• 대한수의학회지
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• 제42권3호
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• pp.411-418
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• 2002

단측성 외고정기구를 이용한 대퇴골 신연술의 합병증을 조사하기 위하여 30마리의 토끼를 대상으로 대퇴골 신연술을 실시하였다. 20마리의 토끼는 대퇴골 신연부의 가골이 완전 경화될 때까지 생존하였다. 10마리의 토끼는 대퇴골 신연 도중 합병증으로 인해 안락사 시켰다. 20마리의 토끼는 대퇴골 신연 비율에 따라 두 군으로 분류하였다: I군(대퇴골 길이의 10%를 신연한 군), II군(대퇴골 길이의 20%를 신연한 군). 두 군 사이에서 대퇴골 신연부위의 골경화 기간은 통계학적으로 유의적인 차이를 보이지 않았다(p=0.25). 두 군의 60%에서 골신연부위의 내반변형이 발생하였으며, I군에 비해 II군에서 보다 높은 내반각 변형을 관찰할 수 있었다. II군의 30%에서 대퇴골 내측관절융기에서 퇴행성 관절염 소견이 나타났다. 골신연을 중단했던 10마리의 토끼에서 핀 빠짐 5두, 골절 2두, 골수염 3두의 합병증이 나타났다.

• 마이크로전자및패키징학회지
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• 제26권4호
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• pp.63-68
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• 2019

온도 및 압축응력 변화에 따른 PIN-PMN-PT계 압전 단결정의 유전 특성과 압전 특성을 조사하였다. 단결정의 결정상은 110℃ 영역에서 강유전 rhombohedral 구조에서 tetragonal 구조로, 190℃ 영역에서 tetragonal 구조로부터 상유전 cubic 구조로 변화하였다. 전계 인가에 따른 분극 및 변위의 변화율로부터 압전상수와 비유전율을 계산하였으며, 이는 계측기로부터 측정된 값과 유사한 수준을 나타내었다. 샘플에 인가되는 압축응력이 증가할수록 압전상수 d₃₃과 비유전율값은 증가하는 경향성을 나타내었다. 측정 온도 5℃에서 샘플에 인가되는 압축응력이 60 MPa인 경우 d₃₃ 값이 4500 pC/N로 계산되었으며, 측정 온도 60℃인 경우, 샘플에 인가되는 압축응력이 40 MPa 일 때 비유전율 62000이 계산되었다. 압축응력이 높아질 때 압전상수와 비유전율 값이 상승한 것은 rhombohedral 상에서 orthorhombic 상으로의 전이에 기인한 것으로 판단된다.

• Tribology and Lubricants
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• 제19권3호
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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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• 제14권3호
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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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• 제11권1호
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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.

• 한국기계가공학회지
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• 제7권3호
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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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• 제16권1호
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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.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제3권1호
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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.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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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.

• 대한족부족관절학회지
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• 제9권2호
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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.