• Hip & pelvis
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• v.35 no.1
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• pp.54-61
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• 2023

Purpose: The purpose was to examine the clinical and radiological outcomes after surgical treatment of acetabular fractures with total hip arthroplasty with a dual mobility cup cemented into a porous multihole cup in the population of frail elderly patients. Materials and Methods: A retrospective review of 16 patients who underwent surgery (mean age, 76.7 years) with a mean follow-up period of 36.9 months was conducted. Following surgery, patients underwent postoperative follow-up at six weeks, three, six, and 12 months and clinical and radiological examinations were performed. Results: Classification of fractures was based on the Letournel classification. Following surgery, all patients were allowed weight-bearing as tolerated immediately postoperative. Fourteen patients showed maintenance of preoperative mobility status at one year. The mean Harris hip score was 64.8 (range, 34.7-82.8) and 80.0 (range, 60.8-93.8) at three months and one year, respectively. The mortality rate was 12.5% at one year (2/16). Complications included heterotopic ossification (2/16), deep venous thrombosis (1/16), heamatoma (1/16), and femoral revision due to a Vancouver B2 fracture (1/16). No case of deep infection, dislocation, or implant loosening was reported. Conclusion: Total hip arthroplasty using a dual mobility cup cemented into a porous multihole cup with locking screws resulted in a stable construct with a capacity for immediate weight-bearing as tolerated with rapid relief of pain. The findings of this study suggest that this procedure can be regarded as a safe method that has shown promising clinical and radiological outcomes for treatment of patients with medical frailty.

• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.21-34
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• 2017

The ground penetrating radar (GPR) signal can be measured with different amplitudes according to the directivity, so the directivity of the antenna should be considered. The objective of this study is to investigate the directivity of antenna by analyzing the reflection characteristics of electromagnetic waves radiated from the antenna, and to evaluate effective range of angle that can inspect an abnormal area according to the directivity of antenna. For the measurement of the directivity, a circular metal bar is used as reflector and the signals are measured by changing the angle and the distance between reflector and antenna in the E- and H-plane. The boundary distance between the near field and the far field is determined by analyzing the amplitudes of reflected signals, and two points with different distances from each of near and far fields are designated to analyze radiation patterns in near and far fields. As a result of radiation pattern measurement, in the near field, minor lobes are observed at angle section at more than $50^{\circ}$ in both E- and H-plane. Therefore, antenna has the directivity for the direction of main lobe and minor lobes in near field. In the far field, antenna has the directivity for a single direction of main lobe because minor lobes are not observed. The amplitude of the signal reflected from the near field is unstable, but it can be distinguished from noise. Therefore, in the near field, the ground anomaly can be detected with high reliability. On the other hand, the amplitude of the signal reflected from the far field is stable, but it is hard to distinguish between reflected signal and noise because of the excessive loss of electromagnetic wave. The analyses of directivity in the near and the far fields performed in this study may be effectively used to improve the reliability of the analyses of abnormal area.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.860-865
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• 2012

Although biomass syngas is very low calorific gas, it is utilized by means of dual fuel combustion technology in the fields of industrial furnace and boiler as a substitute oil technology. The basic structure of duel fuel combustion burner is designed so that low caloric gas fuel is supplied around an oil burner in the middle. In the present study, three types of mixing burners were manufactured to conduct performance experiment. Low caloric gas was evenly distributed around the oil burner and the method of changing the angle of gas nozzle was applied. CO generation decreased according to the increase of the amount of air for combustion. In addition, the shapes and colors of flame changed according to the proportions of gas and oil used. Remained flame after combustion was from the lack of atomization at the exit of oil burner. Although it was difficult to maintain the optimum air ratio due to different required air ratio for oil and syngas, stable combustion was able to maintained within excess oxygen concentration of 4.7~8.2%. From this study, it was shown that the oil atomization at the exit of fuel oil nozzle was promoted by the increased rate of syngas combustion and the CO concentration in flue gas lower than only fuel oil combustion.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.1
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• pp.19-29
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• 2000

