• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.225-231
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• 2019

Purpose: This study was undertaken to compare fracture and flexural strength of provisional restorative resins fabricated by additive manufacturing, subtractive manufacturing, and conventional direct technique. Materials and methods: Five types of provisional restorative resin made with different methods were investigated: Stereolithography apparatus (SLA) 3D printer (S3Z), two digital light processing (DLP) 3D printer (D3Z, D3P), milling method (MIL), conventional method (CON). For fracture strength test, premolar shaped specimens were prepared by each method and stored in distilled water at $37^{\circ}C$ for 24 hours. Compressive load was measured using a universal testing machine (UTM). For flexural strength test, rectangular bar specimens ($25{\times}2{\times}2mm$) were prepared by each method according to ISO 10477 and flexural strength was measured by UTM. Results: Fracture strengths of the S3Z, D3Z, and D3P groups fabricated by additive manufacturing were not significantly different from those of MIL and CON groups (P>.05/10=.005). On the other hand, the flexural strengths of S3Z, D3P, and MIL groups were significantly higher than that of CON group (P<.05), but the flexural strength of D3Z group was significantly lower than that of CON group (P<.05). Conclusion: Within the limitation of our study, provisional restorative resins made from additive manufacturing showed clinically comparable fracture and flexural strength as those made by subtractive manufacturing and conventional method.

• Journal of Technologic Dentistry
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• v.38 no.4
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• pp.273-280
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• 2016

연구목적: 본 연구의 목적은 통상적으로 사용되는 글라스 세라믹과 고분자를 침투시킨 지르코니아 소재로 제작된 코어와 레진 시멘트의 굴곡강도 및 결합강도를 비교하여 하이브리드 기술이 치과 재료의 물리적인 성질에 미치는 영향을 조사하기 위함이다. 연구방법: 본 두 가지의 통상적으로 사용되는 세라믹소재[Vita PM9(GC) and I-JAM(ZC)] 와 다른 두 가지 하이브리드 세라믹 소재 [CELTRA Duo(ZRC) and Vita Enamic(RIZ)] 를 평가하였다. 각 그룹의 소재를 선택하여 결합강도와 굴곡강도, 그리고 scanning electron microscopy(SEM)을 이용하여 표면분석을 시행하였다. 도출된 결과 데이터는 일원분산분석(One-way ANOVA)을 통해 분석되었으며, 제1종 오류의 수준은 0.05로 하였다. 연구결과: RIZ 그룹에서 가장 높은 결합강도를 보였으며(p<0.05), ZC 그룹이 가장 낮은 결과를 보였다. 상대적으로 굴곡강도는 ZC 그룹이 가장 높은 수치를 나타내었으며, RIZ 그룹이 가장 취약했다. 연구결론: 하이브리드 기술로 제작된 소재(RIZ 그룹)는 우수한 레진 시멘트와의 결합강도를 보였지만, 그에 비해 굴곡강도는 상대적으로 통상적인 지르코니아 소재보다 비교적 취약한 결과를 보였다.

• Korean Journal of Applied Biomechanics
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• v.18 no.3
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• pp.33-42
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• 2008

The purpose of this study was to analyze kinematic variables during Side kick motion in Taekwon Aerobics. The subjects of this study were the 7 skilled and 7 unskilled female college students. A QTM and an Auto Track were used to acquire raw data. The sampling rates camera was 100 Hz. The parameters were calculated and analyzed with Visual3D and SPSS 12.0. The results were as following; 1. In the elapsed time, there was no significance difference statically between a skilled and unskilled group. 2. In the cases of knee angle, there was significant difference statically at Maximum Knee Flexion2(p=0.046, F=4.925). 3. In the cases of knee angular velocity, there was significant difference statically at Maximum Knee Flexion1(p=0.031, F=5.940). 4. In the flexion/extension of hip angle, there was significant difference statically at Maximum Knee Flexion2(p=0.012, F=8.668). 5. In the abduction/adduction of hip angular velocity, there was significant difference statically at Minimum Knee Flexion (p=0.019, F=7.324). 6. In the external rotation/internal rotation of hip angular velocity, there was significant difference statically Minimum Knee Flexion(p=0.005, F=11.87).

