半导体存储器及发展趋势

半导体存储器的容量和速度决策着计算机系统运行速度。目前CPU芯片18个月一更新，为了赶上这个速度，半导体存储器的发展也日新月异。     

When to accept a sequence of gambles

When is a sequence of gambles, which is initially rejected eventually accepted? The eventual acceptance is defined as a pair property between the utility function and the sequences of gambles. A sequence of gambles is accepted when the gambles follow a large deviation principle and the utility function is non-satiated and bounded from below in a certain way. The number of gambles required for acceptance is computed.     

"大沈阳经济区"的构建与辽宁老工业基地的振兴

大沈阳经济区是指沈阳与周边经济社会活动有密切联系的地区所形成的“区域经济共同体”.它的建立对于振兴东北老工业基地具有重要的战略意义.但在建立这一经济区的过程中也不可避免的存在一些问题,这需要通过一体化运作、机制创新等有效途径来加以解决.     

Minnesota-type adaptive hierarchical priors for large Bayesian VARs

Large Bayesian VARs with stochastic volatility are increasingly used in empirical macroeconomics. The key to making these highly parameterized VARs useful is the use of shrinkage priors. We develop a family of priors that captures the best features of two prominent classes of shrinkage priors: adaptive hierarchical priors and Minnesota priors. Like adaptive hierarchical priors, these new priors ensure that only ‘small’ coefficients are strongly shrunk to zero, while ‘large’ coefficients remain intact. At the same time, these new priors can also incorporate many useful features of the Minnesota priors such as cross-variable shrinkage and shrinking coefficients on higher lags more aggressively. We introduce a fast posterior sampler to estimate BVARs with this family of priors—for a BVAR with 25 variables and 4 lags, obtaining 10,000 posterior draws takes about 3 min on a standard desktop computer. In a forecasting exercise, we show that these new priors outperform both adaptive hierarchical priors and Minnesota priors.     

大股东资金占用与审计师的监督

本文研究审计师对大股东占用上市公司资金行为的监督作用。通过对1997年到2002年间的上市公司进行分析,我们发现随着大股东资金占用程度的加大,审计师更加倾向于出示非标准意见。在大股东占用资金最多的10%的公司年度中,审计师出示非标准意见的概率高达近50%。在控制了其他影响审计师意见的变量以后,大股东资金占用程度仍然是决定审计意见的一个非常显著的因素。这说明我国的审计师对中国资本市场出现的大股东资金占用问题有一定的认识,并且将其反映到审计师意见中去。我们进一步的分析发现: (1)被审计师出具了非标准意见的公司,其大股东占用资金反而更加持续。这说明审计师意见对公司的监督意义不大,公司并没有因为审计师的意见而减轻占用程度。(2)被审计师出具了非标准意见的公司,其大股东占用对未来的股票收益的负影响与其他公司并没有区别。这说明投资者对审计师的意见并没有给予足够的重视。本文的研究结果说明,审计师对大股东盘剥中小股东的现象进行了监督、对大股东资金占用严重的公司出示了更多的非标准意见,然而这些非标准意见并没有引起各方面的重视,一方面公司的治理并没有改善,另一方面投资者也没有因审计师的意见而避免更多的损失。     

Learning,large deviations and rare events

We examine the role of generalized stochastic gradient constant gain (SGCG) learning in generating large deviations of an endogenous variable from its rational expectations value. We show analytically that these large deviations can occur with a frequency associated with a fat-tailed distribution even though the model is driven by thin-tailed exogenous stochastic processes. We characterize these large deviations, driven by sequences of consistently low or consistently high shocks and then apply our model to the canonical asset pricing framework. We demonstrate that the tails of the stationary distribution of the price–dividend ratio will follow a power law.     

