Yong-Kwon Kim

Multiplex Immunoassay Using Fluorescent-Surface Enhanced Raman Spectroscopic Dots for the Detection of Bronchioalveolar Stem Cells in Murine Lung

Immunoassays using nanomaterials have been rapidly developed for the analysis of multiple biomolecules. Highly sensitive and biocompatible surface enhanced Raman spectroscopy-active nanomaterials have been used for biomolecule analysis by many research groups in order to overcome intrinsic problems of conventional immunoassays. We used fluorescent surface-enhanced Raman spectroscopic dots (F-SERS dots) to detect biomolecules in this study. The F-SERS dots are composed of silver nanoparticle-embedded silica nanospheres, organic Raman tagging materials, and fluorescent dyes. The F-SERS dots demonstrated highly sensitive, selective, and multifunctional characteristics for multiplex targeting, tracking, and imaging of cellular and molecular events in the living organism. We successfully applied F-SERS dots for the detection of three cellular proteins, including CD34, Sca-1, and SP-C. These proteins are simultaneously expressed in bronchioalveolar stem cells (BASCs) in the murine lung. We analyzed the relative expression ratios of each protein in BASCs since external standards were used to evaluate SERS intensity in tissue. Quantitative comparisons of multiple protein expression in tissue were first attempted using SERS-encoded nanoprobes. Our results suggested that immunoassays using F-SERS dots offered significant increases in sensitivity and selectivity. Such immunoassays may serve as the primary next-generation labeling technologies for the simultaneous analysis of multiple biomolecules.

A Technique for Defect Detection of Condenser Tube in Support Plate Region using Guided Wave

Abstract General condensers consist of many tubes supported by tube sheets and support plates to prevent the deflection of the condenser tubes. When a fluid at high pressure and temperature runs over the tubes for the purpose of transferring heat from one medium to another, the tubes vibrate and their surface comes into contact with the support plates. This vibration causes damage to the tubes, such as cracks and wear. We propose an ultrasonic guided wave technique to detect the above problems in the support plate region. In the proposed method, the ultrasonic guided wave mode, L(0,1), is excited using an internal transducer probe from a single position at the end of the tube. In this paper, we present a preliminary experimental verification using a super stainless tube and show that the defects can be discriminated from the support signals in the support region.Key Words : Ultrasonic guided-wave, Condenser tube, Support plate region, Internal transducer probe 연구논문1. 서 론 발전 분야에 널리 사용되는 설비 중 복수기 장치는 열에너지를 다른 유체에 열전달을 이용하는 발전설비 중 하나이다. 열교환기 내부 수많은 튜브는 열 교환 효율을 높이기 위해 두께가 매우 얇아 결함에 상당히 취약하여 결함발생 시 쉽게 파괴될 수 있어 손상을 감지하고 그 상태를 최적화하기 위해 비파괴평가가 진행 되고 있다. 열교환기 튜브를 평가하는 기존의 방법은 국부 검사법(ponit by point inspection)으로 와전류를 이용한 와전류탐상검사(ECT)와 원거리와 전류검사(RFECT), 내삽형 초음파검사(IRIS), 육안검사(Endoscope testing)가 활용되고 있다. 열교환기튜브에서 결함이 집중적으로 발생되는 영역은 잔류응력과 유체이동이 집중되는 확관부에서 주로 발생한다. 또한 튜브지지판과 곡관부에서도 결함이 발생되는데 이 부위는 기존의 검사방법인 국부검사법을 적용하여 튜브를 평가하기에 어려움이 있다. 와전류신호는 임피던스 변화를 이용하여 결함을 검출하는데 결함신호 뿐만 아니라 재질과 형상에도 민감하게 변화한다. 튜브 지지판 영역에서는 지지판 재질의 영향으로 결함신호를 정량적으로 평가하는데 많은 어려움이 있다

Characterization of Water Absorption by CFRP Using Air-Coupled Ultrasonic Testing

Carbon-fiber-reinforced plastic (CFRP) composites are increasingly being used in a variety of industry applications, such as aircraft, automobiles, and ships because of their high specific stiffness and high specific strength. Aircraft are exposed to high temperatures and high humidity for a long duration during flights. CFRP materials of the aircraft can absorb water, which could decrease the adhesion strength of these materials and cause their volumes to change with variation in internal stress. Therefore, it is necessary to estimate the characteristics of CFRP composites under actual conditions from the viewpoint of aircraft safety. In this study air-coupled ultrasonic testing (ACUT) was applied to the evaluation of water absorption properties of CFRP composites. CFRP specimens were fabricated and immersed in distilled water at for 30, 60, and 120 days, after which their ultrasonic images were obtained by ACUT. The water absorption properties were determined by quantitatively analyzing the changes in ultrasonic signals. Further, shear strength was applied to the specimens to verify the changes in their mechanical properties for water absorption.

