Correlations between in-flight particle, splat and coating microstructure of thermally sprayed Ni20Cr were investigated. Flame spray and arc spray systems were employed for spraying Ni20Cr powder and Ni20Cr wire, respectively. The results showed that the arc spray process produced a broader size distribution for both in-flight particles and splats compared to flame process. Flower-like splat morphology was obtained from the arc spray whereas a pancake-like splat was obtained by flame spray. Ni20Cr coating sprayed by arc process had a denser microstructure, lower porosity and better adhesion at the interface.

Thermal management technology is a critical element in all new chip generations, caused by a power multiplication combined with a size reduction. A heat sink, mounted on a base plate, requires the use of special materials possessing both high thermal conductivity (TC) and a coefficient of thermal expansion (CTE) that matches semiconductor materials as well as certain packaging ceramics. In this study, nano tungsten coated copper powder has been developed with a wide range of compositions, 90W-10Cu to 10W-90Cu. Powder technologies were used to make samples to evaluate density, TC, and CTE. Measured TC lies among theoretical values predicted by several existing models.

New manufacturing processes, such as thermochemical, mechanochemical and chemical vapor condensation processes have been developed to obtain nanostructured WC/Co materials. Nanoscale size WC/Co composite powders of near 100-150nm can be synthesizes by thermochemical and mechanochemical processes using water soluble precursors. Non-agglomerated and nano sized WC powder can be synthesized by the chemical vapor condensation process using metallorganic precursors as starting materials. In this paper, the scientific and technical issues on synthesis and consolidation of nanostructured WC/Co alloys produced by new chemical processes are introduced.

Based on theoretical analysis, a new general equation of mean particle size applicable to both conventional atomization methods and new atomization processes is presented. In gas atomization, it is equivalent with and can be changed into Lubanska Equation. In centrifugal atomization, it can be changed into the equations that are currently the most widely used. In water atomization, it is similar to the equation proposed by Grandzol and Tallmadge. According to the universal equation, new correlations for mean particle size in novel atomization processes such as Hybrid Atomization and Multistage Atomization were proposed and agreed with our experimental data well.

새로운 급속소결방법인 고주파유도가열 소결법과 펄스전류활성 소결법을 이용하여 습식 볼밀링으로 혼합한 WC-8wt.%Co분말에 60MPa의 압력과 90%의 고주파출력 또는 2800A의 필스전류를 가하여 상대밀도가 98.6% 이상인 초경재료를 2분이내의 짧은 시간에 제조하였다. 초기의 WC분말의 입도가 미세해짐에 따라 고주파유도가열 소결법과 펄스전류활성 소결법 모두 소결시간이 단축되는 경향을 보였으며 그 소결체의 결정립 크기도 감소하였다. 고주파유도가열 소결

급속소결방법인 고주파유도가열 소결법과 펄스전류활성 소결법을 이용하여 습식 볼밀링으로 혼합한 WC-8wt.%Ni분말에 60MPa의 압력과 고주파유도가열장치의 경우 전체 용량 (15kw)의 90%에 해당하는 고주파출력을, 펄스전류활성 소결장치의 경우 2800A의 펄스전류를 가하여 치밀한 소결체를 2분이내의 짧은 시간에 제조하였다. WC 초기입자크기가 증가함에 따라 제조된 소결체의 입자크기와 평균자유행로는 증가하였다. 또한 WC 결정립 크기가 증가함에 따라

In this study the nanostructured ceramics have been fabricated by the combined application of magnetic pulsed compaction (MPC) and subsequent spark plasma sintering (SPS), and their density and hardness properties were investigated. The prepared by the combined processes showed an increase by in density, approaching the value close to the true density, and an enhancement by in hardness, compared to those fabricated by MPC or static compaction method followed by sintering treatment.

본 연구는 과학 영재 프로그램을 개발하고 개선하는데 반영하고자 2002년도 서울 대학교 과학 영재 교육센터에서 운영된 과학 영재 프로그램의 각 주제에 제시된 학습 목표, 과학적 모형, 과학 탐구의 인지 과정을 분석하였다. 교육 목표와 과학적 모형, 탐구 활동의 세 요소들은 과학 교육 과정의 구성에 있어서 중요하다는 판단 아래 각 요소들이 제시된 정도를 파악한 후 이들의 수준이 영재 학생들의 인지적 요구를 충족시키는지에 초점을 두어 분석 결과를 해석하였다. 이에 따라 교육 목표의 인지 영역 중에서 상위 사고력 영역에 해당하는 종합 영역, 과학적 모형 중에서 상위수준의 추상성과 복잡성 모형인 다 개념-과정 모형, 과학 탐구의 인지 과정 중 창의성 영역에 해당하는 실험 설계의 인지 과정이 과학 영재 학생들을 가르치는 데 중요한 항목임을 전제하였다. 분석 결과 서울 대학교 과학 영재 프로그램의 각 주제에 제시된 교육 목표는 상위사고력 영역과 하위사고력 영역이 비슷한 비율로 나타나며, 그 중에서 종합 영역은 낮게 나타났다. 과학적 모형은 다 개념-과정 모형보다는 단일 개념 모형이 많았으며 추상성 수준은 중간 정도였다. 과학 탐구의 인지 과정은 실제 과학 탐구의 인지 과정을 고르게 다루지는 않았다. 특히 실험 설계의 인지 과정은 적게 다루고 있었다. 따라서 분석한 과학 영재 프로그램이 과학 영재들의 인지적 요구를 충족시키기 위해서는 종합 영역의 교육 목표, 다 개념-과정 모형, 실험 설계의 인지 능력을 더 많이 반영해야 한다.

