• The Journal of Advanced Prosthodontics
• /
• 제10권6호
• /
• pp.415-421
• /
• 2018

PURPOSE. This study investigated the effects of abutment screw lengths on screw loosening and removal torque in external connection implants after oblique cyclic loading. MATERIALS AND METHODS. External connection implants were secured with abutment screws to straight abutments. The abutment-implant assemblies were classified into seven groups based on the abutment screw length, with each group consisting of five assemblies. A cyclic load of 300 N was applied at a $30^{\circ}$ angle to the loading axis until one million cycles were achieved. Removal torque values (RTVs) before and after loading, and RTV differences were evaluated. The measured values were analyzed using repeated measures of analysis of variance with the Student-Newman-Keuls multiple comparisons. RESULTS. All assemblies survived the oblique cyclic loading test without screw loosening. There was a significant decrease in the RTVs throughout the observed abutment screw lengths when the abutment-implant assemblies were loaded repeatedly (P<.001). However, the abutment screw length did not show significant difference on the RTVs before and after the experiment when the abutment screw length ranged from 1.4 to 3.8 mm (P=.647). CONCLUSION. Within the limit of this experiment, our results indicate that the abutment screw length did not significantly affect RTV differences after oblique cyclic loading when a minimum length of 1.4 mm (3.5 threads) was engaged. These findings suggest that short abutment screws may yield stable clinical outcomes comparable to long screws in terms of load resistance.

• 한국항공운항학회지
• /
• 제26권4호
• /
• pp.36-42
• /
• 2018

Although continuous passenger injuries and physical damages are repeated due to the unexpected aviation turbulence encountered during operations, there is still exist the limitation for preventing recurrence of similar events because the lack of real-time information and delay in technological developments regarding various operating conditions and variable weather phenomena. The purpose of this study is to compare and analyze the meteorological data of the aviation turbulence occurred and actual flight data extracted from the Quick Access Recorder(QAR) to provide some precursors that the pilot can identify aviation turbulence early by referring thru the flight instrumentation indications. The case applied for this study was recent event, a scheduled flight from Incheon Airport, Korea to Narita Airport, Japan that suddenly encountered turbulence at an altitude of approximately 14,000 feet during approach. According to the Korea Meteorological Administration(KMA)'s Regional Data Assessment and Prediction System(RDAPS) data, it was observed that the strong amount of vorticity in the rear area of jet stream, which existed near Mount Fuji at that time. The QAR data analysis shows significant changes in the aircraft's parameters such as Pitch and Roll angle, Static Air Temperature(SAT), and wind speed and direction in tens of seconds to minutes before encounter the turbulence. If the accumulate reliability of the data in addition and verification of various parameters with continuous analysis of additional cases, it can be the precursors for the pilot's effective and pre-emptive action and conservative prevention measures against aviation turbulence to reduce subsequent passenger injuries in the aviation operations.

• 한국전문물리치료학회지
• /
• 제26권3호
• /
• pp.42-56
• /
• 2019

Background: Individuals with mechanical neck pain show biomechanical and neurophysiological changes, including cervical spine muscle weakness. As a result of deep muscle weakness, it causes stability disability and reduced upper thoracic spine mobility, which finally leads to functional movement restriction such as limited range of motion and dysfunction. Recent studies have shown that thoracic spine manipulation and mobilization could reduce symptoms of mechanical neck pain in patients. Objects: The purpose of this study was to investigate the effects of thoracic mobility exercise on cervicothoracic function, posture feature, and pain intensity in individuals with mechanical neck pain. Methods: The study subjects were 26 persons who were randomly assigned to the experimental (with thoracic mobility exercise) and control groups (without thoracic mobility exercise), with 13 subjects in each group. The cervicothoracic function (neck functional disability level and cervicothoracic range of motion), posture feature, and pain rating (using a quadrupled visual analogue scale [QVAS]) were measured before, after 3 weeks, and after 6 weeks. Results: Statistically significant group-by-time interactions were found with repeated analyses of variance for the Korean neck disability index (KNDI), all cervical range of motion (CROM), all thoracic range of motion (TROM), cranial rotation angle, sagittal shoulder posture (SSP), and QVAS (p<.05). All groups showed significant improvements from all times in all the evaluated methods. The KNDI, CROM, TROM of left rotation, and SSP in the experimental group showed significant improvements after 3 weeks, and the TROM of the right rotation and QVAS in the experimental group showed significant improvements after 6 weeks when compared with the control group. Conclusion: Thoracic mobility exercise during 6 weeks might be effective intervention to improve the functional level, posture feature, and QVAS pain rating for managing individuals with mechanical neck pain.

