• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.6
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• pp.436-441
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• 1998

$Pt/SrTiO_3/Pb_x(Zr_{0.52}, Ti_{0.48})O_3/SrTiO_3/Si$ structure was prepared by rf-magnetron sputtering method for use in nondestructive read out ferroelectric RAM(NDRO-FEAM). PBx(Zr_{0.52}Ti_{0.48})O_3}$(PZT) and $SrTiO_3$(STO) films were deposited respectively at the temperatures of $300^{\circ}C and 500^{\circ}C$on p-Si(100) substrate. The role of the STO film as a buffer layer between the PZT film and the Si substrate was studied using X-ray diffraction (XRD), Auger electron spectroscopy (ASE), and scanning electron microscope(SEM). Structural analysis on the interfaces was carried out using a cross sectional transmission electron microscope(TEM). For PZT/Si structure, mostly Pb deficient pyrochlore phase was formed due to the serious diffusion of Pb into the Si substrate. On the other hand, for STO/PZT/STO/Si structure, the PZT film had perovskite phase and larger grain size with a little Pb interdiffusion. the interfaces of the PZT and the STO film, of the STO film and the interface layer and $SiO_2$, and of the $SiO_2$ and the Si substate had a good flatness. Across sectional TEM image showed the existence of an amorphous layer and $SiO_2$ with 7nm thickness between the STO film and the Si substrate. The electrical properties of MIFIS structure was characterized by C-V and I-V measurements. By 1MHz C-V characteristics Pt/STO(25nm)/PZT(160nm)/STO(25nm)/Si structure, memory window was about 1.2 V for and applied voltage of 5 V. Memory window increased by increasing the applied voltage and maximum voltage of memory window was 2 V for V applied. Memory window decreased by decreasing PZT film thickness to 110nm. Typical leakage current was abour $10{-8}$ A/cm for an applied voltage of 5 V.

• International Journal of Highway Engineering
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• v.9 no.2 s.32
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• pp.101-114
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• 2007

Dowel bars in the jointed concrete pavement are used to both provide load transfer across pavements joints and prevent the joint faulting leading to longer service life. On the contrary, the misplacement of dowel bar can provide negative results including the joint freezing(locking) that may cause the joint spatting and unexpected mid-slab cracking. The dowel bar can be placed using the assembly or dowel bar inserter (DBI) during the concrete pavement construction. In the domestic practice of the concrete pavement construction, the dowel bar is placed using the assembly method. This study primarily focuses on the comparison of these two dowel placement methods using the field data from the KHC test road in which both dowel placement methods have been applied to a certain length of the concrete pavement. The field data regarding the alignment of the dowel bars placed by both methods was collected using MIT-SCAN2, a nondestructive measuring equipment, and processed to compute Joint Score and Running Ave. Joint Score which are used as indicators of the dowel bar performance. The comparison of the methods for the dowel bar placement using these indicators shows that the DBI method provided much better alignment of the dowel bars reducing the risk of joint freezing than the assembly method. In order to improve the quality of the dowel bar placement using the assembly method, the current weak points of the assembly method including the fabrication, storage, and installation of dowel bar assembly were investigated and the solution was suggested. The improved dowel bar sets based on the suggested solution have been applied to an actual practice of the concrete pavement construction. The field data shows that the improved assembly method suggested in this study can highly reduce the risk of joint freezing.

• Journal of the Korean Wood Science and Technology
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• v.43 no.3
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• pp.304-310
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• 2015

The moisture content of sawdust must be measured accurately and controlled appropriately during storage and transportation because biological degradation could be caused by improper moisture. In this study, to measure the moisture contents of Larix kaempferi sawdust, the near-infrared reflectance spectra (Wavelength 1000-2400 nm) of sawdust were used as detection parameter. After acquiring the NIR reflection spectrum of specimens which were humidified at each relative humidity condition ($25^{\circ}C$, RH 30~99%), moisture content prediction model was developed using mathematical preprocessings (e.g. smoothing, standard normal variate) and partial least squares (PLS) analysis with the acquired spectrum data. High reliability of the MC regression model with NIR spectroscopy was verified by cross validation test ($R^2$ = 0.94, RMSEP = 1.544). The results of this study show that NIR spectroscopy could be used as a convenient and accurate method for the nondestructive determination of moisture content of sawdust, which could lead to optimize wood utilization.

