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101.
102.
S. S. Hasan 《Journal of Astrophysics and Astronomy》2000,21(3-4):283-287
We model the dynamical interaction between magnetic flux tubes and granules in the solar photosphere which leads to the excitation
of transverse (kink) and longitudinal (sausage) tube waves. The investigation is motivated by the interpretation of network
oscillations in terms of flux tube waves. The calculations show that for magnetic field strengths typical of the network,
the energy flux in transverse waves is higher than in longitudinal waves by an order of magnitude. But for weaker fields,
such as those that might be found in internetwork regions, the energy fluxes in the two modes are comparable. Using observations
of footpoint motions, the energy flux in transverse waves is calculated and the implications for chromospheric heating are
pointed out. 相似文献
103.
Hasan Özkaynak 《地震工程与工程振动(英文版)》2018,17(2):385-401
The earthquake performance of vulnerable structures can be increased by the implementation of supplementary energy-dissipative metallic elements. The main aim of this paper is to describe the earthquake behavior of steel cushion-implemented reinforced concrete frames (SCI-RCFR) in terms of displacement demands and energy components. Several quasi-static experiments were performed on steel cushions (SC) installed in reinforced concrete (RC) frames. The test results served as the basis of the analytical models of SCs and a bare reinforced concrete frame (B-RCFR). These models were integrated in order to obtain the resulting analytical model of the SCI-RCFR. Nonlinear-time history analyses (NTHA) were performed on the SCI-RCFR under the effects of the selected earthquake data set. According to the NTHA, SC application is an effective technique for increasing the seismic performance of RC structures. The main portion of the earthquake input energy was dissipated through SCs. SCs succeeded in decreasing the plastic energy demand on structural elements by almost 50% at distinct drift levels. 相似文献
104.
Murat Emre Kartal Alemdar Bayraktar Hasan Basri Başağa 《Soil Dynamics and Earthquake Engineering》2010
In this study, failure probability of the concrete slab on concrete-faced rockfill (CFR) dams with welded and friction contact is investigated under earthquake effects by reliability analysis. For this purpose, Torul CFR dam is selected as an example and numerical solutions are performed by considering combination of reliability analysis–finite element method. 1992 Erzincan earthquake acceleration record is used in the finite element analysis considering deconvolved-base rock input model. In this model, the ground motion to be applied to the foundation base rock is obtained by deconvolution of the free-field surface record. In the materially nonlinear analysis, Drucker–Prager model is used for concrete slab and multi-linear kinematic hardening model is utilized for rockfill. Geometrically nonlinearity is also taken into account. Viscous boundary conditions are defined in the finite element model for both foundation soil and reservoir water. The hydrodynamic pressure of the reservoir water is considered using 2D fluid finite elements based on the Lagrangian approach. Both welded contact and friction contact based on the Coulomb’s friction law are defined in the structural connections. Improved Rackwitz–Fiessler method is used with response surface method in the reliability analysis. The tensile and compression strengths of the concrete slab are utilized in the implicit limit state functions considering various thicknesses. The probability of failure of the most critical points in the concrete slab is obtained. According to this study, the probabilities of failure obtained from the CFR dam including friction contact are lower. When the welded contact is considered in joints, the probability of failure of the concrete slab is 1 due to tensile stress limit state and compression stress limit state only if concrete slab is linear. The most critical probability of failure of the concrete slab appears in the case that the concrete slab is linear and rockfill is materially nonlinear. The probability of failure of the concrete slab decreases if the nonlinearity of the concrete is considered. Also, hydrodynamic pressure decreases the reliability of the concrete slab. 相似文献
105.
R. S. Sinha Ashok Kumar C. S. Agarwal N. Hasan 《Journal of the Indian Society of Remote Sensing》1988,16(1):85-94
Ground water prospecting in hard rock areas of Uttar Pradesh is quite difficult, owing to the geological and geomorphic controls of sub-surface strata on the occurrence and movement of ground water resources, and, therefore, it requires systematic investigations, mainly with the aid of remotely sensed and data, which undoubtedly provide realistic information on the hydrogeological conditions, geomorphologic features, drainage patterns etc. of any rocky area. In this paper, an endeavour has been made to locate ground water possibilities in the drought-affected, rocky terrain of the southern Mirzapur district of Uttar Pradesh, covering part of block Muirpur which is mainly characterised by the varied geological formations, including Archean complex, pre-Vindhyan matasediments and Gondwana formation, through the application of air photointerpretation technique, primarily based on the geologic/geomorphologic approach. The hydro-investigation in the area was carried out using panchromatic aerial photos of 1∶60,000 scale, chiefly to identify the drainage patterns, major geomorphic geo structural and lithological units; as these may control the ground water regime of the area, Further. the present study was also ably supported with limited field survey and hydrogeological data, for achieving reliable results. 相似文献
106.
