排序方式： 共有16条查询结果，搜索用时 515 毫秒
1.
Correlations between Compression Index and Index Properties of Undisturbed and Disturbed Tehran clay
Akbarimehr Davood Eslami Abolfazl Imam Reza 《Geotechnical and Geological Engineering》2021,39(7):5387-5393
The compression index (Cc), which is used to calculate the consolidation settlement of fine-grained soils, can be determined through consolidation testing. Given that exploring the soil in a local region is highly important to determine the correlation between the Cc and other soil indices, the present study investigated these correlations in undisturbed and disturbed samples through 130 consolidation tests and determining the Cc of Tehran clay. The results are suggestive of the validity of the linear correlation between the Cc and the unit weight and initial void ratio of the soil, with several relations presented to estimate the Cc of Tehran clay soil. In contrast, the initial water content, liquid limit and the plasticity index do not produce reliable correlations with the Cc of the local clay soil, and a relation based on these index parameters cannot be recommended in this area. Further, the presented empirical correlations were compared with the existing ones. More over time-displacement and e-log σ’ graphs for undisturbed and disturbed samples are compared and stress history of the site are presented. The results are significant in terms of engineering applications, saving time and money and provides an initial estimation of compression index.
相似文献2.
Joseph Sidky Mikhail Nabil Shoukry Awadalla Imam Ibrahem Ahmed 《Earth, Moon, and Planets》1976,15(3-4):353-402
Photoelectric observations have been carried out during maximum solar activity in order to investigate the variation of the brightness of the lunar surface with the solar cycle and to detect the possiblity of existing colour anomaly. The brightness data, using a wide-passband filter, do not show any evidence of variation with the solar cycle. No colour anomaly is found for the investigated lunar regions, and the doubt that has been felt by some investigators about the nonexistence of certain colour indices' variation with phase is not confirmed. 相似文献
3.
Hospital service area (HSA) and hospital referral region (HRR), known as a hierarchical HSA system, have been used as analysis units in a growing body of large‐scale studies of healthcare spending, utilization, and outcome in the United States. However, the popular Dartmouth HSAs and HRRs were produced more than two decades ago and are unable to represent contemporary healthcare markets. This research uses a revised Huff Model to delineate two levels of hospital service areas in Florida, resulting in sixty‐four HSAs nested in twenty‐one HRRs. Three elements distinguish our method from existing work. First, a best‐fitting distance‐decay function derived from the actual travel pattern of hospitalization is embedded in the Huff Model to strengthen the model's theoretical foundation in individual spatial behavior. Secondly, the hierarchal central place structure is supported by the differing travel‐friction coefficients for general versus specialized patients; general patients experience a steeper gradient and thus a shorter average travel range that supports delineating more HSAs of smaller area size, and specialized patients exhibit a flatter gradient and thus a longer average travel range that leads to fewer HRRs of large‐sized areas. Finally, the delineation method automated in geographic information systems (GIS) can be easily replicated in other regions to define large‐scale and consistent hierarchical HSA systems. 相似文献
4.
Biodegradation of toxic chemicals in Guayanilla Bay,Puerto Rico 总被引：1，自引：0，他引：1
Studies were conducted to assess the factors that may influence the rate and extent of biodegradation of biphenyl, naphthalene, phenanthrene, pentachlorophenol (PCP) and p-nitrophenol in water samples collected from the Guayanilla Bay (18 degrees N; 67.45 degrees W), southwest of Puerto Rico. In vitro studies mediated slow degradation of biphenyl, naphthalene and phenanthrene substrates by natural microbial flora present in the Bay. Addition of KNO(3) as a source of inorganic N greatly enhanced the degradation of phenanthrene but not of naphthalene, suggesting that effects on degradation due to nutrient limitation were compound specific. The rate and extent of degradation of naphthalene and PCP were higher in water samples collected closer to the source of contamination, i.e. the petrochemical complex. The identity of a phenanthrene degrading bacterium, previously identified by conventional phenotypic method (Zaidi et al., Utilizing Nature's Advanced Materials, Oxford Unviersity Press, 1999) as Alteromonas sp., was confirmed by partial DNA sequencing of the small subunit rRNA gene. 相似文献
5.
Explaining foreign diplomatic presence in the U.S. with spatial models: a liberal spatial perspective 总被引：1，自引：0，他引：1
This paper examines the effect of economic interdependence, intergovernmental organizations, political freedom, and spatial relationship on foreign diplomatic presence in the U.S. from 1980 to 2000. Spatial perspective is largely missing in the mainstream international theories. Spatial relationship has three measures: spatial proximity measured as distance, spatial dependency measured as neighborhood effect, and spatial heterogeneity measured as regional effect. We found that the effect of economic interdependence is directional. The U.S. sensitivity to foreign trade rather than foreign sensitivity to trade with the U.S. explains much of the variation in the foreign diplomatic presence in the U.S. Spatial effect is mainly manifested as spatial dependency; the effects of geographic proximity and geographic regions on foreign diplomatic presence are, however, mild. Spatial dependency in the variation of foreign diplomatic presence in the U.S. could not be well explained by the liberal perspective without using the spatial model.
相似文献
| Lin Liu ([Summer Visiting Professor])Email: |
6.
