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91.
Mohsin Muhammad Mu Yongtong Memon Aamir Mahmood Kalhoro Muhammad Talib Shah Syed Baber Hussain 《中国海洋湖沼学报》2017,35(4):936-946
Pakistani marine waters are under an open access regime.Due to poor management and policy implications,blind fishing is continued which may result in ecological as well as economic losses.Thus,it is of utmost importance to estimate fishery resources before harvesting.In this study,catch and effort data,1996-2009,of Kiddi shrimp Parapenaeopsis stylifera fishery from Pakistani marine waters was analyzed by using specialized fishery software in order to know fishery stock status of this commercially important shrimp.Maximum,minimum and average capture production of P.stylifera was observed as 15 912 metric tons(mt)(1997),9 438 mt(2009) and 11 667 mt/a.Two stock assessment tools viz.CEDA(catch and effort data analysis) and ASPIC(a stock production model incorporating covariates) were used to compute MSY(maximum sustainable yield) of this organism.In CEDA,three surplus production models,Fox,Schaefer and Pella-Tomlinson,along with three error assumptions,log,log normal and gamma,were used.For initial proportion(IP) 0.8,the Fox model computed MSY as 6 858 mt(CV=0.204,R~2=0.709) and 7 384 mt(CV=0.149,R~2=0.72) for log and log normal error assumption respectively.Here,gamma error produced minimization failure.Estimated MSY by using Schaefer and Pella-Tomlinson models remained the same for log,log normal and gamma error assumptions i.e.7 083 mt,8 209 mt and 7 242 mt correspondingly.The Schafer results showed highest goodness of fit R~2(0.712) values.ASPIC computed MSY,CV,R~2,F_(MSY)and B_(MSY) parameters for the Fox model as 7 219 mt,0.142,0.872,0.111 and 65 280,while for the Logistic model the computed values remained 7 720 mt,0.148,0.868,0.107 and 72 110 correspondingly.Results obtained have shown that P.stylifera has been overexploited.Immediate steps are needed to conserve this fishery resource for the future and research on other species of commercial importance is urgently needed. 相似文献
92.
Phuong Thao Thi Ngo Mahdi Panahi Khabat Khosravi Omid Ghorbanzadeh Narges Kariminejad Artemi Cerda Saro Lee 《地学前缘(英文版)》2021,12(2):505-519
The identification of landslide-prone areas is an essential step in landslide hazard assessment and mitigation of landslide-related losses.In this study,we applied two novel deep learning algorithms,the recurrent neural network(RNN)and convolutional neural network(CNN),for national-scale landslide susceptibility mapping of Iran.We prepared a dataset comprising 4069 historical landslide locations and 11 conditioning factors(altitude,slope degree,profile curvature,distance to river,aspect,plan curvature,distance to road,distance to fault,rainfall,geology and land-sue)to construct a geospatial database and divided the data into the training and the testing dataset.We then developed RNN and CNN algorithms to generate landslide susceptibility maps of Iran using the training dataset.We calculated the receiver operating characteristic(ROC)curve and used the area under the curve(AUC)for the quantitative evaluation of the landslide susceptibility maps using the testing dataset.Better performance in both the training and testing phases was provided by the RNN algorithm(AUC=0.88)than by the CNN algorithm(AUC=0.85).Finally,we calculated areas of susceptibility for each province and found that 6%and 14%of the land area of Iran is very highly and highly susceptible to future landslide events,respectively,with the highest susceptibility in Chaharmahal and Bakhtiari Province(33.8%).About 31%of cities of Iran are located in areas with high and very high landslide susceptibility.The results of the present study will be useful for the development of landslide hazard mitigation strategies. 相似文献
93.
Precise Seismic Substructural Model of the Eocene Chorgali Limestone in the Turkwal Oil Field, Central Potwar, Pakistan
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Khawar Ashfaq AHMED Sarfraz KHAN Mahmood SULTAN UMAIR Bin Nisar Kalim ULLAH Al -Hseinat MU’AYYAD 《《地质学报》英文版》2019,93(6):1711-1720
The precise seismic substructural interpretation of the Turkwal oil field in the Central Potwar region of district Chakwal of Pakistan has been carried out. The research work was confined to the large fore-thrust that serves as an anticlinal structural trap through ten 2D seismic lines. A precise seismic substructural model of the Eocene Chorgali Limestone with precise orientation of thrust and oblique slip faults shows the presence of a huge fracture, which made this deposit a good reservoir. The abrupt surface changes in dip azimuth for the Eocene Chorgali Limestone verifies the structural trends and also the presence of structural traps in the Turkwal field. The logs of three wells (Turkwal deep X-2, Turkwal-01 and Fimkassar-01) were analyzed for petrophysical studies, well synthetic results and generation of an Amplitude Versus Offset (AVO) model for the area. The AVO model of Turkwal deep X-2 shows abrupt changes in amplitude, which depicts the presence of hydrocarbon content. Well correlation technique was used to define the overall stratigraphic setting and the thickness of the reservoir formation in two wells, Turkwal-01 and Turkwal deep X-2. The Eocene Chorgali Limestone in Turkwal-01 is an upward thrusted anticlinal structure and because of the close position of both wells to the faulted anticlinal structure, its lesser thickness differs compared to Turkwal deep X-2. The overall results confirm that the Turkwal field is comparable to several similar thrust-bound oil-bearing structures in the Potwar basin. 相似文献
94.
