• Wind and Structures
• /
• v.28 no.1
• /
• pp.19-30
• /
• 2019

This article present the free vibration analysis of simply supported perfect and imperfect (porous) FG beams using a high order trigonometric deformation theory. It is assumed that the material properties of the porous beam vary across the thickness. Unlike other theories, the number of unknown is only three. This theory has a parabolic shear deformation distribution across the thickness. So it is useless to use the shear correction factors. The Hamilton's principle will be used herein to determine the equations of motion. Since, the beams are simply supported the Navier's procedure will be retained. To show the precision of this model, several comparisons have been made between the present results and those of existing theories in the literature.

• Structural Engineering and Mechanics
• /
• v.70 no.3
• /
• pp.325-337
• /
• 2019

In the present article, cross ply laminated composite plates are considered and a simple sinusoidal shear deformation model is tested for analyzing their flexural, stability and dynamic behaviors. The model contains only four unknown variables that are five in the first order shear deformation theory (FSDT) or other higher order models. The in-plane kinematic utilizes undetermined integral terms to quantitatively express the shear deformation influence. In the proposed theory, the conditions of zero shear stress are respected at bottom and top faces of plates without considering the shear correction coefficient. Equations of motion according to the proposed formulation are deduced by employing the virtual work principle in its dynamic version. The analytical solution is determined via double trigonometric series proposed by Navier. The stresses, displacements, natural frequencies and critical buckling forces computed using present method are compared with other published data where a good agreement between results is demonstrated.

• Advances in nano research
• /
• v.10 no.3
• /
• pp.281-293
• /
• 2021

This paper presents a new nonlocal Hyperbolic Shear Deformation Beam Theory (HSDBT) for the free vibration of porous Functionally Graded (FG) nanobeams. A new displacement field containing integrals is proposed which involves only three variables. The present model incorporates the length scale parameter (nonlocal parameter) which can capture the small scale effect and its account for shear deformation by a hyperbolic variation of all displacements through the thickness without using the shear correction factor. It has been observed that during the manufacture of Functionally Graded Materials (FGMs), micro-voids and porosities can occur inside the material. Thus, in this work, the investigation of the free vibration analysis of FG beams taking into account the influence of these imperfections is established. Four different porosity types are considered for FG nanobeam. Material characteristics of the FG beam are supposed to vary continuously within thickness direction according to a power-law scheme which is modified to approximate material characteristics for considering the influence of porosities. Based on the nonlocal differential constitutive relations of Eringen, the equations of motion of the nanobeam are derived using Hamilton's principle. The effects of nonlocal parameter, aspect ratio, and the porosity types on the dynamic responses of the nanobeam are discussed.

• PNF and Movement
• /
• v.20 no.2
• /
• pp.215-222
• /
• 2022

Purpose: The purpose of this study was to compare the effects of passive scapular upward rotation and posterior tilt and active scapular posterior tilt on the muscle activity of the upper trapezius (UT), lower trapezius (LT), and serratus anterior (SA). Methods: Fifteen healthy subjects performed general arm elevation, arm elevation with passive scapular upward rotation and posterior tilt, and arm elevation with active scapular posterior tilt. For active scapular posterior tilt, the subjects were trained in this movement using visual biofeedback and a motion sensor. During each arm elevation condition, electromyography was used to measure the muscle activity of the UT, LT, and SA. The measured data were analyzed using a one-way repeated ANOVA. Results: LT muscle activity was significantly increased during arm elevation with active scapular posterior tilt compared to both general arm elevation and arm elevation with passive scapular upward rotation and posterior tilt (p < 0.05). SA muscle activity was greater during arm elevation with passive scapular upward rotation and posterior tilt than during general arm elevation (p < 0.05). There was no significant change in UT muscle activity among the tested arm elevation conditions (p > 0.05). Conclusion: Performing arm elevation with active scapular posterior tilt and performing arm elevation with passive scapular upward rotation and posterior tilt may be useful strategies for increasing muscle activation of the LT and SA, respectively.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2021.11a
• /
• pp.787-790
• /
• 2021