• The Journal of the Korea Contents Association
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• v.9 no.9
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• pp.278-286
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• 2009

The aims of this study were to determined whether excitability of the $\alpha$-motor neuron is modulated by stretching and this changes were associated with flexibility of the muscle. In this study, $\alpha$-motor neuron excitability was measured by using the Hmax/Mmax ratio of the gastrocnemius H-reflex, and muscle flexibility was measured with the range of motion of the ankle dorsiflexion. The gastrocnemii of 10 healthy volunteers were stretched for 4 minutes(2 minutes stretching, 1 minute rest, and 2 minutes stretching) in each session by manual force. The Hmax/Mmax ratio of the H-reflex, as well as the range of motion of the ankle dosiflexion was measured through four different conditions: before stretching, as soon as after $1^{st}$ stretching, as soon as after $2^{nd}$ stretching and at 48 hours after $2^{nd}$ stretching. Excitability of the $\alpha$-motor neuron was decreased significantly after $1^{st}$ and $2^{nd}$ stretching(p<0.05). Furthermore, the range of the dorsiflexion was increased significantly after $1^{st}$ and $2^{nd}$ stretching(p<0.05). However, the excitability of the $\alpha$-motor neuron and range of the dorsiflexion at 48 hours after $2^{nd}$ stretching were not different from those of before stretching. These results suggest that reduced $\alpha$-motor neuron excitability of the gastrocnemius and increased flexibility of the ankle dorsiflexion would be followed by activation of the type III mechanoreceptor which around the ankle joint and the Golgi tendon organ in the gastrocnemius.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.6
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• pp.738-743
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• 2007

In this paper, a muscle motion sensing system and an artificial arm control system are studied. The artificial arm is for the people who lost one's forearm. The muscle motion sensing system detect the intention of motion from the upper arm's muscle. In sensing system we use flex sensors which is electrical resistance type sensor. The sensor is attached on the biceps brachii muscle and coracobrachialis muscle of the upper arm. We propose an algorithm to classify the one's intention of motions from the sensor signal. Using this algorithm, we extract the 4 motions which are flexion and extension of the forearm, pronation and supination of the arm. To verify the validity of the proposed algorithms we made experiments with two d.o.f. artificial arm. To reduce the control errors of the artificial arm we also proposed a fuzzy PID control algorithm which based on the errors and error rate.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.21-30
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• 2008

The purpose of this study was to investigate changes in mechanical properties of human tibialis anterior following eccentric exercise. Healthy subjects (n=12) performed 120 maximum eccentric contraction of ankle dorsiflexor. Before and 1- and 24- hour after the eccentric exercise, ankle dorsiflexion moment-angle relationships were obtained. Along with significant decrease in maximum isometric muscle strength, the shift of the optimum ankle joint angle toward the longer muscle length direction was observed, independent of the ranges of motion of the eccentric exercise. The results of this study demonstrated that eccentric exercise-induced micro muscle damage(Morgan & Allen, 1999) does rut seem to be a sole mechanism of eccentric contraction-induced muscle damage, suggesting further investigation for the better understandings of this phenomenon.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.602-607
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• 2009

Most of explorer robot in past has the fixed magnitude and communicate with wire communication method. In case of various range of pipe's width and various angle in pipe inter structure, the exploring work is very difficult. Thus, in this paper, we design as dealing with spring tension with pushing out pipe exterior, and applied RF communication. We can accept good performance both structure change and improvement of ability, monitor and collect the defaults data in pipe inter structure. Newly designed and developed pipe explorer robot is very advantageous to carrying and driving as being small and law weight.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5677-5683
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• 2011

The purpose of this study was to determine the effects of hip flexion angles and Kinesio-taping on lumbar extension strength. Forty healthy participants(male=20, female=20) were volunteered for this study. It was used to measure lumbar extension strength with the back strength dynamometer in five angles($0^{\circ}$, $20^{\circ}$, $40^{\circ}$, $60^{\circ}$ & $80^{\circ}$ hip flexion). It was used to estimate and compare back extension strength with independent t-test, paired t-test, correlation analysis and ANOVA. The results of this study were as follows; First, lumbar extension strength was the most achieved at $40^{\circ}$ hip flexion in male and female(p<0.05). Second, lumbar extension strength was showed a statically increase(p<0.05) in $0^{\circ}$, $20^{\circ}$, $40^{\circ}$, $60^{\circ}$ and $80^{\circ}$(except male) after appling taping. These results proposed to us the conclusion that back muscle strength was influenced by hip flexion angles and Kinesio-taping in the lifting work.

