성장호르몬 치료 중 발생한 대퇴골두골단분리증 1예

Slipped capital femoral epiphysis (SCFE) is the most common orthopedic hip disorder occuring in adolescence. In this condition, the femoral head (epiphysis) displaces, or slips on the femoral neck through the region of the growth plate. This condition can occur only before the epiphyseal plate closes. The exact etiology is unknown, although it has been associated with obesity, mechanical abnormalities, physeal abnormalities, endocrine disturbances (hypothyroidism, growth hormone deficiency, hypogonadism). Interestingly, SCFE was observed in growth hormone deficiency and in patients treated with growth hormone. We report a case of an adolescent male with glycogen storage disease Ia and growth hormone deficiency who developed SCFE during treatment with recombinant human growth hormone. A 17-year-old male was admitted for pain of left hip which was exacerbated by walking 15 days ago. He was diagnosed glycogen storage disease Ia and growh hormone deficiency 2 years ago and treated growth hormone therapy with recombinant human growth hormone at the dose of 2 unit/day. The diagnosis of SCFE was confirmed radiologically. From the time of admission, he received skin traction on the left hip joint and stopped to inject growth hormone and treated surgically with internal fixation of the epiphysis with use of 3-cannulated screw. The patient is followed at out-patient clinic without postoperative complication

Relationship between Children's Self-perceived Communication with Teachers and their Self-efficacy

본 연구는 교사-아동간의 의사소통 수준 및 아동의 자기효능감 향상을 위한 교육적 기초 자료를 제공하기 위한 목적으로 시도되었다. 이러한 목적을 달성하기 위하여 초등학생이 지각한 교사-아동간의 의사소통과 아동의 자기효능감간의 관계를 규명하고자 하였다. 본 연구에서 설정한 연구문제는 다음과 같다. 아동이 지각한 교사-아동간의 의사소통과 아동의 자기효능감간에는 어떠한 관련성이 있는가? 본 연구의 연구대상은 서울시 소재 4개 초등학교 4학년, 6학년 학생 417명(남학생: 217명, 여학생: 200명)이었다. 본 연구에서 사용한 설문지는 Carkhuff(1969)의 척도를 기초로 하여 신현오(1991)가 번안한 교사-아동간 의사소통 검사지를 수정한 것과 차정은(1997)이 개발한 일반적 자기효능감 검사를 재구성한 것이다. 교사-아동간 의사소통 검사는 7개의 하위영역(공감성, 존중성, 진실성, 구체성 자기개방, 즉시성, 직면)으로 구성되어 있고, 자기효능감 검사는 3개의 하위영역(자기조절, 자신감, 과제난이도 선호)으로 구성되어 있다. 이들 검사의 Cronbach‘s a는 각각 .87와 .89이었다. 수집된 자료에 대한 분석은 SPSS win 12.0에 의한 정준상관분석이 수행되었다. 분석 결과 본 연구의 주요한 결과는 다음과 같다. 아동이 지각한 교사-아동간의 의사소통과 아동의 자기효능감간의 관계를 정준상관분석으로 살펴본 결과, 즉시성, 직면, 진실성, 구체성, 존중성에서 긍정적으로 지각한 학생일수록 과제난이도 선호, 자기조절, 자신감 점수가 높았다. 따라서 교사가 아동과 대화할 때, 지금-여기에서, 아동의 행동과 언어 사이의 불일치를 지적해주고, 진실 되게, 추상적인 말 대신 구체적인 용어를 사용하고, 학생의 능력을 믿으며 존중해준다면, 아동은 어려운 과제에 도전적이게 되고, 자기조절 능력이 향상되며, 자신감이 높아진다는 것을 알 수 있다. 이러한 결과를 통해 아동의 바람직한 내적 변화를 위한 교육이 되기 위해서는 교사의 긍정적인 의사소통 기술이 필요하다는 것을 알 수 있다. 따라서 교사 양성기관에서는 교사의 의사소통 기술 훈련을 위한 교육과정을 마련해야 하며, 교육 현장에서는 지속적인 교사 연수를 통해 교사의 의사소통 기술을 향상시킬 수 있도록 해야 할 것이다. 더 나아가 아동과 많은 시간을 보내고 있는 부모를 대상으로 한 의사소통 기술 향상 프로그램 교육도 활성화되어야 할 것이다.;The purpose of this study was to help improve school children's communication with teachers and their self-efficacy by examining the relationship of their self-perceived communication with teachers to their self-efficacy. A following research question was posed: What is the relationship between children's self-perceived communication with teachers and their self-efficacy? The subjects in this study were 417 fourth and sixth graders in four different elementary schools located in Seoul, who included 217 boys and 200 girls. The questionnaires used in the study were Sin Hyeon-oh(1991)'s adapted version of Carkhuff(1969)'s Teacher-Child communication Scale and Cha Jeong-eun(1997)'s General Self-Efficacy Inventory, which were modified and reconstructed respectively before they were used. The former consisted of seven segments that involved empathy, respect, genuineness, concreteness, self-disclosure, immediacy and confrontation, and the latter was constituted by three segments, including self-control, confidence and preference for task difficulty. The Cronbach's alpha coefficients of the two were respectively .87 and .89. For data handling, canonical correlation analysis was conducted by using SPSS Win 12.0 program. The major findings of the study were as follows: When canonical correlation analysis was utilized to look for connections between the children's perception of their own communication with teachers and their self-efficacy, the students who took a more positive view of their communication with teachers in terms of immediacy, confrontation, genuineness, concreteness and respect scored better in preference for task difficulty, self-control and confidence. So it's found that children could challenge tough tasks, have themselves in control and build up confidence if their teachers talk here and now, if they point out inconsistency of their speech and action on the spot, if they talk in a trustworthy manner, if they talk in a concrete way, not an abstract one, and if they believe in them and respect them. The findings of the study suggested that educating children to make a good inner change requires positive communication skills on the side of teachers. Colleges of education should offer communication-training courses as part of curriculum, and the educational authorities should provide sustained training opportunities for teachers to foster their communication skills. At the same time, a wide variety of communication programs geared toward parents who spend many time with children should be conducted as well.Ⅰ. 서론 = 1 A. 연구의 목적 및 필요성 = 1 B. 연구의 문제 = 3 Ⅱ. 이론적 배경 = 4 A. 의사소통 = 4 B. 자기효능감 = 11 C. 의사소통과 자기효능감 = 16 Ⅲ. 연구방법 = 20 A. 연구대상 및 자료수집 = 20 B. 측정도구 = 20 C. 자료분석 = 22 Ⅳ. 연구 결과 = 23 A. 아동이 지각한 교사-아동간의 의사소통과 아동의 자기효능감간의 정준상관관계 = 23 Ⅴ. 논의 및 결론 = 26 참고문헌 = 29 부록 1 의사소통 척도 = 32 ABSTRACT = 4

