• 대한정형도수물리치료학회지
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• 제9권2호
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• pp.47-58
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• 2003

To closely examine the effects of the massage treatment as one method of curing hypertension by exploring the effects that one-time circulation-centered massage has on a hypertensive's blood pressure, this study selected as the subject ten among fifty-year-old essential hypertensives visiting N clinic, and measured and compared their blood pressures before and after I gave them massage. After stabilizing them, I measured their blood pressures. In their prone and supine postures, I gave them rubbing massage for twenty minutes from positions proximal to their hearts to ones distal from their hearts to help their artery circulation and circulation-centered stroking massage for ten minutes from positions distal from their hearts to ones proximal to their hearts to help their vein circulation. After the massage, I had them rest for five minutes and measured their blood pressures. Regarding each item analyzed, I calculated the mean and standard deviation before and after the massage. The difference before and after the massage was tested by corresponding t-test and the level of significance was made p<0.05. The findings are as follows. First, systolic pressure was $157.70{\pm}7.48$ before the massage and $143.00{\pm}9.39$, which is less than before the massage, after the massage, showing statistically significant difference (p<.05). Secondly, diastolic pressure was $97.80{\pm}6.56$before the massage and $95.20{\pm}5.18$, which is less than before the massage, after the massage, not showing statistically significant difference (p<.05).

• 구강회복응용과학지
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• 제22권3호
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• pp.211-220
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• 2006

Need of porcelain-repair system is largely demanding as dental porcelain restorations are increased in clinical dentistry. This study investigated shear bond strength of commercial porcelain-repair systems on dental porcelain and their reliability. Experimental groups were as follows; Group A Super Bond C&B, Group B Porcelain repair kit, Group C Ceramic repair, and Group D Spectrum system as a control. Porcelain disks were fired and embedded in epoxy resin. Porcelain surface were ground using 220 grit SiC disk, then cleaned in ultrasonic bath. Then porcelain specimens were treated with each repair system. A clear polystyrene cylinder 3.5 mm in internal diameter was filled with composite resin. Then the resin cylinder was polymerized with a visible light curing unit. Thirty one specimens at each group were prepared and stored at $37^{\circ}C$ distilled water for 48 h. Specimens were tested in an Instron testing machine according to ISO TR 11405. Mean shear bond strength and standard deviation of each group was $15.7{\pm}4.1MPa$ (Group A), $12.8{\pm}4.9MPa$ (Group B), $7.2{\pm}3.0MPa$ (Group C) and $9.6{\pm}2.2MPa$ (Group D). ANOVA and Tukey HSD post-hoc test showed that there were significant differences between groups (p<0.05). Data of bond strength were analyzed with two-parameter Weibull distribution. Confidence interval of Weibull modulus (m-parameter) at 95% of Group A (3.5-6.3) and Group D (3.6-6.0) were significantly higher than Group B (2.2-3.7) and Group C (2.0-3.4). There was little correlation between mean shear bond strength and Weibull modulus. Results indicated that acid-etching of porcelain surface increased porcelain-resin shear bonding strength.

• 한국농공학회지
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• 제16권4호
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• pp.3545-3554
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• 1974

The objective of this study was to investigate the characteristics of the evaporation rate, the plastic shrinkage and the compressive strength of concrete exposed to a rapid evaporation environment immediately after casting. Drying of concrete were conducted under a controlled chamber in which the temperature was mainfoimed at 30 ${\pm}$1$^{\circ}C$, the relative humidity 22 ${\pm}$1 percent, and the wind velocity 7 ${\pm}$1 m/sec. The compressive strength of concrete was tested after 28 days of standard curing. The results obtained are as follows: 1. The evaporation rate was the highest at the very beginning, was decreased as the drying progresses, and was kept almost constant after 6 hours. 2. The shrinkage of concrete was changed in three different rates for the concrete mixture having its slump vallue between 3.0cm and 7.5cm. 3. The plastic shrinkage was ended within 5 or 6 hours after casting, regardless of the water cement ratio. 4. The shrinkage was increased within the limit of slump values between 3.0cm and 7.5cm as the water-cement ratio was increased. 5. The evaporation was kept on even after the plastic shrinkage was ended. 6. Within the limit of good workability (slump value between 4.5cm and 7.5cm), the compressive strength of concrete was increased when the shrinkage rate was slow but it was decreased when the rate was rapid 7. From the result of this study it is recommended that (1) the water-cement ratio should be less as long as the workability of concrete is allowable; (2) the evaporation should be prevented at least for 4 hours after casting concrete.