• Restorative Dentistry and Endodontics
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• v.31 no.1
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• pp.58-65
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• 2006

The possibility of applying a hi-axial flexure strength test on composite resin was examined using three point and hi-axial flexure strength tests to measure the strength of the light-cured resin and to compare the relative reliability using the Weibull modulus. The materials used in this study were light-curing restorative materials, $MICRONEW^{TM},\;RENEW^{(R)}$ (Bisco, Schaumburg, USA). The hi-axial flexure strength measurements used the piston-on-3-ball test according to the regulations of the International Organization for Standardization (ISO) 6872 and were divided into 6 groups, where the radius of the specimens were 12mm (radius connecting the 3-balls: 3.75mm), 16 mm(radius connecting the 3-balls: 5mm), and the thickness were 0.5mm, 1mm, 2mn for each radius. The hi-axial flexure strength of the $MICRONEW^{TM}\;and\;RENEW^{(R)}$ were higher than the three point flexure strength and the Weibull modulus value were also higher in all of the bi-axial flexure strength groups, indicating that the hi-axial strength test is relatively less affected by experimental error. In addition, the 2 mm thick specimens had the highest Weibull modulus values in the hi-axial flexure strength test, and the $MICRONEW^{TM}$ group showed no significant statistical difference (p>0.05). Besides the 2mm $MICRONEW^{TM}$ group, each group showed significant statistical differences (p<0.05) according to the thickness of the specimen and the radius connecting the 3-balls. The results indicate that for the 2mm group, the hi-axial flexure strength test is a more reliable testing method than the three point flexure strength test.

• Journal of Korean Orthopaedic Sports Medicine
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• v.11 no.2
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• pp.69-74
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• 2012

Purpose: By confirm the change of popliteal arterial position when extension or flexion of the knee and estimate the change of popliteal arterial position after posterior capsular release, we tried to know the position can minimize injury of popliteal artery during arthroscopic surgery and usefulness of posterior capsular release. Materials and Methods: Total of two middle-aged man and woman, fresh frozen cadavers as systemic, all four cases of the knee were included in this study. After the knee was flexed to 0 degrees, 30 degrees, 60 degrees, 90 degrees angle, we estimated distance from posterior tibial cortex to popliteal artery at articular surface, the distal 1 cm and 2 cm from articular surface. We performed posterior capsular release by arthroscopy, and estimated distance between posterior tibial cortex and popliteal artery in the same way. Results: Mean distance between popliteal artery and posterior tibial cortex was 6.3 mm (4.5~7), 4.6 mm (3.6~6), 4.9 mm (3.9~5.8) when knee flexion to 0 degrees at articular surface, distal 1 cm and 2 cm from articular surface each. When knee flexion to 30 degrees, it was 7.4 mm (5.2~9), 4.9 mm (3.6~7.2), 5.3 mm (3.8~6.6). When knee flexion to 60 degrees, it was 8.7 mm (5.4~11), 5.2 mm (4.9~7.3), 6.2 mm (5.4~9.6). When knee flexion to 90 degrees, it was 9.8 mm (5.8~12.1), 5.5 mm (5.1~7.4), 6.5 mm (5.4~10.7). After posterior capsule release, the distance was 6.5 mm (5.5~7.5), 5.8 mm (3.9~7.2), 5.2 mm (3.8~7.0) when knee flexion to 0 degrees, 7.7 mm (5.5~9,1), 7.1 mm (4.6~7.6), 5.5 mm (4.1~6.9) when knee flexion to 30 degrees, 8.9 mm (5.7~11.2), 8.5 mm (5.5~9.2), 6.4 mm (5.3~10.1) when knee flexion to 60 degrees and 10.2 mm (6.3~13.6), 9.5 mm (6.5~11), 6.6 mm (5.9~9.8) when knee flexion to 90 degrees. Conclusion: As knee joint is flexed, the distance from posterial tibial cortex to popliteal artery are increased beween knee joint articular surface and distal 2 cm from knee joint. So popliteal artery injury will be reduced at knee joint surgery. Posterior capsular release could also reduce popliteal artery injury by increasing distance between posterior tibial cortex and popliteal artery.