Damage and management of cyclone Sidr-affected homestead tree plantations: a case study from Patuakhali, Bangladesh 总被引:1,自引:0,他引:1
Md. Zamiul Haq Mahbub Robbani Mohammad Ali Md. Mainul Hasan Md. Mahmudul Hasan Md. Jashim Uddin Monjila Begum Jaime A. Teixeira da Silva Xiao-Ying Pan Md. Rezaul Karim 《Natural Hazards》2012,64(2):1305-1322
Geographically, Bangladesh is considered to be one of the most cyclone-prone areas in the world. The super cyclone Sidr in 2007 was one of the most devastating disasters to have ever occurred in Bangladesh, having wind speeds of 223?km/h with a tidal surge of 6.1?C7.6?m high. In order to draw a pre- and post-Sidr damage and management scenario, a survey was conducted at Dumki upazila, Patuakhali district in Bangladesh with a pretested questionnaire. Primary data were collected through a questionnaire, while secondary data were collected from pertinent offices as well as academic journals. The major focus of this study was to assess the state of pre-Sidr tree plantations (woody and fruit trees), the devastation caused by Sidr on these tree plantations, and post-Sidr recovery and further sustainable management initiatives to counteract a possible future neo-Sidr. The post-Sidr study showed that about 16.84 million woody and fruit trees were uprooted by Sidr. A total of 3,120 rain tree (Samanea saman L.), 7,548 mahogany (Swietenia mahagoni L.), 1,444 royal siris (Albizzia richardiana L.), 702 white siris (Albizzia procera L.), 1,214 mango (Mangifera indica L.), 1,092 coconut (Cocos nucifera L.), 1,380 jackfruit (Artocarpus heterophyllus L.), and 7,640 betel nut (Areca catechu L.) trees were sampled among which 922, 1,662, 382, 210, 106, 38, 362, and 1,652 trees, respectively, were markedly damaged by Sidr. Sexually propagated woody trees with a damaged taproot were vulnerable to heavy wind during the cyclone. Fruit trees were more resistant to the cyclone than other types of trees, and the lack of proper tree training and pruning was one of the principal causes of the severe damage to woody trees. Hence, plantations of woody tree saplings with damaged taproots are strongly discouraged. However, proper training and pruning of homestead trees together with plantation of fruit trees rather than woody trees is suggested as a possible effective management strategy to protect the homestead ecosystem from devastation by future cyclones in Bangladesh. 相似文献
107.
Subsidence as a result of an underground coal mine is a hazard to human life, properties and environment. This incidence usually occurs over a long period of time which directly or indirectly pertinent with various factors that needs to be carefully considered and systematically analyzed when exploring land subsidence. In reality the relationships among factors, their effects and the subsidence are crucial to have the suitable management plan for the mine-induced ground subsidence around the mining area. In this research, primarily the development of subsidence caused by the extraction of 1203 slice has been evaluated under the profile functions and influence functions methods. The results show that the calculated subsidence profile is almost trough-like subsidence where the maximum amount of subsidence is about 0.89 m. Secondly, based on this result, the analysis on different factors such as the deeper coal bed (420 m depth level) and higher angle of draw (42.5o) show less subsidence which are 0.58 and 0.87 m, respectively, whereas the dip of the coal bed up to 20o does not have significant effect on subsidence. In latter cases, the different preceding scientific papers have been consulted and analyzed for recognizing various influencing factors of subsidence which replicate that the geology and stratigraphic configuration, structural setting of the coal basin, hydro-geological characteristics, less competent nature of overlying rock body, applied mining method, presence of multi-coal seams, ultra thicken coal seam and so on are the major factors in affecting the subsidence event in the area. Moreover, intensive site investigations revealed similar pattern of subsidence and its associated factors around the mine. 相似文献
108.
Hamid M. K. Al-Naimiy Hasan A. Fleyeh Aasem O. Al-Sikab Jinan M. Al-Razzaz 《Astrophysics and Space Science》1989,151(1):135-147
The eclipsing binary 44i Boo was observed photoelectrically using the 40 cm Cassegrain telescope at the Al-Battani Observatory.The light curves were analysed using Fourier techniques of light changes in the frequency-domain, and new geometrical and physical elements have been obtained.A new active period to be started in 1986 has been observed. 相似文献
109.
Javed Mallick Yasser Alashker Shams Al-Deen Mohammad Mohd Ahmed Mohd Abul Hasan 《国际地球制图》2013,28(8):915-940
Soil erosion is the most important factor in land degradation and influences desertification in semi-arid areas. A comprehensive methodology that integrates revised universal soil loss equation (RUSLE) model and GIS was adopted to determine the soil erosion risk (SER) in semi-arid Aseer region, Saudi Arabia. Geoenvironmental factors viz. rainfall (R), soil erodibility (K), slope (LS), cover management and practice factors were computed to determine their effects on average annual soil loss. The high potential soil erosion, resulting from high denuded slope, devoid of vegetation cover and high intensity rainfall, is located towards the north western part of the study area. The analysis is investigated that the SER over the vegetation cover including dense vegetation, sparse vegetation and bushes increases with the higher altitude and higher slope angle. The erosion maps generated with RUSLE integrated with GIS can serve as effective inputs in deriving strategies for land planning/management in the environmentally sensitive mountainous areas. 相似文献
110.
Koichi Unami Macarius Yangyuoru Abul Hasan Md. Badiul Alam 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(1):115-126
Micro-dams in West African savannas are investigated in conjunction with aquatic fauna and human activities at a community
level. A study area is chosen in the Northern Region of Ghana. The micro-dams in the study area serve as habitats for fish,
providing food and job opportunities for inhabitants, but their construction has sacrificed rice fields and fragmented migration
routes of fish. A stochastic population dynamics model is developed to rigorously assess the effect of establishing fish passages
between the fragmented habitats containing the micro-dams on the ichthyological fauna. Values of the model parameters are
estimated from the literature and results of field surveys, in which ten fish species including cichlidae, clariidae, bagridae,
schilbeidae, cyprinidae, and alistidae are reported to be present. A sustainability criterion is proposed to judge whether
a set of model parameters realizes stationarity of the stochastic process representing the population dynamics. It is suggested
that ichthyological fauna can be sustainable provided that the fishing activity is restricted to upstream migrating and fast
growing species. More generally, building micro-dams in West African savannas will be much better justified when the dams
are equipped with appropriately designed fish passages. 相似文献