• Journal of Korea Foresty Energy
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• v.25 no.2
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• pp.1-8
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• 2006

The physical, mechanical and chemical properties of old and new Korean red pine (Pinus densiflora) were analyzed. The old woods were from dismantled timbers of Bonjungsa temple. The crystallized resin in the latewood was observed by microscopic analysis. Also, reduction of specific gravity, occurrence of microscopic cleavage of tracheid was observed in the old wood. The angle of microscopic cleavage of tracheid is estimated with the same angle of micro-fibril angle of 52 layer. The bending, compression and shear strength of old world were decreased about 35-27% than those of new wood. Dynamic modulus of elasticity measured by ultrasonic nondestructive test has the tendency of reducing by the time elapse of the wood usage. Therefore, deterioration of wood could be measured by reduction of specific gravity and dynamic MOE. The static MOE and mechanical properties of old wood could be predictable by measuring dynamic MOE in the longitudinal direction. Extractives of the old wood in 1-% NaOH solution are larger quantity than new wood. Therefore the decay of the wood could be evaluated by analyzing the chemical compound, especially 1-% NaOH solution. The results of this research could be used for understanding and prediction of the changing properties with elapsing time of wood.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.164-172
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• 2020

The fuel oil/heat exchanger installed in military aircraft is a device that cools the lubricant oil supplied to other devices, such as an AMAD, and a hydraulic pump using the low temperature of the fuel is cracked at the AMAD lubricant inlet port. If a crack in the heat exchanger occurs, the lubricant oil supplied to other equipment is not cooled. Therefore, the flight can no longer be performed. In this study, non-destructive inspection and microscopic examination of the fracture surface of the oil port were performed to analyze the crack tendency. The oil pipe connected to the oil port is a titanium pipe, which is fastened with over torque and has been identified as the leading cause of heat exchanger oil port cracks. In addition, it was verified as the main reason for cracking by finite element analysis. The material and diameter of the pipe were changed to improve this defect, and the applied torque was adjusted. In addition, the bending value of the pipe was adjusted to minimize the fatigue accumulation due to pulsating pressure. As a result, no cracks occurred on the heat exchanger via the ground test after the installation of an improved pipe under the same conditions.

• Journal of Sensor Science and Technology
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• v.9 no.6
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• pp.404-415
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• 2000

This paper describes several performances and nondestructive inspection for deterioration due to forest fires in overhead transmission lines. After discussing corrosion mechanism such as atmospheric and galvanic corrosion for aged ACSR conductors and its detection for them are presented. Through impedance analysis of a solenoid coil, it is shown that the eddy current sensor may be available to inspect severe fault or local corrosion. As the solenoid coil changes its impedance when the test conductor is inserted into the coil, it can be possible to measure deterioration degree caused by forest fires. Tensile strength, extension rate and sensor impedance are tested for some samples degraded by artificial fire. As increasing blazed period to some extent, the strength of aluminum strand begins to be reduced remarkably, while galvanized steel strand holds the similar strength to the initial value, despite of appearing a little loss of zinc layer. In general, it is shown that the sensor impedance would be increased while the tension load of conductor is reduced and the extension rate is contrarily increased. Therefore, the sensor output could exhibit the changes of mechanical performances, and would be used to detect such deterioration caused by forest fire in ACSR conductors built on the ridge of mountains. Finally, it was verified that the solenoid coil could be applicable to obtain any crucial inform for serious deterioration due to forest fires.

• Economic and Environmental Geology
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• v.50 no.6
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• pp.497-508
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• 2017

This study was carried out to document and diagnose the conditions of the seated stone statue of Buddhist Master Seungga in Seunggasa temple immediately after its conservation treatment, which was found to be long covered in surface of white materials. The stone Halo was researched along with the Statue, and basic data was secured through precisely examination and nondestructive diagnosis. The result from the surface deterioration evaluation shows that both the Statue and Halo had a little bit of physical deterioration, although their level of chemical deterioration was proportionally higher due to discoloration. The physical property diagnosis using ultrasonic measurements on the Statue and Halo showed that the average ultrasonic velocity was found to be 3,570 m/s and 3,373 m/s, respectively, which corresponds to grade III, an indication of a favorable physical property. The surface covered materials were detected to be Ca, Ti, Pb, Fe, Al and Si, emanating from Hobun (Oster shell powder; $CaCO_3$) or lime ($CaO{\cdot}Ca(OH)_2$) and silicate minerals. Furthermore, Ti and Pb seems to be the component of the white coloring pigments, titanium white ($TiO_2$) and white lead ($2PbCO_2{\cdot}Pb(OH)_2$). Therefore, the seated stone statue of Buddhist Master Seungga is presumed to be painted with Hobun or lime and thereafter painted over with titanium white and white lead.

