• Tribology and Lubricants
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• v.31 no.6
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• pp.294-301
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• 2015

In this paper, we predict the rotordynamic force coefficients of tilting pad journal bearings (TPJBs) with rocker-back pivots, and we compare the predictions to recently published predictions and test data. The present TPJB model considers the rocker-back pivot stiffness calculated based on the Hertzian contact-stress theory, which is nonlinear with the application of a force . For the five-pad TPJB in load-between-pad and load-on-pad configurations, the predictions show the pressure- and film-thickness distributions, the deflection and stiffness of the individual pivots, and bearing stiffness and damping coefficients. The minimum film thickness and peak pressure occur at the bottom pad on which the applied load is directed. Because of the preload, the pres- sure is positive even at the upper pad in the opposite direction to the applied load. The pivot deflection and stiff- ness are maximum at the bottom pad that receives the heaviest pressure load. The predicted stiffness coefficients increase as the static load and rotor speed increase, while the damping coefficients decrease as the rotor speed increases, but increase as the static load increases. In general, the predicted stiffness coefficients agree well with the test data. The predicted damping coefficients overestimate the test data, particularly for large static loads. In general, the current predictive model considering the pivot stiffness improves the accuracy of the rotordynamic performance compared to previously reported models.

• Journal of the Korean Arthroscopy Society
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• v.10 no.2
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• pp.141-147
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• 2006

Purpose: To compare the clinical and radiological results of anterior cruciate ligament(ACL) reconstruction using hamstring autograft and tibialis tendon allograft. Materials and Methods: Twenty four ACL reconstructions using hamstring autograft and 30 using tibialis anterior tendon altograft were followed up at least 1 year. We performed femoral tunnel fixation with Ligament Anchor(LA) screw and tibial tunnel fixation with biodegradable interference screw. Evaluations included Lysholm knee(LK) score, Tegner activity scale, Lachman test, Pivot-Shift test, Quardriceps atrophy, incision site numbness, anterior knee pain and instrumented anterior laxity with $Telos^{(R)}$ device. Results: Preoperativ mean LK score was $60.3(18{\sim}82)$ in autograft group and 61.2(25-80) in allograft group. Mean LK score improved to $91.6(68{\sim}100)\;and\;92.6(77{\sim}100)$ respectively. Activity level, using Tegner activity scale, slightly decreased compared with that of Preinjury state in both groups. Lachman test, pivot-shift test, Quadriceps atrophy, anterior knee pain, incision site numbness, and anterior drawer test using $Telos^{(R)}$ device showed no significant difference between two groups (p>0.05). Conclusion: In performing the ACL reconstruction, there was no statistically significant difference between hamstring autograft group and tibilis anterior allograft group in clinical or in radiological results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.1014-1023
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• 2008

Subway electric trains need to be faster for accommodation of long distance passengers. The faster run of the existing trains results in deterioration of ride quality due to noise and vibration. To reduce the noise and vibration of the electric train, a running test of the electric train was performed and an ADAMS/Rail model was set up to verify the running test results. The experimental results show that the sources of the cabin noise and vibration basically comes from the irregularity of the railroad track and the deterioration of the connection part between cabin and bogie. Consequently for mitigation of noise and vibration of the electric train, the redesign of the center pivot with softer stiffness and the minimization of rail irregularity are necessary. the frequent maintenance of the train will lead to better comport.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.318-322
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• 1999

An analytical study about dynamic behavior of center pivot rocker arm type valve train system equipped with roller of diesel engine is developed. At first, a mathematical model for the dynamic analysis has been set up using the lumped parameter method. In that model, valve spring is divided as some mass elemehts so as to simulate spring surging, Then, how the design parameters, such as valve mass, rocker arm inertia, valve spring stiffness, and initial load on valve spring, affect valve dynamic behavior especially in the valve close area is scrutinized.

• Tribology and Lubricants
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• v.5 no.2
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• pp.77-82
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• 1989

The influences of ram pressure on the performances of tilting-pad journal bearings are investigated experimentally. The test rig consists of a single tilting-pad and a rotating journal. Film thicknesses and pressure distribution of the lubricating film are measured continuously for several values of coordinate of the pivot position and journal speed. The findings of the investigation are as follows: (]) According as the journal speed increases the ram pressure increases, maximum pressure decreases and the pivot position which maximize the minimum film thickness shifts toward the leading edge. (2) The ram pressure makes it possible to generate the converging wedge and the positive pressure between the pad and the journal even when the pad is supported at the points between the leading edge and the center of the pad. (3) The influence of the ram pressure on the performance of tilting pad bearings is significant and must be considered in the design of these bearings.

• Journal of the Korean Arthroscopy Society
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• v.1 no.1
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• pp.26-30
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• 1997

Recently, the incidence of anterior cruciate ligament injury is rapidly increasing because many young Korean are actively participating in sports activities including basketball, skiing and soccer. Sometimes acute ACL injuries arc misdiagnosed as sprain because of pain and muscle spasm. An accurate physical examination and careful history taking are very important to diagnose the ACL injuries. Therefore author described the skill of history taking and the technique of physical examination to diagnose ACL injuries. The most sensitive test is the Lachman's test, which is performed with the knee in 200 of flexion, the femur stabilized with full flexed examiner's knee placed behind patient's distal thigh and one hand of examiner, and the proximal tibia grasped with the other. The pivot shift test is a passive motion test that attempts to subluxate the tibia anteriorly, then have it reduce rapidly. The pivot shift test is very sensitive test to diagnose the chronic ACL injuries.