Escape dynamics: A continuous-time approximation

We extend a continuous-time approximation approach to the analysis of escape dynamics in economic models with constant gain adaptive learning. This approach is based on the application of the results of continuous-time version of large deviations theory to the linear diffusion approximation of the original discrete-time dynamics under learning. We characterize escape dynamics by analytically deriving the most probable escape point and mean escape time. The approximation is tested on the Phelps problem of a government controlling inflation while adaptively learning a misspecified Phillips curve, studied previously by Sargent (1999) and Cho et al. (2002) (henceforth, CWS), among others. We compare our results with simulations extended to very low values of the constant gain and show that, for the lowest gains, our approach approximates simulations relatively well. We express reservations regarding the applicability of any approach based on large deviations theory to characterizing escape dynamics for economically plausible values of constant gain in the model of CWS when escapes are not rare. We show that for these values of the gain it is possible to derive first passage times for learning dynamics reduced to one dimension without resort to large deviations theory. This procedure delivers mean escape time results that fit the simulations closely. We explain inapplicability of large deviations theory by insufficient averaging near the point of self-confirming equilibrium for relatively large gains which makes escapes relatively frequent, suggest the changes which might help approaches based on the theory to work better in this gain interval, and describe a simple heuristic method for determining the range of constant gain values for which large deviations theory could be applicable.     

大豆大杂粉碎及重杂灭活工艺改造

随着国家对环保的重视,改变进口大豆大杂(豆荚、豆杆)焚烧处理的传统做法尤为重要,采用风选、粉碎等手段,区分处理轻重杂,杂质分别采用生产线高温高压和蒸汽湿热灭活法进行处理后,可充当纤维类物质掺入到成品豆粕中。根治环境污染的同时降低厂内安全风险,充分利用进口大豆秸秆类纤维物质,减少大豆损耗,以较小的投入实现经济效益和环境保护。     

Probabilistic assessment of fleet-level noise impacts of projected technology improvements

Demand projections for civil aviation have forecast increases in operations in future decades. Increases in demand are beneficial to the growth and advancement of the aviation industry, but also come with the threat of significant increase in environmental impacts. In response, the industry is focusing on programs to develop technologies for reductions in fuel burn, NO_x emissions, and noise. While aircraft-level impacts are an obvious metric of success, it is difficult to make informed robust technology investment decisions with respect to noise without understanding the fleet-level impacts. Fleet-level predictions of noise for technology explorations are especially complicated because it is computationally expensive, highly combinatorial, and airport-specific. Recently, rapid automated airport noise models have been developed, which can be simulated using Design of Experiments (DOE). The results of these simulations are used to generate surrogate models for airport noise contour area, which can be summed to yield a fleet-level impact. These models make use of simplifying assumptions to provide estimates of airport-level noise that are substantially cheaper to compute. They can be used to perform parametric trade-off analyses in conjunction with the equivalency assumption. Equivalency asserts that environmental impacts of a technology infused aircraft can be represented by scaled operations of the baseline aircraft in the same class. This simple assumption allows for the modeling of technology and market penetration factors under the same units: operations. This research uses surrogate models in conjunction with the equivalency assumption to examine two potential technology scenarios in a target forecast year, simulating technology and market performance factors to identify vehicle classes that could have the greatest impact in reducing contour area. Results show that technology and market performance of future notional Small Single Aisle and Large Single Aisle vehicle aircraft have the highest positive correlations with potential reductions in contour area.     

The international diversification-performance link in Spain: Does firm size really matter?

This study provides new insights into the link between international diversification and firm performance in a sample of large manufacturing firms and SMEs based in Spain for the 1994–2008 period. Specifically, the focus is on how the nature and shape of this relationship may vary over time with firm size. The results show the existence of a horizontal-S curve when the whole sample of firms is considered in the empirical analysis. However, major differences are found between SMEs and large firms, and even within the actual group of SMEs. Strong support is found in large firms for the existence of a horizontal-S curve. Within the group of SMEs, there are small firms with a linear and negative relationship, whereas medium-sized firms record a U-shaped form. These findings suggest that as the international diversification-performance link is size-dependent, future research should explicitly consider firm size in order to better understand the nature of this relationship.