The corrosion resistance of submerged entry nozzle (SEN) materials were investigated for high-class steel manufacturing. Composite samples were fabricated by mixing ZrO2, Al2O3, MgO, mullite, spinel, and carbon. The raw materials were mixed with attrition milling, compacted in a uniaxial pressure of 200MPa and calcined at 1000˚C for 3 h in N2 atmosphere. The bulk density and apparent porosity of the calcined samples were measured by the liquid displacement method in water using Archimedes's principle. The corrosion resistance of the samples were measured by cup test with mold powder at 1550˚C for 2 h. The microstructure and elemental analysis of samples were observed by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), and X-ray diffraction pattern (XRD). The XRD result shows that the starting raw materials were crystalline phase. The microstructure of fabricated specimen was investigated before and after corrosion tests at 1000˚C and 1550˚C for 2h. ZrO2-C composite showed good resistance in the slag corrosion test. Among the composite oxide materials, ZrO2-Al2O3-C and ZrO2-MgO-C showed better resistance than ZrO2-C in the slag corrosion test. The diameter variation index of ZrO2-C refractory was 16.1 at 1000˚C for 2 h. The diameter variation index of the ZrO2-Al2O3-C refractory was larger than that of the ZrO2-C refractory at 1550˚C for 2 h.

We demonstrate optical cross-sectional imaging system implemented with high-resolution interferometry and present oral diagnostic imaging results obtained without any physical sectioning. High-resolution interferometry could be performed with utilizing broadband optical source and employment of beam scanning device to high-resolution interferometer constitutes optical imaging system for non-invasive cross-sectional view at real-time. The optical imaging system is implemented with fiber-optic devices for compactness and optical probe head is realized by using single mode optical fiber and miniaturized actuator, which is properly designed for the application to dental imaging. The basic performance of the optical imaging system, for example, such as resolution, imaging depth, and sensitivity is suggested to prove high-resolution optical imaging performance. Feasibility of the developed optical imaging system performance in the application of dental diagnostic is proved with demonstrating non-invasively obtained cross-sectional images. The imaging quality suggested in the images could be applied to assessment of oral diseases and used for alternative imaging modality to X-ray diagnostic method overcoming disadvantage of low-image resolution. The imaging performance enabling real-time image reconstruction also could be exploited as early oral diagnostic apparatus prior to microscopic observation under H&E staining.

세라믹재료의 동탄성계수 측정을 위한 공진주파수 측정장치를 구성하였다. 구조용 세라믹 재료로 이용되는 Al2O3, SiC, Si3N4의 온도를 1200˚C까지 50˚C의 온도간격으로 올리면서 torsional resonant frequency와 flexural resonant frequency를 측정하고, 측정된 공진주파수로부터 각 재료의 탄성계수를 구하였다. SiC의 경우는 1200˚C의 온도까지 탄성계수가 선형적으로 감소하였으나, Al2O3와 Si3N4의 경우에는 각각 1000˚C와 800˚C까지는 선형적으로 감소하나, 그 이상의 온도에서는 탄성게수의 감소폭이 증가하는 현상을 보였다. 이러한 현상은 다결정재료에서의 grain boundary sliding에 의한 것으로 알려져 있다. 상온에서 공진법으로 측정된 동탄성계수의 측정결과는 초음파법으로 측정한 결과와 비교하였는데, 4% 내에서 서로 일치하는 결과를 보였다.

LPCVD(Low Pressure Chemical Vapor Deposition) System을 이용하여 여러가지 증착 변수에 따른 실리콘 박막의 표면형상에 대해 고찰하였다. 중착압력, 중착온도, 반응기체의 유속에 따라 증착층의 표면형상이 큰 변화를 나타냈으며, 증착압력과 반응기체의 유속이 증가할수록 유효면적이 최대가 되는 증착온도가 증가하였다. 이러한 실험결과는 안정한 핵의 생성률이 최대가 될때 유효표면적이 최대가 된다는 가정으로부터 유도된 식과 일치하는 결과를 나타냈다.

교량 지지용으로 사용되는 강재 케이블에 대한 장력측정은 교량 안전관리의 중요한 측정항목이다. 현재 케이블에 걸린 장력을 진동법과 로드셀로 측정하고 있으며, 최근에는 선진국에서 자기적 방식에 의한 장력측정 방법을 연구하여 이에 대해 여러 가지 결과물을 제공하고 있다. 그러나 아직 우리나라에서는 이에 대한 체계적인 연구가 수행되지 않고 있어 자기적 방식에 의한 장력측정 연구를 시작하였으며 장력측정 정밀도 향상을 위해 연구하고 있다. 자기적 방식의 장력측정에서 강재 케이블 내의 온도와 자기장에 대한 영향을 검토해야 한다. 금번 논문에서는 온도에 따라 장력센서의 출력특성을 시험하였고 주어진 자기장에서 온도보정계수를 도출하였으며 시험실 내의 장력측정 시스템에 보정계수를 적용하여 케이블 장력에 따른 장력센서의 출력특성에 대한 시험 결과를 분석하고 평가하였다.

For diagnoses of digestive organs, capsule endoscopes are widely used and offer valuable information without patient’s discomfort. A general capsule endoscope which consists of image sensing module, telemetry module and battery is able to move along gastro-intestinal tracts passively only through peristaltic waves. Thus, it is likely to have some limitations for doctor to acquire images from the desired organs and to diagnose them effectively. As solutions to these problems, a locomotive function of capsule endoscopes has being developed. We have proposed a capsule-type microrobot with synchronized multiple legs. However, the proposed capsular microrobot also has some limitations, such as low speed in advancement, inconvenience to controlling the microrobot, lack of an image module, and deficiency in a steering module. In this paper, we will describe the limitations of the locomotive microrobot and propose solutions to the drawbacks. The solutions are applied to the capsular microrobot and evaluated by in-vitro tests. Based on the experimental results, we conclude that the proposed solutions are effective and appropriate for the locomotive microrobot to explore inside intestinal tracts.