• Phonetics and Speech Sciences
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• v.7 no.1
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• pp.39-45
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• 2015

Changes in speech production in normal elderly might be subtle and gradual. Therefore, an acoustic analysis is appropriate to identify the effect of aging on speech. For this purpose, this study examined four speech parameters; voice onset time (VOT), VOT range, $f_0$ of following vowel($f_0FV$), and $f_0FV$ difference in two age groups, old (mean age 74.57 yrs.) and young (m: 27.43 yrs.). The results show that compared to the older group the younger demonstrated significantly shorter VOTs in lenis and longer in aspirated stop. VOT ranges were relatively broad and consequently overlapped between the phonation types (e.g., lenis, fortis, aspirated). The $f_0FV$ values in the older group which are an integral parameter with VOT were lower compared with the young group. The $f_0FV$ differences in the old female group were significantly narrower than the young female group, therefore, clear distinction became difficult. In conclusion, contrast in temporal information was obscured, and the domain of glottal information was diminished on stop consonants in Korean elderly. The findings suggest that central/peripheral changes by aging could lead to a deficit in coordination between phonation and articulation.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.10-17
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• 2007

Design of experiments (DOE) technique has been used to design an exhaust heat exchanger to reduce the exhaust gas temperature under high load conditions in a spark-ignition engine. The DOE evaluates the influence and the interaction of a selected eight design parameters of the heat exchanger affecting the cooling performance of the exhaust gas through a limited number of experiments. The heat exchanger was installed between the exhaust manifold and the inlet of the close-coupled catalytic converter (CCC) to reduce thermal aging. To maximize the heat transfer between exhaust gas and coolant, fins were implemented at the inner surface of the heat exchanger. The design parameters consist of the fin geometry (length, thickness, arrangement, and number of fin), coolant direction, heat exchanger wall thickness, and the length of the heat exchanger. The acceptable range of each design parameter is discussed by analyzing the DOE results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.4
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• pp.427-434
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• 2004

Ferritic stainless steel is recently used in high temperature structures because of its good properties of thermal fatigue resistance, corrosion resistance, and low price. Tensile and low-cycle fatigue (LCF) tests on 429EM stainless steel used in exhaust manifold were performed at several temperatures from room temperature to 80$0^{\circ}C$. Elastic Modulus, yield strength, and ultimate tensile strength monotonically decreased when temperature increased. Cyclic hardening occurred considerably during the most part of the fatigue life. Dynamic strain aging was observed in 200~50$0^{\circ}C$, which affects the cyclic hardening behavior. Among the fatigue parameters such as plastic strain amplitude, stress amplitude, and plastic strain energy density (PSED), PSED was a proper fatigue parameter since it maintained at a constant value during LCF deformation even though cyclic hardening occurs considerably. A phenomenological life prediction model using PSED was proposed considering the influence of temperature on fatigue life.

• Journal of IKEEE
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• v.11 no.3
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• pp.108-116
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• 2007

This paper proposed an analyzable parameter and its analytic method to provide more accurate information than currently employed 4 channels system which uses pulse wave velocity (PWV) information of the volume pulse wave measured from 4 arterial channels for the characterization of arterial vessel. In order to verify the volume pulse waves on 4 sites were simultaneously acquired subjects aged from 12 to 81 years old. and the proposed parameters were extracted from time (UT) was then compared with blood pressure. Then, the regression analyses were done relationships among the proposed parameter and others, such as aging, pulse transit time pressure (BP). The followings are the results of linear regression analysis of the proposed parameter for total 50 normal subjects. We selected any two subjects (58 years and 27 years) and measured PPG (photoplethysmogram) and BP of before and after exercise. The coefficient of correlations between BP and UT observed was -0.928 for 50 years subject, and -0.922 for 20 years subject. For total 50 normal subjects, in case of correlation between the pulse transit time and BP, the result showed -0.170 on left side and -0.233 on right side, and the coefficient value of correlation between the pulse transit time and UT was -0.607 on left side and -0.510 on right side. UI is strongly correlated with the pulse transit time than BP. Hence, we believe that the proposed parameter is related with the index of arterial stiffness.

• The Korean Journal of Food And Nutrition
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• v.22 no.4
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• pp.548-553
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• 2009

Qualitative properties- polyphenol compounds(total phenolics, anthocyanin, flavonoids, tannins), color parameters and antioxidant activities- of wild grape wine having different aging periods were studied. The contents of total phenolics and anthocyanin decreased significantly in accordance with aging terms(p<0.05). The total phenolics and anthocyanin of the oldest wine(WG3) represented only 43% and 45% of it's related compound in the wine aged for one year(WG1), respectively. The contents and the degree of polymerization of tannins, including condensed tannins, also decreased but not showed statistically significant. However, The contents of flavonoids of the 2 year old wine(WG2) decreased significantly related to that of WG1, remaining, then, almost constant at that levels during aging. The L* values, b(yellow) values and the hue (hab) values were increased in long aged wines(WG2, WG3), while the intensity of color(CI) and, the a(red) parameter value decreased. The antiradical activity of wild grape wines was shown to be high(87 EDA%) in WG1. The corresponding coefficient of tannin concentrations with antiradical activity($r^2$=0.9189) suggests that the tannin content may be strongly related to the antioxidant properties of wild grape wines.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.4
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• pp.439-445
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• 2001

