Causes of rockfalls in Al-Huwayshah area, Yemen          下载免费PDF全文

Aref M. O. AL-JABALI  NIE Lei  Abdo S. AL-MAQTARY  Hussein AL-AKHALI  Mohammed HAZAEA  Fadel AL-AGHBARI 《世界地质(英文版)》2009,12(1):5-12

According to topography of Yemen, most areas and villages are located at obligated crest, toe of mountain and under cliffs. Therefore Al-Huwayshah consisting of Tawilah sandstone group is characterized by steep slope reach to 90° in some areas. This area is affected by strong tectonic movements and faults that occurred during the geological epochs. This effect enhances to find out fractures and joints as well as the rocks become brittle and ready to slide depending on the position of area. And there are some fractures and joints on the surface of the areas due to tectonic movement associated with opening the Red Sea and Gulf of Aden. The rainfalls, fractures, joints, earthquakes, gravity, vegetations, temperatures and human activities play a big role in the processes of rockfalls and landslides in this area. All those factors are considered as the basic causes and catalyzed factors for occurrence of rockfall in the studide area. In addition, the authors carried out laboratory test for many rock samples to get the physical properties of the rocks.  相似文献   

River fisheries management in Bangladesh: Drawing lessons from Community Based Fisheries Management (CBFM) experiences     

Mohammed A. Rab   《Ocean & Coastal Management》2009,52(10):533-538

River fisheries in Bangladesh is characterized as “open-access” and the history of administrative and legislative measures bear “contradiction and dilemmas” in resource extraction. The 1950 Fisheries act, the proclamation of 1973 that restricted lease to the registered fisher cooperatives and the experimental New Fisheries Management Policy (NFMP) of 1986 could not contribute to devolve into any participatory institution to introduce sustainable fisheries management. Because of the persistent dilemma in government policy, continued increase in fishing pressure and other anthropogenic reasons, the River resources degraded substantially. Over the past ten years, the Department of Fisheries (DOF) in collaboration with NGOs implemented community based fisheries management (CBFM) approaches with the technical assistance from the WorldFish Center. The principal goal of the approaches was to provide access rights to the fishers through organizing poor fishers and the community to introduce sustainable fisheries management in beels, floodplains and River sections. The CBFM experiences suggest that management and institution building process in river management is complex, and require participation of all concerned stakeholders including local government institutions and administration. CBFM-2 river fisheries management developed a broad-based institutional framework that include community and local government along with the direct beneficiaries and resource users. A positive feature of such institutions is its ability to facilitate flow of information among agents, which is a key to maintain solidarity within and across groups. This paper draws lessons from the CBFM experiences in Bangladesh to manage river fisheries resources in Bangladesh.  相似文献   

Unsteady hydromechanics of a steering podded propeller unit     

Pengfei Liu  Mohammed Islam  Brian Veitch 《Ocean Engineering》2009,36(12-13):1003-1014

Unsteady forces, torques and bending moments were predicted for a model podded propulsor unit at various azimuth angles. Predictions in time history include propeller shaft thrust, propulsor unit thrust, normal forces to the propeller shaft bearing, total forces acting on the propulsor unit, propeller shaft torque, blade spindle torque, in-plane and out-of-plane bending moments, and propulsor unit stock shaft torque and bending moments. Analysis was performed for averaged forces and their fluctuations as well. A time-domain unsteady multi-body panel method code, PROPELLA, was further developed for this prediction work. Predictions were compared with a set of time averaged in-house experimental data for a puller-type podded propulsor configuration in the first quadrant operation. Unsteady fluctuations of forces were predicted numerically. Analysis was made for the bending moment on propeller blades, shaft and the propulsor unit stock shaft for azimuth angles from 0° to 45°. It indicates that the magnitude and fluctuation of the forces are significant and they are essential for structural strength and design optimization. The predicted bending moment and global forces on the propulsor unit provide some useful data for ship maneuvering motion and simulation in off-design conditions.  相似文献   

Causes of rockfalls in Al-Huwayshah area,Yemen     

Aref M.O.AL-JABALI  Abdo S.AL-MAQTARY  Hussein AL-AKHALI  Mohammed HAZAEA  Fadel AL-AGHBARI 《东北亚地学研究》2009,(1)

According to topography of Yemen,most areas and villages are located at obligated crest,toe of mountain and under cliffs.Therefore Al-Huwayshah consisting of Tawilah sandstone group is characterized by steep slope reach to 90° in some areas.This area is affected by strong tectonic movements and faults that occurred during the geological epochs.This effect enhances to find out fractures and joints as well as the rocks become brittle and ready to slide depending on the position of area.And there are some frac...  相似文献   

Slope stability FEM analysis and retaining wall design: a case study of clinker in Benxi of Liaoning     

Aref M. O. AL-JABALI  Lei NIE  Jianlei LIU  Huangping DING  Nengjuan ZHOU  Mohammed HAZAEA 《世界地质(英文版)》2008,11(2)

Stability is always the most important problem after high slope was excavated. The study analyzed the stress and strain inside the slope by Finite Element Method (FEM) and carried through stress distribution and failure zone, then analyzed the stability of the slope using three different methods and came to the conclusion that it is in unstable condition, so the designed retaining wall was put forward which makes the slope stable.  相似文献   

