• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.414-421
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• 2001

The present study is conducted to investigate the local heat/mass transfer characteristics on the shroud with blade tip clearances. The relative motion between blade and shroud has little influence on the overall heat transfer characteristics, except some local effects. Therefore, the relative motion between the blade and shroud is neglected in this study. A naphthalene sublimation method is employed to determine the detailed local heat/mass transfer coefficients on the surface of the shroud. The tip clearance is changed from 0.66% to 2.85% of the blade chord length. The flow enters the gap between the blade tip and shroud at the pressure side due to the pressure difference. Therefore, the heat/mass transfer characteristics on the shroud are changed significantly from those with endwall. At first, high heat/mass transfer occurs along the profile of blade at the pressure side due to the entrance effect and acceleration of the gap flow. Then, the heat/mass transfer coefficients on the shroud increase along the suction side of the blade because tip leakage vortices are generated and interact with the main flow. The results show that the heat/mass transfer characteristics are changed largely with the gap distance between the tip of turbine blade and the shroud.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.12-13
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• 2021

Methods for the manufacture, erection, and assembly of heavy frame modules were proposed. Interferences among precast members were prevented by using bolted metal plates for dry precast beam-to-column joints during assembly with a clearance for tolerance implementing grouted concrete filler plates instead of metal filler plates. Clearances for tolerances were provided to avoid conflictions among components during erection phases. These gaps were, then, grouted by high-strength mortar. The constructability of new connections of a beam-to-column joint using bolted metal plates for precast structures was examined using a full-scale assembly test in which practical observations indicated that members could be aligned and placed accurately in both horizontal and vertical directions, leading to a fast and convenient assembling. Bolt holes of the endplate were properly aligned using couplers with 30 mm fastened length embedded in the columns. The assembly test demonstrated the erection safety and structural stability of the proposed joints that were without filler plates when they were subjected to heavy loads at the time of their erection. The facile and rapid assembly of precast beam-to-column connections with a 30 mm tolerance was observed. The proposed assembly method is rapid, sustainable, and resilient, replacing the conventional methods of concrete frame construction, offering a connection that can be used in constructing infrastructure, such as buildings and pipe-rack frames.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.796-802
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• 2018

The effects of inner liquid sloshing on vessel motions are a well-known factor. It was investigated experimentally and numerically. In this regard, the study of many efforts to reduce natural phenomena of vessel motions by adopting special devices especially for roll motions. Among many devices, inserting baffles in the inner liquid tank is very common. In this study, one investigated the vessel motions with inner sloshing tanks with baffles inside. For the numerical simulation, one employed a dynamically coupled program between boundary-element-method-based vessel motion analysis program and a particle-based computational fluid dynamics program. Comparing corresponding experimental results validated the dynamically coupled program. The validated coupled program was used to simulate vessel motions, including sloshing effects with various lengths of inner baffles. The simulation results show that not only the filling ratio of inner liquid, but also the length of clearance due to baffles influenced the vessel motions. The significant point of this study was that the natural frequency of vessel motions can be maintained irrespective of the amount of filling ratio through adjustment of the clearance. In a future study, the effects of various numbers of baffles with various clearances would be conducted to percuss the possibility of vessel motion control with inner liquid sloshing effects.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.869-877
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• 2020

The power consumption in the low consistency (LC) refining is an important indicator for the optimal control of the process and it is composed of the net power and the no-load power. The refining efficiency and process characterization of LC refining are directly affected by power consumption. In this paper, the effect of pulp consistency and average fiber length on the power consumption and refining efficiency were studied through the LC refining trials conducted by an experimental disc refiner. It is found that the curve of power-gap clearance can be divided into constant power section, power reduction section, and power increase section. And the no-load power and the adjustable domain of loading applied by the refining plates will increase as the increase of pulp consistency, while the increase of net power is larger than that of no-load power which makes the increasing of refining efficiency. Meanwhile, the adjustable domain of loading applied by the refining plates can be slightly improved by increasing the average fiber length, but its effect on the no-load power in the LC refining process can be neglected. The study of power consumption in LC refining is of positive significance for the proper selection of pulp properties in LC refining, in-depth exploration of refining mechanism, and energy consumption reduction in refining.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.46-55
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• 2014

