• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.29 no.2
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• pp.423-433
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• 1999

Purpose : To assess the methods for the clinical evaluation of the longitudinal bone changes after implantation of tooth ash-plaster mixture into the defect area of human jaws. Materials and methods : Tooth ash-plaster mixtures were implanted into the defects of 8 human jaws. 48 intraoral radiograms taken with copper step wedge as reference at soon, 1st, 2nd, 4th, and 6th week after implantation of mixture were used. X-ray taking was standardized by using Rinn XCP device customized directly to the individual dentition with resin bite block. The images inputted by Quick scanner were digitized and analyzed by NIH image program. Cu­equivalent values were measured at the implanted sites from the periodic digital images. Analysis was performed by the bidirectional subtraction with color enhancement and the surface plot of resliced contiguous image. The obtained results by the two methods were compared with Cu­equivalent value changes. Results : The average determination coefficient of Cu-equivalent equations was 0.9988 and the coefficient of variation of measured Cu values ranged from 0.08~0.10. The coefficient of variation of Cu-equivalent values measured at the areas of the mixture and the bone by the conversion equation ranged from 0.06 ~0.09. The analyzed results by the bidirectional subtraction with color enhancement were coincident with the changes of Cu-equivalent values. The surface plot of the resliced contiguous image showed the three dimensional view of the longitudinal bone changes on one image and also coincident with Cu-equivalent value changes after implantation. Conclusion : The bidirectional subtraction with color enhancement and the surface plot of the resliced contiguous image was very effective and reasonable to analyze clinically and qualitatively the longitudinal bone change. These methods are expected to be applicable to the non-destructive test in other fields.

• Journal of Korean Society of Steel Construction
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• v.16 no.4 s.71
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• pp.415-423
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• 2004

To investigate the long-term corrosion resistance of an uncoated weathering steel, an important outdoor constructional steel material, skyward surfaces of the weathering steel and a control steel initially exposed to rural and industrial atmospheres for 9 years were electrochemically tested in neutral artificial rain in terms of electrochemical potentials, impedances, and anodic potentiodynamic polarization curves. Their results were then discussed. A quite passive and stable rust layer to the artificial rain was well formed on the skyward surface of the weathering steel exposed to the industrial and rural atmospheres, and its corrosion rate in the artificial rain was measured to be about a low $3{{\mu}m}/y$. Continuous immersion of all the weathered surfaces in the artificial rain revealed the gradual degradation of the weathered corrosion layers on the steel, resulting in a cathodically controlled corrosion of the substrate steel by the electrochemical measurements. Alloy components of the weathering steel were found to retard the degradation of the weathered corrosion layers on the steel in the artificial rain. For better corrosion evaluation of the weathering steel, more electrochemical measurements of surfaces that have been exposed for more than 9 years to more closely simulated atmospheric waters are needed. These measurements are almost non-destructive and can provide online and in situ information on the corrosion rate, the development of corrosion and the conditions of rust layers on any interested surface and at any exposure time of the steel, so they can be effectively applicable to the corrosion evaluation of steel structures such as bridges, towers, and architectures by forming an electrochemical cell on an interested structural surface and by using a portable electrochemical instrument.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.4
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• pp.403-413
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• 2007

As rock bolts become one of the main support systems in tunnels and underground structures, the integrity of the rock bolts affects the safety of these types of structures. The purpose of this study is the evaluation of rock bolt integrity using Fourier and wavelet transforms of the guided ultrasonic waves. After five rock bolt specimens with various defect ratios are embedded into a large scale concrete block, guided waves are generated by a PZT (lead zirconate titanate) element and measured by an acoustic emission (AE) sensor. The captured signals are analyzed in the frequency domain using the Fourier transform, and in the time-frequency domain using the wavelet transform based on a Gabor wavelet. The spectrum obtained from the Fourier transform shows that a portion of high frequency contents increases with increase in the defect ratio. Peak values in the time-frequency domain represent the interval of travel time of each echo. The energy velocities of the guided waves increase with the defect ratio. This study shows that the spectrum ratio and the energy velocity may be indicators fur the evaluation of rock bolt integrity.

