中国国内生产总值及其相关因素分析

自1978年改革开放以来,中国国内生产总值连续高速增长.基于对1978-2008年共31年来中国国内生产总值、固定资产投资、能源消费总量、进出口贸易总额、居民消费、人口数、财政收入等因素的关系研究,提出一个更为合适的对数线性模型,同时给出了该模型中参数的估计方法.研究表明:截止至2008年,中国国内生产总值的增长是不均衡的,而是分阶段的,而且在不同阶段,影响国内生产总值的因素有所不同,并且从经济学角度对所建立的模型给出了合理的解释,结论符合中国实际.     

Estimation of bioreactor efficiency through structured hydrodynamic modeling case study of a Pichia pastoris fed-batch process

In this article, two theories are unified to investigate the effect of hydrodynamics on a specific bioprocess: the network-of-zones (NOZ) hydrodynamic structured modeling approach (developed by several researchers but applied to only a few bioprocesses) and the effectiveness factor η approach. Two process scales were investigated (20 and 500 L), and for each, hydrodynamics were quantified using an NOZ validated by homogeneity time measurements. Several impeller combinations inducing quite different hydrodynamics were tested at the 20-L scale. After this step, effectiveness factors were determined for each fermentation run. To achieve this, a perfectly mixed microbial kinetic model was evaluated by using simple Monod kinetics with a fed-batch mass balance. This methodology permitted determination of the effectiveness factor with more accuracy because of the relation with the perfect case deduced from the Monod kinetics. It appeared that for the small scale, η decreased until reaching a value of approx 0.7 (30% from the ideal case) for the three impeller systems investigated. However, stirring systems that include hydrofoils seemed to maintain higher effectiveness factors during the course of the fermentation. This effect can be attributed to oxygen transfer performance or to homogenization efficiency exhibited by the hydrofoils. To distinguish the oxygen transfer from the homogenization component of the effectiveness factor, these phenomena were analyzed separately. After determining the evolution of η_{O 2} linked to oxygen transfer for each of the fermentation runs, the NOZ model was employed to quantify substrate gradient appearance. After this step, another effectiveness factor, η_mix, related to mixing was defined. Consequently, it is possible to distinguish the relative importance of the mixing effect and oxygen transfer on a given bioprocess. The results have highlighted an important scale effect on the bioprocess that can be analyzed using the NOZ model.     

美国旅华需求的影响因素：模型构建与检验

关于美国旅华的研究多为描述性的定性研究,定量研究较少,且对美国旅华需求的研究鲜见。因此,本文首先提出影响美国旅华需求的因素假设,然后通过Johansen协整分析,构建出相应协整模型,同时验证了假设。进一步通过Granger因果关系检验,表明影响因素的假设是有效的。从而得出结论:美国旅华需求对在华生活相对价格变化、人民币兑美元汇率变化都缺乏弹性,而对美国总人口变化及美国人均收入变化率的变化非常敏感.     

Excited nucleon electromagnetic form factors from broken spin-flavor symmetry

A group theoretical derivation of a relation between the N →△ charge quadrupole transition and neutron charge form factors is presented.     

Fundamental factors versus herding in the 2000–2005 US stock market and prediction

We present a general methodology to incorporate fundamental economic factors to the theory of herding developed in our group to describe bubbles and antibubbles. We start from the strong form of rational expectation and derive the general method to incorporate factors in addition to the log-periodic power law (LPPL) signature of herding developed in ours and others’ works. These factors include interest rate, interest spread, historical volatility, implied volatility and exchange rates. Standard statistical AIC and Wilks tests allow us to compare the explanatory power of the different proposed factor models. We find that the historical volatility played the key role before August of 2002. Around October 2002, the interest rate dominated. In the first six months of 2003, the foreign exchange rate became the key factor. Since the end of 2003, all factors have played an increasingly large role. However, the most surprising result is that the best model is the second-order LPPL without any factor. We thus present a scenario for the future evolution of the US stock market based on the extrapolation of the fit of the second-order LPPL formula, which suggests that herding is still the dominating force and that the unraveling of the US stock market antibubble since 2000 is still qualitatively similar to (but quantitatively different from) the Japanese Nikkei case after 1990.     

Influence Diagnostics in Partially Varying-Coefficient Models

When a real-world data set is fitted to a specific type of models,it is often encountered that oneor a set of observations have undue influence on the model fitting,which may lead to misleading conclusions.Therefore,it is necessary for data analysts to identify these influential observations and assess their impacton various aspects of model fitting.In this paper,one type of modified Cook's distances is defined to gaugethe influence of one or a set observations on the estimate of the constant coefficient part in partially varying-coefficient models,and the Cook's distances are expressed as functions of the corresponding residuals andleverages.Meanwhile,a bootstrap procedure is suggested to derive the reference values for the proposed Cook'sdistances.Some simulations are conducted,and a real-world data set is further analyzed to examine theperformance of the proposed method.The experimental results are satisfactory.     

Reaction of an anisotropic cylindrical shell to a moving load

A method is proposed to determine the stress-strain state of inhomogeneous anisotropic viscoelastic cylindrical shells subject to a load moving along the circumference with a given velocity. The effect of localization of the load on the dynamic stress and displacement amplification factors is examined for cylinders of different lengths __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 4, pp. 80–88, April 2007.     

Disjoint directed quadrilaterals in a directed graph

Let D be a directed graph of order 4k, where k is a positive integer. Suppose that the minimum degree of D is at least 6k ? 2. We show that D contains k disjoint directed quadrilaterals with only one exception. © 2005 Wiley Periodicals, Inc. J Graph Theory     

Dispersion theory and the low-energy constants for neutral-pion photoproduction

The relativistic amplitudes of pion photoproduction are evaluated by dispersion relations at t = const. The imaginary parts of the amplitudes are taken from the MAID model covering the absorption spectrum up to center-of-mass energies W = 2.2GeV. For sub-threshold kinematics the amplitudes are expanded in powers of the two independent variables ν and t related to energy and momentum transfer. Subtracting the loop corrections from this power series allows one to determine the counter terms of covariant baryon chiral perturbation theory. The proposed continuation of the amplitudes into the unphysical region provides a unique framework to derive the low-energy constants to any given order as well as an estimate of the higher-order terms by global properties of the absorption spectrum.     

On multivariate attenuation factors

In this paper, we introduce the method of discrete attenuation factors for the approximate computation of multivariate discrete Fourier transforms. We consider attenuation factors related with multivariate discrete Bernoulli functions and deduce a best approximation property of the corresponding method of attenuation factors. Choosing a unique approach to the discrete and non-discrete settings, we emphasize the close relation between both cases and interpret results in the literature from a more general point of view.