Colorimetric detection of DCP using transparent cellulose nanofilm sensor in vapor phase

Transparent cellulose nanofiber films (CNFs) were prepared for colorimetric detection of diethyl chlorophosphate (DCP), a nerve agent mimic in the vapor phase. The nanofibrillaion of cellulose was efficiently achieved by aqueous collision counter (ACC) system, followed by succinylation. Horizontal centrifugal casting (HCC) process allows the fabrication of succinylated cellulose nanofiberfilm (SCNF film) with uniform film thickness. DCP receptor, (E)-4-((E)-(4-((2-hydroxyethyl)(methyl)amino)phenyl)diazenyl)benzaldehyde oxime (HEMBAO), was anchored on the surface of SCNF film, leading to the target probe, hereafter referred to as SCNF1 film. SCNF1 film exhibits the selective detection behaviors toward DCP in the vapor phase. Upon exposure to DCP vapor, the oxime groups of SCNF1 film reacted with DCP, which accompanied by a color change from yellow to purple due to enhancement of the intramolecular charge transfer (ICT) effect. Most importantly, the transparency of the film was retained during the entire detection process, enabling it to identify objects behind the film during DCP detection. This property could be generally applicable to the detection system where the color change caused by detection should not interfere with the transparency of the film. The film sensor is biodegradable, allowing it to be disposable after use.Maste

고등학교 영어 학습자들의 읽기 학습책략에 관한 연구

학위논문(석사)--서울대학교 대학원 :외국어교육과 영어교육전공,1996.Maste

The Chemical Vapor Deposition of TiN on Cemented Tungsten Carbide Cutting Tools(PartII)