본 논문에서는 최신 모션 인식 기술을 활용하여 골프 스윙 비디오에서 사람의 자세를 추정한 후 다양한 원인으로 오검출된 좌표들을 보정하여 자세 추정의 정확도를 높이는 방법을 제안한다. 기존의 사람 자세 추정 모델은 골프 스윙 데이터에서 오검출, 반전, 불안정성, 미검출의 문제를 보여 정확한 자세 추정을 어렵게 했다. 이를 해결하기 위하여 본 연구에서는 자세 추정시 발생하는 이상치 데이터들을 Bi-LSTM 으로 학습하고 골프 스윙의 특징을 고려한 간단한 규칙을 통하여 이상치 데이터를 효과적으로 검출하고 이를 보정하는 방법을 제안한다. 또한 다양한 실험과 분석을 통하여 제안하는 방법이 골프 스윙 모션에서 사람의 자세를 정확히 추정할 수 있음을 보인다.

• The Journal of Korean Society for Radiation Therapy
• /
• v.26 no.2
• /
• pp.247-256
• /
• 2014

Purpose : To assess target motion during radiotherapy by quantifying daily setup errors and inter-fractional and intra-fractional movements of pancreatic fiducials. Materials and Methods : Eleven patients were treated via stereotactic body radiotherapy (SBRT) with volumetric modulated arc therapy. Bony setup errors were calculated using cone beam computed tomography (CBCT). Inter-fractional and intrafractional fiducial (seed) motion was determined via cone beam computed tomography (CBCT) projections and orthogonal fluoroscopy. Results : Using an off-line correction protocol, setup errors were 0.0 (-1.7-4.0), 0.3 (-0.5-3.0), and 0.0 (-4.1-6.6) mm for the left-right, anterior-posterior, and superior-inferior directions respectively. Random inter-fractional setup errors in the mean fiducial positions were -0.1, -1.1, and -2.3 mm respectively. Intra-fractional fiducial margins were 9.9, 7.8, and 12.5 mm, respectively. Conclusion : Online inter-fractional and intra-fractional corrections based on daily kV images and CBCT expedites SBRT of pancreatic cancer. Importantly, inter-fractional and intra-fractional motion needs to be measured regularly during treatment of pancreatic cancer to account for variations in patient respiration.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.22 no.6
• /
• pp.323-332
• /
• 2018

Recent two moderate earthquakes (2016 $M_w=5.4$ Gyeongju and 2017 $M_w=5.5$ Pohang) in Korea provided the unique chance of developing a set of relations to estimate instrumental seismic intensity in Korea by augmenting the time-history data from MMI seismic intensity regions above V to the insufficient data previously accumulated from the MMI regions limited up to IV. The MMI intensity regions of V and VI was identified by delineating the epicentral distance from the reference intensity statistics in distance derived by using the integrated MMI data obtained by combining the intensity survey results of KMA (Korea Meteorological Administration) and 'DYFI (Did You Feel It)' MMIs of USGS. The time-histories of the seismic stations from the MMI intensity regions above V were then preprocessed by applying the previously developed site-correction filters to be converted to a site-equivalent condition in a manner consistent with the previous study. The average values of the ground-motion parameters for the three ground motion parameters of PGA, PGV and BSPGA (Bracketed Summation of PGA per second for 30 seconds) were calculated for the MMI=V and VI and used to generate the dataset of the average values of the ground-motion parameters for the individual MMIs from I to VI. Based on this dataset, the linear regression analysis resulted in the following relations with proposed valid ranges of MMI. $MMI=2.36{\times}log_{10}(PGA(gal))+1.44$ ($I{\leq}MMI$$MMI=2.44{\times}log_{10}(PGV(kine))+4.86$ ($I{\leq}MMI$$MMI=2.59{\times}log_{10}(BSPGA(gal{\cdot}sec))-1.02$ ($I{\leq}MMI$

• Geophysics and Geophysical Exploration
• /
• v.14 no.4
• /
• pp.298-304
• /
• 2011

