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排序方式: 共有101条查询结果,搜索用时 15 毫秒
1.
Kevin Fong 《Earth, Moon, and Planets》2004,94(3-4):169-176
Human space exploration is not considered a strategic priority in the United Kingdom at present. However the UK would benefit from participating in human spaceflight, for both scientific and social reasons. From the point of view of medical science there are many parallels between the physiology of spaceflight and terrestrial disease processes, and studies of the response of astronauts to long-duration spaceflight can therefore help in the development of therapeutic strategies on Earth. On the social side, human spaceflight is an attractive vehicle for stimulating the interest of young people in science and engineering, something that must be of value for an aspiring ‘knowledge-based’ economy. 相似文献
2.
We conducted a laboratory experiment to quantify nutrient (nitrogen and phosphorus) limitation of macroalgae collected along
a gradient in water column nutrient availability in Upper Newport Bay estuary, a relatively nutrient-rich system in southern
California, United States. We collectedEnteromorpha intestinalis and water for use in the experiment from five sites ranging from the lower end of the estuary to the head. Initial algal
tissue N and P concentrations and molar N∶P ratios—as well as water column NO3 and total Kjeldahl nitrogen (TKN)—increased along a spatial gradient from the lower end toward the head. Water column soluble
reactive phosphorus (SRP) varied among sites as well but did not follow a pattem of increasing from the seaward end toward
the head. Algae from each site were assigned to one of four experimental treatments: control (C), nitrogen enrichment (+N),
phosphorus enrichment (+P), and nitrogen and phosphorus enrichment (+N+P). Each week for 3 wk we replaced the water in each
unit with the appropriate treatment water to mimic a poorly flushed estuary. After 3 wk, the degree of nutrient limitation
ofE. intestinalis varied spatially with distance from the head of the estuary. Growth ofE. intestinalis collected from several sites increased with N enrichment alone and increased further when P was added in combination with
N This indicated that N was limiting and that when N was sufficient, P became limiting. Sites from whichE. intestinalis exhibited nutrient limitation spanned the range of background water column NO3 (12.9±0.4 to 55.2±2.1 μM) and SRP (0.8±0.0 to 2.9±0.2 μM) concentrations. Algae that were N limited had initial tissue N
levels ranging from 1.18±0.03 to 2.81±0.08% dry weight and molar N∶P ratios ranging from 16.75±0.39 to 26.40±1.98. 相似文献
3.
To accurately predict soil volume changes under thermal cycles is of great importance for analysing the performance of many earth structures such as the energy pile and energy storage system. Most of the existing thermo‐mechanical models focus on soil behaviour under monotonic thermal loading only, and they are not able to capture soil volume changes under thermal cycles. In this study, a constitutive model is proposed to simulate volume changes of saturated soil subjected to cyclic heating and cooling. Two surfaces are defined and used: a bounding surface and a memory surface. The bounding surface and memory surface are mainly controlled by the preconsolidation pressure (a function of plastic volumetric strain) and the maximum stress experienced by the soil, respectively. Under thermal cycles, the distance of the two surfaces and plastic modulus increase with an accumulation of plastic strain. By adopting the double surface concept, a new elastoplastic model is derived from an existing single bounding surface thermo‐mechanical model. Comparisons between model predictions and experimental results reveal that the proposed model is able to capture soil volume changes under thermal cycles well. The plastic strain accumulates under thermal cycles, but at a decreasing rate, until stabilization. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
4.
5.
Geophysical analysis of zonal tidal signals in length of day 总被引:5,自引:0,他引:5
Benjamin Fong Chao James B. Merriam Yoshiaki Tamura 《Geophysical Journal International》1995,122(3):765-775
6.
Changes in global gravitational energy induced by earthquakes 总被引:1,自引:0,他引:1
Benjamin Fong Chao Richard S. Gross Da-Nan Dong 《Geophysical Journal International》1995,122(3):784-789
7.
1980~1994年台湾海峡两岸的地热涡与降水季度预报初探 总被引:4,自引:0,他引:4
利用1980~1994年大陆3.2m深度和台湾3.0m深度的地温资料,分析了15a来的逐季地气图,统计了台湾海峡两岸的地热涡活动,发现平均每季有1个地热涡活动,其水平尺度比大陆内部的地热涡要小,生命史也要短,进入台湾地区的地热涡绝大多数是从西方和北方进入,其移动速度比大陆内部的要快得多。90%以上的地热涡在同期有多雨区与其对应,热涡中心与多雨中心相距在100km以内者占68%。最后给出了一个季度降水的定性预测方案,其步骤为:预报地热涡的中心位置、强度和水平尺度;推算降水正距平区的水平尺度、中心位置和强度;根据本区发生的地震等情况进行预报订正。 相似文献
8.
Input determination has a great influence on the performance of artificial neural network (ANN) rainfall–runoff models. To improve the performance of ANN models, a systematic approach to the input determination for ANN models is proposed. In the proposed approach, the irrelevant inputs are removed. Then an adequate ANN model, which only includes highly relevant inputs, is constructed. Unlike the trial‐and‐error procedure, the proposed approach is more systematic and avoids unnecessary trials. To demonstrate the effectiveness of the proposed approach, an application to actual typhoon events is presented. The results show that the proposed ANN model, which is constructed by the proposed approach, has advantages over those obtained by the trial‐and‐error procedure. The proposed ANN model has a simpler architecture, needs less training time, and performs better. The proposed ANN model is recommended as an alternative to existing rainfall–runoff ANN models. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
9.
Mohamad Zam Zuriyati Yang Fong Chee Charles Ramendran S. P. R. Rehman Mobashar Nee Au Yong Hui Yin Yip Chee 《GeoJournal》2022,87(1):167-181
GeoJournal - Two phases of study are involved in this research: first, the sales strategies for affordable houses embedded with eco-friendly and smart technology features; and second, the impact of... 相似文献
10.