Plastic marine debris: sources,impacts and management

Marine plastic has many negative impacts on coastal countries, including Vietnam. Vietnamese waters face problems of marine pollution owing to plastic waste. There are few studies on controlling marine plastic waste generated by marine-based activities. Therefore, this paper aims to provide a general view of marine plastics based on existing academic articles, and the impacts on marine animals and on human health. The paper includes a brief account of the quantity of marine plastic waste on coastal Vietnam and offers some recommendations for Vietnam to minimise and manage plastic waste generated by ships.     

论塑性因子与塑性时间的一般关系

 确定材料特定的内蕴时间表达式,是内时塑性力学建模的难点之一,依据原有的内蕴时间定义,也难以探明塑性增量理论和内时塑性理论之间的联系。为此,给出新的内蕴时间——塑性时间的定义,旧的内蕴时间是塑性时间的特例。根据塑性时间的定义,塑性增量力学理论是内时塑性力学理论的特例,塑性增量理论的塑性因子属于内时塑性理论的塑性时间,因此通过塑性因子的表达式可以获得塑性时间的表达式。材料已有的塑性试验表明,不同材料具有不同的塑性因子,由此确定的塑性时间也因材料而异。众多实例阐明推导塑性时间表达式的具体过程,提供利用塑性时间和脉冲函数把塑性增量力学本构模型推广为积分型内时塑性模型的一般方法。     

Implication of heavy metals distribution for a municipal solid waste management system--a case study in Shanghai

Heavy metal contamination in municipal solid waste (MSW) is of increasing concern. The occurrence and distribution of heavy metals in MSW and their implications for the integrated MSW management system in mega-cities have been investigated by means of material flow analysis based on a case study of Shanghai in China. A good statistical basis was provided through a one-year monitoring program on the mass and metals composition of the waste from three MSW treatment facilities. The results showed that the main heavy metals in the MSW were Zn, Cr, Cu, and Pb (on average >100 mg kg(-1)), followed by Ni, Cd, and Hg. The MSW contained higher levels of Cu and Ni in metals, Cr and Pb in plastics, and Pb and Zn in the inorganic fractions. Regardless of the sources, the statistically similar heavy metal contents in the organic fractions indicated that effective blending and diffusion of heavy metals had taken place throughout the MSW collection, transfer, transportation, and storage, leading to cross-contamination of the waste fractions. PU (composed of putrescible waste and miscellaneous indistinguishable particles) contributed the majority of the heavy metals to the MSW, followed by plastics, as a result of the predominance in the overall composition of PU and plastics rather than from differences in their heavy metal contents. Therefore, manual or mechanical separation of some significantly heavy metal-rich fractions alone is not sufficient to reduce the heavy metal contents in the MSW. Source separation of organic waste and the diversion of tailored inorganic waste such as hazardous components, construction and demolition waste, etc., are proposed to control the heavy metal contamination in MSW. For the mixed MSW management system, physicochemical fractionation to exclude particles containing high levels of heavy metals can be conducted.     

Estimation of the mass-balance of selected metals in four sanitary landfills in Western Norway, with emphasis on the heavy metal content of the deposited waste and the leachate

A worst-case simulation of the mass-balance for metals in the waste deposited during 1 year and the levels of cadmium (Cd), lead (Pb), mercury (Hg), chromium (Cr) and iron (Fe) in the leachate was calculated for four sanitary landfills in Western Norway. Estimates of the levels of metal content in mixed municipal solid waste (MSW) were found by using recent literature values calculated in a mass-balance study at a Norwegian waste incinerator plant. Leachate from the landfills were sampled and analyzed monthly during 1 year, and from these measurements the total annual discharge of the selected metals through the leachate was determined. The levels of the measured heavy metals in the leachate were low. For Cd less than 0.06%, for Pb less than 0.01% and for Hg less than 0.02% of the estimated year's deposited mass of metals were leached from the landfills during the year of investigation. The high retention of these metals are most likely due to sulfide precipitation, but also due to the immobile condition of the metals in their original deposited solid state (plastics, ceramics, etc.). The percentage of Cr leached was relatively higher, but less than 1.0% per year. The mass balance of Fe suggests that this element is more mobile under the prevailing conditions. The percentage of Fe leached varied and was estimated to be between 1.9% and 18%. The present study clearly supports the theory that MSW only to a small extent will lead to discharge of metals if deposited at well-constructed sanitary landfills with top layers.     

