• The Journal of Advanced Prosthodontics
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• 제2권2호
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• pp.39-45
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• 2010

PURPOSE. The aim of this study was to determine differences in shear bond strength to human dentin using immediate dentin sealing (IDS) technique compared to delayed dentin sealing (DDS). MATERIALS AND METHODS. Forty extracted human molars were divided into 4 groups with 10 teeth each. The control group was light-cured after application of dentin bonding agent ($Excite^{(R)}$ DSC) and cemented with $Variolink^{(R)}$. II resin cement. IDS/SE (immediate dentin sealing, $Clearfil^{TM}$ SE Bond) and IDS/SB (immediate dentin sealing, $Adapter^{TM}$ Single Bond 2) were light-cured after application of dentin bonding agent ($Clearfil^{TM}$ SE Bond and $Adapter^{TM}$ Sing Bond 2, respectively), whereas DDS specimens were not treated with any dentin bonding agent. Specimens were cemented with $Variolink^{(R)}$. II resin cement. Dentin bonding agent ($Excite^{(R)}$. DSC) was left unpolymerized until the application of porcelain restoration. Shear strength was measured using a universal testing machine at a speed of 5 mm/min and evaluated of fracture using an optical microscope. RESULTS. The mean shear bond strengths of control group and IDS/SE group were not statistically different from another at 14.86 and 11.18 MPa. Bond strength of IDS/SE group had a significantly higher mean than DDS group (3.14 MPa) (P < .05). There were no significance in the mean shear bond strength between IDS/SB (4.11 MPa) and DDS group. Evaluation of failure patterns indicates that most failures in the control group and IDS/SE groups were mixed, whereas failures in the DDS were interfacial. CONCLUSION. When preparing teeth for indirect ceramic restoration, IDS with $Clearfil^{TM}$ SE Bond results in improved shear bond strength compared with DDS.

• Journal of Biosystems Engineering
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• 제41권4호
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• pp.304-312
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• 2016

Purpose: Soil strength has been measured using a cone penetrometer, which is making it difficult to obtain the spatial data required for precision agriculture. Our objectives were to evaluate real-time horizontal soil strength (RHSS) to measure soil strength in real time while moving across the field. Using the RHSS data, the tillage depth was determined, and the power consumption of a tractor and rotavators were compared. Methods: The horizontal soil-strength index (HSSI) obtained by the RHSS was compared with the cone index (CI), which was measured using a cone penetrometer. Comparison analysis in accordance with the measurement depth that increased at 5-cm interval was conducted using kriged maps at six sensing depths. For tillage control and evaluation of the power consumption, the system was installed with a potentiometer for tillage depth, a torque sensor from the rear axle, and a power take-off (PTO) shaft. Results: The HSSI was lower than the CI, but they were the same at 54.81% of the total grids for the 5-cm depth and at 3.85% for the 10-cm depth. In accordance with the recommended tillage map, tillage operations between 0 and 15 cm left 2.3% and 7% residue cover on the soil, and that between 20 and 10 cm covered a wider utilization of 3% and 18.4%, respectively. When the tillage depth was 15 cm, the comparison result of the power requirements between the PTO and rear axle in terms of control performance revealed that the maximum power requirements of the axle and PTO were 44.63 and 23.24 kW, respectively. Conclusions: An HSSI measurement system was evaluated by comparison with the conventional soil strength measurement system (CI) and applied to a tractor to compare the tillage power consumption. Further study is needed on its application to various farm works using a tractor for precision agriculture.

• 대한치과기공학회지
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• 제42권4호
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• pp.326-333
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• 2020

Purpose: The purpose of this study was to evaluate the effects of various zirconia surface treatment methods on shear bond strength with resin cements. Methods: We prepared 120 cylindrical zirconia specimens (⌀10 mm×10 mm) using computer-aided design/computer-aided manufacturing (CAD/CAM). Each specimen was randomly subjected to one of four surface treatment conditions: (1) no treatment (control), (2) airborne-particle abrasion with 50 ㎛ of Al2O3 (A50), (3) airborne-particle abrasion with 125 ㎛ of Al2O3 (A125), and (4) ZrO2 slurry (ZA). Using a polytetrafluoroethylene mold (⌀6 mm×3 mm), we applied three resin cements (Panavia F 2.0, Super-Bond C&B, and Variolink N) to each specimen. The shear bond strength tests were performed in a universal testing machine. The surfaces of representative specimens of each group were evaluated under scanning electron microscope. We used one-way analysis of variance (ANOVA), two-way ANOVA, and post hoc Tukey honest significant difference test to analyze the data. Results: In the surface treatment method, the A50 group showed the highest bond strength, followed by A125, ZA, and control groups; however, no significant difference was observed between A50 and A125, A125 and ZA, and ZA and control (p>0.05). Among the resin cements, Super-Bond C&B showed the highest shear bond strength, followed by Panavia F 2.0 and Variolink N (p<0.05). Conclusion: Within the limitations of this study, application of airborne-particle abrasion and ZrO2 slurry improved the shear bond strength of resin cement on zirconia.

