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RADIATIVE TRANSPORT IN THE DELTA-P1 APPROXIMATION FOR LAMINAR OPTICAL TOMOGRAPHY
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作者 BAOHONG YUAN 《Journal of Innovative Optical Health Sciences》 SCIE EI CAS 2009年第2期149-163,共15页
To provide a computational efficient forward model with moderate accuracy for rapid 3D optical tomography in small volumes,radiative transport in the delta-P1 approximation combined with the approximation of the recip... To provide a computational efficient forward model with moderate accuracy for rapid 3D optical tomography in small volumes,radiative transport in the delta-P1 approximation combined with the approximation of the reciprocity was examined.Perturbations of optical signals caused by absorption and fluorescence heterogeneities submerged in a resin-based liquid phantom with background parameters close to rat brain tissues were measured using a recently constructed laminar optical tomography system.These measured perturbations were used to examine the theoretically calculated fluence perturbations based on the delta-P1 approximation and the reciprocity approximation.Results show that the errors between the predicted and measured data are acceptable,especially for fluorescence perturbations. 展开更多
关键词 Photon migration TOMOGRAPHY fluorescence delta-p1 approximation reciprocity approximation.
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Mo_(1-x)W_(x)C碳化物稳定性及力学性质的第一性原理计算 被引量:1
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作者 周少兰 丛大龙 +5 位作者 杨九州 李立 黄安畏 冉旭东 陈汉宾 李忠盛 《原子与分子物理学报》 北大核心 2024年第3期127-134,共8页
金属碳化物作为基体的增强相,对钢铁的力学性能起到至关重要的作用.采用基于密度泛函理论的第一性原理方法,通过虚拟晶体近似构建Mo_(1-x)W_(x)C(0≤X≤1)碳化物模型,计算Mo_(1-x)W_(x)C的晶格常数、形成能、结合能、弹性常数、弹性模... 金属碳化物作为基体的增强相,对钢铁的力学性能起到至关重要的作用.采用基于密度泛函理论的第一性原理方法,通过虚拟晶体近似构建Mo_(1-x)W_(x)C(0≤X≤1)碳化物模型,计算Mo_(1-x)W_(x)C的晶格常数、形成能、结合能、弹性常数、弹性模量、泊松比u、维氏硬度、电子态密度等性质参数,分析W元素对MoC碳化物稳定性及力学性能的影响.本次计算值与其他理论计算值及试验值吻合度较高;随着W含量的增加,晶格常数增加,Mo_(1-x)W_(x)C的形成能、结合能皆为负值,结合能、形成能的绝对值均随着W含量的增加而增加.不同掺杂含量下的Mo_(1-x)W_(x)C均满足Born判据,在力学上是稳定的,随着W含量的增加,Mo_(1-x)W_(x)C的弹性常数、体模量、杨氏模量、剪切模量呈线性增加,B/G、泊松比降低.Mo_(1-x)W_(x)C在费米能级处的态密度值均不为0,态密度值随着W含量的增加而降低.Mo_(1-x)W_(x)C能自发形成且能稳定存在,随着W含量的增加,Mo_(1-x)W_(x)C碳化物的稳定性、弹性模量、硬度及耐磨性均增加,Mo_(1-x)W_(x)C呈脆性,脆性大小随着w含量的增加而增加. 展开更多
关键词 第一性原理 虚拟晶体近似 Mo_(1-x)W_(x)C 力学性质
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质子入射Al_(x)Ga_(1-x)N材料的位移损伤模拟
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作者 何欢 白雨蓉 +5 位作者 田赏 刘方 臧航 柳文波 李培 贺朝会 《物理学报》 SCIE EI CAS CSCD 北大核心 2024年第5期92-99,共8页
氮化镓材料由于优良的电学特性以及耐辐照性能,其与不同含量Al_(x)Ga_(1-x)N材料组成的电子器件,有望应用于未来空间电子系统中.然而目前关于氮化镓位移损伤机理研究多关注于氮化镓材料,对于Al_(x)Ga_(1-x)N材料位移损伤研究较少.本文... 氮化镓材料由于优良的电学特性以及耐辐照性能,其与不同含量Al_(x)Ga_(1-x)N材料组成的电子器件,有望应用于未来空间电子系统中.然而目前关于氮化镓位移损伤机理研究多关注于氮化镓材料,对于Al_(x)Ga_(1-x)N材料位移损伤研究较少.本文通过两体碰撞近似理论模拟了10 keV-300 MeV质子在不同Al元素含量的Al_(x)Ga_(1-x)N材料中的位移损伤机理.结果表明质子在Al_(x)Ga_(1-x)N材料中产生的非电离能损随质子能量增大而下降,当质子能量低于40 MeV时,非电离能损随着Al含量的增大而变大,当质子能量升高时该趋势相反;分析由质子导致的初级撞出原子以及非电离能量沉积,发现不同Al_(x)Ga_(1-x)N材料初级撞出原子能谱虽然相似,然而Al元素含量越高,由弹性碰撞产生的自身初级撞出原子比例越高;对于质子在不同深度造成的非电离能量沉积,弹性碰撞导致的能量沉积在径迹末端最大,而非弹性碰撞导致的能量沉积在径迹前端均匀分布,径迹末端减小,并且低能质子主要是通过弹性碰撞造成非电离能量沉积,而高能质子恰好相反.本研究揭示了不同Al元素含量的Al_(x)Ga_(1-x)N材料质子位移损伤机理,为GaN器件在空间辐射环境下的应用提供参考依据. 展开更多
关键词 Al_(x)Ga_(1-x)N 质子 位移损伤 两体碰撞近似
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APPROXIMATION ANALYSES FOR FUZZY VALUED FUNCTIONS IN L_1(μ)-NORM BY REGULAR FUZZY NEURAL NETWORKS 被引量:4
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作者 Liu Puyin (Dept. of System Eng. and Math., National Univ. of Defence Tech., Changsha 410073) 《Journal of Electronics(China)》 2000年第2期132-138,共7页
