• Journal of the Korean Ceramic Society
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• v.33 no.5
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• pp.547-555
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• 1996

Porous alumina ceramics were fabricated by pseudo-boehmite phydosol-gel process within/without commercial $\alpha$-alumina particles average 1 and 40 micron respectively. The pore characteristics of fired specimens were studied by the measurement of bulk density total porosity thyermal analysis pore volume pore distribution BET area XRD and SEM. with increasing of firing temperature pore volume and BET surface area were decreased and the average pore size was increased to approximately 146$\AA$ upto 80$0^{\circ}C$ by de-watering of [OH] and formation of $\alpha$-alumina. The fired relative density of the alumina-dispersed specimen with average 1 micron particle was increased with the amounts of dispersed particle by bimodal packing theory which is compared to the ones of specimen including of average 40 micron particle. It was confirmed that the percola-tion threshold in porous ceramics with coarser particle (40 micron) has formed between the transformed-alumina from hydrogel and dispersed-alumina of above 50 vol% particle and the total porosity was increased at the threshold point above.

• Journal of the Ergonomics Society of Korea
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• v.14 no.2
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• pp.41-50
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• 1995

A field study was conducted to assess the preferred height and the range of discomfort recognition of school desks and chairs for students from elementary school to high school. For this study 43 male subjects and 44 female subjects in Taejon metropolitan area were surveyed. The result showed that the preferred height of chairs were found to be about 1.7cm higher than the popliteal sitting height, while the preferred height of desks showed no significant difference with the elbow sitting height which is known to be the ergonomically proper desk height. The threshold value between comfort and discomfort recognition of chair heigth was 1.88cm below the most preferred height and 1.79cm above it. The threshold value between comfort and discomfort recognition of desk height was 1.76cm below the most preferred height and 2.62cm above it.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.263.2-263.2
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• 2013

We report a systematic investigation of a set of macrophotoinitiators for use in polymerization-based signal amplification. To test the dependence of photopolymerization responses on the number of photoinitiators localized per molecular recognition event, we gradually increased the number of photoinitiator molecules coupled to a scaffold macromolecule. Macrophotoinitiators constructed with an average of 7 to 168 photoinitiators per polymer with the goals of quantifying the relationship between the number of initiators per binding event and the degree of amplified colorimetric readout. To evaluate the capacity of the macrophotoinitiators to detect molecular recognition, neutravidin was coupled to these molecules to recognize biotin-labeled DNA immobilized on biochip test surfaces. Fluorescein macroinitiators are found to be useful in detecting molecular recognition above a threshold of initiators per polymer. Above this threshold, increasing the number of initiators per macroinitiator resulted in increased signal strength.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.540-541
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• 2002

In this paper, the performance of upidirectional and hi-directional regenerative erbium-doped fiber amplifier (EDFA) is compared. The systems are operating above laser oscillation threshold. The experimental results show that the unidirectional regenerative EDFA has a better performance than the hi-directional.

• Korean Management Science Review
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• v.16 no.1
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• pp.101-113
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• 1999

The individual behavior on considering prior information when one assesses the probability of uncertain event by representativeness heuristic has been investigated. While prior researches proposed two contrasting behaviors on the employment, we tested the mixed hypothesis that individual ignores the prior information to some extents and begins to consider it above certain threshold when the evidence of representativeness is not salient. The threshold effect of prior probability is positively experimented and the results strongly support the discontinuity hypothesis of representativeness heuristic.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.4
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• pp.101-108
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• 1998

We examine experimentally the dependence of output width on DC bias, RF power, and RF frequency in a gain-switched semiconductor laser. The optimum short pulses are obtained around threshold DC bias. The DC bias to generatoe shorter pulses decreases the RF power increases, whereas it increases to above threshold as the RF freqnecy increases. The pulse width becomes less sensitive to the variations of the DC bias, as the RF bias, or frquency increases.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.5 no.2
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• pp.193-199
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• 1995

