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｜上期回顾｜钱荒,又见钱荒。继2008年金融危机后,中国企业钱荒再现。＂钱荒＂并非全是＂现金流＂惹的祸,资金的＂亚健康＂运行,也责无旁贷。＂由于缺乏专业的现金管理能力,多数企业的现金流处于亚健康的运行状态。     

转化思想在初中数学解题中的应用

在初中数学解题中,转化思想是一种重要的数学思维.解题中常见的转化方式有:直接转化、降次转化、换元转化与数形转化.在教学中,教师应注重转化的原则和提问方式,适时渗透转化思想,以帮助学生在解题时恰当运用转化方式.     

2004年全国各地高考及模拟试题评析——化归与转化

"化归与转化"思想是处理数学问题的一种基本策略.转化和化归就是对原问题换一个方式、换一个角度、换一个观点加以考虑,就是在数学研究中,把要解决的问题通过某种转化,再转化,化归为一类已经解决或比较容易解决的问题,从而使问题得到圆满解决的思维方法.2004年全国各地高考及模拟试题中有不少用"化归与转化"这一思想来解决试题.1概念和载体之间的相互转化     

求解混合三角多项式方程组的直接GBQ方法

许多科学与工程领域,我们经常需要求混合三角多项式方程组的全部解.一般来说,混合三角多项式方程组可以通过变量替换及增加二次多项式转化为多项式方程组,进而利用数值方法进行求解,但这种转化会增大问题的规模从而增加计算量.在本文中,我们不将问题转化,考虑利用直接同伦方法求解,并给出基于GBQ方法构造的初始方程组及同伦定理的证明.数值实验结果表明我们构造的直接同伦方法较已有的直接同伦方法更加有效.     

阅读与转化一例

数学中的转化与化归思想,是指在研究和解决有关数学问题时,采用某种手段将问题通过变换使之转化,进而得到解决的一种思想.常见的转化方式有：一般向特殊转化、复杂向简单转化、数形转化、构造转化、类比转化等.能否有意识地运用转化与化归思想解决问题,往往取决于能否发现待解问题中的转化点.     

把四边形向三角形转化的若干技巧

把四边形的有关问题向三角形转化,是处理四边形问题的一种常见策略.一方面是源于二者同属多边形,故可割可补;另一方面,通过转化,集中条件,往往能形成特殊三角形,曲径通幽.本文结合例子说明几种常见转化途径及方法(割、补、移、转、折、借),供读者参考.     

消错逻辑的增加转化词

定义了增加转化词的概念 ,说明了它的研究对象及在消除决策错误中的作用 ,研究了在消错逻辑变换中 ,这个转化词所具有的性质和规律 .     

富氧燃烧对烟气组分影响的数值模拟研究

以4×10~4m~3/h顶烧式常压加热制氢转化炉为研究对象,分析富氧燃烧对烟气组分的影响.采用有限体积法建立制氢转化炉辐射室流体的三维有限元模型,选取合理的数学模型研究了不同富氧工况对制氢转化炉辐射室内及出口处烟气组分的影响规律.研究结果表明:随着助燃空气中含氧量的增加,燃料气燃烧愈加完全,烟气中碳氢化合物(HC)和一氧化碳(CO)的含量降低.当含氧量为32.5%时,制氢转化炉炉膛内富氧燃烧特性明显.研究结果可为富氧燃烧技术在制氢转化炉的工程应用提供理论指导.     

转化与化归思想在解题中的应用

转化有等价转化与不等价转化.等价转化要求转化过程的前因与后果既是充分的,又是必要的,以保证转化后所得的结果为原题的结果;不等价转化其过程则是充分或必要的,这样的转化能给人带来思维的闪光点,找到解决问题的突破口.不等价转化要对所得结论进行必要的修正(如解无理方程转化为解有理方程,要进行验根).     

浅谈化归与转化思想

化归与转化的思想,就是在研究和解决数学问题时采用某种方式,借助某种函数性质、图像、公式或已知条件将问题通过变换加以转化,进而达到解决问题的思想.转化是将数学命题由一种形式转化成另一种形式的变换过程,化归是把待解决的问题通过某种转化过程归结为一类已经解决或比较容易解决的问题.化归与转化思想是中学数学最基本的思想方法,堪称数学思想的精髓,它渗透到了数学教学内容的各个领域和解题过程的各个环节中.转化有等价转化与不等价转化.等价转化后的新问题与原问题实质是一样的,不等价转化则部分改变了原对象的实质,需对所得结论进行必要的修正.     

On redundant weighted voting systems with components having stochastic arrangement increasing lifetimes

As one generalization of the k-out-of-n structure, the weighted voting system has been paid much attention during the past two decades. This paper has a further study on active redundancies allocation to weighted voting reliability systems of components having LWSAI lifetimes. For redundancies with SAI lifetimes, allocating a more reliable redundancy to a weaker and more heavily weighted component is found to produce a more reliable system in the sense of having higher reliability. Also, in the context of redundancies with identically distributed lifetimes, we show that allocating more redundancies to a weaker and more heavily weighted component produces a more reliable system. Some numerical examples are presented to illustrate the main results as well.     

Optimal retirement strategy with a negative wealth constraint

This paper investigates an optimal consumption, portfolio, and retirement time choice problem of an individual with a negative wealth constraint. We obtain analytical results of the optimal consumption, investment, and retirement behaviors and discuss the effect of the negative wealth constraint on the optimal behaviors. We find that, as an individual can borrow more with better credit, she is more likely to retire at a higher wealth level, to consume more, and to invest more in risky assets.     

