• 연구논문집
• /
• s.28
• /
• pp.229-238
• /
• 1998

Materials and parts required for nondestructive testing should be evaluated using with standard block. And it is ruled that standard blocks should be fabricated from same or similar material with test specimen. In order to manufacture and export materials and parts, quality assurance system should be required. In this paper, ultrasonic characteristics of ASTM 4340 steel ultrasonic standard block are investigated for nondestructive evaluation of udimet 720Li disc. Microstructures of udimet 720Li alloy are investigated using with optical and transmission electron microscope. Also ultrasonic transit time and attenuation are measured from high power ultrasonic analysis system with phase adjustment method. Conclusively, it is proved that 4340 steel ultrasonic standard block can be use for nondestructive evaluation of udimet 720Li disc.

• Journal of Biomedical Engineering Research
• /
• v.31 no.2
• /
• pp.129-133
• /
• 2010

Intense pulsed light(IPL) is a photo-therapeutic medical device using xenon lamps with optical characteristics of incoherence, defocusing, and polychromatic. IPL has been recognized as a representative medical therapeutic device with growth of domestic skin care market. However, there is no standard regulation manual and guideline to evaluate the safety and performance of IPL. International Electrotechnical Commission(IEC) is being statued "Technical Report IEC TR 60825-16" which is a guidelines for the safe use of intense light source equipment on humans and animals. In this study, a standard Korea Food & Drug Administration (KFDA) regulation for the safety and performance of IPL was suggested by developing minimal evaluation methods for optical parameters of IPL such as output energy density, pulse mode, spot size, wavelength and uniformity of output light. We expect that this study may be a step to statue a standard regulation manual and guideline for IPLs used in domestic.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.33 no.4
• /
• pp.615-623
• /
• 2006

The purpose of this study was to evaluate the specificity, sensitivity, and diagnostic power of caries activity test using LED fluorescence. The subjects of this study were 55 children of $6{\sim}7$ years old. LED light were irradiated to labial or buccal surface of all teeth. Fluorescence from initial carious lesion of teeth illuminated by an LED light was observed through barrier filter and the number of teeth showing lesion, size and position of lesion were counted. Streptococcus mutans colony counting and dDfFtT rate test were also done and their correlation was compared. And then specificity, sensitivity, diagnostic power of optical caries activity test using LED light were evaluated. 1. There was positive $correlation({\gamma}=0.43)$ between LED fluorescence test and Streptococcus mutans count(P<0.05). 2. When visual examination was defined to standard testing method, the specificity, sensitivity, diagnostic power of LED fluorescence test were 100%, 76.1%, and 100%. 3. When dDfFtT rate was defined to standard testing method, the specificity, sensitivity, diagnostic power of LED fluorescence test were 88.9%, 47.8%, and 95.7%. 4. When S. mutans colony counting was defined to standard testing method, the specificity, sensitivity, diagnostic power of LED fluorescence test were 100%, 58.7%, and 100%. Considering the above results, optical caries activity test using LED light could be regarded as a practical method because of its close relationship with microbiological caries activity test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.13-16
• /
• 2004

The reliability of 1.550m-wavelength InGaAs mesa waveguide photodiodes(WGPDs), which developed for 40-Gbps optical receiver applications, fabricated by metal organic chemical vapor deposition is investigated. Reliability is examined by both high-temperature storage tests and the accelerated life tests by monitoring dark current and breakdown voltage. The median device lifetime and the activation energy of the degradation mechanism are computed for WGPD test structures. From the accelerated life test results, the activation energy of the degradation mechanism and median lifetime of these devices in room temperature are extracted from the log-normal failure model by using average lifetime and the standard deviation of that lifetime in each test temperature. It is found that the WGPD structure yields devices with the median lifetime of much longer than $10^6$ h at practical use conditions. Consequently, this WGPD structure has sufficient characteristics for practical 40-Gbps optical receiver modules.

• Fire Science and Engineering
• /
• v.28 no.2
• /
• pp.9-13
• /
• 2014

This paper is basic study for development of the photoelectric-type smoke detector that is able to distinguish fire source as well as fire detection. For this subject, Light source and sensor which is normally used for the conventional smoke detector are assembled for the optical chamber. Using 3 type of the test fires (the paper fire, the wood fire, the flammable liquid fire) this paper attempts to find optical properties of each fire. These 3 type of fire are used in the testing of smoke detector according to UL 268 standard. As the result, there are disambiguated between the paper fire and the wood fire in scattering and reason of extinction in the flammable liquid fire is different from that of the paper and the wood fire.

