• 폴리머
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• 제32권5호
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• pp.433-439
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• 2008

고분자 소재에 평판형 플라즈마 전처리 방식을 적용시켜 polyurethane foam(density : 0.27)과 rubber (butadiene rubber) 소재 표면의 접촉각 및 접착력을 향상시켰다. 플라즈마 반응기의 최적의 반응조건을 조사하기 위해서 전처리기류(질소, 아르곤, 산소, 공기), 기류의 유량($30{\sim}100\;mL/min$), 그리고 전처리 시간($0{\sim}30\;s$) 등을 변화시켜 전처리하고 polyurethane foam의 경우 진공식 플라즈마처리 방식과 상호 비교하였다. 분위기 기류인 $N_2$의 유량을 100 mL/min로 설정 후 polyurethane foam은 10 s, rubber는 3 s 동안 전처리 했을 때 가장 높은 접착박리강도를 나타내었다. 전처리 후 소재의 표면 변화는 SEM과 ATR-FTIR을 이용하여 측정하였다. 결과적으로 평판형 플라즈마 조작 방식에 의한 처리로 소재 표면의 젖음성과 접착박리강도가 개선되었음을 확인하였다.

• 한국지반공학회논문집
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• 제28권7호
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• pp.67-75
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• 2012

교량기초의 지지층인 조밀한 화강풍화토 지반에서 얕은 기초의 침하에 대한 크기효과를 평가하고자 하였다. 이를 위해 지반조건이 유사한 2개 현장에서 재하판 크기를 다르게 하여 평판재하시험을 수행하였다. 시험결과 재하판 하부 및 주변 지반의 파괴는 관찰되지 않았으며 하중 증가에 따라 침하가 비례하여 증가하였다. 이러한 결과는 대상지반에 지지되는 기초의 안정성 또는 사용성은 침하가 지배하는 것을 의미한다. 침하에 대한 기초크기 효과는 압력-침하곡선의 기울기로 표현되는 지반반력계수와 기초폭의 관계로 표현하였다. 기존에 제안된 관계식과 비교해 볼 때 본 실험결과는 크기효과가 더 크게 나타나며, 이는 기존에 제안된 관계식은 조밀한 화강풍화토 지반에 지지된 기초의 침하를 과소평가할 수 있음을 나타낸다.

• 한국재료학회지
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• 제30권8호
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• pp.426-434
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• 2020

The performance characteristics of a lead acid battery are investigated with the content of Sodium Perborate Tetrahydrate (SPT, NaBO₃·4H₂O) in a positive plate active material. SPT, which reacts with water to form hydrogen peroxide, is applied as an additive in the positive plate active material to increase adhesion between the substrate (positive plate) and the active material; this phenomenon is caused by a chemical reaction on the surface of substrate. A positive plate with the increasing content of SPT is prepared to compare its properties. It is confirmed that the oxide layer increases at the interface between the substrate and the active material with increasing content of SPT; this is proven to be an oxide layer through EDS analysis. Battery performance is confirmed: when SPT content is 2.0 wt%, the charging acceptance and high rate discharge properties are improved. In addition, the lifetime performance according to the Standard of Battery Association of Japan (SBA) S0101 test is improved with increasing content of SPT.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1994년도 추계 학술발표 강연 및 논문 개요집
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• pp.125-126
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• 1994

The chemorheological changes and kinetics during curing reaction of an silica filled epoxy system (DGEBA with curing agent Polyxoypropylenediamine) were investigated. This study concentrates on the influence of silica on the reaction kinetics and rheological behavior of the eopxy system. The concentration of the filler was varied 0~200phr. Curing behavior of the silica filled epoxy system was measured at various heating rates with DSC. Conversion was also measured by integrating the obtained DSC curve and Kinetic parameters measured by using the nonlinear regression method. DSC experiments showed that the presence of silica was found to accelerate the progress of the curing reaction and of reduce the heat of reaction compared with that of unfilled epoxy systems . Rheological experiments were conducted on a Physica by using a disposable parallel plate fixture. Material properites were measured such as the elastic modulus(G′), the loss modulus(G"), the loss tangent(tan $\delta$), and the viscosity was at the initial stahe, and the more the silica filler was added, and the lower the gel temperature was in the epoxy system. In this study it is concluded that the curing of the silica filled epoxy system was found to be accelerated, as silica was added to the epoxy compound.

