The goal of this work was to study the mechanical behavior of concrete with recycled Polyethylene Therephtalate (PET), varying the water/cement ratio (0.50 and 0.60), PET content (10 and 20 vol%) and the particle size. Also, the influence of the thermal degradation of PET in the concrete was studied, when the blends were exposed to different temperatures (200, 400, 600 °C). Results indicate that PET-filled concrete, when volume proportion and particle size of PET increased, showed a decrease in compressive strength, splitting tensile strength, modulus of elasticity and ultrasonic pulse velocity; however, the water absorption increased. On the other hand, the flexural strength of concrete-PET when exposed to a heat source was strongly dependent on the temperature, water/cement ratio, as well as on the PET content and particle size. Moreover, the activation energy was affected by the temperature, PET particles location on the slabs and water/cement ratio. 相似文献
Solid waste management is one of the most challenging issues in urban cities, which are facing a serious pollution problem due to the generation of huge quantities of solid waste. This paper presents an assessment of the existing situation of municipal solid waste management (MSWM) in major cities in India. The quantity and composition of MSW vary from place to place, and bear a rather consistent correlation with the average standard of living. Extensive field investigations were carried out for quantification, analysis of physical composition, and characterization of MSW in each of the identified cities. The MSW management status (per the MSW Rules, 2000) has also been assessed, and an action plan for better management has been formulated; both are presented in this paper. Studies carried out in 59 selected cities in India have revealed that there are many shortcomings in the existing practices used in managing the MSW. These shortcomings pertain mainly to inadequate manpower, financial resources, implements, and machinery required for effectively carrying out various activities for MSWM. To overcome the deficiencies in the existing MSWM systems, an indicative action plan has been presented incorporating strategies and guidelines. Based on this plan, municipal agencies can prepare specific action plans for their respective cities. 相似文献
Pollution and health risks generated by improper solid waste management are important issues concerning environmental management in developing countries. In most cities, the use of open dumps is common for the disposal of wastes, resulting in soil and water resource contamination by leachate in addition to odors and fires. Solid waste management infrastructure and services in developing countries are far from achieving basic standards in terms of hygiene and efficient collection and disposal. This paper presents an overview of current municipal solid waste management in Rasht city, Gilan Province, Iran, and provides recommendations for system improvement. The collected data of different MSW functional elements were based on data from questionnaires, visual observations of the authors, available reports and several interviews and meetings with responsible persons. Due to an increase in population and changes in lifestyle, the quantity and quality of MSW in Rasht city has changed. Lack of resources, infrastructure, suitable planning, leadership, and public awareness are the main challenges of MSW management of Rasht city. However, the present situation of solid waste management in this city, which generates more than 400tons/d, has been improved since the establishment of an organization responsible only for solid waste management. Source separation of wastes and construction of a composting plant are the two main activities of the Rasht Municipality in recent years. 相似文献
There has been considerable interest in the use of the biodegradable polymer poly(lactic acid) (PLA) as a replacement for
petroleum derived polymers due to ease of processability and its high mechanical strength. Other material properties have
however limited its wider application. These include its brittle properties, low impact strength and yellow tint. In an attempt
to overcome these drawbacks, PLA was blended with four commercially available additives, commonly known as masterbatches.
The effect of the addition of 1.5 wt% of the four masterbatches on the mechanical, thermal, optical and surface properties
of the polymer was evaluated. All four masterbatches had a slight negative effect on the tensile strength of PLA (3–5% reduction).
