The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of ...The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of the riser under VIVs are calculated and the mean stresses,the number of stress cycles and amplitudes are determined by the rainflow counting method.The Palmgren-Miner rule for cumulative damage theory with a specified S-N curve is used to estimate the fatigue life of the riser.The corresponding numerical programs numerical simulation of vortex-induced vibrations (NSVIV) which can be used to calculate the VIV response and fatigue life of the riser are compiled.Finally the influences of the riser's parameters such as flexural rigidity,top tension and internal flow velocity on the fatigue life of the riser are analyzed in detail and some conclusions are drawn.展开更多
Genetic structure data of five populations of the Luehea divaricata Mart. ＆ Zucc., forest tree species under development in the Atlantic Forest biome, obtained by microsatellite DNA markers, were used in simulations ...Genetic structure data of five populations of the Luehea divaricata Mart. ＆ Zucc., forest tree species under development in the Atlantic Forest biome, obtained by microsatellite DNA markers, were used in simulations to study their reproductive and ecological pattern. Different selfing and migration rates were tested, using the observed and expected heterozygosity of 0.55 and 0.67, respectively, obtained through the use of microsatellite markers. Closest values were obtained with the use of selfing rates of 0.3 and migration of 0.2. These results suggest the presence of some self-incompatibility system between these species, which reduces, but does not prevent the self-fertilization. The migration rate contributes to a low genetic differentiation between the populations, making the reproductive mode, responsible for the inbreeding observed in the same populations. Authors suggest continuous monitoring of the genetic variability as a guarantee for the persistence of these populations. The study focus on the importance of using computer simulations to investigate ecologic, reproductive and genetic patterns for forestry populations, thus enabling the application of suitable measures for conservation.展开更多
This paper present a simulation study of an evolutionary algorithms, Particle Swarm Optimization PSO algorithm to optimize likelihood function of ARMA（1, 1） model, where maximizing likelihood function is equivalent ...This paper present a simulation study of an evolutionary algorithms, Particle Swarm Optimization PSO algorithm to optimize likelihood function of ARMA（1, 1） model, where maximizing likelihood function is equivalent to maximizing its logarithm, so the objective function ＇obj.fun＇ is maximizing log-likelihood function. Monte Carlo method adapted for implementing and designing the experiments of this simulation. This study including a comparison among three versions of PSO algorithm “Constriction coefficient CCPSO, Inertia weight IWPSO, and Fully Informed FIPSO”, the experiments designed by setting different values of model parameters al, bs sample size n, moreover the parameters of PSO algorithms. MSE used as test statistic to measure the efficiency PSO to estimate model. The results show the ability of PSO to estimate ARMA＇ s parameters, and the minimum values of MSE getting for COPSO.展开更多
许多国家都通过招投标来实现勘探区块的最优化发放。投标公司和招标机构面，临着一项共同的重大挑战，那就是如何估算区块的价值。考虑到投标价格一般是未知储量的估算价值与一个系数的乘积，本文的目的就是计算成功发包区块的未知价值...许多国家都通过招投标来实现勘探区块的最优化发放。投标公司和招标机构面，临着一项共同的重大挑战，那就是如何估算区块的价值。考虑到投标价格一般是未知储量的估算价值与一个系数的乘积，本文的目的就是计算成功发包区块的未知价值的一组代表数据（a set of proxies）。使用复合概率分布模型，通过投标价格系数（bid fraction）的随机模拟估算区块价值。我们使用巴西七轮招标的公开资料验证了这一模型。巴西的七轮招标共向50家公司发放了22个沉积盆地的610个区块，收取的签字定金（现金）达14亿美元。文中只选取巴西坎波斯盆地的招标区块作为研究对象，因为它是巴西最有吸引力的油气勘探区域之一，该盆地的石油产量高达180万桶／日，占巴西全国石油总产量的近80％。模拟结果显示，这种方法可以作为一种辅助性的决策手段。石油公司可以用它来选择投标区块和制定投标策略，而监管机构可以用它来评价招标结果。这种方法适用于全世界不同地区不同含油气盆地的勘探区块的竞争性招标。展开更多