By defining fuzzy valued simple functions and giving L1(μ) approximations of fuzzy valued integrably bounded functions by such simple functions, the paper analyses by L1(μ)-norm the approximation capability of four-... By defining fuzzy valued simple functions and giving L1(μ) approximations of fuzzy valued integrably bounded functions by such simple functions, the paper analyses by L1(μ)-norm the approximation capability of four-layer feedforward regular fuzzy neural networks to the fuzzy valued integrably bounded function F : Rn → FcO(R). That is, if the transfer functionσ: R→R is non-polynomial and integrable function on each finite interval, F may be innorm approximated by fuzzy valued functions defined as to anydegree of accuracy. Finally some real examples demonstrate the conclusions. 展开更多
关键词 FUZZY VALUED simple function REGULAR FUZZY neural network L1(μ) approximation Universal approximator
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Distribution function estimates by Wasserstein metric and Bernstein approximation for C^(-1) functions 被引量:2
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作者 WU Zong-min TIAN Zheng 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2015年第2期141-150,共10页
The aim of the paper is to estimate the density functions or distribution functions measured by Wasserstein metric, a typical kind of statistical distances, which is usually required in the statistical learning. Based... The aim of the paper is to estimate the density functions or distribution functions measured by Wasserstein metric, a typical kind of statistical distances, which is usually required in the statistical learning. Based on the classical Bernstein approximation, a scheme is presented. To get the error estimates of the scheme, the problem turns to estimating the L1 norm of the Bernstein approximation for monotone C-1 functions, which was rarely discussed in the classical approximation theory. Finally, we get a probability estimate by the statistical distance. 展开更多
关键词 Wasserstein metric Bernstein approximation L1 norm approximation confidence interval
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APPROXIMATION PROPERTIES OF LAGRANGE INTERPOLATION POLYNOMIAL BASED ON THE ZEROS OF (1-x^2)cosnarccosx
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作者 Laiyi Zhu 《Analysis in Theory and Applications》 2006年第2期183-194,共12页
We study some approximation properties of Lagrange interpolation polynomial based on the zeros of (1-x^2)cosnarccosx. By using a decomposition for f(x) ∈ C^τC^τ+1 we obtain an estimate of ‖f(x) -Ln+2(f, ... We study some approximation properties of Lagrange interpolation polynomial based on the zeros of (1-x^2)cosnarccosx. By using a decomposition for f(x) ∈ C^τC^τ+1 we obtain an estimate of ‖f(x) -Ln+2(f, x)‖ which reflects the influence of the position of the x's and ω(f^(r+1),δ)j,j = 0, 1,... , s,on the error of approximation. 展开更多
关键词 Lagrange interpolation polynomial zeros of 1 -x^2)cos n arccosx piecewise smooth functions error of approximation
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APPROXIMATION BY KANTOROVICH-BERNSTEIN POLYNOMIALS IN L_p(0
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作者 G.T.Tachev 《Analysis in Theory and Applications》 1992年第3期38-50,共13页
The purpose of the present paper is to evaluate the error of the approximation of the func- tion fL_1[0,1]by Kantorovich-Bernstein polynomials in L_p-metric(0<p<1).