• International Journal of Contents
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• v.7 no.3
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• pp.13-18
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• 2011

Oriental medicine statistics are essential in research planning, research evaluation, and policy decision based on objective data. However, integrated administration of such statistics is not presently possible in the oriental medicine field, which has been slow in incorporating information communication technology. In an effort to address this problem, the Korea Institute of Oriental Medicine (KIOM) developed an oriental medicine statistical system in 2009, and the system has been offered in the traditional medicine information portal of OASIS. However, according to a 2010 survey targeting OASIS users, those surveys reported that needs for a system where various statistical data can be extracted via an interactive approach to multidimensional data. As a result of an analysis of the functions of the existing system, it was found that it is necessary to array and arithmetically analyze Stats Value, Drill Up & Drill Down, and Pivot. To this end, the existing DB schema should be redesigned. Based on our analysis result, we redesigned the database into a structure that is applicable to the reverse pivot algorithm. We used J2EE/JSP and a Flex framework to design and develop an oriental medicine statistical system that can provide multidimensional statistical data. Considering that the improved oriental medicine statistical system is planned to be offered by OASIS of KIOM, utilization and value of oriental medicine statistical data are expected to be enhanced.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.450-452
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• 2004

This paper analyzes some important achievements in Ergonomics field in CRT industry. After introducing principal regulatory requirements for CRTs, including ISO 9241 and TCO standards, the paper indicates some theoretical research in ergonomics of the display devices, such as new contrast parameter for appraising the display devices and effects of environment on visual performance at the ergonomic. Then, as the pivot of this paper, some practical progress, in the ergonomics field in CRT manufacturing , are described, such as vacuum sputtering process for advanced CRTs, new developed wet process for getting the multi-coating layers on surface of the panel.

• Journal of the Korean Arthroscopy Society
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• v.11 no.2
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• pp.85-91
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• 2007

Purpose: To analyze the clinical results and second look arthroscopic findings of anterior cruciate ligament(ACL) reconstruction with a tibialis anterior tendon allograft and a hamstring tendon autograft. Materials and Methods: We reviewed the cases of athroscopic ACL reconstructions using allogenous tibialis anterior(TA) tendon and autogenous hamstring tendon done from March, 2002 to August, 2005 and followed-up more than 1 year. The 250 cases were included in this study and allogenous TA tendon was used in 150 cases and autogenous hamstring tendon in 100 cases. The mean follow-up period was 15 months and 14 months, respectively. The clinical evaluation was done by Lachman test, Pivot shift test, KT-1000 arthrometer and International Knee Documentation Committee(IKDC) knee score. Graft tension, synovial coverage were observed in cases of second look arthroscopy. Results: At final follow-up, there was no significance between the two groups in clinical examination. On second look arthroscopy, synovial coverage was better in autogenous hamstring tendon group than allogenous TA tendon group(p=0.005). But no difference was found in graft tension(p>0.05). Conclusion: There were no significant differences between the two groups in the clinical results. But autogenous hamstring tendon group had better synovial coverage than allogenous TA tendon group in second look arthroscopy.

• Journal of Korean Orthopaedic Sports Medicine
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• v.10 no.2
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• pp.47-53
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• 2011

Purpose: As the number of the anterior cruciate ligament (ACL) reconstruction has increased, the incidence of revision of ACL reconstruction due to reconstruction failure has been also increased. Therefore, authors analyzed the reason of the failure of ACL reconstruction and the clinical result of the ACL revision. Materials and methods: From February 1998 to July 2010, we selected 36 cases which was followed at least 12months after the ACL reconstruction failure. Duration from reconstruction to revision, the average duration was 60 months (5~334) and on first reconstruction, we used allograft on 23 cases (63.9%) and autograft on 13 cases (36.1%). For the main symptom of ACL reconstruction failure, instability was the most common symptom, and 35 cases (97.5%) were undergone only one reconstruction and 1case (2.5%) was undergone two reconstruction. Clinical results were evaluated by Lysholm knee joint score, pivot shift test, and Telos device. Results: Average follow-up duration of the patients was 21 months (12~40), and the reason for the ACL reconstruction failure, trauma was most common by 19 cases (52.8%), malposition of the femoral tunnel was 13 cases (36.1%), malposition of the tibia tunnel was 1case (2.8%), and failure of osteointegration was 3 cases (8.4%). On performing the ACL revision, we used allograft on 34 cases (94%) and autograft on 2 cases (6%), and 21 cases accompanied injury of the meniscus (medial meniscus 14 cases, lateral meniscus 7 cases). Lysholm knee joint score was improved from 66.5 points, preoperatively to 92 points on last follow-up (p<0.01). In most cases, patients were satisfied (92%) with the operation results. Tegner activity score was also improved from 2.0 points preoperatively to 6.2 points on the last follow-up. On Lachman and pivot sift test, 33 cases and 30 cases were improved to grade I respectively, and on stability test using Telos device, the bilateral difference was improved from mean 15.5 mm preoperatively to 4.5 mm on the last follow-up. Conclusion: After 1 year follow-up, Revision of ACL had a little anterior instability but it showed satisfactory result on clinical result and patient's subjective satisfaction.