• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.132.4-132
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• 2001

Field robot represented by excavator can be applied for various kinds of working in manufacturing, construction, agriculture etc. because of the flexibility of its multi-joint mechanism and the high power of hydraulic actuators. In general, the dynamics of field robot have strong coupling, various kinds of non-linearity, and time varying parameters according to working conditions. Therefore, it is very difficult to describe the system well, and design controller systematically based on its model. This paper established the mathematical model of field robot driven by electro-hydraulic servomechanism and constructed the adaptive control system robust to external load variations. The proposed control system for the field robot was evaluated by the computer simulation, and the performance results of trajectory tracking were compared with that of PID control system.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.2_1
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• pp.149-161
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• 2020

We describe a new approach to implement of trajectory control and track record of articulated manipulator based on monitoring simulator for smart factory. The learning control algorithm was applied in implementation real-time control to provide enhanced motion control performance for robotic manipulators. The proposed control scheme is simple in structure, fast in computation, and suitable for real-time control. Moreover, this scheme does not require any accurate dynamic modeling, or values of manipulator parameters and payload. Performance of the proposed controller is illustrated by simulation and experimental results for robot manipulator consisting of six joints at the joint space and Cartesian space.by monitoring simulator.

• Korean Journal of Applied Biomechanics
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• v.30 no.1
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• pp.73-81
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• 2020

Objective: The purpose of this study is to analyze the effects of aquatic walking exercise on gait and balance parameters of elderly women. Method: 15 elderly people were recruited for this study (age: 73.20±5.19 yrs, height: 153.87±3.36 cm, mass: 60.33±5.73 kg). All variables were measured using Gaitview AFA-50. The variables were the heel contact time ratio, gait angle, and M/P change ratio for gait patterns and ENV, REC, RMS, Total Length, TLC, Sway velocity, and Length/ENV for balance abilities. A paired t-test and the Wilcoxon signed-rank test were carried out to verify the differences in the test scores after participating in the water walking program. The significance level for all statistical analyses was set to α=.05. Results: As for the changes in their walking function after the exercise, heel contact time ratio (p<.01) showed a statistical significance, while gait angle and M/P change ratio did not reveal statistically significant differences. In the test of balance ability on both feet and with eyes opened, statistical significance was found in ENV, REC, RMS, TLC (p<.01), and sway velocity (p<.05), while the test with eyes closed showed statistical significance in length/ENV as well as ENV, REC, RMS, sway velocity (p<.01) TLC, and total length (p<.05). As for the single-leg stance balance ability, ENV and REC revealed statistically significant differences. Conclusion: These results show that water walking is effective for improving the function of the ankle flexor muscles, providing stability to the ankle joint during walking and helping efficient walk. In addition, it is also expected to help prevent falls due to loss of balance by improving the stability of lower extremity muscles and trunk.

• Journal of Korean Neurosurgical Society
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• v.29 no.4
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• pp.528-535
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• 2000

Objective : To investigate objectively the postoperative improvement of gait disturbance in patients with cervical myelopathy through a gait analysis. Patients and Methods : Ten patients who underwent cervical decompression and fusion for cervical myelopathy caused by spondylosis, OPLL, or concomitant hypertrophy of ligamentum flavum were studied. Preoperatively, gait disturbance was present in all patients. The patients were evaluated by gait analysis using three dimensional motion analyzer to collect data of linear and kinematic parameters before surgery, 1 week and 3 months after surgery. Statistical analysis of the related pre-and post-operative data were performed. Results : In the linear parameters, average value of cadence, walking speed, stride length, step time, width and double support were increased postoperatively compare to preoperative value. In the kinematic parameters, average value of knee flexion during initial swing phase, plantar flexion of ankle and range of motion of hip joint were increased as well. These differences were statistically significant(p<0.05). Conclusion : This study suggests that gait analysis can be used as a method of quantitative analysis of postoperative gait improvement in patients with cervical myelopathy.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.505-517
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• 2004

This paper presented equations on the stress evaluation of steel frame pier connections that were composed of a box beam and a circular column. The existing equations, which transformed the circular column into an equivalent box column had some problems; they underestimated a shear lag stress as the joint angle decreased, and overestimated a shear stress as the joint angel increased. Therefore, FE analyses were performed with various parameters, such as joint angle(${\alpha}$), span length-width ratio(L/B), and circular column-to-box beam stiffness ratio(${\alpha}$), and new equations on stress evaluation were proposed based on FE analyses. Furthermore, material and geometric nonlinear analyses were performed to estimate ultimate strength and to confirm the validity of the proposed equations.

