• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.91-96
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• 2010

The combination of a bolt and nut is the element most widely used for connecting machines and structures. When a load is repetitively applied in the direction right angle to the bolt axis after the bolt and nut is fastened, the nut gradually becomes loose. To solve this problem, in this study, a new type of the loose-proof nut, called a lock nut, is developed. The lock nut is equipped with a spring, and the spring increases the axial force of the bolt. Then, the connection force between the bolt and nut is also augmented. Three dimensional finite element models for the bolt and spring are generated, and the change of the axial force of the bolt while the bolt is being inserted into the spring is analyzed using MSC/Marc, a commercial finite element program. Finally, the optimum shape of the spring is found according to the response surface analysis methodology. The optimization result is verified by comparing the variation of the axial force of the bolt when the bolt is inserted to the initial and optimized spring.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.35 no.3
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• pp.176-181
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• 2009

Synovial chondromatosis is a rare, benign, monoarticular arthropathy that is characterized by the development of highly cellular, metaplastic cartilaginous nodules in the synovial membrane. It commonly affects larger joints such as the knee, elbow, wrist, shoulder, and hip. Synovial chondromatosis of the temporomandibular joint(TMJ) is rare. Moreover, the temporal involvement of synovial chondromatosis without connection with joint is greatly rare. A 44-year-old women had experienced pain of the right TMJ area and limitation of mouth opening. MRI and CT revealed multiple calcified loose bodies and widening in right upper joint space of TMJ and osteolytic lesion in right temporal bone. Treatment consisted of removal of multiple loose bodies, resection of the osteolytic lesion through the preauricular approach. She was diagnosed with primary transitional synovial chondromatosis of TMJ with involvement of temporal bone. In spite of remaining of the loose bodies, pain and mouth opening improved and there have been no recurrence of signs and symptoms for 5 years follow up.

• Journal of Ocean Engineering and Technology
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• v.26 no.1
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• pp.27-33
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• 2012

This paper presents the effect of temperature on the impedance-based damage monitoring of steel-bolt connections using wireless impedance sensor nodes. In order to achieve the objective, the following approaches are implemented. First, a temperature-compensated damage monitoring scheme that includes a temperature compensation model and damage detection method is described. The temperature compensation model is designed by analyzing the linear regressions between the temperatures and impedance signatures. The correlation coefficient of the impedance signatures is selected as the damage index to monitor the damage occurrence in the target structures. Second, a wireless impedance sensor node is described for the design of the hardware components and embedded software. Finally, the performance of the temperature-compensated impedance-based damage monitoring scheme is evaluated for detecting a loose bolt in the steel-bolt connections on a lab-scale steel girder under various temperatures.

• Smart Structures and Systems
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• v.24 no.3
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• pp.293-301
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• 2019

Bolted joints are commonly used in civil infrastructure and mechanical assembly structures. Monitoring and identifying the connection status of bolts is the frontier problem of structural research. The existing research is mainly on the looseness of a single bolt. This article presents a study of assessing the loosening/tightening health state and identifying the loose bolt by using ultrasonic guided wave in a bolt group joint. A bolt-tightening index was proposed for evaluating the looseness of a bolt connection based on correlation coefficient. The tightening/loosening state of the bolt was simulated by changing the bolt torque. More than 180 different measurement tests for total of six bolts were conducted. The results showed that with the bolt torque increases, value of the proposed bolt-tightening index increases. The proposed bolt-tightening index trend was very well reproduced by an analytical expression using a function of the torque applied with an overall percentage error lower than 5%. The developed damage index based on the proposed bolt-tightening index can also be applied to locate the loosest bolt in a bolt group joint. To verify the effectiveness of the proposed method, a bolt group joint experiment with different positions of bolt looseness was performed. Experimental results show that the proposed approach is effective to detect and locate bolt looseness and has a good prospect of finding applications in real-time structural monitoring.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.1
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• pp.1-10
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• 1999

The north-west sea area of Cheju Island is where originate two layer current in the summer season. The case of the fishing operations in this sea area is almost impossible for normal expansion of the net gear for shooting net, and is happened to be frequent occasions for rise of tension suddenly in purseline by changes of the net shapes in the operation. Therefore, the safety of the operations is often obstructed by the above mentioned. In connection with the above, model experiments on the purse seine in the circulating water tank was carried out in comparison and analysis on the changes of tension in the pruseline by deformation of purse seine in the sea area of two layer current. THe results obtained are as follows;In the case of the required time for pursing of 20 minutes in the no current set, the increasing curve for tension of purseline can be expressed as:Y=0.0004x3+0.0098x2+0.3000x(r=0.9989)where Y is tension(metric tons) of a purseline, x is required time(minutes) for pursing. And, the maximum value of tension in this time was an increase of 31.3 percent at 15 minutes, and was a decrease of 30.3 percent at 30 minutes than that of 20 minutes.When the bottom margin of net is held on the position in velocity of 0.5 knot at three-eighths of net in the bottom current to the net height, the maximum tension of the required time for pursing of 30 minutes in tight set and loose set were decrease of 29.5 percent and 28.7 percent respectively than that of 20 minutes.The work load during the required time for pursing of 20 minutes were calculated 5.79×106 kgf·m in no current set, 7.89×106 kgf·m in tight set and 5.15×106 kgf·m in loose set, therefore it was an increase of 22.3 percent in tight set, and was a decrease of 11.1 percent in loose set than that of the no current set. Where tight set and loose set is a range of the bottom current with velocity of 0.5 knot at three-eighths of net to the net height.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.3
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• pp.494-500
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• 2008