Because the previous simulation tool for attitude control of satellite was designed for the modeling of rigid body and PD controller, the attitude error can be made more than the limitation value for keeping for communication link, and then the communication link can be lost at moving of satellite. So, for rapid attitude restoration and design of stable and modernized controller, the modelling of rigid body and flexible body structure for moving GEO and LEO satellites were performed. Also the minimum time controller is designed for the rapid restoration of attitude error at communication broken and to minimize the disconnection period from ground communication system during the satellite stationkeeping. The linear regulator is designed using the space state vector that is better than accuracy and stability of PD controller. Firstly the simulation was performed for comparison of the rigid and stability of PD controller. Firstly the simulation was performed for comparison of the rigid and flexible models using PD controller and the case of the pitch angle changing by ground command, and the case of the periodic north-south stationkeeping are performed for the analysis of response characteristics of each controller when the attitude is changed. As a result, the flexible body model represents more sililar results of real situation than the rigid body model. The minimum time controller can restore 7 times rapidly than PD controller for its lost attitude. The linear regulator has several merits for capability of adaptation against the external disturbance, stability and response time. In future, we can check the estimated results using this satellite model and controller for real operation. Futhermore the development of new controller and training can be supported.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.394-399
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• 2017

In Korean AC power railway substations, SCOTT winding transformers are under operation to have a single phase power supply together with a phase angle of $90^{\circ}$ on the secondary side of the main transformer. In the case of an internal fault of the transformer, the transformer protection relay should be cut off on the primary side, the transformer should be inoperative to the external fault of the transformer or to the normal train operation. Reducing the malfunction of the relay through an exact fault determination is very important for securing a stable power system and improving its reliability. The main transformers are protected using Buchholtz's relay and a differential relay as the internal fault detection devices, but there are some cases of the main transformer operation under the deactivation of this protection function due to a malfunction of the differential relay. In this paper, the characteristics of the SCOTT transformer and differential relay as well as the malfunctioning of the protection relays are presented. The modeling of the SCOTT transformer protection relay was accomplished by the power system analysis program and the Comtrade file from 'A substation', which was used as the input data for the fault wave, and the harmonics were analyzed to determine if the relay operates or not. In addition, an improvement plan for malfunctioning cases through wave form analysis is suggested.

• The Journal of the Korea Contents Association
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• v.10 no.6
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• pp.307-311
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• 2010

The aim of this study is to investigate PAE, as the result of the test of kVp accuracy, according to detector measurement method. Based on the indicated value of 70kVp, each distance between a focus and a kVp meter was 100cm, 80cm and 60cm and the angle of X-ray tube was set on $5^{\circ},\;10^{\circ},\;15^{\circ},\;20^{\circ},\;25^{\circ},\;30^{\circ}$. Each indicated value, 60kVp, 70kVp, 80kVp, 90kVp and 100 kVp, was used compare Small focus with Large focus. As a result, PAE on the side of cathode was higher than it on the side of anode in the case of 100cm and PAE on the side of anode was higher in the case of 80cm and 60cm. The coefficient rate was stable both the side of cathode and anode in the case of 100cm and it was fluctuated in the case of 80cm and 60cm. PAE in the case of Small focus was higher than Large focus and it was disproportionate to an indicated value. Error rate was in inverse proportion to the indicated value.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.373-381
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• 2017

Kyeonggi Provincial Government is considering double decker bus service to solve the problem of heavy rush hour traffic. However, the height-to-width ratio is more than 1.16 times larger than that of a general high-speed single decker bus, and the center of gravity is higher. This could cause driving stability problems, such as turnover and breakaway from the lane, especially under strong side-wind conditions at high speed. In this numerical study, the driving characteristics of a model double decker bus were reviewed under side-wind and superelevation conditions at high driving speed. The rolling, pitching, and yawing moment of the model bus were calculated with CFD numerical simulation, and the results were compared to the recovery angular moments of the model bus to evaluate the dynamic stability under given driving conditions. As the model vehicle moves on a straight level road, it is stable under any side-wind conditions. However, on a curved road under side-wind conditions, it could reach unstable conditions dynamically. There is a chance that the bus will turn over when it moves on a curved road with a radius of gyration less than 100 m under side-wind (15 m/s). However, there is a very small chance of breakaway from the lane under any driving conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.49-55
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• 2017

