以安徽省为例,选取城镇常住人口占总人口比例等18项指标,从人口、空间、经济、社会生活四维度构建了城镇化综合水平评价体系,采用熵值赋权法对其综合指数进行了测算;运用对数平均迪氏分解模型(Logarithmic Mean Divisia Index,LMDI),对...以安徽省为例,选取城镇常住人口占总人口比例等18项指标,从人口、空间、经济、社会生活四维度构建了城镇化综合水平评价体系,采用熵值赋权法对其综合指数进行了测算;运用对数平均迪氏分解模型(Logarithmic Mean Divisia Index,LMDI),对城镇化进程引致的耕地减少份额进行了计算;基于经济学边际理论,采用最小二乘回归分析方法,构建了城镇化边际耕地变化率测度模型;借助EXCEL软件,通过作散点图并添加趋势线,采用最佳拟合优度获取曲线及高数极值求导判别方法,测算了城镇化演进对耕地影响最小的极限时刻,结果表明:安徽省城镇化综合指数由1996年的0.0319上升至2012年的0.9945;城镇化进程引致耕地面积减少量2002年后呈降幅态势,契合经济学边际效应递减规律;城镇化边际耕地变化率指数由2002-2003年的1 292 517.63下降至2011-2012年的7 430.35,整体呈下降态势;边际耕地变化率拟合曲线为开口向上U形抛物线,当城镇化综合指数为7.325时,即2022-2023年间,城镇化对耕地影响处极小状态,2023年前,安徽省推进城镇化与耕地保护矛盾较突出。基于研究结果,从依靠产业结构优化升级促进城镇土地集约利用等方面提出了政策建议。该研究成果可为安徽省科学编制土地利用规划及制定协调城镇化演进与耕地保护政策提供参考,也可为同类研究提供借鉴。展开更多
In this article, we propose a class of additive-accelerated means regression models for analyzing recurrent event data. The class includes the proportional means model, the additive rates model, the accelerated failur...In this article, we propose a class of additive-accelerated means regression models for analyzing recurrent event data. The class includes the proportional means model, the additive rates model, the accelerated failure time model, the accelerated rates model and the additive-accelerated rate model as special cases. The new model offers great flexibility in formulating the effects of covariates on the mean functions of counting processes while leaving the stochastic structure completely unspecified. For the inference on the model parameters, estimating equation approaches are derived and asymptotic properties of the proposed estimators are established. In addition, a technique is provided for model checking. The finite-sample behavior of the proposed methods is examined through Monte Carlo simulation studies, and an application to a bladder cancer study is illustrated.展开更多
A new covariate dependent zero-truncated bivariate Poisson model is proposed in this paper employing generalized linear model. A marginal-conditional approach is used to show the bivariate model. The proposed model wi...A new covariate dependent zero-truncated bivariate Poisson model is proposed in this paper employing generalized linear model. A marginal-conditional approach is used to show the bivariate model. The proposed model with estimation procedure and tests for goodness-of-fit and under (or over) dispersion are shown and applied to road safety data. Two correlated outcome variables considered in this study are number of cars involved in an accident and number of casualties for given number of cars.展开更多
Recurrent event data often arises in biomedical studies, and individuals within a cluster might not be independent. We propose a semiparametric additive rates model for clustered recurrent event data, wherein the cova...Recurrent event data often arises in biomedical studies, and individuals within a cluster might not be independent. We propose a semiparametric additive rates model for clustered recurrent event data, wherein the covariates are assumed to add to the unspecified baseline rate. For the inference on the model parameters, estimating equation approaches are developed, and both large and finite sample properties of the proposed estimators are established.展开更多
Recurrent events data with a terminal event （e.g. death） often arise in clinical and observational studies. Most of existing models assume multiplicative covariate effects and model the conditional recurrent event r...Recurrent events data with a terminal event （e.g. death） often arise in clinical and observational studies. Most of existing models assume multiplicative covariate effects and model the conditional recurrent event rate given survival. In this article, we propose a general mSditive-multiplicative rates model for recurrent event data in the presence of a terminal event, where the terminal event stop the further occurrence of recurrent events. Based on the estimating equation approach and the inverse probability weighting technique, we propose two procedures for estimating the regression parameters and the baseline mean function. The asymptotic properties of the resulting estimators are established. In addition, some graphical and numerical procedures are presented for model checking. The finite-sample behavior of the proposed methods is examined through simulation studies, and an application to a bladder cancer study is also illustrated.展开更多
