• The Journal of Advanced Prosthodontics
• /
• 제9권3호
• /
• pp.143-151
• /
• 2017

PURPOSE. The design of the attachment must provide an optimum stress distribution around the implant. In this study, for implant overdentures with a bar/clip attachment or a locator attachment, the stress transmitted to the implant in accordance with the change in the denture base length and the vertical pressure was measured and analyzed. MATERIALS AND METHODS. Test model was created with epoxy resin. The strain gauges made a tight contact with implant surfaces. A universal testing machine was used to exert a vertical pressure on the mandibular implant overdenture and the strain rate of the implants was measured. RESULTS. Means and standard deviations of the maximum micro-deformation rates were determined. 1) Locator attachment: The implants on the working side generally showed higher strain than those on the non-working side. Tensile force was observed on the mesial surface of the implant on the working side, and the compressive force was applied to the buccal surface and on the surfaces of the implant on the non-working side. 2) Bar/clip attachment: The implants on the both non-working and working sides showed high strain; all surfaces except the mesial surface of the implant on the non-working side showed a compressive force. CONCLUSION. To minimize the strain on implants in mandibular implant overdentures, the attachment of the implant should be carefully selected and the denture base should be extended as much as possible.

• 대한치과보철학회지
• /
• 제40권1호
• /
• pp.42-52
• /
• 2002

The purpose of this study was to evaluate the bond strength of reline resin to pressure injection type thermoplastic denture base resin. The denture base resins used in this study were $Hi-polycarbonate^{(R)}$(High Dental Co., Japan), Acetal $dental^{(R)}$(Pressingdental s.r.1., Repubblica di San Marine) of thermoplastic resin and Acron $MC^{(R)}$(GC Dental Industrial Co., Japan) of heat cured resin. The reline resins used were Lucitone $199^{(R)}$(Dentsply international Inc., USA), Tokuso $rebase^{(R)}$(Tokuyama Corp., Japan), and $Lightdon-U^{(R)}$(Dreve-Dentamid-Gmbh, Germany). The reline resins are representative of heat-cured, self-cured, and light-cured resin respectively Bond strength was examined by use of a three-point transverse flexural strength test. The results were as follows 1. The bond strength of Lucitone 199 to Acron MC was the highest. 2. The bond strengths of Lucitone 199 and Tokuso rebase to Hi-polycarbonate resulted in a value of approximately one half that of Lucitone 199 to Acron MC and there were no significant differences between these and the bond strength of Tokuso rebase to Acron MC(p<0.05) 3. The bond strengths of reline resins to Acetal dental were lower than those of reline resins to Hi-polycarbonate. 4. For all base resins Lightdon-U showed lower bond strength than the other reline resins.

• 대한인간공학회지
• /
• 제32권1호
• /
• pp.145-152
• /
• 2013

Objective: The aim of this study is to develop an ergonomic office chair that has an alarm function for the unbalanced sitting postures. Background: Contrary to expectation, it is reported that office workers sit on their chairs much more in unbalanced postures during daily work. Even though an office worker uses an ergonomically good-designed chair and begins their work in a good sitting posture, his/her posture is likely to shift to the unbalanced bad posture. Therefore, a posture alarm system would be very helpful in keeping office workers' good postures. Method: We developed a prototype chair with four load cells under a seat pan and one load cell beneath a backrest. Through some experiments, we set the criteria for unbalanced bad postures then implemented the criteria into the alarm system of the prototype chair. The chair called e-BASE chair could detect unbalance postures and show alarms for chair users. We also enhanced back support by developing a step-wised folding backrest. Results: The e-BASE chair showed better performance in interface pressure distributions and balanced posture ratio in VDT work. Conclusion: The ergonomic chair with posture alarm function(e-BASE chair) was developed. It showed better performance in seat pressure distribution and in keeping good posture during office work. Application: The posture alarm system and folding backrest can be applied to the new models of office chair.

