• 한국세라믹학회지
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• 제31권10호
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• pp.1107-1114
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• 1994

Although various theories have been presented on the mechanism of setting retardation of plaster in addition to organic admixtures. The purpose of this paper is that Hydration studies of plaster of paris in the presence of carboxylic acids under alkalinity are examined in the coordination chemistry. Setting of plaster of paris is retarded by the addition of carboxylic acids except oxalic acid. And setting of plaster of paris contained 5 wt% of Ca(OH)2 is also retarded by the addition of above-mentioned carboxylic acids. The degree of retarding effect under alkalinity is found to be a function of the number of the functional group and the length of carbon chain of carboxyl acids. These reasons are attributed to the soluble complex formation, that is calcium complex formation between calcium ion and carboxylic acids. The author's proposal was confirmed by the results of electrical conductivity measurement. The formation of calcium complex was surpported by IR spectra.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.631-634
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• 2005

This paper discussed the influence of addition of aqueous additives such as various beverage and detergent on the properties of concrete during placement by workmen's mistake. Slump and air content were not highly affected by the addition of aqueous additives, while addition of detergent led to an remarkable increase in air content due to interfacial activated ingredient in detergent. For setting time, lactic-acid fermented milk exhibited a longest setting delay and in order of coffee and soda. Concrete containing setting retarding beverage had higher compressive strength than control concrete at 7 and 28days. Concrete containing detergent exhibited strength loss due to the presence of larger amount of air content.

• 약학회지
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• 제49권5호
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• pp.380-385
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• 2005

The aim of this study is to investigate the effects of verapamil on the pharmacokinetics of tamoxifen following oral administration of tamoxifen with verapamil to rats. Tamoxifen (10 mg/kg) was administered orally in the presence or absence of verapamil (1, 3 or 6 mg/kg). Compared to the control group (given tamoxifen alone), the presence of verapamil significantly (p<0.05 by 1 mg/kg, p<0.01 by 3 and 6 mg/kg) increased the areas under the plasma concentration-time curve (AUC) and the peak concentrations ($C_{max}$) of tamoxifen. Consequently, the relative bioavailability ($RB\%$) of tamoxifen with verapamil was 1.6-2.1 fold higher than that of the control. But the time to reach peak concentration ($T_{max}$) and the terminal half-life ($t_{1/2}$) of tamoxifen were not altered significantly in the presence of verapamil. The increased AUC and $C_{max}$ of tamox­ifen in the presence of verapamil might be associated with the inhibition by verapamil of the P-glycoprotein and the first­pass metabolizing enzyme CYP3A4 in small intestinal mucosa. The drug interaction should be taken into consideration when tamoxifen is used to the patient with verapamil in the clinical setting.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1590-1599
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• 2016

The installation of distributed generation (DG) in the electrical networks has numerous advantages. However, connecting and disconnecting of DGs (CADD) leads to some problems in coordination of protection devices due to the changes in the short circuit levels in the different points of network. In this paper, an adaptive method is proposed based on available setting groups (SG) of relays. Since the number of available SG is less than possible CADD states, a classifying index (CI) is defined to categorize the several states in restricted setting groups. Genetic algorithm (GA) with a suitable objective function (OF) is used as an optimization method for the classification. After grouping, a modified coordination method is applied to achieve optimal coordination for each group. The efficiency of the proposed technique is demonstrated by simulation results.

• 방송공학회논문지
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• 제19권1호
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• pp.44-55
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• 2014

3D 영상의 궁극적인 목표는 부정적 경험을 최소화하면서 동시에 깊이감 정보를 추가하여 얻을 수 있는 더 큰 몰입감, 사실감과 같은 긍정적 경험을 극대화시키는 것이다. 본 연구는 3D 카메라의 컨버전스 레벨을 다르게 조절했을 때 나타나는 깊이감 차이가 긍정적 그리고 부정적 경험에 어떠한 영향을 미치는지 살펴보고, 최적의 파라미터를 찾는 것을 목적으로 하며 이를 위해 3D 뮤직 비디오를 5개의 다른 컨버전스 레벨에 따라 제작하고 100명을 대상으로 실험을 진행하였다. 연구 결과는 깊이감에 따라 프레즌스와 프레즌스의 하위차원인 공간관여, 몰입실재감 등에서 유의미한 차이가 있었으며, 지각된 특성과 지각된 특성의 하위차원인 깊이 지각감, 화면 전달감, 모양 지각감, 공간 확장감 역시 유의미한 차이가 있었다. 또한 부정적 경험 요인인 피로감과 부자연스러움도 그룹에 따라 각각 차이가 있음을 보여 주었다. 본 연구결과는 3D 영상 제작 시 카메라의 폭주각은 피사체 위치에서의 폭주각보다 $0.17^{\circ}$ 작게 하여 화면보다 18.66cm 돌출된 영상을 제작하는 것이 영상에 대한 프레즌스와 지각된 특성은 높이고 부정적 경험은 줄여주는 최적의 영상경험을 제공하는 것으로 나타났다.