WC-TiC-TaC-Co系의 超硬合金위에 TiN蒸着時 TiCl₄에서 TiN으로되는 理論的인 Yield( ?? )를 溫度 1,000℃K~1,500℃K範圍에서 計算하였으며 또한 TiCl₄分壓과 Substrate의 Co含量이 Deposition rate에 미치는 影響을 調査하였다. 이때 얻어진 結果는 Coating두께가 增加함에 따라 Coated Tool의 抗折力은 減少하며, Tool의 Co含量 增加에 따라 顯著하게 純化됨을 알 수 있었다. Coated Tool의 Surface Roughness는 蒸着溫度에 依해 支配를 받으며 TiN Coating의 微小硬度는 1,700~2,000kg/mm²값을 갖는다. TiN Coating을 하므로서 磨耗抵抗은 현저하게 增加하여 uncoated tool에 比해 Crater Wear resistance는 20倍, Flank Wear resistance는 6倍 增加함을 確認하였다.In developing a TiN Coating for cobalt bonded WC-TiC-TaC, theoretical calculations of percent conversion of TiDl₄as a function of TiCl₄partial pressure were carried out in the temperature range of 1,000°K-1,500°K. In addition, the effect of the TiCl₄partial pressure and cobalt content of the substrate on the deposition rate were investigated. The transverse rupture strength is noticeably reduced by the coating, the extent of this decrease depending thickness. Concerning the deposition of the smooth coating layers, it was oberved that surface roughness is influenced by deposition temperature. The TiN coating had hardness balues of 1,700-2,000kg/mm². The wear resistance of TiN layers is tested in turning steel and it was observed that Crater resistance is 20 times, Flank resistance is 6 times better than uncoated tools.In developing a TiN Coating for cobalt bonded WC-TiC-TaC, theoretical calculations of percent conversion of TiDl₄as a function of TiCl₄partial pressure were carried out in the temperature range of 1,000°K-1,500°K. In addition, the effect of the TiCl₄partial pressure and cobalt content of the substrate on the deposition rate were investigated. The transverse rupture strength is noticeably reduced by the coating, the extent of this decrease depending thickness. Concerning the deposition of the smooth coating layers, it was oberved that surface roughness is influenced by deposition temperature. The TiN coating had hardness balues of 1,700-2,000kg/mm². The wear resistance of TiN layers is tested in turning steel and it was observed that Crater resistance is 20 times, Flank resistance is 6 times better than uncoated tools

A Study on the Hardness and Toughness of Cemented Carbides as a function of Microstructural Parameters

