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同步是OFDM系统中的关键技术,最大似然估计算法在OFDM符号定时同步和载波频率同步中得到了广泛的应用.通过仿真可以清楚地看到,拓宽的ML算法使ML算法在应用范围上有了扩展.并且能够更好地实现OFDM系统的符号同步和载波同步. 相似文献
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主要研究了分组数据的区间估计问题.一个密度函数的支撑集(不依赖于参数)被分成一些互不相交区间,则分组数据是样本落入每一区间的观测值的个数.本文主要讨论了正态分布下分组数据均值的区间估计问题. 相似文献
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本文基于不完全样本中的分组样本研究方法,当失效数据服从指数分布时,对给定的两个加速应力水平下的恒加试验进行了分析和探究,并讨论了在平均寿命的对数的渐近方差达到最小的时候,对受试元件观察的等间隔时间问题. 相似文献
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假设第i个可修系统的失效时间遵从强度函数为vi(t) =αiβtβ - 1,αi>0 ,β >0的非齐次Poisson过程 ,其中尺度参数αi 互不相同 ,i=1,2 ,…… ,m ,那么可以用一个复合的非齐次Poisson过程来作为系统的失效模型。本文给出了定时截尾和定数截尾两种情况下 ,模型参数的极大似然估计 ,以及系统能达到的MTBF的极大似然估计 相似文献
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基于二项分布B(n,p)总体,给出了未知参数p2的矩估计和极大似然估计,并讨论了估计量的无偏性。 相似文献
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林路 《邵阳学院学报(社会科学版)》1998,(2)
摘要 本文研究一般的线性回归模型的观测向量受到一种污染时未知参数的最大似然估计,并讨论了若干用于统计推论的统计量在污染下的不变性。不变性的研究提示我们,在何种统计推断中可无视污染的影响。 相似文献
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In the context of an afterschool program in which students explore relatively large authentic datasets, we investigated how 11- to 14-year old students worked with categorical variables. During the program, students learned to use the Common Online Data Analysis Platform (CODAP), a statistical analysis platform specifically designed for middle and high school students, to create and interpret graphs. Following the program, we conducted individual clinical interviews, during which students used CODAP to answer questions about relationships between variables. Here, we describe how students engaged in exploratory data analysis that involved looking at relationships between two categorical variables. Students worked from data in table form and created “contingency graphs,” a variant of contingency tables, which they used to analyze and draw insights from the data. Our research identified four strategies that students used to examine the data in order to explore patterns, make comparisons, and answer questions with the data. 相似文献
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本文运用主成分分析法和ML方法对C.TEST进行探索性因素分析。在C.TEST(A—D级)试卷中,提取到了3个公共因素,我们认为C.TEST(A—D级)至少考察到了应试者听的能力、汉字书写能力和图表的识别能力。在C.TEST(E—F级)试卷中,也提取到3个公共因素,我们认为C.TEST(E—F级)至少考察到了应试者听的能力、读的能力和汉语拼音认读能力。这说明C.TEST除了具有较高的信度外,还具有良好的构想效度,即测到了测验设计者想要测到的东西。 相似文献
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This study compared diagonal weighted least squares robust estimation techniques available in 2 popular statistical programs: diagonal weighted least squares (DWLS; LISREL version 8.80) and weighted least squares–mean (WLSM) and weighted least squares—mean and variance adjusted (WLSMV; Mplus version 6.11). A 20-item confirmatory factor analysis was estimated using item-level ordered categorical data. Three different nonnormality conditions were applied to 2- to 7-category data with sample sizes of 200, 400, and 800. Convergence problems were seen with nonnormal data when DWLS was used with few categories. Both DWLS and WLSMV produced accurate parameter estimates; however, bias in standard errors of parameter estimates was extreme for select conditions when nonnormal data were present. The robust estimators generally reported acceptable model–data fit, unless few categories were used with nonnormal data at smaller sample sizes; WLSMV yielded better fit than WLSM for most indices. 相似文献