We conducted magnetic survey using IBRV (Ice Breaker Research Vessel) ARAON of KORDI (Korea Ocean Research and Development Institute), ROV (Remotely Operated Vehicle) of Oceaneering Co. and three components vector magnetometer, at Apr., 2011 in the western slope of the caldera of TA25 seamount, the Lau Basin, the southwestern Pacific. The depth ranges of the survey area are from about 900 m to 1200 m, below sea level. For the deep sea magnetic survey, we made the nation's first small deep sea three components magnetometer of Korea. The magnetometer sensor and the data logger was attached with the upper part and lower part of ROV, respectively. ROV followed the planning tracks at 25 ~ 30 m above seafloor using the altimeter and USBL (Ultra Short Base Line) of ROV. The three components magnetometer measured the X (North), Y (East) and Z (Vertical) vector components of the magnetic field of the survey area. A motion sensor provided us the data of pitch, roll, yaw of ROV for the motion correction of the magnetic data. The data of the magnetometer sensor and the motion sensor were recorded on a notebook through the optical cable of ROV and the network of ARON. The precision positions of magnetic data were merged by the post-processing of USBL data of ROV. The obtained three components magnetic data are entirely utilized by finding possible hydrothermal vents of the survey area.

• Journal of the Korean Arthroscopy Society
• /
• v.10 no.2
• /
• pp.153-158
• /
• 2006

Purpose: We evaluated the effectiveness of arthroscopic shaving cystectomy by using posteromedial portal for popliteal cyst with the correction of valvular mechanism. Materials and Methods: We had treated 15 cases of popliteal cyst with arthroscopic shaving cystectomy by using posteromedial portal from April 2004 to June 2005. The mean duration of follow up was 15 months (range: $12{\sim}28$). Functional results were based on the Rauschning and Lindgren criteria. We estimated operative time, time for regaining pain-free full range of motion and checked sonography for recurrence of the cyst at 12 months after the surgery. Results: The functional results by Rauschning and Lindgren criteria were rated Grade 0 or Grade 1 in all cases at last follow up. The average operation time was 45 minutes (range: $35{\sim}70$). All cases regained pain-free full range of motion within five days after surgery and range of motion was also normal at last follow up. There were no recurrence and no walking disturbance in all cases. Conclusion: Arthroscopic shaving cystectomy by using posteromedial portal is one of the effective alternative method of the treatment for popliteal cyst and it is also useful to correct the valvular mechanism.

• The Korean Journal of Nuclear Medicine
• /
• v.33 no.3
• /
• pp.327-336
• /
• 1999

Purpose: To assess the quantitative accuracy and the clinical utility of 3D volumetric PET imaging with FDG in brain studies, 24 patients with various neurological disorders were studied. Materials and Methods: Each patient was injected with 370 MBq of 2-[$^{18}F$]fluoro-2-deoxy-D-glucose. After a 30 min uptake period, the patients were imaged for 30 min in 2 dimensional acquisition (2D) and subsequently for 10 min in 3 dimensional acquisition imaging (3D) using a GE $Advance^{TM}$ PET system, The scatter corrected 3D (3D SC) and non scatter-corrected 3D images were compared with 2D images by applying ROIs on gray and white matter, lesion and contralateral normal areas. Measured and calculated attenuation correction methods for emission images were compared to get the maximum advantage of high sensitivity of 3D acquisition. Results: When normalized to the contrast of 2D images, the contrasts of gray to white matter were $0.75{\pm}0.13$ (3D) and $0.95{\pm}0.12$ (3D SC). The contrasts of normal area to lesion were $0.83{\pm}0.05$ (3D) and $0.96{\pm}0.05$ (3D SC). Three nuclear medicine physicians judged 3D SC images to be superior to the 2D with regards to resolution and noise. Regional counts of calculated attenuation correction was not significantly different to that of measured attenuation correction. Conclusion: 3D PET images with the scatter correction in FDG brain studies provide quantitatively and qualitatively similar images to 2D and can be utilized in a routine clinical setting to reduce scanning time and patient motion artifacts.