基于弹性网惩罚的复合分位数回归估计

针对高维数据的建模分析问题,提出一种基于弹性网络法和复合分位数回归相结合的稳健估计方法。 在该 估计方法中,所提出的模型能够有效进行变量选择与系数压缩,并处理数据间的多重共线性与群组效应问题,在大 数据时代下具有较广的适应性。 同时,与已有的惩罚最小二乘估计和惩罚分位数回归估计相比,该估计方法不仅 放宽了对模型误差项的分布要求,而且综合考虑了多个分位点的损失,在面对离群值或呈现尖峰、厚尾分布数据时 能够保持更强的稳健性和抗干扰性。 在一定条件下,对所构建模型估计的相合性与稀疏性进行了理论分析,结果 表明:所提出的模型能够将不相关的变量完全压缩至零,且估计量和真实系数以趋于 1 的概率相同。 此外,在数值 模拟方面,设置了 5 种误差项分布条件,根据设定的 4 项指标,通过与其他惩罚函数模型以及损失函数模型进行比 较,结果表明新提出的方法具备更好的稳健性与有效性。     

高维惩罚分位数回归及优化算法

针对具有异常值或离群点的高维数据线性回归模型，提出了一种基于误差函数正则化的惩罚分位数回归的新方法，与经典的L₁惩罚方法相比，新方法具有更好的稳健性以及更小的估计偏差和预测误差；为解决分位数损失函数非光滑性与误差函数非凸性所带来的计算挑战，结合迭代再加权L₁算法以及ADMM算法，提出了一种有效的IRWADMM算法，并对回归系数进行了求解.模拟结果表明，与已有的惩罚分位数回归方法相比，新方法在参数估计和变量选择等方面均具有更好的表现.将新方法应用于核黄素基因数据分析，以证实其有效性和可行性.     

正弦余弦算法求解含有异常值的非线性数据拟合

针对非线性数据拟合问题，建立以残差的平方和与绝对值和为目标的最小二乘与最小一乘模型，采用正弦余弦算法计算模型参数.计算结果表明：如果数据的分布是对称且无异常值，则最小二乘得到的结果与最小一乘得到的结果基本一致；如果数据存在异常值，则异常值对最小二乘有着较大的影响，而对最小一乘的影响较小.     

基于调整秩回归的组变量选择

EXP惩罚是一种指数形式的惩罚函数,它近似于L₀惩罚. EXP惩罚最小二乘估计具有模型选择的相合性和渐近正态性.但是,惩罚最小二乘方法对重尾分布和含有异常值的混合分布的效果并不理想.该文考虑回归模型中的变量是以组结构形式存在的,研究基于调整秩回归的EXP型组变量选择,给出了调整秩回归估计的理论性质,并通过数据模拟和实例分析,检验调整秩回归的EXP惩罚的效果,结果表明这种方法具有较好的表现.     

左截断右删失数据下线性模型的加权复合分位数估计及变量选择

在可靠性及生存分析等领域中经常出现左截断右删失数据,即指在某种设定下,样本值不能被完全观测到的数据.左截断右删失数据下线性回归的参数估计方法一般选用加权分位数估计,然而加权分位数估计只考虑了单个分位点的损失,在估计效率方面存在缺陷.为克服这一缺点,针对左截断右删失数据下线性模型的参数估计问题,提出了加权复合分位数估计方法.此外,为识别模型中的非零参数并进行变量选择,建立了基于自适应Lasso的惩罚加权复合分位数估计,并在一定假设条件下,证明了所提估计具有渐近正态性和Oracle性质.数值模拟和实例分析结果表明,本文提出的惩罚加权复合分位数估计具有良好的变量选择性质,并且加权复合分位数估计与加权分位数估计相比,具有更高的估计效率.     

工具变量线性回归模型的指数平方损失估计

在讨论协变量和响应变量关系时,常会遇到内生变量,已有关于内生变量的研究大多是在最小二乘目标函数的框架下讨论,然而该方法不具有稳健性,鉴于此,本文采用指数平方损失估计方法,构造模型中回归系数的稳健估计.为了克服内生变量对估计产生的偏差,利用工具变量消除协变量的内生性,再构造回归系数的指数平方损失估计;针对指数平方损失目标...     

