• Transactions of Materials Processing
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• v.11 no.3
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• pp.255-261
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• 2002

The grain size of 7010 Al alloy was refined to submicrometer level by using equal channel angular pressing (ECAP) and additional warm rolling. The mechanisms of grain refinement in ECAP process were fragmentation of coarse grain to ultra fine subgrains after a few passes and continuous recrystallization of the subgrains with the increase o( passes. Because of ultrafine grain size, essentially low temperature and high strain rate superplasticity was observed after ECAP process and warm rolling to form a sheet metal. The maximum elongation of 700% was obtained for an ECA pressed specimen after IS passes without warm rolling at $450^{\circ}C$ with strain rate of 5x$10^{-3}$/sec.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.450-455
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• 2017

A shield connector is an automotive electrical component that is used to connect electrical wiring in a vehicle. This part is made by progressive pressing using a phosphor bronze material with high electrical conductivity. The shape of the product is not complicated, but plastic forming techniques are required, such as deep drawing and bending, as well as shearing techniques such as piercing and notching. The finite element method was used to model the process. The strip layout design stage of the progressive die makes it possible to examine the thickness change, the stability of the forming process, and the spring-back. As a result of this analysis, it is possible to predict the correction values for the tendency of cracks, wrinkles, and incomplete plastic deformation, and to identify possible problems in advance. As a countermeasure against the forming error caused by the drawing process analysis, the drawing shape was modified and applied in the process design. For effective material utilization, a 3D strip layout was designed using an optimized blank shape based on nesting. The results improve the crack stability and spring-back of shield connector products produced through progressive pressing.

• Transactions of Materials Processing
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• v.21 no.3
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• pp.160-163
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• 2012

In this paper, a new approach to finite element analysis for tube swaging is presented. An analysis model is developed with emphasis on the pusher that imposes back pressure in order to keep the workpiece from slipping along the die-workpiece interface especially when tapered dies are used. A rigid-plastic finite element method is employed. The approach is to simulate the tube swaging process and the results are compared quantitatively with predictions, showing close agreement with each other.

• Tribology and Lubricants
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• v.24 no.6
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• pp.315-319
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• 2008

This paper presents the interface bonding characteristics between a phosphor bronze and a steel plate for pin-bush bearings. The pin-bush bearing is an important component in which is used to reduce a friction loss and a wear against the piston pin. The pin-bush bearing is manufactured by hot-pressing a phosphor bronze and a back metal of a steel plate. This paper investigated the bonding interface characteristics in which is manufactured by melting a copper based bronze and a steel plate. The hardness from the inner surface of a bronze to the outer one of steel has been measured using a Vickers hardness tester. The experimental results show that the hardness of a bronze is superior to that of the conventional bronze and the transient hardness of pin-bush bearings is gradually increasing to the hardness of the steel back metal. This means that the bonding interface zone of pin-bush bearings may be fabricated by defusing a bronze to the steel plate due to a density difference between two materials.

• Journal of Korean society of Dental Hygiene
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• v.12 no.4
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• pp.685-693
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• 2012

Objectives : This research was conducted to find the subjective symptoms of musculoskeletal system for main jobs and job posture. Methods : A survey was conducted from September 15, 2011 to October 7, 2011 and 357 dental hygienists were responded. The survey was consisted of the working environment and medical equipments, psycho-social characteristics, health habits and education, job posture, subjective symptoms of musculoskeletal system pain, and so on. Results : In the survey on the frequency of job posture of dental hygienists by jobs, said they cast down or tilt their head by 15 degrees or more or twist or bend their back. The result of the analysis on the subjective symptoms of musculoskeletal system by main job showed that they experienced a pain in neck, shoulder, and back, although the order differed. The order of subjective symptoms of musculoskeletal system for casting down or turning head by 15 degrees or more, twisting or bending back, having shoulders not parallel to the ground, sitting at the end of a chair, and supporting the whole body with one leg or pressing on a pedal for treatment was from the shoulders to the neck to the back. The order of subjective symptoms of musculoskeletal system for having arms too far from the body or hunching for treatment and bending wrists inward or outward for treatment was from the shoulders to the back to the neck. Conclusions : Due to the characteristics of the job which requires one to have a proper view of a patient's oral cavity, most of the postures included casting down of head or bending of back. Therefore a development of new postures is needed to replace the existing job postures which pressure the musculoskeletal system. And shift rotation can be used as a preventive measure.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.110-117
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• 2011

The purpose of this work is to develop of a press forming process for mobile phone battery cover as an alternative to the current manufacturing process by laser welding. This press forming process consists of a combination of bending, side pressing and side bending operations. The dimensional error for each process was investigated by finite element(FE) analysis and the Taguchi optimization method. The spreading of the cover width in the side pressing process was adjusted by modifying the blank shape with a notch. The over-bending method was adopted to compensate the spring-back which occurs after bending. Forming experiments were performed to verify the reliability of the developed press forming process. In addition, the strength of the product was evaluated to verify the suitability of the battery cover manufactured with this new press forming process. The results of the forming experiments indicate that the dimensional accuracy of the battery cover is within the required tolerance. The strength of the battery cover was evaluated to 547N which is larger than required strength of 400N.