본 연구에서는 초경합금의 변형기구를 이해하기 위하여 초경합금의 미세조직 인자에 따른 경도와 인성을 조사하였다. 특히 초경합금의 인성을 측정하기 위해 항절력시험, 충격시험, Palmqvist시험, 평면변형파괴 인성시험을 수행한 결과 다음과 같은 결론을 얻었다. 1) 초경합금의 비커스 경도와 미세조직인자와 관계는 Hall-Petch관계식이 성립하며 Hall-Petch상수 H?와 K₁는 각각 425Kg/mm², 559Kg/mm³?²로 주어지며 초경합금의 강도지배인자는 True MFP임을 확인하였다. 2) 항절력시험 결과 항절력은 True MFP가 0.62μm 일때 최대값을 갖는다. 3) 초경합금의 충격강도는 주로 초경합금의 취약한 상의 양에 의존되며 충격강도는 Cobalt함량이 증가함에 따라 증가하나 초경합금의 입도에 따른 영향은 거의 없다. 4) Palmqvist시험으로 얻어진 결과는 10?/W=AH-B이며 여기서 W는 균열저항계수, H는 Vickers경도이며 상수 A, B는 각각 0.0216, 20.93이었다. 이 관계식은 초경합금의 연구와 품질관리에 유용한 식이 될 수 있다. 5) 방전가공기에 의해 Notch를 부여한 SENB시편을 3점 굽힘시험에 의해 K?값을 측정한 결과 평면변형파괴인성은 미세조직인자 중 True MFP와 WC입자의 분산정도에 의존되며 초경합금의 경도 증가에 따라 직선적으로 감소한다. 선형탄성파괴역학에 근거로부터 계산된 임계변형에너지 해방율, G?는 True MFP의 증가와 더불어 직선적으로 증가한다.In the present investigation, to understand the deformation mechanism of cemented tungsten carbides, the variation of the hardness and toughness of cemented tungsten carbide was studied as a function of its microstructural parameters. Particularly, in order to evaluate the toughness of cemented tungsten carbides, transverse rupture test, impact test, Palmqvist test, plane strain fracture toughness test were used. Results obtained are as follows. 1) The relation of the Vickers indentation hardness of cemented carbide to its microstructural parameters can be presented by the Hall-Petch type equation. The value of Hall-Petch constant H? and K? are give as 425Kg/mm? and 559Kg/mm?, respectively. The true MFP of cobalt layers is proposed as the strength controlling microstructural parameter. 2) In transverse rupture test, it has been shown that TRS reaches a maximum for the critical value of true MFP (0.62μm). 3) Impact strength is a function, mainly, of the amount of the brittle phase present in the WC-CO alloys. It continues to increase with the percentage of cobalt, but the effect of grain size is relatively small. 4) It is shown experimentally that the parameters measured by the Palmqvist test crack resistance parameter, W and the hardness, H, are related by the following expression 10?/W=AH-B. The values of constant A and B are given as 0.0216 and 20.93, respectively. This method is very useful for daily measurement of toughness, for example in studying materials and in quality control of products. 5) The fracture toughness values (K?) of cemented carbides depends on the microstructural parameter, particularly the true MFP of cobalt binder and degree of separation of WC grains. The fracture toughness decreases almost linearly with the hardness of cemented carbides. The critical strain energy release rate, G? calculated from the linear elastic fracture mechanics relationships also increases linearly with the true MFP.In the present investigation, to understand the deformation mechanism of cemented tungsten carbides, the variation of the hardness and toughness of cemented tungsten carbide was studied as a function of its microstructural parameters. Particularly, in order to evaluate the toughness of cemented tungsten carbides, transverse rupture test, impact test, Palmqvist test, plane strain fracture toughness test were used. Results obtained are as follows. 1) The relation of the Vickers indentation hardness of cemented carbide to its microstructural parameters can be presented by the Hall-Petch type equation. The value of Hall-Petch constant H? and K? are give as 425Kg/mm? and 559Kg/mm?, respectively. The true MFP of cobalt layers is proposed as the strength controlling microstructural parameter. 2) In transverse rupture test, it has been shown that TRS reaches a maximum for the critical value of true MFP (0.62μm). 3) Impact strength is a function, mainly, of the amount of the brittle phase present in the WC-CO alloys. It continues to increase with the percentage of cobalt, but the effect of grain size is relatively small. 4) It is shown experimentally that the parameters measured by the Palmqvist test crack resistance parameter, W and the hardness, H, are related by the following expression 10?/W=AH-B. The values of constant A and B are given as 0.0216 and 20.93, respectively. This method is very useful for daily measurement of toughness, for example in studying materials and in quality control of products. 5) The fracture toughness values (K?) of cemented carbides depends on the microstructural parameter, particularly the true MFP of cobalt binder and degree of separation of WC grains. The fracture toughness decreases almost linearly with the hardness of cemented carbides. The critical strain energy release rate, G? calculated from the linear elastic fracture mechanics relationships also increases linearly with the true MFP