关键词 METRIC p<1 approximation BY KANTOROVICH-BERNSTEIN POLYNOMIALS IN L_p
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L_p(1≤p≤∞) APPROXIMATION BY AN n-DIMENSIONAL SUBSPACE ON A SET OF n+1 POINTS
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作者 史应光 《Acta Mathematica Scientia》 SCIE CSCD 1993年第4期430-436,共7页
Some new characterizations and immediate explicit expressions of best L(1≤p≤∞) approximation and their deviations by an n-dimensional subspace on a set of n+1 points are given.
关键词 approximation BY AN n-DIMENSIONAL SUBSPACE ON A SET OF n+1 POINTS L_p ID Case
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The Mixed Spin-1/2 and Spin-1 Ising–Heisenberg Model in the Mean-Field Approximation: a New Approach
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作者 Erhan Albayrak 《Chinese Physics Letters》 SCIE CAS CSCD 2018年第3期84-88,共5页
Thermodynamic properties of the mixed spin-1 and spin-1/2 Ising-Heisenberg model are studied on a honeycomb lattice using a new approach in the mean-field approximation to analyze the effects of longitudinal Dz and tr... Thermodynamic properties of the mixed spin-1 and spin-1/2 Ising-Heisenberg model are studied on a honeycomb lattice using a new approach in the mean-field approximation to analyze the effects of longitudinal Dz and transverse Dx crystal fields. The phase diagrams are calculated in detail by studying the thermal variations of the order parameters, i.e., magnetizations and quadrupole moments, and compared with the literature to assess the reliability of the new approach. It is found that the model yields both second- and first-order phase transitions, and tricritical points. The compensation behavior of the model is also investigated for the sublattice magnetizations, and longitudinal and transverse quadrupolar moments. The latter type of compensation is observed in the literature but its possible importance is overlooked. 展开更多
关键词 Heisenberg Model in the Mean-Field approximation The Mixed Spin-1/2 and Spin-1 Ising a New Approach
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APPROXIMATION BY FABER-LAURENT RATIONAL FUNCTIONS IN THE MEAN OF FUNCTIONS OF CLASS LP(T) WITH 1
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作者 A. Cavus D. M. Israfilov 《Analysis in Theory and Applications》 1995年第1期105-118,共14页
Let Γ be a regular curve and Lp (Γ), 1<p<+∞. be the class of all complex - valued functions f de-fined on Γ which are such that |f|p is mtegrabie in sense of Lebesgue. In this work, we define the k th p-Fabc... Let Γ be a regular curve and Lp (Γ), 1<p<+∞. be the class of all complex - valued functions f de-fined on Γ which are such that |f|p is mtegrabie in sense of Lebesgue. In this work, we define the k th p-Fabcrpolynomial F k,p (z),the kth p-Faber principle part F k.p (1/z) for Γ , and defined the nth p-Fcber- Laurent rational function Rn.p (f, z) and p- generalized modulus of continuity Ωp(f, t) of a function f of Lp(Γ) We inves-tigate some properties of Fk,p (z) and Fk.p (1/z). And then we prove a direct theorem characterizing the degree of approximation with respect to Ω (. , t) in the mean of functions of Lp(Γ) by the rational junctions Rn.p (. . z). 展开更多
关键词 approximation BY FABER-LAURENT RATIONAL FUNCTIONS IN THE MEAN OF FUNCTIONS OF CLASS LP WITH 1 Rational
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On Converse Theorem of Best Approximation by Polynomials in Bergman Spaces H_q^p(p>0,q>1)
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作者 邢富冲 《Chinese Quarterly Journal of Mathematics》 CSCD 1993年第4期89-98,共10页
A Bernstein type theorem and a converse theorem of best approximation by polynomials in Bergman spaces Hq^p(p>0,q>1) are proved.Some proofs and results in [1] are in proved.
关键词 BERGMAN空间 多项式逼近 最佳逼近 逆定理 Bers空间 复平面 解析函数 BERNSTEIN不等式 连续性积分模
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APPROXIMATE POWER OF HETEROSCEDASTICITY TEST IN NONLINEAR MODELS WITH ARIMA(0,1,0) ERRORS 被引量:1
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作者 Lin Jinguan Wei Bocheng Zhang Nansong 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2005年第4期423-430,共8页
This paper presents an approach for estimating power of the score test, based on an asymptotic approximation to the power of the score test under contiguous alternatives. The method is applied to the problem of power ... This paper presents an approach for estimating power of the score test, based on an asymptotic approximation to the power of the score test under contiguous alternatives. The method is applied to the problem of power calculations for the score test of heteroscedasticity in European rabbit data (Ratkowsky, 1983). Simulation studies are presented which indicate that the asymptotic approximation to the finite-sample situation is good over a wide range of parameter configurations. 展开更多
关键词 ARIMA (0 1 0) errors asymptotic approximation HETEROSCEDASTICITY local power nonlinear model score test.
