基于一维数据逐段均匀条件下的参考分布研究

聚类分析中一个重要的问题是估计聚类数,GS方法通过参考分布对聚类数进行合理的估计,解决了其他聚类方法无法对应分为一类的数据进行分类的问题,具有更好的分类效果;目前已通过理论证明得出,在分布为对数凹且一维情况下,GS方法的参考分布为均匀分布,而有关其在其他条件下的参考分布研究较少;针对这一情况,提出解决一维且逐段均匀条件下GS方法的参考分布问题,以类内平方和为评价标准,通过拉格朗日乘数法求解与问题等价的优化问题,理论证出条件下总体均匀分布是类内平方和最大的情况,进而得出对于一维数据,逐段均匀条件下的参考分布仍为均匀分布的结论。     

Doubling Fock空间之间的正Toeplitz算子

设F~p(φ)为复平面C上的加权Fock空间,其中φ为次调和函数,ΔφdA为doubling测度.本文利用均值函数与t-Berezin变换刻画了F~p(φ)(0p∞)与F~∞(φ)之间具有正测度符号的Toeplitz算子T_μ的有界性和紧性,拓展了已有结果.     

The material theory of induction and the epistemology of thought experiments

John D. Norton is responsible for a number of influential views in contemporary philosophy of science. This paper will discuss two of them. The material theory of induction claims that inductive arguments are ultimately justified by their material features, not their formal features. Thus, while a deductive argument can be valid irrespective of the content of the propositions that make up the argument, an inductive argument about, say, apples, will be justified (or not) depending on facts about apples. The argument view of thought experiments claims that thought experiments are arguments, and that they function epistemically however arguments do. These two views have generated a great deal of discussion, although there hasn't been much written about their combination. I argue that despite some interesting harmonies, there is a serious tension between them. I consider several options for easing this tension, before suggesting a set of changes to the argument view that I take to be consistent with Norton's fundamental philosophical commitments, and which retain what seems intuitively correct about the argument view. These changes require that we move away from a unitary epistemology of thought experiments and towards a more pluralist position.     

Correcting the January optimism effect

Each month, various professional forecasters give forecasts for next year's real gross domestic product (GDP) growth and unemployment. January is a special month, when the forecast horizon moves to the following calendar year. Instead of deleting the January data when analyzing forecast updates, I propose a periodic version of a test regression for weak-form efficiency. An application of this periodic model for many forecasts across a range of countries shows that in January GDP forecast updates are positive, whereas the forecast updates for unemployment are negative. I document that this January optimism about the new calendar year is detrimental to forecast accuracy. To empirically analyze Okun's law, I also propose a periodic test regression, and its application provides more support for this law.     

Theoretical and experimental design of Pt-Co(OH)_2 electrocatalyst for efficient HER performance in alkaline solution

Design efficient electrocatalysts become significant for the hydrogen evolution reaction (HER) in alkaline solution.Here,the HER performance on Pt-Co(OH)2 has been investigated by using DFT calculations.Compared with pure Pt,the Pt-Co(OH)2 shows excellent hydrogen binding energy (-0.29 eV) and hydrogen adsorption free energy (0.02 eV).More strikingly,the water dissociation process on Pt-Co(OH)2 is an exothermic reaction while that of Pt is an endothermic reaction,demonstrating that the Pt-Co(OH)_2 is an excellent catalyst for HER in alkaline medium.Then the two-step electrodepositions was used to fabricate Pt-Co(OH)2 on the carbon paper (CP).The Pt-Co(OH)_2/CP shows the lowest overpotential of only 37.6 mV at a current density of 10 mA cm~(-2) in 0.1M KOH,the smallest Tafel slope of58 mV dec~(-1) and the good stability for 20000s without obvious degradation.     

Brinbaum-Sauders分布的极值收敛速度

主要讨论了Brinbaum-Sauders分布的尾部特征,得到了最大值分布的渐进展开.