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211.
212.
R. A. Broucke 《Celestial Mechanics and Dynamical Astronomy》1994,58(2):99-123
We describe a collection of results obtained by numerical integration of orbits in the main problem of artificial satellite theory (theJ
2 problem). The periodic orbits have been classified according to their stability and the Poincaré surfaces of section computed for different values ofJ
2 andH (whereH is thez-component of angular momentum). The problem was scaled down to a fixed value (–1/2) of the energy constant. It is found that the pseudo-circular periodic solution plays a fundamental role. They are the equivalent of the Poincaré first-kind solutions in the three-body problem. The integration of the variational equations shows that these pseudo-circular solutions are stable, except in a very narrow band near the critical inclincation. This results in a sequence of bifurcations near the critical inclination, refining therefore some known results on the critical inclination, for instance by Izsak (1963), Jupp (1975, 1980) and Cushman (1983). We also verify that the double pitchfork bifurcation around the critical inclination exists for large values ofJ
2, as large as |J
2|=0.2. Other secondary (higher-order) bifurcations are also described. The equations of motion were integrated in rotating meridian coordinates. 相似文献
213.
Jose-Manuel Ferrándiz Maria-Eugenia Sansaturio Joseph R. Pojman 《Celestial Mechanics and Dynamical Astronomy》1992,53(4):347-363
The set of canonical redundant variables previously introduced by the first author is derived from Cartesian coordinates in a simplified form which allows the reduction of the Kepler problem to four harmonic oscillators with unit frequency. The coordinates are defined to be the direction cosines of the position of the particle along with the inverse of its distance. True anomaly is the new independent variable. The behavior of this new transformation is studied when applied to the numerical integrations of the main problem in satellite theory. In particular, computation time and accuracy of orbits in the new variables are compared with those in K-S and Cartesian variables. It is noteworthy that for high eccentricities the new variables require the least computation time for comparable accuracy, regardless of the integration scheme. 相似文献
214.
大珠母贝人工苗工厂化分组标粗;室内养殖54d,贝苗平均壳高从入池时6.61mm增长至13.08mm,最大为14.25mm,平均成活率31.9%,最高达49.8%。试验结果初步表明:1.大珠母贝岸上室内工厂化养殖不但可行,而且也将是解决当前海上养成困境的一条出路;2.发现自然海区中也存在饥饿死亡现象及死亡潜伏期,反映出海上养殖高死亡率的复杂性;3.人工配合饲料的应用显著提高了贝苗的增长率和成活率,显示出广阔的商业价值。 相似文献
215.
The analysis of ground vibrations induced by bench blasting at Akyol quarry and practical blasting charts 总被引:3,自引:0,他引:3
Umit Ozer Ali Kahriman Mehmet Aksoy Deniz Adiguzel Abdulkadir Karadogan 《Environmental Geology》2008,54(4):737-743
Ground vibrations arising from excavation with blasting is one of the fundamental problems in the mining industry. Therefore,
the prediction of ground vibration components plays an important role in the minimization of environmental complaints. In
this study, 582 events were recorded during limestone production at a quarry (Akyol Quarry) during a period of time. The blasting
parameters of these shots were also carefully recorded. During the statistical analysis of the collected data, three predictor
equations proposed by the United States Bureau of Mines (USBM), Ambraseys–Hendron and Langefors–Kihlstrom were used to establish
a relationship between peak particle velocity and scaled distance described by these prediction equations. As a result of
this analysis, the most powerful relationship was determined and proposed to be used in this site. And also, this equation
was used in the derivation of the practical blasting charts specific to this site as a practical way of predicting the peak
particle velocity and maximum charge amount per delay for future blasting. 相似文献
216.
The effectiveness of artificial recharge in combating seawater intrusion in Salalah coastal aquifer, Oman 总被引:1,自引:0,他引:1
Mahaad I. Shammas 《Environmental Geology》2008,55(1):191-204
The Salalah central sewage treatment plant has been designed to treat 20,000 m3/day at the first stage and two further stages to double the initial capacity. The plant currently (2005) treats more than
15,000 m3/day effluents to a tertiary level, and after chlorination phase, the effluents are recharged into tube wells in a line parallel
to the coast. The process aims to help stabilize the seawater interface and a part to be recovered from hand-dug wells/boreholes
further inland and downstream. A three-dimensional flow and solute advection transport model was developed to assess the effectiveness
of the proposed recharge scheme and to track the solute transport with respect to the design system. The advection transport
model predicted that in 2020 the maximum pathlines of the injection fluids would reach the abstraction wells that are located
600 m, southward of the injection bores in about 1-year travel time in the case of the no-management interference and more
than that southward under management interference. The developed flow predicted the wedge of the saline intrusion in 2019
is tracked up to 2.7 and 3.4 km from the shoreline with the injection and without the injection, respectively under constant
underflow. The injection scheme is effective in pushing back the saline zone front by 700 m. This study argues that the treated
wastewater would help to increase the water levels at the vicinity of the injection line and to reduce the influence of saline
inflows from the coast. The reclaimed sewage recharge scheme is examined in the case of the Salalah coastal aquifer using
groundwater simulation, which can also be applied to other regions with similar conditions. 相似文献
217.
