• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.7
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• pp.469-473
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• 2003

The effect of photoquenching on infrared image of the EL2 center in semi-insulating(S.I.) GaAs has been studied using near infrared transmission techniques. Particular interest is devoted to as-grown and annealed samples of undoped S.I. GaAs. It is found that the quenching mechanism is different in each sample and also the quenching rate is dependent on the materials and the quenching temperature which is somewhat inconsistent with other existing publications.

• Research in Mathematical Education
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• v.6 no.2
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• pp.171-182
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• 2002

Students approach mathematical problem solving in fundamentally different ways, particularly problems requiring conceptual understanding and complicated strategies such as mathematical word problems. The main objective of this study is to compare students' performance with different cognitive styles (Field-dependent vs. Field-independent) on mathematics problem solving, particularly, in word problems. A sample of 180 school girls (13-years-old) were tested on the Witkin's cognitive style (Group Embedded Figures Test) and two mathematics exams. Results obtained support the hypothesis that students with field-independent cognitive style achieved much better results than Field-dependent ones in word problems. The implications of these results on teaching and setting problems emphasizes that word problems and cognitive predictor variables (Field-dependent/Field- independent) could be challenging and rather distinctive factors on the part of school learners.

• Communications for Statistical Applications and Methods
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• v.28 no.2
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• pp.151-159
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• 2021

In this article, our interest is to estimate the association between consecutive gap times which are subject to interval censoring. Such data are referred as doubly interval censored data (Sun, 2006). In a context of serial event, an induced dependent censoring frequently occurs, resulting in biased estimates. In this study, our goal is to propose a Kendall's 𝜏 based association measure for doubly interval censored data. For adjusting the impact of induced dependent censoring, the inverse probability censoring weighting (IPCW) technique is implemented. Furthermore, a multiple imputation technique is applied to recover unknown failure times owing to interval censoring. Simulation studies demonstrate that the suggested association estimator performs well with moderate sample sizes. The proposed method is applied to a dataset of children's dental records.

• Communications for Statistical Applications and Methods
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• v.4 no.3
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• pp.787-793
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• 1997

It is well known that the assumption of independence is ofter not valid for real data. This phenomenon has been observed empirically by many prominent scientists. In this article the sensitivity of dependence on Bayes test of a sharp null hypothesis is considered. The robustness is considered with respect to the significant level and the prior probability on the null hypothesis.

• Journal of the Korean Statistical Society
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• v.22 no.1
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• pp.125-132
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• 1993

Large sample test of homogeneity for a panel of more than two seasonal autoregressive processes is derived and its limiting distribution is found. Detailed results are shown for the important special case that the seasonal and nonseasonal autoregressive components are both of order one.

• The Journal of Pediatrics of Korean Medicine
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• v.4 no.1
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• pp.1-17
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• 1990

?In order to investigate effects of Zanthoxyli Fructus (Sample-A) and Fagarae mandshuricae Fructus (Sample-B), experimental study was performed through observation on isolated - ileum analgesic, hypothermal, anti-pyretic, anti-inflammatory, capillary permeability, blood flow rate, blood pressure and respiratory works. The results were as follows; 1. In spontaneous movement of mice isolated-ileum, both samples were noted to have strong inhibitory action after temporary contraction, and to show antagonism against acetylcholine chloride and barium chloride. 2. Both samples were showed to have antihistamin work on guinea pig isolated-ileum 3. In analgesic work by the acetic acid method, only Fagarae mandshuricae Fructus was proved to have significant analgesic effect in mice. 4. Both sample groups indicated anti-pyretic and anti-inflammatory effect. 5. Both samples were noted to have inhibitory effect against capillary permeability ?rise in mice. ?6. Both samples were noted to have dose-dependent falling effect on blood pressure in rabbits.