There was a four fold increase in impact resistance however with the addition of one of the masterbatches. Differential scanning
calorimetry demonstrated that this increase corresponded to a decrease in the polymer crystallinity. However there was an
associated increase in polymer haze with the addition of this masterbatch. The clarity of PLA was improved through the addition
of an optical brightener masterbatch, but the impact resistance remained low. The glass transition and melting temperatures
of PLA were not affected by the addition of the masterbatches, and no change was observed in surface energy. Some delay in
PLA degradation, in a PBS degradation medium at 50 °C, was observed due to blending with these masterbatches. 相似文献
The flora of Siberia includes 4500 species, 815 genera, and 123 families of angiosperms. The causes of the relationship between sexual forms and such ecological and biological features of plants as the life form, the mode of pollination, pericarp’s consistency, habitat type, zonal group, and the ecological group in relation to moistening were analyzed and discussed. For the first time, we demonstrated that gynomonoecy in the flora of Siberia was associated with a semiwoody growth form, pollination by wind, and propagation in zonal communities. It was revealed that gynodioecy in Siberia was associated with a semiwoody growth form, circumpolar or Eurasian distribution, and floodplain meadows. It was found that the ratio of dioecious and hermaphrodite plants in the ecological-biological complexes of species directly depends on the frequency of the abundance of species with endemic areas. 相似文献
Delivering access to sufficient food, energy and water resources to ensure human wellbeing is a major concern for governments worldwide. However, it is crucial to account for the ‘nexus’ of interactions between these natural resources and the consequent implications for human wellbeing. The private sector has a critical role in driving positive change towards more sustainable nexus management and could reap considerable benefits from collaboration with researchers to devise solutions to some of the foremost sustainability challenges of today. Yet opportunities are missed because the private sector is rarely involved in the formulation of deliverable research priorities. We convened senior research scientists and influential business leaders to collaboratively identify the top forty questions that, if answered, would best help companies understand and manage their food-energy-water-environment nexus dependencies and impacts. Codification of the top order nexus themes highlighted research priorities around development of pragmatic yet credible tools that allow businesses to incorporate nexus interactions into their decision-making; demonstration of the business case for more sustainable nexus management; identification of the most effective levers for behaviour change; and understanding incentives or circumstances that allow individuals and businesses to take a leadership stance. Greater investment in the complex but productive relations between the private sector and research community will create deeper and more meaningful collaboration and cooperation. 相似文献
Does status matter in community-based forest management? If so, are the high-status households more benefited than the low-status households? What drives status differences, if any, in the appropriation of forest resources? To address these questions, we draw on a theory of status and resource use that defines one’s status as one’s relative position in a group on the basis of power, prestige, honor and deference. Following this perspective, we surveyed the heads of 341 forest-based rural households in India from 2009 to 2010. We find that collective actions themselves are status-driven and the high-status households are more interested and involved in status-maintaining collective actions such as decision-making and implementation, while the low-status households perform general tasks like forest patrol. Moreover, the high-status households derive benefits from local forest significantly more than the low-status households. Further, decomposition analysis shows that a household’s prestige and honor measured by its access to social resources, problem faced and useful contacts explain about 56 % of the status gap in forest benefits, while socioeconomic characteristics explain only 16 % of the gap. Thus, due emphasis on household status from a broader socioeconomic perspective is required to reduce inequality in participation and the distribution of forest benefits in co-management. 相似文献
This paper seeks to understand why climate information is produced differently from country to country. To do this, we critically examined and compared the social and scientific values that shaped the production of three national climate scenarios in the Netherlands, Switzerland and the UK. A comparative analysis of documentary materials and expert interviews linked to the climate scenarios was performed. Our findings reveal a new typology of use-inspired research in climate science for decision-making: (i) innovators, where the advancement of science is the main objective; (ii) consolidators, where knowledge exchanges and networks are prioritised; and (iii) collaborators, where the needs of users are put first and foremost. These different values over what constitutes ‘good’ science for decision-making are mirrored in the way users were involved in the production process: (i) elicitation, where scientists have privileged decision-making power; (ii) representation, where multiple organisations mediate on behalf of individual users; and (iii) participation, where a multitude of users interact with scientists in an equal partnership. These differences help explain why climate knowledge gains its credibility and legitimacy differently even when the information itself might not be judged as salient and usable. If the push to deliberately co-produce climate knowledge is not sensitive to the national civic epistemology at play in each country, scientist–user interactions may fail to deliver more ‘usable’ climate information.