• Environmental Engineering Research
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• 제21권1호
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• pp.15-21
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• 2016

Magnesium potassium phosphate cement (MKPC) is an effective agent for solidification/stabilization (S/S) technology. To further explore the mechanism of the S/S by MKPC, two kinds of Cd including $Cd(NO_3)_2$ solution (L-Cd) and municipal solid waste incineration fly ash (MSWI FA) adsorbed Cd (S-Cd), were used to compare the effects of the form of heavy metal on S/S. The results showed that all the MKPC pastes had a high unconfined compressive strength (UCS) above 11 MPa. For L-Cd pastes, Cd leaching concentration increased with the increase of Cd content, and decreased with the increase of curing time. With the percentage of MSWI FA below 20%, S-Cd pastes exhibited similar Cd leaching concentrations as those of L-Cd pastes, while when the content of MSWI FA come up to 30%, the Cd leaching concentration increased significantly. To meet the standard GB5085.3-2007, the highest addition of S-Cd was 30% MSWI FA (6% Cd contained), with the Cd leaching concentration of 0.817 mg/L. The S/S of L-Cd is mainly due to chemical fixation, and the hydration compound of Cd was $NaCdPO_4$, while the S/S of S-Cd is due to physical encapsulation, which is dependent on the pore/crack size and porosity of the MKPC pastes.

• 디지털융복합연구
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• 제13권1호
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• pp.555-562
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• 2015

본 연구에서는 남북한의 심리적 통일방안의 중요성과 그 구체적 실현 방법, 남북한 정신건강의 현황과 문제점에 대해 살펴보았다. 지금까지 남북통일에 대해 김대중의 남북연방제와 3단계 통일론 등 여러 주장과 연구들이 제시되었다. 본 연구에서는 남북한의 이질성과 동질성, 북한주민의 심리사회적 특성과 정신건강, 남북한의 심리학적 통일에 대한 기존의 심리학적 방안과 연구, 한국의 정신보건 현황 등을 개관했다. 남북한 통일의 문제는 점진적으로든 갑작스럽든 우리민족에게 필연적으로 다가올 수 밖에 없는 역사의 과정이라 할 수 있다. 남북한 통일에 대한 정치경제적 준비도 중요하지만, 분단 60여년의 심리적 상처와 고통을 치유할 수 있는 심리적 차원의 대비와 연구도 매우 중요하다. 향후 남북한 통일에 대비한 정신보건 정책 마련과 제도개선, 탈원화와 지역사회 통합을 강조하는 세계적인 정신보건 기준이나 OECD 권고에 부응하기 위한 각고의 노력이 필요한 상황이다. 본 연구의 의의와 한계점, 향후 연구방향이 논의되었다.

• Restorative Dentistry and Endodontics
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• 제39권4호
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• pp.296-302
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• 2014

Objectives: It is difficult to achieve adhesion between resin cement and zirconia ceramics using routine surface preparation methods. The aim of this study was to evaluate the effects of $CO_2$ and Er:YAG laser treatment on the bond strength of resin cement to zirconia ceramics. Materials and Methods: In this in-vitro study 45 zirconia disks (6 mm in diameter and 2 mm in thickness) were assigned to 3 groups (n = 15). In control group (CNT) no laser treatment was used. In groups COL and EYL, $CO_2$ and Er:YAG lasers were used for pretreatment of zirconia surface, respectively. Composite resin disks were cemented on zirconia disk using dual-curing resin cement. Shear bond strength tests were performed at a crosshead speed of 0.5 mm/min after 24 hr distilled water storage. Data were analyzed by one-way ANOVA and post hoc Tukey's HSD tests. Results: The means and standard deviations of shear bond strength values in the EYL, COL and CNT groups were $8.65{\pm}1.75$, $12.12{\pm}3.02$, and $5.97{\pm}1.14MPa$, respectively. Data showed that application of $CO_2$ and Er:YAG lasers resulted in a significant higher shear bond strength of resin cement to zirconia ceramics (p < 0.0001). The highest bond strength was recorded in the COL group (p < 0.0001). In the CNT group all the failures were adhesive. However, in the laser groups, 80% of the failures were of the adhesive type. Conclusions: Pretreatment of zirconia ceramic via $CO_2$ and Er:YAG laser improves the bond strength of resin cement to zirconia ceramic, with higher bond strength values in the $CO_2$ laser treated samples.

