纸张复卷机的设计造型与仿真

本论文介绍了下引纸复卷机的方案,针对关键部件底辊进行了设计计算,用UG软件完成了整机三维造型,并结合3DSMAX实现了复卷过程的仿真。     

Estimated non-linearities and multiple equilibria in a model of distributive-demand cycles

We introduce the results of a non-parametric estimate of the US wage-Phillips Curve into a simplified version of the model of the wage-price spiral by Flaschel and Krolzig (2008). Making use of Okun’s law, the non-linearity in the wage inflation-employment relation translates into a non-linearity in the so-called ‘distributive curve’ of the economy. Exploiting the observed non-linearity in extending an otherwise standard demand-distribution model (Taylor 2004 Taylor, Lance. 2004. Reconstructing macroeconomics. structuralist proposals and critique of the mainstream, Cambridge, MA: Harvard University Press.  [Google Scholar]), we provide a dynamical analysis both in wage-led and profit-led effective demand regimes. In a profit-led scenario, shown to be the empirically relevant case for the US economy, there are two stable equilibria of Goodwin (1967 Goodwin, R.M. 1967. “A growth cycle”. In Socialism, capitalism and economic growth, Edited by: Feinstein, C.H. Cambridge, , UK: Cambridge University Press.  [Google Scholar]) growth cycle type, identified as a stable depression and a stable boom, and a saddle-path stable equilibrium in between them. Both stable steady states are surrounded by trajectories that cycle counterclockwise around their basins of attraction. The obtained type of growth fluctuations can be verified by a long phase cycle estimation for the US economy using a method developed by Kauermann, Teuber and Flaschel (2008 Kauermann, G., Teuber, T. and Flaschel, P. 2008. “Estimating loops and cycles using penalized splines”. Bielefeld: CEM working paper.  [Google Scholar]).     

Cost-effective compensation to avoid carbon emissions from forest loss: An approach to consider price-quantity effects and risk-aversion

Analyses were carried out on financial compensation to avoid loss of tropical forests and related carbon (C) emissions when marginal financial yield declined for land-use options with extended areas, and when a risk-averting perspective (modeled according to financial theory around the capital asset pricing model) is assumed. The approach in this study was to consider natural forest, forest plantation, pasture, and cropland simultaneously to investigate how an optimized land-use distribution may reduce the amount of compensation necessary to avoid C emissions from forest loss.The financial compensations derived were as high as US$ 176 per hectare per year when comparing natural forests only with the most profitable alternative (croplands). However, compensation decreased to US$ 124 for risk-neutral decision-makers, who would strive for optimized land-use allocation, and to only US$ 47 per hectare per year for risk-avoiders, who would look to maximize the reward-to-variability ratio. Sensitivity analyses indicated that the compensation under risk-aversion increased much less than under risk-ignoring when increased productivity of agricultural land-use or growing demand for agricultural products was simulated. It was concluded that considering appropriate diversification strategies and the well documented human behavior to avoid risks is an important step in developing cost-effective compensation policies.     

在数学建模中培养学生创新性思维及建议

本文论述了数学建模对培养学生创新能力、提高综合素质的重要作用,指出大学生创新性思维能力的培养是数学建模活动的核心目标,对在数学建模活动中如何培养学生的创新性思维能力作了讨论,并根据学校开设数学建模课程及参加数学建模竞赛活动的现状,就如何提高数学建模成绩提出了一些建议.     

When do B2B brands influence the decision making of organizational buyers? An examination of the relationship between purchase risk and brand sensitivity

The dominant perspective on organizational buying behavior suggests that buyers tend to rely on objective criteria when making product choice decisions and that the potential influence of subjective cues, such as brands, on buyer decision making decreases with increasing risk. An alternative perspective, confirmed in this study by in-depth interviews with various managers, suggests that brands serve as a risk-reduction heuristic, whereby the influence of brands on decision making increases as a function of risk. Building on risk and information processing theories, this research builds on these complementary perspectives to propose that risk and brand sensitivity relate in a U-shaped manner, where brand sensitivity is highest in relatively low- or high-risk situations. The results of scenario- and survey-based field studies—involving 206 and 180 members of buying centers, respectively—suggest that both perspectives have merit and support the proposed nonlinear relationship. Moreover, the findings reveal that the risk-brand sensitivity relationship is moderated by competitive intensity, such that the linear (negative) and quadratic (positive) effects are stronger when competitive intensity is low.     