• Journal of the Korean Wood Science and Technology
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• v.34 no.1
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• pp.23-31
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• 2006

X-ray transit materials with straight path and the its intensity is proportional to the density of materials. Therefore, X-ray has been extensively used as a nondestructive evaluation (NDE) method in various fields. This study was carried out for development of a portable X-ray CT (computed-tomography) system to detect deteriorations of wood members in buildings. Based on the results of our previous study, a procedure of CT image reconstruction was established In order to verify the applicability of developed system, CT images of three wood disks were reconstructed by newly developed procedure and compared with the prototypes. From the results of this study, it was shown that the newly developed system could be used not only to determine the shape, size, and position of defects, but also to find the density distribution in cross section of wood structure members. The density distribution may be utilized to clarify the reason of wood deterioration and to provide the preventive method on how to treat or repair wood buildings. Because it was initial stage of system development, there were some limitations concerned with measuring equipment and image reconstruction algorithm. Especially, measuring time including equipment setup time was longer and measuring accuracy was lower than we expected. Therefore, we planned some additional studies on improvement of equipment and algorithm to enhance the capability of X-ray CT system.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.25-33
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• 2012

In electric power transmission tower structures on offshore, implementation of life management using the event data of regular safety inspections for structural and material damages is strongly recommended. In this study, six tower structures in Sihwa Lake around Yeoungheung island were target bodies for the safety inspections. safety inspections for deterioration about each of six towers were performed about three items for steel member, five items for concrete foundation, and four items for steel-pipe pile in seawater and seawater itself. Safety inspections for steel members included the visual observations of surface appearances, the measurements of member thicknesses, and the checks of painting states. Also safety inspections for concrete foundations comprised the estimation of crack features, the evaluation of non-destructive compression strengths, and the measurements of neutralization depths and chlorides contents. For steel-pipe piles in seawater the inspections comprised the surveys of corrosion states in accordance with potential levels tests and anode tests, the analyses of photos taken on surfaces of the piles as well as the evaluation of seawater quality. A set of deterioration inspections was performed at the same positions around october of each year for three consecutive years. As a result in this study, Newly developed deterioration indexes have been applied profitably to maintain structural safety for electric power transmission towers by utilizing these event data systematically.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.37-46
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• 2024

This study investigates the evolution of concrete damage due to chloride-induced steel corrosion through Impact-echo (IE) testing. Three reinforced concrete specimens, each measuring 1500 mm in length, 400 mm in width, and 200 mm in thickness, were fabricated using three concrete mixture proportions of blended cement types: ordinary Portland cement, ground granulated blast-furnace slag and fly ash. Steel corrosion in the concrete was accelerated by impressing a 0.5 A current following a 35-day cycle of wet-and-dry saturation in a 3% NaCl solution. Initial IE data collected during the saturation phase showed no significant changes, indicating that moisture had a minimal impact on IE signals and highlighting the slow progress of corrosion under natural conditions. Post-application of current, however, there was a noticeable decline in both IE peak frequency and the P-wave velocity in the concrete as the duration of the impressed current increased. Remarkably, progressive monitoring of IE proves highly effective in capturing the critical features of steel-corrosion induced concrete deterioration, such as the onset of internal damages and the rate of damage propagation. These results demonstrate the potential of progressive IE data monitoring to enhance the reliability of diagnosing and prognosticating the evolution of concrete damage in marine environment.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.4
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• pp.283-289
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• 2014

This study was conducted to develop a non-destructive detection method for adulterated powder products using Raman spectroscopy and partial least squares regression(PLSR). Garlic and ginger powder, which are used as natural seasoning and in health supplement foods, were selected for this experiment. Samples were adulterated with corn starch in concentrations of 5-35%. PLSR models for adulterated garlic and ginger powders were developed and their performances evaluated using cross validation. The $R^2_c$ and SEC of an optimal PLSR model were 0.99 and 2.16 for the garlic powder samples, and 0.99 and 0.84 for the ginger samples, respectively. The variable importance in projection (VIP) score is a useful and simple tool for the evaluation of the importance of each variable in a PLSR model. After the VIP scores were taken pre-selection, the Raman spectrum data was reduced by one third. New PLSR models, based on a reduced number of wavelengths selected by the VIP scores technique, gave good predictions for the adulterated garlic and ginger powder samples.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1522-1522
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• 2001