• Design & Manufacturing
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• v.10 no.2
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• pp.34-38
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• 2016

In this paper, a transversely isotropic behavior of AZ31 Mg alloy produced by equal-channel angular pressing (ECAP) process was investigated through tensile test and microstructure observation. The effects of initial ECAP pass number on the anisotropic behavior and mechanical properties of the Mg alloy are evaluated after conventional direct extrusion test, which are carried out at a temperature of $200^{\circ}C$. As a result of the tensile test in three directions ($0^{\circ}$, $45^{\circ}$, and $90^{\circ}$ to the extrusion direction of the sheet) at room temperature, elongation of as-extruded AZ31 alloy(ECAP for 0 pass) showed an unusual anisotropic behavior depending on the extrusion direction although the yield strength and tensile strength are similar to the ECAPed AZ31 alloy. After ECAP for 4 passes at $200^{\circ}C$, microstructural observations of ECAPed magnesium alloy showed a significant grain refinement, which is leading to an equiaxed grain structure with average size of $2.5{\mu}m$. The microstructures of the extruded billet are observed by the use of an electron back-scattering diffraction (EBSD) technique to evaluate of the influence on the grain refinement during extrusion process and re-crystallization mechanism of AZ31 Mg alloy.

• Journal of Powder Materials
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• v.31 no.1
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• pp.1-7
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• 2024

This study explores the profound impact of varying oxygen content on microstructural and mechanical properties in specimens HO and LO. The higher oxygen concentration in specimen HO is found to significantly influence alpha lath sizes, resulting in a size of 0.5-1 ㎛, contrasting with the 1-1.5 ㎛ size observed in specimen LO. Pore fraction, governed by oxygen concentration, is high in specimen HO, registering a value of 0.11%, whereas specimen LO exhibits a lower pore fraction (0.02%). Varied pore types in each specimen further underscore the role of oxygen concentration in shaping microstructural morphology. Despite these microstructural variations, the average hardness remains consistent at ~370 HV. This study emphasizes the pivotal role of oxygen content in influencing microstructural features, contributing to a comprehensive understanding of the intricate interplay between elemental composition and material properties.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.25 no.1
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• pp.72-87
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• 2021

Objectives This is the review on the Jeolgyeong which means diagnosis method of meridian and acupoints. Detecting method of meridian and acupoints under the disease condition using fingertips were more developed in Japan than in China and Korea. This study is the introduction to the Japanese style palpation method on meridian and acupoints. Methods Firstly the textbook 'Acupuncture medicine' published by the committee of Korean professors' association of acupuncture and moxibustion was analyzed. Especially the contents of the palpation method on meridian and acupoints were focused and summarized and secondly the book describing the palpation method on meridian and acupoints was selected, translated and summarized. Results Until now the knowledge on the acupoints reaction depending on the patient's status, the deficiency pattern and the excessive pattern was rarely described in China and Korea. On the contrary, 4 kinds of reactions in the deficiency pattern and 4 kinds of reactions in the excessive pattern were well described in Japanese literatures. Mild touching, mild pinching, rubbing, mild pressing and severe pressing were also described along the meridians. Except the bladder meridian Back Shu points, Yuan points, Luo points, Xi(cleft) points, Front Mu points were depicted as the same as those in China and Korea. For the bladder meridian lines, 4 lines were organized including 2 lines of Hua-Tuo-Jia-Ji-Xue and the middle line between 1st and 2nd bladder meridian line as well as 1st bladder meridian line and 2nd bladder meridian line. Conclusions Detecting meridians or acupoints and using them for diagnosis and treatment is a method used in China, Korea, and Japan. However, detailed descriptions of the method for detecting meridians through palpation are revealed in Japanese books. Palpation methods for diagnosing meridians using touching, pinching, rubbing, and pressing methods are expected to be standardized and systematically learned in Korea.

• Journal of Acupuncture Research
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• v.24 no.3
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• pp.187-196
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• 2007

Objectives : This study was designed to evaluate the effect of Moxa Pellet therapy on chronic low back pain. Methods: Subjects were voluntarily recruited by newspapers and internet. The Moxa Pellet therapy was performed for 4 weeks. Patients were randomized to three groups: Moxa Pellets, Control-l and Control-2 group. Moxa Pellets group administered with Moxa Pellets, Control-l group administered with moxa pellet-shaped moxa pellet without available components and Control-2 group administered with round bonded fabric that could not give pressing stimulation. Acupuncture points used in this study were $GV_3$, $BL_{23}$, $BL_{24}$, $BL_{25}$ and $BL_{22}$. The patient's symptoms were assessed before and after 4 weeks treatments by VAS, SF-MPQ and SF- 36. Results : The results are follows; 1. VAS score showed significant difference in Moxa Pellet group and Control-l group after treatment. 2. SF-MPQ score showed significant difference only in Moxa Pellet group. 3. Moxa Pellet group showed significant difference in PF, RE, MR, and BP of SF- 36 score after treatment; Control-l group showed no significant difference; Control-2 group showed significant difference in BP. There were no significant difference among the groups. Conclusions : This study suggests that Moxa Pellet therapy can be applicable to improve symptoms in the patients with chronic low back pain. Further studies on the Moxa Pellet therapy and other treatment in the patients with chronic low back pain is recommended.