• 대한물리의학회지
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• 제16권4호
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• pp.103-116
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• 2021

PURPOSE: This study examined the effects on the upper extremity function, muscle strength, and hand function of a task-oriented training approach using a percussion instrument for patients with chronic stroke. METHODS: Twenty-four chronic stroke patients accompanied with upper extremity hemiplegia were selected for research and were classified randomly into 12 experimental groups and 12 control groups. The experimental group performed a task-oriented approach, and the control group performed upper extremity occupational therapy. Stroke upper extremity test, Jebsen-Taylor Hand Function test, upper extremity muscle strength test, and hand muscle strength test were measured before and after training in the evaluation process. RESULTS: In the upper extremity test and Jebsen-Taylor test, there were no significant differences between the groups. In the upper extremity muscle strength test, there were significant differences in shoulder flexion, internal rotation, and elbow flexion in the experimental group. In the hand muscle strength test, there were significant differences in the grip, tip Pinch, lateral Pinch, and 3-jaw chuck in the experimental group and significant differences in only grip, tip pinch, and lateral pinch in the control group. In addition, there were significant differences in the lateral pinch compared to the amount of change. CONCLUSION: Task-oriented approach using percussion instruments for upper extremity rehabilitation in stroke patients is effective in the upper extremity function and strength, hand function, and strength.

• 대한통합의학회지
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• 제10권4호
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• pp.57-69
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• 2022

Purpose : The purpose of this study was to investigate the effect of ankle strengthening exercise combined with sling-assisted gluteus medius strengthening on ankle instability score, and static and dynamic balance ability, muscle strength in adults in their 20s with chronic ankle instability. Methods : Twenty-eight adults in their 20s with chronic ankle instability were recruited. After screening test, they were randomized through R studio program as an experimental group (n=14) to apply an ankle strengthening exercise combined with sling-assisted gluteus medius strengthening and a control group (n=14) to apply ankle strengthening exercise. The intervention lasted two times a week for 6 weeks. To compare the intervention effects, the Cumberland ankle instability tool (CAIT) score, static and dynamic balance ability, and muscle strength of lower extremities were measured. Results : The experimental group showed a significant increase in pre and post-intervention Cumberland ankle instability tool (CAIT) score, static and dynamic balance ability, and muscle strengt (p<.05). The control group showed a significant increase in pre and post-intervention CAIT score, dynamic balance ability, and muscle strength (p<.05). The experimental group showed a significant increase in CAIT score, dynamic balance ability, and muscle strength compared to the control group (p<.05), and showed a high effect size. Conclusions : The results of this study confirmed that ankle strengthening exercise combined with sling-assisted gluteus medius strengthening on people with chronic ankle instability the possibility that it could be effective in improving ankle instability and improving dynamic balance ability, and strength by movement. Although additional research is needed to increase the number of participants due to the small sample size, it is hoped that this study will be an optimistic clinical protocol for people with chronic ankle instability.

• 한국재료학회지
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• 제30권1호
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• pp.38-43
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• 2020

Sand casting 3D printing uses a binder jetting method to produce a mold having complicated shape by spraying a binder on sand coated with activator. Appropriate heat treatment process in sand mold fabrication can increase the degree of polymerization to improve flexural strength. However, long heat treatment of over 24 hours decreases flexural strength and reliability due to chemical bond decomposition through thermal degradation. The main role of the activator is to control the reaction rate between the polymer chains. As a result, when the activator composition is increased from 0.15 wt% to 0.25 wt%, the flexural strength is increased by 218 N/㎠. However, excess activator (0.40 wt%) has been shown to decrease reliability without increasing flexural strength. The main role of the binder is to control the flexural strength of the specimen. As the binder composition is increased from 2.00 wt% to 4.00 wt%, the flexural strength increases to about 255 N/㎠, indicating the maximum flexural strength increase. Finally, the reliability of the flexural strength of the fabricated specimens is evaluated by a Weibull plot. Weibull modulus calculations are used to evaluate the flexural strength reliability of the specimens, and maximum reliability value of 11.7 is obtained at 0.20 wt% activator composition. Therefore, it is confirmed that this composition has maximum flexural strength reliability.

