Reality and risk of contact-type head injuries related to bicycle-mounted child seats

Objective

The authors have treated numerous children who have been injured by falling from bicycle-mounted child seats. Despite the greatly increased use of such seats, the understanding of their risk and the importance of helmet use remains alarmingly poor. The objective of this study was to confirm the risk of bicycle-mounted child seats and to evaluate the efficacy of helmets, seat belts, and back seat height in terms of preventing or mitigating contact-type head impacts that occur in falls from bicycle-mounted child seats.

Materials and methods

Biometrical dummy tests were performed to examine contact-type head injuries in falls from stationary bicycles. A bicycle with an anthropometric test dummy placed in a bicycle-mounted child seat was tipped over. Each test was repeated three times and three-dimensional acceleration was measured using accelerometer. Head Injury Criteria (HIC) were calculated and the respective influences of a helmet, a seat belt, and increased height of the back of the seat on such impacts were evaluated.

Results

Only helmets unequivocally lowered maximal acceleration and/or HIC values with statistical significance. The seat belt lowered HIC values as long as it was used with the high-back seat. Only when the dummy wore a helmet sitting in a high-back seat did the HIC show less than the threshold of 570 for three-year-old children. The HIC showed the lowest score of 161.5 when the dummy wore both a helmet and a seat belt sitting in a high-back seat.

Conclusions

Riders in bicycle-mounted child seats definitely have higher risks of contact-type head injuries. In transporting a child on a bicycle-mounted child seat, parents must use both a child-bicycle helmet and a high-back child seat at least; a seat belt is highly recommended as long as it is used with the other safety devices.

Impact on Industry

The bicycle-mounted child seat should have a high enough back and an appropriate seat belt to protect the head of the child from a contact-type injury.     

基于未确知测度理论的安全生产状况评价研究

为研究我国省市的安全生产级别,基于未确知测度理论,建立安全生产状况评价的等级模型。根据实际情况,选取5项评价指标,建立各评价指标的未确知测度函数。利用熵确定各项指标的权重,避免人为主观性对评价的影响,根据多指标综合测度评价向量和置信度识别准则进行评判。结合2009年9省市对应指标统计数据,采用未确知理论对安全生产状况进行评价,并结合实际进行分析。该理论为省、市安全生产提供了指导性的建议和依据。     

Siting and Routing Assessment for Solid Waste Management Under Uncertainty Using the Grey Mini-Max Regret Criterion

Solid waste management (SWM) is at the forefront of environmental concerns in the Lower Rio Grande Valley (LRGV), South Texas. The complexity in SWM drives area decision makers to look for innovative and forward-looking solutions to address various waste management options. In decision analysis, it is not uncommon for decision makers to go by an option that may minimize the maximum regret when some determinant factors are vague, ambiguous, or unclear. This article presents an innovative optimization model using the grey mini-max regret (GMMR) integer programming algorithm to outline an optimal regional coordination of solid waste routing and possible landfill/incinerator construction under an uncertain environment. The LRGV is an ideal location to apply the GMMR model for SWM planning because of its constant urban expansion, dwindling landfill space, and insufficient data availability signifying the planning uncertainty combined with vagueness in decision-making. The results give local decision makers hedged sets of options that consider various forms of systematic and event-based uncertainty. By extending the dimension of decision-making, this may lead to identifying a variety of beneficial solutions with efficient waste routing and facility siting for the time frame of 2005 through 2010 in LRGV. The results show the ability of the GMMR model to open insightful scenario planning that can handle situational and data-driven uncertainty in a way that was previously unavailable. Research findings also indicate that the large capital investment of incineration facilities makes such an option less competitive among municipal options for landfills. It is evident that the investment from a municipal standpoint is out of the question, but possible public–private partnerships may alleviate this obstacle.     

电袋复合除尘器气流分布技术及评判标准研究

从电袋复合除尘器的基本原理出发,提出对其进行气流组织的三个关键点,并从理论上对影响电袋复合除尘器性能的烟气冲刷速度、逆重力向速度分量（CANE速度）、静电区除尘效率、静电区气流均匀性系数、净气室及出口烟道的设计等方面进行了研究。     

论“三级三循环”耕地保护利益补偿模式的构建

我国耕地保护应更多侧重对耕地保护实施主体的内在激励,因此建立耕地保护利益补偿机制是实现我国切实保护耕地的关键环节。结合近期有关耕地保护利益补偿模式的研究成果,本文从耕地保护的外部性没有得到相应的经济体现、耕地保护政策损益补偿机制不健全、现行耕地保护的委托—代理机制具有较高的效率损失风险、耕地保护的区域差异性在经济上未得到有效体现、耕地资源价值核算不完善和由于比较利益的存在使得农户保护耕地的积极性不高等六大方面系统分析了我国现行耕地保护制度缺陷,提出了建立"三级三循环"耕地保护利益补偿模式的新思路。在此基础上,对"三级三循环"耕地保护利益补偿资金的筹集和使用、补偿主体、补偿标准、补偿方式等进行了详细论述。最后,从建立"三级"耕地保护基金管理委员会、对城镇居民开征耕地保护税、建立受偿农户耕地保护补偿账户体系以及加强对各级耕地保护基金管理委员会的监督管理等方面提出了政策建议。本文的分析结果对于推进我国耕地保护经济补偿,实现切实保护耕地目的具有一定的理论参考价值。     

