我国大学生英语发音受母语影响分析

为探究母语发音对英语语音音素的影响,从而探究如何更好地掌握英语语音的发音技巧和提高英语发音的基本功的能力。对50名大学英语一年级学生进行了试验研究,结果表明:母语发音对英语语音音素有很大的影响,这种影响主要表现在声母发音对英语辅音群的影响;韵母对英语元音素的影响。了解母语发音对英语语音音素的影响对学生掌握纯正、标准的英语发音以及口语表达和听力能力的提高有重大的指导意义。     

Asymptotics of cross-validated risk estimation in estimator selection and performance assessment

Risk estimation is an important statistical question for the purposes of selecting a good estimator (i.e., model selection) and assessing its performance (i.e., estimating generalization error). This article introduces a general framework for cross-validation and derives distributional properties of cross-validated risk estimators in the context of estimator selection and performance assessment. Arbitrary classes of estimators are considered, including density estimators and predictors for both continuous and polychotomous outcomes. Results are provided for general full data loss functions (e.g., absolute and squared error, indicator, negative log density). A broad definition of cross-validation is used in order to cover leave-one-out cross-validation, V-fold cross-validation, Monte Carlo cross-validation, and bootstrap procedures. For estimator selection, finite sample risk bounds are derived and applied to establish the asymptotic optimality of cross-validation, in the sense that a selector based on a cross-validated risk estimator performs asymptotically as well as an optimal oracle selector based on the risk under the true, unknown data generating distribution. The asymptotic results are derived under the assumption that the size of the validation sets converges to infinity and hence do not cover leave-one-out cross-validation. For performance assessment, cross-validated risk estimators are shown to be consistent and asymptotically linear for the risk under the true data generating distribution and confidence intervals are derived for this unknown risk. Unlike previously published results, the theorems derived in this and our related articles apply to general data generating distributions, loss functions (i.e., parameters), estimators, and cross-validation procedures.     

基于梯度法的OD矩阵估计和应用研究

以交通规划软件EMME／2为平台，在拥有合理的原始矩阵和一定数量的路段实测流量数据的基础上，运用梯度法(最速下降法)求出OD矩阵估计．结合具体的课题研究应用情况，证明该方法适用于大规模实际路网．     

CO_2增加与气候突变时的参数关系及判据

建立了一个包含云与辐射动态相互作用的一维非线性能量平衡气候模型，根据超熵产生理论，求得相应的稳定性判据．在此基础上，讨论了ＣＯ＿２增量与气候突变的参数关系．研究表明，在不考虑其余参数变化的前提下，当ＣＯ＿２浓度增至大于１０３５．８×１０￣（－６）时，气候系统将发生突变．     

莱茵衣藻-se两步法产氢用培养基的研究

分析了TAP(Tris-Acet-Phosphate)、seTA(se-Tris-Acet)、seP(se-Phosphate)、seTH(se-Tris-HCl)和se这5种培养基对莱茵衣藻-se生长产氢的影响,并进行了培养基的含量分析.结果发现,培养基的pH和氮素的含量是影响莱茵衣藻生长的重要因素;而培养基中醋酸根的含量则有助于提高厌氧产氢过程中衣藻的氢酶活性,从而提高其产氢量.综合考虑两步法产氢对细胞生长周期和细胞密度的要求以及最终厌氧诱导获得的氢酶活性,最终选择seTA培养基作为莱茵衣藻-se产氢用培养基.     

两种不同体系的双向电泳比较

探讨蛋白质组学中不同体系的双向凝胶电泳技术(2-DE)对昆虫细胞内蛋白质分离和电泳结果的影响。以经Cry1Ac抗性筛选的粉纹夜蛾BT1-Tn-5B1细胞为例,分别进行ISO-DALT和IPG-DALT方法进行双向聚丙烯酰胺凝胶电泳,并比较了电泳图谱。ISO-DALT得到了700多个蛋白质斑点,IPG-DALT得到了800多个蛋白质点。前者的pH梯度不稳定,受电场和时间的影响较大,制得的胶条的重复性不好,但对样品的要求不高。后者有稳定的pH梯度,操作方便,但对样品中盐离子浓度的耐受性低。     

毛泽东与大跃进时期的"浮夸风"

毛泽东对于当时盛行的浮夸风现象,尽管没有提倡,但其一系列的决策和主张,实际上对浮夸风的产生和蔓延起了鼓舞、推动的作用,从客观行为效果的角度来看,他实际上是相信、认可了浮夸风,并且被卷入其中,成为浮夸风不自觉的提倡与鼓吹者。随着运动的发展,毛泽东对浮夸风的认识开始转变,由相信、认可的角色逐渐转向对其作出怀疑、否定的判断,并由此开始了局部的纠偏努力,取得了一些成效。由于根本指导思想的"左"倾错误,其纠偏的成效是有限的,未能从根本上纠正、终止浮夸风的破坏。     

I^2C总线器件及其通用单片机软件接口

本文简要介绍Ｉ２Ｃ总线规范，并以Ｉ２Ｃ总线器件２４ＬＣ０２Ｂ与Ｉｎｔｅｌ８０９８单片机的接口为例，介绍了在通用单片机应用系统中Ｉ２Ｃ总线的软件实现方法。     

How the local supply of day-care centers influences fertility in Norway: A parity-specific approach

In order to assess how expansion of day care facilities affects fertility, the Norwegian Family and Occupation Survey of 1988 was linked with individual register-based migration histories and time-series data on day-care coverage rates in all Norwegian municipalities. Many factors affect both the allocation of resources to day-care centers and a woman's probability of giving birth. The local coverage rate is positively associated with the probability of advancing from parity two, after control for geographical region, degree of urbanization and other confounders. This effect of day-care supply, which is significant at low coverage levels, contributed to a moderate rise in third-birth rates after the mid-1970s. However, if the aggregate employment rate for women is also regarded as a confounder, the effect of day care may actually be insignificant. Moreover, the effect fades at higher coverage levels. Finally, there are indications that second- and first-birth probabilities decline with increasing provision of day care. These results suggest that further efforts to improve the supply of private and public day care - which in Norway are likely to be motivated by non-demographic concerns - will have little stimulating effect on fertility, at least if the subsidies and quality of care remain unchanged.     

数控技术专业“2 1”教学改革模式的实践与探索

数控技术专业进行"2 1"教学改革模式的实践与探索,全面提高了专业建设水平、教育教学质量和毕业生就业率,本文就该人才培养模式的理论体系设计、实践课程的改革和校外教学体系建立进行了总结。