• Korean Journal of Materials Research
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• v.27 no.6
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• pp.331-338
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• 2017

This study was carried out to investigate the optimum condition of a friction stir welding process for a joint of AA2219-T87 and AA2195-T8 dissimilar aluminum alloys. These alloys are known to have good cryogenic properties, and as such to be suitable for use in fuel tanks of space vehicles. The welding parameters include the travelling speed, rotation speed and rotation direction of the tool. The experiment was conducted under conditions in which the travelling speed of the tool was 120-300 mm/min and the rotation speed of the tool was 400-800 rpm. To investigate the effect of the rotation direction of the tool, the joining was performed by switching the positions of the two dissimilar alloys. After welding, the microstructure was observed and the micro-hardness were measured; non-destructive evaluation was carried out to perform tensile tests on defect-free specimens. The result was that the microstructure of the weld joint underwent dynamic recrystallization due to sufficient deformation and frictional heat. The travelling speed of the tool had little effect on the properties of the joint, but the properties of the joint varied with the rotation speed of the tool. The conditions for the best joining properties were 600 rpm and 180-240 mm/min when the AA2219-T8 alloy was on the retreating side(RS).

• PNF and Movement
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• v.16 no.3
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• pp.317-332
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• 2018

Purpose: Patients with tibial fractures can have functional problems with balance and gait, as well as lower extremity muscle weakness. This case report aimed to describe the effect of hip joint strengthening exercises using proprioceptive neuromuscular facilitation (PNF) on balance and gait and lower limb function in a patient with tibia fracture. Methods: One patient diagnosed with tibial fracture was treated for seven weeks with the basic procedure, pattern, and technique of PNF for a hip joint strengthening exercise. Results: The results of pre- and post-intervention treatment showed improvements in physical function and structure in the clinical tests, including the manual strength test; the modified Ashworth scale; sensory evaluation; balance, sit-to-stand, and gait performance; and evaluation of lower limb function. Conclusion: Based on the results of this study, it is suggested that the use of theory-based proprioceptive neuromuscular stimulation for hip joint strengthening exercises positively affects patients' functional improvement in tibial fracture patients, and this may be used as a therapeutic exercise method for those with orthopedic problems in the lower extremities. One limitation of this study was that it was performed on only one tibia fracture patient, which makes it difficult to extend the treatment effects to all patients with this condition.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.823-824
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• 2016

In general, distribution board, panel board and motor control center can be installed over a wide area such as residence of group, building, schools, factories, ports, airports, water service and sewerage, substation and heavy industries that are used to supply converts the voltages extra high voltage into optimal voltage. There are electrical accidents due to rise of contact temperature, loose contact of bus bar, deterioration of the contact resistance, overtemperatue of the bus bars. In this paper, we propose bus bar joints monitoring system with loose connection of bus bar, measuring the joint resistance of busbars and monitoring internal and external heat. The proposed system can be reduced the electrical accidents by maintenance of busbar joints and the temperature of the conductive contact surface of busbars.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.101-112
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• 2023

When a submerged floating tunnel is connected to the ground, there is a risk of stress concentration at the shore connection owing to the displacement imbalance caused by low confinement pressures in water and high confinement pressures in the ground. Here, the effects of the boundary condition and stiffness of the joints installed at the shore connection on the behaviors of a submerged floating tunnel and its shore connection were analyzed using a numerical method. The analysis results obtained with fixed and ground boundaries were similar due to the high stiffness of the ground boundary. However, the stability of the shore connection was found to be improved with the ground boundary as a small displacement was allowed at the boundary. The effect of the joint stiffness was evaluated by investigating the dynamic behavior of the submerged floating tunnel, the magnitude of the load acting on the bored tunnel, and the stress distribution at the shore connection. A lower joint stiffness was found to correspond to more effective relief of the stress concentration at the shore connection. However, it was confirmed that joints with low stiffness also increase the submerged floating tunnel displacement and decrease the frequency of the dynamic behavior, causing a risk of increased resonance when wave loads with low frequency are applied. Therefore, it is necessary to derive the optimal joint stiffness that can achieve both stress concentration relief and resonance prevention during the design of shore connections to secure their dynamic stability.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1367-1375
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• 2010

In this study, optimization of the process parameters of the resistance spot welding of a sheet of aluminum-coated boron alloyed steel, 22MnB5, used in hot stamping has been performed by a Taguchi method to increase the strength of the weld joint. The process parameters selected were current, electrode force, and weld time. The heating temperature and heating time of 22MnB5 are considered to be noise factors. It was known that the variation in the thickness of the intermetallic compound layer between the aluminum-coated layer and the substrate, which influences on the formation of nugget, was generated due to the difference of diffusion reaction according to heating conditions. From the results of spot weld experiment, the optimum weld condition was determined to be when the current, electrode force, and weld time were 8kA, 4kN, and 18 cycles, respectively. The result of a test performed to verify the optimized weld condition showed that the tensile strength of the weld joint was over 32kN, which is considerably higher than the required strength, i.e., 23kN.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5867-5874
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• 2012

