Development of functionally-graded cementitious panel against high-velocity small projectile impact

A functionally-graded (FG)-cementitious panel consisting of PE-fibrous ferrocement, calcined bauxite aggregates and conventional mortar was developed to resist high-velocity small projectile penetration. A total of 72 specimens measuring 200 mm by 200 mm by 100 mm were fabricated and subjected to ogive-nosed (Caliber Radius Head, CRH = 2.5) projectile impacts at velocities ranging from 300 m/s to 600 m/s. The results indicated that FG-panels have superior impact resistance compared to plain mortar targets in which all FG-panels remained intact, whereas the latter disintegrated into several pieces when the projectile velocity exceeded 300 m/s. The FG-panels also suffered minor front face damages with much smaller average crater diameters (<48 mm) compared to plain mortar targets (>100 mm). However, penetration depths in the FG-panels were slightly larger at impact velocity less than 400 m/s compared to the mortar panels due to the lower compressive strength of PE-fibrous ferrocement. At higher impact velocity, all penetration depths in FG-panels were smaller than those in plain mortar targets. The effects of thickness variation of each functional layer were also investigated and results showed that thickening the calcined bauxite aggregate layer was most effective in reducing the penetration depth for all impact velocities, but the average inner and outer crater diameters were slightly increased.     

钢中合金元素成分起伏对韧脆转变温度的影响

某材料为16MND5的压力容器筒体,在进行低温-20℃冲击试验时,取样位置邻近试样的冲击功却相差很大。通过对冲击功不同的试样分别进行金相检验、断口分析、化学成分分析以及能谱微区成分分析,找出了冲击功相差较大的原因。结果表明:冲击功较低试样中的钼和硅等元素微观聚集程度比冲击功较高试样中的严重,尤其是钼元素的微观聚集更为严重;由于合金元素钼和硅在钢中能提高钢的韧脆转变温度,因此偏聚严重就会导致材料在低温冲击时的冲击功相差较大;由此可以判定是由于热处理工艺不当,造成了钼和硅等合金元素的严重微观聚集,致使材料出现冲击韧度不均匀、相邻位置冲击功相差较大的问题。     

An artificial neural network model for virtual Superpave asphalt mixture design

This study presents an artificial neural network (ANN) model to predict the asphalt mixture volumetrics at Superpave gyration levels. The input data-set needed by the algorithm is composed of gradation of the mix, bulk specific gravity of aggregates, low- and high-performance grade of the binder, binder content of the mix and the target number of gyrations (i.e. N_ini, N_des and N_max). The proposed ANN model uses a three-layer scaled conjugate gradient back-propagation (feed-forward) network. The ANN was trained using data obtained from numerous roads with a total of 1817 different mix designs. Results revealed that the ANN was able to predict V_a within V_a (measured) ± 1.0% range 85–93% of the time and within V_a (measured) ± 0.5% range 60–70% of the time. Currently with the developed ANN model, Superpave mix design can take approximately between 1.5 and 4.5 days, which corresponds to 3–6 days of savings.     

The impact assessment we want

The impact assessment (IA) we want seeks to balance the ‘productive harmony’ between people and nature by enhancing the quality of life while maintaining the integrity of natural systems. Its focus centers on ‘sustainable futures’ as the goal of integrated IA.     

电爆网路联接方式对准爆可靠性的影响

煤矿采掘和地面爆破施工中,爆破可靠性是个重要环节。发生在串联网路或串并朕网路中部的成组拒爆,或者只有一端爆炸的情况,往往令爆破作业者费解。该研究一改往常定性方法描述不良爆破的征兆,通过试验、理论推导、定量分析,评价电爆网路中出现的成组拒爆现象。     

进口分箱机的适用性改造

本文介绍了进口托板式分箱机在现有生产条件下运作出现的问题和原因,以及根据实际生产条件进行改造的设计方案和所取得的效果。     

Critical review of methods for risk ranking of food-related hazards,based on risks for human health

This study aimed to critically review methods for ranking risks related to food safety and dietary hazards on the basis of their anticipated human health impacts. A literature review was performed to identify and characterize methods for risk ranking from the fields of food, environmental science and socio-economic sciences. The review used a predefined search protocol, and covered the bibliographic databases Scopus, CAB Abstracts, Web of Sciences, and PubMed over the period 1993–2013.