Desertification process as a great problem affects most of the countries in the world.This process has a high rate in arid and semiarid areas.Today,human societies are encountering the desertification phenomenon as a serious problem which causes various irreparable damages to economic and social sectors.In order to assess desertification results in production of different regional models for their application in another region the indices should be re-investigated and adjusted to local conditions.Several models have been developed for desertification evaluation.The present study,attempts to assess quantitatively the desertification process has in an area located at Sistan plain of Iran(Niatak region as a case study) by using Modified MEDALUS method.The obtained results indicated that of the whole studied region(comprising 4819.6 acres),2651.56 acres(55%) are located in medium desertification intensity class,1269.48 acres(26.34%) are positioned in severe desertification intensity class,and 898.54 acres(18.64%) are placed in vary severe desertification intensity class. 相似文献
95.
Mahmood A. Ismail 《Astrophysics and Space Science》1986,122(1):1-32
The paper discusses an investigation of linear polarization produced by the transmission of light through an astronomical spectrograph slit. An experimental apparatus was designed and set up to carry out this work. The parallel beam of plane polarized light was rotated in the measuring system, by optically active of half-wave plate. The intensity of normally incident of polarized light of wavelength 0.436 μm transmitted by various slit was measured as a function of slit width. The results indicate:
- That the degree of polarization increased as thedepth of the narrow slit was increased.
- That the degree of polarization increased as thewidth of the narrow slit was decreased.
- That when the width of slit was widened the degree of polarization tended to approach a constant value asymptotically.
- That the theoretical calculation of Slater (1942) predicts the measured experimental values more accurately than Thiessen (1947) and Jones and Richards (1954).
96.
97.
Paula Lindgren Martin R. Lee Mahmood R. Sofe Michael E. Zolensky 《Meteoritics & planetary science》2013,48(6):1074-1090
Clasts in the CM2 carbonaceous chondrite Lonewolf Nunataks (LON) 94101 have been characterized using scanning and transmission electron microscopy and electron microprobe analysis to determine their degrees of aqueous alteration, and the timing of alteration relative to incorporation of clasts into the host. The provenance of the clasts, and the mechanism by which they were incorporated and mixed with their host material are also considered. Results show that at least five distinct types of clasts occur in LON 94101, of which four have been aqueously altered to various degrees and one is largely anhydrous. The fact that they have had different alteration histories implies that the main part of aqueous activity occurred prior to the mixing and assimilation of the clasts with their host. Further, the presence of such a variety of clasts suggests complex mixing in a dynamic environment involving material from various sources. Two of the clasts, one containing approximately 46 vol% carbonate and the other featuring crystals of pyrrhotite up to approximately 1 mm in size, are examples of unusual lithologies and indicate concentration of chemical elements in discrete areas of the parent body(ies), possibly by flow of aqueous solutions. 相似文献
98.
Nonlinear cylindrical and spherical ion acoustic shocks have been studied in unmagnetized dissipative non-Maxwellian electron-positron-ion (e-p-i) plasmas. Modified Korteweg-de Vries Burgers (mKdVB) has been derived by using reductive perturbation method. Two level finite difference scheme is used with the help of Runge Kutta method to simulate the mKdVB. It is noticed that positron concentration, spectral indices of electrons and positrons, kinematic viscosity of ions significantly modifies the strength of shocks in cylindrical and spherical geometries. 相似文献
99.
The positron acoustic shock and solitary wave are explored in nonextensive electron-positron-ion plasma. The plasma system under-consideration, consists of a classical positron beam, q distributed electrons and positively charged bulky ions constitute a neutralizing background. The nonlinear Korteweg-de Vries and Burger equations are derived by employing the standard reductive perturbation method. The positron acoustic wave in linear limit is also discussed for dissipative as well as nondissipative cases of nonextensive plasmas. The plasma parameters such as, the concentration of neutralizing ions background, beam velocity, temperature and q parameter of the nonextensive electrons are noticed to significantly affect the positron acoustic shock and solitary waves. Our findings may be helpful in the understanding of laboratory beam plasma interaction experiments as well as the astrophysical nonextensive plasmas interacting with positron beam. 相似文献
100.
S. Mahmood A. Hussain Z. Saeed M. Athar 《International Journal of Environmental Science and Technology》2005,2(3):269-274
The heavy metal tolerance in corn (Zea mays L.) var. ‘Neelum’ was assessed at germination and seedling growth after having subjected it to different concentrations of CuSO4 and ZnSO4. Germination was not affected by any of the metal tested, whereas initial growth was strongly inhibited by increasing concentrations of ZnSO4. Seedlings developed toxicity symptoms in the presence of both metals but more chlorotic and necrotic regions were observed at varying levels of ZnSO4 than CuSO4. The metal accumulation was concentration dependent. Z. mays seedlings accumulated more copper in roots but greater contents of zinc in their shoots. On the basis of results presented here, it can be concluded that the cultivar of the species tested has shown a marked sensitivity to the presence of small amounts of metals present in the growth medium. The data support the assumption that metal sensitivity is probably due to strong tendency of the species to accumulate them. This justifies that the corn variety ‘Neelum’ is not suitable for the cultivation under situations where water and soil suffer from occasional and/ or transitory metal pollution. 相似文献