Evaluation of Thickness Reduction in an Aluminum Sheet using SH-EMAT

In this paper, a non-contact method of evaluating the thickness reduction in an aluminum sheet caused by corrosion and friction using SH-EMAT (shear horizontal, electromagnetic acoustic transducer) is described. Since this method is based on the measurement of the time-of-flight and amplitude change of guided waves caused from the thickness reduction, it provides information on the thinning defects. Information was obtained on the changes of the various wave features, such as their time-of-flight and amplitude, and their correlations with the thickness reduction were investigated. The interesting features in the dispersive behavior of selected guided modes were used for the detection of thinning defects. The measurements of these features using SH waves were performed on aluminum specimens with regions thinned by 7.2% to 29.5% of the total thickness. It is shown that the time-of-flight measurement provides an estimation of the thickness reduction and length of the thinning defects.

Evaluation of Thickness Reduction in a Thin Plate Using a Non‐Contact Guided Wave Technique

Ultrasonic guided waves are widely being studied and successfully applied to various non‐destructive tests with the advantage of a long range inspection. Recently, non‐contact methods are also adopted and combined with the guided wave techniques. In this paper, an advanced technique for the nondestructive detection of thinning defects simulating hidden corrosion in thin plates using non‐contact guided waves is presented. The proposed approach uses EMAT(Electro‐Magnetic Acoustic Transducer) for the non‐contact generation and detection of guided plate waves in aluminum plates. Interesting features of the dispersive behavior in selected wave modes are used for the detection of plate thinning. The experimental results show that the mode cutoff measurements provide a qualitative measurement of thinning defects and change in the mode group velocity can be used as quantitative parameter of thinning depth measurement.

Miniature fluorescence detection system for protein chips

We report the development of miniature fluorescence detection systems that employ miniature prism, mirrors and low cost CCD camera to detect the fluorescence emitted from 40 fluorescently-labeled protein patterns without scanner. This kind of miniature fluorescence detection systems can be used in point of care. We introduce two systems, one uses prism + mirror block and the other uses prism and two mirrors. A large NA microscope eyepiece and low cost CCD camera are used. We fabricated protein chip containing multi-pattern BSA labeled with Cy5, using MEMS technology and modified the surface chemically to clean and to immobilize proteins. The measurements show that the combination of prism and mirrors can homogenize elliptical excitation light over the sample with higher optical efficiency, and increase the separation between excitation and fluorescence light at the CCD to give higher signal intensity and higher signal to noise ratio. The measurements also show that protein concentrations ranging from 10 ng/ml to 1000 ng/ml can be assayed with very small error. We believe that the proposed fluorescence detection system can be refined to build a commercially valuable hand-held or miniature detection device.

Time Frequency Domain Analysis of the Dispersion of Guided Wave Modes

One of unique characteristics of guided waves is a dispersive behavior that guided wave velocity changes with an excitation frequency and mode. In practical applications of guided wave techniques, it is very important to identify propagating modes in a time-domain waveform for determination of defect location and size. Mode identification can be done by measurement of group velocity in a time-domain waveform. Thus, it is preferred to generate a single or less dispersive mode. But, in many cases, it is difficult to distinguish a mode clearly in a time-domain waveform because of superposition of multi modes and mode conversion phenomena. Time-frequency analysis is used as efficient methods to identify modes by presenting wave energy distribution in a time-frequency. In this study, experimental guided wave mode identification is carried out in a steel plate using time-frequency analysis methods such as wavelet transform. The results are compared with theoretically calculated group velocity dispersion curves. The results are in good agreement with analytical predictions and show the effectiveness of using the wavelet transform method to identify and measure the amplitudes of individual guided wave modes.Copyright