The aim of this study is to estimate the capabilities of forecasting the yield of wheat using an artificial neural network combined with multi-temporal satellite data acquired at high spatial resolution throughout the agricultural season in the optical and/or microwave domains. Reflectance (acquired by Formosat-2, and Spot 4–5 in the green, red, and near infrared wavelength) and multi-configuration backscattering coefficients (acquired by TerraSAR-X and Radarsat-2 in the X- and C-bands, at co- (abbreviated HH and VV) and cross-polarization states (abbreviated HV and VH)) constitute the input variable of the artificial neural networks, which are trained and validated on the successively acquired images, providing yield forecast in near real-time conditions. The study is based on data collected over 32 fields of wheat distributed over a study area located in southwestern France, near Toulouse. Among the tested sensor configurations, several satellite data appear useful for the yield forecasting throughout the agricultural season (showing coefficient of determination (R2) larger than 0.60 and a root mean square error (RMSE) lower than 9.1 quintals by hectare (q ha−1)): CVH, CHV, or the combined used of XHH and CHH, CHH and CHV, or green reflectance and CHH. Nevertheless, the best accurate forecast (R2 = 0.76 and RMSE = 7.0 q ha−1) is obtained longtime before the harvest (on day 98, during the elongation of stems) using the combination of co- and cross-polarized backscattering coefficients acquired in the C-band (CVV and CVH). These results highlight the high interest of using synthetic aperture radar (SAR) data instead of optical ones to early forecast the yield before the harvest of wheat. 相似文献
218.
Simultaneously simulate vertical and horizontal expansions of a future urban landscape: a case study in Wuhan,Central China 总被引:1,自引:0,他引:1
Qingsong He Chen Zeng Yin Chaohui Ronghui Tan 《International journal of geographical information science》2017,31(10):1907-1928
While there are extensive studies of urban 2D forms, research on the varying geometric features and spatial distribution patterns of urban 3D spaces is comparatively rare. In this paper, we propose a coupled model, known as BPANN-CBRSortCA, which is based on a back propagation artificial neural network (BPANN) and case-based reasoning technology with sort cellular automaton (CBRSortCA) to simulate future urban building heights and their spatial distribution. BPANN–CBRSortCA uses BPANN to predict the vertical extrusion of building heights and uses CBRSortCA to simulate horizontal urban expansion. The BPANN–CBRSortCA model is innovative because of its capabilities to simultaneously project urban growth in the vertical and horizontal dimensions. The proposed model also overcomes the limitations of the traditional cellular automata models that cannot simulate ‘diffused’ urban expansion. This research used Wuhan City as a case study to simulate vertical and horizontal urban expansion from 2015 to 2025. The results showed the following: (1) in the next 10 years, new build-up will mainly appear along the edge of Hongshan and Hanyang Districts or will occupy bare land in the form of ‘filling’ and (2) the tallest buildings will be mainly located to the south of East Lake in Hongshan District and on undeveloped land within the city. These simulation results can provide a reference for future urban planning. 相似文献
219.
神经网络模型预报湖北汛期降水量的应用研究 总被引:18,自引:1,他引:18
使用人工神经网络方法建立了湖北省汛期 (6~ 8月 )总降水量的短期气候预测模型 ,该神经网络模型的输入是汛期前期 (2~ 4月 )的北半球月平均 5 0 0 h Pa高度场、海平面气压场和太平洋海温场的扩展自然正交展开 (EEOF)的前几个主要模态的时间系数 ,输出了湖北汛期降水场的自然正交展开 (EOF)的前 2个主要模态的时间系数。41 a历史资料的交叉检验表明 :样本试验的预报技巧评分平均为 0 .2 4 6 ,虽然该模型对各年的预报效果仍存在一定的不稳定性 ,但它可为湖北汛期降水的短期气候预测提供一种具有明显统计预报正技巧的预报方法 相似文献
220.