베체트병 병인에서 Vitamin D가 단핵구 toll-like receptor 발현에 미치는 영향

PURPOSE: Behcet’s disease (BD) is a chronic, relapsing, systemic vasculitis of unknown etiology. Although the exact mechanisms of the increased inflammatory response is not yet clear, infectious agents and immunological cross-reaction with the heat-shock proteins (HSP) are considered to play roles in the pathogenesis. Toll-like receptors (TLRs) are involved in the initiation of innate immune response in several immune mediated inflammatory disease including BD by sensing the various microorganisms and triggering the signalling pathways, causing release of cytokines. Recent studies have noticed the immunomodulatory effect of vitamin D3 through down-regulation of TLR expression in human monocytes. To understand the role of vitamin D affecting innate immunity in BD, we focused on the association between the serum vitamin D concentration and the TLR expression in BD. MATERIALS AND METHODS: Serum 25-hydroxyvitamin D levels were measured in the patients with BD, psoriasis and healthy controls. The expression of CD16, TLR 2 and TLR 4 on blood monocytes was detected by flow cytometric analysis and semiquantitative RT-PCR among those groups. Then we correlated the values of serum 25-hydroxyvitamin D levels with the expression of TLRs and the clinical indicators of disease severity (ESR, CRP) among patients and control groups. Then, to assess the influence of Vitamin D on expression and function of TLRs, human monocytes were treated with increasing concentrations of 1,25(OH)2D3 in vitro . RESULTS: We found a trend toward lower 25-hydroxyvitamin D levels in active BD patients compared to controls. The monocytes of active BD patients showed higher expression of TLR2, TLR4 with increased proportion of CD16+ cells compared to the control groups. Interestingly the 25-hydroxyvitamin D levels were inversely correlated with the expression of TLR2, TLR4 and clinical indicators. In vitro study, 1,25(OH)2D3 suppressed the expression of TLR2, TLR4 protein and mRNA in human monocytes in a dose-dependent manner. TNF-α synthesis upon LPS, LTA and HSP60 stimulation was also decreased in 1,25(OH)2D3 treated monocytes in concordance with TLR2, TLR4 down-regulation. And the marked increase of TNF-α response to TLR2, TLR4 ligands was found in active BD monocytes when compared to normal, which was correlated with the higher TLR2, TLR4 expression. CONCLUSION: We found lower serum 25(OH)D levels among active BD patients compared to controls. These results suggest vitamin D deficiency as a possible risk factor for active BD. And treatment of vitamin D deficiency will have a positive impact on immune health. BD patients are known to be rather susceptible to infectious agents which are recognized by TLRs, and HSP60 induced immune-activation is considered as an endogenous “danger signal” in the pathogenesis of BD. Our results could strengthen the notion about immunomodulatory effects of vitamin D to innate immunity-mediated inflammation in BD through down-regulation of TLR2, TLR4 on monocytes.연구 목적: 베체트병은 점막 및 피부, 눈, 심장, 혈관, 신장, 위장 그리고 신경이 침범될 수 있는 임상적 특징을 가지는 만성, 재발성의 전신 질환이다. 현재까지 베체트병에서 보이는 지속적인 염증 반응의 정확한 원인 기전은 밝혀져 있지 않으나 다양한 감염원과 체내의 열 충격 단백 (heat shock protein) 과의 면역 교차 반응이 발병에 중요한 역할을 담당할 것으로 보여진다. Toll-like receptor (TLR)는 박테리아, 바이러스 등의 외부 감염원의 pathogen-associated molecular pattern 을 빠르게 인지하여 체내에서 자연 면역 (innate immunity) 반응을 유도하는 세포막 유형 인지 수용체로, TLR에 의해 유도되는 proinflammatory cytokine 들의 과발현은 자가 면역 질환이나 만성 염증성 질환의 발병, 유지에 영향을 미칠 수 있다는 근거들이 보고된 바 있다. 최근에 활성형 비타민 D, 1,25(OH)2D3 (calcitriol)가 사람의 단핵구에서 TLR의 발현을 감소시켜 면역 조절 기능을 담당한다는 사실이 밝혀졌고, 자가 면역 질환의 여러 동물 연구에서 비타민 D의 투여 후 증상이 호전, 예방된 사례 등이 발표된 바 있어 비타민 D가 자가 면역 질환의 조절 가능한 외부인자로서 역할을 하고 있음이 제시되고 있다. 따라서 본 연구에서는 베체트병 환자 혈청의 vitamin D level과 TLR 발현 정도를 측정하고 이들의 correlation을 통해 vitamin D 의 자연 면역 (innate immunity)에 대한 조절 작용을 알아보고, 단핵구 세포 배양을 통해 이를 실험적으로 확인해 보고자 하였다. 연구 방법: 41명의 베체트병 환자군과 대조군으로 질환 대조군인 19명의 건선 대조군, 15명의 정상 대조군을 선정하여 혈청 25-hydroxyvitamin D 양을 측정하고, 혈액으로부터 분리된 단핵구의 CD16, TLR2, TLR4 발현 정도를 flow cytometric analysis와 semiquantitative RT-PCR 을 이용하여 측정하였다. 또한 TLR 발현과 ESR, CRP와 같은 질병 활성도와 혈청 내 hydroxyvitamin D 양의 관련성을 비교하였다. 그리고 THP-1 세포주, 정상인 단핵구, 베체트병 환자의 단핵구를 세포 배양한 후 1,25(OH)2D3 양을 달리하여 처리한 후 TLR2, TLR4의 발현, cytokine 양의 변화 등을 측정하였다. 연구 결과: 활동성 베체트병 환자군의 혈청 내 25-hydroxyvitamin D 양은 정상과 비교하여 낮은 경향을 보였다. 활동성 베체트병 환자군의 단핵구 TLR2, TLR4의 발현은 flow cytometric analysis와 RT-PCR에서 모두 대조군에 비해 통계학적으로 유의한 증가를 보였고, 베체트병 환자군에서 혈청 25-hydroxyvitamin D과 TLR2, TLR4의 발현 정도, 질병 활성도는 유의한 역비례 관계를 보였다. 단핵구 배양 시 1,25(OH)2D3 농도를 달리하여 처리한 결과 비타민 D가 농도에 비례하여 TLR2, TLR4 의 발현이 억제되었고, TLR2, TLR4 ligand 로 자극 후 TNF-α 양의 변화 또한 비타민 D 농도가 증가함에 따라 감소하는 경향을 보였다. 또한 같은 조건 하에서 TLR2, TLR4 ligand 로 정상인의 단핵구와 베체트 환자의 단핵구를 각각 자극했을 때 TNF-α의 양이 베체트 환자군에서 정상인 보다 유의하게 증가하는 결과를 볼 수 있었다. 결론: 본 연구 결과는 베체트병 환자군에서 혈청 비타민 D 양이 감소해 있음을 확인함으로써 비타민 D의 결핍이 활성 베체트의 위험 인자가 될 수 있음을 시사하였다. 또한 베체트병과 TLR 발현의 관련성을 통해 비타민 D가 베체트병 환자 단핵구의 TLR 발현, 기능을 억제함으로써 자연 면역으로부터 유도되는 만성 염증 과정에 대한 면역 조절 기능을 가짐을 보여주었다."―ABSTRACT― = ii LIST OF FIGURES = vi LIST OF TABLES = vii I. INTRODUCTION = 1 II. MATERIALS AND METHODS = 4 A. SUBJECTS = 4 B. MATERIALS = 4 C. METHODS = 6 1. Serum 25-hydroxyvitamin D measurement = 6 2. Flow cytometry = 6 3. Semiquantitative RT-PCR = 7 4. Cell culture and measurement of TNF-α in supernatants = 8 5. Statistical analysis = 9 III. RESULTS = 10 1. Participant characteristics = 10 2. Vitamin D level = 11 3. Increased expression of TLR2, TLR4 on monocytes from patients with active BD = 13 4. Increased expression of TLR2 and TLR4 mRNA in active BD patients = 15 5. Correlation between TLR expression and serum vitamin D levels = 16 6. In vitro effect of vitamin D on TLR2, TLR4 expression = 17 7. In vitro cytokine analysis confirming vitamin D effect on functional consequences of TLR2, TLR4 = 19 IV. DISCUSSION = 23 V. CONCLUSION = 28 REFERENCES = 29 ―국문 요약― = 33"Maste