• 한국지반환경공학회 논문집
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• 제20권5호
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• pp.47-55
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• 2019

본 연구에서는 토양의 종류에 따라 친환경고화재인 E.S.B.(Eco Soil Binder)를 사용하여 혼합토의 강도특성과 활용목적에 따른 흙 포장의 기초자료를 제공하고자 한다. 연구에 사용된 토양은 우리나라 주변에서 흔히 채취되는 화강풍화토로 토질분류법에 의한 SW, SP, SC로 구분된다. 일축압축강도 시험을 위한 공시체는 지름 50mm, 높이 100mm의 크기로 혼합토 중량대비 E.S.B.의 혼합비율을 5%, 10%, 15%, 20%, 25%, 30%로 변화시키고 각 조건에 따라 다짐도를 90%, 100%를 적용하고 재령기간 3, 7, 28일에 따른 일축압축강도 특성을 분석하였다. 또한 흙 포장 기준강도와 일축압축강도의 강도비를 산정하여 최적의 E.S.B.혼합비율을 결정하고 ACI209R의 추정식을 활용한 일축압축강도의 현장 적용성을 평가하였다.

• 한국건축시공학회지
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• 제19권5호
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• pp.449-456
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• 2019

최근 비정형 건축물의 비중이 증가함에 따라 거푸집 재사용이 불가하여 건설폐기물이 증가하고 있는 추세이다. 또한 비정형 건축물 건축 시 생산자의 숙련도에 따라 비정형 패널의 품질이 결정되며 이에 따른 정확한 공사비 측정불가 및 인건비 증대라는 문제점이 있다. 본 연구는 이러한 비정형 건축물의 문제점을 보완하기 위하여 오차율이 적고 작업성이 좋은 최적의 배합을 찾는 것을 목표로 실험을 진행한다.

• Computers and Concrete
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• 제27권4호
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• pp.333-341
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• 2021

Steel slag, an industrial reject from the steel rolling process, has been identified as one of the suitable, environmentally friendly materials for concrete production. Given that the coarse aggregate portion represents about 70% of concrete constituents, other economic approaches have been found in the use of alternative materials such as steel slag in concrete. Unfortunately, a standard framework for its application is still lacking. Therefore, this study proposed functional model equations for the determination of strength properties (compression and splitting tensile) of steel slag aggregate concrete (SSAC), using gene expression programming (GEP). The study, in the experimental phase, utilized steel slag as a partial replacement of crushed rock, in steps 20%, 40%, 60%, 80%, and 100%, respectively. The predictor variables included in the analysis were cement, sand, granite, steel slag, water/cement ratio, and curing regime (age). For the model development, 60-75% of the dataset was used as the training set, while the remaining data was used for testing the model. Empirical results illustrate that steel aggregate could be used up to 100% replacement of conventional aggregate, while also yielding comparable results as the latter. The GEP-based functional relations were tested statistically. The minimum absolute percentage error (MAPE), and root mean square error (RMSE) for compressive strength are 6.9 and 1.4, and 12.52 and 0.91 for the train and test datasets, respectively. With the consistency of both the training and testing datasets, the model has shown a strong capacity to predict the strength properties of SSAC. The results showed that the proposed model equations are reliably suitable for estimating SSAC strength properties. The GEP-based formula is relatively simple and useful for pre-design applications.

• 대한건축학회논문집:구조계
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• 제35권7호
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• pp.179-186
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• 2019

Air lime is a traditional building material of Korea. It had been used in roofs, walls, floors and masonry joints of traditional buildings until the advent of Portland cement. However, due to its low strength and durability, the lime is currently avoided as a repair or restoration material for the preservation of architectural heritage. Furthermore, due to the current practice of using hydraulic materials such as Portland cement, understanding of the material characteristics of air lime is very poor in practice. In this context, this study intended to improve the mechanical properties of the air lime mortar by reducing water contents, and also the carbonation reaction of the mortar was quantitatively evaluated to clearly understand the characteristics of this material. Accordingly, air lime mortar with a water-to-binder ratio of 0.4 was manufactured using polycarboxylate-type superplasticizer. During the 7 days of sealed curing period, the mortar did not harden at all. In other words, there was no reaction required for hardening since it could not absorb carbon dioxide from the atmosphere. However, once exposed to the air, the compressive strength of the mortar began to rapidly increase due to the carbonation reaction, and the strength increased steadily until the 28th day; after then, the strength development was significantly slowed down. On the 28th day, the mortar exhibit a compressive strength of about 5 MPa, which is equivalent to the European standard regarding strength of hydraulic lime used for preservation of architectural heritage.