• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.2
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• pp.124-132
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• 2018

In this paper, landing stability evaluation of lunar lander considering various landing conditions was performed. The status of landing stability of the lunar lander is classified into stable landing, conditionally stable landing due to sliding and unstable landing due to tip-over. In particular, the quasi-static tip-over equation was rearranged considering the phenomena of lowering the center of gravity and extension of foot-pad interval of the landing gear. These results were compared by finite element model analysis results using a commercial software ABAQUS and its validity and accuracy were verified. The verified finite element model was used for examining the tendency of various environmental variables such as landing conditions, friction coefficient, lateral speed and slope of ground.

• Journal of Korean Neurosurgical Society
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• v.55 no.6
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• pp.331-336
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• 2014

Objective : The purpose of this study was to evaluate the differences in sagittal spinopelvic alignment between lumbar degenerative spondylolisthesis (DSPL) and degenerative spinal stenosis (DSS). Methods : Seventy patients with DSPL and 72 patients with DSS who were treated with lumbar interbody fusion surgery were included in this study. The following spinopelvic parameters were measured on whole spine lateral radiographs in a standing position : pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis angle (LL), L4-S1 segmental lumbar angle (SLL), thoracic kyphosis (TK), and sagittal vertical axis from the C7 plumb line (SVA). Two groups were subdivided by SVA value, respectively. Normal SVA subgroup and positive SVA subgroup were divided as SVA value (<50 mm and ${\geq}50mm$). Spinopelvic parameters/PI ratios were assessed and compared between the groups. Results : The PI of DSPL was significantly greater than that of DSS (p=0.000). The SVA of DSPL was significantly greater than that of DSS (p=0.001). In sub-group analysis between the positive (34.3%) and normal SVA (65.7%), there were significant differences in LL/PI and SLL/PI (p<0.05) in the DSPL group. In sub-group analysis between the positive (12.5%) and normal SVA (87.5%), there were significant differences in PT/PI, SS/PI, LL/PI and SLL/PI ratios (p<0.05) in the DSS group. Conclusion : Patients with lumbar degenerative spondylolisthesis have the propensity for sagittal imbalance and higher pelvic incidence compared with those with degenerative spinal stenosis. Sagittal imbalance in patients with DSPL is significantly correlated with the loss of lumbar lordosis, especially loss of segmental lumbar lordosis.

• Water for future
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• v.27 no.2
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• pp.73-83
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• 1994

The unproper development of the nearshore zone can enhance the diffusion of pollutant in the nearshore zone resulting in unbalanced sediment budget of beach which causes alteration of beach topography. Therefore, it is required to predict the effects of the envirnmental change quantitatively. In this paper, the depth-averaged and time-averaged energy balance equation is selected to acount for the wave transformation such as refraction, shoaling effect, the surf zone energy disipation, wave breaking index and bore, due to wave breaking in the shore region.(Numerical solutions are obtained by a finite difference method, ADI and Upwind. For the calculation of the wave-induced current, the unsteady nonlinear depth-averaged and time-averaged governing equation is derived based on the continuity and momentum equation for imcompressible fluid.) Numerical solutions are obtained by finite difference method considering influences of factors such as lateral mixing coefficient, bed shear stress, wave direction angle, wave steepness, wave period and bottom slope. The model is applied to the computation of wave transformation, wave-induced current and variation of mean water leel on a uniformly sloping beach.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.91-105
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• 1992

For the analysis of multistory frames with sidesway, no adequate procedures can be found in the classical methods of structural analysis. Even well-known procedures such as the slope-deflection method and the moment distribution method may not be effective tools since those methods require a multiple of computational labor and/or yield results of approximate values. In this study, a direct method is developed and proposed for the analysis of multistory frames with sidesway, which is due to the lateral loads, asymmetry of the structure itself, or asymmetry of vertical loadings. The proposed method is to obtain simple forms of equations derived by a mathematical formulation of the moment distribution procedure combined with successive correction concept. Numerical illustrations show that the results obtained by the proposed method agree well with those by rigorous ones. Undoubtedly, this newly developed method can be applied more easily for the analysis of structural frames without joint translation as well as continuous beams.