建筑垃圾资源化再利用方兴未艾

有人曾提出这样一个问题:十年来我们周围最大的变化是什么?几乎半数的人给出的回答都是城市面貌。随着城镇化步伐的加快,一间间危楼平房被高楼大厦所置换,上百条马路、胡同被一条条通衢大道取代,每次走在光鲜灿亮的大街上,您想没想过这样一个问题,那些被拆除下来的建筑垃圾哪里去了?每年大量的施工建设和拆迁改造工程不可避免地产生数亿吨     

采用修正塑性功硬化参数的双屈服面模型及应用

 首先对国内外双屈服面模型的发展进行回顾,指出土体模型中双屈服面概念的必要性和合理性。其次以平面应变试验结果为基础,直接推导出双屈服面模型各部分关系式,其中体积屈服面以塑性功为硬化参数,硬化函数与试验结果吻合程度较好,剪切屈服面以修正塑性功为硬化参数,满足了其与硬化面关系唯一性的要求,并可反映硬化–软化全过程。为使其能较方便地应用于数值计算方法,推导适用于双屈服面模型的弹塑性刚度矩阵。最后应用该模型对一高填土工程的变形进行计算,比较显示其与实测结果较为吻合。     

木－塑复合材料建筑模板的研制

木－塑复合材料建筑模板是利用废旧热塑性塑料与大比例木屑和必要添加剂，经适当复合工艺生产的木－塑复合材料，与木框架固定组合而成的一种新型建筑模板。它具有重量轻、抗湿性能好、耐磨性能好、使用率高、便于施工和保证混凝土表面质量等特点。     

可塑城市: 基于塑料的基础设施 与气候适应性沿海社区构建

Many of the world’s coasts are becoming increasingly urbanized, with two-fifths of cities with populations of millions located near coastlines. Coastal settlements have always been attractive due to the provision of critical inputs to industries, despite the many threats — floods, typhoons, tsunamis, etc. With the Southeast Asian market expected to become the fifth largest economy by 2020, migration from rural to urban areas is set to increase, putting a strain on existing infrastructures within the cities, one of which is the solid waste disposal and recycling infrastructure within the developing nations in Southeast Asia. Currently in the age of the Anthropocene, it is clear that human has greatly reshaped the Earth, bending nature into the course of human wishes, terraforming the land with landfills, mines, and patchwork agriculture fields, choking the atmosphere with toxic emissions, and cloging the seas with plastic waste. Inadequate waste disposal management has resulted in poorly managed landfills with waste being washed into water during rainy seasons, jeopardizing the environment and local communities (typically the most vulnerable ones) that depend on it. This project hopes to explore the nature of plastics, by envisioning a “mechanic landscape” that manages waste input within rivers whilst creating a speculative infrastructural network that varies with environmental conditions (such as global warming and sea-level rise).     

Fire Emissions of Organics into the Atmosphere

The mass of dioxins, PAH (polycyclic aromatic hydrocarbons) and VOC (volatile organic compounds) emitted from fires to the atmosphere in Sweden per year has been estimated. The estimate is based on the number of fires in buildings, vehicles, waste and forest fires in Sweden in 1999. It is estimated that the total emission of dioxins from fires is in the range 0.5–1.4 g TEQ. The total emissions of PAH and VOC are in the ranges 2–12 ton and 13–200 ton, respectively. The estimated emission of dioxins from fires approximately corresponds to the total emission from traffic or half the emissions from municipal waste combustion (Swedish data from 1993). The fire statistics show that the mass of material combusted in building fires during a year is approximately 7500 ton, while that from forest fires is 2600 ton. Additionally, 2000–3000 tons are combusted in vehicle fires, fires in containers, etc. In addition to the more common types of fires during a year, individual large incidents may contribute significantly to the total emission. Such incidents include fires in municipal landfills or specific waste storage facilities (such as those for used tyres). An assessment of the consequences of such incidents has been made. This assessment implies that a large contribution to the emission of dioxins could be expected from fires in landfills and from fires in waste plastics (PVC) and tyres. Fires in deposits of wood chips and tyres are also significant potential sources of PAH and VOC.     