The aim of this study was to find on muscle architectural and tissue compliance of biceps brachii in stroke patient based on elbow joint angle. The subjects of this study were twelve hemiplegic adults after stroke with passive range of motion in the elbow from $10^{\circ}$ to $90^{\circ}$ and Modified Ashworth Scale score 1 to 3 were recruited. Ultrasonography and Myotonometer was used to measure biceps brachii muscle pennation angle, fascicle length, and tissue compliance at the rest condition and pennation angle, fascicle length, and tissue compliance of the biceps brachii muscle were measured in the affected and unaffected sides of people after stroke at 9 different elbow angles ranging from $10^{\circ}$ to $90^{\circ}$ at the rest condition. The results of this study, comparisons found that the pennation angles of the affected biceps brachii muscle were significantly larger(p<.05) than the unaffected muscle in the most extended positions($<40^{\circ}$), whereas the affected fascicle lengths were significantly shorter(p<.05) than the unaffected muscle in most flexed positions($>20^{\circ}$), and the affected tissue compliance were significantly lower(p<.05) than the unaffected muscle in most extended positions($<50^{\circ}$) Therefore, pennation angles, fascicle lengths, and tissue compliance were found to be joint-angle-dependent in both the affected and unaffected sides at the rest condition. Suggest that, the results data can be used as a muscle architectural changes and clinical treatment research in stroke patients.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.4
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• pp.11-20
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• 1997

The aseismic capacity of a traditional three-bay-straw-roof wooden house for rock site condition is quantitatively estimated. One 1/4 scale model was tested for the Nahanni Earthquake with peak ground accelerations from 0.1g to 0.6g. The natural frequency of the wooden house in elastic range is 1.66 Hz and 2.15 Hz in longitudinal and transversal direction, respectively. Damping ratio of the house in elastic range is 7%. The horizontal acceleration response of the house is significantly reduced compared with the input motion due to the nonlinear inelastic characteristics of the Sagae-machum joint of the frame. The traditional wooden house has high aseismic capacity in the rock site condition where high frequency contents of motion are predominant.

• Physical Therapy Korea
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• v.14 no.3
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• pp.16-22
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• 2007

The purpose of this study was to determine the influence of muscle fatigue in elbow flexors on the sense of force reproduction. Fifteen healthy subjects were recruited for this study. Maximum voluntary force (MVF) of elbow flexor muscles was measured by a digital tensiometer. Force errors were measured to test accuracy of the sense of force reproduction in elbow flexors. The subject was required to flex the elbow joint, to maintain and concentrate on about 20% of the MVF target force under visual feedback for 3 seconds. After a 5 second period rest, the subject was asked to duplicate the target force actively. Muscle fatigue was evoked with isometric contraction of the elbow flexors. Isometric contraction was continued until a 50% drop in MVF. The difference, in kilogram between the target force and the reproduced force was calculated for measuring force error. Force errors were compared between the non-fatigued condition and the fatigued condition by the paired t-test. Force errors were significantly increased in the fatigued condition compare to non-fatigued condition. This result suggests that the sense of force reproduction can be disturbed by localized muscle fatigue.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.5
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• pp.27-34
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• 2018

Concrete placed under hot weather condition suffers from larger slump loss, rapid moisture evaporation due to high air temperature. Proper measures for material, transportation and curing should be taken to prevent the quality deterioration of the concrete under hot weather condition. In Korea, Although the period of hot weather concrete in Korea occupies only 2 months, there are a lot of quality problems including plastic, drying shrinkage and cold joint. Therefore, the objective of this paper is to investigate and compare the temperature history and crack occurrence of the concrete, which was placed in the actual apartment house construction field under hot weather condition, in response to the application of surface covered curing blankets including PE film, single layer clear bubble sheet, white colored bubble sheet and aluminum metalized bubble sheet. Test results indicated that the application of white colored bubble sheet and aluminum metalized bubble sheet showed most favorable results in terms of reduction in temperature rise and crack occurrence as well as easiness in handling. But, due to light reflection by aluminum metalized bubble sheet, it is believed that white colored bubble sheet is preferable.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.14 no.1
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• pp.141-152
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• 1984

The author analysed the bone changes, the positional relationships between condylar head and articular fossa, and the interrelationship between the bone changes and the abnormal position of condylar head, from 1,036 radiographs of 259 patients with temporomandibular joint arthrosis, which were obtained by the oblique-lateral transcranial projection and orthopantomograms. The results were as follows: 1. Among the radiographic bone changes of the temporomandibular joint arthrosis, deformity was 36.90%(217 case), sclerosis 34.18% (20 cases), errosive chang 25.85% (152 cases) and marginal proliferation 3.06% (18 cases) respectively. 2. In the positional changes between condylar head and articular fossa, the downward positioning of condylar head in centric occlusion was most frequent(36.90%), of which frequency was signifiantly higher than forward positioning (11.22%) and backward positioning(4.76%) in same condition. Also, radiographs showed that the enlargement of articular space showed higher frequency than its narrowing. In the opening position of mouth, the restricted movement of condylar head within articular fossa was most frequent(35.03%). The forward positioning and the downward positioning was 15.65% and 9.52% respectively. Also, radiographs revealed that the incomplete movement or no positional change of condylar head was most frequent. 3. In the interrelationship between bone changes and abnormal position of condylar head, deformity was 42.79% in the cases of downward positioning of condylar head in centric occlusion and 37.50% in those of normal positioning of condylar head in same condition. This revealed that deformity was most frequent bone change in above condylar positionings. However, erossive change was 34.62% in the cases of downward positioning of condylar head in centric occlusion and 33.33% in those of forward positioning. In opening position of condylar head, and deformity in the cases of normal positioning, forward positioning and downward positioning of condylar head was 38.38%, 36.96% and 44.64% respectively. 4. Bone changes of condylar head was 47.11%, articular eminence 41.50% and articular fossa 11.39% respectively. This revealed that the frequencies of bone changes. were higher in the projected portion of bony structures of temporomandibular joint than their depressed portions. On the otherhand, in the bone changes of condylar head, deformity was 59.57% which was the most frequent. In the bone changes of articular eminence and articular fossa, however, sclersis was 41.39% and 65.67% respectively, which was the most frequent in those portions.