Heteroskedasticity and Spatiotemporal Dependence Robust Inference for Linear Panel Models with Fixed Effects

This paper studies robust inference for linear panel models with fixed effects in the presence of heteroskedasticity and spatiotemporal dependence of unknown forms. We propose a bivariate kernel covariance estimator that is flexible to nest existing estimators as special cases with certain choices of bandwidths. For distributional approximations, we embed the level of smoothing and the sample size in two different limiting sequences. In the first case where the level of smoothing increases with the sample size, the proposed covariance estimator is consistent and the associated Wald statistic converges to a chi square distribution. We show that our covariance estimator improves upon existing estimators in terms of robustness and efficiency. In the second case where the level of smoothing is fixed, the covariance estimator has a random limit and we show by asymptotic expansion that the limiting distribution of the Wald statistic depends on the bandwidth parameters, the kernel function, and the number of restrictions being tested. As this distribution is nonstandard, we establish the validity of a convenient F-approximation to this distribution. For bandwidth selection, we employ and optimize a modified asymptotic mean square error criterion. The fl exibility of our estimator and the proposed bandwidth selection procedure make our estimator adaptive to the dependence structure. This adaptiveness effectively automates the selection of covariance estimators. Simulation results show that our proposed testing procedure works reasonably well in finite samples.Adaptiveness, HAC estimator, F-approximation, Fixed-smoothing asymptotics, Increasing-smoothing asymptotics, Panel data, Optimal bandwidth, Robust inference, Spatiotemporal dependence

Online ESL / EFL Instruction for Korean Children Under 7 Years Old: A Curricular Design

Early bilingual education is currently implemented in many countries around the world. There has been much research on the effects of early second language learning on children\u27s language development and school performance, and the results are positive. Koreans focus on learning foreign languages to communicate with other people around the world and approach to lots of information and experience. For Koreans to become fluent English speakers, the best time to learn a foreign language is during early childhood. It is a critical period for mastering pronunciation and developing language skills, making it an ideal time to easily learn a foreign language and speak like a native speaker. English education during early childhood allows Korean children to easily learn English while preserving their mother tongue, so that they can grow into bilingual children. In this article, I provide a brief history of the English education policy of the Korean government through a literature review. I also explained successful bilingual programs and factors that make the program effective. In addition, I discussed the impact of bilingual education on young children. Based on this research, I provide a platform and curriculum for online Zoom classes so that young children in Korea can attend ESL or EFL classes with native English-speaking teachers. This is to provide educational opportunities for children to listen and speak English in online class to support their bilingualism. Through the development of an effective English curriculum, children can learn English easily and in a fun way.Therefore this program can contribute to the expansion of early childhood English education and help improve Koreans\u27 English skills

Transition from quasi-unidirectional to unidirectional guided resonances in leaky-mode photonic lattices

Unidirectional light emission from planar photonic structures is highly advantageous for a wide range of optoelectronic applications. Recently, it has been demonstrated that unidirectional guided resonances (UGRs) can be realized by utilizing topological polarization singularities in momentum space. However, the practical application of these topological unidirectional emitters has been limited due to their intricate geometric configurations, requiring special efforts with high-cost fabrication processes. In this study, we show that unidirectional light emission can be achieved in conventional one-dimensional zero-contrast gratings (ZCGs), which can be easily fabricated using current nanofabrication technologies. In ZCGs, the interband coupling between even-like and odd-like waveguide modes leads to the formation of quasi-UGRs, characterized by significantly higher decay rates in either the upward or downward direction compared to the opposite direction. We demonstrate that these quasi-UGRs evolve into genuine UGRs with an gradual increase in grating thickness. Moreover, the emission direction of UGRs can be selectively steered either upward or downward by adjusting the lattice parameters. In addition to quasi-UGRs and UGRs, our study also reveals additional topological phenomena in ZCGs, including exceptional points and quasi-BICs

The Evaluation of CP-001 (a Standardized Herbal Mixture of Houttuynia cordata

In the present study, the effect of CP-001, a standardized herbal mixture of Houttuynia cordata, Rehmannia glutinosa, Betula platyphylla, and Rubus coreanus, on cytochrome P450 (CYP) enzyme-mediated drug metabolism was investigated in vitro to evaluate the potential for herb-drug interactions. CP-001 was tested at concentrations of 1, 3, 10, 30, and 100 μg/mL. A CYP-specific substrate mixture was incubated with CP-001 in human liver microsomes, and the metabolites generated by each CYP-specific metabolic reaction were measured by liquid chromatography-tandem mass spectrometry. CP-001 seemed to slightly inhibit some CYP isozymes, but the IC50 values for all CYP isozymes were greater than 100 μg/mL. Furthermore, CP-001 did not exhibit time-dependent CYP inhibitory activities, indicating that it does not act as a mechanism-based inactivator of CYP enzymes. In conclusion, the effects of CP-001 on CYP isozyme activities were negligible at the concentrations tested. Therefore, the likelihood of herbal mixture-drug interaction is considered minimal

RELATIONSHIP BETWEEN THE BALL VELOCITY AND UPPER EXTREMITY KINEMATICS DURING AN OVERARM THROWING SELF-PRACTICE PROGRAM

The purpose of this study was to investigate the relationship between the ball velocity and upper extremity kinematics in inexperienced individuals during a 5 weeks selfpractice overarm throwing. Seven women participated in this study. Participants performed 15 overarm throwing 3 days in a week for 5 weeks. The relationship between the ball velocity and the first-last week overarm throwing upper extremity kinematics data (maximum angles and angular velocities) were statistically analyzed using Spearman’s rho. Results showed there was weak to moderate relationship for both maximum angles and angular velocities of trunk, shoulder, and elbow. Rotational movements of upper extremities should be prioritized at the early stages of throwing skills acquisitions