• 한국임상약학회지
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• 제18권1호
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• pp.6-10
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• 2008

This study investigated the effect of long-term administration of pioglitazone on the pharmacokinetics of verapamil in rats. Pharmacokinetic parameters of verapamil were determined after oral administration of verapamil (9 mg/kg) in rats coadministered pioglitazone (0.5 mg/kg) or pretreated with pioglitazone (0.5 mg/kg) for 3 and 9 days. Compared to oral control group, the presence of pioglitazone significantly (p<0.05) increased the area under the plasma concentration-time curve (AUC) of verapamil by 48.6% (coad), 61.1% (3 days) and 56.5% (9 days), and the peak concentration($C_{max}$) by 65.1% (coad), 76.8% (3 days) and 66.4% (9 days). The absolute bioavailability (AB%) of verapamil was significantly (p<0.05) higher by 6.2% (coad), 6.7% (3 days), 6.5% (9 days) compared to control (4.2%), and presence of pioglitazone was no significant change in the terminal half-life ($t_{1/2}$) and the time to reach the peak concentration($T_{max}$) of verapamil. Our results indicate that pioglitazone significantly enhanced oral bioavailability of verapamil in rats, implying that presence of pioglitazone could be effective to inhibit the CYP3A4-mediated metabolism of verapamil in the intestine. Drug interactions should be considered in the clinical setting when verapamil is coadministrated with pioglitazone.

• Imaging Science in Dentistry
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• 제51권1호
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• pp.1-7
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• 2021

Purpose: The aim of this study was to assess artifacts generated in cone-beam computed tomography (CBCT) of 3 types of dental implants using 3 metal artifact reduction (MAR) algorithm conditions (pre-acquisition MAR, post-acquisition MAR, and no MAR), and 2 peak kilovoltage (kVp) settings. Materials and Methods: Titanium-zirconium, titanium, and zirconium alloy implants were placed in a dry mandible. CBCT images were acquired using 84 and 90 kVp and at normal resolution for all 3 MAR conditions. The images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the intensity of artifacts for each combination of material and settings. A 3-factor analysis of variance model with up to 3-way interactions was used to determine whether there was a statistically significant difference in the mean intensity of artifacts associated with each factor. Results: The analysis of all 3 MAR conditions showed that using no MAR resulted in substantially more severe artifacts than either of the 2 MAR algorithms for the 3 implant materials; however, there were no significant differences between pre- and post-acquisition MAR. The 90 kVp setting generated less intense artifacts on average than the 84 kVp setting. The titanium-zirconium alloy generated significantly less intense artifacts than zirconium. Titanium generated artifacts at an intermediate level relative to the other 2 implant materials, but was not statistically significantly different from either. Conclusion: This in vitro study suggests that artifacts can be minimized by using a titanium-zirconium alloy at the 90 kVp setting, with either MAR setting.

• Asian Pacific Journal of Cancer Prevention
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• 제15권5호
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• pp.2287-2290
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• 2014

Background: In the past few years, a considerable number of preclinical studies have been proposed metformin as a potential anticancer agent, but some of these studies suffer from a number of methodological limitations such as assessment of cytotoxicity in the presence of supraphysiological glucose concentrations or applying suprapharmacological levels of the drug. These objections have limited the translation of published preclinical data to the clinical setting. The present study aimed to investigate direct anticancer effects of metformin on different molecular subtypes of breast cancer with pharmacological concentrations and under normoglycemic conditions in vitro. Materials and Methods: Breast cancer cell lines from luminal A, luminal B, ErbB2 and triple-negative molecular subtypes were treated with a pharmacological concentration of metformin (2mM) at a glucose concentration of 5.5mM. Time-dependant cell viability was assessed by dye exclusion assay. MTTbased cytotoxicity assays were also performed with metformin alone or in combination with paclitaxel. Results: Metformin did not show any growth inhibitory effects or time-dependant cytotoxicity on breast cancer cell lines in the presence of normal glucose concentrations at the therapeutic plasma level. No augmentation of the antineoplastic properties of paclitaxel was apparent under the tested conditions. Conclusions: Metformin is probably unable to exert cytotoxic or cytostatic effects on breast cancer subtypes at pharmacological concentrations and normal plasma glucose levels. These results highlight the importance of establishing a higher steady-state plasma concentration of metformin in the clinical setting for assessment of anticancer effects in normoglycemic patients.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.502-512
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• 2017

The presence of DGs in power system networks tends to negatively affect the protective relays coordination. The proposed method introduces an approach to minimize the numbers of relays that acquire new settings on contrary to their original settings (case without DG), to achieve relays coordination in case of adding DG, since relays coordination with minimum number of relays of re-adjusted settings represents economical target, especially in networks containing mixture of electromechanical and adaptive digital relays. The scheme decides the possible minimum number of re-adjusted relays and their locations in an optimum manner to achieve proper relays coordination in case of adding DGs. The proposed approach is divided into two successive phases; the first phase is stopped when the first relays coordination solution is achieved. The second phase increases the possibility to keep higher number of relays at their original settings than that obtained in first phase through achieving multi solutions of relays coordination. The proposed approach is implemented and effectively tested on the well-known IEEE-39 bus test system.

• Journal of the Korean Statistical Society
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• 제33권1호
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• pp.79-97
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• 2004

We propose a permutation approach to the classic Behrens-Fisher problem of comparing two means in the presence of unequal variances. It is motivated by the observation that a paired test is valid whether or not the variances are equal. Rather than using a single arbitrary pairing of the data, we average over all possible pairings. We do this in both a parametric and nonparametric setting. When the sample sizes are equal, the parametric version is equivalent to referral of the unpaired t-statistic to a t-table with half the usual degrees of freedom. The derivation provides an interesting representation of the unpaired t-statistic in terms of all possible pairwise t-statistics. The nonparametric version uses the same idea of considering all different pairings of data from the two groups, but applies it to a permutation test setting. Each pairing gives rise to a permutation distribution obtained by relabeling treatment and control within pairs. The totality of different mean differences across all possible pairings and relabelings forms the null distribution upon which the p-value is based. The conservatism of this procedure diminishes as the disparity in variances increases, disappearing completely when the ratio of the smaller to larger variance approaches 0. The nonparametric procedure behaves increasingly like a paired t-test as the sample sizes increase.