• Proceedings of the Korean Fiber Society Conference
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• 1993.06a
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• pp.14-15
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• 1993

• Proceedings of the Korean Fiber Society Conference
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• 1993.06a
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• pp.20-21
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• 1993

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.113-116
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• 2006

In order to fully utilize the inherent precision that GPS observables could offer, accurate estimation of dynamic and measurement parameters is vital. Among these parameters some are indispensable in virtually every form of GPS processing, while some are limitedly relevant to a particular application. In the context of time transfer by GPS, the transmission-related errors such as ionospheric and tropospheric delays, and the integer ambiguity of the carrier phase observables belong to the former, the atomic clock parameters and data batch-related parameters to the latter. Obviously the atomic clock parameters are of prime importance in GPS time transfer. In this study some of important parameters in conducting time transfer experiments by use of GPS were characterized and their effects on time transfer performance were investigated in detail

• Journal of the Korean Society for Nondestructive Testing
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• v.15 no.1
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• pp.277-290
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• 1995

The study was carried out to analyze the fracture behavior and the acoustic emission(AE) characteristics and to find the relationship among tensile strength, fracture toughness and cure pressure in owe process of the carbon fiber reinforced composites of two types, $[0^{\circ}/90^{\circ}]_{2S}$ and $[0^{\circ}\;_2/90^{\circ}\;_2]_S$. AE signals were detected during the curing process, tensile tests and fracture toughness tests by acoustic emission(AE) measurements, respectively. Tensile strengths showed that the less cure pressurizing steps and the side of $[0^{\circ}/90^{\circ}]_{2S}$ specimens had the higher strengths than those of the others. Fracture toughness by the change of test temperature showed nearly same values in the same temperature region, but the higher test temperature had the lower fracture toughness values. In order to examine the relationship between fracture behavior of CFRP in tensile and fracture toughness tests and AE signals, the post processing for AE parameters of AE data and the observations of microscope and SEM have been carried out respectively.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.3
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• pp.469-477
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• 2002

One of the major deficiencies of composite restorative resins is their insufficient resistance to wear. Of the multitude of factors that have been associated with wear, subsurface degradation within the restoration is considered to be one. The aim of this study was to evaluate the resistance to degradation of four commercial composite resins in an alkaline solution. The brands studied were Z100(3M), Clearfil AP-X(Kuraray), Tetric Ceram(Vivadent), Aelit flo(Bisco). Resistance to degradation was evaluated on the basis of the following parameters: (a) mass loss(%) - determined from pre-and post-exposure specimen weights: (b) Si loss(ppm) - obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation depth(${\mu}m$) - measured microscopically (SEM) from polished circular sections of exposed specimens. The results were as follows: 1. The sequence of the mass loss was in ascending order by AE, EL, TC, Z100. There was statistically significant difference of mass loss between AE, CL group and TC, Z100 group(p<0.05). 2. The sequence of the degree of degradation layer depth was in ascending order by AE, CL, TC, Z100. But there was no statistically significant difference of degree of degradation layer depth between AE and CL(p<0.05). 3. For the Si concentration, Z100 was the highest of all. 4. The correlation coefficient between mass loss and degradation depth was relatively high(r=0.71 p<0.05).

• Journal of the Korean Society of Physical Medicine
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• v.9 no.1
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• pp.83-91
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• 2014

PURPOSE: The purpose of this study was to investigate the effects of task oriented circuit exercise(TOCE) on the balance and cognition in mild dementia patients. METHODS: The subjects of the study were 30 patients with mild dementia and assigned to the TOCE(task oriented circuit exercise) group(n=15) and aerobic exercise(AE) group(n=15). TOCE group performed six task three times weekly for 12 weeks. AE group underwent the cycle ergometer and treadmill exercise three times a week during the experimental period respectively. Timed up and go test(TUG), Berg balance scale(BBS) and AP1153 Biorescue were used to assess the parameters for the balance. Korean-mini mental state examination and Global deterioration scale(GDS) were used to assess the parameters for the cognition. For the statistical analysis, paired t-test and independent t-test were used to compare the differences among two groups. RESULTS: Each group showed improvement in balance and possibility for improving cognitive function. TOCE group especially, there were significant improvements in limit of stability. CONCLUSION: The results of the study suggest that TOCE is a more diverse exercise programs introduced in the study. Furthermore, TOCE can be a helpful to improve the balance and cognition in mild dementia patients.

