee queen. We collected worker progeny arising from eggs that were laid sequentially during three sampling periods. Paternity was determined by analysis of three polymorphic microsatellite loci, leading to the conclusion that the queen had mated with seven males. Direct analysis of the sperm from the spermatheca revealed no evidence that sperm from additional males was present inside the spermatheca. Frequencies of different subfamilies differed significantly and ranged from 3.8% to 27.3%. In the short term, the frequencies of subfamilies among the eggs laid did not change over time. The frequency of eggs of a particular subfamily was statistically independent of the previous egg's subfamily. Thus, there is no evidence for non-random fine-scale sperm usage, and we estimate the effect of sperm clumping to be less than 6%. We conclude that the sperm is mixed completely inside the queen's spermatheca. Our results suggest that taking brood samples from comb cells next to each other is a statistically correct way of independent sampling of subfamilies at a given time in honey bee colonies. Furthermore, any bias in subfamily frequencies in offspring queens due to sperm usage can be excluded. However, the analyses of progeny samples taken 12 months apart do not allow us to exclude moderate fluctuations of subfamily frequencies in the long-term. Received: 11 August 1997 / Accepted after revision: 14 November 1997     

Domestic energy usage and its' health implications on residents of the Ese‐Odo and Okitipupa local government areas of Ondo state,Nigeria

This study examined domestic energy usage and its health implication on residents of Ese‐Odo and Okitipupa Local Government Areas (LGA), of Ondo State. Systematic random sampling was used to select 103 and 156 respondents in Ese‐Odo and Okitipupa LGA, respectively. It was established that environmental and socio‐economic related attributes influenced residents' choice of domestic energy type. Similarly, burns, blindness, stroke, cataract and pulmonary diseases were the most prevalent self‐reported ill‐health. A relatively weak correlation between domestic energy usage and ill‐health is experienced by the residents. Therefore, the study concluded that the use of traditional energy types had significant adverse effects on the health of the residents in Okitipupa and Ese‐Odo LGAs of Ondo State.     

Public Investment and Environmental Sustainability of Agricultural Production in China

The excessive application of fertilizer and pesticides in grain production in China has posed a threat to the environmental sustainability of agricultural production. One of the major reasons of the increasing usage of chemical inputs by farmers is their trying to reach higher yields, especially in absence of adequate public inputs, such as development and extension of appropriate technology and necessary production infrastructure, etc. Based on the crop specific data of the past 20 years, this paper examines how the public investments in agricultural researches could impact on the reduction of farmers' private material inputs of major grain crops in China. It manifests that the increased investments in public sector, especially in agricultural researches, is a favorable and effective way to reduce farmers' private material inputs and should be given a priority consideration in the policy emendation to increase yields and improve production sustainability.     

2000～2015年中国地级市化肥使用量的时空变化特征

化肥在农业生产中对粮食增产起到至关重要作用,但过量使用也带来诸如地表水富营养化、土壤结构恶化及农业承载力下降等一系列环境问题.目前对于化肥的研究多集中于利用效率方面,而空间变化特征的研究很少,充分认识化肥使用量空间上的变化对我国农业的可持续发展同样具有重要意义.基于2000~2015年全国地级市化肥折纯使用量和播种面积、粮食产量等数据,采用空间自相关分析、冷热点分析、核密度分析和标准差椭圆分析等方法,比较了2000、2005、2010和2015年这4年全国尺度各地区化肥使用总量及单位面积化肥使用负荷的时空变化特征.结果表明：①2000~2015年我国的化肥折纯使用量呈直线增加趋势,而在区域内一直处于比较高的集聚状态.化肥折纯使用量经历2000~2005年区域聚集状态增强,2005~2010年聚集状态减弱,2010~2015年又增加的过程.②从全国化肥使用的空间分布来看,2000~2015化肥使用总量呈现增加趋势,主要表现在化肥使用量超标的地级市变多,区域变广.东部经济发展较快的地区,如广东省和福建省由于播种面积减少比例大于化肥使用量的增长比例,导致超标地级市较为密集.③2000~2015年我国粮食重心的移动轨迹和化肥使用量的移动轨迹不相符,粮食重心往东北地区移动,而化肥使用量的重心往西部移动.一是表明东北地区的商品粮地位越来越重要,二是表明我国西部地区化肥使用量逐渐增加,有超标的趋势,应加以重视.