Browsing by Author "Pan, Wei"

Now showing 1 - 7 of 7
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    Acoustic differences between healthy and depressed people: a cross-situation study
    Wang, Jingying; Zhang, Lei; Liu, Tianli; Pan, Wei; Hu, Bin; Zhu, Tingshao (2019-10-15)
    Background Abnormalities in vocal expression during a depressed episode have frequently been reported in people with depression, but less is known about if these abnormalities only exist in special situations. In addition, the impacts of irrelevant demographic variables on voice were uncontrolled in previous studies. Therefore, this study compares the vocal differences between depressed and healthy people under various situations with irrelevant variables being regarded as covariates. Methods To examine whether the vocal abnormalities in people with depression only exist in special situations, this study compared the vocal differences between healthy people and patients with unipolar depression in 12 situations (speech scenarios). Positive, negative and neutral voice expressions between depressed and healthy people were compared in four tasks. Multiple analysis of covariance (MANCOVA) was used for evaluating the main effects of variable group (depressed vs. healthy) on acoustic features. The significances of acoustic features were evaluated by both statistical significance and magnitude of effect size. Results The results of multivariate analysis of covariance showed that significant differences between the two groups were observed in all 12 speech scenarios. Although significant acoustic features were not the same in different scenarios, we found that three acoustic features (loudness, MFCC5 and MFCC7) were consistently different between people with and without depression with large effect magnitude. Conclusions Vocal differences between depressed and healthy people exist in 12 scenarios. Acoustic features including loudness, MFCC5 and MFCC7 have potentials to be indicators for identifying depression via voice analysis. These findings support that depressed people’s voices include both situation-specific and cross-situational patterns of acoustic features.
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    Dry etching of layer structure oxides
    (United States Patent and Trademark Office, 1999-02-23)
    A method of patterning layered structure oxide thin films involving placing the layered structure thin film (with or without a mask) laid on a substrate into a chamber which is partially filled with CHC1FCF.sub.3 gas and producing a glow discharge to cause the etching of the thin film ferroelectric material. The method provides high etch rates, good etch anisotropy and good etch uniformity. For example, for SBT and SBN thin films, the etch process provides etch rates in the range of 2.5 to 17.5 nm/min depending on the etch conditions and minimal etch residues at the end of the etch process is removed easily by low temperature (250.degree. C.) baking. Also, the method provides good etch selectivity in the films and minimal surface damage.
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    Dry etching processes for ferroelectric capacitors
    Pan, Wei (Virginia Polytechnic Institute and State University, 1995)
    Dry etching processes for patterning of ferroelectric thin films using environmental benign etching gases was developed. The PbZrxTi1-xO3 (PZT) and RuO2 films were patterned using CHCIFCF3 and O2. Selective etching between PZT and RuO2 was achieved by changing the gas composition. The etched profile and surface were anisotropic and smooth. Surface residues were found after etching and were removed by a post-etch heat treatment. In addition, the reactive ion etching damage to PZT ferroelectric capacitors was first defined and studied using Ar and CHCIFCF3 etch gases. It was found that the internal field developed in the capacitors during etching was responsible for causing the shift in hysteresis loop and the reduction of switchable remnant polarization. The increase in leakage current after etching can be attributed to the electrical properties change at the interface of Pt/PZT and the roughness along the side wall of a PZT capacitor after RIE. Furthermore, the etching damage effect to PZT capacitors was substantially recovered by post-etching annealing at 400 °C for 30min. The dry etching processes for new layered structure SrBi2(TaxNb1-x)2O9 ferroelectric films were developed in this research using CHCIFCF3and SF6 as etching gases. Physical sputter etching was the dominant etching mechanism in RIE of SBT and SBN films. Sr-enrichment on the etched surfaces was observed for both SBT and SBN films and was removed by post etching cleaning solution developed in this research. From a technological point of view, a practical dry etch process for etching of RuO2 films was first developed using O2/CF3CFH2 (R-134) etching gases. The maximum etch rate, 1625 Ȧ/min, of RuO2 was obtained at pressure of 75 mTorr and rf power of 200W in Or2-2.5% CF3CFH2 discharge. RuO2 films were successfully patterned under these conditions using SiO2 as the etch mask. The etching mechanism was investigated from a scientific aspect. Several impurity gases, such as N2, SF6, and H2, were added into the oxygen discharge for this investigation. Atomic oxygen is the dominant active species reacting with RuO2 films to form RuO4 volatile products. The addition of impurity gases in oxygen discharge increased the generation rate and/or the life-time of atomic oxygen in the reactor thereby enhancing the etch rate. CF3CFH2 gas had the strongest effect in increasing the generation rate (G), and accordingly, addition of a small amount of CF3CFH2 in oxygen discharge yielded the highest etch rate. The decrease in the etch rate with increasing mole fraction of R-134 in the feed (>5%) was mainly due to the F atoms reacting with RuO2 to form a surface residue layer that occupied surface reaction sites impeding the reaction between O and RuO2.
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    Identification of county-level health factors associated with COVID-19 mortality in the United States
    Pan, Wei; Miyazaki, Yasuo; Tsumura, Hideyo; Miyazaki, Emi; Yang, Wei (Journal of Biomedical Research, 2020-11-01)
    Many studies have investigated causes of COVID-19 and explored safety measures for preventing COVID-19 infections. Unfortunately, these studies fell short to address disparities in health status and resources among decentralized communities in the United States. In this study, we utilized an advanced modeling technique to examine complex associations of county-level health factors with COVID-19 mortality for all 3141 counties in the United States. Our results indicated that counties with more uninsured people, more housing problems, more urbanized areas, and longer commute are more likely to have higher COVID-19 mortality. Based on the nationwide population-based data, this study also echoed prior research that used local data, and confirmed that county-level sociodemographic factors, such as more Black, Hispanic, and older subpopulations, are attributed to high risk of COVID-19 mortality. We hope that these findings will help set up priorities on high risk communities and subpopulations in future for fighting the novel virus.
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    Reactive ion etching of ferroelectric SrBi2TaxNb2-xO9 thin films
    Desu, Seshu B.; Pan, Wei (AIP Publishing, 1996-01-01)
    Ferroelectric SrBi2TaxNb2-xO9 thin films were patterned using reactive ion etching. Considering the environmental impact effect, CHCIFCF3, a special etching gas, known to be less environmentally hazardous compared to the other hydrofluorocarbons, was employed in this study. The etch rates as a function of etching parameters were investigated. An etch rate of 20 nm/min was obtained. Surface compositional change during etching was monitored by x-ray photoelectron spectroscopy. Surface residues were removed by a postetching cleaning process. (C) 1996 American Institute of Physics.
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    Reactive ion etching of lead zirconate titanate and ruthenium oxide thin films
    (United States Patent and Trademark Office, 1996-03-05)
    A method of reactive ion etching both a lead zirconate titanate ferroelectric dielectric and a RuO.sub.2 electrode, and a semiconductor device produced in accordance with such process. The dielectric and electrode are etched in an etching gas of O.sub.2 mixed with either CClF.sub.2 or CHClFCF.sub.3.
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    Reactive ion etching of lead zirconate titanate and ruthenium oxide thin films using CHClFCF.sub.3 or CHCl.sub.2 CF.sub.3 as an etch gas
    (United States Patent and Trademark Office, 1995-01-17)
    A method of reactive ion etching both a lead zirconate titanate ferroelectric dielectric and a RuO.sub.2 electrode, and a semiconductor device produced in accordance with such process. The dielectric and electrode are etched in an etching gas of O.sub.2 mixed with either CHCl.sub.2 CF.sub.3 or CHClFCF.sub.3.