This paper presents the estimation of Chinese emissions of HCFC-22 and CFC-11 in 2009 by an inverse modeling method based on in-situ measurement data from the Shangdianzi Global Atmosphere Watch (GAW) Regional Station...This paper presents the estimation of Chinese emissions of HCFC-22 and CFC-11 in 2009 by an inverse modeling method based on in-situ measurement data from the Shangdianzi Global Atmosphere Watch (GAW) Regional Station (SDZ) and atmospheric transport simulations. After inversion (a-posteriori) estimates of the Chinese emissions in 2009 increased by 6.6% for HCFC-22 from 91.7 (± 83.6) to 98.3 (± 47.4) kt/yr and by 22.5% for CFC-11 from 13 (±12.6) to 15.8 (±7.2) kt/yr compared to an a-priori emission. While the model simulation with a-priori emissions already captured the main features of the observed variability at the measurement site, the model performance (in terms of correlation and mean-square-error) improved using a-posteriori emissions. The inversion reduced the root-mean-square (RMS) error by 4% and 10% for HCFC-22 and CFC-11, respectively.展开更多
The next-generation weather radar(NEXRAD) can generally capture the spatial variability of rainfall fields,but fails to provide accurate depth measurements.A systematic strategy to evaluate the accuracy of radar data ...The next-generation weather radar(NEXRAD) can generally capture the spatial variability of rainfall fields,but fails to provide accurate depth measurements.A systematic strategy to evaluate the accuracy of radar data in depth measurement and its performance in hydrologic model is outlined.Statistical evaluation coefficients are calculated by comparing NEXRAD data with individual raingauges as well as subbasin-averaged interpolations,and point-and surface-average factors are introduced to revise radar data successively.Hydrologic simulations are then performed with a distributed hydrologic model,called basin pollution calculation center(BPCC) with both raingauge observations and revised NEXRAD estimates inputs.The BPCC model is applied to Clear Creek Watershed,IA,USA,on an hourly scale,and the calibration and validation parameters are semi-automatically optimized to improve manual calibration shortcomings.Results show that hydrographs generated from both gauge and NEXRAD are in good agreement with observed flow hydrographs.Coefficient statistics reveal that NEXRAD contributes to model performance,indicating that NEXRAD data has the potential to be used as an alternative source of precipitation data and improve the accuracy of hydrologic simulations.展开更多
基金supported by the High Technology Research and Development Program of China (863 Program,Grant Nos.2006AA09Z356 and 2007AA09Z313)
文摘The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of the riser under VIVs are calculated and the mean stresses,the number of stress cycles and amplitudes are determined by the rainflow counting method.The Palmgren-Miner rule for cumulative damage theory with a specified S-N curve is used to estimate the fatigue life of the riser.The corresponding numerical programs numerical simulation of vortex-induced vibrations (NSVIV) which can be used to calculate the VIV response and fatigue life of the riser are compiled.Finally the influences of the riser's parameters such as flexural rigidity,top tension and internal flow velocity on the fatigue life of the riser are analyzed in detail and some conclusions are drawn.
文摘Genetic structure data of five populations of the Luehea divaricata Mart. ＆ Zucc., forest tree species under development in the Atlantic Forest biome, obtained by microsatellite DNA markers, were used in simulations to study their reproductive and ecological pattern. Different selfing and migration rates were tested, using the observed and expected heterozygosity of 0.55 and 0.67, respectively, obtained through the use of microsatellite markers. Closest values were obtained with the use of selfing rates of 0.3 and migration of 0.2. These results suggest the presence of some self-incompatibility system between these species, which reduces, but does not prevent the self-fertilization. The migration rate contributes to a low genetic differentiation between the populations, making the reproductive mode, responsible for the inbreeding observed in the same populations. Authors suggest continuous monitoring of the genetic variability as a guarantee for the persistence of these populations. The study focus on the importance of using computer simulations to investigate ecologic, reproductive and genetic patterns for forestry populations, thus enabling the application of suitable measures for conservation.
