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CH Park

Publications and source records attributed to CH Park.

At least 19 recordsLinked to original sources
PubMed2000

Effect of interstitial hydrogen impurities on ferroelectric polarization in PbTiO3

We investigate the electronic and atomic structure of interstitial hydrogen impurities in PbTiO3 and investigate their effect on ferroelectric polarization through first-principles total-energy calculations. Interstitial H in PbTiO3 is found to bond to oxygen and to act as a shallow donor impurity. At equilibrium, H does not much affect nearby Ti-O bonds and the H-O dipole increases the polarization. The barrier for reversing the defect dipole can give rise to imprint (extra stabilization of one of the two polarization modes).

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PubMed1999

Optical CDMA system using bacteriorhodopsin for optical data storage

An optical CDMA (code division multiple access) system for the optical data storage using bacteriorhodopsin (BR) is reported as an application of the BR materials. The desired signal of multiple input can be recorded and reconstructed by use of orthogonal codes. An experimental setup is proposed and demonstrated.

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PubMed1997

Back Pain among U.S. Workers: Comparison of Worker Attributes According to Self-reported Causes of Back Pain.

Back pain is a significant health problem, especially in industry. To gain a better understanding of back pain in light of its diverse causality, data for 29,322 working adults interviewed in the Occupational Health Supplement to the 1988 National Health Interview Survey were analyzed by self-reported cause of back pain. The 12-month prevalences of back pain for "injury or repeated activities at work," "injury or repeated activities not at work," and "other reasons," were 9.1%, 4.4%, and 4.0%, respectively. The worker attributes and work impacts associated with these self-reported causes were compared for this nationally representative sample. Results from multivariate logistic regressions indicated different profiles of worker attributes among the three cause-specific subgroups of back-pain sufferers. Work impact was substantial in all cases, but was highest for workers with work-related back pain.

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PubMed1996

Excitation Gap in the Normal State of Underdoped Bi2Sr2CaCu2O8+delta

Angle-resolved photoemission experiments reveal evidence of an energy gap in the normal state excitation spectrum of the cuprate superconductor Bi2Sr2CaCu2O8+delta. This gap exists only in underdoped samples and closes around the doping level at which the superconducting transition temperature Tc is a maximum. The momentum dependence and magnitude of the gap closely resemble those of the dx2-y2 gap observed in the superconducting state. This observation is consistent with results from several other experimental techniques, which also indicate the presence of a gap in the normal state. Some possible theoretical explanations for this effect are reviewed.

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