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41.
Commercial aquaculture in India has come under attack for having caused negative agricultural and environmental impacts. This paper formulates an interactive model of non-renewable and renewable resources to characterize land allocations between aquaculture and agriculture in ecologically and economically sustainable fashion. Through an empirical application, various economic and policy circumstances that affect the optimal land allocation mix are evaluated. The aquaculture industry must address two economic effects: off-site negative effects on renewable food and other coastal resources, and on-site self-pollution of shrimp ponds. Current regulatory and land-use policies are inadequate to address these effects. 相似文献
42.
Jennifer G. Winter M. Catherine Eimers Peter J. Dillon Lem D. Scott Wolfgang A. Scheider Campbell C. Willox 《Journal of Great Lakes research》2007,33(2):381-396
Total phosphorus (TP) inputs to Lake Simcoe have led to hypolimnetic dissolved oxygen (DO) depletion and loss of cold water fish habitat. Since 1990, efforts have been made to reduce the total TP input to the lake below a defined target of 75 t/year, which was predicted to lead to reductions in spring TP concentration and improvements in end-of-summer hypolimnetic DO concentrations. The total TP load to the lake during the most recent period of record (1998/99-2003/04) ranged from 53 to 76 t/yr and averaged 67 t/yr, compared to an average of 114 t/yr estimated between 1990/91 and 1997/98 (range 85-157 t/yr). Reductions in TP loads from the catchment via tributary discharge (∼26 t) accounted for the majority of the decrease in total load between the two time periods. Total P concentrations decreased significantly in four out of six long-term monitored tributaries; however, concentrations in all six tributaries remain above the level recommended to avoid nuisance plant growth (30 μg/L). Although TP loads to the lake are currently below the target 75 t/yr, excessive growths of filamentous algae and macrophytes continue to be a problem in the nearshore zone. End-of-summer minimum hypolimnetic DO concentrations (average 4.3 mg/L, 1998/99-2003/04) remain substantially below the level (7 mg/L) that is considered protective of lake trout. Efforts to reduce TP loads to the lake therefore need to continue. 相似文献
43.
Yu. V. Balaban-Irmenin N. G. Fokina 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(5):306-312
The effect of internal-corrosion inhibitors on heating-system pipelines is investigated. Tests were conducted on a testing
device for polarization measurements under conditions corresponding to the Rostov Heat-Supply System. The concentration of
OEDP-zinc, which provides a high degree of protection from general corrosion, is determined. The reagent has been successfully
incorporated into the Rostov No. 2 TPP.
__________
Translated from élektricheskie Stantsii, No. 7, July 2007, pp. 37–43. 相似文献
44.
Aboubakar Sako Kenneth G. MacLeod Catherine M. O’Reilly 《Journal of Great Lakes research》2007,33(4):806-815
In this study, we measured growth trends in oxygen and carbon isotopic ratios in whole sagittal otoliths from three adult centropomid fish (Lates stappersii) from each of three sub-basins of Lake Tanganyika, East Africa. Sampling density was 20 to 50 samples per otolith. Both δ18O and δ13C values increase with age. The δ18O data suggest that otoliths were precipitated near the expected equilibrium with the ambient environment (ca. +3.5‰) and support a migration pattern from surface waters during larval stages to deeper waters (40 to 80 m) for mature fish. Relatively high δ18O values in the southern sub-basin are consistent with cooler temperatures in the region during seasonal upwelling. The δ13C increase from otolith core to edge is large (up to 4‰) and is interpreted as due to ontogenetic changes in diet and contributions from a decrease in the proportion of respired CO2 incorporated into otolith carbonate as metabolic rates of the fish dropped with maturity. The data seem to successfully reveal life strategy and migration patterns of L. stappersii, document regional differences in lake conditions, and provide a record of temperature within the water column during which the fish lived. Higher resolution studies and analyses of historical samples could be used to constrain modern and past growth patterns, and to reconstruct past temperature gradients and productivity patterns in the lake. 相似文献
45.
Yu. V. Balaban-Irmenin N. G. Fokina 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(4):228-232
The reliability of heat-supply systems is determined primarily by internal corrosion of the pipelines. The concentration of
oxygen in the water exerts a major influence on the corrosion. In systems with a standard oxygen content, OéDF-Zn is a highly
effective corrosion inhibitor. However, there are systems in which the quality of deaeration of the make-up water of the heat-supply
system is low (or deaeration is nonexistent), and the concentration of oxygen is considerably above the standard value. Classed
among these systems, for example, are the HWS systems, which are incorporated into closed heat-supply systems. The oxygen
concentration in these systems is analyzed to assess the situation.
__________
Translated from élektricheskie Stantsii, No. 6, June 2007, pp. 35–39. 相似文献
46.
47.
Scott G. Borgerson 《环球财经》2008,(6):102-102
北极冰川融化将使跨北极通航成为可能,运输公司可减少40%的航运距离。马六甲海峡也将不再垄断国际通运。国际经济将进一步融合。 相似文献
48.
GÁBOR VIRÁG 《Journal of Public Economic Theory》2008,10(5):891-922
This paper considers a two‐party election with a single‐dimensional policy space. We assume that each voter has a higher probability of observing the position of the party he is affiliated with than the position of the other party, an assumption that is consistent with the National Election Studies (NES) electoral data set. In equilibrium, the two parties locate away from the median, because the voters who dislike a party's platform observe its policy choice with a lower probability, and its own audience like policy choices that cater to its taste. As the asymmetry in voter information or the cost of voting increases, the parties adopt more extreme platforms, while if there are fewer extreme voters the opposite effect occurs. Making voters more symmetrically informed about the two parties' platforms increases the welfare of society, while asymmetric information acquisition by the voters is worse than no information acquisition at all. 相似文献
49.
Water retention times less than 3 h from inlet to outlet were necessary to meet new effluent requirements without extending the footprint of the existing plant. Nitrogen removal was required at the existing, high loaded, direct precipitation plant and space was not readily available. The staff at the VEAS WWTP took on the task to design a new process at their own risk. Selected solutions and ups and downs in the water treatment during the past 10 years of operations and further developments are presented in this paper. Always asking for well-proven solutions might make life easy. The intent of this paper is to encourage some of our colleagues to be more daring in their approach to new challenges. However, expect sleepless nights in order to solve the unexpected problems along the way. 相似文献
50.
Two of the main forces driving European emigration in the late nineteenth century were real wage gaps between sending and receiving regions and demographic booms in the low‐wage sending regions. Our new estimates of net migration for the countries of sub‐Saharan Africa show that exactly the same forces driving African across‐border migration are at work today. The results suggest that rapid growth in the cohort of potential young emigrants, population pressure on the resource base, and slow economic growth are likely to intensify the pressure for migration out of Africa and into high‐wage OECD countries over the next two decades. 相似文献