• Journal of The Korean Society of Integrative Medicine
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• v.7 no.4
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• pp.265-272
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• 2019

Purpose : Excessive computer use frequently results in musculoskeletal disorders of the neck and shoulder such as forward head posture (FHP). The purpose of this study was to investigate effects of neck and shoulder exercise program on spino-pelvic alignment and the correlation between change in head and neck posture and spino-pelvic alignment in FHP. Methods : The study included 44 participants with FHP. The participants performed the exercise for correction of FHP 2-3 times a week for 4 weeks. We examined whole spine X-ray images in the lateral standing position with both arms crossed. We measured anterior head translation distance (AHT), craniovertebral angle (CVA), cervical lordosis (CL), thoracic kyphosis (TK), lumbosacral lordosis (LSL), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI) of the subjects. The association between change in AHT and each spino-pelvic parameter was also subjected to Pearson's correlation coefficient analysis. Results : There were statistically significant differences before and after exercise in the parameters of AHT, CVA, and SS (p<.05). Significant negative correlation was observed between the change in AHT and CVA (r=-.768, p<.001), and CL (r=-.388, p<.05). There was significant positive correlation between the change in AHT and SS (r=.328, p<.05), and PI (r=.333, p<.05). However, no significant correlation was observed in change in AHT with that of TK, LSL, and PT. Conclusion : Based on the above results, we conclude that there is a relationship between change in AHT, which is a parameter associated with forward displacement of the head, and that of CVA, CL, SS, and PI after exercise in cases of FHP.

• Journal of Welding and Joining
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• v.28 no.1
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• pp.66-71
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• 2010

With large specific strength and outstanding corrosion resistance and erosion resistance in sea water, titanium and titanium alloy are widely used in heat exchanger production. In particular, pure titanium demonstrates outstanding molding performance and may be considered optimal for production of heat exchanger. Since titanium is very vulnerable to oxidation and embrittlement during welding, processes with less heat input are widely used, and laser welding is widely applied by considering production performance and shield etc in atmosphere. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through oxygen and nitrogen quantitative analysis and hardness measurement, and evaluated welding performance and mechanical properties of butt welding. This study evaluated field applicability of lap welding to heat exchange plate of LPG re-liquefaction device for ships through tensile stress test, hardness test and internal pressure test etc after deducing optimal weding condition and applying to actual heat exchange plate. In bead overlap area, the experiment produced sound welds with no porosity or defect by increasing and decreasing laser power, and tensile-shear test results indicated virtually the same tension and yield strength as base metal. As a result of measuring hardness at lateral cross section and bead overlap zone of actual heat exchanger welds, hardness difference within 20Hv was produced at base metal, HAZ and weldment, and as a result of pneumatic and hydraulic pressure test, no leakage occurred.

• Journal of The Korean Society of Integrative Medicine
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• v.8 no.3
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• pp.173-180
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• 2020

Purpose : The aim of this study was to assess the intra- and inter-rater reliability and validity of measurements of head, neck, and pelvis posture using a mobile application in subjects with forward head posture. Methods : Forty-eight volunteers (22 men, 26 women) participated in this study. Two raters independently examined whole body picture images in a lateral standing posture with arms crossed using a CA-Smart Posture Reminder (CA-SPR), and a rater took and calculated posture images twice to assess reliability. We measured five parameters: craniovertebral angle 1 (CVA1), anterior shoulder translation (AST), pelvic tilt (PT), knee angle (KA), and ankle angle (AA) in the subject's sagittal plane using CA-SPR. We examined whole spine X-ray images in the same position to assess validity. We measured four variables in the subjects: CVA2, translation distance (AHT), anterior pelvic plane (APP), and sacral slope (SS). The intra- and inter-rater reliability were calculated using the intraclass correlation coefficient (ICC). Convergent validity was calculated using Pearson's correlation coefficient. Results : The intra-rater reliability (ICC=.889 -.989) and inter-rater reliability (ICC=.800 -.980) were excellent for all variables measured using CA-SPR. The variables measured using CA-SPR and X-ray were significantly positively correlated (r=.623, p<.01). However, the correlation of the variables in the pelvis was not statistically significant. Conclusion : This study shows that a mobile application (CA-SPR) is a useful tool for measuring head and neck posture in subjects with forward head posture. However, further study is needed to measure pelvic variables when using a mobile application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1523-1531
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• 2011

