A cautious projection BFGS method is proposed for solving nonconvex unconstrained optimization problems.The global convergence of this method as well as a stronger general convergence result can be proven without a gr...A cautious projection BFGS method is proposed for solving nonconvex unconstrained optimization problems.The global convergence of this method as well as a stronger general convergence result can be proven without a gradient Lipschitz continuity assumption,which is more in line with the actual problems than the existing modified BFGS methods and the traditional BFGS method.Under some additional conditions,the method presented has a superlinear convergence rate,which can be regarded as an extension and supplement of BFGS-type methods with the projection technique.Finally,the effectiveness and application prospects of the proposed method are verified by numerical experiments.展开更多
Mixed traffic consisting of cars and bicycles is a typical pattern of urban traffic in China. To study the impact of bicycles on traffic performance, a microscopic simulating model based on the principle of cautious d...Mixed traffic consisting of cars and bicycles is a typical pattern of urban traffic in China. To study the impact of bicycles on traffic performance, a microscopic simulating model based on the principle of cautious driving and collision free was proposed. The interaction between cars and bicycles were described by lateral friction and overlapping driving. The dynamical features of speed and time-headway were investigated by numerical simulations. The results show that bicycles have a significant impact on travel speed and time-headway. The effect of bicycles can cause different results in the free flow phase and congestion phase respectively. The results also indicate the necessity to mitigate the interaction between motorized vehicles and non-motorized vehicles.展开更多
An efficient SQP algorithm for solving nonlinear degenerate problems is proposed in the paper. At each iteration of the algorithm, a quadratic programming subproblem, which is always feasible by introducing a slack va...An efficient SQP algorithm for solving nonlinear degenerate problems is proposed in the paper. At each iteration of the algorithm, a quadratic programming subproblem, which is always feasible by introducing a slack variable, is solved to obtain a search direction. The steplength along this direction is computed by employing the 1∞ exact penalty function through Armijo-type line search scheme. The algorithm is proved to be convergent globally under mild conditions.展开更多
In this paper, we present a theoretical analysis on stability and convergence of the cautious control, which has advantages over the traditional certainty equivalence adaptive control, since it takes the parameter est...In this paper, we present a theoretical analysis on stability and convergence of the cautious control, which has advantages over the traditional certainty equivalence adaptive control, since it takes the parameter estimation error into account in the design, and is also one-step-ahead optimal in the mean square sense under Gaussian assumptions.展开更多
Aims Observer error is an unavoidable aspect of vegetation surveys involving human observers.We quantified four components of interobserver error associated with long-term monitoring of prairie vegetation:overlooking ...Aims Observer error is an unavoidable aspect of vegetation surveys involving human observers.We quantified four components of interobserver error associated with long-term monitoring of prairie vegetation:overlooking error,misidentification error,cautious error and estimation error.We also evaluated the association of plot size with pseudoturnover due to observer error,and how documented pseudochanges in species composition and abundance compared with recorded changes in the vegetation over a 4-year interval.Methods This study was conducted at Tallgrass Prairie National Preserve,Kansas.Monitoring sites contained 10 plots;each plot consisted of a series of four nested frames(0.01,0.1,1 and 10 m^(2)).The herbaceous species present were recorded in each of the nested frames,and foliar cover was visually estimated within seven cover categories at the 10 m^(2)spatial scale only.Three hundred total plots(30 sites)were surveyed,and 28 plots selected at random were resurveyed to assess observer error.Four surveyors worked in teams of two.Important Findings At the 10 m^(2)spatial scale,pseudoturnover resulting from overlooking error averaged 18.6%,compared with 1.4%resulting from misidentification error and 0.6%resulting from cautious error.Pseudoturnover resulting from overlooking error increased as plot size decreased,although relocation error likely played a role.Recorded change in species composition over a 4-year interval(excluding potential misidentification error and cautious error)was 30.7%,which encompassed both pseudoturnover due to overlooking error and actual change.Given a documented overlooking error rate of 18.6%,this suggests the actual change for the 4-year period was only 12.1%.For estimation error,26.2%of the time a different cover class was recorded.Over the 4-year interval,46.9%of all records revealed different cover classes,suggesting that 56%of the records of change in cover between the two time periods were due to observer error.展开更多
欧元伴随1999年新年钟声而诞生。她在世界各地的国际外汇交易市场的亮相的消息成为新闻传媒的一个亮点。1999年1月4日上海一家大报的头条新闻是:上海金融界“欧元总动员”。打开1999年1月5日清晨的Internet,首先映入眼帘的消息是:欧元...欧元伴随1999年新年钟声而诞生。她在世界各地的国际外汇交易市场的亮相的消息成为新闻传媒的一个亮点。1999年1月4日上海一家大报的头条新闻是:上海金融界“欧元总动员”。打开1999年1月5日清晨的Internet,首先映入眼帘的消息是:欧元闪亮登场,美元不见惊慌。这篇文章写得精彩,信息丰富。美元,在本文称为“the worl’s most sought-after reserve currency”,对于欧元的面世,自然别有一番滋味在心头。这种微妙的心情在本文表现得淋漓尽致。当然,在种种复杂的情绪中,文章披露的两条倒也不无道理: 1....Europe might turn its back on(不理睬)Problems elsewhere in theworld economy as it concentrates on making its unprecedented currency unionwork. 2....the focus on the euro must not deflect(使偏斜)from structuralreforms to reduce sky-high unemployment rates m much of Europe. 美国人的担心(The euro will start to challenge the dollar as the world’slead currency)是否会成为现实,何时会成为现实。国人尚须拭目以待。现在就下结论,未免为时过早。 此外,本文有几处措辞极为成功,读者不妨细读慢赏。】展开更多
基金supported by the Guangxi Science and Technology base and Talent Project(AD22080047)the National Natural Science Foundation of Guangxi Province(2023GXNFSBA 026063)+1 种基金the Innovation Funds of Chinese University(2021BCF03001)the special foundation for Guangxi Ba Gui Scholars.