• Korean Chemical Engineering Research
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• 제49권5호
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• pp.652-656
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• 2011

양극산화에 의해 티타니아 나노튜브(TNT) 박막과 나노필름(TNF) 박막을 제조하여 이의 광촉매 반응특성을 연구하였다. TNT 박막이 형성된 티타늄 판에 자외선을 조사하여 용액 내 메틸렌블루의 분해율을 측정하였다. TNT의 길이가 증가할수록 광촉매(PC) 반응에 의한 메틸렌블루 분해율이 증가하였다. 광전자의 재결합을 억제하기 위해 포텐셜을 가해준 광전자촉매(PEC) 반응에서는 전반적으로 분해율이 상승하였으며, 길이에 따른 분해율 차이가 상대적으로 작았다. 튜브형태가 아닌 필름형태의 TNF는 TNT에 비해 낮은 분해율을 나타내었으며, 광촉매 반응에서 분해율의 차이가 더 크게 나타났다.

• 대한치과교정학회지
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• 제10권1호
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• pp.37-43
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• 1980

This study was undertaken to assess the effects of demethylchlortetracycline on bone growth of mandibular symphyseal region in rats. Demethylchlortetracycline at 30mg/kg body weight, respectively, were daily administered by mouth to the sewen female rats from 10th day of pregnancy to 13th day. Thirty six new-born rats from these experimental animals were used for histological examination at 1, 5, 10, 15, 20, 25 and 30 days. All these new-born rats were killed by an overdose of ether. Mandibular bodies were removed and fixed in $10\%$ neutral formalin,. Carney and aceton. Specimens were embedded, sectioned and stained with H-E, Van Gieson, PAS and prepared for alkaline phosphatase. The results were as follows; 1. Until erupting of incisors, hyaline cartilage was located in relatively large symphyseal space, but bone trabeculae of ossifying area at incisal side were arranged irregularly in experimental group. 2. During this period, PAS reaction was moderately positive, but alkaline phosphatase reaction was slightly positive. 3. By erupting or incisors, symphyseal space appeared narrower like control group, but alkaline phosphatase reaction tended to slow down. 4. By erupting of molars, symphyseal space appeared muck narrower, and cartilane plate was reduced and aealed off like control group. Alkaline phosphatase reaction tended to slow down severely.

• Tribology and Lubricants
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• 제13권4호
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• pp.60-65
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• 1997

The tungsten disulfide $(WS_2)$ solid lubricant was synthesized by two different reaction processes, i.e., the reaction between $CS_2$ gas phase and solid $WO_3$powder, and the vapour phase transport method of tungsten and sulfur in a high vacuum. The chemical and physical characteristics of synthesized $WS_2$powder were analyzed in terms of the average particle size, morphology, crystalline phase etc. in comparison with those of commercial $WS_2$powder. The solid $WO_3$ powder with the average size of 0.2 ${\mu}{\textrm}{m}$ was reacted with $CS_2$gas flowed with$N_2$or 96%$N_2{\times}4%H_2$forming gas for 36 h and 24 h at 90$0^{\circ}C$ respectively. $WS_2$ crystalline phase was then formed through the intermediate phase of .$W_{20}O_{58}$ In the case of vapour phase transport method, the 3.5 wt% iodine was added as a vapour transport reagent into the composition of tungsten and sulfur powders maintaining a constant molar ratio of W:S=1:2.2. The mixture was then heat treated at 85$0^{\circ}C$ for 2 weeks in vacuum. The reaction product obtained showed the average size of 12 ${\mu}{\textrm}{m}$ and the hexagonal plate shape of typical solid lubricant with 2H-$WS_2$crystalline phase.