All references deemed relevant, on the basis of predefined evaluation criteria, were included in the review, and the risk ranking method characterized. The methods were then clustered—based on their characteristics—into eleven method categories. These categories included: risk assessment, comparative risk assessment, risk ratio method, scoring method, cost of illness, health adjusted life years (HALY), multi-criteria decision analysis, risk matrix, flow charts/decision trees, stated preference techniques and expert synthesis. Method categories were described by their characteristics, weaknesses and strengths, data resources, and fields of applications.

It was concluded there is no single best method for risk ranking. The method to be used should be selected on the basis of risk manager/assessor requirements, data availability, and the characteristics of the method. Recommendations for future use and application are provided.     

多轴向经编曲面复合材料汽车门低速碰撞数值模拟

为探究多轴向经编曲面复合材料汽车壳体的抗冲击性能,揭示该材料在乘用车领域的应用优势,本文采用有限元方法对多轴向经编曲面复合材料乘用车车门的低速碰撞性能进行了模拟分析。通过对多轴向曲面复合材料车门与传统SAPH440钢车门进行建模、低速碰撞数值模拟,对比分析了二者在应力分布、车门侵入量、侵入速度和车门内能等多个角度的性能差异,并从保护车内成员安全和轻量化等方面进行探讨。研究表明,与传统钢材料车门相比,多轴向经编曲面复合材料车门在受到低速碰撞时变形更小、能量吸收性能更强,在一定程度上加强了对车内人员的保护。另外,该材料的应用使车身大幅减重,实现乘用车的轻量化。     

不同槽数槽轮机构的运动特性分析

根据运动曲线无因次化表示方法,对槽轮机构运动规律进行了分析,得到了不同槽数槽轮机构运动规律无因次化曲线,并得出随着槽数的减少,机构惯性冲击增大的结论。     

Consumption and production waste: another externality of tobacco use

OBJECTIVE: To describe the waste produced by and environmental implications of individual cigarette consumption (filter tips, packages, and cartons) and tobacco manufacturing. STUDY SELECTION: All available articles and reports published since 1970 related to cigarette consumption and production waste were reviewed. DATA SOURCES: Global cigarette consumption data were used to estimate cigarette butt and packaging waste quantities. Data from the Center for Marine Conservation's International Coastal Cleanup Project were used to describe some environmental impacts of tobacco-related trash. Data from the United States Environmental Protection Agency's (EPA's) Toxics Release Inventory and reported global cigarette consumption totals were used to estimate waste production from cigarette manufacturing. DATA EXTRACTION AND SYNTHESIS: In 1995, an estimated 5.535 trillion cigarettes (27,675 million cartons and 276,753 million packages) were sold by the tobacco industry globally. Some of the wastes from these products were properly deposited, but a large amount of tobacco consumption waste ends up in the environment. Some is recovered during environmental clean-up days. For the past eight years (1990-1997), cigarette butts have been the leading item found during the International Coastal Cleanup Project; they accounted for 19.1% of all items collected in 1997. The tobacco manufacturing process produces liquid, solid, and airborne waste. Among those wastes, some materials, including nicotine, are designated by the EPA as Toxics Release Inventory (TRI) chemicals. These are possible environmental health hazards. In 1995, the global tobacco industry produced an estimated 2262 million kilograms of manufacturing waste and 209 million kilograms of chemical waste. In addition, total nicotine waste produced in the manufacture of reduced nicotine cigarettes was estimated at 300 million kilograms. CONCLUSIONS: Laws against littering relative to cigarette butts could be better enforced. Additional taxes might be levied on cigarette products that would then be directed to environmental clean-up efforts. The tobacco industry should improve the biodegradability of filters, reduce packaging waste, and educate its customers. Worksites and public buildings should be encouraged or required to supply appropriate disposal mechanisms at all building entrances. Public awareness campaigns about the magnitude and prevention of cigarette consumption waste could be developed through partnerships among environmental groups, health organisations, and environmental protection agencies. Tobacco production waste should be a source of concern and regulation by governments throughout the world; it contains numerous chemicals which may be considered health hazards, not the least of which is nicotine produced in the manufacture of low-nicotine cigarettes.