PCB design technology for high-speed transmission line has been developed continuously. Adapting to the high capacity of the communication system, switch fabric interface used for backplane is being standardized to accommodate more than 10Gbps serial interface. In this paper, various computer simulations are performed to compare the performance of each transmission line per length according to PCB material, and also to analyze the effect from via stub length and crosstalk, for the purpose of applying 11.5Gbps serial interface as a switch fabric interface in tera-bit switching system. As a result of the simulation, important design issues, such as PCB material of each board supporting 8dB improvement in transmission loss using low loss PCB, maximum available stub length on transmission line via, whether or not to apply the backdrill process to the via, and the clearance of the differential pair between transmission lines, are determined. The most efficient system architecture which could be applied 11.5Gbps serial interface in all switch fabric interfaces is defined from the simulation results.

• Journal of Korean Neurosurgical Society
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• v.50 no.3
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• pp.166-172
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• 2011

Objective : The intralaminar screw (ILS) fixation technique offers an alternative to pedicle screw (PS) and lateral mass screw (LMS) fixation in the C7 spine. Although cadaveric studies have described the anatomy of the pedicles, laminae, and lateral masses at C7, 3-dimensional computed tomography (CT) imaging is the modality of choice for pre-surgical planning. In this study, the goal was to determine the anatomical parameter and optimal screw trajectory for ILS placement at C7, and to compare this information to PS and LMS placement in the C7 spine as determined by CT evaluation. Methods : A total of 120 patients (60 men and 60 women) with an average age of $51.7{\pm}13.6$ years were selected by retrospective review of a trauma registry database over a 2-year period. Patients were included in the study if they were older than 15 years of age, had standardized axial bone-window CT imaging at C7, and had no evidence of spinal trauma. For each lamina and pedicle, width (outer cortical and inner cancellous), maximal screw length, and optimal screw trajectory were measured, and the maximal screw length of the lateral mass were measured using m-view 5.4 software. Statistical analysis was performed using Student's t-test. Results : At C7, the maximal PS length was significantly greater than the ILS and LMS length (PS, $33.9{\pm}3.1$ mm; ILS, $30.8{\pm}3.1$ mm; LMS, $10.6{\pm}1.3$; p<0.01). When the outer cortical and inner cancellous width was compared between the pedicle and lamina, the mean pedicle outer cortical width at C7 was wider than the lamina by an average of 0.6 mm (pedicle, $6.8{\pm}1.2$ mm; lamina, $6.2{\pm}1.2$ mm; p<0.01). At C7, 95.8% of the laminae measured accepted a 4.0-mm screw with a 1.0 mm of clearance, compared with 99.2% of pedicle. Of the laminae measured, 99.2% accepted a 3.5-mm screw with a 1.0 mm clearance, compared with 100% of the pedicle. When the outer cortical and inner cancellous height was compared between pedicle and lamina, the mean lamina outer cortical height at C7 was wider than the pedicle by an average of 9.9 mm (lamina, $18.6{\pm}2.0$ mm; pedicle, $8.7{\pm}1.3$ mm; p<0.01). The ideal screw trajectory at C7 was also measured ($47.8{\pm}4.8^{\circ}$ for ILS and $35.1{\pm}8.1^{\circ}$ for PS). Conclusion : Although pedicle screw fixation is the most ideal instrumentation method for C7 fixation with respect to length and cortical diameter, anatomical aspect of C7 lamina is affordable to place screw. Therefore, the C7 intralaminar screw could be an alternative fixation technique with few anatomic limitations in the cases when C7 pedicle screw fixation is not favorable. However, anatomical variations in the length and width must be considered when placing an intralaminar or pedicle screw at C7.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4D
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• pp.369-376
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• 2010

At present, many problems in traffic operation and safety occurs since there is no clear design criteria on designating the not-permitted entrance/exit section at curb areas within complex areas. Even, there is no specific and detailed researches on the not-permitted entrance/exit section by now. This research calculated the proper length of the entrance/exit section at curb areas by dividing the access not-permitted section into the two sections. First, the calculation of the entrance section was done by considering the location of crosswalks, stop line clearance, the queue length of vehicles approaching to second lanes, and marginal distance for safety have been considered. Second, the calculation of the exit section was done by comparing and analyzing the distance between cars of the entrance section according to the investigation point and the distance considering the location of crosswalks, the behavior of exit vehicles and the length of vehicles. In conclusion, by presenting the proper length in consideration of the traffic operation and safety on the access not-permitted section within complex areas, it can be used as a traffic safety improvement alternative and will be contributed in establishing and operating the proper installation criteria for the access not-permitted section within complex areas.

