AN ANALYTICAL RAYPATH APPROACH TO THE REFRACTION WAVEFRONT METHOD1     

M. ALI AK 《Geophysical Prospecting》1990,38(8):971-982

Seismic refraction surveying is still an important tool for determining the geometries and elastic wave propagation velocities of near-surface layers. Many analytical and graphical methods have been developed over the years for refraction interpretation, and these can be classified into two basic groups. The first group visualizes critically refracted rays converging on a common surface position, while the second group, which includes the wavefront methods, makes use of the critical rays emerging from a common point on the refractor. The method described in this paper is an analytical approach to the wavefront methods. The reverse refracted ray received by a geophone is intersected by the forward refracted rays received by subsequent geophones and a common critical refraction point on the refractor is estimated after a series of comparisons. This process is repeated for each geophone to yield the geometry and the velocity of the refractor. Several interpolations are performed to achieve a better accuracy. Palmer's models are used to test the efficiency of the algorithm. The results are presented together with those of other methods applied to the same models.  相似文献   

RESOLUTION OF STRONGLY OVERLAPPING TWO-WAY MULTICOMPONENT DATA BY MEANS OF HEURISTIC EVOLVING LATENT PROJECTIONS   总被引：3，自引：0，他引：3  

OLAV M.KVALHEIM  ALI RAHMANI  RICHARD G.BRERETON 《地理学报(英文版)》1993,(1)

High-performance liquid chromatography with diode array detection(HPLC-DAD)is used tocharacterize mixtures from chlorophyll α degradation experiments.Overlapping chromatographic peaksare resolved by means of the heuristic evolving latent projections(HELP)method.The HELP methodis a self-modelling curve resolution method.No assumptions are made about spectral and/orchromatographic peak shape.In the first step the method establishes the real noise level in the data byuse of the so-called zero-component regions.This information is used to reveal selective chromatographicinformation and the number of chemical species at every retention time in unresolved chromatographicpeaks.Utilising the selective chromatographic regions in combination with the zero-concentrationwindows,unique resolution into concentration profiles and spectra of the pure chemical species isaccomplished.HPLC-DAD data from six chlorophyll a degradation experiments were analysed.Consistent results were obtained even with very similar spectra for six or seven overlapping chemicalcomponents.  相似文献   

星基多光谱分析的降水估算     

马雷凯  邢文渊 《沙漠与绿洲气象(新疆气象)》2010,4(3):59-61

<正>对从已广泛应用的全球气候模型到局地降水和洪灾的预报而言,准确估算降水的数量、时间和空间分布是至关重要的。降水作为地球水循环的一个关键组成部分,对于人类的生命财产安全有着重要的影响。从区域到全球尺度,现存的地基降水观测网络是不足的;因此,卫星提供了一种可行和吸引人的选择。很显然,  相似文献   

Infiltration-recharge through wadi beds in arid regions     

ALI U. SORMAN  MOHAMED J. ABDULRAZZAK 《水文科学杂志》2013,58(3):173-186

Abstract

Groundwater recharge in arid regions is intermittent and usually occurs as a result of flood flow transmission losses in dry wadi channels. Hydrograph characteristics play a dominant role in determining the amount of channel abstraction in relation to the width of the wetted perimeter and the time of inundation, and the subsequent groundwater recharge. Large variations in the magnitude of channel losses result mainly from the diversity in inflow volumes. The magnitude of groundwater recharge in relation to bed transmission losses is dependent on flood volume and duration, soil moisture content and physical soil profile characteristics. Runoff volume and duration are the dominant factors influencing the cumulative infiltrated volume and recharge to shallow water tables. Taking into consideration the influence of various hydrological and channel characteristics, several regression equations are suggested to estimate the transmission losses from a wadi bed and the groundwater recharge.  相似文献   

The Chinese Carbon-Neutral Goal: Challenges and Prospects     

Ning ZENG  Kejun JIANG  Pengfei HAN  Zeke HAUSFATHER  Junji CAO  Daniel KIRK-DAVIDOFF  Shaukat ALI  Sheng ZHOU 《大气科学进展》2022,39(8):1229-1238

