• 대한소아치과학회지
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• 제35권3호
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• pp.477-486
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• 2008

치과 임상에서는 여러 목적으로 Polymethyl methacrylate를 주성분으로 한 아크릴릭 레진이 사용되고 있으며, 특히 가철성 교정장치는 대부분 이것을 사용한다. 그러나 아크릴릭 레진은 중합이 완벽하게 이루어지지 않을 경우 인체에 악영향을 줄 수 있는 미반응 모노머가 레진에 잔존할 수 있다. 본 연구에서는 다양한 방법(온도, 압력, 수중 혹은 공기 중)으로 중합 조건과 시간을 달리 하여 교정용 아크릴릭 레진에서 발생하는 미반응 모노머의 용리량을 고성능 액체 크로마토그래피를 이용하여 정성 및 정량분석 하고자 하였다. 연구 결과, 모든 군에서 MMA를 제외한 다른 모노머는 용리되지 않았으며, 중합 방법에 따른 모든 실험군에서 미반응 모노머의 용리는 유의하게 감소하였고(P<0.05) 중합 방법을 한 가지만 사용하였을 때보다 2가지 이상 복합적으로 변화시켰을 때 모노머의 용리량이 더 감소함을 알 수 있었다. 또한 시간경과에 따라 모노머의 용리량이 유의하게 감소하여, 특히 1일 후 부터 급격한 감소를 보였다. 이상의 결과를 보아 중합 방법을 달리하였을 때 모노머의 용리량을 더 많이 감소시키고, 다른 중합 조건들도 복합적으로 사용하는 것이 용리량을 더 효과적으로 줄일 수 있을 것으로 생각된다. 그리고 중합 과정에서 온도, 수분, 압력의 조건을 강화하여 3일 이상 중합 시간을 가지는 것이 미반응 모노머의 용리량을 최소화할 수 있을 것으로 생각되었다.

• Composites Research
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• 제35권6호
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• pp.425-430
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• 2022

수소가스용 압력용기의 안전성 평가를 위해 다양한 내구성 시험이 요구된다. 고온 정압 시험은 고압(875 bar) 하에 고온(85℃ 이상)에서 장시간(1,000시간) 유지하여 수소 용기의 내구성을 시험하는 방법이며 승용차용 용기에 한정되어 있다. 하지만 대용량 수소버스용 용기와 관련된 고온 정압 시험의 국제 기준은 논의 초기 단계이며, 시험의 효율성 및 신뢰성 측면에서 가속시험 기준 제시 등의 현실적 보완이 필요하다. 본 연구에서는 수소버스용 내압용기의 고온 정압 시험 기준을 정립하기 위해 열적환경에 노출된 내압용기 복합재의 기계적 물성평가를 진행하였다. 복합재의 인장강도는 수지의 유리전이온도에 가까워질수록 수지의 열화로 인해 강도가 감소한다. 또한 장시간 유지 시 수지의 후경화로 인해 인장강도의 재상승을 확인할 수 있었다. 따라서 대용량 수소버스용 압력용기의 고온 정압 시험은 탄소섬유 복합재의 에폭시 수지 물성을 바탕으로 시험 조건을 설정해야 한다.

• 대한치과기공학회지
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• 제37권1호
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• pp.17-21
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• 2015

Purpose: In this study, Spreadability of denture adhesive in accordance with the saturation level of saliva, respectively, by using the resin plate and the glass was measured thickness and Spreadability. Methods: Examine the spreadability of denture adhesive in accordance with the saturation level of saliva, respectively, by using the resin plate and the glass was measured thickness and Spreadability. Also, by measuring the adhesive strength according to the amount of saliva, and the edentulous patients using denture adhesive and dry mouth patients attempt to provide clinical information of the denture adhesive. Therefore, by using the relatively low shrinkage cold curing resin, after fabricating specimen of plate form, for 7 days, it was immersed in water. Results: For the control group only denture adhesive, an artificial saliva for the experimental group were injected in $0.1m{\ell}$, $0.2m{\ell}$ and $0.3m{\ell}$ of the denture adhesive on the surface, experimental results of the investigation of the 10 times the tensile bond strength of the specimens in each group was obtained the following results. Conclusion: As the time to pressure increase in the same amount of saliva was found that the amount coming out of the denture adhesive, as the amount of saliva in the same pressure increase coming out of many denture adhesives. And the greater the pressure came out a lot of denture adhesives. Spreadability in measuring saliva contact with $0.1m{\ell}$ and $2m{\ell}$ and $3m{\ell}$ group pressured the diameter of the circular was the denture adhesive is small when compared to the group without adding the pressure of 2kg and 3kg put the saliva. The size of the circle is the same amount of saliva denture adhesive spread more pressure showed a greater increase.

• Design & Manufacturing
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• 제14권4호
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• pp.65-70
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• 2020

Partial reinforcement of sheet metal parts with CFRP patch is a technology that can realize ultra-lightweight body parts while overcoming the high material cost of carbon fiber. Performing these patchworks with highly productive press equipment solves another issue of CFRP: high process costs. The A-pillar is the main body part and has an undercut shape for fastening with other parts such as roof panels and doors. Therefore, it is difficult to bond CFRP patches to the A-pillar with a general press forming tool. In this paper, a flexible system that applies uniform pressure to complex shapes using ceramic particles and silicone rubber is proposed. By benchmarking various A-pillars, a reference model with an undercut shape was designed, and the system was configured to realize a uniform pressure distribution in the model. The ceramic spherical particles failed to realize the uniform distribution of high pressure due to their high hardness and point contact characteristics, which caused damage to the CFRP patch. Compression equipment made of silicone rubber was able to achieve the required pressure level for curing the epoxy. Non-adhesion defects between the metal and the CFRP patch were confirmed in the area where the bending deformation occurred. This defect could be eliminated by optimizing the process conditions suitable for the newly developed flexible system.