• Composites Research
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• v.36 no.6
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• pp.429-434
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• 2023

In this study, aimed at improving the existing acoustic emission sensor for real time monitoring, a macro-fiber composite (MFC) transducer was employed as the acoustic emission sensor in the gas leak detection system. Prior to implementation, structural analysis was conducted to optimize the MFC's design. Consequently, the flexibility of the MFC facilitated excellent adherence to curved pipes, enabling the reception of acoustic emission (AE) signals without complications. Analysis of AE signals revealed substantial variations in parameter values for both high-pressure and low-pressure leaks. Notably, in the parameters of the Fast Fourier Transform (FFT) graph, the change amounted to 120% to 626% for high-pressure leaks compared to the case without leaks, and approximately 9% to 22% for low-pressure leaks. Furthermore, depending on the distance from the leak site, the magnitude of change in parameters tended to decrease as the distance increased. As the results, in the future, not only will it be possible to detect a leak by detecting the amount of parameter change in the future, but it will also be possible to identify the location of the leak from the amount of change.

• Phonetics and Speech Sciences
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• v.1 no.3
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• pp.133-144
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• 2009

Pharyngeal flap surgery changes the space and shape of the oral cavity and vocal tract, and these changing conditions bring resonance change. The purpose of this study was to determine the most reliable and valuable parameters for evaluating hypernasality to distinguish two patients before and after pharyngeal flap surgery. Each patient was asked to clearly speak the vowels /a/, /i/, /u/, /e/, /o/ for voice recording. There were nine parameters: Formant (F1, F2, F3), Bandwidth (BW1, BW2, BW3), LPC energy slope ($\Delta$ |A2-A1/F2-F1|), and Band Energy (0-500 Hz, 500-1000 Hz) by each vowel. From the results of discrimination analyses on acoustic parameters, the vowels /a/, /e/ appeared to be insignificant but vowels /i/, /u/, /o/ appeared to be efficient in the separation. A 95%, 100%, and 100% recognition score could be reached when vowels /i/, /u/, and /o/ were analyzed. The results showed that F2, BW3, and LPC slope are more important parameters than the others. Finally, there is a relation between perceptual evaluation score and LPC energy slope of acoustic parameters by least square slope.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.5
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• pp.104-113
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• 2006

The main objective of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals and doing a source location for weld heat affected zone (HAZ) through tensile testing. This study was carried out an SWS 490A high strength steel for electric shield metal arc welding, SMAW; $CO_2$ gas metal arc welding, GMAW($CO_2$); and gas tungsten arc welding, GTAW/TIG. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. For instance, Gutenberg-Richter magnitude-frequency relationship (G-R MFR) offers useful b-value in data analysis. Namely event identification, source location gives the X- and Y-coordinates of the AE source. And K-means clustering analysis by Euclidean distance confirmed that was powerful to source location. Generally, strength of welded metal zone was stronger than strength of base metal. As the result, confirmed certainly that fracture is produced in HAZ instead of welded metal zone from source location.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.28-31
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• 1999

Carbon fiber/epoxy composites using electrodeposited monomeric and polymeric coupling agents were compared with the dipping and the untreated cases. Treating conditions such as time, concentration and temperature were optimized. Four-fibers embedded micro-composites were prepared for fragmentation test. Interfacial properties of four-fiber composites with different surface treatments were investigated with simultaneous acoustic emission (AE) monitoring. The microfailure mechanisms occurring from fiber break, matrix and interlayer crackings were examined by AE parameters and an optical microscope. It was found that interfacial shear strength (IFSS) of electrodeposited carbon fibers was much higher than the other cases under dry and wet conditions. Well separated and different-shaped AE groups occurs for the untreated and ED treated case, respectively.