• 대한한의학회지
• /
• 제39권4호
• /
• pp.86-113
• /
• 2018

Objectives: We examined the effects of a mixed formula consisting of dried pomegranate concentrate powder (PCP) and the aqueous extracts of Eucommiae cortex (EC) and Achyranthis radix (AR) in rats with surgically induced osteoarthritis (OA). Methods: Two weeks after OA-inducing surgery, a PCP:EC:AR 5:4:1 (g/g) combination or single formula was orally administered. Changes in body weight, knee thickness, maximum knee extension angle, bone mineral density of the knee joints, femoral and tibial articular surfaces, and compressive strength of the femoral and tibial articular cartilage (AC) were assessed, along with the prostaglandin E2 level, 5-lipoxygenase, matrix metalloproteinase (MMP)-2 and MMP-9 activity, and chondrogenic gene mRNA expression in the femoral and tibial AC with the synovial membrane (SM). In addition, the number of cleaved poly(ADP-ribose) polymerase, cyclooxygenase and tumor necrosis factor-${\alpha}$-immunoreactive cells in the femoral and tibial AC with SM were monitored, and the rate of cell proliferation was determined with a 5-bromo-2'-deoxyuridine uptake assay. Results : The signs of surgically induced OA in rats were significantly inhibited by both PCP, EC and AR combined and single formulas. In particular, the combination formula-treated OA model rats showed dose-dependent, significantly increased inhibitory activity against all tested criteria compared with single formula-treated rats. Conclusions: Taken together, our results suggest that the combination formula synergistically increased the anti-OA effects of its components through anti-inflammatory and chondrogenic activity in rats with surgically induced OA. In addition, 200, 100 and 50 mg/kg combination formula treatments showed dose-dependent inhibitory activity against all of the tested criteria.

• 대한통합의학회지
• /
• 제7권2호
• /
• pp.189-195
• /
• 2019

Purpose : The purpose of this study was to investigate the effects of chin tuck exercise (CTE) on the craniovertebral angle (CVA), strength and endurance of deep cervical flexor (DCF) muscles in subjects with forward head posture(FHP). This study was performed on 30 subjects with FHP. Method : Thirty subjects were divided into two groups; modified CTE (n=15), conventional CTE (n=15). Both of the group performed the exercise 4 times a week for 6 weeks. The subjects performed CTE in two different methods; modified CTE, with device designed that help keep cervical lordois curve, and coventional CTE, without using device. The CVA was measured using Image software version. A pressure biofeedback unit was used to measure the strength and endurance of the DCF muscles. The data was analyzed by the paired t-test for comparing before and after changes of variables in each group and the independent t-test for comparing the between groups. Result : There was statistically significant difference of before and after strength and endurance of DCF muscles in modified CTE (p<0.05). There was statistically significant difference of before and after only endurance of DCF muscles in conventional CTE (p<0.05). There was statistically significant difference of between the two group in strength of DCF muscles (p<0.05). Conclusion : Muscle strength to stabilize the spine plays an important role in maintaining a good posture. Therefore, we suggest that the application of CTE with a device designed to maintain the lordotic curvature in the neck is likely to yield better outcomes in FHP subjects in future studies.

• 소성∙가공
• /
• 제28권2호
• /
• pp.63-70
• /
• 2019

This study investigates the effects of multi-axial diagonal forging (MADF) processing number on the microstructures of AA1100 fabricated using MADF processes. The cast AA1100 was annealed at $400^{\circ}C$ for 3hrs in $N_2$ atmosphere and cut into $25mm^3$ cubes for the MADF processes. The MADF process consist of plane forging with a thickness reduction of 30% and a diagonal forging with a diagonal forging angle of 135 degrees. In order to analyze the microstructural variations based on the number of repetitions, 1, 2, 3 and 4 cycles of the MADF process were performed. AA1100 specimens were successfully deformed without cracking of the surface for up to 4 cycles of MADF. The grain size, average misorientation and average grain orientation spread (GOS) of MADF processed materials were analyzed using EBSD technique. The results showed that MADF process effectively refined the microstructure of AA1100 with an initial average grain size of $337.4{\mu}m$. The average grain sizes of specimens which were MADF processed for 2, 3, 4 cycles were refined to be $1.9{\mu}m$, $1.6{\mu}m$, $1.4{\mu}m$, respectively. The grain refinement appeared saturated when AA1100 got MADF processed over 2 cycles. When the specimen was subjected to two or more cycles of MADF, the degree of decrease in the average grain size drastically decreased with an increase in the number of cycle due to the softening phenomena such as dynamic recovery or dynamic recrystallization during processing.