Beverages based on fruit juices are among the most popular commercially available drinks. There is an ever-increasing demand for these juices in the market. Orange juice is one of the most common as well as most favorite flavor. The fruit processing industries have a tremendous responsibility of quality control. For quality evaluation estimation of various components of the juice is necessary. Sucrose, glucose, fructose, citric acid and malic acid are the prime components of orange juice. Little information is available on analysis of orange juice. However, conventional and general wet chemistry procedures are currently being used which are no longer desired by the industry owing to the time involved, labor input and harmful chemicals required for each analysis. Need to replace these techniques with new, highly specific and automated sophisticated techniques viz. HPLC and spectroscopy has been realized since long time. Potential of Near Infrared Spectroscopy in quantitative analysis of different components of food samples has also been well established. A rapid, non-destructive and accurate technique based on Near Infrared Spectroscopy for determination of sugars and organic acids in orange juice will be highly useful. The current study is an investigation into the potential of Near Infrared Diffuse Reflectance Spectroscopy for rapid quantitative analysis of sucrose, glucose, fructose citric acid and malic acid in orange juice. All the Near Infrared measurements were peformed on a dispersive NIR spectrophotometer (ELICO 153) in diffuse reflectance mode. The spectral region from 1100 to 2500nm has been explored. The calibration has been performed on synthetic samples that are mixtures of sucrose, glucose, fructose, citric acid and malic acid in different concentration ranges typically encountered real orange juice. These synthetic samples are therefore considered to be representatives of natural juices. All the Near Infrared spectra of synthetic samples were subjected to mathematical analysis using Partial Least Square (PLS) algorithm. After the validation, calibration was applied to commercially available real samples and freshly squeezed natural juice samples. The actual concentrations were compared with those predicted from calibration curve. A good correlation is obtained between actual and predicted values as indicated by correlation coefficient ($R^2$) value, which is close to unity, showing the feasibility of the technique.

• Journal of Korean Society of Steel Construction
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• v.18 no.4
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• pp.503-514
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• 2006

FBG sensors are capable of measuring the strain of structures easily and more durably than electric resistance gauges. Thus, many researches are dedicated to the application for the response monitoring or non-destructive evaluation of structures using FBG sensors. Additionally, the measured strains at the top and bottom of a cross-section can be transformed into the curvature of the section, which can be used to calculate its vertical displacement. Hence, this study aims to measure the dynamic strain signals of a steel section simply supported beam and to estimate the dynamic displacement from the strain signals, after which the estimated displacement is com pared with the measured displacement. The dynamic characteristics (natural frequency, damping ratio and mode shape) of the beam are predicted from both the estimated and measured displacement signals, and from the strain time history of the FBG sensors. The predicted properties are compared with those of an analytical model of the beam. The estimated displacement. However, the predicted dynamic properties from both the estimated displacements and the measured strains are well-correlated with those from the measured displacement. It is therefore appreciated that the estimation of the dynamic properties of FBG sensor signals is reasonable. Especially, the strain signal of the FBG sensor was amplified at a higher-frequency region in comparison with the displacement estimation with higher-mode properties.

• Journal of the Mineralogical Society of Korea
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• v.32 no.4
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• pp.287-301
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• 2019

Preservation of the original form is the principle for conservation, management and utilization of cultural heritages. Thus, non-destructive analysis of these samples are important field of the conservation science. In this study, examined the applicability of nondestructive surface X-ray diffraction analysis (ND-XRD) for cultural heritage by materials (rock specimen, jade stone, pigment painted specimen, earthen artifact, metal artifact). In result, all type of sample is recorded suitable X-ray diffraction patterns for identifying mineral composition in case of surface condition with adequate particle size and arrangement. And diffraction pattern is reflected surface information than matrix. Therefore, ND-XRD is thought to be applicable not only mineral identification but also interpretation of manufacturing technique and alteration trend about layered sample (in horizontally or vertically). Whereas some exceptional diffraction patterns were recorded due to overlapping information on specific crystal planes. It caused by skip the sample treatment (powdering and randomly orientation). It could be advantageously used for mineral identification, such as preferred orientation of clay minerals. In contrast, irregular diffraction pattern caused by single crystalline effect is required careful evaluation.