玄武岩纤维复合筋与混凝土握裹强度的试验研究

玄武岩纤维复合筋是我国战略性新兴产业重点产品。玄武岩纤维复合筋为无机材料,与混凝土基体有很好的兼容性,耐海水腐蚀性好,在替代钢筋用于海洋地材混凝土方面具有很大潜力。对比测试了玄武岩纤维复合筋与淡水河砂混凝土、玄武岩纤维复合筋与海水海砂混凝土、钢筋与淡水河砂混凝土、钢筋与海水海砂混凝土的握裹强度,试验发现玄武岩纤维复合筋与混凝土握裹强度比钢筋与混凝土握裹强度高;玄武岩纤维复合筋与海水海砂混凝土的握裹强度比玄武岩纤维复合筋与淡水河砂混凝土握裹强度高;玄武岩纤维复合筋与混凝土握裹强度极差较大。     

Characterization of medical waste from hospitals in Tabriz, Iran

Medical waste has not received enough attention in recent decades in Iran, as is the case in most economically developing countries. Medical waste is still handled and disposed of together with domestic waste, creating great health risks to health-care stuff, municipal workers, the public, and the environment. A fundamental prerequisite for the successful implementation of any medical waste management plan is the availability of sufficient and accurate information about the quantities and composition of the waste generated. The objectives of this study were to determine the quantity, generation rate, quality, and composition of medial waste generated in the major city northwest of Iran in Tabriz. Among the 25 active hospitals in the city, 10 hospitals of different size, specializations, and categories (i.e., governmental, educational, university, private, non-governmental organization (NGO), and military) were selected to participate in the survey. Each hospital was analyzed for a week to capture the daily variations of quantity and quality. The results indicated that the average (weighted mean) of total medical waste, hazardous-infectious waste, and general waste generation rates in Tabriz city is 3.48, 1.039 and, 2.439 kg/bed-day, respectively. In the hospital waste studied, 70.11% consisted of general waste, 29.44% of hazardous-infectious waste, and 0.45% of sharps waste (total hazardous-infectious waste 29.89%). Of the maximum average daily medical waste, hazardous-infectious waste, and general waste were associated with N.G.O and private hospitals, respectively. The average composition of hazardous-infectious waste was determined to be 35.72% plastics, 20.84% textiles, 16.70% liquids, 11.36% paper/cardboard, 7.17% glass, 1.35% sharps, and 6.86% others. The average composition of general waste was determined to be 46.87% food waste, 16.40% plastics, 13.33% paper/cardboard, 7.65% liquids, 6.05% textiles, 2.60% glass, 0.92% metals, and 6.18% others. The average bulk densities of total medical waste, hazardous-infectious waste, and general waste were determined to be 99.58, 96.16 and 101.26 kg/m³, respectively. Significant differences were observed between the medical waste characteristics of the hospitals studied here and those reported in other studies. In conclusion, the characteristics of generated medical waste, current environmental problems and strict budgets necessitate that the implementation of efficient management, training, and segregation program be top priorities if we are to minimize the treatment and disposal costs and reduce the risks of hazardous-infectious waste in Tabriz city.     

岩石隧道塑性位移新解

 在统一强度理论和弹脆塑性模型的基础上,考虑塑性区围岩弹性模量的变化、中间主应力效应、围岩应变软化和剪胀等影响,推导了深埋圆形岩石隧道塑性位移新解。文中的隧道位移新解具有广泛的理论意义,可根据具体工程实际情况,进行多种合理选择。经工程算例分析可知,由塑性区半径相关的弹性模量计算得到的位移处于上、下限之间,反映了隧道开挖卸荷扰动影响的距离变化,更符合隧道变形真实情况,并得出统一强度理论参数和剪胀特性参数对塑性区位移的影响规律。研究结果表明：隧道塑性区位移受中间主应力、围岩剪胀特性和塑性区弹性模量的影响显著,三者相互影响,共同作用。     

北京市建筑垃圾减量化规划应对策略研究

我国城市已进入快速发展阶段,城市建设量增加,导致城市建筑垃圾产生量逐年递增,对环境造成巨大压力,因此建筑垃圾减量化处理刻不容缓.通过阐述国外建筑垃圾治理模式,分析北京市建筑垃圾处理现状及问题,最后从建筑垃圾治理与城市国土空间规划体系相衔接、构建建筑垃圾全过程减量化模式、完善建筑垃圾治理法律法规体系3个方面,提出北京市建...     

