• Tribology and Lubricants
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• v.19 no.3
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• pp.151-158
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• 2003

In metal cutting at the tool-chip interface, friction generates considerable amount of heat. Thus, the knowledge of wear properties of cutting tool material in high temperature has been as one of important factors in need of clarification. The authors presented the wear properties of 5%Co-5%V-1%Nb high speed steel, fabricated by powder metallurgy, in room temperature in previous articles. The objective of this paper is to clarify the effects of temperature on its wear properties. Wear tests in sliding conditions under various temperatures have been conducted using the pin-on-disc type wear test machine. The results indicate that the wear properties of 5%Co-5%V-1%Nb high speed steel in high temperature as well as in room temperature are excellent. It may be deduced that the oxide layer formed on worn surface at high temperature is stable enough to prevent wear due to the high temperature strength of its matrix.

• Design & Manufacturing
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• v.14 no.3
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• pp.17-22
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• 2020

As devices such as smartphones, tablet PC, and wearable devices have been miniaturized, the connectors that go into the devices are also designed to be very small. The connector combines the plug and the receptacle to transfer electricity. As devices are miniaturized, the contact shape is formed by partially thinning the thickness of the raw material of the terminal in order to lower the coupling height of the plug and receptacle. The product used in this study is a receptacle terminal used for 0.4mm pitch board to board connector among fine pitch connectors. When the material thickness is reduced by forging the receptacle terminal, the width change of the pin is checked. To reduce the thickness of the material by forging, pre-notching is applied in the first step, forging in the second step, and notching in the third step. After forming the width dimension of the pin to 0.28 mm in the pre-notching process, in the forging process, the material thickness 0.08 mm and 0.02 mm (25%) were forged and the thickness was changed to 0.06 mm and the width change amount of the pin was measured. The facility produced 10,000 pieces at 400 SPM using a Yamada Dobby (MXM-40L) press, and thirty pins were measured and the average value was shown. After forging by using C5210-H (HP) and NKT322-EH, which are frequently used in connectors, analyze the amount of change in each material. The effect of punching oil on forging is investigated by appling FM-200M, which is highly viscous, and FL-212, fast drying oil. This study aims to minimize mold modification by predicting the amount of material change after forging.

• Toxicological Research
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• v.11 no.1
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• pp.69-75
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• 1995

The present study was carried out to establish several spermatotoxicity test methods. For this purpose we investigated following parameters in the fertility study of DA-125, a new anticancer agent, in rats: testicular spermatid counts, epididymal sperm counts, daily sperm production rate, sperm morphology, and serum testosterone concentration. Motility and velocity of sperms were also measured using non-treated rats. At 0.3 mg DA-125/kg, spermatids per 1g testis and daily sperm production rate per 1g testis were significantly decreased, when compared with those of control group. Several types of abnormal sperms, such as no head, pin head, double head, hook at wrong angle, no tail, and small sperm, were found in both treated and control groups at a low frequency. Serum testosterone concentration at 0.3 mg DA-125/kg was close to the control value. Sperm motility and velocity measured with non-treated rats were in a good agreement with the results of other investigators. In our study established spermatotoxicity test methods can be used as a tool not only for the close examination of the cause of drug- or chemical-induced infertility, but also for the effective evaluation of reproductive toxicity.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.3
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• pp.110-114
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• 2008

In this study, to examine the friction coefficient and wear amount of dental prosthesis, pin-on-disk type wear test were at room temperature. Vickers hardness and fracture toughness measurement of dental materials were preformed. Microscopic observations on worn surfaces of specimens were conducted by SEM. The friction coefficient of dental material was investigated according to weight and slinging velocity. dental material have investigated composed to nature teeth.

• Journal of Chest Surgery
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• v.16 no.1
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• pp.121-126
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• 1983

8 cases of the esophageal perforations were treated at the department of thoracic surgery, Chungnam National University Hospital during the period from July, 1980 to Dec., 1982. The causes of the perforation were various; swallowed a piece of glass, stocking pin, coiled wire, compressed air blow, strenuous vomiting, dog bite, tiller accident, and endoscopic procedure. The perforation sites were cervical esophagus in 3 cases, upper thoracic in 2 cases and lower thoracic in remains. We have performed following surgical procedure; Incision and drainage for cervical abscess, closed thoracostomy, thoracotomy and debridement, esophagoscopy and gastrostomy. Two cases were died. The causes of death were massive bleeding and sepsis.

