• Safety and Health at Work
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• v.11 no.4
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• pp.397-404
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• 2020

Background: Most job exposure matrices (JEMs) have been developed for chemical and physical hazards in the United States (US). In addition, the overall validity of most JEMs of work organization hazards using self-reported data in the literature remains to be further tested due to several methodological weaknesses. Methods: This paper aims to review important methodological issues with regard to a JEM of work organization hazards using self-report data and to present a research protocol for developing a four-axis (job titles, hazards, sex, and time) JEM of major work organization hazards using the US General Social Survey-Quality of Work-Life (GSS-QWL) data (2002-2018; N = 7,100 workers). Results: Five methodological weaknesses in existing JEMs of work organization hazards using self-report data were identified: having only two axes (hazard and occupation), using psychometrically weak items and scales, including scales having little interoccupational variability, unresolved optimal minimum numbers of subjects per occupation, and low accessibility. The methodological weaknesses were successfully addressed in the proposed research protocol. Conclusion: The work organization JEM to be developed will significantly facilitate and strengthen occupational epidemiological studies on work organization hazards and major health outcomes, improve national and occupational surveillance of work organization hazards, and promote interventions for a healthy work environment in the US.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.357-357
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• 2000

In this study, we consider a multi-input multi-output styrene polymerization reactor system for which the monomer conversion and the weight average molecular weight are controlled by manipulating the jacket inlet temperature and the feed flow rate. The reactor system is identified by using a linear subspace identification method and then the output feedback model predictive controller is constructed on the basis of the identified model. Here we use the Best Linear Unbiased Estimation (BLUE) filter as a stochastic estimator instead of the Kalman filter. The BLUE filter observes the state successfully without any a priori information of initial states. In contrast to the Kalman filter, the BLUE filter eliminates the offset by observing the state of the augmented system regardless of a priori information of the initial state for an integral white noise augmented system. A BLUE filter has a finite impulse response (FIR) structure which utilizes finite measurements and inputs on the most recent time interval [i-N, i] in order to avoid long processing times.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1397-1400
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• 2013

The influence of electron beam irradiation on photocatalytic activity of $TiO_2$ thin films was investigated. $TiO_2$ thin films were prepared by anodization of Ti foil, and they were then subjected to an 1 MeV electron beam. Changes in physical properties and photocatalytic activity of $TiO_2$ before and after e-beam irradiation were investigated. The crystallinity of the synthesized materials was investigated by X-ray diffraction, and the oxidation states of both titanium and oxygen were determined by X-ray photoelectron spectroscopy (XPS). The density of donor ($N_d$) and flat band potential ($E_{fb}$) were investigated by Mott-Schottky analysis, and photocurrent was measured under a 1kW Xenon lamp illumination. After e-beam irradiation, significant change of Ti oxidation state was observed. $Ti^{3+}/Ti^{4+}$ ratio increased mainly due to the surface reduction by electron, and photocurrent was observed to increase with e-beam irradiation.

• Journal of the Korean Electrochemical Society
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• v.13 no.1
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• pp.57-62
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• 2010

New monomers, possessing various alkyl substituents on propylene dioxypyrrole, were synthesized. The monomers could be easily polymerized to produce highly conductive and soluble polymers. The corresponding polymers showed excellent solubility, retaining electrochemical and optical properties of their parent polymer [poly(propylene dioxypyrrole)]. The conductivities of chemically prepared polymers were quite high in a range of 20 and $60\;Scm^{-1}$. Solubility of the polymer in a common organic solvent was as high as no polymer is deposited on an electrode. The redox potentials of the electrochemically prepared polymers revealed quite stable electro-activity during repeated redox switching up to 500 times. The optoelectrochemistry studies also showed distinct color changes of the polymers upon changing the doping state, indicating strong absorption peaks at 400~600 nm in reduced states and complete bleaching in fully oxidized states.