基于最小距离法的稳健群组变量选择

在研究存在异常值的logistic回归模型时,发现如果使用极大似然估计(MLE)方法进行参数估计,那么异常值引起的偏差不是造成参数估计过大而是导致参数向量内爆即参数向量收缩为零向量,此时如果进行群组变量选择很可能会忽略一些重要变量.因此针对具有组结构的logistic回归模型,为处理解释变量存在异常值时的群组变量选择问题,将基于最小距离法的稳健估计(L₂E)方法与已有的3种群组变量选择方法和3种双层变量选择方法结合,在此基础上利用Majorization-Minimization(MM)算法对目标函数进行求解.通过数值模拟比较了基于L₂E方法和MLE方法在模型具有组稀疏和双层稀疏的情况下,6种变量选择方法在不同维数下的有限样本表现,结果不仅验证了L₂E方法在存在异常值的logistic回归模型参数估计中的稳健性,而且指出了在这6种变量选择方法中使用Group Bridge方法进行变量选择的准确度更高.     

面向网络数据的Elastic Net回归模型

线性模型作为一种经典的回归模型，具有简洁的表达形式和较强的可解释性。然而，传统的线性模型是基于样本独立假设的，并不能有效地处理网络数据问题。为了有效地表达网络数据之间的关联信息，本文利用网络结构图，构建了包含样本邻近信息的回归模型。进一步，为了合理估计回归模型参数，并提高处理强相关变量数据的能力，本文提出了一种能够有效处理网络数据的Elastic Net回归模型。具体地，该模型由平方损失和Elastic Net正则项组成，其中平方损失项既包含数据的属性变量信息，又包含响应变量的网络结构信息，能够更好地提高模型学习的准确性；Elastic Net正则项不仅可以保证模型的稳定性和稀疏性，而且具有变量分组效应，能够将强相关性变量组全部剔除或保留。最后采用坐标下降和交替迭代算法对目标函数进行求解。在实验过程中，分别采用Scale-free网络、Hub网络以及Erd?s-Renyi网络进行了大量实验，实验结果显示模型的预测误差能够降低到0.006 6,0.010 3,0.009 7，表明了所提模型的有效性。真实数据集上的实验结果也表明Elastic Net模型具有更高的准确性，能够更加有效地适用...     

基于Horseshoe+先验的惩罚置信区域变量选择方法

针对高维稀疏线性回归问题,相关变量的数量远远少于不相关变量.相关变量的变量选择问题对于传统的频率论正则化方法是一大挑战.现有的贝叶斯惩罚置信区域法通过将模型拟合与变量选择分离,在联合后验置信区域内搜索最稀疏解,从而得到稀疏模型解.且该方法在高维变量选择效果上优于常用的变量选择方法.在此基础上,针对高维稀疏模型,将原方法中依赖的共轭正态先验替换成针对"稀疏信号勘测问题"提出的Horseshoe+先验,利用Horseshoe+先验对小系数"重"压缩与大系数几乎零压缩的理论特性,实现对稀疏回归系数的稳健估计.通过数据仿真模拟不同稀疏程度下的高维稀疏线性回归,并将基于Horseshoe+先验的惩罚置信区域法分别与基于正态先验以及Laplace先验的该方法进行比较,结果表明基于Horseshoe+先验的惩罚置信区域法在高维稀疏线性回归问题具有更好的变量选择效果与预测效果.     

基于SCAD正则最小一乘回归问题研究

针对损失函数为最小一乘,惩罚项由基数函数定义的稀疏回归问题,用SCAD(smoothly clipped absolute deviation)罚来连续逼近基数罚,得到一个连续的松弛问题,研究SCAD罚问题与原基数罚问题之间解的等价性。首先,证明了SCAD罚松弛模型的下界性质,并借助此下界性质分析了原问题与松弛问题之间解的等价性,证明了在一定条件下两个问题具有相同的全局最优解以及最优值。此外,证明了松弛模型的局部最优解是原问题的局部最优解并且在局部极小值点处松弛模型与原问题的目标值相等。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the