Recent Developments in Coated Hardmetal Cutting Tools

本稿에서는 化學蒸着法(CVD)에 依한 Coating으로 Metal protection方法을 紹介하였다. 被覆 切削工具의 生産活動에 큰 活氣를 불어 넣어준 最近 硏究活動의 進步는 많은 超硬合金 製造會社로 하여금 超硬合金에 Titanium Carbide(TiC), Titanium Nitride(TiN), Titanium Carbonitride[Ti(CN)], Alumina(TiC+Al₂O₃, Double layer), Titanium Ozycarbide[Ti(CO)], Hafnium Carbide(HfC), Hafnium Nitride(HfN)를 얇게 被覆시킨 切削工具를 販賣케 하는데 큰 도움을 주었으며 被覆 超硬製品의 需要는 앞으로 增加할 것이 豫想된다.In this review the protection of metalsusing coatings produced by Chemical Vapor Deposition(C.V.D) is discussed. Developments that has led to a great resurgence in the activity of manufacturing Coated Cutting tools has been marketing by various companies of cemented carbide tool coated by C.V.D. process with a thin layer of TiN, TiC, Ti(CN), TiC+Al₂O₃, Ti(CO), HfN, HfC.In this review the protection of metalsusing coatings produced by Chemical Vapor Deposition(C.V.D) is discussed. Developments that has led to a great resurgence in the activity of manufacturing Coated Cutting tools has been marketing by various companies of cemented carbide tool coated by C.V.D. process with a thin layer of TiN, TiC, Ti(CN), TiC+Al₂O₃, Ti(CO), HfN, HfC

