Cemented tungsten carbide has been used in cutting tools and die materials, and is an important industrial material. When the particle size is reduced to ultrafine, the hardness and other mechanical properties are improved remarkably. Ultrafine cemented carbide with high toughness and hardness is now widely used. The objective of this study is synthesis of nanostructured WC-Co powders by liquid phase method of tungstate. The precursor powders were obtained by freezen-drying of aqueous solution of soluble salts, such as ammonium metatungstate, cobalt nitrate. the final compositions were WC-10Co. In the case of liquid phase method, it can be observed synthesis of WC-10Co. The properties of powder produced at various temperature, were estimated from the SEM, BET and C/S analyser.

As the performance of microelectronic devices is improved, the use of copper as a heat dissipation member is increasing due to its good thermal conductivity. The high thermal conductivity of copper, however, leads to difficulties in the joining process. Satisfactory bonding with copper is known to be difficult, especially if high shear and peel strengths are desired. The primary reason is that a copper oxide layer develops rapidly and is weakly attached to the base metal under typical conditions. Thus, when a clean copper substrate is bonded, the initial strength of the joint is high, but upon environmental exposure, an oxide layer may develop, which will reduce the durability of the joint. In this study, an epoxy adhesive formulation was investigated to improve the strength and reliability of a copper to copper joint. Epoxy hardeners such as anhydride, dihydrazide, and dicyandiamide and catalysts such as triphenylphosphine and imidazole were added to an epoxy resin mixture of DGEBA and DGEBF. Differential scanning calorimetry (DSC) analyses revealed that the curing temperatures were dependent on the type of hardener rather than on the catalyst, and higher heat of curing resulted in a higher Tg. The reliability of the copper joint against a high temperature and high humidity environment was found to be the lowest in the case of dihydrazide addition. This is attributed to its high water permeability, which led to the formation of a weak boundary layer of copper oxide. It was also found that dicyandiamide provided the highest initial joint strength and reliability while anhydride yielded intermediate performance between dicyandiamide and dihydrazide.

Electrical discharge machining (EDM) is an attractive machining technique but it requires electrically conductive ceramic materials. In this study, Alumina matrix composites reinforced with CNTs were fabricated through CNT purification, mixing, compaction and spark plasma sintering (SPS) processes. nanocomposites with the different CNT concentrations were synthesized. The mechanical and electrical characteristics of /CNTs composites were examined in order to apply the materials to the EDM process. In addition, micro-EDM using wire electrical discharge grinding (WEDG) was conducted under the various EDM parameters to investigate the machining characteristics of machined hole by Field Emission Scanning Electron Microscope (FE-SEM). The results show that /CNTs 10%Vol. was more suitable than the other materials because high conductivity and large discharge energy caused violent sparks resulting in bad machining accuracy and surface quality.

The existing reliability evaluation models which have already developed by the corporations are so various because of using Maximum Likelihood Method. The existing models are very complicated owing to using system designing methods Therefore, it is very d

The development of low-k materials is essential for modern semiconductor processes to reduce the cross-talk, signal delay and capacitance between multiple layers. The effect of the CH4 concentration on the formation of SiOC(-H) films and their dielectric characteristics were investigated. SiOC(-H) thin films were deposited on Si(100)/SiO2/Ti/Pt substrates by plasma-enhanced chemical vapor deposition (PECVD) with SiH4, CO2 and CH4 gas mixtures. After the deposition, the SiOC(-H) thin films were annealed in an Ar atmosphere using rapid thermal annealing (RTA) for 30min. The electrical properties of the SiOC(-H) films were then measured using an impedance analyzer. The dielectric constant decreased as the CH4 concentration of low-k SiOC(-H) thin film increased. The decrease in the dielectric constant was explained in terms of the decrease of the ionic polarization due to the increase of the relative carbon content. The spectrum via Fourier transform infrared (FT-IR) spectroscopy showed a variety of bonding configurations, including Si-O-Si, H-Si-O, Si-(CH3)2, Si-CH3 and CHx in the absorbance mode over the range from 650 to 4000 cm-1. The results showed that dielectric properties with different CH4 concentrations are closely related to the (Si-CH3)/[(Si-CH3)+(Si-O)] ratio.

Calcia (CaO) stabilized cubic-HfO2 is studied by density functional theory (DFT) with generalized gradient approximation (GGA). When a Ca atom is substituted for a Hf atom, an oxygen vacancy is produced to satisfy the charge neutrality. The lattice parameter of a 2×2×2 cubic HfO2 supercell then increases by 0.02 Å. The oxygen atoms closest to the oxygen vacancy are attracted to the vacancy as the vacancy is positive compared to the oxygen ion. When the oxygen vacancy is located at the site closest to the Ca atom, the total energy of HfO2 reaches its minimum. The energy barriers for the migration of the oxygen vacancy were calculated. The energy barriers between the first and the second nearest sites, the second and the third nearest sites, and the third and fourth nearest sites are 0.2, 0.5, and 0.24 eV, respectively. The oxygen vacancies at the third and fourth nearest sites relative to the Ca atom represent the oxygen vacancies in undoped HfO2. Therefore, the energy barrier for oxygen migration in the HfO2 gate dielectric is 0.24 eV, which can explain the origin of gate dielectric leakage.

teacher s efficiency is an important factor. Recently, some schools installed an air conditioner in classroom, while most schools selected the built-in type air conditioner. However, the study on a valuation of thermal environment is not sufficient, especially in classroom. It is insufficient that the study is a valuation of thermal environment which considered valuation about indoor thermal environment diffusion angle and air volume. In this work, the change of thermal environment was investigated for five kinds of air diffusion angle(15∘, 30∘, 45∘, 60∘, 90∘) for ceiling type air conditioner. The vector and temperature distributions of air in the room were calculated by a 3-dimensional numerical method. This study was also conducted to calculate the Mean Age of Air and Predicted Mean Vote(PMV). This analysis showed that 30-45° is the optimum angle of diffusion in cooling mode and in heating mode.

