• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.300-306
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• 2005

This paper presents the methodology for measuring eccentricity of the machined cylindrical part using CCS(cylindrical capacitance spindle sensor) signal in the CNC turning process. We use capacitance type sensor to take full advantage of averaging effect by using large capacitance area to encompass the whole side of a sensor. The intentionally proposed initial eccentricity is applied to the experimental testpieces, and their resultant relationships between CCS orbits and eccentricities are investigated. As a result, the possibility as a automatic detection apparatus for the CNC lathe is considered based on the linearities of CCS signal and magnitude of eccentricity of machined cylindrical surfaces.

• Tribology and Lubricants
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• 제32권2호
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• pp.44-49
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• 2016

Diamond mechanical polishing (DMP) is a crucial process in a sapphire wafering process to improve flatness and achieve the target thickness by using free abrasives. In a DMP process, material removal rate (MRR) is a key factor to reduce process time and cost. Controlling mechanical parameters, such as velocity and pressure, can increase the MRR in a DMP process. However, there are limitations of using high velocities and pressures for achieving a high MRR owing to their side effects. In this paper, we present the lapping characteristics and improvement of MRR by using a fixed abrasive plate through an experimental study. The change in MRR as a function of velocity and pressure follows Preston's equation. The surface roughness of a wafer decreases as the plate velocity and pressure increases. We observe a sharp decrease in MRR over the lapping time at a high velocity and pressure in the velocity and pressure test. An analysis of surface roughness (Rq and Rpk) indicates that wear of abrasives decreases the MRR sharply. In order to investigate the effect of abrasive wear on the MRR, we utilize a cutting fluid and a rough wafer. The cutting fluid delays the wear of abrasives resulting in improvement of MRR drop. The rough wafer maintains the MRR at a stable rate by self-dressing.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.132-136
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• 1996

A Study is a experiment which is figure out to aptimum discharge cutting condition of the surfaceroughness, electric discharging speed and electro wear ratio with Ton Toff and V(voltage) as an input condition according to the current(Ip) in an electric spark machine ; 1)Electrode is utilized Cu(coper) and Graphite. 2)Work piece is used the material of carbon steel. The condition of experiment is; 1)Current is varied 0.7(A) to 50(A). 2)Pulse time(Ton) is varied 3($\mu$s) to 240($\mu$s) and also Toff is varied 7($\mu$s) to 20($\mu$s). 3)The time of electric discharging to work piece in each time is 30(min) to 60(min) 4)After the upper side of work piece was measured in radius (5${\mu}{\textrm}{m}$) of syulus analyzed the surface roughness to made the table and graph of Rmax by yielding data. 5)Electro wear ratio is; \circled1Coper was measured cx-machining and post machining but the electronic baiance. \circled2The ex-machining of graphite measured by it, the post-machining was found the data from volume specific gravity and analyzed to made its table and graph on ground the data 6)In order to keep the accuracy of voltage affected to the work piece was equipped with the A.V.R(Automatic Voltage Regulator). 7)The memory scope was sticked to the electric spark machine. 8)In order to preserve the precision of current, to get rid of the noise occured by internal resistance of electric spark machine and to force injecting for the discharge fluid, it made the fixed table for a work piece to minimize the work error by means of one's failure during the electric discharging According to above results, the surface roughness by the variation of electrodw and current was analyzed to compare KS(Korea Standards) It was decided the optimum condition of electric discharge cutting through analyzing the effect of electric discharge speed and electro wear ratio.

• 한국지반환경공학회 논문집
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• 제9권4호
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• pp.5-13
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• 2008

충전물이 암 절리면의 전단강도를 감소시키는 것과 유사하게 콘크리트와 주변 암반근입부 사이의 연약한 물질은 암반에 근입된 현장타설말뚝의 주면저항력을 감소시킨다. 이러한 현상은 콘크리트 타설 후에 암반 근입부 측벽에서 천공잔류물이나 스미어 또는 재성형 암반을 생성시키는 시공과정에서도 형성되게 된다. 콘크리트 말뚝과 주변 암반 사이의 접촉면의 특성은 시공법에 따라서 크게 영향을 받는다. 콘크리트 타설과정 또는 그 이후 형성되는 연약한 물질이 존재하거나 거칠기와 같은 콘크리트-암 접촉면의 특성은 말뚝의 주면부 거동에 큰 영향을 미친다. 본 연구에서는 유한차분법 코드를 기반으로 하는 FLAC 2D를 이용하여 스미어현상이 발생한 암반에 근입된 현장타설말뚝의 거동특성을 조사하기 위하여 변수분석을 실시하였다. 본 연구의 결과로서, 정적연직하중을 받는 암반에 근입된 현장타설말뚝의 극한주면저항력에 영향을 미치는 요소와 말뚝두부의 침하에 영향을 미치는 요소들을 확인할 수 있었다.