• 한국재료학회지
• /
• 제27권5호
• /
• pp.276-280
• /
• 2017

This study was carried out to evaluate the developed microstructures and mechanical properties of friction welded A6063 alloy. For this work, specimens were prepared at a size of 12 mm ${\O}{\times}80mm$, and friction welding was carried out at a rotation speed of 2,000 RPM, friction pressure of $12kgf/cm^2$ and upset pressure of $25kgf/cm^2$. To perform an analysis of the grain boundary characteristic distributions, such as the grain size, orientation and misorientation angle distributions, the electron back-scattering diffraction method was used. In addition, in order to identify the dispersed intermetallic compounds of the base and welded materials, transmission electron microscopy was used. The experimental results found that the application of friction welding on A6063 led to significant grain refinement of the welded zone relative to that of the base material. Besides this, intermetallic compounds such as AlMnSi and $Al_2Cu$ were found to be dispersed with more refined size relative to that of the base material. This formation retains the mechanical properties of the welds, which results in the fracture aspect at the base material zone. Therefore, based on the developed microstructures and mechanical properties, the application of friction welding on A6063 could be used to obtain a sound weld zone.

• 한국의류학회지
• /
• 제41권4호
• /
• pp.687-697
• /
• 2017

To figure out an appropriate pressure level for a body warming base layer, human responses were observed when the pattern reduction of base layers varied. Under the condition of $2^{\circ}C$, 60% RH, 0.1m/s, ten male subjects participated in the experiment with four sizes of experimental vests where heating pads were attached. The subjective evaluations of the heating vests with different sizes were reported using 7 or 9 point scales. We simultaneously observed chest, abdomen and scapula skin temperatures and microclimate humidity. It was found that the tight pattern as in the case of A or B provided a warmer subjective sensation and skin temperature than C or D; however, there were no differences in skin temperature at the chest. Eventually, the chest temperature decreased after about 30 mins of heating; however, temperature of abdomen increased and indicated that heating with two commercial pads used was inadequate for whole body warming. The pressure sensation of 'tight' was improved after warming the abdomen in a cold environment. Overall, the gaps beyond the original circumference of the abdomen, as in C or D, were not desirable for the local heating of abdomen under the conditions of this experiment where walking was included in the protocol. The experiment garment B with nude waist circumference was the best, and D with the largest ease, was the worst for a comfortable warming vest.

• 대한치과보철학회지
• /
• 제34권4호
• /
• pp.665-674
• /
• 1996

This study was designed to evaluate the effect of processing method and surface design on the transverse strength of repaired denture base resin. Three heat-cured denture base resins(Vertex, Lucitone, Lang), one cold-cured resin(Lang), and one light-cured resin(Dentacolor gingiva material) were used for repair purpose. The specimens for 3-point flexure test were fabricated by five processing methods such as self-curing, pressure pot, boiling water, processing, and light curing. Finally to evaluate the effect of surface designs for repaired resin, three surface designs(butt, bevel, inverse bevel) were tested. Within the limit of this study, following conclusions were drawn. 1. Lucitone denture base material showed highest flexural strength of $131.37{\pm}2.15MPa$, and there were significant differences in stength between Lucitone and other resins. 2. Between two different self curing methods, self curing repair resin, Lang, cured by pressure pot method showed highest flexural strength, $58.49{\pm}4.89MPa$. 3. Among the heat cured repair resins, maximum transverse strength value of $88.69{\pm}16.60MPa$ was recorded in Lucitone group cured by processing method. 4. Inverse bevel joint design showed significantly higher bond strength than butt joint group, Maximum bond strength was $59.36{\pm}1.33MPa$ in inverse bevel joint design group.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 추계학술대회 논문집
• /
• pp.111-114
• /
• 2005

