一个修正PRP共轭梯度法的全局收敛性

In this paper, a modified formula for βk^PRP is proposed for the conjugate gradient method of solving unconstrained optimization problems. The value of βk^PRP keeps nonnegative independent of the line search. Under mild conditions, the global convergence of modified PRP method with the strong Wolfe-Powell line search is established. Preliminary numerical results show that the modified method is efficient.     

非线性Schr\"{o}dinger方程组解的整体存在与有限时刻爆破的两个门槛结果[英文]

本文研究一类薛定谔方程的初值问题. 我们建立解的整体存在与有限时刻爆破的两个门槛结果并讨论了驻波解的不稳定性.     

火焰原子吸收光谱法测定不锈钢中高含量镍

镍的火焰原子吸收光谱法的测定已有报道,在测定中大多采用232.0 nm吸收线。光谱分析波长适合于微量镍的测定,但不适于不锈钢中高含量镍的测定。国家标标准GB/T 223.25—1994方法对不锈钢中镍的测量范围为0.030%～2.00%,不适合应用于样品中镍含量大于2%的样品的测定,应选用丁二酮肟重量法和EDTA滴定法测定镍量,操作繁琐,耗时长。针对此问题,本工作采用火焰原子吸收光谱法,采用镍341.5 nm次灵敏线测定不锈钢中高含量镍,样品经盐酸-硝酸-水(3+1+12)溶液溶解后定     

电感耦合等离子体质谱法测定纯铜中微量元素

纯铜线材广泛应用于现代电子工业,对其产品的纯度要求很高,尤其对铅、锌、铋、锑、锡、砷、镍、铁等元素有一定的限量要求,这些杂质元素的含量直接影响其牌号的确定及交易价格。这些元素含量相     

评析问题213——两种结果貌异实同,p可用a,b的代数式表示

评析本问题的稿件纷至沓来,至截稿时止,共收稿49篇.来稿均认为两种结果貌异实同,解法2的结果可进一步简化为解法1的结果,这是因为p,a,b互相依存,并不独立.事实上,     

New approach for normalization and photon-number distributions of photon-added （-subtracted） squeezed thermal states

Using the thermal field dynamics theory to convert the thermal state into a "pure" state in doubled Fock space, we find that the average value of efa a under squeezed thermal state (STS) is just the generating function of Legendre polynomials. Based on this remarkable result, the normalization and photon-number distributions of m-photon added (or subtracted) STSs are conviently obtained as the Legendre polynomials. This new concise method can be expanded to the entangled case.     

测量结果表达式与不确定度关系的研究与探讨

测量不确定度和结果表达是学习物理实验的重要概念,它是衡量测量结果可靠性和准确程度的标志.本文就这些概念以及它们之间关系一一进行阐述,以有利于学生学习与参考.     

A note on lower bound of centered L2-discrepancy on combined designs

This note provides a theoretical justification of optimal foldover plans in terms of uniformity. A new lower bound of the centered L ₂-discrepancy values of combined designs is obtained, which can be used as a benchmark for searching optimal foldover plans. Our numerical results show that this lower bound is sharper than existing results when more factors reverse the signs in the initial design.     

IMPROVED ESTIMATES OF THE COVARIANCE MATRIX IN GENERAL LINEAR MIXED MODELS

In this article, the problem of estimating the covariance matrix in general linear mixed models is considered. Two new classes of estimators obtained by shrinking the eigenvalues towards the origin and the arithmetic mean, respectively, are proposed. It is shown that these new estimators dominate the unbiased estimator under the squared error loss function. Finally, some simulation results to compare the performance of the proposed estimators with that of the unbiased estimator are reported. The simulation results indicate that these new shrinkage estimators provide a substantial improvement in risk under most situations.     

A FAST SIMPLEX ALGORITHM FOR LINEAR PROGRAMMING

Recently, computational results demonstrated remarkable superiority of a so-called ＂largest-distance＂ rule and ＂nested pricing＂ rule to other major rules commonly used in practice, such as Dantzig＇s original rule, the steepest-edge rule and Devex rule. Our computational experiments show that the simplex algorithm using a combination of these rules turned out to be even more efficient.