1,720,985 research outputs found
Ecological impacts of small hydropower in China: Insights from an emergy analysis of a case plant
No full textThe belief that small hydropower (SHP) systems are sources of clean energy with few or no ecological problems has been driving the rapid expansion of SHP plants in China and elsewhere. This paper presents an evaluation of the ecological impacts of SHP based on an emergy analysis of a plant located in Guizhou Province in southwest China. The results suggest that periodic downstream drying-up of the river is the largest contributor to the induced ecological impacts in terms of emergy cost. In 2010, the ecosystem service losses caused by downstream ecosystem degradation totaled 2.35E+18. seJ, which accounts for 38% of the total emergy utilized in the annual operation of this plant. If such losses could be avoided, i.e., if the SHP operated as designed, SHP projects would produce relatively modest impacts on the environment. When the reaches downstream of the SHP plant are not affected, the environmental loading ratio (ELR) is 2.20 and the emergy sustainability index (ESI) is 0.93; however, the ELR increases to 3.82 and ESI decreases to 0.38 when river drying-up occurs. These results indicate that China should rigorously investigate potential ecological problems of SHP development and proceed with caution rather than readily believing unjustified assumptions
Small hydropower development in China : Growing challenges and transition strategy
No full textWith the great successes in improving rural electrification and reducing poverty, China's small hydropower (SHP) development is expected to provide a good example for other developing countries. However, recently, nearly all new SHP development plans have been halted, and many plants have been urged to shut down or even be removed. The SHP industry in China is now in a dilemma. This paper presents a review of the status of SHP development in China and explores the challenges troubling this industry. It was revealed that SHP resources in many provinces have been intensively exploited, with an exploration rate over 0.80, while untapped resources are primarily located in remote western provinces, such as ecologically fragile Tibet. This intensive and disordered SHP development has caused serious dewatering of rivers and affected local agricultural and household water access, which arouses fierce controversy. Moreover, the role of SHP has been gradually weakened by the extension of power grids and diversified electricity sources. Therefore, the transition and upgrade of the SHP industry has become critical to enhance its sustainable development and to provide a solid example for the world. A divergence management strategy for SHP should be adopted to achieve low-impact development, as opposed to blind large-scale development or rigidly discontinuing all projects. Future transition strategies are proposed in this paper that include delicate management of existing plants and construction of new plants with higher standards, as well as pathways for the development benefits to be shared by a wider range of local residents.</p
Environmental sustainability of small hydropower schemes in Tibet: An emergy-based comparative analysis
No full textExploring safe and sustainable hydropower, with regard to the size and scheme, is of particular importance to avoid unsettling the fragile ecology in Tibet. Through emergy analysis, this study aimed to assess and compare the environmental performance and sustainability of three different small hydropower (SHP) schemes that are currently in use, i.e., dam-toe, diversion and hybrid, in the Nagqu Prefecture of Tibet. The results indicate that the main difference among the three schemes is the high emergy cost associated with the sizeable dam and related sediment deposition. Correspondingly, the diversion scheme without the dam component is superior to the other two schemes with respect to environmental performance. Considering the necessity of SHP in sparsely populated Tibet, the diversion scheme is recommended more highly than the other two schemes for new SHP plants that are being planned for construction. Because of the much higher resource cost but smaller installed capacity, all three case plants in Tibet present worse performance than their counterparts in Guizhou Province. These results help to encourage China's policy makers to be conservative and proceed with caution regarding SHP development in the fragile Tibetan ecosystem, although SHP has played and will continue to play an essential role in rural electrification in this unique region
Small hydropower development in Tibet: Insights from a survey in Nagqu Prefecture
No full textDue to its large hydraulic power potential, Tibet has been proposed as the main hydropower development base in China after 2020. This is likely to result in the construction of large and medium sized hydropower projects in this region. To date, small hydropower (SHP) has played an essential role in rural electrification in Tibet. Here we present a review of the status of SHP plants in Tibet and explore its potential based on a field survey conducted in the summer of 2014 in Nagqu Prefecture. The survey revealed that SHP in Nagqu has made it possible for approximately 80,000 local residents (16.3% of the total population) to have access to electricity. Our study shows that SHP suffers from problems such as low utilization of the installed power capacity, high scrap ratio and has severe impacts on the local ecosystem. Moreover, the role of SHP in Tibet's rural electrification is gradually changing with the arrival of the main power grid, which has also impacted existing SHP plants. In order to improve SHP overall sustainability, optimization of existing plants and construction of new plants with highers tandards are deemed necessary. This has to be done with due consideration to the fragile ecosystem in Tibet. Therefore, any expansion in the development of SHP in Tibet should have an appropriate strategy for sustainability and ecosystems conservation and protection
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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