文摘This paper present a simulation study of an evolutionary algorithms, Particle Swarm Optimization PSO algorithm to optimize likelihood function of ARMA（1, 1） model, where maximizing likelihood function is equivalent to maximizing its logarithm, so the objective function ＇obj.fun＇ is maximizing log-likelihood function. Monte Carlo method adapted for implementing and designing the experiments of this simulation. This study including a comparison among three versions of PSO algorithm “Constriction coefficient CCPSO, Inertia weight IWPSO, and Fully Informed FIPSO”, the experiments designed by setting different values of model parameters al, bs sample size n, moreover the parameters of PSO algorithms. MSE used as test statistic to measure the efficiency PSO to estimate model. The results show the ability of PSO to estimate ARMA＇ s parameters, and the minimum values of MSE getting for COPSO.
文摘许多国家都通过招投标来实现勘探区块的最优化发放。投标公司和招标机构面，临着一项共同的重大挑战，那就是如何估算区块的价值。考虑到投标价格一般是未知储量的估算价值与一个系数的乘积，本文的目的就是计算成功发包区块的未知价值的一组代表数据（a set of proxies）。使用复合概率分布模型，通过投标价格系数（bid fraction）的随机模拟估算区块价值。我们使用巴西七轮招标的公开资料验证了这一模型。巴西的七轮招标共向50家公司发放了22个沉积盆地的610个区块，收取的签字定金（现金）达14亿美元。文中只选取巴西坎波斯盆地的招标区块作为研究对象，因为它是巴西最有吸引力的油气勘探区域之一，该盆地的石油产量高达180万桶／日，占巴西全国石油总产量的近80％。模拟结果显示，这种方法可以作为一种辅助性的决策手段。石油公司可以用它来选择投标区块和制定投标策略，而监管机构可以用它来评价招标结果。这种方法适用于全世界不同地区不同含油气盆地的勘探区块的竞争性招标。
基金supported by the National Natural Science Foundation of China (41030107)Chinese Ministry of Science and Technology(2010CB950601)+2 种基金EUS & T Cooperative Project 2SMONGS&T Cooperation Project of the MOST and Eu (1015)CAMS Fundamental Research Funds-General Program (2010Y003)
文摘This paper presents the estimation of Chinese emissions of HCFC-22 and CFC-11 in 2009 by an inverse modeling method based on in-situ measurement data from the Shangdianzi Global Atmosphere Watch (GAW) Regional Station (SDZ) and atmospheric transport simulations. After inversion (a-posteriori) estimates of the Chinese emissions in 2009 increased by 6.6% for HCFC-22 from 91.7 (± 83.6) to 98.3 (± 47.4) kt/yr and by 22.5% for CFC-11 from 13 (±12.6) to 15.8 (±7.2) kt/yr compared to an a-priori emission. While the model simulation with a-priori emissions already captured the main features of the observed variability at the measurement site, the model performance (in terms of correlation and mean-square-error) improved using a-posteriori emissions. The inversion reduced the root-mean-square (RMS) error by 4% and 10% for HCFC-22 and CFC-11, respectively.
基金supported by the National Basic Research Program of China ("973" Project) (Grant No. 2007CB407202)
文摘The next-generation weather radar(NEXRAD) can generally capture the spatial variability of rainfall fields,but fails to provide accurate depth measurements.A systematic strategy to evaluate the accuracy of radar data in depth measurement and its performance in hydrologic model is outlined.Statistical evaluation coefficients are calculated by comparing NEXRAD data with individual raingauges as well as subbasin-averaged interpolations,and point-and surface-average factors are introduced to revise radar data successively.Hydrologic simulations are then performed with a distributed hydrologic model,called basin pollution calculation center(BPCC) with both raingauge observations and revised NEXRAD estimates inputs.The BPCC model is applied to Clear Creek Watershed,IA,USA,on an hourly scale,and the calibration and validation parameters are semi-automatically optimized to improve manual calibration shortcomings.Results show that hydrographs generated from both gauge and NEXRAD are in good agreement with observed flow hydrographs.Coefficient statistics reveal that NEXRAD contributes to model performance,indicating that NEXRAD data has the potential to be used as an alternative source of precipitation data and improve the accuracy of hydrologic simulations.
