• Journal of the Korean Society of Safety
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• v.16 no.2
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• pp.117-120
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• 2001

Low back pain has been known as the most frequent musuculoskeletal disorders in modern industrial society and cost by low back pain is increasing mon and more. The asymmetric lifting has been identified as a major risk factor of low back pain. In this study, the muscle activity and muscle exertion level during asymmetric load handling (without trunk flexion) was estimated. The results of normalized MVC measurement were decreased about 16％, 24％, 34％ respectively as the asymmetric angle was $30^{\circ}$, $60^{\circ}$, $90^{\circ}$. From the results of EMG measurement contralateral muscles were more active than ipsilateral muscles. RMSEMG values of right erector spinae muscles were decreased as the work posture went to 90$^{\circ}$ and those of left erector spinae muscles were increased until the asymmetric angle was 40$^{\circ}$ but decreased continually over 40$^{\circ}$. And for seven of subjects, activities of left and right latissimus dorsi muscles were maintained constantly, while for remainer, those were irregular.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.11
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• pp.108-114
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• 2021

In this study, a multivariate function was applied to the genetic algorithm for D-type lugs currently used in shipyards to closely analyze the behavioral form of weight loss without double plates. An optimal lifting lug structure design without attachments is proposed. MATLAB R2016a was used to design features by applying multivariate functions to genetic algorithms. Furthermore, the design was achieved by deriving the optimal shapes of lugs using genetic algorithms. The shapes of the designed lugs were validated for structural bonding using the structural analysis program ANSYS 2020 R2, and a robust design of lugs with no appendages was developed.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.27 no.2
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• pp.140-150
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• 2005

Maxillary sinus lifting procedure and bone grafting are used to reconstruct atrophic maxillae. These procedure are usually followed by the placement of endosseous dental implants. Different materials and techniques can be used for sinus bone grafting. Platelets are known to contain various growth factors involved in the repair of the vasculature and tissues, and it is known that the specialized platelet secretory granules, the alpha granules, contain platelet derived growth factor(PDGF), transforming growth factor-beta(TGF-beta), insuline like growth factor-I(IGF-I), epidermoid growth factor(EGF), and others. This study was to evaluate the effect of PRP on bone formation in a sinus bone grafting. Twelve rabbits were included in this randomized, blinded, prospective pilot study. In experimental group, sinus bone grafting with autobone and platelet rich plasma. In control group, sinus bone grafting with only autobone. Rabbits were sacrificed at 2nd, 4th, 8th, 12th weeks postoperatively. Clinical and radiographic tests, histological analysis were conducted to compare both sides. In clinical examination, there in no significant difference between experimental group and control group. But, in radiographic examination, a distinct incresed in the radiopaque of the PRP experimental group at 2nd and 4th weeks. The histologic examination revealed that more new bone formation and osteoblast activity were seen in experimental group at 2nd and 4th weeks. In conclusion, PRPs action in sinus bone grafting had a capacity of increased new bone formation in a early bone healing stage.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.248-255
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• 1998

The objective of this study is to conduct the prevention method using electromyography that is to resist the strain on L5/S1 disc and to measure the heart rate for the prevention of low back pain during lifting. EMG signals and heart rate were analyzed under the condition of fixed vertical factor (20∼80cm), two horizontal factors (35cm, 55cm), and two weight factors (10kg, 25kg) 2 times per minute for each lifting task. Eight healthy male workers performed nine-step stretching exercises which were intensified back power at the L5/S1 disc for six months. After completion of the two trials, the results were compared. The results of this analysis show that EMG signals have more an effect on the weight than the horizontal factors similar to those analyzed previous study, and are decreased. Therefore, those exercises presented very efficient. Also, there are not statistically significant differences on the analysis result of heart rate between weight factors.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.9
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• pp.816-822
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• 2011

