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151.
Characteristics of meteorological drought in Bangladesh 总被引:3,自引:3,他引:0
Meteorological drought events occur in Bangladesh are diagnosed using monthly rainfall and mean air temperature from the surface observations and Regional Climate Model (RegCM) by calculating Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI) for the period 1961?C1990. The historical records of drought event obtained from the Bangladesh Bureau of Statistics and International Disaster Database are used to verify the SPI and PDSI detected events. The SPI and monthly PDSI are obtained for 27 station data across Bangladesh as well as for two subregions over the country. Result based on the observed data shows that regional information is better in drought diagnosis compared to the point information. The regional analysis is able to detect about 80?% of the drought events occurred during the study period. Frequency of moderate drought is higher for all over the country. The SPI calculated from RegCM rainfall shows that the detection of moderate drought events is 10, 7, and 21?% overestimated for 1-, 3-, and 6-month length, respectively, compared to using of observed data. For extreme drought cases, detection is overestimated (underestimated) by 25?% (79?%) for 1-month (6-month) length. The PDSI results for model and observed data are nearly same to SPI calculations. Model monthly PDSI result is overestimated (underestimated) by 29?% (50?%) for moderate (severe) drought events with reference to the observed PDSI. Hence, RegCM output may be useful to detect 3?C6-month (monthly to seasonal) length moderate drought events over a heavy rainfall region likely Bangladesh. 相似文献
152.
Nitrogen and phosphorus budget in coastal and marine cage aquaculture and impacts of effluent loading on ecosystem: review and analysis towards model development 总被引:14,自引:0,他引:14
Islam MS 《Marine pollution bulletin》2005,50(1):48-61
Being an essentially open system, cages are usually characterized by a high degree of interaction with environment and cage systems are highly likely to produce large bulk of wastes that are released directly into the environment. Therefore, large-scale cage aquaculture development has been put into question and concerns have been raised that cage aquaculture produces large bulk of wastes that are rich in organic matter and nutrients and are released into coastal and nearshore environment. Recent information on cage aquaculture nutrient budget is scarce and most published reports are dated. This paper reviews cage aquaculture nutrient budget and nutrient loadings and propose a model for nutrient (nitrogen, N and phosphorus, P) budget in a hypothetical cage aquaculture farm with values of feed loss, FCR (feed conversion ratio) and nutrient contents in feed and fish taken from published literature in order to calculate the amount (kg) of N and P produced and released to the environment for each ton of fish produced. The paper proposes, in addition, a critically analyzed nutrient budget based on the dry matter conversion rate instead of the usual feed conversion rate. The conceptual model shows that 132.5 kg N and 25.0 kg P are released to the environment for each ton of fish produced; these values are as high as 462.5 kg N and 80.0 kg P when calculated on the basis of dry matter conversion rate instead of usual feed conversion rate. Thus, the annual global N and P loadings from cage aquaculture (10,000 tons fish and 3000 tons dry matter) are 1325 tons N and 250 tons P and 1387.5 tons N and 240.0 tons P based on usual feed conversion rate and dry matter conversion rate respectively. The paper also proposes, by analyzing the existing data, an FCR-based regression model for predicting nutrient loadings for a given diet. Finally, attempt was made to calculate the annual global loading and release of N and P from cage aquaculture to the coastal and marine environment, the potential impacts of nutrient loading on the ecosystem were discussed and critical points to be considered for minimizing nutrient output in cage aquaculture were suggested. 相似文献
153.
In this paper the authors have extended Bayin's (1978) work to the case of charged fluid spheres. These solutions are matched at the boundary with the Reissner-Nordström solution. 相似文献
154.
On average, only 30-40% of the global fishery production is consumed fresh and the rest 60-70% is processed for human consumption and other purposes. Although the proportion of the total fishery production that are processed remained relatively stable over the last decade, the total bulk of processed fishery commodity increased due to the steady increase in the total fishery production. Processing of large bulk of fish, shrimp and other aquatic organisms produces a corresponding large bulk of by-products and wastes. Although recent trend shows that much of these wastes are made into various value added products, considerable quantities are discharged as the processing effluents with large volume of waters used in processing. Reports suggest that fish and shrimp processing effluents are very high in biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), fat-oil-grease (FOG), pathogenic and other microflora, organic matters and nutrients, etc. Fish and shrimp processing effluents are, therefore, highly likely to produce adverse effects on the receiving coastal and marine environments. Although substantial reduction of the waste loads is possible by applying available simple techniques, this is not in practice in most part of the world due to lack of proper managerial and regulatory approach. The present paper reviews the characteristics of fish and shrimp processing effluents as a potential source of coastal and marine pollution and, using the existing data, analyzes the global production and discharge of waste loads from the processing plants and discusses available options for waste treatment and management. 相似文献
155.
Das Gupta represented theH-functions of transport problems for the albedo [0, 1] in the formH(z)=R(z)–S(z) (see Das Gupta, 1977) whereR(z) is a rational function ofz andS(z) is regular on [–1, 0]
c
. In this paper we have representedS(z) through a Fredholm integral equation of the second kind with a symmetric real kernelL(y, z) as
. The problem is then solved as an eigenvalue problem. The kernel is converted into a degenerate kernel through finite Taylor's expansion and the integral equation forS(z) takes the form:
(which is solved by the usual procedure) where
r
's are the discrete eigenvalues andF
r
's the corresponding eigenfunctions of the real symmetric kernelL(y, z). 相似文献
156.
