• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.93-98
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• 1999

Generally, the - life of die is limited by fatigue fracture or dimensional inaccuracy originated from wear. In this paper, to predict the fatigue life of the dissimilar materials die, the stress and stxain histories of die can be predicted by the analysis of elasto-plastic finite element neth hod and the elastic analysis of die during the process analysis of workpiece. Using heat shrink fit analysis, initial stress of the k r t die is computed. Also, the stress-life curve of die material can be obtained through experiment. With the above two facts, we propose the analysis method of predicting fatigue life in die. In the proposed model, tlz analysis of elastic-plastic finite element method for material is carried out by using ABAQUS. Surface force resulted from the contacting border of the die and workpiece is tmnsformed into the nodal force of die to implement elastic analysis. Besides, the proposed analysis model of die is applied to the one material and the dissimilar materials extrusion die.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.34-39
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• 2014

In this study, the structural analysis and the modal analysis are conducted to investigate the stress level, the deformation characteristics and the natural modes of the casing of a planetary gear reducer for a 800kW grade pulverizer mill. The casing is subjected to the load, 2800 kN, from the lump coals in the pulverizing process. Because of the symmetry, the half portion of the reducer casing is modeled for the stress analysis. But the full model is used to find out the eigenvalues and natural modes for the modal analysis. The contact conditions are applied between the thrust pad bearing and the adjacent contacting parts. The results shows that the casing structure has the sufficient strength and stiffness to support the load under consideration. ANSYS version 15 is employed to perform the numerical study.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.81-88
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• 2001

To study the influence of the shape of contacting bodies (especially the end profile) on slip regime, wear test is conducted in the case of the contact between tube and support. Two different end profiles of the support are used such as truncated wedge and rounded punch. During the test, 10, 30 and 50 N are applied as normal force and slip displacement varies between 10-200 $\mu\textrm{m}$. The tube and the support specimens are made of Zircaloy-4 and a specially designed wear tester is used. Tests are carried out in air at room temperature. Wear on the tube is examined by measuring microscope. Partial and gross slip regimes are classified from the observed wear shape. Surface roughness tester is also used to measure the wear depth and contour, from which wear volume is evaluated. The transition from partial to gross slip is also investigated by investigating the considerable increase of wear volume. From the result, the boundary between the partial and the gross slip is newly determined in the conventional fretting map for the present specific contact configuration. Since the transition is related with the amount of energy dissipation from the contact surface so is wear, it is regarded that wear can be restrained by designing a proper shape of support.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.4
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• pp.358-363
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• 2008

Ultrasonic nonlinearity has been considered as a promising method to evaluate the micro damage of material; however, its magnitude is so small that its measurement is not easy. Thus, in this study, we investigate the effects of such experimental system dependent factors in the measurement of ultrasonic nonlinear parameter by using contact PZT transducer. Experimental results showed that the effect of system dependent nonlinearity is reduced when the contact pressure and transducer input voltage are sufficiently large. These results will be very useful to find out the proper experiment condition to measure rather accurate nonlinear parameter.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.98-104
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• 2020

In this work, a study on the 5-axis machining of ball gear cam is conducted which is a continuation of reference [1]. The ball gear cam used in this study delivers motion in conjunction with the ball supported by the turret. Therefore, it requires carbonizing heat treatment and is usually completed using a 4-axis machining with a carbide ball end mill. If the nose part of the ball end mill is not allowed to participate in the machining, then CBN tools without the nose part can be used. However, machining of certain shapes can be carried out only by contacting the ball in some of the areas on either side which can improve the surface of the machining. This requires a 5-axis machining in order to maintain a constant angle for the processing path. Therefore, in this work, the 5-axis machining method is studied in order to maintain the direction of the cutter axis at a constant angle with the tangent direction of the curve-ball gear cam. Furthermore, the 5-axis machining program for the ball gear cam was developed and the machining experiment was completed and verified.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.8
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• pp.63-72
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• 1995

Closed-die forging of spur gears with hollow cylindrical billet has been analysed by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, an involute curve has been introduced to represent the forging die profile. In the analysis, the deformation region has been divided into nine zones. A constant frictional stress has been assumed on the contacting surfaces. Utilizing the formulated velocity field, numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth and friction factor, on the forging of spur gears. Hardness and accuracy of forged gears are measured. The following results have been obtained: (1) It is verified that an axisymmetric deformation zone exists between root circle and center of gear through forged gears. (2) The average relative forging pressure is predominantly dependent on the number of teeth and increases near the final filling stage as the addendum modification coefficient increases. (3) Close agreement was found between the predicted values of forging load and those obtained from experimental results.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.6
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• pp.526-534
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• 2001