Multi-axle driving vehicle are favored for military use in off road operations because of their high mobility on extreme terrains and obstacles. Especially, Military Vehicle needs an ability to driving on hills of 60% angle slope. This paper presents the improvement of the ability of hill climbing for 6WD/6WS vehicle through the optimal tire force distribution method. From the driver's commands, the desired longitudinal force, the desired lateral force, and the desired yaw moment were obtained for the hill climbing of vehicle using optimal tire force distribution method. These three values were distributed to each wheel as the torque based on optimal tire force distribution method using friction circle and cost function. To verify the performance of the proposed algorithm, the simulation is executed using TruckSim software. Two vehicles, the one the proposed algorithm is implemented and the another the tire's forces are equivalently distributed, are compared. At the hill slop, the ability to driving on hills is improved by using the optimum tire force distribution method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.9
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• pp.1615-1622
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• 2008

We have fabricated the poly-silicon thin film transistor(TFT) which has the LDD-region with graded spacer. The devices of n-channel poly-si TFT's hydrogenated by $H_2$ and $H_2$/plasma processes were fabricated for the devices reliability. We have biased the devices under the gate voltage stress conditions of maximum leakage current. The parametric characteristics caused by gate voltage stress conditions in hydrogenated devices are investigated by measuring/analyzing the drain current, leakage current, threshold voltage($V_{th}$), sub-threshold slope(S) and transconductance($G_m$) values. As a analyzed results of characteristics parameters, the degradation characteristics in hydrogenated n-channel polysilicon TFT's are mainly caused by the enhancement of dangling bonds at the poly-Si/$SiO_2$ interface and the poly-Si grain boundary due to dissolution of Si-H bonds. The structure of novel proposed poly-Si TFT's are the simplicities of the fabrication process steps and the decrease of leakage current by reduced lateral electric field near the drain region.

• Journal of Biosystems Engineering
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• v.43 no.4
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• pp.311-319
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• 2018

Purpose: The aim of this study is to develop a small combine for harvesting miscellaneous cereal crops. Methods: A prototype small combine was designed and constructed. Its specifications and basic performance were investigated. Results: The prototype small combine for harvesting miscellaneous cereal crops was designed and constructed to reflect similar specifications as those of the conventional combine. The prototype small combine comprises a diesel engine with the rated power/speed of 22.0 kW/2,600 rpm, three-stage primary and two-stage speed range transmission shifts, and a double acting threshing part. The maximum travel speeds of the prototype combine are approximately 0.72 m/s, 2.50 m/s, 0.30 m/s at the low, high speed range shifts in the forward direction, and while traversing in the reverse direction, respectively. The minimum radius of turning was approximately 1.50 m. In a static lateral overturning test, the prototype combine overturned neither to the right nor to left on a $30^{\circ}$ slope. The results of an oilseed rape harvesting test included the maximum operating speed of 0.32 m/s, the grain loss ratio of approximately 9.0%, and the effective field capacity of approximately 10.3 a/h. Additionally, among the outputs in grain outlet, the whole grains, damage grains, and materials other than grain (MOG) ratios accounted for 97.4%, 0.0%, and 2.6%, respectively. Conclusions: The prototype small combine for harvesting miscellaneous cereal crops indicates good driving ability and stability. The results of the oilseed rape harvesting test reveal that the harvesting performance must be enhanced such that the separating and cleaning parts are more suitable for each type of crop, thus reducing grain loss and foreign substances among the outputs in grain outlet. An improved small prototype combine could be used effectively to mechanize the harvesting of miscellaneous cereal crops in small family farms or semi-mountainous areas.