文摘A cautious projection BFGS method is proposed for solving nonconvex unconstrained optimization problems.The global convergence of this method as well as a stronger general convergence result can be proven without a gradient Lipschitz continuity assumption,which is more in line with the actual problems than the existing modified BFGS methods and the traditional BFGS method.Under some additional conditions,the method presented has a superlinear convergence rate,which can be regarded as an extension and supplement of BFGS-type methods with the projection technique.Finally,the effectiveness and application prospects of the proposed method are verified by numerical experiments.
基金Supported by the Programme of Introducing Talents of Discipline to Universities(B12022)
文摘Mixed traffic consisting of cars and bicycles is a typical pattern of urban traffic in China. To study the impact of bicycles on traffic performance, a microscopic simulating model based on the principle of cautious driving and collision free was proposed. The interaction between cars and bicycles were described by lateral friction and overlapping driving. The dynamical features of speed and time-headway were investigated by numerical simulations. The results show that bicycles have a significant impact on travel speed and time-headway. The effect of bicycles can cause different results in the free flow phase and congestion phase respectively. The results also indicate the necessity to mitigate the interaction between motorized vehicles and non-motorized vehicles.
基金Supported by the National Natural Science Foundation of China(No.10671060)the Specialized Research Found for the Doctoral Program of Higher Education(No.20030532006)
文摘An efficient SQP algorithm for solving nonlinear degenerate problems is proposed in the paper. At each iteration of the algorithm, a quadratic programming subproblem, which is always feasible by introducing a slack variable, is solved to obtain a search direction. The steplength along this direction is computed by employing the 1∞ exact penalty function through Armijo-type line search scheme. The algorithm is proved to be convergent globally under mild conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.60221301 and 60334040)the Basic Research Funds of Beijing Institute of Technology.
文摘In this paper, we present a theoretical analysis on stability and convergence of the cautious control, which has advantages over the traditional certainty equivalence adaptive control, since it takes the parameter estimation error into account in the design, and is also one-step-ahead optimal in the mean square sense under Gaussian assumptions.
基金funded by the National Park Service Inventory and Monitoring Program.
文摘Aims Observer error is an unavoidable aspect of vegetation surveys involving human observers.We quantified four components of interobserver error associated with long-term monitoring of prairie vegetation:overlooking error,misidentification error,cautious error and estimation error.We also evaluated the association of plot size with pseudoturnover due to observer error,and how documented pseudochanges in species composition and abundance compared with recorded changes in the vegetation over a 4-year interval.Methods This study was conducted at Tallgrass Prairie National Preserve,Kansas.Monitoring sites contained 10 plots;each plot consisted of a series of four nested frames(0.01,0.1,1 and 10 m^(2)).The herbaceous species present were recorded in each of the nested frames,and foliar cover was visually estimated within seven cover categories at the 10 m^(2)spatial scale only.Three hundred total plots(30 sites)were surveyed,and 28 plots selected at random were resurveyed to assess observer error.Four surveyors worked in teams of two.Important Findings At the 10 m^(2)spatial scale,pseudoturnover resulting from overlooking error averaged 18.6%,compared with 1.4%resulting from misidentification error and 0.6%resulting from cautious error.Pseudoturnover resulting from overlooking error increased as plot size decreased,although relocation error likely played a role.Recorded change in species composition over a 4-year interval(excluding potential misidentification error and cautious error)was 30.7%,which encompassed both pseudoturnover due to overlooking error and actual change.Given a documented overlooking error rate of 18.6%,this suggests the actual change for the 4-year period was only 12.1%.For estimation error,26.2%of the time a different cover class was recorded.Over the 4-year interval,46.9%of all records revealed different cover classes,suggesting that 56%of the records of change in cover between the two time periods were due to observer error.
文摘欧元伴随1999年新年钟声而诞生。她在世界各地的国际外汇交易市场的亮相的消息成为新闻传媒的一个亮点。1999年1月4日上海一家大报的头条新闻是:上海金融界“欧元总动员”。打开1999年1月5日清晨的Internet,首先映入眼帘的消息是:欧元闪亮登场,美元不见惊慌。这篇文章写得精彩,信息丰富。美元,在本文称为“the worl’s most sought-after reserve currency”,对于欧元的面世,自然别有一番滋味在心头。这种微妙的心情在本文表现得淋漓尽致。当然,在种种复杂的情绪中,文章披露的两条倒也不无道理: 1....Europe might turn its back on(不理睬)Problems elsewhere in theworld economy as it concentrates on making its unprecedented currency unionwork. 2....the focus on the euro must not deflect(使偏斜)from structuralreforms to reduce sky-high unemployment rates m much of Europe. 美国人的担心(The euro will start to challenge the dollar as the world’slead currency)是否会成为现实,何时会成为现实。国人尚须拭目以待。现在就下结论,未免为时过早。 此外,本文有几处措辞极为成功,读者不妨细读慢赏。】