In this study, a program has been coded to evaluate propeller thrust rapidly following the effects of propeller shapes and the environmental facts. At this time, Semi-infinite Helical Vortices model is used to predict the induction factor which is introduced by Kawada. This program is based on Wrench's Propeller lifting line theory, and it can predict aerodynamic coefficients such as thrust, power, and efficiency. First of all, this program is compared with test results of NACA reports to verify of the reliability. Secondly, subsonic wind tunnel test has been performed following variations of propeller's rpm and inflow velocities.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.7-12
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• 2004

Large-sized pins are usually used to lift and handle large low speed diesel engine crankshaft. There has then been a need to reduce and optimize the weight of the traditionally used pins. Making an hole by cutting the inside of the pin out was investigated in view of static and fracture strength. To compensate the stress increase caused by the introduction of the inner hole, the groove in the circumferential direction pre-existing on the pin is to be removed. Finite element analysis was carried out for both the original model and weight reduced model. Stress intensity factors for semi-elliptical defects assumed on the pin for the original model and weight reduced model was calculated using the ASME method and compared with the fracture toughness test result of the pin material. The diameter of the cutting hole for the revised model was determined based on the analysis results.

• Journal of agricultural medicine and community health
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• v.44 no.3
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• pp.138-143
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• 2019

Objectives: The purpose of this study was to assess the ergonomic risk factors in beekeeping, and to evaluate the effectiveness of assistive device hive lift. Methods: This study included 30 subjects of beekeeper in Pocheon, Korea. We assessed the ergonomic risk of main task in beekeeping with NLE, OWAS and evaluate the effectiveness of hive lift. We also surveyed prevalence of musculoskeletal symptoms among the subjects based on the Korea Working Condition Survey. Results: Moving to different floral origin, internal inspection of beehives, feeding syrup is the most burdensome to musculoskeletal system (NLE LI value=2~3. OWAS action category=4). The prevalence of musculoskeletal symptoms (lower and upper extremities) among the subjects was over 80 %. The introduction of assistive devices in the three hazardous tasks has dramatically reduced the risk by removing manual lifting hives (OWAS action category<1). Conclusions: Beekeeping is a heavy workload on the musculoskeletal system because it has a lot of manual lifting task. As a result of applying the hive lift, the burden could be reduced.

• Journal of Institute of Convergence Technology
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• v.9 no.1
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• pp.25-30
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• 2019

Normal cranes cannot be used to move the fan inside the high-rise factories. Due to the size of the fan and safety accidents, there is a need for a structure capable of lifting and transporting. In this study, the safety of the structure was evaluated by considering the center of gravity of the fan and the effect of the fan being tilted up. An analysis of the buckling was performed by hand calculation. Nonlinear analysis was performed using ABAQUS to evaluate the safety of the structure. The safety factor for buckling is above 4.0 and the safety factor for stress is calculated to be 1.31 under the worst load distribution conditions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.4
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• pp.48-53
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• 2005

This research is materialized the mechanism of a interlocking elevator device to meet with customer's requirement demanding a variety of function. On this suitably theoretical translation and by considering of material significance of the most factor's tension spring and torsion spring, it's compared and reviewed the stress's calculation according that SWC and SWPB applied differently. And also that is approved through actual experiment. Out of a variety of feasible movement. Torque Balance is materialized by combination of tension spring, torsion spring and disk spring. So that application of 3 factors for optimal design is very important factor. In future, this research thesis make sure to play a highly role for application and improvement mechanically in various industry sector out of materializing interlock.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.1
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• pp.19-26
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• 1996

An experimental and computational study of the pressure fluctuation induced by a propeller on a hull surface was carried out with three ship models and seven model propellers. The fluctuation of pressure on a flat plate was measured at KRISO cavitation tunnel and calculated by a panel and lifting surface method(XForShip code). To extend the measurement data on the flat plate into that on complex hull forms, the correction factor was determined as a ratio of the solid boundary factor(SBF). The computation of pressure fluctuation around complex hull forms was also performed to make the full scale prediction and compared with the corrected experimental data. The calculated values agreed well with the compensated experimental data and it was found that the correction factor was about 0.65-0.7.