• Journal of the Korean Magnetics Society
• /
• v.11 no.1
• /
• pp.38-44
• /
• 2001

The magnetic field standard below 1 mT with the resolution of 0.26 nT has been established. Earth magnetic field (EMF) is compensated automatically down to 0.1 nT/10 min. by a closed feedback system with Cs optical pumping magnetometer and 3-axis Helmholtz coils in nonmagnetic facilities. A multi-layer precision solenoid with the optimized single-current method generates the uniform magnetic field better than 1.0$\times$10$\^$-7/ within $\pm$ 1 cm region at its center. The coil constant of solenoid determined from Helium optical pumping magnetometer is 1.231 058 9 mT/A, and temperature coefficient is 0.38 nT/$\^{C}$. This standard system is used for calibration of low field magnetometers and testing relates to low field.

• Nuclear Engineering and Technology
• /
• v.52 no.3
• /
• pp.597-609
• /
• 2020

Accident Tolerant Fuels have been widely studied since the Fukushima-Daiichi accident in 2011 as one of the options on how to further enhance the safety of nuclear power plants. Deposition of protective coatings on nuclear fuel claddings has been considered as a near-term concept that will reduce the high-temperature oxidation rate and enhance accidental tolerance of the cladding while providing additional benefits during normal operation and transients. This study focuses on experimental testing of Zr-based alloys coated with Cr-based coatings using Physical Vapour Deposition. The results of long-term corrosion tests, as well as tests simulating postulated accidents, are presented. Zr-1%Nb alloy used as nuclear fuel cladding serves as a substrate and Cr, CrN, Cr_xN_y layers are deposited by unbalanced magnetron sputtering and reactive magnetron sputtering. The deposition procedures are optimized in order to improve coating properties. Coated as well as reference uncoated samples were experimentally tested. The presented results include standard long-term corrosion tests at 360℃ in WWER water chemistry, burst (creep) tests and mainly single and double-sided high-temperature steam oxidation tests between 1000 and 1400℃ related to postulated Loss-of-coolant accident and Design extension conditions. Coated and reference samples were characterized pre- and post-testing using mechanical testing (microhardness, ring compression test), Thermal Evolved Gas Analysis analysis (hydrogen, oxygen concentration), optical microscopy, scanning electron microscopy (EDS, WDS, EBSD) and X-ray diffraction.

• Microbiology and Biotechnology Letters
• /
• v.34 no.4
• /
• pp.357-362
• /
• 2006

A growth inhibition assay using Chlorella sp. AG 10002 based on the OECD 201 standard test procedure was applied to the toxicity testing of endosulfan and its reported metabolites. Comparison of dry cell weight, optical density (OD) at 680 nm, and chlorophyll a concentration indicated that optical density at 680 nm of culture broth is convenient, rapid, and accurate method for cell growth. In this microalgae system, the $IC_{50}$ values of endosulfan, endosulfan sulfate, endosulfan lactone, and endosulfan ether were determined as 9.45, 18.8, 18.2 and 37.5 mg/L, respectively. In a while, endosulfan diol did not show a significant toxicity up to 50 mg/L. Since endosulfan is liable at acidic or alkaline conditions, treatment of endosulfan in pH 3, 4, and 11 for 3 days resulted in reduced toxicity, as expected. These results suggested that the microalgae system is useful to evaluate various toxic chemicals and provide a new notion for bioremediation of endosulfan in aqueous systems.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.31 no.2
• /
• pp.150-156
• /
• 2011

In this paper, infrared thermography measurement technique has been used to develop standard measurement technique for nondestructive testing of composite materials which is widely used in aerospace industries. To increase the defect detection rate, the related experiment used the lock-in IR-thermographiy method. Therefore it is of considerable interest in the field of non-destructive testing for fast discontinuity detection by using ultrasonic lock-in infrared thermography. The result also shows that as the investigation period of light source is lengthened according to the thickness of specimen, the possibility of detecting defects gets higher as well. However, the reason why the result values were not favorable when less than 50 mHz of light source was provided is because it was difficult to detect defects as the defect parts became a state of thermal equilibrium in general when thermal diffusivity affects the entire materials.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.6 no.4
• /
• pp.331-336
• /
• 2005

Recently, Japan has showed strong demand for protection of consumers against misleading specification provided by producers, establishing the committee for JIS and ISO. To protect domestic market and overcome potential subordinate relationship in overseas market, several universities and institutes in Korea have performed collaborative works on the standardization of test method f3r photocatalytic activity concerning the selected application fields. This article deals with the process and the result for the method of testing photocatalytic sol or suspended powder using optical fiber. Currently, this method is Intended for TiO2, but can be applied for various photocatalytic raw materials that can be activated by visible light and solar irradiation.