针对比特币的PoW(proof of work)共识机制中资源消耗巨大、系统性能存在瓶颈和“公地悲剧”问题,从博弈论的角度分析了比特币系统后期只有交易费奖励所带来的“公地悲剧”现象,提出了基于门限密码方案的共识机制(a consensus mechanism ...针对比特币的PoW(proof of work)共识机制中资源消耗巨大、系统性能存在瓶颈和“公地悲剧”问题,从博弈论的角度分析了比特币系统后期只有交易费奖励所带来的“公地悲剧”现象,提出了基于门限密码方案的共识机制(a consensus mechanism based on threshold cryptography,TCCM).首先,新共识协议引入了节点保证金的思想,提出了一种基于门限群签名理论的保证金模型.该模型既能够确保保证金的安全,又为节点诚实地记账提供保障.其次,利用门限加密的思想构造了记账权竞价模型来产生区块链记账节点,这能够保证记账权竞价环境的公平性和记账节点产生的随机性.同时,在原有的区块奖励基础上,设计了新的激励机制,使得更多的节点能够参与共识的全过程.最后,安全性和性能分析结果表明,该共识机制既有效地降低了资源消耗,又提高了交易处理效率,使得整个区块链系统变得更加安全可靠.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 10731010, 10971015, 10721101)National Basic Research Program of China(Grant No. 2007CB814902)Key Laboratory of Random Complex Structures and Data Science,Chinese Academy of Sciences (Grant No. 2008DP173182)
文摘In this article, we propose a class of additive-accelerated means regression models for analyzing recurrent event data. The class includes the proportional means model, the additive rates model, the accelerated failure time model, the accelerated rates model and the additive-accelerated rate model as special cases. The new model offers great flexibility in formulating the effects of covariates on the mean functions of counting processes while leaving the stochastic structure completely unspecified. For the inference on the model parameters, estimating equation approaches are derived and asymptotic properties of the proposed estimators are established. In addition, a technique is provided for model checking. The finite-sample behavior of the proposed methods is examined through Monte Carlo simulation studies, and an application to a bladder cancer study is illustrated.
文摘A new covariate dependent zero-truncated bivariate Poisson model is proposed in this paper employing generalized linear model. A marginal-conditional approach is used to show the bivariate model. The proposed model with estimation procedure and tests for goodness-of-fit and under (or over) dispersion are shown and applied to road safety data. Two correlated outcome variables considered in this study are number of cars involved in an accident and number of casualties for given number of cars.
基金supported by International Cooperation Projects (2010DFA31790) of Chinese Ministry of Science and Technologythe fund of Central China Normal University for Ph.D students (No. 2009023)+2 种基金supported by the National Natural Science Foundation of China Grants(No. 10731010, 10971015 and 11021161)the National Basic Research Program of China (973 Program) (No.2007CB814902)Key Laboratory of Random Complex Structures and Data Science, Academy of Mathematics& Systems Science, Chinese Academy of Sciences (No. 2008DP173182)
文摘Recurrent event data often arises in biomedical studies, and individuals within a cluster might not be independent. We propose a semiparametric additive rates model for clustered recurrent event data, wherein the covariates are assumed to add to the unspecified baseline rate. For the inference on the model parameters, estimating equation approaches are developed, and both large and finite sample properties of the proposed estimators are established.
基金Supported by the National Natural Science Foundation of China(No.11371354)Young Elite Program of Beijing(YETP150)Science and Technology Project of Beijing Municipal Education Commission(KM201411232019)
文摘Recurrent events data with a terminal event （e.g. death） often arise in clinical and observational studies. Most of existing models assume multiplicative covariate effects and model the conditional recurrent event rate given survival. In this article, we propose a general mSditive-multiplicative rates model for recurrent event data in the presence of a terminal event, where the terminal event stop the further occurrence of recurrent events. Based on the estimating equation approach and the inverse probability weighting technique, we propose two procedures for estimating the regression parameters and the baseline mean function. The asymptotic properties of the resulting estimators are established. In addition, some graphical and numerical procedures are presented for model checking. The finite-sample behavior of the proposed methods is examined through simulation studies, and an application to a bladder cancer study is also illustrated.
文摘针对比特币的PoW(proof of work)共识机制中资源消耗巨大、系统性能存在瓶颈和“公地悲剧”问题,从博弈论的角度分析了比特币系统后期只有交易费奖励所带来的“公地悲剧”现象,提出了基于门限密码方案的共识机制(a consensus mechanism based on threshold cryptography,TCCM).首先,新共识协议引入了节点保证金的思想,提出了一种基于门限群签名理论的保证金模型.该模型既能够确保保证金的安全,又为节点诚实地记账提供保障.其次,利用门限加密的思想构造了记账权竞价模型来产生区块链记账节点,这能够保证记账权竞价环境的公平性和记账节点产生的随机性.同时,在原有的区块奖励基础上,设计了新的激励机制,使得更多的节点能够参与共识的全过程.最后,安全性和性能分析结果表明,该共识机制既有效地降低了资源消耗,又提高了交易处理效率,使得整个区块链系统变得更加安全可靠.
