An analytic solution for propagation of blast waves in stellar interiors     

O. S. Srivastava  A. H. Khan  D. Singh 《Astrophysics and Space Science》1987,137(1):63-72

B, V observations of the eclipsing binary RS CVn have been presented. A dip around 0 ^p . I appears to be a wave minimum which fits well in the Wave minimum phase-time relation, but deviates from the Wave aplitude-time relation, derived for the RS CVn. Either, the Wave amplitude-time relation requires a modification or the amplitude of the wave minmum appears masked by the intrinsic variability of one of the components or by the Sun-spot activity of the system. The colour exhibits variation. The secondary component appears active.  相似文献   

Evaluation of extreme dust storm over the northwest Indo-Gangetic plain using WRF-Chem model     

Shukla  K. K.  Attada  Raju  Khan  Aman W.  Kumar  Prashant 《Natural Hazards》2022,110(3):1887-1910

Natural Hazards - This study uses a high-resolution Weather Research and Forecasting model coupled with the chemistry module (WRF-Chem) to analyze the dust storm that occurred during 12?17...  相似文献   

Poverty and environmental nexus in rural Pakistan: a multidimensional approach     

Khan  Irum  Saqib  Muhammad  Hafidi  Houda 《GeoJournal》2021,86(2):663-677

The study examines the relationship between poverty and forest cover degradation in rural areas of Pakistan. The area selected for the study District Upper Dir is a rural and relatively backward region located in northwestern Pakistan, in Khyber-Pakhtunkhwa province. The study area is undergoing severe deforestation and natural disasters in the recent past. The study consists of two stages, in first stage the traditional Geographical information system image was used to analyze the spatial–temporal situation of the surroundings. In the second stage, well-designed questionnaire was used to collect the primary information from 420 randomly selected households of research areas. A multidimensional poverty index has been used to measure the poverty profile of the population. It has been found that 55% households were below the poverty line. Almost, 95% households are using wood for cooking purposes. High dependence on natural resources causes forest cover degradation while burning off too much wood causes CO₂ emission and leads to environmental degradation. A major portion of population is living on steeply sloped areas with certain risks. It is found that frequency of flash flood is 53% and agricultural land (54%) is at high risk and often flows with flash floods. It is concluded that there is strong correlation between multidimensional poverty and forest cover degradation which leads to climate and environmental risks.

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Multidimensional six-stage model for flood emergency response in schools: a case study of Pakistan     

Shah  Ashfaq Ahmad  Wu  Wenya  Gong  Zaiwu  Pal  Indrajit  Khan  Jahangir 《Natural Hazards》2021,105(2):1977-2005

Natural Hazards - Children spend more than two-thirds of their total daytime in schools and becoming more persuasive in shielding them from potential hazards. Schools have a responsibility to...  相似文献   

Composition,Structure and Regeneration Dynamics of Olea ferruginea Royle Forests from Hindukush Range of Pakistan     

NASRULLAH Khan  FAYAZ Ali  KISHWAR Ali  SHAHID Shaukat 《山地科学学报》2015,(3):647-658

The abundance of Olea ferruginea in Malakand Division has been significantly reduced across its distribution range due to anthropogenic pressure in the recent past. A number of initiatives were taken for grafting this species to obtain better seeds for oil production, without the basic information on their ecology and management. To address this knowledge gap, we quantified the composition, structure and regeneration dynamics of Olea ferruginea forests in Malakand Division, Hindukush range of Pakistan. In the present study, five communities dominated by Olea ferruginea were identified using Ward's agglomerative cluster analysis.Total tree density ranged from 153-2602 plants/ha, and basal area from 19.55 to 2353 m2 ha-1 with Olea having a relative density of 51% to 87% and basal area of 48% to 93%, respectively. The density of juveniles of the dominant and subordinate tree species were generally low which reflect their narrow distribution in the study area. Size-class distributions of O. ferruginea disclosed a bell-shaped pattern, indicating that forests were heavily exploited by local inhabitants in previous periods and recently by armed forces owing to security risks in the study area. The age(mean max. 300±34 years) and annual increment(3.2±1.2 years/cm) indicates that the species is long lived and generally slow growing among the different broad leaved species studied so far. However, the oldest trees can be found by the exploration of large diameter trees in the area. In addition, we found a stable linear relationship between the age and diameter(r2 = 0.779), indicating that diameter is a good predictor of age for this broad leaved species. In view of its relatively slow growth, longevity and positive ring-width characteristics O. ferruginea seems to be a suitable choice for dendroecological and dendrochronological studies in lesser Himalayan and Hindukush ranges of Pakistan. The results obtained from this study may help in understanding the composition, structure and regeneration dynamics of other subtropical broad leaved species.  相似文献   