• Composites Research
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• v.30 no.2
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• pp.132-137
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• 2017

The purpose of this paper is to investigate failure characteristics of Carbon/BMI-Nomex honeycomb sandwich on design parameters. A total of 6 types sandwich specimens were manufactured according to core height, face thickness and density, and environmental condition were applied to evaluate temperature and humidity effects of one of these specimens. The test results show that the core shear buckling loads was commonly observed in all specimens except for the joint with density of $64kg/m^3$. After core shear buckling, however, the joint carried additional loads over the buckling loads and then finally failed in the upper face and lower face at the same time. In the case of specimen having high stiffness, the maximum failure load was low due to interfacial failure of the upper face and core without initial core shear buckling. The ETW1 and ETW2 conditions, which were carried out to evaluate the environmental condition of the sandwich specimen, show an initial failure mode which was significantly different from RTD condition. Also, the ETW2 condition with increased temperature under the same humidity shows that the core shear buckling load was 18% less than ETW1 condition.

• Physical Therapy Korea
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• v.24 no.2
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• pp.48-57
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• 2017

Background: Rounded shoulder posture (RSP), a postural abnormality, might cause shoulder pain and pathologic conditions. Although most previous research has investigated RSP focusing on the proximal structures of the shoulder, such as the scapula and pectoralis muscles, the relationship between RSP and anterior distal structures of the upper extremity, such as the biceps brachii muscle and elbow joint, is not clearly understood. Objects: This study aimed to investigate the correlations between RSP and the biceps brachii length, elbow joint angle (EJA), pectoralis minor length, general pectoralis major length, humeral head anterior translation (HHAT), glenohumeral internal rotation (IR), external rotation (ER), and horizontal adduction (HAD). Methods: Twelve subjects with RSP (6 male, 6 female) were recruited. All subjects fulfilled the RSP criteria indicated by a distance ${\geq}2.5cm$ from the posterior aspect of the acromion to the table in the supine position. The examiner measured each of the following parameters twice: RSP, biceps brachii length, EJA, pectoralis minor length, pectoralis major length, HHAT, glenohumeral IR, ER, and HAD. Pearson's correlation coefficient(r) was used to assess the correlation between RSP and all the variables. Results: There was a significant moderate positive correlation between RSP and biceps brachii length (r=.55, p=.032), moderate negative correlation between RSP and pectoralis minor length (r=-.62, p=.015), and moderate positive correlation between RSP and HHAT (r=.53, p=.038). Conclusion: The biceps brachii length, pectoralis minor length, and HHAT could be used to evaluate patients with RSP. Better understanding of the correlation between these factors and RSP could help in the development of effective methods to treat patients with this condition in clinical management.

• Imaging Science in Dentistry
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• v.46 no.3
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• pp.217-222
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• 2016

Bifid mandibular condyle (BMC) is an uncommon morphological variant of the mandibular condyle. Although authors have proposed various etiologies for BMC, no consensus has emerged. In addition, varying findings have been reported regarding the epidemiological parameters of BMC (e.g., prevalence, gender ratio, and age), possibly due to its low incidence. BMC is occasionally associated with symptoms of the temporomandibular joint, such as ankylosis, pain, and trismus; however, it is difficult to detect this condition on conventional radiographs. This study reports a case of BMC with radiographic findings, and reviews the literature on the epidemiology of BMC.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.43 no.6
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• pp.363-367
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• 2017

Headaches are one of the most common conditions associated with temporomandibular disorder (TMD). In the present paper, we evaluated the relationship between headache and TMD, determined whether headache influences the symptoms of TMD, and reported two cases of TMD accompanied by headache. Our practical experience and a review of the literature suggested that headache increases the frequency and intensity of pain parameters, thus complicating dysfunctional diseases in both diagnostic and treatment phases. Therefore, early and multidisciplinary treatment of TMD is necessary to avoid the overlap of painful events that could result in pain chronicity.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.155-157
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• 2007

The Friction spot dissimilar welding of galvanized steel/Al6061-T6 was performed to investigate the mechanical characteristics of the joints. The presence of thin film of aluminum oxide on the surface and melting of zinc in the coating, made substandard joint characteristics for dissimilar Friction spot joining(FSJ) performed with out removing the coating. Where as, for dissimilar FSJ of galvanized steel/Al6061-T6 after removing the coating, superior agitation and welding quality has been obtained for a configuration of galvanized steel as the upper plate and Al6061-T6 as lower plate. The results from tensile tests and microscopic examination for various combinations of the welding parameters have been presented.