• Proceedings of the Korean Geotechical Society Conference
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• 1995.10a
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• pp.15.2-22
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• 1995

Evaluating stiffness of near-surface materials has been one of the critically important tasks in many civil engineering works. It is the main goal of geotechnical characterization. The so-called deflection-response method evaluates the stiffness by measuring stress-strain behavior of the materials caused by static or dynamic load. This method, however, evaluates the overall stiffness and the stiffness variation with depth cannot be obtained. Furthermore, evaluation of a large-area geotechnical site by this method can be time-consuming, expensive, and damaging to many surface points of the site. Wave-propagation method, on the other hand, measures seismic velocities at different depths and stiffness profile (stiffness change with depth) can be obtained from the measured velocity data. The stiffness profile is often expressed by shear-wave (S-wave) velocity change with depth because S-wave velocity is proportional to the shear modulus. that is a direct indicator of stiffiiess. The crosshole and downhole method measures the seismic velocity by placing sources and receivers (geophones) at different depths in a borehole. Requirement of borehole installation makes this method also time-consuming, expensive, and damaging to the sites. Spectral-Analysis-of-Surface-Waves (SASW) method places both source and receivers at the surface, and records horizontally-propagating surface waves. Based upon the theory of surfacewave dispersion, the seismic velocities at different depths are calculated by analyzing the recorded surface-wave data. This method can be nondestructive to the sites. However, because only two receivers are used, the method requires multiple measurements with different field setups and, therefore, the method often becomes time-consuming and labor-intensive. Furthermore. the inclusion of noise wavefields cannot be handled properly, and this may cause the results by this method inaccurate. When multi-channel recording method is employed during the measurement of surface-waves, there are several benefits. First, usually single measurement is enough because multiple number (twelve or more) of receivers are used. Second, noise inclusion can be detected by coherency checking on the multi-channel data and handled properly so that it does not decrease the accuracy of the result. Third, various kinds of multi-channel processing techniques can be applied to f1lter unwanted noise wavefields and also to analyze the surface-wavefields more accurately and efficiently. In this way, the accuracy of the result by the method can be significantly improved. Fourth, the entire system of source, receivers, and recording-processing device can be tied into one unit, and the unit can be pulled by a small vehicle, making the survey speed very fast. In all these senses, multi-channel recording of surface waves is best suited for a routine method for geotechnical characterization in most of civil engineering works.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.29-42
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• 1999

The SASW (Spectral-Analysis-of-Surface-Waves) method, which evaluates the stiffness structure of the subsurface and structures nonintrusively and nondestructively, has been successfully used in the civil engineering applications. However, the SASW method assumes that the subsurface or structures consist of horizontal multi-layers, so that the method has some difficulty in continuously evaluating the integrity of a tunnel lining and a pavement system. This difficulty prevents the SASW method from being used to generate a tomographic image of stiffness for the subsurface or structures. Recently, the GPR technique which has the advantage of continuously evaluating integrity of the subsurface and structures has been popular. This advantage of GPR technique initiated the efforts to make the SASW method, which is superior to GPR and other nondestructive testing methods due to its capability of evaluating stiffness and modulus, be able to do continuous evaluation of stiffness structure, and the efforts finally lead to the development of \ulcornerTomographic SASW Technique.\ulcorner Tomographic SASW technique is a variation of the SASW method, and can generate a tomographic image of stiffness structure along the measurement line. The tomographic SASW technique was applied to the investigation of lateral variability of a sand box placed by the raining method for the purpose of verifying its effectiveness. Tomographic SASW measurements on the sand box revealed that the investigated sand box has different shear stiffness along the measurement line, which gave a clue of how to make a better raining device.

• Nuclear Engineering and Technology
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• v.49 no.5
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• pp.1044-1062
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• 2017

The construction project of the Kijang research reactor (KJRR), which is the second research reactor in Korea, has been launched. The KJRR was designed to use, for the first time, U-Mo fuel. Plate-type U-7 wt.% Mo/Al-5 wt.% Si, referred to as U-7Mo/Ale5Si, dispersion fuel with a uranium loading of $8.0gU/cm^3$, was selected to achieve higher fuel efficiency and performance than are possible when using $U_3Si_2/Al$ dispersion fuel. To qualify the U-Mo fuel in terms of plate geometry, the first miniplates [HANARO Miniplate (HAMP-1)], containing U-7Mo/Al-5Si dispersion fuel ($8gU/cm^3$), were fabricated at the Korea Atomic Energy Research Institute and recently irradiated at HANARO. The PIE (Post-irradiation Examination) results of the HAMP-1 irradiation test were analyzed in depth in order to verify the safe in-pile performance of the U-7Mo/Al-5Si dispersion fuel under the KJRR irradiation conditions. Nondestructive analyses included visual inspection, gamma spectrometric mapping, and two-dimensional measurements of the plate thickness and oxide thickness. Destructive PIE work was also carried out, focusing on characterization of the microstructural behavior using optical microscopy and scanning electron microscopy. Electron probe microanalysis was also used to measure the elemental concentrations in the interaction layer formed between the U-Mo kernels and the matrix. A blistering threshold test and a bending test were performed on the irradiated HAMP-1 miniplates that were saved from the destructive tests. Swelling evaluation of the U-Mo fuel was also conducted using two methods: plate thickness measurement and meat thickness measurement.