Energy contents of some non-vacuum spacetimes in teleparallel gravity     

M. Sharif  Sumaira Taj 《Astrophysics and Space Science》2010,325(1):75-83

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Short-Term Periodicities in Sunspot Activities During the Descending Phase of Solar Cycle 23     

Partha Chowdhury  Manoranjan Khan  P. C. Ray 《Solar physics》2010,261(1):173-191

In the present study, the short-term periodicities in the daily data of the sunspot numbers and areas are investigated separately for the full disk, northern, and southern hemispheres during Solar Cycle 23 for a time interval from 1 January 2003 to 30 November 2007 corresponding to the descending and minimum phase of the cycle. The wavelet power spectrum technique exhibited a number of quasi-periodic oscillations in all the datasets. In the high frequency range, we find a prominent period of 22 – 35 days in both sunspot indicators. Other quasi-periods in the range of 40 – 60, 70 – 90, 110 – 130, 140 – 160, and 220 – 240 days are detected in the sunspot number time series in different hemispheres at different time intervals. In the sunspot area data, quasi-periods in the range of 50 – 80, 90 – 110, 115 – 130, 140 – 155, 160 – 190, and about 230 days were noted in different hemispheres within the time period of analysis. The present investigation shows that the well-known “Rieger periodicity” of 150 – 160 days reappears during the descending phase of Solar Cycle 23, but this is prominent mainly in the southern part of the Sun. Possible explanations of these observed periodicities are delivered on the basis of earlier results detected in photospheric magnetic field time series (Knaack, Stenflo, and Berdyugina in Astron. Astrophys. 438, 1067, 2005) and solar r-mode oscillations.  相似文献   

Lead isotope signatures of Pb-Zn sulfide mineralization in the Reshian-Lamnian area of Azad Jammu and Kashmir,Pakistan     

Mohammad Tahir Shah  Tazeem Khan  Ahmad Khan 《中国地球化学学报》2010,29(1):65-74

The Reshian-Lamnian area within the Hazara-Kashmir syntaxis in Pakistan is composed mainly of the rocks of the Salkhala, Panjal and Murree formations. Base metal sulfide mineralization in the form of sphalerite and galena with lesser amounts of chalcopyrite and pyrite is present within the Salkhala Formation of the study area. Chemically all these ore phases are homogeneous in composition. The Pb isotopic composition of galena from the area suggests that there is very little or negligible variation in the ratios of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb. Modal ages ranging from 509 to 562 Ma and the μ values of 10.71 to 10.93 have been calculated for the studied Pb-Zn mineralization. On the basis of field features, mineralogy and Pb-isotope signatures, it is concluded that the Pb-Zn sulfide mineralization in the Reshian-Lamnia area is pre-Himalayan in age and can be correlated with the Cambro-Ordovician (Pan-African) orogenic event.  相似文献   

Trace element geochemistry of groundwater from Quetta Valley,western Pakistan   总被引：1，自引：0，他引：1  

Shuhab D. Khan  Khalid Mahmood  Mohamed I. Sultan  Abdul S. Khan  Yingqian Xiong  Zhanay Sagintayev 《Environmental Earth Sciences》2010,60(3):573-582

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Hydrological processes of adsorption,sedimentation, and infiltration into the lake bed during the 2004 urban flood in Dhaka city,Bangladesh   总被引：1，自引：1，他引：0  

Kenji Okubo  M. Shah Alam Khan  M. Qumrul Hassan 《Environmental Earth Sciences》2010,60(1):95-106

The urban flood of Dhaka city in September 2004 is a result of heavy rainfall (341 mm a day or more than 600 mm in 5 days). In addition to the local rainfall, elevated water levels in the surrounding rivers may have affected the flood duration by bank filtration. Two lakes, Banani and Gulshan, in the mid of the city are the part of general storm water retention system in Dhaka. Flood water runs through the lakes acting as channels to the pumping station downstream. A tank model is used in this study to describe the total drainage process with the hydraulic geometry and resistance laws to derive cross-sections and friction factors of the quasi-uniform flows. Assuming the dissolved matters of the flood water was of similar composition as in the lake sediments, the process was a combination of adsorption and sedimentation. Lake sediment samples collected in March 2004 show an anomaly of chromium which may reflect the previous 1998 flood, and there may be a diffusive leakage from the source area to the adjacent zones. Further evidence of infiltration process is seen in records of diurnal thermal stratification of Lake Banani. It responds to only heavy rainfalls over 100 mm/day, and the fact means that infiltration to the groundwater is rather intermittent.  相似文献