This study was designed to investigate the difference of time weighted average(TWA) of noise levels and noise doses by the different operating parameter settings such as exchange rate, threshold level and criterion level for noise dosimeter in the field measurements of noise at industrial working environments. The time weighted averages of noise level and noise doses for noise working environments were determined by noise dosimeter on 80 workers employed at 20 industrial establishments of 8 industries. The results obtained were as follows: 1. The mean time weighted average(TWA) of the noise working environments by the operating parameter settings showed 93.4 dB(A) in 3 dB of exchange rate, 80 dB of threshold level and 90dB of criterion level 92.0 dB(A) in 3 dB-exchange rate, 90 dB-threshold level and 90 dB-criterion level, in 90.8 dB(A) in 5 dB of exchange rate, 80 dB of threshold level and 90 dB of criterion level, and 86.7 dB(A) in 5 dB of exchange rate, 90 dB of threshold level and 90dB of criterion level. 2. ln group of noise level less than 90 dB(A), mean TWAs of 80 dB of threshold level were significantly higher than that of 90 dB of threshold level in 3 dB and 5 dB of exchange rate. 3. The case exceeded threshold limit value of noise was 49(61.3 %) in 3dB, 80dB and 90 dB setting, 44(55.0 %) in 3 dB, 90 dB, 90 dB setting, 33(41.3 %) in 5 dB, 80dB, 90 dB setting and 26(32.5%) in 5 dB, 90 dB, 90 dB setting. Above considerations in mind, it is suggested that exchange rate and threshold level be specified in related laws and regulations in the evaluation of working environments noise.

• Journal of the Korean Wood Science and Technology
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• v.43 no.5
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• pp.641-651
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• 2015

The aim of this study was to estimate the service life of alkaline copper quaternary (ACQ)-treated wood. The service life of preservative-treated wood was estimated by comparing a residual quantity of ACQ in wood with toxic threshold to fungi. Indoor and outdoor leaching tests were carried out in order to predict residual ACQ quantity within wood. As a result, the leaching ratio of ACQ from treated wood above ground via precipitation was 18.1% for 50 years. When the H4 treated wood, which is traditionally used in contact with the ground and fresh water, is used above-ground, the leaching ratio of ACQ for 50 years is 18.1% and the residual quantity of ACQ is $4.2kg/m^3$, which is higher than the toxic threshold of ACQ. Thus, the H4 treated wood used above-ground will be resistant to biodeterioration for at least 50 years.

• Computers and Concrete
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• v.19 no.3
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• pp.257-262
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• 2017

The aim of this study is to investigate the pH threshold value for the corrosion of steel reinforcement in concrete. A method was designed to attain the pH value of the pore solution on the location of the steel in concrete. Then the pH values of the pore solution on the location of steel in concrete were changed by exposing the samples to the environment (CO25%, RH 40%) to accelerate carbonation with different periods. Based on this, the pH threshold value for the corrosion of steel reinforcement had been examined by the methods of half-cell potential and electrochemical impedance spectra (EIS). The results have indicated that the pH threshold value for the initial corrosion of steel reinforcement in concrete was 11.21. However, in the carbonated concrete, agreement among whether steel corrosion was initiatory determined by the detection methods mentioned above could be found.

• Journal of Families and Better Life
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• v.26 no.5
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• pp.129-142
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• 2008

This study examines how economic and psychological characteristics affect the quality of life (QoL) of elderly individuals age 60 and older, who live in the Seoul-metropolitan area. Relationships among socio-demographic status, economic conditions, psychological characteristics, family life, health status, and QoL are examined by t-test and ANOVA(Duncan's test as post hoc multiple comparisons), and the multiple regression analysis is used to estimate QoL determinants in the elderly. The major findings of the study are as follows. First, younger age, higher education levels, better health status, harmonious family relations, higher levels of household income, lower levels of loneliness, and higher self-esteems are related to higher QoL levels. Second, the impacts of factors on QoL are differentiated according to tercile groups that divide monthly allowance of respondents into three categories: below normal (threshold amount below 21MW), near normal (threshold amount between 21MW and 35MW), and above normal (threshold amount above 35MW). For each tercile group, poor health status or higher loneliness have negative effects on QoL, while harmonious family relationship has a positive effect. For the below-normal group, years of education or self-esteem have positive effects, while age or retirement status have negative effects when controlling for other factors. For the near-normal group, being married, or perceived financial insecurity create lower QoL levels, while higher self-esteem increases QoL levels. For the above-normal group, being widowed, employed, or retired have positive effects on QoL, when controlling for other variables. Third, even among elderly with high allowances, the effects of health status and family relationship are significant determinants that explain QoL levels. This result suggests that, for te elderly, poor health status and poor family relationships severely decrease QoL in later life, regardless of economic condition.