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排序方式: 共有250条查询结果,搜索用时 15 毫秒
51.
Md. Sirajul Islam G. M. Jahid Hasan Md. Aktarul Islam Chowdhury 《International Journal of Environmental Science and Technology》2006,2(4):301-308
Indiscriminate cutting of hills in the Sylhet region has become a major environmental issue. The nature and life style of Sylhet intimately related with the hills are thus under the threat of a drastic imbalance in its ecosystem. Due to such hill cutting the mostly affected sectors of this region will be its weather and climate, geomorphology and hydrology, and the indigenous flora and fauna. As a result the frequency of natural calamities like earthquake, flash flooding etc may increase considerably. Deforestation and resulting increased soil erosion, decreased ground water recharge and deteriorated water quality might also be as consequences of such hill cutting. This paper investigates the cause and extent of the problem along with its probable impact and finally suggests actions for conservation of hills for ecological balance of the region. 相似文献
52.
近14 a也门降水异常的气候特征 总被引:2,自引:0,他引:2
利用1990-2003年也门7个测站降水资料,在分析近148也门降水季节变化特征的基础上,着重分析了也门夏季降水的年际变化特征。结果表明,也门降水异常的季节变化明显,异常在4-9月最大,尤其是7-9月,异常峰值所在月呈现出较明显的提早趋势;近148也门夏季降水呈现出增加的趋势,90年代末该趋势加大;近148也门夏季降水存在38和78左右的显著振荡周期。 相似文献
53.
Ömer Emre Tamer Y. Duman Selim Özalp Fuat Şaroğlu Şeyda Olgun Hasan Elmacı Tolga Çan 《Bulletin of Earthquake Engineering》2018,16(8):3229-3275
We have updated the active fault map of Turkey and built its database within GIS environment. In the study, four distinct active fault types, classified according to geochronological criteria and character, were delineated on the 1:25,000 base map of Turkey. 176 fault segments not included in the former active fault map of Turkey, have been identified and documented. We infer that there are 485 single fault segments which are substantially potential seismic sources. In total 1964 active-fault base-maps were transferred into the GIS environment. Each fault was attributed with key parameters such as class, activity, type, length, trend, and attitude of fault plane. The fault parameters are also supported by slip-rate and seismogenic depth inferred from available GPS, seismological and paleoseismological data. Additionally, expected maximum magnitude for each fault segment was estimated by empirical equations. We present the database in a parametric catalogue of fault segments to be of interest in earthquake engineering and seismotectonics. The study provides essential geological and seismological inputs for regional seismic hazard analysis of all over Turkey and its vicinity. 相似文献
54.
ADEL Mil PALANISAMY Satheesh Kumar SHAFIEI Shafigh FAZLI Hasan ZORRIEHZAHRA Mohammad Jalil 《海洋学报(英文版)》2016,35(8):39-43
Sturgeons are the most important principal market species in the Caspian Sea. In the present study, measurement of blood parameters was carried out with the aim of evaluating the normal value of hematological and serum biochemical parameters of brood stocks Acipenser persicus during spawning season. Blood samples were collected from 36 brood stocks of A. persicus (18 males and 18 females) during the spawning season. Higher value of red blood cells, white blood cells, haemoglobin, haematocrit was observed in male breeders with significant differences between female breeders (p>0.05). Haemoglobin and haematocrit value in this study was within the range of 8.70 to 9.2 g/dL and 29.73% to 30.26%, respectively. The statistically significant differences between mean corpuscular volumes, mean corpuscular haemoglobin, lymphocyte and neutrophil percentages, aspartate aminotransferase, alkaline phosphatase and creatine kinase were observed in the male and female brood stocks. It is concluded from this study, some of the hematological and serum biochemical parameters of male and female A. persicus breeders were significantly varied from each other. In comparative investigation with earlier reports, the values of red blood cells, haemoglobin and haematocrit are highly varied due to age variations of fish. However, further studies are necessary to understand the impact of sexual, age, size, length, and season and habitat variation. Serum biochemical parameters can be used for confirming the maturity of A. persicus and monitoring any changes in the water quality parameters and soil. 相似文献
55.
The November 27, 2005 Qeshm Island earthquake (Mw 6.0) occurred along the Zagros Thrust and Fold Belt which accommodates about half of the deformation caused by the Arabian and Eurasian Plates convergence. As typical for the belt, the earthquake was associated with buried reverse faulting and produced no surface rupture. Here, teleseismic broadband P velocity waveforms of the earthquake are inverted to obtain coseismic finite-fault slip distribution of the earthquake. It is obtained that rupture was controlled by failure of a single asperity with largest displacement of approximately 0.6 m, which occurred at a depth of 9 km. The slip model indicated radial rupture propagation from the hypocentre and confirmed blind reverse faulting within deeper part (below the depth of 6 km) of the sedimentary cover above the Hormuz Salt, lying between the cover and the basement, releasing a seismic moment of about 1.3?×?1018 Nm (MW?=?6.0). The results also confirm that the Hormuz Salt behaves as a barrier for rupture propagation to the basement below and occurrence of the aftershock activity downdip from the rupture within the Hormuz Salt. Calculated Coulomb stress variations caused by the coseismic rupture indicates stress coupling between the 2005 Qeshm Island earthquake and both the largest aftershock several hours later and the 2008 Qeshm Island earthquake (MW?=?5.9). The stress calculations further indicated stress load at the depth range (15–20 km) of the well-located aftershocks, corresponding to depths of the Hormuz Salt and top of the basement and providing plausible explanation for occurrence of the aftershocks within those layers. 相似文献
56.