Purpose : The objective of this study is to ascertain whether the positive exists among the frenum length, the tongue movement and the speech and to present the normal range of tongue movement and guidelines for the choice of surgery, observation if necessary. Materials and Methods : 180 patients were evaluated. We divided 180 patients into 6 group by age. Each group was separated as follows; the age of 2.5-4, 5-6, 7-9, 10-12, 16-18. We measured the frenal length, the range of tongue motion and evaluated the speech so that we really questioned about the positive relationship between the tongue-tie and speech. We let the patient exercise the protrusive both(right, left) laterotrusive superior movement of the tongue. During these movements, we measured the distance between the vermilion border and the tongue tip. We also measured the distance from the tongue tip to the point contacting the upper lip with dorsum of the tongue during the maximal protrusive movement of the tongue. Three linear measurement of the anterior, inferior segment of the tongue including the lingual frenum, are made. These measurements are as follows: 1. Distance A. Free anterior portion of the tongue from the point of frenular insertion to the tongue tip. 2. Distance B. The distance from the initiating point of the lingual frenum to the point connecting the two sublingual carundcles to the lingual frenum perpendicularly. 3. Distance C. The distance from the point contacting the line crossing the sublingual caruncles with the lingual frenum to the terminating point of the lingual frenum. We transform three linear measures into a statistical ratio, A/(A-B+C), representing the length of the free portion of the tongue compared with the total sublingual dimensions. In addition, we assessed the speech through Picture Consonant Articulation Test(PCAT) and tried to find out the relationship between the length of the lingual frenum and speech. Conclusion : As people are born, they have small and restricted tongue. As people grow old, tongue motions are more liberate, and unrestricted and they can speak so freely. Therefore we suggest that until age 5, oral and maxillofacial surgeons postpone the surgery if not urgent, evaluate the maximal lingual motions and PCAT according to this article and observe their changes.

• Journal of International Area Studies (JIAS)
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• v.13 no.4
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• pp.251-284
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• 2010

Through specific cases, this article examines the causes and measures to overcome cultural divergences most frequently encountered by Koreans living in Vietnam and Korean-contacting Vietnamese in terms of mode of communication, mode of living and mode of doing business. Historical reality proves that Vietnam and Korea have a lot in common in history, culture and society, due to the influence from the Chinese culture on both countries. However, each country has its own acculturation, hence, there exist, apart from the normal dissimilarities, differences between the two countries especially in natural environment andpolitical systems. As a result, in Vietnam, Koreans and Vietnamese have met with quite a lot of divergences in communication, business and living activities. In order to overcome these cultural divergences, in addition to the ceaseless efforts made by Koreans in Vietnam and Korean-contacting Vietnamese, there should be concern, assistance as well as cooperation between the people and the authorities of the two countries. We should draw lessons from the groundless or trivial affairs which, springing from the Chinese people's dislike for Koreans, have been blown up and disseminated on the internet; where by we are to reconsider the relationship between Koreans and Vietnamese. What is more, Korea still feels historically ashamed to have sent nearly 350,000 soldiers to the wa rin Vietnam for economic purposes in the past. As our predecessors brought about that historic shame to get bread for our fatherland in exchange, our generation today should approach Vietnam out of a sense of responsibility towards history. Having experienced a period of economic difficulties, Vietnam innovated and started its open-door policy in 1987. However, this event should not be regarded as the reason for us to approach Vietnam with only one rigid economic principle.

• Journal of Oral Medicine and Pain
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• v.25 no.2
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• pp.235-240
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• 2000

This study was carried out among 34 patients who visited Yonsei Dental Hospital from 1996. 1. to 1999. 5 for trigeminal neuralgia. By studying the patient's treatment prior to visiting our hospital, features of trigeminal neuralgia, treatment process of trigeminal neuralgia, prognosis of treatment, consultation with other professions and involvement of surgery, etc., the results are as follows: 1. 67.7% of onset age range from 40s to 60s, and average age is 50.2. 2. Ratio of right to left involvement is 1:2.1, male to female ratio is 1:1.9. 3. Occurrence rate of each branch is V3(44.1%), V2(11.8%), V1+V2+V3(11.8), V1+V2(8.8%). 4. Treatments prior to admission to our hospital are extraction(5.9%), endodontic treatment(5.9%), medication(11.8%), Oriental Medicine treatment(5.9%). 5. Routes of admittance to our hospital are by their preference(55.9%), local clinic referral(32.4%), E.N.T referral(5.9%), Neurology referral(5.9%). 6. 70.6% of patients treated at our hospital who were relieved of symptoms, were referred to Neurology(66.7%) and Pain Clinic(33.3%) for the reason of relapse, side effects of the drug itself, incomplete relief of pain. 7. 2 patients who were referred to medical part showed brain vessels contacting trigeminal nerve root on Brain MRangiography. But pain is being controlled by medication and no specific surgical procedure was carried out. The results show that 17.7% of patients admitted received inappropriate early treatment. In order to relieve tooth loss and patient's psychologic stress due to inappropriate treatment, precise differential diagnosis must be made among local teeth disease and idiopathic facial pain. Medication may show side effects of the drug itself, incomplete relief of pain or relapse of symptoms. Therefore, to treat trigeminal neuralgia appropriately by drug injection, surgery or radiation therapy, consultations among dentists, neurologists and anesthesiologists are required.

• Composites Research
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• v.19 no.4
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• pp.7-14
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• 2006

Interfacial shear strength between epoxy and carbon fiber has been analyzed utilizing the microbond specimen with an epoxy micro-droplet adhered onto single carbon fiber. The interfacial shear stress distributions along the fiber/matrix interface were calculated by finite element analysis using three kinds of finite element models such as droplet model, circular-crosssection model and pull-out model. Conclusions were obtained as follows. (1) Interfacial shear stress distribution showed that larger stresses were concentrated in the fiber/matrix interface for microbond test than for pull-out test. Thus, debonding at the fiber/matrix interface during microbond test was liable to occur at low load level. (2) Microbond test showed higher interfacial strength which was caused by various effects of micro-droplet geometry and size as well as stress concentration in the region contacting with the micro-vise tip.