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《The Journal of educational research》2012,105(1):3-15
Abstract The ability of cognitive, affective, personality, and demographic variables to predict second-language acquisition among college students was investigated. An all possible subsets regression analysis was used to compare the proportion of variance in foreign-language achievement explained by each variable. The analysis revealed that variables from each of the 4 domains were important predictors of foreign-language achievement. Overall, academic achievement, as measured by GPA average, was the best predictor, explaining 11.5% of the variance in foreign-language achievement. Foreign-language anxiety, the next best predictor, explained 10.5% of the variance. The educational implications of these findings for understanding foreign-language achievement are discussed, along with suggestions for future research. 相似文献
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何江 《新疆师范大学学报(哲学社会科学版)》2006,27(2):153-158
文章以汉语声调为实验材料,通过合成语音样本,对汉族学生和维吾尔族学生进行辨别实验和区分实验。研究表明虽然汉族学生的辨别感知为范畴性感知,但并不对应区别实验中的高峰,所以从两个实验的对应性来讲,不是范畴性感知而是介于范畴性与非范畴性感知之间,即半范畴性感知。维吾尔族学生在辨别实验中的结果表明其声调感知不是范畴性感知。通过对比汉维两组受试组的区分实验结果,表明维吾尔族学生对音高变化的绝对值更为敏感。 相似文献
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张志明 《内蒙古师范大学学报(哲学社会科学版)》2012,(1):10-15
康德的《道德形而上学原理》是继亚里士多德《尼各马可伦理学》之后最伟大的伦理学著作。该著作系统论述了绝对命令的思想。绝对命令使康德在伦理学领域发动了一次哥白尼式的革命,即把伦理学由他律转变为自律。自杀问题便是康德对其以绝对命令为基础的自律伦理学的感性检验。 相似文献
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We describe and evaluate a random permutation test of measurement invariance with ordered-categorical data. To calculate a p-value for the observed (?)χ2, an empirical reference distribution is built by repeatedly shuffling the grouping variable, then saving the χ2 from a configural model, or the ?χ2 between configural and scalar-invariance models, fitted to each permuted dataset. The current gold standard in this context is a robust mean- and variance-adjusted ?χ2 test proposed by Satorra (2000), which yields inflated Type I errors, particularly when thresholds are asymmetric, unless samples sizes are quite large (Bandalos, 2014; Sass et al., 2014). In a Monte Carlo simulation, we compare permutation to three implementations of Satorra’s robust χ2 across a variety of conditions evaluating configural and scalar invariance. Results suggest permutation can better control Type I error rates while providing comparable power under conditions that the standard robust test yields inflated errors. 相似文献
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人的类本质:解构与回归——解读马克思《1844 年经济学哲学手稿》中人的类本质思想 总被引：1，自引：0，他引：1
马克思《1844年经济学哲学手稿》从全新的角度阐述了人的类本质问题。对其进行重新解读,可回归马克思关于人的类本质的原初态度——对人的类本质的消解。 相似文献
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张林军 《暨南大学华文学院学报》2010,(2):15-20
研究考察了韩国、日本和泰国留学生的汉语声调知觉,发现：零起点的韩国和日本留学生的知觉是连续性的,泰国留学生则表现出一定的范畴化特征,但和汉语母语者的知觉模式并不一致;初级水平的韩国、日本和泰国留学生表现出和汉语母语者一致的知觉模式,但在范畴化程度上和母语者存在差别;初级水平的韩国、日本和泰国留学生在知觉的范畴化程度上不存在差别。结果表明零起点学习者汉语声调的范畴化知觉受到母语经验的影响,但音高重音和声调语言的母语经验对声调范畴化知觉能力的发展并没有明显的促进作用。 相似文献
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通过构建中职教育变量对产业结构变量影响的实证模型,进行实证研究发现:中职教育对我国产业结构调整有较大的正向促进作用,中职教育发展规模强于财政预算内经费投入规模对产业结构调整的影响。因此,必须重新认识中职教育的地位和作用,提高其经费使用效率,在"求大"的同时更要"求强"。 相似文献
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