• Research in Mathematical Education
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• v.3 no.1
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• pp.23-34
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• 1999

This paper presents a summary of the Scientific Research Training (SRT) in Liaocheng Teachers University, which is a representative of normal universities and teachers' colleges in China. There is a survey on the situation of SRT in China systematically and historically. Tentative ideas about SRT in future are targeted at the teachers and heads of departments in China.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.653-654
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• 2006

A Pre-emphasis transmitter for DRAM bus system has achieved 3.2Gbps/pin operation at 1.8V supply voltage with 0.18um CMOS process. The transmitter has 800MHz PLL to generate 4 phase clocks. The 4 phase clocks are used for input clock of PRBS and multiplexing. One tap pre-emphasis is used to reduce inter symbol interference (ISI) caused by channel low pass effects. The analog calibration makes the optimized driver impedance independent with the PVT variation.

• Journal of Korean Foot and Ankle Society
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• v.9 no.2
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• pp.140-145
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• 2005

Purpose: To analyze the outcome of metatarsal lengthening of first brachymetatarsia by callotasis using an external fixator. Materials and Methods: Between January 1998 and February 2004, 10 patients (17 cases) were reviewed. The mean age at operation was 17.3 years. Seven patients had bilateral first brachymetatarsia and eight patients had combined 4th brachymetatarsia. The operations were performed with a monoexternal fixator, and distraction was started at a rate of 0.75 mm/day after 7 days. The radiographic results were evaluated by lengthening amount and percentage, fixation time, and healing index. Complications and AOFAS score were evaluated. Results: The average lengthening amount was 17.7 mm and the average lengthening percentage was 43.4%. The external fixation time was 107 days and average healing index was 69.8 days/cm. The evaluation according to AOFAS score was excellent in 12 cases and good in 5 cases. Complications were 4 cases of hallux valgus, 4 of metatarsophalangeal joint stiffness, 3 of medial angular deformity, 3 of pes cavus, 2 of pin breakage, 2 of pin site infection, and 1 of skin hyperpigmentation. Conclusion: Callotasis for 1st brachymetatarsia is a very useful treatment method with high patient satisfaction, excellent healing rate and early ambulation without bone graft. Nevertheless, great care must be taken to minimize the various possible complications.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.2
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• pp.277-289
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• 1996

The purpose of this study was to compare the amount of the vertical pin opening of dentures processed by the conventional compression method & the injection-processing method. The articulating ribbon and T-Scan system were used to determine the changes in tooth contacts and the correlation between the changes in tooth contacts and the amount of the vertical pin opening after processing was analyzed statistically. The obtained results were as follows. 1. The amounts of the vertical pin opening were 0.75mm, 0.31mm for conventional compression method and injection-pressing method, respectively. The difference between the two methods was highly significant on the basis of t test statistics(p<0.05). 2. The total number of contact points recorded by articulating ribbon after processing was decreased to 48%, 72%, of that before processing for conventional compression method and injection-pressing method, by T-Scan system, 39%, 53%, respectively. 3. The mean values for the number of contacts points per tooth recorded by articulating ribbon after processing were 1.6 for the second molar, 2.2 for the first moalr, 0.4 for the second premolar, 0.6 for the first premolar in conventional compression method, and 2, 3.2, 1.2, 0.8 in injection-pressing method. 4. The correlation between the reduction of contact points and the amount of the pin opening after processing was not significant. 5. The mean values for the number of contact points per tooth recorded by T-Scan system after processing were 1.25, 1.4, 0.7, and 0.55 at the second molar, the first molar, the second premolar, and the first premolar in conventional compression method, and 1.45, 2.1, 1.0, 0.75 in injection method, respectively. 6. The correlation between the number of contact points by using articulating ribbon and T-Scan system after processing was not significant in both methods.

• Journal of the Korean Wood Science and Technology
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• v.36 no.4
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• pp.93-101
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• 2008

Bearing strength test was investigated to determine the bearing properties of domestic larix glulam according to the load direction (in parallel to grain and in perpendicular to grain), the fastener (bolt and drift-pin), and the direction of laminae. The specimen was 5 ply glulam. The diameters of fastener are 12, 16 and 20 mm. The results were as follows. 1) In according to the diameter of bolt and drift-pin, the average of maximum bearing strength in parallel to grain loading was similar to that in perpendicular to grain loading. The average of maximum bearing strength was 1.50~2.31 times higher in parallel to grain loading than in perpendicular to grain loading. The average of maximum bearing strength in parallel to grain loading was lowered by 20% with increasing the diameter from 16 mm to 20 mm, but that in perpendicular to grain loading didn't show a clear tendency. 2) The average of bearing stiffness in parallel to grain loading was the highest at 16 mm in diameter. The average of bearing stiffness is similar to the shearing stiffness in drift-pin connection with increasing diameter. 3) In parallel to grain loading, the failure mode of specimens was the splitting along the grain in decreasing diameter. The failure mode in perpendicular to grain loading was the splitting along the grain. In this case, split occured more in specimens using bolt than in those using drift-pin. 4) The 5% offset yield strength in parallel to grain loading was similar to the predicted bearing strength of KBCS, NDS. In perpendicular to grain loading, the NDS's equation can be applied to predict the bearing strength.