A Study on the Plane Strain Fracture Toughness of WC-Co and TiC-Ni Composites

본연구에서는 WC-Co 및 TiC-Ni계 복합재료의 탄화물 입도, 결합상의 평균자유 행로, 합금원소 및 탄화물의 체적분율의 변화에 따른 평면변형 파괴인성을 방전가공에 의해 노?「? 부여한 SENB시편을 사용하여 측정하였다. 또한 복합재료인 WC-Co 및 TiC-Ni합금의 기계적 성질을 조사하기 위하여 경도, 항절력, 충격강도 및 Palmqvist 균열저항도 측정하였으며 얻어진 결론은 다음과 같다. 1) 항절력 시험결과 항절력은 결합상의 진평균 자유행로의 임계값에서 최대 값을 갖는다. 2) 충격강도는 결합상의 양에 따라 증가하나 합금의 탄화물 입도에 따른 영향은 거의 없다. 3) Palmqvist 균열저항 시험으로 부터 얻어진 결과는 10³/W=AH-B이며 여기서 W는 균열저항 계수, H는 비커스 경도이며 상수 A,B는 WC-Co계 합금의 경우는 각각 0.0175, 14.7 값을 갖으며 TiC-Ni계 합금의 경우는 각각 0.0175, 16.6 값을 갖는다. 이 관계식은 초겅합금의 연구와 품질관리에 유용한 식이 될 수 있다. 4) 복합재료의 평면변형 파괴인성(K??)은 현미경 조직인자 중 특히 결함상의 진평균 자유행로와 탄화물의 분리정도(1-C)에 의존하며 파괴인성은 복합재료의 경도 증가에 따라 직선적으로 감소한다. 선형탄성 파괴역학에 근거로 부터 계산된 임계변형에너지 해방률 G??는 진평균 자유행로의 증가와 더불어 직선적으로 증가한다.The plane strain fracture toughness(K??) of WC-Co and TiC-Ni composites was measured as a function of carbide grain size, mean free path of binder, alloying elements and volume fraction of carbide using single-edge notched beam(SENB) specimens of whigh notch formed by electron discharge machining(EDM). To evaluate the mechanical behavior of WC-Co and TiC-Ni composites, measurements of hardness, transverse rupture strength(TRS), impact strength and Palmqvist crack resistance were employed. The results obtained are as foliows: 1) In transverse rupture test, it has been found that TRS reaches a maximum value at the critical value of true mean free path of binder. 2) Impact strength increased with the increase of binder content, but the effect of carbide grain size was relatively small. 3) The empirical relationship between Palmqvist test crack resistance(W) and Vicker's hardness(H?) is as follows : 10³/W = AH - B where constants A and B are 0.0175 and 14.7 respectively for WC-Co base composites and 0.0175 and 16.6 for TiC-Ni base composites. It is considered that this relationship will be very useful for bath the development of cemented carbides and quality control is the production line. 4) The plane strain fracture toughness(K??) of composites depends on the microstructural parameters, particularly on the true mean free path(λ) of binder content and decree of separation of carbide grains(1-C). The fracture toughness decreased linearly with the increasing hardness of composites. The critical strain energy release rate(G??) increased linearly with the increase of the true mean free path.The plane strain fracture toughness(K??) of WC-Co and TiC-Ni composites was measured as a function of carbide grain size, mean free path of binder, alloying elements and volume fraction of carbide using single-edge notched beam(SENB) specimens of whigh notch formed by electron discharge machining(EDM). To evaluate the mechanical behavior of WC-Co and TiC-Ni composites, measurements of hardness, transverse rupture strength(TRS), impact strength and Palmqvist crack resistance were employed. The results obtained are as foliows: 1) In transverse rupture test, it has been found that TRS reaches a maximum value at the critical value of true mean free path of binder. 2) Impact strength increased with the increase of binder content, but the effect of carbide grain size was relatively small. 3) The empirical relationship between Palmqvist test crack resistance(W) and Vicker's hardness(H?) is as follows : 10³/W = AH - B where constants A and B are 0.0175 and 14.7 respectively for WC-Co base composites and 0.0175 and 16.6 for TiC-Ni base composites. It is considered that this relationship will be very useful for bath the development of cemented carbides and quality control is the production line. 4) The plane strain fracture toughness(K??) of composites depends on the microstructural parameters, particularly on the true mean free path(λ) of binder content and decree of separation of carbide grains(1-C). The fracture toughness decreased linearly with the increasing hardness of composites. The critical strain energy release rate(G??) increased linearly with the increase of the true mean free path