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Tim Wylie Michael A. Schuh Rafal A. Angryk 《Journal of Combinatorial Optimization》2016,32(4):1107-1132
Many modern search applications are high-dimensional and depend on efficient orthogonal range queries. These applications span web-based and scientific needs as well as uses for data mining. Although k-nearest neighbor queries are becoming increasingly common due to mobile and geospatial applications, orthogonal range queries in high-dimensional data remain extremely important and relevant. For efficient querying, data is typically stored in an index optimized for either kNN or range queries. This can be problematic when data is optimized for kNN retrieval and a user needs a range query or vice versa. Here, we address the issue of using a kNN-based index for range queries, as well as outline the general computational geometry problem of adapting these systems to range queries. We refer to these methods as space-based decompositions and provide a straightforward heuristic for this problem. Using iDistance as our applied kNN indexing technique, we also develop an optimal (data-based) algorithm designed specifically for its indexing scheme. We compare this method to the suggested naïve approach using real world datasets. The data-based algorithm consistently performs better. 相似文献
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This article presents an historical review of the organization known as Student Health Services at Academic Medical Centers (SHSAAMc). The authors discuss characteristics of health service directors as well as the history of meetings, discussion, and leadership. The focus of the group is the healthcare needs of health professions students at academic medical centers. 相似文献
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Recent decades have witnessed the rise, across a wide range of countries, of political institutions designed to promote gender equality and women’s political representation. Existing studies have shown how international diffusion processes have contributed to the adoption of two kinds of such institutions – gender mainstreaming and gender quotas. Mounting evidence suggests that institutional reforms within legislatures constitute the latest wave of gendered institutional reform. This article identifies and explains trends in the adoption of one kind of gender-focused parliamentary institution – women’s legislative caucuses (WLCs). We use a discrete time duration model to assess the effect of several factors on WLC establishment. While there is theoretical room to expect diffusion, structural and institutional variables to affect the likelihood of caucus adoption, we find the strongest empirical support for diffusion and institutional factors. A parliament’s likelihood of adopting a WLC rises when sub-regional peers have created WLCs, when women’s international non-governmental organizations are active in the country and when the country has implemented a gender quota. Understanding the factors that affect the adoption of gender-focused parliamentary institutions is critically important, we argue, since such bodies provide space to confront masculinized institutionalized rules and norms. 相似文献
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Soil-atmosphere exchange of carbon dioxide,methane and nitrous oxide in urban garden systems: impact of irrigation,fertiliser and mulch 总被引:1,自引:1,他引:0
Stephen J. Livesley Ben J. Dougherty Alison J. Smith Damian Navaud Luke J. Wylie Stefan K. Arndt 《Urban Ecosystems》2010,13(3):273-293
Urban green spaces provide important ecosystem services, such as amenity, biodiversity, productivity, climate amelioration,
hydrological and biogeochemical cycling. Intensively managed urban gardens can sequester carbon through vegetation growth
and soil C increase, but may experience nitrous oxide (N2O) emissions and reduced soil methane (CH4) uptake from irrigation and fertiliser use. Soil atmosphere exchange of N2O, CH4 and carbon dioxide (CO2) was measured in lawn and wood chip mulched garden areas in Melbourne, Australia in winter, spring and summer under various
water and fertiliser regimes. Gas exchange before and after lawn fertiliser application was measured continuously for three
weeks using an automated chamber system. Applying fertiliser led to a peak N2O emission of >60 μg N m−2 h−1, but overall only weekly irrigation (10 mm) significantly increased mean soil N2O emissions above that in other treatments. Under mulch, mean soil N2O emissions (14.0 μg N m−2 h−1) were significantly smaller than from irrigated lawn (27.9 μg N m−2 h−1), whereas mean soil CH4 uptake under mulch (−30.7 μg C m−2 h−1) was significantly greater (p < 0.01) than in any lawn treatment. Lawns were either a weak CH4 sink or source. Soil C density (0–25 cm) under mulch (12.5 kg C m−2) was greater that under lawn (8.0 kg C m−2). On a carbon dioxide equivalent (CO2-e) basis, soil N2O emissions offset the benefits of soil CH4 uptake. Mulched garden areas provide greatest C sequestration potential in soil and vegetation and the smallest non-CO2 emissions, as soil CH4 uptake offsets a large fraction of soil N2O emissions. Results of this study suggest that reducing the irrigation and fertiliser application to lawns can help mitigate
GHG emissions from urban garden systems, and increasing the area of mulched perennial garden beds can also provide net GHG
benefits; however, this needs to be tested in other garden systems with different soil types and environmental conditions. 相似文献
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