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Truncated series solutions to the(2+1)-dimensional perturbed Boussinesq equation by using the approximate symmetry method
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作者 焦小玉 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第10期123-129,共7页
In this paper, the(2+1)-dimensional perturbed Boussinesq equation is transformed into a series of two-dimensional(2 D) similarity reduction equations by using the approximate symmetry method. A step-by-step proce... In this paper, the(2+1)-dimensional perturbed Boussinesq equation is transformed into a series of two-dimensional(2 D) similarity reduction equations by using the approximate symmetry method. A step-by-step procedure is used to acquire Jacobi elliptic function solutions to these similarity equations, which generate the truncated series solutions to the original perturbed Boussinesq equation. Aside from some singular area, the series solutions are convergent when the perturbation parameter is diminished. 展开更多
关键词 approximate symmetry method (2+1)-dimensional perturbed Boussinesq equation series solutions convergence of series solutions
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4-氨基-1-羟基-2-氧-1,8-萘啶-3-甲酰胺类化合物抑制HIV整合酶链转移活性的主要微观结构因素探究
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作者 康家雄 李爱秀 +1 位作者 靳玉瑞 肖泽云 《化学与生物工程》 CAS 2023年第6期16-21,34,共7页
以25个4-氨基-1-羟基-2-氧-1,8-萘啶-3-甲酰胺类化合物为研究对象,利用遗传函数逼近法(GFA)构建了10个二维定量构效关系(2D-QSAR)模型,从中选取最优模型并检验其预测可靠性,并分析4-氨基-1-羟基-2-氧-1,8-萘啶-3-甲酰胺类化合物抑制HIV... 以25个4-氨基-1-羟基-2-氧-1,8-萘啶-3-甲酰胺类化合物为研究对象,利用遗传函数逼近法(GFA)构建了10个二维定量构效关系(2D-QSAR)模型,从中选取最优模型并检验其预测可靠性,并分析4-氨基-1-羟基-2-氧-1,8-萘啶-3-甲酰胺类化合物抑制HIV整合酶链转移活性的主要微观结构因素。结果表明,最优2D-QSAR模型的R^(2)=0.7776、Q^(2)=0.6421、r^(2)=0.87、(r^(2)-r′02)/r^(2)=0.01、k′=0.97、r^(2)_(m)=0.58,具有较高的稳定性和外部预测能力;热力学描述符AlogP、电拓扑状态描述符ES_Sum_sssN、ES_Sum_ssCH 2和空间描述符Shadow_nu是影响4-氨基-1-羟基-2-氧-1,8-萘啶-3-甲酰胺类化合物抑制HIV整合酶链转移活性的主要微观结构因素,其中Shadow_nu是最重要的微观结构因素。 展开更多
关键词 4-氨基-1-羟基-2-氧-1 8-萘啶-3-甲酰胺 整合酶链转移 抑制剂 遗传函数逼近法 二维定量构效关系
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正则表达式分组的1/(1-1/k)-近似算法 被引量:12
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作者 柳厅文 孙永 +2 位作者 卜东波 郭莉 方滨兴 《软件学报》 EI CSCD 北大核心 2012年第9期2261-2272,共12页
对正则表达式集合进行分组是解决DFA状态膨胀问题的一种重要方法.已有的分组算法大都是启发式的或蛮力的,分组效果很差.分析了DFA状态膨胀的原因,总结了某些正则表达式间的冲突状况.证明了当冲突非负和冲突独立时,正则表达式集合的最优... 对正则表达式集合进行分组是解决DFA状态膨胀问题的一种重要方法.已有的分组算法大都是启发式的或蛮力的,分组效果很差.分析了DFA状态膨胀的原因,总结了某些正则表达式间的冲突状况.证明了当冲突非负和冲突独立时,正则表达式集合的最优k分组问题可归结为最大k割问题,从而说明该问题是NP-Hard的.基于局部搜索的思想,提出了一种分组算法GRELS来解决分组问题,并证明对最大k割问题,该算法的近似比是1/(1-1/k).与已有的分组算法相比,当分组数目相同时,GRELS算法分组结果的状态总数最少,并且集合发生变化时所需的更新时间最短. 展开更多