• Tribology and Lubricants
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• v.34 no.4
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• pp.138-145
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• 2018

Elliptical bearings are widely used for large steam turbines owing to their excellent load carrying capacity and good dynamic stability. Power loss in bearings is an extremely important parameter, especially for high turbine capacities. Optimization of operation conditions and design variables such as bearing clearance and bearing length can reduce the power loss in elliptical bearings. Although changes in the oil supply method have served to increase the efficiency of the tilting pad journal bearing, it has not explicitly improved elliptical bearings. In this study, we verify the static characteristics of an elliptical bearing by changing the direction of oil supply. We evaluate the bearing power loss and bearing metal temperature, and compare the bearing performance and reliability in different test cases. The direction of oil supply is $90^{\circ}$ (9 o'clock) and $270^{\circ}$ (3 o'clock) when the rotor rotates in a counterclockwise direction. We use an elliptical bearing with an inner diameter and active length of 220.30 and 110.00 mm, respectively. Bearing power loss and bearing metal temperatures are measured and evaluated by rotor rotational speed, oil flow rate, and bearing load. The results reveal a 20 reduction in the power loss when the direction of oil supply is 90. Furthermore, the oil film on the upper part of the bearing has a high temperature when the direction of oil supply is $90^{\circ}$. In contrast, when the direction of oil supply is $270^{\circ}$, the oil film on the upper part of the bearing is relatively cold.

• Korean Journal of Bronchoesophagology
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• v.15 no.2
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• pp.36-41
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• 2009

Background : Controversy exists whether patients with esophageal carcinoma are best managed with classical Ivor Lewis esophagectomy(ILO) as combined thoracic and abdominal approach or transhiatal esophagectomy(THO). The THO approach is known to be superior with respect to operative time, morbidity and mortality, and length of stay, especially at poor pulmonary function patient, but may represent an inferior cancer operation due to inadequate mediastinal clearance compared with ILO. Accordingly, we estimated the THO role at esophageal cancer to compare each operative approach. Material and Method : From January 2002 to December 2007, we performed a retrospective review of all esophagectomies performed at Keimyung University Dongsan Medical Center; 36 underwent THO, and 11 underwent ILO. Result : There were all men and squamous cell carcinoma but 1 woman at ILO group, 2 women at THO group. There were no significant differences between THO and ILO with age, sex, location of tumor, mean tumor length. There were significant differences at preoperative pulmonary function test(In ILO group, average FEV1 is $2.65{\pm}0.6\;L/min$ and iIn THO group, average FEV1 is $2.07{\pm}0.7\;L/min$). The amount of blood transfusion, hospital stay, leak rates and respiratory complication, hospital mortality rate were not significantly different. Conclusion : There was no significant difference in the post-operative complication, hospital mortality rate, long-term survival of patients of both operative method. THO method had lower mobidity and mortality at poor pulmonary function patient than ILO method. Hence, THO is a valid alternative to ILO for patients with poor general condition or expected post-operative respiratory complication.

• Korean Journal of Applied Biomechanics
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• v.21 no.5
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• pp.561-571
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• 2011

The purpose of this study was to perform the kinematic analyses of the women's pole vault skills in IAAF World Championships Daegu 2011. Subjects were the 1st through 8th place finishers in the pole vault. The kinematic analyses were divided into four phases: two dimensional run up analysis, and three dimensional analyses for the remaining plant, swing up, and extension phases. Run-up variables consisted of run up distance, number of steps, average step length, ratio of step length to height, average velocity at the final 5~10 m, approach position. Three variables were analyzed during plant: pole angle, center of gravity (COG) velocity, and COG takeoff angle. Swing up phase variables included: pole flection angle, COG velocity (horizontal, vertical, resultant), COG trajectory and bar approach angle of COG. Compared to the 2009 World Championships in Berlin, the average vault height increased, while run up velocity and approach position were almost unchanged. However, horizontal velocity during the last two steps of the final approach decreased noticeably compared to speeds from 1990. These results reflect the change in both technique and physical fitness in pole vaulters. During extension, the peak height of COG surpassed the clearance height by an average of 0.11m. These specific results can help coaches and athletes modify training and improve performance.