Experimental and numerical studies were carried out in order to investigate the processability and the transcriptability of the injection molding of micro structures. For this purpose, we designed a mold insert having micro rib patterns on a relatively thick base part. Mold insert has a base of 2mm thickness, and has nine micro ribs on that base plate. Width and height of the rib are $300{\mu}m\;and\;1200{\mu}m$, respectively. We found a phenomenon similar to 'race tracking', due to 'hesitation' in the micro ribs. As the melt flows, it starts to cool down and melt front located in the ribs near the gate cannot penetrate further because the flow resistance is large in that almost frozen portion. When the base is totally filled, the melt front away from the gate is not frozen yet. Therefore, it flows back to the gate direction through the ribs. Consequently, transcriptability of the rib far from the gate is better. We also verified this phenomenon via numerical simulation. We further investigated the effects of processing conditions, such as flow rate, packing time, packing pressure, wall temperature and melt temperature, on the transcriptability. The most dominant factor that affects the flow pattern and the transcriptability of the micro rib is flow rate. High flow rate and high melt temperature enhance the transcriptability of micro rib structure. High packing time and high packing pressure result in insignificant dimensional variations of the rib. Numerical simulation also confirms that low flow rate causes a short shot of micro ribs and high wall temperature helps the filling of the micro ribs.

• 한국강구조학회 논문집
• /
• 제17권2호통권75호
• /
• pp.217-225
• /
• 2005

본 연구에서는 축력과 모멘트를 받는 H형강 주각부의 거동에 대해 조사하였다. 주각부의 거동을 분석하기 위하여 유한요소해석법을 이용하였으며 주각부의 해석적 모델을 도출하고자 하였다. 6개의 시험체에 대하여 축력비와 앵커볼트 크기, 베이스플레이트의 두께를 변수로 두고 각각의 거동을 알아보고자 하였으며 H형강 주각부의 실험결과와 유한요소해석결과 그리고 해석적 모델을 상호 비교하였다. 또한 일반적으로 축력과 모멘트를 받는 베이스플레이트의 설계에서 가정하는 지압응력과 유한요소해석에 의한 베이스플레이트의 지압응력의 분포를 비교하였다. 연구결과를 비교한 결과 주각부의 거동을 나타내는 초기강성과 항복하중은 유사하게 나왔으며, 지압응력은 베이스플레이트의 두께가 얇을수록 기둥의 하단에 집중되는 현상을 보였다.

• 대한치과기공학회지
• /
• 제33권1호
• /
• pp.25-35
• /
• 2011

Purpose: There are some advantages of the acrylic resin denture base ; appropriate strength, volume safety, simple processing apparatus, and low cost. But, it have a weakness for fracture by intense pressure or shock. However, the repairs for resin denture base are possible using various materials and techniques. There is a few studies in repairs for resin denture base, but not clinical researches. And there is no studies in absorbed saliva into the region of fracture and bond strength. This study is to observe re-bond strength of resin denture base after repairing under saliva absorption. Methods: The samples were made of heat curing resin and the rectangular parallelepiped specimens which were 50mm long, 10mm wide and 3mm high. The four different groups immersed in the artificial saliva for 2 weeks were prepared, 1) no repaired control samples, 2) immediately repaired samples, 3) repaired samples after 1 day dry, and 4) repaired samples after 3 days dry. The prepared samples were repaired by two different curing materials, self curing resin and heat curing resin method. Each groups composed of 10 specimens were experimented with the three point bending tests for bonding strength measuring Results: There were under condition absorbed in the artificial saliva and repaired by self curing resin method, repaired specimens after 1 day and 3 days dry groups had higher values of bonding strengths than control group, and bonding strengths of immediately repaired samples were similar to those of control samples (p<0.05). There were under condition immersed in the artificial saliva and repaired by heat curing resin method, immediately repaired samples showed similar values to bonding strengths of control groups, and repaired samples after 1 day and 3 days dry groups were lower than those of control group (p>0.05). Conclusion: In this study, the repairs for resin denture base were remarkably high values of bonding strengths than those of the past, and showed that have stable bonding strengths independent of saliva absorption of denture base, so present repairs for resin denture base can be performed, regardless of saliva conditions.

• 한국농공학회:학술대회논문집
• /
• 한국농공학회 2002년도 학술발표회 발표논문집
• /
• pp.337-340
• /
• 2002

The purpose of this study is to evaluate the loss volume of base soil materials with the grain size range of filter materials for agricultural reservoir. The test results show that the loss volume is increased with the hydraulic pressure, and the amount of loss volume for same sample is different with the filter range.