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s=1/2xxz反铁磁链的Spin-Peierls相变研究
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作者 江学范 《常熟高专学报》 2000年第4期24-28,共5页
应用玻色化的自洽微扰论方法 ,给出了s =12 xxz反铁磁链的Spin-Peierls系统的基态能量和准粒子元激发能谱的解析近似式 。
关键词 反铁磁铁相变 自洽微扰论 晶格畸变
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健康效用值测量中的映射法及其相关模型概述 被引量:6
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作者 孙园园 余正 李洪超 《中国药房》 CAS 北大核心 2017年第29期4045-4049,共5页
目的:为将非效用量表测量结果转化为健康效用值提供方法学参考。方法:查阅国内外文献,总结健康效用值测量中的映射法及其相关模型,并以生存质量量表测量结果转换成欧洲五维健康量表效用值为例,介绍各模型在概率映射中的应用。结果:映射... 目的:为将非效用量表测量结果转化为健康效用值提供方法学参考。方法:查阅国内外文献,总结健康效用值测量中的映射法及其相关模型,并以生存质量量表测量结果转换成欧洲五维健康量表效用值为例,介绍各模型在概率映射中的应用。结果:映射法可通过建立非效用量表和效用量表之间的映射关系,进而得到健康效用值;其常用模型包括普通最小二乘法(OLS)模型、最小绝对离差法(CLAD)模型、Tobit模型、多元Logistic回归(MNL)模型、贝叶斯网络(BN)模型等。其中,OLS模型相对简单,预测效度较好,但会受到天花板效应的限制;Tobit模型不受天花板或地板效应的限制,当误差项满足方差齐性及正态性时,其预测结果优于OLS模型;CLAD模型可用于误差项非方差齐性不适用Tobit模型的情况;MNL模型先通过回归分析确定一种健康状态,再确定其效用值;BN模型预测效度较好,且不涉及计量经济学中的诸多假设和限制条件,但其构建过程受领域专家的影响较大。使用MNL或BN模式计算健康效用值的方法主要有蒙特卡洛模拟法、期望效用值法和最大可能概率法等。利用拟合优度、调整拟合优度、平均误差、均方误差、平均绝对误差等指标进行模型性能评价,可选出最优模型,进而计算健康效用值。结论:由于各映射模型各有优缺点,在临床研究中需要根据实际情况选择不同的映射模型。 展开更多
关键词 映射法 健康效用值 映射模型 生存质量量表 欧洲五维健康量表
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Application of AERMOD on near future air quality simulation under the latest national emission control policy of China: A case study on an industrial city 被引量:8
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作者 Jieyun Ma Honghong Yi +3 位作者 Xiaolong Tang Yan Zhang Ying Xiang Li Pu 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2013年第8期1608-1617,共10页
Air quality model can be an adequate tool for future air quality prediction, also atmospheric observations supporting and emission control strategies responders. The influence of emission control policy (emission red... Air quality model can be an adequate tool for future air quality prediction, also atmospheric observations supporting and emission control strategies responders. The influence of emission control policy (emission reduction targets in the national "China's 12th Five-Year Plan (2011-2015)") on the air quality in the near future over an important industrial city of China, Xuanwei in Yunnan Province, was studied by applying the AERMOD modeling system. First, our analysis demonstrated that the AERMOD modeling system could be used in the air quality simulation in the near future for SO2 and NOx under average meteorology but not for PM10. Second, after evaluating the simulation results in 2008 and 2015, ambient concentration of SO2, NOx and PM10 (only 2008) were all centered in the middle of simulation area where the emission sources concentrated, and it is probably because the air pollutions were source oriented. Last but not least, a better air quality condition will happen under the hypothesis that the average meteorological data can be used in near future simulation. However, there are still heavy polluted areas where ambient concentrations will exceed the air quality standard in near future. In spatial allocation, reduction effect of SO2 is more significant than NOx in 2015 as the contribution of SO2 from industry is more than NOx. These results inspired the regulatory applications of AERMOD modeling system in evaluating environmental pollutant control policy 展开更多
关键词 the China’s 12th Five-Year Plan (2011–2015) AERMOD modeling system industry point source
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