• The Journal of Korean Physical Therapy
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• 제34권4호
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• pp.175-180
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• 2022

Purpose: Leg length discrepancy causes the posture deformation, gait asymmetry, and lower back pain. The purpose of this study is to investigate the correlation among functional leg length discrepancy (FLLD), muscle activity, muscle contraction onset time and vertical ground reaction force (vGRF) during simple lifting task. Methods: Thirty-nine subjects participated in this study. FLLD was measured from the umbilicus to medial malleolus of left and right leg using a tape. The subjects performed to lift a 10 kg box from the floor to chest. The muscle activity and muscle contraction onset time of rectus abdominis, erector spinae and rectus femoris was measured using EMG system and vGRF was measured by two force plate. Pearson correlation was used to fine out the correlation among FDDL, muscle activity, muscle contraction onset time and vGRF during simple lifting task. Results: Correlation between FLLD and difference of muscle activity of short-long side was very high (r>0.9) during simple lifting task. Correlation between FLLD and difference of muscle contraction onset time of short-long side was very high (r>0.9) during simple lifting task. And correlation between FLLD and difference of vGRF of short-long side was high (r>0.7) during simple lifting task. Conclusion: This study suggests that there is high correlation between FLLD and muscle activity, muscle contraction onset time, and ground reaction force during simple lifting task. Therefore, FLLD could negatively affect the postural balance.

• 대한치과보철학회지
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• 제30권2호
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• pp.155-166
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• 1992

In dentistry, precious metal alloys are, mainly due to economic factors, increasingly displaced by alternatives containing Ni-Cr-Co. There are some reports where hypersensitive reactions to Ni-Cr-Co alloys are presented and discussed. The reactions reported vary from mucosa contact stomatitis to generalized dermatitis without any oral mucosal reaction. The purpose of this study was to investigate the incidence of nickel, chrome, cobalt and copper, and to know whether subjects with positive skin reaction to nickel would also demonstrate adverse intraoral reaction to a non-precious metal nickel. The patch tests were performed in 81 subjects(male 39, female 42) and nickel sulfate 5% aq., potassium bichromate 0.5% at., cobalt chloride 2% aq., & copper sulfate 1% aq., were used for test allergens. And then the intraoral tests were performed in 16 subjects, 8 subjects with positive allergic skin reaction to nickel and 8 subjects with negative allergic skin reaction. A pure metallic nickel plate was attached to the buccal side of the upper second premolar. The results are as follows : 1. The frequency of nickel sensitivity was 9.9% (2 men, 6 women), cobalt was 4.9% (1 man, 3 women), and chrome was 2.5% (2 men) respectively and there was no positive reaction to copper 2. The positive reactions were 8 of 23 (34.8%) with a history of jewelry allergic reactions and 3 of 58 (5.1%) without a history of jewelry allergic reactions. 3. Three of 8 subjects with positive skin reaction. gave reactions to the metal plates.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.12-19
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• 2006

It is positively necessary to study on the stiffness of a 13degree-type impact tester in order to improve the fracture prediction of impact testing in wheels using FE(finite-element) analysis. The 13degree-type impact tester consists of an impact striker, a wheel fixer, a steel plate, and four cylindrical rubbers. Important parts of the tester are the steel plate and four cylindrical rubbers which play a role of absorbing impact energy during impact testing. Because of these buffers, the RF(reaction force) variation of the lower part in the 13degree-type impact tester showed the tendency like a damped harmony oscillation during impact testing. In order to investigate the stiffness of a 13degree-type impact tester, this work measured each stiffness of a steel plate and cylindrical rubbers. The stiffness of a cylindrical rubber was measured using a compressive tester. On the other hand, the stiffness of a steel plate was predicted by simulating experimental method using FE analysis.