• 한국융합학회논문지
• /
• 제12권8호
• /
• pp.309-315
• /
• 2021

소나무 수피에서 추출한 Pycnogenol은 항균활성과 항산화 효과가 뛰어난 성분으로 항염, 혈압조절기능, 면역조절, 암세포 성장억제 등 다양한 의학적 효능과 함께 천연 소염제로 응용되고 있지만 화장품 관련 연구는 미비한 상황이므로 본 연구는 Pycnogenol 성분이 피부에 미치는 효과를 임상학적 접근한 연구이다. Pycnogenol 성분 첨가, 무첨가한 화장품을 각 각 10명의 임상자가 6주간 사용하게 한 후 피부 상태 변화를 살펴보았으며 모공의 감소, 눈가주름의 감소, 처진모공의 개수와 각도의 감소, 색소침착이 감소하는 효과가 있었다. 그러므로 Pycnogenol 성분을 함유한 화장품은 노화피부에서 나타나는 피부 문제를 개선하는 효과가 있다.

• 대한조선학회논문집
• /
• 제57권5호
• /
• pp.287-296
• /
• 2020

The present study aims to improve the accuracy of the maneuvering simulations based on captive model test results. To derive the hydrodynamic coefficients in a self-propelled condition, a mathematical maneuvering model using a whole vehicle model was established. Captive model tests were carried out using the Vertical Planar Motion Mechanism (VPMM) equipment. A motor controller was used to control the constant propeller revolution rate during pure motion tests. The resistance tests, self-propulsion tests, static drift tests, and VPMM tests were performed in the towing tank of Seoul National University. When the vertical drift angle changes, the gravity load on the sensors were changed. The hydrodynamic forces were deduced by subtracting the gravity load from the measured forces. The hydrodynamic coefficients were calculated using the least-square method. The simulation of the turning circle test was compared with the free-running model test result, and the error of the turning radius was 8.3 % compared to the free-running model test.

• Journal of Industrial and Engineering Chemistry
• /
• 제67권
• /
• pp.244-254
• /
• 2018

Surface modified poly ${\text\tiny{L}}$-lactic acid (PLLA) samples with hydroxyapatite (HA), heparin and bone morphogenetic protein-2 (BMP-2) mediated by polydopamine (pDA) coating (PLLA/pDA/HA/Hep/BMP-2) were prepared, and their effects on the enhancements of bone formation and osseointegration were evaluated in vitro and in vivo as compared to PLLA, PLLA/pDA/HA, and PLLA/pDA/Hep/BMP-2. The changes in surface chemical compositions, morphologies and wettabilities were observed by X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and water contact angle measurements. Pre-coating of HA particles with pDA provided uniform and homogeneous anchoring of particles to PLLA surface. In addition, the strong ionic interaction between heparin and pDA led PLLA surface readily heparinized for loading of BMP-2. In vitro experiments revealed that the levels of alkaline phosphatase (ALP) activity, calcium deposition, and osteocalcin (OCN) gene expression were higher in MG-63 human osteosarcoma cell lines grown on PLLA/pDA/HA/Hep/BMP-2 than on control PLLA, PLLA/pDA/HA, and PLLA/pDA/Hep/BMP-2. In vivo studies using micro-computed tomography (micro-CT) also showed that PLLA/pDA/HA/Hep/BMP-2 screw exhibited greatest value of bone volume (BV) and bone volume/tissue volume (BV/TV) among samples. Histological evaluations with H&E and Von Kossa staining demonstrated that a combination of HA and BMP-2 contributed to the strong osseointegration.

• 한국산학기술학회논문지
• /
• 제22권1호
• /
• pp.402-408
• /
• 2021

기계 설계를 기반으로 제작한 자동차에 의한 사고 발생 시 차량 공학적인 분석은 심도 있게 조사하지 않고 조사자의 주관적인 경험 지식을 토대로 분석하는 경우가 있다. 본 연구는 실제 발생한 중앙선 침범 사고 자료를 토대로 캐드(CAD) 프로그램을 이용하여 현장 상황을 도면화하고, 도면화 한 자료를 시뮬레이션 프로그램(PC-Crash)에 적용하여 250번의 충돌 상황을 반복적으로 수행하여 최종 정지 위치 및 최종 정지 자세와 부합하는 충돌 속도, 진행 자세, 조향 작동 여부 및 제동 여부 등의 상관 관계를 분석했다. 충돌 속도가 낮을수록 이탈각의 영향을 크게 받지 않고 속도가 높은 차량의 속도에 영향을 크게 받고 충돌 이후에는 유효 충돌 속도와 같이 속도가 낮은 차량은 높아지고, 속도가 높은 차량은 낮아진다. 본 연구의 시뮬레이션 결과는 마이티가 중앙선을 넘은 자세로 오르막 좌커브 구간을 진행하다가 마주오던 포터를 인지하고 자기 진행 차로로 복귀하는 과정과 포터의 전면 좌측면이 충돌하여 포터가 우대각선 방향으로 밀려나 전면이 약 11시 방향을 향해 최종 정지하는 것을 규명하였다.