• 콘크리트학회논문집
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• 제15권1호
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• pp.87-94
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• 2003

현재 건설생산현장에서 이루어지고 있는 거푸집 제거 시기 결정, 설계기준강도 확보 등의 강도관리는 그 시점을 예측할 수 없다는 단점이 있기 때문에 건설생산현장에서의 공정계획 및 강도관리에서 한계가 있을 수밖에 없다. 이에 따라 콘크리트의 강도를 예측할 수 있으면 보다 합리적인 강도관리 및 공정계획이 가능하게 된다. 본 연구는 적산온도 방법에 의해 새로 제안된 강도예측모델의 적용가능성을 검증하기 위해 기존 강도예측모델 중 Logistic 모델과 비교 평가하였으며, 모의부재에서 채취한 코어공시체와 현장양생공시체의 압축강도를 비교 평가한 후 새로운 강도예측모델에 의해 강도를 예측하여 거푸집 제거시기를 결정하는 것에 대한 합리성을 검증하고자 하였다. 실험결과 Freiesleben의 활성화에너지를 이용한 등가재령함수에 있어서 콘크리트의 강도는 양생온도에 관계없이 유사한 강도수준을 나타내고 있으나 강도-적산온도의 상관성을 높이기 위해서는 등가재령 계산시 이용되는 활성화에너지에 대한 검토가 필요할 것으로 사료된다. 새로 제안된 모델의 경우 Logistic 모델에 비해 초기재령에 있어서 강도예측이 보다 정확한 것으로 나타났으며, SSE는 작고 결정계수는 높게 나타나고 있어 이를 이용한 강도예측이 보다 합리적일 것으로 판단된다. 본 연구의 범위 내에서 양생온도 10~15$^{\circ}C$의 경우 강도관리 측면에서 새로운 강도예측모델 사용시 압축강도 50kgf/${cm}^2$ 발현시점이 기존에 제안된 기간과 비교하여 빠르게 나타나고 있어 이를 건설생산현장에서 적용할 경우 거푸집제거시기의 단축에 의한 공기단축이 가능할 것으로 사료된다.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2021년도 제63차 동계학술대회논문집 29권1호
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• pp.127-128
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• 2021

본 연구는 국내 건설산업의 현장프로젝트조직 사업 참여자를 대상으로 프로젝트 참여자간 간 통제유형에 따라 유대 강도와 현장프로젝트 성과에 어떠한 영향을 주는지를 살펴보고자 하는 실증연구이다. 본 연구에서는 통제를 산출통제(Output Control), 과정통제(Process Control), 사회통제(Social Control)로 구분하여 통제유형에 따라 현장프로젝트 참여자 간 유대 강도와 현장프로젝트성과에 어떠한 유의한 영향을 미치며 또한 한국 건설산업의 현장프로젝트조직만이 가지는 특징을 실증분석을 통하여 알아보고자 한다.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2020년도 제61차 동계학술대회논문집 28권1호
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• pp.87-88
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• 2020

본 연구는 국내 ICT산업에서 국제합작투자 기업들을 대상으로 합작사업 참여기업 간 통제유형에 따라 참여기업간 유대강도 및 합작 성과에 어떠한 영향을 주는지를 살펴보고자 하는 실증연구이다. 본 연구에서는 통제유형별(산출통제(Output Control), 과정통제(Process Control), 사회적통제(Social Control))로 국제합작사업 참여기업 간 유대강도에 및 합작성과에 어떠한 유의한 영향을 미치며 또한, 국내 ICT산업에서 국제합작사업에 참여하는 기업들의 특징을 실증분석을 통하여 알아보고자 한다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.159-162
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• 2001

A combined finite element and experimental study based on the characteristic length method is performed to investigate the strength and behavior of the pin joint in composite control rod. The failure is estimated by the Yamada-Sun and Tsai-Wu criteria on the characteristic curve. The gap elements are used to simulate the contact between the pin and the composite fitting with hole. The accuracy and applicability of the method are validated by the joint tests. All the specimens were failed in the bearing mode in the test and finite element analysis, and good agreement was found between the predicted and test results on the joint strength of composite control rod.