关键词 正则表达式 深度包检测 分组算法 局部搜索 1/(1-1/k)近似
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一种基于盲运算的1比特压缩感知重建算法 被引量:1
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作者 闫斌 陈浩 +1 位作者 王文东 周小佳 《西南交通大学学报》 EI CSCD 北大核心 2015年第2期264-269,共6页
为了解决1比特压缩感知中符号匹配追踪算法(matching sign pursuit)在稀疏度未知的情况下不能自适应重构信号的问题,提出了向前/向后迭代符号匹配追踪算法(forward-backward matching sign pursuit,FBMSP).该算法以逐步逼近理论为核心,... 为了解决1比特压缩感知中符号匹配追踪算法(matching sign pursuit)在稀疏度未知的情况下不能自适应重构信号的问题,提出了向前/向后迭代符号匹配追踪算法(forward-backward matching sign pursuit,FBMSP).该算法以逐步逼近理论为核心,通过逐步扩大支撑集来扩大搜索范围,把相邻两次迭代的差值作为终止条件,在MSP算法模型下进行盲运算,以实现信号的重构.数值试验表明:在控制迭代系数α=8,β=1的情况下,FBMSP算法比传统的符号匹配追踪算法重构精度提高了3 d B,运算时间减少了40%. 展开更多
关键词 信号处理 压缩感知 逼近论 1比特 符号匹配追踪
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铁路网上技术直达列车编组计划优化的二次0-1规划法 被引量:20
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作者 曹家明 朱松年 《铁道学报》 EI CAS CSCD 北大核心 1993年第2期62-70,共9页
以文献[1]的构模原理为基础,构造了任意结构的路网上双方向技术直达列车编组计划综合优化的二次0-1规划模型,然后给出了这类模型的若干理论结果,并在此基础上介绍了模型的解法、计算试验结果及分析。
关键词 铁路网 列车编组计划 松弛问题
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0-1背包问题的非线性降维近似算法 被引量:4
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作者 赵建英 《内蒙古师范大学学报(自然科学汉文版)》 CAS 2007年第1期25-29,共5页
求解0-1背包问题的精确算法不能在较短时间内求解大规模0-1背包问题,使其实用性受到限制.针对该问题,给出求解0-1背包问题的非线性降维算法,并进行了数值实验,验证了算法的有效性.该算法属于近似算法,相对其他一些近似算法,计算结果更... 求解0-1背包问题的精确算法不能在较短时间内求解大规模0-1背包问题,使其实用性受到限制.针对该问题,给出求解0-1背包问题的非线性降维算法,并进行了数值实验,验证了算法的有效性.该算法属于近似算法,相对其他一些近似算法,计算结果更为精确. 展开更多
关键词 0-1 背包问题 非线性降维算法 精确算法 近似算法
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基于贪婪策略的0/1背包问题算法研究 被引量:7
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作者 游维 《计算机与现代化》 2007年第4期10-12,16,共4页
对求解0/1背包问题的贪婪策略进行了详细的讨论。在分析价值密度贪婪算法缺陷的基础上,提出了重做贪婪选择的改进算法,并从理论和实验两个方面证明了其求解质量的提高。本文还详细分析了k阶优化算法,并证明了其近似比为k/(k+1),最后编... 对求解0/1背包问题的贪婪策略进行了详细的讨论。在分析价值密度贪婪算法缺陷的基础上,提出了重做贪婪选择的改进算法,并从理论和实验两个方面证明了其求解质量的提高。本文还详细分析了k阶优化算法,并证明了其近似比为k/(k+1),最后编程模拟了该算法的实现过程,并对结果进行了分析。 展开更多
关键词 0/1背包问题 贪婪策略 k阶优化算法 近似比
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关于L^1-逼近的若干注记 被引量:2
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作者 周观珍 《杭州大学学报(自然科学版)》 CSCD 1998年第3期19-25,共7页
具有O正则变化拟单调系数的Fourier级数的复值函数f的L1逼近的特征之一是:‖f-Sn(f)‖=O(ψn)En(f)=O(ψn)和^f(n)log|n|=O(ψ|n|),这里Sn(f)是部分和算子,{ψn}... 具有O正则变化拟单调系数的Fourier级数的复值函数f的L1逼近的特征之一是:‖f-Sn(f)‖=O(ψn)En(f)=O(ψn)和^f(n)log|n|=O(ψ|n|),这里Sn(f)是部分和算子,{ψn}是一个单调递减趋于零的数列,满足ψn=O(ψ2n).现问在什么情况下条件En(f)=O(ψn)可以省去?本文讨论这个问题,并给出一些肯定的回答. 展开更多
关键词 复值函数 L^1-逼近 傅里叶级数 傅里叶系数
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