Most motor cases adopt deep drawing products, which are excellent in waterproof functions, concentricity, right angle, and quality. In addition, the blower motor and seat motor, which are installed in the car interior and do not require waterproof function, adopts a multi-forming manufacturing method. The deep drawing process requires an expensive transfer press that can digest approximately 12 processes, such as drawing, trimming and piercing. On the other hand, products can be produced with low investment because the multi-forming method is composed of one multi-forming machine or one multi-forming machine and one press. The multi-forming machine is a high-priced facility that is mostly imported and a bending / shearing process multi-foaming machine, which was developed by domestic small and medium-sized enterprises, is not enough to reduce the production cost. An integral multi - forming machine is used as a limited working method for thin material and small products. A large product and thick material has a high shear load. A large product and thick material has a high shear load and uses a single crank press. After blanking, the worker manually feeds the material to a multi-forming machine. When the bending operation is performed in the multi-forming machine, it is transferred to the press again to calibrate the dimensions. This variance in work processes has resulted in lower cost competitiveness due to the lower productivity, quality issues, and excessive operator input. The aim of this study was to establish a stable and cost - effective production system through bending / shearing process separation and facility automation.

• Journal of the Korean Geotechnical Society
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• v.31 no.5
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• pp.35-46
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• 2015

In this study, the behavior of self-supported earth retaining wall with stabilizing piles was investigated by using a numerical study and field tests in urban excavations. This earth retaining wall can provide stable support against lateral earth pressures through its use of stabilizing piles that provide passive resistance to lateral earth pressures arising due to ground excavations. Field tests at two sites were performed to verify the performance of instrumented retaining wall with stabilizing piles. Furthermore, detailed 3D numerical analyses were conducted to provide insight into the in situ wall behavior. The 3D numerical methodology in the present study represents the behavior of the self-supported earth retaining wall with stabilizing piles. A number of 3D numerical analyses were carried out on the self-supported earth retaining wall with stabilizing piles to assess the results stemming from wide variations of influencing parameters such as the soil condition, the pile spacing, the distance between the front pile and the rear pile, and the pile embedded depth. Based on the results of the parametric study, the maximum horizontal displacement and the maximum bending moment significantly decreased when the retaining wall with stabilizing piles is used. Moreover, the horizontal displacement reduction effect of influencing parameters such as the pile spacing and the distance between the front pile and the rear pile is more sensitive in sandy soil, with a higher friction angle compared to clayey soil. In engineering practice, reducing the pile spacing and increasing the distance between the front pile and the rear pile can effectively improve the stability of the self-supported earth retaining wall with stabilizing piles.

• The Journal of Engineering Geology
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• v.10 no.1
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• pp.1-12
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• 2000

Heaving of road and subsidence of slope took place at the Wiri region of the local highway 999 in Gyeongsangbukdo, Korea after heavy rain in the next year of construction. Although the state government had performed remedial treatments by reducing the angle and the height of the slope, deformation had never stopped. Therefore, we have preformed the analysis of deformation and stabilityof the slope. Study area consists of the Cretaceous shale, siltstone and sandstone and two faults are found. The major deformation occurred by sliding of rock mass along faults after heavy rain because not only thepore pressure at the fault plane and the unit weight of sliding mass increased, but did the shearstrength of saturated fault clay become very low. The decrease in shear strength of saturated fault clayis the major factor among the reasons for deformation. Numerical simulations using limit equilibriummodel, finite difference model and finite element model were performed for eight cross sections.Although safety factors are above 1.7 during the dry season, they become below 1.0 when groundwaterlevel raises to surface. The maximum displacement is about 15-3Ocm. However, safety factors increasedto above 2.4 and the maximum displacement is below 2.08cm after remedial treatment, Indicating thatthe slope becomes stable.