• Applied Science and Convergence Technology
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• v.24 no.1
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• pp.22-26
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• 2015

The optical properties of InP/GaP short-period superlattice (SPS) structures grown at various temperatures from $400^{\circ}C$ to $490^{\circ}C$ have been investigated by using temperature-dependent photoluminescence (PL) and emission wavelength-dependent time-resolved PL measurements. The PL peak energy for SPS samples decreases as the growth temperature increases. The decreased PL energy of ~10 meV for the sample grown at $425^{\circ}C$ compared to that for $400^{\circ}C$-grown sample is due to the CuPt-B type ordering, while the SPS samples grown at $460^{\circ}C$ and $490^{\circ}C$ exhibit the significant reduction of the PL peak energies due to the combined effects of the formation of lateral composition modulation (LCM) and CuPt-B type ordering. The SPS samples with LCM structure show the enhanced carrier lifetime due to the spatial separation of carriers. This study represents that the bandgap energy of InP/GaP SPS structures can be controlled by varying growth temperature, leading to LCM formation and CuPt-B type ordering.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.2
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• pp.105-111
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• 1999

This paper presents experimental results on the electrical properties of hydrogenated amorphous carbon films(a-C:H) prepared by PECVD. DC conductance of a-C:H was measured as a function of temperatures in the range of 100 to 423K. We studied two a-C:H films: one was well explained by the Mott's Variable Range Hopping(VRH) rule, but the other sample did not follow it. However, the conduction data of second sample were well fitted to Shimakawa's Multi-Phonon Hopping(MPH) model according to which conductivity is proportional to $T^M$ with m=15-17. but, in our samples, m was 10-12. Also a-C:H showed several bias effects like relaxation of conductance, bias-dependent conductance and the change of conductance slope in 1n(${\sigma}{\sqrt{T}}$) vs. $T^{1/4}$ plot. In this study we interpret these data by bias-dependent detrapping model.

• Applied Science and Convergence Technology
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• v.25 no.4
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• pp.81-84
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• 2016

InP/InGaP quantum structures (QSs) grown on GaAs substrates by a migration-enhanced molecular beam epitaxy method were studied as a function of growth temperature (T) using photoluminescence (PL) and emission-wavelength-dependent time-resolved PL (TRPL). The growth T were varied from $440^{\circ}C$ to $520^{\circ}C$ for the formation of InP/InGaP QSs. As growth T increases from $440^{\circ}C$ to $520^{\circ}C$, the PL peak position is blue-shifted, the PL intensity increases except for the sample grown at $520^{\circ}C$, and the PL decay becomes fast at 10 K. Emission-wavelength-dependent TRPL results of all QS samples show that the decay times at 10 K are slightly changed, exhibiting the longest time around at the PL peak, while at high T, the decay times increase rapidly with increasing wavelength, indicating carrier relaxation from smaller QSs to larger QSs via wetting layer/barrier. InP/InGaP QS sample grown at $460^{\circ}C$ shows the strongest PL intensity at 300 K and the longest decay time at 10 K, signifying the optimum growth T of $460^{\circ}C$.

• The Korean Journal of Food And Nutrition
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• v.20 no.2
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• pp.114-119
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• 2007

Our research objective was to examine the in vitro biological activity of deer antler(Nogyong in Korean) extract, including the antioxidative, nitrite scavenging, and tyrosinase inhibitory effects, as well as the antithrombotic, and angiotensin I converting enzyme(ACE) inhibitory activities. The carbohydrate, protein, fat, and mineral contents of the deer antler were 7.6%, 65.3%, 3.2% and 23.9%, respectively. The electron donating ability(EDA) by the reduction of 2,2'-diphenyl-1-picrylhydrazyl(DPPH) was 67.1%, and the inhibition rate of lipid peroxidation by the thiocyanate method using linoleic acid was 92.1% in 100 mg/ml of extract. The nitrite scavenging effects were pH dependent, and were highest at pH 1.2 and lowest at pH 6.0. The sample inhibition rate against tyrosinase was above 64.0%. The platelet aggregation induced by ADP(adenosine-5'diphosphate) was inhibited up to 51.7%, and the inhibitory effect was dependent on the sample concentration. Lastly, the inhibition rate of ACE was 47.5% in 100 mg/ml of deer antler extract.