Accommodating spatial correlation across choice alternatives in discrete choice models: an application to modeling residential location choice behavior

This paper presents a modeling methodology capable of accounting for spatial correlation across choice alternatives in discrete choice modeling applications. Many location choice (e.g., residential location, workplace location, destination location) modeling contexts involve choice sets where alternatives are spatially correlated with one another due to unobserved factors. In the presence of such spatial correlation, traditional discrete choice modeling methods that are often based on the assumption of independence among choice alternatives are not appropriate. In this paper, a Generalized Spatially Correlated Logit (GSCL) model that allows one to represent the degree of spatial correlation as a function of a multi-dimensional vector of attributes characterizing each pair of location choice alternatives is formulated and presented. The formulation of the GSCL model allows one to accommodate alternative correlation mechanisms rather than pre-imposing restrictive correlation assumptions on the location choice alternatives. The model is applied to the analysis of residential location choice behavior using a sample of households drawn from the 2000 San Francisco Bay Area Travel Survey (BATS) data set. Model estimation results obtained from the GSCL are compared against those obtained using the standard multinomial logit (MNL) model and the spatially correlated logit (SCL) model where only correlations across neighboring (or adjacent) alternatives are accommodated. Model findings suggest that there is significant spatial correlation across alternatives that do not share a common boundary, and that the GSCL offers the ability to more accurately capture spatial location choice behavior.     

农村公共产品多元合作供给效应实证研究

农村公共产品的多元合作供给有利于改善供给绩效。在理论研究的基础上,根据结构方程模型的相关原理构建了农村公共产品多元合作供给与供给绩效关系的假设模型。通过调查问卷的发放、分析和数据处理,获得了农村公共产品多元合作供给与供给绩效关系的相关数据。运用结构方程模型的研究方法,对假设模型进行了检验。结果表明:农村公共产品多元合作供给的各影响因素与供给绩效有显著的正相关关系,农村公共产品的多元合作供给对供给绩效有积极的正向影响作用。     

农户经济视角下的我国农村土地流转影响因素——基于Multiple Choice Model的调查研究

利用农户土地流转问卷调查所得到的微观数据,采用统计分析、Probit multiple choicemodel方法,将农户经济行为中的保障性行为、投资行为、就业行为和产业选择行为引入土地流转的实证研究领域。研究结果显示：目前的土地流转多为暂时性流转,土地流转结构性供需矛盾严重;农户对土地的需求目的更多来自于保障性需要;农户的投资行为、就业行为、社会保障行为对土地流转有着重要影响。     

浅谈培养和提高学生数学建模能力的对策

数学建模是一种数学思想方法,可以帮助学生灵活地综合地应用所学的知识来处理和解决一些现实生活中的问题.文章首先对数学建模的步骤、数学建模能力作了介绍;接着分析学生在数学建模中存在的问题,并针对问题提出培养和提高学生数学建模能力的对策.     

基于SC-FDMA的认知无线电网络的研究

物理层数据传输方案的选择是认知无线电（CR）技术能在实际中广泛应用的重要基础。给出了将SC—FDMA（单载波频分多址）技术应用于CR网络中的传输方案,并与传统的NC—OFDM（非连续的OFDM）技术进行分析比较。仿真结果和相应分析表明：在CR网络中,总体而言SC—FDMA的性能比NC—OFDM更为优良,特别是在严重的频率选择性衰落环境中,或者是当认知用户的可用频谱资源（子载波）比较稀少时,SC—FDMA的性能优势更加明显。因此SC—FDMA是一种很有前景的技术,在不久的将来有希望取代NC—OFDM,成为CR网络的物理层传输方案。