Prevalence of voice disorders in African American and European American preschoolers

Several studies have reported prevalence rates for voice disorders in school-aged children. Less is known, however, about such prevalence in preschoolers, and whether racial, ethnic, or cultural diversity may influence it. The presence of voice disorders in a total of 2445 African-American and European-American preschool children, 1246 males and 1199 females, from 2 to 6 years of age is reported here. Presence of a voice disorder characterized by hoarseness was identified by a three-prong approach including teacher identification, investigator screening, and parent identification. Speech-language pathologists listened individually to each child's speech as they engaged each child in play-conversation activities. A voice disorder was identified on the basis of the judgment of two speech-language pathologists. Voice disorders characterized by hoarseness were identified in 95 children or 3.9% of the total sample by the investigators. Statistical analysis revealed no significant differences for age, gender, or race.     

The circular chemistry conceptual framework: A way forward to sustainability in industry 4.0

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Representations for conditional expectations and applications to pricing and hedging of financial products in Lévy and jump-diffusion setting

In this article, we derive expressions for conditional expectations in terms of regular expectations without conditioning but involving some weights. For this purpose, we apply two approaches: the conditional density method and the Malliavin method. We use these expressions for the numerical estimation of the price of American options and their deltas in a Lévy and jump-diffusion setting. Several examples of applications to financial and energy markets are given including numerical examples.     

胶黏剂中的化学*——2020年美国国家化学周活动介绍及启示

重点介绍2020年美国国家化学周——“胶黏剂中的化学”实验活动,对科学阅读和采访未来科学家活动作简要介绍。以此得出本次化学周活动对我国化学教学的几点启示:(1)大概念视角,加深结构化认识;(2)扎根实践,提高应用意识;(3)鼓励探析,深化本质意识;(4)跨界科学,渗透STSE理念;(5)精选主题,凸显微型项目;(6)勤研善思,塑造优秀品格。     

PBL教学模式在中美高校化学实验课教学中应用的对比研究

因课程设置、学情等不同, PBL教学模式在中美高校化学实验课的实施过程中各具特色。本文从教材、课程考核、师资培训、研究机构和基金等4个角度客观分析PBL教学模式在中美2国高校化学实验课应用中的差异,并在此基础之上提出,应该客观公正地看待这种差异,树立文化自信。     

有红利美式看跌期权定价的Crank-Nicolson有限差分法

本文基于B-S微分方程,采用Crank-Nicolson差分格式(简称C-N差分格式)求解支付固定红利的美式看跌期权价值,给出实证分析,并对C-N差分格式和隐含的差分格式进行了比较.结果表明,用C-N差分格式可以得到更加精确、有效的数值解.     

中美无机化学课程比较与探讨*——以美国康奈尔大学与河北工业大学无机化学课程为例

以河北工业大学和美国康奈尔大学的无机化学课程为例,从教材设置、教学方法和课程考核评价方式等方面对该课程教学进行了对比探讨,以期构建一套符合我国国情且具有国际视野的无机化学新的课程体系,能为国内高校本科无机化学课程的教学改革提供参考,提高其教育教学质量,促进本科人才培养。     

Pricing American Asian options with higher moments in the underlying distribution

We develop a modified Edgeworth binomial model with higher moment consideration for pricing American Asian options. With lognormal underlying distribution for benchmark comparison, our algorithm is as precise as that of Chalasani et al. [P. Chalasani, S. Jha, F. Egriboyun, A. Varikooty, A refined binomial lattice for pricing American Asian options, Rev. Derivatives Res. 3 (1) (1999) 85–105] if the number of the time steps increases. If the underlying distribution displays negative skewness and leptokurtosis as often observed for stock index returns, our estimates can work better than those in Chalasani et al. [P. Chalasani, S. Jha, F. Egriboyun, A. Varikooty, A refined binomial lattice for pricing American Asian options, Rev. Derivatives Res. 3 (1) (1999) 85–105] and are very similar to the benchmarks in Hull and White [J. Hull, A. White, Efficient procedures for valuing European and American path-dependent options, J. Derivatives 1 (Fall) (1993) 21–31]. The numerical analysis shows that our modified Edgeworth binomial model can value American Asian options with greater accuracy and speed given higher moments in their underlying distribution.     

美式期权定价问题的变网格差分方法

本文提出一种求解美式期权定价自由边值问题的变网格差分方法.通过建立一个自由边界所满足的方程,利用变网格技术可同时求出期权的差分解和最佳执行边界.本文分别讨论了显式和隐式变网格差分格式,并给出了差分解的收敛性和稳定性分析.数值实验表明本文算法是一个非常有效的期权定价算法.