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Ti-6Al-4V 합금에서 고온산화시 합금원소가 내산화성에 미치는 영향
장중호,이대철 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.2
The oxidation behavior and morphological changes of Ti-6Al-4V alloy have been investigated in air over the temperatures ranging from 973K to 1273K. The phases of oxidation product have teen examined by X-ray diffractometer and scanning electron microscopy. They are composed of films of TiO₂ and Al₂O₃ mixture. The weight gains during the oxidation increase rapidly at temperature above 973K, which obey the parabolic law. The oxidation behavior of Ti-6A1-4V alloy lead to breakaway oxidation at high temperature, which is similar to that, of pure Ti. However, the oxidation rate of Ti-6Al-4V alloy is higher than that of pure Ti, because a porous mixture film of TiO₂ and α-Al₂O₃ formed in Ti-6Al-4V alloy is less protective than TiO₂ film formed in pure Ti. The growth rate of TiO₂ oxides in Ti-6Al-4V alloy is faster than that of α-Al₂O₃ at high temperature.
張重浩,蔡京洙,李大喆 全北大學校 1994 論文集 Vol.38 No.-
The oxidation behavior and mechanism of pure Ti has been investigated in air over the temperature range from 973K to 1273K. The phases of oxidation products and matrix have been examined by scanning electron microscopy, x-ray diffractometer and optical microscopy. The rate of oxidation of pure Ti follows a parabolic rate law in an initial stage of oxidation process but a linear rate law in the later stage. The transition from the parabolic to linear rate law take places when the thickness of oxide layer reaches a certain value, and the oxide layer formed thereafter contains a lot of defects which have been considered to form due to the stresses present at the matrix-oxide interface. The rate determining process in the overall oxidation of pure Ti is observed to be the inward diffusion of oxygen through the oxide layer.
장중호,최현철 한국통신학회 1999 韓國通信學會論文誌 Vol.24 No.6
12GHz-13GHz에서 동작하는 두 개의 선형 직교 편파된 신호를 분리전송하기 위한 협대역 직교모드편파분리기를 설계 및 제작하였다. 제안된 구조는 도파관 형태의 main arm과 side arm으로 구성되어 있다. 각 모드에 대한 전송손실 및 격리도 특성을 향상시키기 위하여 계단형 도파관 트랜스포머를 설계하고 인덕티브 포스트를 삽입하였다. 설계 제작한 직교모드편파분리기의 측정결과 각 모드에 대한 전송손실은 1dB이내, 각 포트의 격리도는 20dB이상을 보였다. This paper presents a narrow-band orthomode transducer(OMT) based on waveguide to waveguide transitions which can separate two linearly polarized orthogonal modes. This operates in the range 120Hz-13GHz frequency band. It consists of two parts, main arm and side arm. Stepped transformers are designed and an inductive post is inserted to improve the characteristics of the transmission loss and isolation. This paper also presents results from fabricated OMT These results show that the transmission loss is less than 1dB and the isolation between the ports for the OMT is above 20dB.
장중호,이대철 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.5
The oxidation kinetics and morphological changes of oxides in intermetallic compound TiAl containing 37wt% Al have been investigated in air over the temperature range of 973K to 1473K. The phases of oxidation products have been examined by X-ray diffractometer and scanning electron microscope. They are composed of four layers, that is, TiO₂, Al₂O₃, TiO₂+Al₂O₃, Ti₃Al from the outer layer. The mass gain during the oxidation increases rapidly at temperatures above 1173K, obeying the parabolic law. The oxidation resistance is related to the characteristics of a protective oxide layer(Al₂O₃, or TiO ₂). The existance of the Al₂O₃ layer has improved oxidation resistance of TiAl. However, this Al₂O₃ layer is not dense enough to prevent the oxidation above 1173K. The growth rate of TiO₂ is faster than that of Al₂O₃ at high temperature. Oxidation rate of TiAl is controlled by titania-forming kinetics above 1273K but controlled by alumina-forming kinetics below 1173K.
張重浩,蔡京洙,李大喆 全北大學校 1995 論文集 Vol.40 No.-
The oxidation behavior and mechanism of intermetallic compounds TiNi has been investigated in air over the temperature range from 923K to 1073K. The phases of oxidation products and matrix have been examined by scanning electron microscopy, x-ray diffractometer and optical microscopy. The rate of oxidation in intermetallic compound TiNi follows the parabolic rate law in an initial stage of the oxidation process but it does not follow the parabolic rate law in the later stage. Oxidation products formed on the matrix consist of a layer structure of TiO_2(rutile), TiO_2 phase containing TiNiO_3 particles, TiO_2, Ni phase containing Ti, TiN_i3 phase and TiNi matrix in sequence from the outer side. The rate determining process in the overall oxidation of TiNi is the inward diffusion of oxygen through the oxide layer and the outward diffusion of Ti through the Ni phase.
고유함수전개법을 이용한 비대칭 유전체 원주공진기의 공진특성해석
류원열,민경호,장중호,전오곤,이창화,최현철 경북대학교 센서기술연구소 1998 센서技術學術大會論文集 Vol.9 No.1
The resonant frequency of the dielectric rod resonator which is surrounded by cylindrical cavity can be calculated very exactly by using eigenfunction expansion method in the concept of electric and magnetic wall from the symmetry. But if the supporter is put in the cavity, the symmetry disappears. Thus this method has some errors. In this paper, the resonant frequency of the asymmetric dielectric rod resonator was calculated by using the eigenfunction expansion method. Also, the effect of the supporter was discussed. Then we found that the resonant frequency was more affected in the case of TM mode than TE or Hybrid modes as the length of the supporter was longer.