Khalid A. Al-Ramadan Mahbub Hussain Badrul Imam Salih Saner 《Marine and Petroleum Geology》2004,21(10):1221-1234
The Lower Devonian Jauf Formation in Saudi Arabia is an important hydrocarbon reservoir. However, in spite of its importance as a reservoir, published studies on the Jauf Formation more specifically on the reservoir quality (including diagenesis), are very few. This study, which is based on core samples from two wells in the Ghawar Field, northeastern Saudi Arabia, reports the lithologic and diagenetic characteristics of this reservoir. The Jauf reservoir is a fine to medium-grained, moderate to well-sorted quartz arenite. The diagenetic processes recognized include compaction, cementation (calcite, clay minerals, quartz overgrowths, and a minor amount of pyrite), and dissolution of the calcite cements and of feldspar grains. The widespread occurrences of early calcite cement suggest that the Jauf reservoir lost a significant amount of primary porosity at a very early stage of its diagenetic history. Early calcite cement, however, prevented the later compaction of the sandstone, thus preserving an unfilled part of the primary porosity. Based on the framework grain–cement relationships, precipitation of the early calcite cement was either accompanied or followed by the development of part of the pore-lining and pore-bridging clay cement. Secondary porosity development occurred due to partial to complete dissolution of early calcite cements and feldspar. Late calcite cement occurs as isolated patches, and has little impact on reservoir quality of the sandstones.In addition to calcite, several different clay minerals including illite and chlorite occur as pore-filling and pore-lining cements. While the pore-filling illite and chlorite resulted in a considerable loss of porosity, the pore-lining chlorite may have helped in retaining the porosity by preventing the precipitation of syntaxial quartz overgrowths. Illite, which largely occurs as hair-like rims around the grains and bridges on the pore throats, caused a substantial deterioration to permeability of the reservoir. Diagenetic history of the Jauf Formation as established here is expected to help better understanding and exploitation of this reservoir. 相似文献
7.
Hospital service areas (HSAs) are increasingly adopted as a basic analysis unit for health care studies. The popular Dartmouth HSAs were produced more than two decades ago, and the process was far from automated. This research uses a Huff-based model automated in a geographic information systems (GIS) environment to delineate HSAs. Based on the Florida State Inpatient Database (SID) in 2011, a best-fitting distance decay function is derived from the actual travel patterns of hospitalization and then fed into the Huff model to strengthen the model's theoretical foundation in individual spatial behavior. The HSAs derived from the Huff-based model are then compared to the traditional flow-based HSAs defined by the Dartmouth method and assessed in terms of self-containment and heterogeneity of internal socioeconomic structure and urbanicity. The Huff-based model requires fewer data and is easy to implement as an automated toolkit and thus has great potential for replication in other regions to define large-scale and consistent HSAs. 相似文献
8.
E. H. Imam S. A. El Baradei 《International Journal of Environmental Science and Technology》2009,6(2):315-324
This research studies the impact of water level control structures on self-assimilative capacity of rivers and on fish habitat. Constructing a water level control structure in a river reach will alter its hydraulics as well as its water quality, thermal regime and fish habitat. A mathematical model is developed to simulate river hydraulics, water quality, temperature and fish habitat. Diurnal dissolved oxygen concentrations are investigated to show their impact on fish. A case of a Nile River reach was studied to investigate the impact of the existence of the Esna barrage on the water quality and fish in its upstream reach. The barrage has negative impacts on the upstream self-assimilative capacity of the rivers. The waste load that the river could absorb was only 54 % (at low flow) and 78 % (at high flow) of the entire load if no barrage was present. Including in the simulation of the effects of photosynthesis and respiration, the above mentioned percentages were raised to 54 % and 91 %, respectively. Although water level control structures have negative impacts on the upstream self-assimilative capacity of the rivers, they have positive effect on downstream dissolved oxygen concentrations due to reaeration that happens across them. Downstream dissolved oxygen concentration increased by 6 % from its upstream concentration value. The barrage has a positive effect on fish habitat in the upstream section. The weighted usable area of Tilapia fish is doubled in case of barrage existence. The barrage causes a slight decrease in water temperature that reaches an average of 0.13 degree in the month of June. 相似文献
9.
10.
Y. E. Imam B. E. Laval G. A. Lawrence 《Aquatic Sciences - Research Across Boundaries》2013,75(2):213-233
Field data and two linear layered models were used to examine the baroclinic response to wind in a small elongated two-basin lake, Amisk Lake (Alberta, Canada). For the first vertical baroclinic mode, wind-forced horizontal modes were simulated using a dynamic two-layer variable cross-section (TVC) model. The first horizontal mode, H1, was found to dominate the exchange between the two basins of Amisk Lake. The highest velocities associated with H1 occurred in the constricted channel connecting the two basins. This high velocity led to strong damping which brought H1 in near-resonance with the diurnal wind despite a difference in periods. Along with H1, the second horizontal mode, H2, was detected at a thermistor mooring. The TVC showed that H2 resulted from the coupling between along-thalweg wind distribution and the bathymetry of Amisk Lake. The damping for H2 was found to be weaker than for H1, likely because of weaker bottom drag in the connecting channel. The evolution of vertical H1 modes were simulated using a multi-layered box model. In response to wind pulses, the first vertical mode V1H1 initially dominated over higher vertical modes causing two-layer exchange. Following the faster decay of V1H1, higher vertical modes shifted the exchange to three and more layers. Our study shows the importance of the coupling between wind stress distribution and lake bathymetry in exciting horizontal modes, reveals the effect of damping on resonance with wind, and explains the evolution of exchange associated with vertical modes. 相似文献