Four different mechanical alloying(MA) processes were employed to fabricate very fine intermetallic compound particles dispersed Al composite materials(MMC) with Al-4at.%Zr composition. Phase transformations including phase stability during MA and heat treatment processes were investigated. Part of Zr atoms were dissolved into Al matrix and part of them reacted with hydrogen produced by decomposition of PCA(methanol) to form hydride during first MA process. These hydrides disappeared when alloy powders were heat treated at . Stable dispersoids with structure were formed by heat treating the mechanically alloyed powders at . On the other hand, metastable dispersoids with structure were formed during first MA of powers with Al-25at.%Zr composition. These metastable dispersoids transformed to stable with structure when heat treated above .

Clusters of galaxies generally form by the gravitational merger of smaller clusters and groups. Major cluster mergers are the most energetic events in the Universe since the Big Bang. The basic properties of cluster mergers and their effects are discussed. Mergers drive shocks into the intracluster gas, and these shocks heat the intracluster gas. As a result of the impulsive heating and compression associated with mergers, there is a large transient increase in the X-ray luminosities and temperatures of merging clusters. These merger boost can affect X-ray surveys of clusters and their cosmological interpretation. Similar boosts occur in the strong lensing cross-sections and Sunyaev-Zeldovich effect in merging clusters. Merger shock and turbulence associated with mergers should also (re)accelerate nonthermal relativistic particles. As a result of particle acceleration in shocks and turbulent acceleration following mergers, clusters of galaxies should contain very large populations of relativistic electrons and ions. Observations and models for the radio, extreme ultraviolet, hard X-ray, and gamma-ray emission from nonthermal particles accelerated in these shocks will also be described. Gamma-ray observations with GLAST seem particularly promising.

The purpose of this study is to investigate how Korean primary school L2 readers construct intertextual meaning and how they relate their conceptions or beliefs about reading to their intertextualtity. School instructions or home literacy environments in English reading might influence L2 readers' reading conceptions and their reading processes which are in turn associated with their intertextual connections among the multiple texts. Though current literature in L2 reading has focused on great interest in the reading processes of a single story or text, little interest was given to L2 readers' intertextuality among the multiple stories. The researcher first diagnoses four Korean primary school readers' reading conceptions, followed by retrospective miscue reading analyses to investigate their reading processes. Finally, their intertextual connections among the five stories of adventure are examined by conducting think-aloud procedure. The results showed that L2 readers have their own reading conceptions and behaviors, which are influenced by their home literacy environment and school instructions. In addition, Korean EFL readers' conceptions of reading and behaviors are strongly connected with their intertextuality among the multiple stories.

It compared quality characteristics for the stone surface treatment system and its products. With the result, the flame burner equipment was mainly used to the surface treatment of granite, but it occurred greatly the high temperature, the rock fragment, the noise and dust. For the other side, the whetstone polishing machine for the polishing was a maintenance for the specific physical properties of stone, and it did not occur the stone fragment and the dust. The durability of the stone products due to the flame burner was investigated with that it falls to 20~25% more than the surface treatment by the whetstone polishing. Share's hardness of the polishing products in the durability test showed more greatly index than the flame burner and conventional product. The polishing products of Pochon stone in the case of the abrasion resistance showed great more 15% than the general products, more 9% than the products by the flame burner.

본 연구에서는 보통의 조리조건과 위생적 조리조건에서 김밥을 조리하였을 때에, 각 조리조건하에서의 식자재(원재료),조리자의 손, 조리환경(조리기구 및 조리실),그리고 완성된 김밥의 미생물 품질을 살펴보고 이를 토대로 김밥조리과정 중의 중요관리점(CCPs)을 관찰하였다. 김밥과 그 원재료, 조리자의 손, 그리고 조리기구(칼, 도마 및 김발)의 표준평판균, 대장균군, 분변성대장균군, 대장균, 황색포도상구균, 살모넬라균 등의 미생물을 식품공전에 준하여 측정하였으며 조리실의 미생물 오염도를 평가하였다. 모든 시료에서 대장균, 황색포도상구균 및 살모넬라균은 검출되지 않았으며 표준평판균, 대장균군 및 분변성대장균군은 보통의 조리조건에서보다 위생적 조건에서 현저하게 낮았다. 김밥 원재료 중 비가열재료에서는 가열재료보다 표준평판균 및 대장균군수가 많이 검출되었다. 두 조건에서조리실의 공중낙하균은 모두 양호한 수준이었다. 위생적 조리조건에서 만든 김밥은 보통의 조리조건에서 만든 김밥에 비하여 표준평판균과 대장균군이 1/100수준이었으나 아직 분변성대장균군이 검출되었다. 따라서 비가열재료, 조리기구 및 조리자의 손의 미생물 오염, 그리고 조리 중의 교차오염이 김밥 미생물 오염의 주요 근원으로 지적되며, 비가열재료의 취급, 조리기구의 세척과 소독 및 조리자의 손씻기 단계가 CCPs로 제시된다.