This paper presents the analyzed result of the series arc fault current by using the discrete wavelet transform. The series arcing is caused by a loose connection in series with the load circuit. The series arc current is limited to a moderate value by the resistance of the device connected to the circuit, such as an appliance or a lighting system. The amount of energy in the sparks from the series arcing is less than in the case of parallel arcing but only a few amps are enough to be a fire hazard. Therefore, it is hard to detect the distinctive difference between a normal current and a intermittent arc current. This paper, presents the variation of the ratio of peak values and RMS values of the series arc fault current, and proposes the novel series arc fault detecting method by using the discrete wavelet transform. Loads such as a CFL lamp, a vacuum cleaner, a personal computer, and a television, which has the very similar normal current with the arc current, were selected to confirm the novel method.

• 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.

• Journal of the Economic Geographical Society of Korea
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• v.23 no.3
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• pp.262-275
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• 2020

Due to the pandemic caused by Corona 19, cities around the world have faced a change. As the global economic system weakens, localization is increasing in the product production and distribution system. In addition, consumption patterns have changed in urban where localization has been strengthened. As a result, the way physical places are consumed is also changing. Consumption of large multi-use facilities has drastically decreased, the speed of the collapse of the online and offline boundaries has been accelerated, and the consumption of amenities for sharing tastes has become more subdivided, specialized, and private. A big change also appeared in the urban scene, which is perceived as the concentration of urban amenities. Local scale and locality became important in the urban scene, and a new urban scene element called empathy emerged. Empathy aims to connect socially and emotionally to individuals consuming urban amenities. The pursuit of connectivity, taste consumption, and nostalgia. In this study, the space for cultural consumption based on empathy was named as empathetic space and the concept was explained. The importance of empathic space in the urban scene in the future post-corona situation was presented.

• Journal of the korean society of oceanography
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• v.35 no.1
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• pp.1-10
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• 2000

A two-dimensional numerical model was applied to investigate the sediment transport and sand bank formation in a macrotidal sea, the Kyunggi and Asan Bays. The tidal residual currents show quite complex pattern including counter-rotating eddies off the northwestern corner of the Dugjeok Island that reflect the promontory effect. Complex residual eddies are also present off the coast of the Taeanbando and in the Asan Bay. Net sediment transport pattern shows that sandy sediments in the Kyunggi and Asan Bays are generally transported landward from the outer sea suggesting sediment trapping inside the bays. This phenomenon may be related to the formation and maintenance of numerous sand banks in this macrotidal sea. Alternate occurrences of deposition and erosion predicted from the numerical model along the coast of the Taeanbando with strong deposition on the southwestern part of the 'Jangansatoe'(JSB), a large sand ridge off the coast of the Taeanbando appear to reflect the loose connection of JSB, The 'Joongangcheontoe', a central sand bank (CSB) with the main axis in the NW-SE direction in the Asan Bay may undergo a modification with strong deposition along the northeastern flank. These results indicate that the sand banks are actively modified and maintained by the strong tidal currents in this shallow macrotidal sea.

• Korean Journal of Head & Neck Oncology
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• v.13 no.2
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• pp.247-250
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• 1997

Bronchogenic cysts are thought to be uncommon developmental anomalies. They develop from small buds or diverticuli that separate from the foregut in the formation of the tracheo-bronchial tree. They are nearly always located near the tracheal bifurcation; However, these lesions can occur anywhere along the tracheo-bronchial tree. We experienced a case of cervical bronchogenic cyst presenting sorely as an anterior neck mass in a 26-year-old woman. The neck ultrasonography showed as $1.4{\times}1.1cm$ sized hypoechoic lesion with a well-defined margin on the isthmic portion of the thyroid gland. Excision of the mass was carried out. The mass was superfical to the strap muscle and was contained within the subcutaneous tissue in the midline without any connection to the trachea. Grossly, the mass was an oval-shaped cystic lesion which measured 1.5 cm in the greatest diameter. The cyst was filled with thick, yellow, jelly-like material and the inner surface was smooth and glistening. Microscopically, the cyst showed a lining of ciliated columnar epithelium, beneath which was a loose areolar stroma containing plaques of mucous glands and mature cartilage. We thought this cervical bronchogenic cyst appeared to represent an expression of complete aberrent accessory lung bud detachment from the primitive foregut.