为了更好地评价和推进生态文明建设,改进足迹家族并构建生态文明建设评价指标体系,以新疆为例进行试评估。结果表明:1990-2013年新疆的生态文明建设属中等水平。其中,生态压力一直处于低水平;温室气体由低排放升为高排放;水资源从中等压力升至高压力;社会发展由低水平上升至中等。空间上,2013年克孜勒苏州、阿勒泰地区、巴音郭楞州和伊犁直属县市的生态文明建设水平高,博尔塔拉州、塔城、喀什、和田及阿克苏等地区为中等水平,乌鲁木齐市、克拉玛依市、吐鲁番地区、哈密地区和昌吉州的水平低。研究表明,制约新疆生态 文明建设的主要因子是温室气体排放高和水资源压力大,节能减排和节水是今后需要努力的方向。 相似文献
57.
A GIS model for preliminary hazard assessment of swelling clays,a case study in Harran plain (SE Turkey) 总被引:1,自引:1,他引:1
Swelling behavior of clayey soils regarded as a hidden disaster, causes a great deal of damage in light hydraulic structures
such as drinking water network, irrigation pipes or open canal linings through which water can easily leak and penetrate into
soil during loading and unloading stages. Early identification during site investigation and laboratory testing is extremely
important to ensure that the appropriate design strategy is adopted. The clay soils having swelling potential are generally
found in arid and semi-arid regions, such as in the Şanlıurfa-Harran plain located in the southeast of Turkey. The problems
associated with swelling clays occurred for the lightweight hydraulic structures constructed in Turkey have been met during
the construction of irrigation structures in the scope of Southeast Anatolian Project as the Turkey’s greatest water resources
project. Therefore, the identification of such soils and the assessment of their swelling potential parameters are necessary
for hazard mitigation planning and land-use management. In this scope, extensive geotechnical study is executed for an investigation
area. The samples were obtained from the Harran plain where many irrigation canal structures are constructed, and geotechnical
study was performed on these samples. Atterberg limit tests often provide the basic field information to substantiate the
soil’s swelling nature. The plasticity index (PI) and liquid limit (LL) values are also used extensively for classifying swelling
soil and should always be determined during preliminary investigations. Because of this, LL and PI are assessed by using geographical
information system (GIS)-based computer software, and LL and PI contour maps are created. Swelling percentages of the soil
samples were carried out on both undisturbed and compacted soil samples by using direct methods. As a result of this extensive
study, the values of swelling percentages determined for each location are used to obtain the swelling potential hazard map
of the area by means of a GIS program. The results of GIS analyses for this area indicate that the analyses based on a lot
of data introduce meaningful results for this study. It is expected that these maps will be a useful tool for planners and
engineers in their efforts to achieve better land-use planning and to decide necessary remedial measures. 相似文献
58.
59.
The Afyon stratovolcano exhibits lamprophyric rocks, emplaced as hydrovolcanic products, aphanitic lava flows and dyke intrusions, during the final stages of volcanic activity. Most of the Afyon volcanics belong to the silica-saturated alkaline suite, as potassic trachyandesites and trachytes, while the products of the latest activity are lamproitic lamprophyres (jumillite, orendite, verite, fitztroyite) and alkaline lamprophyres (campto-sannaite, sannaite, hyalo-monchiquite, analcime–monchiquite). Afyon lamprophyres exhibit LILE and Zr enrichments, related to mantle metasomatism. 相似文献
60.
Haris Hasan Khan Arina Khan Shakeel Ahmed Marie-Claude Gennero Kien Do Minh Anny Cazenave 《Arabian Journal of Geosciences》2013,6(10):3693-3702
In this study, the hydrodynamics of lower Ganges basin in India has been monitored using radar altimetry data from environmental satellite (ENVISAT) mission and microgravity data from the Gravity Recovery and Climate Experiment (GRACE) mission. River stage time series have been constructed for different virtual stations on the lower Ganges. Time series for the integrated water volume changes from microgravity measurements have also been constructed to characterize the seasonal and interannual fluctuation patterns in water storage and flux. The ENVISAT dataset indicates an average seasonal river stage fluctuation of 8 m in the lower Ganges River. The GRACE dataset reveals a seasonal fluctuation ranging from 0.18 to 0.40 m in the vertically integrated total water storage in the lower Ganges basin. The two independent datasets show broad similarity in the lower Ganges basin and outline the importance of space-based techniques for monitoring continental water resources. 相似文献