塑料模板的性能及其应用施工技术

PVC木塑建筑模板和改性增强聚丙烯复合材料模板是目前应用较成熟的塑料模板,塑料模板加工制作及施工工艺同木模板较相似,但在工程实践中,应考虑塑料模板的材质特性,制定工艺标准,以满足工程施工要求。     

MBT垃圾的三轴试验结果

采集杭州天子岭垃圾填埋场的MBT垃圾,在环境土工实验室进行了成分分析、试样制备、三轴快剪、固结快剪和慢剪试验,对MBT垃圾的剪切强度特性进行了系统地研究。结果表明:①MBT垃圾的组分主要以塑料、纺织物、玻璃、灰土和无法识别的材料为主。②随着轴向应变的增大,偏应力逐渐增大,轴向应变超过30%后仍没达到峰值,是一条应变硬化曲线。③得到了三轴快剪、固结快剪和慢剪试验条件下抗剪强度参数(黏聚力和内摩擦角)的取值范围。④MBT垃圾的抗剪强度参数与轴向应变的关系可拟合为直线关系,建立了抗剪强度参数与轴向应变的线性关系表达式。⑤MBT垃圾的应力–应变关系符合邓肯–张模型,得到了模型参数a,b的取值范围,建立了模型参数a,b与围压的幂函数关系表达式。研究结果可为MBT垃圾填埋场的稳定性分析提供理论基础。     

废弃PE裂解蜡作为沥青温拌剂的可行性研究

以高密度聚乙烯(HDPE)和低密度聚乙烯(LDPE)共混废塑料为原材料,在不同温度下裂解得到的2种裂解蜡WMa-1和WMa-2,采用该裂解蜡对70~#基质沥青进行改性,探讨聚乙烯废塑料裂解蜡作为沥青温拌添加剂的可行性。试验结果表明,在试验掺量范围内,WMa-1和WMa-2均具有良好的降黏效果,WMa-1能提高沥青的高温性能和抗车辙性能,但对沥青的低温性能不利;WMa-2能显著降低沥青硬度,改善沥青的低温塑性,但使沥青的高温抗变形能力明显降低。     

人工塑性铰的功能及其合理位置

本文包括三部分,第一部分对文献(1)所建议的人工塑性铰在框架结构中应用的优点进行了论述;第二部分对设置人工铰的合理位置进行了探讨,结果表明,将梁铰从梁根转移出一个梁高h_o的建议是可取的;第三部分是结束语。     

多孔岩石塑性压缩本构模型研究

白垩是一种典型的多孔岩石,三轴试验研究成果表明白垩具有2种塑性力学机理:塑性压缩(孔隙坍塌)和剪切破坏。孔隙度对白垩的塑性力学特征有重要影响,在描述白垩塑性行为的本构方程中,特别是描述塑性压缩(孔隙坍塌)的塑性力学机理,需要考虑孔隙的影响。基于对白垩力学机理的认识,建立了基于Gurson屈服准则的本构关系用来描述白垩的塑性压缩(孔隙坍塌)机理的本构模型,模拟结果与试验成果相一致。     

广义塑性力学中的屈服面的研究

基于广义塑性力学，详细讨论了屈服面和塑性势面的对应关系以及岩土材料的3类屈服面（即体积屈服面q方向上及θσ方向上的剪切屈服面）的基本特征，尤其是提出了能考虑剪胀与剪缩的体积屈服面和Lode角θσ方向的剪切屈服面。     

生活垃圾综合处理前分选工艺的调试研究

以重庆市涪陵区李渡镇生活垃圾处理厂为例,分析了前分选工艺在垃圾综合处理中的减量化和资源化效果,探讨了前分选工艺对提高生活垃圾综合处理水平的作用。结果表明:通过对原生垃圾进行分选,使堆肥物料、可回收物料和填埋物料实现了有效分流。其中,一次发酵仓的堆肥物料质量相对于原生垃圾减少了16.6%,堆肥物料容积减少了51.4%,堆肥物料的密度增加了67%,且较均匀、含水率低,提高了物料的堆肥特性。通过对前分选工艺各分选出料口物料的分析,前分选工艺对金属的分选效率为92.0%,对塑料的分选效率为63.5%,对玻璃的分选效率为33.0%,分选出的可回收物料质量占分选线分选出物料总量的44.2%,提高了原生垃圾的资源化水平。