Book reviews     

T. Littmann  Rudolf Brázdil  Manfred Domrös  Mohammed A. Kishk  A. Wallner  Radan Květ  Andreas Grotewold 《GeoJournal》1992,26(4):547-549

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The marine killers: Dinoflagellates in estaurine and coastal waters     

Shoukri N. Messieh  Mohammed I. El-Sabh 《Natural Hazards》1984,3(1):69-86

Records of massive fish kills and paralytic shellfish poisoning (PSP) in Europe and North America go back to the 17th century. But, it was not until the 1940s when the relationship between PSP, red tide and toxic dinoflagellateGonyaulax was established. Recent records show that PSP and related poisons caused by toxic dinoflagellates in coastal waters and estuaries, are a world-wide problem. Diarrhetic shellfish poisoning (DSP) and neurotoxic poisoning (NSP), believed earlier as bacterial or viral infections are now shown to be caused by other toxic dinoflagellates such asDinophysis. The shellfish most often involved in the poisoning are mussels and clams. Other dinoflagellates,Gyrodinium, occasionally cause massive fish kills in vast coastal areas, resulting in fishery and economic losses.Factors promoting toxic dinoflagellate bloom development and PSP/DSP outbreaks are not fully understood. In previous studies, temperature was considered as the principal factor influencing dinoflagellate blooming. Recent studies showed that other factors such as salinity, sunlight, freshwater runoff and water stability are also important. Pollution from land drainage and sewage discharge in inshore waters were also implicated.Current knowledge indicates that although chemical and biotic factors are important forin-situ growth of dinoflagellate cells, convergence by thermal and tidal fronts is essential for cell accumulation and bloom development. Advances in physical oceanographic research, modelling and remote sensing enabled the detection of fronts and bordering eddies with high precision. There is a potential for an increased use of these technological advances in predicting and monitoring the bloom development.The present paper overviews the history and distribution of toxic dinoflagellates, and the physical factors influencing bloom development and PSP/DSP outbreaks. Future research needs to improve the predictability and control of this world-wide hazard are also discussed.  相似文献   

Foreword     

Mohammed Bensaid 《International Journal of Earth Sciences》1992,81(1):I-I

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Dynamics of particle creation in relativistic viscous fluid Universe in Brans Dicke theory     

L. Ibochouba  Mohammed Ashraf Ali 《Astrophysics and Space Science》1996,241(2):227-235

The study of dynamics of the particle creation in relativistic viscous fluid in Robertson-Walker Universe is studied by using Brans-Dicke theory. The behaviour of these solutions with respect to Dirac's hypothesis are investigated along with the discussion of the physical parameters as well as the variable gravitational constant. By adopting a particular method of integration, exact solutions are obtained and physical interpretations are presented.  相似文献   

Optical and radiative properties of aerosols over Abu Dhabi in the United Arab Emirates     

S Naseema Beegum  Haifa Ben Romdhane  Mohammed Tauha Ali  Peter Armstrong  Hosni Ghedira 《Journal of Earth System Science》2016,125(8):1579-1602

The present study is on the aerosol optical and radiative properties in the short-wave radiation and its climate implications at the arid city of Abu Dhabi (24.42 ^°N, 54.61 ^°E, 4.5 m MSL), in the United Arab Emirates. The direct aerosol radiative forcings (ARF) in the short-wave region at the top (TOA) and bottom of the atmosphere (BOA) are estimated using a hybrid approach, making use of discrete ordinate radiative transfer method in conjunction with the short-wave flux and spectral aerosol optical depth (AOD) measurements, over a period of 3 years (June 2012–July 2015), at Abu Dhabi located at the south-west coast of the Arabian Gulf. The inferred microphysical properties of aerosols at the measurement site indicate strong seasonal variations from the dominance of coarse mode mineral dust aerosols during spring (March–May) and summer (June–September), to the abundance of fine/accumulation mode aerosols mainly from combustion of fossil-fuel and bio-fuel during autumn (October–November) and winter (December–February) seasons. The monthly mean diurnally averaged ARF at the BOA (TOA) varies from ?13.2 Wm^?2 (～?0.96 Wm^?2) in November to ?39.4 Wm^?2 (?11.4 Wm^?2) in August with higher magnitudes of the forcing values during spring/summer seasons and lower values during autumn/winter seasons. The atmospheric aerosol forcing varies from + 12.2 Wm^?2 (November) to 28.2 Wm^?2 (June) with higher values throughout the spring and summer seasons, suggesting the importance of mineral dust aerosols towards the solar dimming. Seasonally, highest values of the forcing efficiency at the surface are observed in spring (?85.0 ± 4.1 W m^?2 τ ^?1) followed closely by winter (?79.2 ± 7.1 W m^?2 τ ^?1) and the lowest values during autumn season (?54 ± 4.3 W m^?2 τ ^?1). The study concludes with the variations of the atmospheric heating rates induced by the forcing. Highest heating rate is observed in June (0.39 K day ^?1) and the lowest in November (0.17 K day ^?1) and the temporal variability of this parameter is linearly associated with the aerosol absorption index.  相似文献