Wavelet transform associated to the affine group AG m p

This paper considers wavelet transforms associated to the affine group, which is more general than the paper given by R. Murenzi, and it seems more important in mathematical theory and more natural to be used to analyze signals in more than 1-dimension. This work is supported by National Natural Science Foundation of China.     

全要素生产率如何影响我国制造业企业的区位选址决策

新经济地理理论以及新近发展的“‘新’新经济地理理论”认为,高生产率企业通过集聚效应和选择效应存在于规模较大的市场,本文在后者理论框架下考察中国企业区位选址这一被忽视的问题。运用中国1999~2007年297个地级及以上城市100多万家企业的微观数据,采用倾向得分匹配方法克服样本选择性偏误,本文发现:相比低生产率企业组,高生产率企业选址于更大规模的城市。而且,这种选址倾向在不同区域和企业所有制上具有差异表现:相比传统中、西部地区,东部地区高生产率企业选址于大城市的倾向更为明显;相比集体企业,港澳台、外商及私营企业的这种倾向性更为显著,且估计结果显示国有企业选址不受全要素生产率水平的影响。以上发现为我国制造业企业区位选址决策的制定提供了新的思路。     

Global stability and stabilization of more general stochastic nonlinear systems

This paper considers the global stability and stabilization of more general stochastic nonlinear systems. Due to the absence of the conventional assumptions (e.g., Lipschitz condition), the stochastic nonlinear systems under investigation may have more than one weak solution. However, the most associated results are only applicable to the stochastic systems having a unique strong solution, and therefore, it is meaningful to refine and extend the relevant concepts and methods to the more general case. In this paper, the concepts of stochastic stability in the more general sense are first introduced to cover the stochastic nonlinear systems having more than one weak solution. Then, the generalized stochastic Barbashin–Krasovskii theorem and LaSalle theorem are established, which present the criterions of stochastic stability for more general stochastic nonlinear systems. As one of the main contributions in this paper, we rigorously prove the generalized stochastic Barbashin–Krasovskii theorem. Moreover, based on the generalized theorems, the output-feedback and state-feedback stabilization are accomplished respectively for two classes of high-order stochastic nonlinear systems under rather weaker assumptions comparing to the existing literature.     

结构模糊可靠性分析方法的泛灰求解

针对现有的基于区间求解结构模糊可靠度方法的缺陷,提出了一种新的求解结构模糊可靠度方法.该方法利用泛灰数描述与结构基本变量概率分布相关的不确定参数,并将这些泛灰数引入到结构模糊可靠度计算中,得出了较为精确的结构可靠度计算结果.数值算例表明,该方法得到的结构可靠度区间更窄,实现了利用较少的信息量得到较精确的可靠度计算结果,相比传统的结构模糊可靠度计算方法能提供更多、更精确的关于结构安全程度的有用信息.     

Comparison of two alternative approaches to quality STEM teacher preparation: Fast‐track licensure and embedded residency programs

Alternative pathways to teaching licensure were developed to address teacher shortages. These programs differ widely, making it difficult to generalize the effects. This study compares the impact of two alternative licensure programs on the development of fundamental elements of science teacher preparation and persistence. The fast‐track programs include a 6‐month teacher preparation program and a one‐year residency teacher preparation program. The study concluded that licensure type was unassociated with the impact on teaching self‐efficacy, beliefs about teacher‐focused/student‐focused teaching, preferences for inquiry instructional practices, and experiences with student misbehavior. However, the study revealed that licensure type was associated with a number of other variables: residency students had more confidence in their ability to provide quality instruction; preferred inquiry‐based instruction more often; and may be better prepared for the high‐needs classroom. Those in the 6‐month program were more likely to score higher on practical versus theoretical approaches to teaching, and while they had a more realistic idea of how to measure success in the high‐needs classroom, the residency students had more knowledge of educational theory and how to apply it. Findings suggest that more traditionally licensed teachers may be more inclined to use inquiry‐based methods suggested in current reforms.     

The effects of demand uncertainty on channel structure

Motivated by the business practice whereby some manufacturers open their own retail stores despite the existence of more efficient independent retailers, this paper examines the distribution channel choice of competing manufacturers under demand uncertainty and resale price maintenance. We characterize the conditions for the equilibrium channel structures. We find that (1) manufacturers tend to distribute products with more design attributes through their own retail stores, (2) manufacturers with highly substitutable products are more likely to use independent retailers, and (3) at least one manufacturer has more incentive to open its own retail stores when facing an increase of the market size asymmetry.     

受时间限制的运输问题的新算法

针对现实的物品配送过程中存在着各种各样的外界因素会导致销售时间上的不可预测性的问题,本文在常用的解决受时间限制运输问题的模型的基础上,提出了一种新的解决模型。新模型更适用于较为苛刻的调运时间,相比已有的模型更精确、更适用于现实的市场环境。文中举例说明了该模型的有效性。     

Homological dimensions of the extension algebras of monomial algebras

The main objective of this paper is to study the dimension trees and further the homological dimensions of the extension algebras — dual and trivially twisted extensions — with a unified combinatorial approach using the two combinatorial algorithms — Topdown and Bottomup. We first present a more complete and clearer picture of a dimension tree, with which we are then able, on the one hand, to sharpen some results obtained before and furthermore reveal a few more hidden subtle homological phenomenons of or connections between the involved algebras; on the other hand, to provide two more efficient combinatorial algorithms for computing dimension trees, and consequently the homological dimensions as an application. We believe that the more refined complete structural information on dimension trees will be useful to study other homological properties of this class of extension algebras.