Mohammad Mahfuzul Islam M. Reaz H. Khondoker Chowdhury Mofizur Rahman 《Ocean Engineering》2001,28(12)
The paper describes a methodology for automatic hull form generation of ships with some desired performances using artificial intelligence techniques. The whole implementation process is divided into three main components. First of all the half-breadth weight matrices are generated that would provide population with pre-fitness by examining the relationship of the hull form with the principal dimensions of a number of existing vessels. Secondly, breadth and draft are adjusted using Neural Network Concepts. Breadth, draft, length, displacement and speed of the ship are very related terms and relations among them create some constraints. Neural Networks solve these constraints and adjust the parameters. Finally, Genetic Algorithm is used for searching the exact solution by examining several generations. For this, the algorithms need to measure fitness for every population in every generation. Unfortunately, GA doesn't guarantee fairness of the surface of the hull form, which can't be ignored. So, for every population especially for newborn population fairing techniques would be used. However, being complex geometric shape, hull form surface can't be faired using least-square or other single equation fitting techniques. Fairness is done taking pair-wise points using B-spline functions [CAD 20(1988)]. 相似文献
157.
158.
Islam Nazrul 《GeoJournal》1980,1(1):7-32
Summary The technically recoverable hydrocarbon reserves of the North Sea are currently estimated at 23 × 109 bbls of oil, condensate and NGL and 90 × 1012 scf of gas.The North Sea underwent a complex geological evolution. The oil and gas occurrences in the central and northern North Sea are tied to Mesozoic and Tertiary sediments; the gas fields of the southern North Sea are mainly contained in Permian series.The proven hydrocarbon provinces cover at best one third of the total area of the North Sea.It is estimated that in the early 1980's the oil production from the North Sea will meet 22% of the oil demand of Western Europe.
Abbreviations scf standard cubic feet (atmospheric conditions at 15° C) - TCF 1012 scf - bbls barrels - NGL Natural Gas Liquids 相似文献
Zusammenfassung Die technisch ausbeutbaren Kohlenwasserstoffreserven der Nordsee werden gegenwärtig auf 23 × 109 bbls Öl, Kondensat und NGL 90 × 1012 scf Gas geschätzt.Das Nordseegebiet durchlief eine komplexe geologische Entwicklungsgeschichte. Die Öl- und Gasfelder der zentralen und nördlichen Nordsee sind hauptsächlich and mesozoische und tertiäre Sedimente gebunden. Die Gasfelder der südlichen Nordsee sind hauptsächlich in permischen Serien enthalten.Die nachgewiesenen Kohlenwasserstoffprovinzen bedecken höchstens ein Drittel der Gesamtoberfläche der Nordsee.Es wird angenommen, da die Ölproduktion der Nordsee während der ersten Hälfte der 1980er Jahre 22 % des Ölbedarfs von West-Europa decken wird.
Résumé Les réserves exploitables de la mer du Nord sont actuellement estimées 23 × 109 bbl de pétrole, condensat et NGL et 90 × 1012 scf de gaz.L'évolution géologique du bassin de la mer du Nord est très complèxe. Les champs de pétrole et de gaz des parties centrales et septentrionales de la mer du Nord se trouvent surtout dans des séries mésozoiques et tertiaires, tandis que la majorité des champs de gaz des régions méridionales sont situés dans des réservoirs permiens.Les provincespetrolfières connues couvrent moins d'un tiers de la surface totale de la mer du Nord.La production de pétrole de la mer du Nord est estimée correspondre pour les premirès années de 1980 à 22 % de la demande en pétrole de l'Europe occidentale.
Abbreviations scf standard cubic feet (atmospheric conditions at 15° C) - TCF 1012 scf - bbls barrels - NGL Natural Gas Liquids 相似文献
159.
160.
S. M. Talha Qadri M.R. Shalaby Md. Aminul Islam Lim Lee Hoon 《Arabian Journal of Geosciences》2016,9(10):559
The Middle to Late Eocene Mangahewa Formation of Taranaki Basin, New Zealand, has been evaluated in terms of organic matter abundance, type, thermal maturity, burial history, and hydrocarbon generation potential. Mangahewa Formation reflects the deposition of marine, marginal marine, shallow marine, and terrestrial strata due to alternative transgressive and regressive episodes in Taranaki Basin. The sediments of the Mangahewa Formation contain type II (oil prone), types II–III (oil-gas prone), and type III kerogens (gas prone), with hydrogen index values ranging from 58 to 490 mg HC/g total organic content (TOC). Vitrinite reflectance data ranging between 0.55 and 0.8 %Ro shows that the Mangahewa Formation is ranging from immature to mostly mature stages for hydrocarbon generation. Burial history and hydrocarbon generation modeling have been applied for two wells in the study area. The models have been interpreted that Mangahewa Formation generated oil in the Mid Miocene and gas during Middle to Late Miocene times. Interpretations of the burial models confirm that hydrocarbons of Mangahewa Formation have not yet attained peak generation and are still being expelled from the source rock to present. 相似文献