降雨引发排土场滑坡的预警准则研究*

为降低降雨引发排土场滑坡的风险,提出更加科学、实用的降雨滑坡预警准则,以贵州某矿山排土场的实际情况为例,建立排土场在线监测预警系统,并基于FLAC3D软件,对安全系数与边坡位移的关系以及降雨与边坡位移的关系进行数值模拟。结果表明:降雨是影响排土场滑坡的主要因素,且降雨影响具有滞后性,降雨量可作为排土场滑坡的预警指标;排土场滑坡预警等级与排土场安全系数存在密切相关性,可根据排土场安全系数确定滑坡红、橙、黄、蓝预警等级;可根据模拟结果确定降雨引发排土场滑坡的预警准则。研究结果具有较强的实用性,为排土场滑坡事故的预防和控制提供科学指导。     

基于Mogi-Coulomb强度准则的井壁稳定性力学分析新方法*

传统井壁坍塌失稳分析模型是基于M-C破坏准则而建立的,该方法忽略了中间主应力对岩石强度的影响,常使得预测的钻井液密度过于保守。为此,引入考虑中间主应力的Mg-C破坏准则建立任意井眼的井壁稳定性评价新模型,通过数值模拟法分析了不同地应力状态下的井斜角和方位角对井壁稳定性的影响。研究结果表明: Mg-C准则克服了M-C准则忽略中间主应力低估岩石强度的影响,其计算结果略低于M-C准则的计算结果,有助于提高钻速,降低钻井成本;正断层地应力状态时,沿最小水平主应力方向钻进时,井壁稳定性最好;走滑断层地应力状态时,沿最大与最小水平主应力之间的某一临界角钻进时井壁最稳定;逆断层地应力状态时,沿最大水平主应力方向钻进时井壁最稳定;该模型有助于指导现场钻井井眼轨迹的优化设计及安全施工。     

某恒温间歇反应的热失控研究

为得到某恒温间歇反应冷却系统临界温度Tc并评估该反应体系的热危险性,基于间歇反应体系热参数的敏感性,探讨数值计算方法和选用4种反应热失控临界判据得到的不同Tc值。结果表明,数值计算方法得到了反应体系的Tc为31.7℃,Semenov判据、Sliding判据、Da/St判据得到的Tc值分别为10℃,17℃和27℃;无量纲绝热温升B给出的结论是,在允许的工艺温度范围内,该反应对任意的冷却系统温度都处于难以控制状态。数值计算方法及各判据得到的Tc的较大差异性说明各方法均有一定的局限性。在运用参数敏感性分析的基础上,结合风险矩阵图方法对系统冷却失效的热危险性进行评估,得到不同Tc下风险可接受、有条件接受及不可接受对应的参数范围的物料累积度Xac与最大反应速率到达时间θ间的关系。     

Numerical modelling of electrohydraulic free-forming and die-forming of DP590 steel

Electrohydraulic forming (EHF) is a high energy rate forming process in which the strain rate in the sheet metal can vary from 5 × 10² to 10⁵ s⁻¹ depending on various factors. Several mechanisms have been reported to cause an improvement in formability in EHF such as material deformation mechanisms, inertial effects and the dynamic impact of the sheet against the die. EHF is a complex high speed forming process and experimental work alone is not sufficient to properly understand this process. To understand the variation of some influential variables in EHF, electrohydraulic die-forming (EHDF) and free-forming (EHFF) of DP590 dual phase steel were simulated in ABAQUS/Explicit by considering the fluid/structure interactions. Three-dimensional finite element simulations were conducted by modelling the water with Eulerian elements with a view to investigating the effect of released energy on the sheet deformation profile history, strain distribution, loading path and damage accumulation type. The Johnson–Cook constitutive material model was used to predict the sheet behaviour and the parameters in this model were calibrated based on experimental test results available for DP590 at various strain rates. The Johnson–Cook phenomenological damage model was also used to predict the ductile failure (damage accumulation) in both EHDF and EHFF. Predicted final strain values and damage accumulation type showed good agreement with the experimental observations.     

中国绿色食堂评价指标体系构建

绿色食堂是实现绿色餐饮的重要构成,构建科学的绿色食堂评价指标体系对餐饮业健康良性发展十分关键。目前,国内缺乏关于绿色食堂的有效评价指标体系。本文遵循目的性、科学性、系统性、可行性、动态性五大原则,探索构建了中国绿色食堂评价指标体系。该体系从反食品浪费与绿色消费、食品安全与营养、节能减损、污染物控制、绿色服务与运营管理5个方面17个指标给出相应的评价标准并赋权。最后,本文以高校食堂为例,通过全国层面的数据调查和个别高校的案例研究,从反食物浪费的现实需求和消费者认同视角,证实了评价绿色食堂需要对反食品浪费和绿色消费指标予以高度重视。本文为绿色食堂评价指标体系的完善提供了初步依据,有助于《反食品浪费法》在食堂场所的实施实践。