A law of Korean product liability was enforced on 1st in July for 2002 years. Although it is later than the United States in 25 years, and more later than Japan in 7 years, it have been welcomed a new chances promoting the preservation of consumer"s safety and increasing business compactability toward the small and medium size enterprises. Up to now, The a large enterprise, which have concentrated in export of an advanced country, have already the resistant power against the law of Korean product liability, but the Korean medium and small-sized enterprises were concentrated mainly a domestic market or subcontracting business of a major big company. Relatively very week positions on this Low. If They cannot supply the most safest product in the market, then Those enterprise are confronting the difficulty for surviving. Now the product safety has become more important role to the small and medium size company. Therefore, this paper offered the object and the direction how the company must carry out measures on this product design stage applying safe engineering and Ergonomic Technology for the achieving ongoing development and progress of small ann medium size industry in Korea.

본 연구는 수출유통경로 지배구조결정과 이에 영향을 미치는 관련변수간의 관계 규명에 초점을 맞추고 있다. 본 연구에서 제시하고 있는 연구의 개념적 틀은 생산비용분석 모형과 거래비용분석 모형을 결합하여 설정하였다. 관련변수로는 거래비용요소인 자산특유성의 인적자산특유성, 물적자산특유성, 제품특유성 요인과 환경불확실성의 가변성1, 다양성, 가변성2 요인, 생산비용요소의 수출판매액, 수출집중도, 수출경험 요인, 그리고 심리적 요소의 심리적 거리 요인 등이 포함되었다. 또한 분석단위에 있어서는 통합경로, 준통합경로, 비통합경로의 3분법적 연구로 이루어졌다. 연구조사의 모집단은 수출에 종사하는 제조기업으로서 726개 업체에 대해 3차에 걸친 우편조사와 면접조사로 모두 454개의 사용 가능한 설문지를 확보하였다(응답를 63.2%). 가설검증은 판별분석에 의해 이루어졌으며, 판별분석의 외적타당성을 확보하기 위해 표본을 분석표본과 유보표본으로 구분하여 판별하였다. 아울러 분류결과에 의한 판별명중률과 우연기준에 의한 판별명중률을 비교함으로서 판별예측력의 개선을 도모하여 판별모형의 내적 타당성을 입증하였다. 본 연구의 마케팅 전략적 시사점은 첫째, 수출유통경로로 준통합경로의 중요성을 인식하여야 하고, 둘째, 거래파트너와 긴밀한 관계유지가 정립되어야 하며, 셋째, 거래파트너에 대한 상품판매 후의 애프터서비스 확대 도모가 요청되고, 넷째, 수출상대국의 문화적 거리감 이해 등이 중요하게 제시되고 있다.

이 연구는 상향식 교육과정 평가 모형을 개발하고 이를 적용하기 위한 협력적 실행 연구이다. 중앙 집중적인 교육과정 개발 체제를 따르는 우리나라의 상황을 고려해 볼 때, 교사는 교육과정 실행의 주체임에도 불구하고 국가 교육과정을 평가하고 이에 대한 개선 의견을 제안할 수 있는 공식적인 기회를 갖기 어려운 형편이었다. 이와 같은 문제의식에서 출발하여, 이 연구는 단위 학교 에서 현행 국가 교육과정을 평가하고자 할 때 적용할 수 있는 모형을 개발하고 이를 적용하였다. 연구자-참여자 간 협력을 통해 개발된 교육과정 평가 모형을 적용한 결과, 단위 학교에서 이루어지는 국가 교육과정 평가는 교사들이 국가 교육과정에 대한 이해와 참여의 필요성을 인식하는 계기를 제공하였고, 현장에 기반을 둔 유의미한 개선 의견을 도출하는 기회가 되었으며, 교육과정 제안자로서 국가 교육과정에 대한 ‘주인-되기’의 역동을 형성하는 과정임을 확인할 수 있었다. 연구 결과를 바탕으로, 이 글은 상향식 교육과정 평가 모형이 지속・확산되기 위한 향후 개선 과제를 제안하였다.

LoRa LPWAN 네트워크 시스템은 비면허 무선통신을 이용하고, Mems 기반 통합센서를 통하여 Data 계측 및 기존 계측센서의 무선통신을 구현한 시스템이다. 본 시스템은 기존의 무선계측시스템 대비 장거리 통신과 기존망을 활용한 기술적/경제적인 우수성을 갖고 있으며, 유선계측시스템 대비 시스템 구축장비의 최소화로 경제성을 확보하였다. 경제성 검토항목에서 기존 유선계측 시스템 대비 약 41%의 경제적인 절감효과가 가능하다는 것을 확인하였다. 또한 유지관리 및 운영적인 측면에서도 우수하기 때문에 향후 국내에서도 많은 교량에 설치가 된다면, 교량의 유지관리 분야의 우수한 시스템으로 발전되고, 재난(지진 산사태 등), 환경(오염물 측정 및 관리 등), 플랜트 분야(화재 안전 등)에도 폭넓게 사용되길 기대한다.