On 22 September 2020, within the backdrop of the COVID-19 global pandemic, China announced its climate goal for peak carbon emissions before 2030 and to reach carbon neutrality before 2060. This carbon-neutral goal is generally considered to cover all anthropogenic greenhouse gases. The planning effort is now in full swing in China, but the pathway to decarbonization is unclear. The needed transition towards non-fossil fuel energy and its impact on China and the world may be more profound than its reform and development over the past 40 years, but the challenges are enormous. Analysis of four representative scenarios shows significant differences in achieving the carbon-neutral goal, particularly the contribution of non-fossil fuel energy sources. The high target values for nuclear, wind, and bioenergy have approached their corresponding resource limitations, with solar energy being the exception, suggesting solar’s critical role. We also found that the near-term policies that allow for a gradual transition, followed by more drastic changes after 2030, can eventually reach the carbon-neutral goal and lead to less of a reduction in cumulative emissions, thus inconsistent with the IPCC 1.5°C scenario. The challenges and prospects are discussed in the historical context of China’s socio-economic reform, globalization, international collaboration, and development.  相似文献   

乌鲁木齐市城区和郊区近地层比湿分布和廓线特征          下载免费PDF全文

李振杰  金莉莉  何清  缪启龙  买买提艾力  买买提依明 《干旱区地理》2020,43(4):977-996

利用乌鲁木齐市城区和郊区的5座100 m气象铁塔10层比湿数据和乌鲁木齐气象站L波段探空雷达资料,详细分析了边界层2 km内比湿廓线特征,城区和郊区近地层比湿季节变化和日变化特征,揭示了乌鲁木齐逆湿的原因,得出以下结果：（1） 乌鲁木齐市比湿季节差异明显,冬季最小,春季、秋季稍大,夏季最大,夏季比湿约为冬季的4~5倍,但秋季仅比春季大1 g·kg^–1。除冬季外,比湿均随高度增加而趋于减小,夏季减小最显著,冬季比湿的垂直变化很小。比湿廓线极小值白天和夜间出现高度相近,且有多个极小值。夏季和冬季比湿日变化最大,且位相相反;夏季夜间大、白天小,冬季与之相反。冬季,郊区比湿小于城区;其余季节城、郊比湿差异不明显。（2） 2 km内存在逆湿现象,逆湿出现概率高于35%,概率1月最大、7月最小。1月逆湿最大高度超过1 500 m,7月逆湿最大高度可达到1 900 m,且最大厚度可达到1 550 m。逆湿强度最大在7月和10月可达2. 5 g·kg^–1·（100 m）^–1,而1月最小。（3） 1月逆湿往往与逆温相伴随,逆温层改变了水汽的垂直分布结构,从脱地逆温层顶起出现逆湿现象,逆湿还与水汽输送有关。本研究可以有效地揭示空气湿度的季节特征,为研究城市大气污染形成的气象因素提供了一个思路。  相似文献   

Exploring Placer Gold Deposits through Integrated Geophysical and Geochemical Techniques at the Confluence of the Indus and Kabul Rivers, NW Pakistan     

Asghar ALI  Khaista REHMAN  Owais TAYYAB  Tahir ZAMAN  Mahad JAMEEL  Azeem KHAN  Rafique AHMAD  Muhammad IRFAN 《《地质学报》英文版》2020,94(5):1440-1450

Analysis of the anomalous magnetic mineral intensities and geochemistry for placer gold deposits are presented for those of the Attock area at the confluence of the Indus and Kabul rivers in northwestern Pakistan. Two grids covering an area of 10x18 m2 and 8x10 m2 were analyzed using a G-858 Cesium Vapor Magnetometer. The anomalous zones obtained were plotted on contour maps, 2D and 3D magnetic intensity maps. Based on the magnetic anomalies, grid-1 of the study area was sampled at three different anomalous zones for geochemical analysis. These zones contain gold concentrations, ranging from 2.11 ppm to 6.109 ppm with an average of 4.01 ppm. Increase in gold concentration in the subsurface within the anomalous zones indicates that magnetometer survey followed by a geochemical analysis can potentially narrow down the gold-bearing anomalous zones.  相似文献   