• 대한치과보철학회지
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• 제42권5호
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• pp.556-571
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• 2004

Statement of problem: Surface texture of the implant is one of the important factors of the implant success, especially in the immediate implant loading. Many methods of the surface treatment of implant have developed and introduced. Purpose : This study was to evaluate the effects of the Ca-P coating implant crystallized the hydroxyapatite on the surface by the removal torque test and the histomorphometric analysis in vivo. Material and methods: 135 screw type implants, 4.0mm in length and 3.75mm in diameter were used in this study. Implants were divided into 3 groups and treated in the different mothods. Group I was not treated, Group II was treated in the SLA method, and Group III was treated in the Ca-P coating with the anodizing method and the hydroxyapatite was crystallized on the surface with the hydrothermal treatment. Firstly, the surface roughness of each group was measured, 45 rabbits were used in this experiment. Two implants were inserted on right tibial metaphysis and one implant was inserted on left side with the alternating order. After the healing periods of 3, 5, and 12 weeks, the rabbits were sacrificed to evaluate the osseointergration by the removal torque test and the histomorphometric analysis. Results : 1. In the analysis for the surface roughness, Group II showed the highest roughness. And Group III showed higher secondly. There was a significant difference one another statistically 2. In the removal torque test, Group III and II were significantly higher than Group I. There was no statistical difference between Group III and Group II. 3. For all Groups, the removal torque values at 12th week were significantly higher than at 3rd and 5th week. 4. In histomorphometric analysis, the bone implant contact rates of Group III and II were higher than that of Group I at 3rd and 5th week. There was a significant difference at 5th week. 5. In histomorphometric analysis, the bone implant contact rate of Group III and II increased from 3rd week to 5th week, but decreased at 12th week. In Group I, the contact rate at 12th week was significantly higher than at 3rd week and 5th week.

• 한국강구조학회 논문집
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• 제23권2호
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• pp.199-210
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• 2011

사장교의 케이블은 타 부재에 비해 단면적이 매우 작고 고응력 상태이므로 진동에 매우 민감한 부재이다. 따라서 사장교 케이블의 충격계수는 실제 차량의 주행으로 발생하는 동적 효과를 반영하여 평가하는 것이 합리적이다. 이에 본 연구에서는 차량 중량, 케이블 모델, 노면조도, 차량속도 및 차량간격의 설계변수를 고려하여 중앙경간 230m 및 540m의 강합성 사장교를 대상으로 차량 이동하중 해석을 수행하여 케이블의 충격계수를 평가하고, 현재 실무에서 사용되고 있는 영향선을 이용한 방법과 비교하였다. 본 연구에 사용된 노면조도는 ISO 8608 규정에 근거하여 랜덤 생성하였으며, 생성 회수에 따른 케이블 충격계수의 수렴 추이를 분석함으로써 결과의 신뢰도를 확보하였다. 또한, 차량모델은 9-자유도를 갖는 트랙터-트레일러 형식의 트럭 모델을 적용하였으며 차량의 운동방정식은 Lagrange운동방정식으로부터 유도하였다. 해석 대상 교량은 3차원 유한요소모델로 구축하였으며 보강형과 주탑은 보요소, 케이블은 등가탄성계수를 갖는 트러스요소를 사용하였다. 이동하중으로 인한 교량-차량 상호작용 해석에는 직접적분법을 사용하였으며, 교량의 변위 오차율이 허용 범위 내에 수렴될 때까지 반복 해석을 수행하였다. 그 결과, 실제 차량의 주행으로 발생하는 동적 효과를 고려하지 못하는 영향선 기법은 차량 이동하중 해석에 비해 측경간 단부 케이블의 충격계수를 과소평가할 수 있는 것으로 나타났다.

• Corrosion Science and Technology
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• 제14권1호
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• pp.19-24
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• 2015

지금까지 마그네타이트 전극의 제조 방법과 전기화학적 특성에 대해 살펴보았다. 마그네타이트 전극을 제조하는 방법은 프레스법, 페이스트법, 전기도금법 등이 있으며, 이들의 전기화학 특성은 다음과 같이 정리할 수 있다. 1. Cycle voltammetry 실험을 통하여 애노딕, 캐소딕 분극 방향으로 각각 2개의 peak가 관찰되고, 이것은 $Fe_3O_4$가 $Fe(OH)_2$, FeO 등의 중간 산화물 형태를 거쳐 $Fe^{2+}$로 용해되는 반응들이다. 2. 산성 및 중성 용액에서는 마그네타이트의 환원적 용해가, 염기성 용액에서는 헤마타이트로의 산화 반응이 나타난다. 3. 전기화학 실험 결과와 마그네타이트 용해도를 관련시키기 위해서는 마그네타이트 용해가 일어나는 전위에서 실험 후, 용액에서 $Fe^{2+}$, $Fe^{3+}$ 이온들에 대한 분석이 필요하다.

