Frobenius扩张下的W⊥-Gorenstein内射性

对于一个广义的倾斜模WR,定义了W⊥R-Gorenstein内射模和W⊥R-Gorenstein内射维数,证明了在环Frobe-nius扩张下,模的W⊥-Gorenstein内射模性是保持的,即对于MR、MR是一个W⊥R-Gorenstein内射模当且仅当M?RSS是一个(W?RSS)⊥S-Gorenstein内射模,...     

Gorenstein代数上的倾斜模的个数

若A是一个Gorenstein代数,则倾斜右A-模的个数等于倾斜左A-模的个数。给出反例说明自内射维数大于等于2的Gorenstein代数B的经典倾斜右B-模的个数不一定等于经典倾斜左B-模的个数。     

Empirical Bayesian Density Forecasting in Iowa and Shrinkage for the Monte Carlo Era

The track record of a 20‐year history of density forecasts of state tax revenue in Iowa is studied, and potential improvements sought through a search for better‐performing ‘priors’ similar to that conducted three decades ago for point forecasts by Doan, Litterman and Sims (Econometric Reviews, 1984). Comparisons of the point and density forecasts produced under the flat prior are made to those produced by the traditional (mixed estimation) ‘Bayesian VAR’ methods of Doan, Litterman and Sims, as well as to fully Bayesian ‘Minnesota Prior’ forecasts. The actual record and, to a somewhat lesser extent, the record of the alternative procedures studied in pseudo‐real‐time forecasting experiments, share a characteristic: subsequently realized revenues are in the lower tails of the predicted distributions ‘too often’. An alternative empirically based prior is found by working directly on the probability distribution for the vector autoregression parameters—the goal being to discover a better‐performing entropically tilted prior that minimizes out‐of‐sample mean squared error subject to a Kullback–Leibler divergence constraint that the new prior not differ ‘too much’ from the original. We also study the closely related topic of robust prediction appropriate for situations of ambiguity. Robust ‘priors’ are competitive in out‐of‐sample forecasting; despite the freedom afforded the entropically tilted prior, it does not perform better than the simple alternatives. Copyright © 2014 John Wiley & Sons, Ltd.     

可倾瓦滑动轴承摩擦功率损耗特性研究

为了在降低轴承能耗的同时保证透平机械的高效安全运行,对轴承-转子系统进行了更准确的建模仿真。首先对转子和轴承间隙内的油膜厚度进行了精细建模,考虑润滑油温粘效应及轴瓦变形,结合小扰动法计算轴承转子动力学参数,开发出计算五瓦可倾瓦轴承程序(COMDYN-Bearing),并将文献数据与本文数据对比,以验证本模型在多项参数中尤其是功率损耗计算的准确性。最后以某合成氨装置工业汽轮机为例,实证研究轴承宽径比、预负荷等结构参数对功率损耗以及转子稳定性的对应关系,结果表明:随着轴承预负荷的增大,轴承功耗和最高瓦温随之降低,但转子的稳定性也随之降低;随着宽径比的增加,轴承最大瓦温降低,但功耗增加,转子稳定性降低。     

2-Calabi-Yau三角范畴中的丛倾斜对象

在2-Calabi-Yau三角范畴中,几乎完备丛倾斜对象或几乎完备极大刚性对象T都存在两个补T1、T2.本文给出了T为几乎完备丛倾斜对象时满足⊥T［1］=add(T⊙T1⊙T2)的一个充要条件, 并将该充要条件推广到n丛范畴中的n丛倾斜对象. 另外, 本文证明了如果几乎完备极大刚性对象不是几乎完备丛倾斜对象, 那么⊥T［1］add(T⊙T1⊙T2)并进一步得到了极大刚性对象T是丛倾斜对象当且仅当⊥(T⊙T2)［1］(     

倾斜代数的优化扩张

讨论了倾斜代数和拟倾斜代数在优化扩张下的不变性.证明了如果B是Artin代数A的优化扩张,A是拟倾斜代数当且仅当B是拟倾斜代数;设A是Artin R-代数,如果A是R的优化扩张,则A是倾斜代数当且仅当R是倾斜代数.     

倾斜西海岸线的正压海洋对中纬西风的响应

用超松弛迭代法数值求解带有非线性平流项的正压准平衡海洋模型,以讨论在东北—西南向的倾斜西海岸线下,海洋流场对中纬西风强迫的响应。当存在该倾斜时,海洋响应中关于β通道中心轴线的对称性遭破坏。倾斜度越大,西海岸处β通道中流函数零线与西海岸线的夹角越小,且其位置也向北偏移得越多;倾斜度固定时,地面西风急流形式的风场分布得越宽阔,上述偏移越明显。非线性下存在解对参数很敏感和迭代不收敛的情况,但在取典型参数时非线性与线性两者的计算结果几乎相同。考虑西海岸线倾斜后的结果较取正南北向的结果更接近于真实,这表明该倾斜的影响是重要和不可忽视的。     

GLS-代数的奇点范畴

设H是GLS-代数,D_(sg)(mod~Z H)是其有限维Z-分次H-模的奇点范畴。本文证明了D_(sg)(mod~Z H)存在倾斜对象,从而D_(sg)(mod~Z H)三角等价于某个代数投射模的有界同伦范畴。     

AOD炉倾动力矩精确计算及耳轴中心安全高度位置确定

运用solidworks软件建立AOD炉及钢液的三维实体模型,以获取其重心坐标,并对新炉、旧炉倾动力矩进行了精确的计算,依据倾动力矩变化曲线提出了防止炉体自动倾翻的耳轴中心安全高度的合理位置。     

计入三维热效应对可倾瓦推力轴承动力特性的影响

在考虑三维热效应的情况下,研究线支撑可倾瓦推力轴承的动力特性.建立广义雷诺方程、完整的三维能量方程、瓦体的热传导方程和温粘关系,联立求解非线性偏微分方程组,计算油膜的刚度和阻尼系数.研究表明：温度变化对可倾瓦推力轴承的动力特性有较大影响;与不计入热效应的线支撑可倾瓦推力轴承相比,计入三维热流体的可倾瓦推力轴承的油膜刚度和阻尼系数会增大,其理论计算结果更接近实际工况;随着载荷、入口温度的增加以及转速的减小,油膜的刚度和阻尼也会随之增大.