• Journal of the Korean Wood Science and Technology
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• 제51권6호
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• pp.431-446
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• 2023

Samama wood (Anthocephalus macrophyllus (Roxb) Havil) is a fast-growing and lesser-utilized wood species that has inferior properties; therefore, its quality needs to be improved. This research aimed to determine the effect of citric acid impregnation at high curing temperatures on the dimensional stability and mechanical properties of wood. Citric acid solution with 10% concentration (w/w) was impregnated into wood samples by vacuum-pressure method (-0.5 cmHg, 30 min; 0.7 MPa, 3 h), followed by curing process at 140℃, 160℃, and 180℃ of temperature for 1 h. In comparison, the other wood samples were heat treated at the same temperatures and time. The results showed that the increase in curing and heat temperatures for both treatments were directly proportional to the dimensional stability, but inversely proportional to the mechanical properties. Citric acid impregnated had higher density, dimensional stability, and mechanical properties, except for modulus of rupture, than that of heat treatment. The optimum temperature is suggested at 160℃ in both treatments.

• 대한의용생체공학회:의공학회지
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• 제29권4호
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• pp.323-328
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• 2008

A patient with respiratory disorders such as a sleep apnea is increasing as the obese patient increase on the modern society. Positive Airway Pressure (PAP) devices are used in curing patient with respiratory disorders and turn out to be efficacious for patients of 75%. However, these devices are required for evaluating their performance to improve their performance by the mechanical breathing simulator. Recently, the mechanical breathing simulator was studied by the real time feedback control. However, the mechanical breathing simulator by an open loop control was specially required in order to analyze the effect of flow rate and pressure after operating the breathing auxiliary devices. Therefore the aims of this study were to make the mechanical breathing simulator by a piston motion and a valve function from the characteristic test of valve and motor, and to duplicate the flow rate and pressure profiles of some breathing patterns: normal and three disorder patterns. The mechanical simulator is composed cylinder, valve, ball screw and the motor. Also, the characteristic test of the motor and the valve were accomplished in order to define the relationship between the characteristics of simulator and the breathing profiles. Then, the flow rate and pressure profile of human breathing patterns were duplicated by the control of motor and valve. The result showed that the simulator reasonably duplicated the characteristics of human patterns: normal, obstructive sleep apnea (OSA), mild hypopnea with snore and mouth expiration patterns. However, we need to improve this simulator in detail and to validate this method for other patterns.

• 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).

• Corrosion Science and Technology
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• 제7권1호
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• pp.13-15
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• 2008

Aiming at the corrosion circumstances and corrosion prevention needs of downhole oil tubes, series protective coatings for downhole oil tubes have been developed in the authors' laboratory, including a baked type coating YG-01 and an air curing type coating YG-03, etc. The performance investigation of the coatings has been done for testing their corrosion resistance, mainly including salt fog test, immersion test in oil-field waste water and various acid solutions, high temperature and high pressure test in alkali solution or $H_2S/CO_2$ environment, as well as some other performances. The investigation results show that oil tube anti-corrosion coatings developed here can endure over 4000 hrs salt fog test, over 1000 hrs immersion in various acid solutions at room temperature and in boiling oil-field waste water. In addition, the coatings can keep intact after experiencing test in alkali solution under 70 MPa pressure at $150^{\circ}C$ for 24 hrs, and in simulative sour gas environment under the total pressure of 32 MPa ($P_{H_{2}S}=3.2MPa$, $P_{CO_{2}}=3.2MPa$) at $90^{\circ}C$ for 168 hrs, which show that the coatings can be used for corrosion prevention in downhole environments with specific high temperature and high pressure, such as sour gas wells. The other testing results show the oil tube protective coatings have excellent comprehensive performance.

• Elastomers and Composites
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• 제49권3호
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• pp.199-203
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• 2014

아크릴 단량체인 2-ethylhexyl acrylate (2-EHA), 2-hydroxyethyl acrylate (2-HEA), isobornyl acrylate (IBOA)를 광중합을 통하여 3원 공중합체 시럽을 합성하였다. 이관능기 아크릴 단량체인 1,6-hexanediol diacrylate (HDDA), poly(ethylene glycol) diacrylate (PEGDA, Mn = 250, 575, 700)를 가교제로 사용하여 semi-IPN형 감압성 점착제 (Pressure sensitive adhesives; PSAs)를 UV-광가교 시켜 제조하였다. 가교제 변화에 따른 감압성 점착제의 점착특성, 저장탄성율, 그리고 광학특성을 고찰하였으며, 점착특성과 저장탄성율은 가교제의 화학구조와 분자량에 의존하였다. 광학특성은 모든 감압성 점착제에서 92.5 % 이상의 광투과도 (at 550 nm), 1.0 % 이하의 haze값, 0.3 이하의 색차계값을 보임을 확인하였다. 결과적으로 가교제의 종류에 영향을 받지 않음을 확인하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.13-16
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• 2008

This paper is to present the performance data for improved direct setting method using tile bond for application of porcelain tile under 1 percent absorptance. For this purpose, improved direct setting method type 1 & 2(tile bond curing time 0, 24H) were compared with the conventional setting methods(including direct setting method and improved pressure setting method) in the sight of the adhesive stability of porcelain tile. It tested for tiles after 14, 28days under standard condition and severe conditions. The severe conditions were water immersion, heat ageing(70℃) and freeze-thaw cycle. On the basis of test results, the adhesive strength of direct setting method was lowest for the conventional setting methods. But improved direct setting method using tile bonds(A, B) came close to the result of improved pressure setting method using tile bonds.