• 치과방사선
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• 제25권2호
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• pp.409-422
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• 1995

The purpose of this study was to investigate the effects of radiation on the formation of rat molar enamel at the developmental stage. The experimental animals were divided into five groups and were irradiated single dose of 396cGy ; 1 st group on 14th day of gestation, 2nd group on 19th day of gestation, 3rd group on 3 days after birth, 4th group on 8 days after birth, 5th group on 28 days after birth. The control and 1, 2, 3, and 4th experimental groups were sacrificed on 2, 4, and 6 weeks and the 5th groups were sacrificed on 1 day and 2 weeks after irradiation. Distal 1/2 and occlusal 1/3 enamel surface of lingual side of lingual cusp, and fractured surface of lingual side of lingual cusp in a longitudinal direction of the mandibular first molar were examined using scanning electron microscope. The following results were obtained. 1. The roughness of enamel surface and enamel hypoplasia were increased in a sequence of 4th, 1st, 2nd, and 3rd experimental group, and the enamel cracks were increased in the 1st and 2nd experimental group. 2. The pattern of enamel hypoplasia had a network form on the 1st and 2nd experimental group, and appeared a linear shape on the 3rd experimental group, and then the crator-like enamel defects were observed in all experimental groups (especially 1st and 2nd experimental group) except 5th. 3. Dentinoenamel junction showed the clear-cut and straight appearance except 5th experimental group. 4. There was no significant difference between 5th experimental and control group.

• Restorative Dentistry and Endodontics
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• 제19권1호
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• pp.64-72
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• 1994

Zinc Phosphate Cement hand been used for about more than 100 years in luting of cast gold inlay. But many scientists had been trying to develop the new form of luting agent because the ZPC hand shown the lack of adhesiveness on the tooth structure and the toxicity to the pulp tissue. Recently many researches about the surface treatment of the cast body are being done to increase the adhesion of cement to it. The conventional Class I gold inlays were fabricated in the 20 permanent molars. After the internal surface of the cast body was sandblasted with $Al_2O_3$ particles and was tin-plated, the inlays were cemented with adhesive cement [G I cement and resin cement(Super-Bond & $Panavia_{EX}$)] and the evaluation on the adhesion pattern, adhesive strength and the fracture pattern of the adhesive cast gold inlay was compared to that of the cast gold inlay cemented conventionally with ZPC. The results were as follows : 1. The surface roughness of the cast body was increased significantly after sandblasting with the $Al_2O_3$ particles and the tin oxide layer, which was consisted of round particles, came into being. 2. The bond strength was in the order of Super-Bond, ZPC, Fuji I, $Panavia_{EX}$ group. The group cemented with Super-Bond showed statistically greater strength than the other groups(p<0.05). 3. The group cemented with ZPC was fallen apart by principal adhesion failure and that with Fuji I was by complete adhesion failure. But the group with Super-Bond showed pricncipal cohesive failure pattern and in the group with $Panavia_{EX}$, complete cohesive fracture pattern was shown and small protion of tooth structure was fractured out with cast body and the fractured surface showed the figure just as the enamel prism. 4. Various gaps were shown at the pulpal side regardless of little gap at the side walls of the cavity in all groups. Only the Super-Bond was attached to the tooth structure and the other cements were detached from both the tooth and the cast body.

• 한국표면공학회지
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• 제47권6호
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• pp.303-310
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• 2014

In this study, the average in-situ stress in metallic thin film was measured during deposition of the Cu thin films on the Si(111) wafer and then the phenomenon of stress shift by the interruption of deposition was measured using Cu thin films. We have observed the stress shift in accordance with changing amount of atom's movement between the surface and grain boundary through altering the grain size of the Cu thin film with variety of parameters. The grain size is known to be affected on the deposition rate, film thickness and deposition temperature. As a experimental results, the these parameters was not adequate to explain stress shift because these parameters affect directly on the amount of atom's movement between the surface and grain boundary as well as the grain size. Thus, we have observed the stress shift toward tensile side in accordance with the grain size changing through the interlayer deposition. From an experiment with inserting interlayer before deposit Cu, in thin film which has big grain size with high roughness, amount of stress movement is higher along direction of tensile stress after deposition that means, after deposition process, driving force of atoms moving in grain boundary and on the surface of the film is relatively higher than before.