The destructive method is reliable and widely used lot the estimation of material degradation but, it have time-consuming and a great difficulty in preparing specimens from in-service industrial facilities. Therefore, the estimation of degraded structural materials used at high temperature by nondestructive evaluation such as electric resistance method, replica method, Barkhausen noise method, electro-chemical method and ultrasonic method are strongly desired. Ultrasonic nondestructive evaluation technique has been reported good to attain efficiency of measurement, high sensitivity of measurement, and rapidity and reliability of result interpretation. In this study, it was verified experimentally the feasibility of the evaluation of degraded 2.25Cr-1Mo steel specimens which were prepared by the isothermal aging heat treatment at $630^{\circ}C$ by high frequency longitudinal wave method investigating the change of attenuation coefficient by FFT analysis and wavelet transform. Because of carbide precipitation increase and spheroidization near grain boundary of microstructure to aging degradation, attenuation coefficient had a tendency to increase as degradation proceeded. It was identified possibly to evaluate degradation using the characteristics of high-frequency ultrasonics. Frequency dependence of ultrasonic attenuation coefficient to aging degradation appeared large, which made sure that attenuation coefficient is an important parameter for evaluation of aging degradation.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.4
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• pp.151-159
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• 2001

As huge energy transfer systems like a nuclear power plant, steam power plant and petrochemical plant are operated for a long time, mechanical properties are changed by degradation. The life time of the systems can be affected by the mechanical properties. BI(Ball Indentation) test has a potential to replace conventional fracture tests like a uniaxial tensile test, fracture toughness test, hardness test and so on. In this paper, we would like to present the ageing evaluation technique by the BI method. The four classes of the thermally aged 1Cr-!mo-0.25V specimens were prepared using an artificially accelerated aging method. Tensile tests, fracture toughness tests, hardness tests and BI tests were performed. The results of the BI tests were in good agreement with fracture characteristics by a standard fracture test method within 5%. The IDE(Indentation Deformation Energy) of a BI technique as a new parameter for evaluating a degradation was suggested and the new IDE parameter clearly depicts the degradation degree.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1631-1635
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• 2002

In order to be good display, the ac PDP lifetime should be guaranteed over 30000 hours. Therefore, to satisfy these demands, it is need to find out main factors in ac PDP affecting the lifetime. In this paper, the characteristics of lifetime as a parameter of the MgO deposition rate conditions is investigated. MgO protective layers is fabricated by E-beam. Before measuring the lifetime we have carefully peformed high temperature evacuation and aging procedure, which is essential for providing the initial condition of our experiment. If MgO deposition rate increased, MgO film becomes dense and an adhesive power of MgO film gets better and because occurrence rate of the MgO cluster decreases, lifetime of MgO will be improved. As a result, ac PDP lifetime can be improved due to the improvement of MgO by MgO preparation conditions.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.70-72
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• 2019

For the safe and reliable operation of Lithium-ion batteries in Electric Vehicles (EVs) or Energy Storage Systems (ESSs), it is essential to have accurate information of the battery such as State of Charge (SOC). Many kinds of different techniques to estimate the SOC of the batteries have been developed so far such as the Kalman Filter. However, when it is applied to the multiple number of batteries it is difficult to maintain the accuracy of the estimation over all cells due to the difference in parameter value of each cell. Moreover the difference in the parameter of each cell may become larger as the operation time accumulates due to aging. In this paper a novel Deep Neural Network (DNN) based SOC estimation method for multi cell application is proposed. In the proposed method DNN is implemented to learn non-linear relationship of the voltage and current of the lithium-ion battery at different SOCs and different temperatures. In the training the voltage and current data of the Lithium battery at charge and discharge cycles obtained at different temperatures are used. After the comprehensive training with the data obtained with a cell resulting estimation algorithm is applied to the other cells. The experimental results show that the Mean Absolute Error (MAE) of the estimation is 0.56% at 25℃, and 3.16% at 60℃ with the proposed SOC estimation algorithm.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1614-1616
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• 1999

Epoxy resin has been used as matrix resin of advanced composites owing to ideally suitable properties and inherent physical and chemical properties for electrical and electronic insulation. In this paper, in order to evaluate the performance of epoxy composites for out door insulation, variations of tracking resistance were investigated on the complex ageing parameter. Also, IPN methods were introduced in order to improve performance for out door use. As a result, it was confirmed that tracking resistance were degraded with complex ageing parameters. But, it was confirmed that specimen of IPN structure have the better tracking resistance properties than SIN structure by moisture absorption aging.