Three-Dimensional Structural Modelling and Source Rock Evaluation of the Quseir Formation in the Komombo Basin, Egypt     

Moamen ALI 《《地质学报》英文版》2020,94(5):1619-1634

The Quseir Formation consists mainly of dark gray mudstones with a high organic matter content and excellent hydrocarbon-generating potential. The main objectives of this study are to highlight the dominant structural elements in the Komombo Basin, Egypt, and evaluate the geochemical characteristics of the Quseir Formation. Depth maps and a 3D structural model indicate two normal fault trends NW–SE and ENE–WSW. The NW–SE trend is the dominant one that created the primary half-graben system. The depth to the top of the Quseir Formation gradually decreases from the eastern and central parts towards the corners of the basin. The thickness of the Quseir Formation ranges from about 300 to 1000 ft. The 3D facies model shows that the shale has a large probability distribution in the study area, compared with the sandstone and siltstone. The source rock potential varies between good in the western part to very good in the eastern part of the basin. The organic-rich interval is dominated by gas-prone kerogen type III based on TOC and Rock-Eval. The pyrolysis data vitrinite reflectance (%Ro) (0.5–0.74%) and Tmax values (406–454C°) suggest a maturity level that ranges from immature to early maturity stage for hydrocarbon generation.  相似文献   

The tectono‐metamorphic evolution of the Balcooma Metamorphic Group,north‐eastern Australia: a multidisciplinary approach     

A. ALI 《Journal of Metamorphic Geology》2010,28(4):397-422

The sequential growth of biotite, garnet, staurolite, kyanite, andalusite, cordierite and fibrolitic sillimanite, their microstructural relationships, foliation intersection axes preserved in porphyroblasts (FIAs), geochronology, P–T pseudosection (MnNCKFMASH system) modelling and geothermobarometry provide evidence for a P–T–t–D path that changes from clockwise to anticlockwise with time for the Balcooma Metamorphic Group. Growth of garnet at ～530 °C and 4.6 kbar during the N–S‐shortening event that formed FIA 1 was followed by staurolite, plagioclase and kyanite growth. The inclusions of garnet in staurolite porphyroblasts that formed during the development of FIAs 2 and 3 plus kyanite growth during FIA 3 reflect continuous crustal thickening from c. 443 to 425 Ma during an Early Silurian Benambran Orogenic event. The temperature and pressure increased during this time from ～530 °C and 4.6 kbar to ～630 °C and 6.2 kbar. The overprinting of garnet‐, staurolite‐ and kyanite‐bearing mineral assemblages by low‐pressure andalusite and cordierite assemblages implies ～4‐kbar decompression during Early Devonian exhumation of the Greenvale Province.  相似文献   

气泡混合轻质土试样制备研究     

周云东  王勇  黎冰  徐佳辉  刘萌成  Ali H Mahfouz 《岩土力学》2018,39(12):4413-4420

由于气泡消泡的缘故,室内制备和现场浇筑气泡混合轻质土时存在塌陷问题。为分析和解决该问题,以砂土为原料土,开展了不同温差、湿度和掺砂与否条件下3种密度气泡混合轻质土的制备试验,并测定了各试样的高度和强度,基于热力学理论分析了3种因素对试样制备和强度的影响规律。试验结果表明,试样制备时温度与养护温度之间的温差是影响气泡混合轻质土胀缩性的决定性因素,轻质土中的气泡含量越高,受温差影响越大,通过控制温差即可解决塌陷问题;湿度和掺砂与否对气泡混合轻质土的试样制备影响不明显,但是湿度高会延长试样脱模时间以及影响试样的完整性;温差和温度共同影响气泡混合轻质土的早期强度,其中温差主要影响试样密实度,温度主要影响水泥水化反应速率。试验结果可为气泡混合轻质土制备和施工时间点选择提供借鉴。  相似文献