• 대한예방의학회:학술대회논문집
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• 2005.10a
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• pp.31-44
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• 2005

In summary, air pollution issues in the United States are addressed by a core group of regulations supplemented by active Interventions as needed by public health agencies. The strategies employed by public health officials must be flexible and innovative to address the needs of the citizens, As you can see from the examples cited above, the collaboration of public health agencies can be critical in protecting communities from adverse exposures. In the US state and local governments have the primary responsibility for health and safety issues, including those associated with air pollution. The federal agencies have responsibilities when activities between states are involved and or the issues are of national significance. Significant challenges and opportunities remain to identify the relationship to air pollution and other environmental factors and the incidence of disease, and hence develop and implement Intervention strategies.

• Journal of Photoscience
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• v.10 no.1
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• pp.165-173
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• 2003

m-Phenylene-linked biscarbenes, bisnitrenes and carbenonitrenes can be formed photochemically from appropriate nitrogenous precursors. Generation of such reactive intermediates under matrix-isolation conditions allows for their characterization by spectroscopic techniques such as ESR, UV /vis and IR. The latter method is also useful in characterizing secondary products derived from these reactive intermediates. Computational chemistry methods complement experimental IR data, aiding, thus, in identification of such compounds. In addition electronic structure calculations help in developing qualitative and semi-quantitative models, which can be useful in predicting ground-state multiplicities. The parent systems of m-phenylene-linked carbenes and nitrenes have high-spin ground states, but a switching to lower multiplicity can be achieved by chemical substitution. The ground state and various low-lying excited states of m-phenylenecarbenonitrenes can be reasonably approximated by simple valence-bond depictions. Finally, m-phenylenecarbenonitrenes are photoreactive in the inert matrix isomerizing to cyclopropene derivatives.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1539-1540
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• 2008

The field degradation of carbon nanotube field emitters in diode emission at constant current was demonstrated to be highly dependent upon the presence of residual gases at partial pressures. Upon exposure to a higher pressure of oxygen containing gases, for example, $O_2$ and CO increased the voltage. Those gases give rise to chemical etching to CNTs emitters. On the contrary, $CH_4$ affected the emission properties in the opposite direction as decreasing the voltage which was probably attributed to the introduction of adsorbate tunneling states. The mixed gas may cause a combined effect of both adsorbate tunneling states and CNT etching.

• Journal of the Korean Vacuum Society
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• v.1 no.1
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• pp.145-152
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• 1992

Si surfaces exposed to CHF3/C2F6 gas plasmas ih reactive ion etching (RIE) have been characterized by X-ray photoelectron spectroscopy (XPS). CHF3/C2F6 gas plasma exposure of Si surface leads to the deposition of residual film containing carbon and fluorine. The narrow scan spectra of C 1s show various bonding states of carbon as C-Si, C-F/H, C-CFx(x $\leq$ 3), C-F, C-F2, and C-F3. The chemical bonding states of fluorine are described with F-Si, F-C and F-O. And the oxygen and silicon are also detected. The effects of parameters for reactive ion etching as CHF3/C2F6 gas ratio, RF power, and pressure are investigated.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1402-1404
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• 2009

The silicon nitride films for gate dielectric were deposited by catalytic chemical vapor deposition at low temperature (${\leq}200^{\circ}C$). The mixture of $SiH_4$, $NH_3$ and $H_2$ was used as source gases. The current-voltage (I-V) and the capacitance-voltage (C-V) characteristics of the films were measured. The breakdown voltage and the flat band voltage shift of samples were improved by increase of the $NH_3$ contents and $H_2$ dilution ratio. The defect states were analyzed by photoluminescence (PL) spectra. As the defect states decreased, the breakdown voltage and the flat band voltage shift increased.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.176-178
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• 2002

Surface states of silicone polymer treated by plasma were investigated by the analysis by x-ray photoelectron spectroscopy(XPS) and surface voltage decay after corona charging. Plasma treatment causes the silica -like oxidative layer, which was confirmed with XPS, and lowers surface resistivity with increasing the plasma treatment time. Using the decay time constant of surface voltage, the calculated surface resistivity was compared with the value directly measured by voltage-current method using three electrodes system. A good agreement between two methods was obtained. In addition, we estimated the thermal activation energy for surface conduction, Based on our results, we could understand the relationship between surface chemical states and surface electrical properties.