• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.533-538
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• 2014

Power generator is one of the most important component of electricity generation system to convert mechanical energy to electrical energy. I t designed robustly to maintain high system reliability during operation time. But unexpected failure of the power generator could happen and it cause huge amount of economic and social loss. To keep it from unexpected failure, health prognostics should be carried out In this research, We developed a health prognostic method of stator windings in power generator with statistical data analysis and degradation modeling against water absorption. We divided whole 42 windings into two groups, absorption suspected group and normal group. We built a degradation model of absorption suspected winding using Fick's second law to predict upcoming absorption data. Through the analysis of data of normal group, we could figure out the distribution of data of normal windings. After that, we can properly predict absorption data of normal windings. With data prediction of two groups, we derived upcoming Directional Mahalanobis Distance (DMD) of absorption suspected winding and time vs DMD curve. Finally we drew the probability distribution of Remaining Useful Life of absorption suspected windings.

• Journal of the Korean Ceramic Society
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• v.16 no.1
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• pp.31-37
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• 1979

The middle point of composition within the system $MgO-Al_2O_3-SiO_2$ has been studied for applicability as ceramics dielectrics. A Kyul Sung Tale of high purity, magnesia clinker of Sam-wha chemical company, C.P. aluminium oxide, calcium carbonate, red lead, barium carbonate which was made into frit were used the raw materials. A number of steatite ceramics were prepared under carefully controlled condition and the water absorption, linear shrinkage, power factor, dielectric constant and dielectric loss were measured at elevated temperature. When we used magnesia clinker as flux, the quantity of this flux was 0.05mole, sintering temperature was continued for 2 hrs. at 1, 27$0^{\circ}C$. From this conditions, we could get the data whose power factor was 0.142%, water absorption was zero, linear shrinkage was 8.76%, dielectric constant was 5.63, dielectric loss was 0.00799. When we used red lead as flux, the quantity of this flux was 0.033mole and 0.066mole, sintering temperature was continued for 2hrs. at 1, 26$0^{\circ}C$. From this conditions, we could get the data whose water absorption was zero, linear shrinkage was 8.03%, and 8.48%, power factor was 0.136% and 0.062%, dielectric loss was 0.0072 and 0.0037. When we used barium carbonate made into frit as flux, the quantity of this flux was 0.02mole, sintering temperature was continued for 2hrs. at 1, 27$0^{\circ}C$. From this conditions, we could get the data whose water absoption was zero, linear shrinkage was 8.44%, power factor was 0.138%, dielectric constant was 5.69, dielectric loss was 0.0074.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.6
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• pp.42-50
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• 1993

In this paper the affect an inorganic filler and a f i n g up water absorption in epoxy composite material was represented. The results are summarized as follows ; 1. In the case of Sample 1, Sample 2 and a fillng up water absorption, the frequency depenence of E,' shows the straight characteristic underl4O0C. 2. Between lOOHz and 3kHz, the frequency dependency of tan8 is dominated by the loss of a dipole relaxation than the conductive loss for movement of a career. The effect of water absorption, is increased as the frequency is d e creased.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.2
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• pp.51-56
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• 1993

In this paper the affect an inorganic filler and a filling up water absorption in epoxy composite material was represented. The results are summarized as follows; 1. In the case of Sample 1, Sample 2 and a fillng up water absorption, the frequency depenence of ${\varepsilon}_\tau$ shows the straight characteristic under $140^{\circ}C$. 2. Between lOOHz and 3kHz, the frequency dependency of $tan{\delta}$ is dominated by the loss of a dipole relaxation than the conductive loss for movement of a career. The effect of water absorption, is increased as the frequency is decreased.

• Journal of Biomedical Engineering Research
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• v.16 no.1
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• pp.67-76
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• 1995

Explosive evaporative removal process of biological tissue by absorption of a CW laser has been simulated by using gelatin and a multimode Nd: YAG laser. Because the point of maximun temperature of laser-irradiated gelatin exists below the surface due to surface cooling, evaporation at the boiling temperature is made explosively from below the surface. The important parameters of this process are the conduction loss to laser power absorption (defined as the conduction-to-laser power parameter, Nk), the convection heat transfer at the surface to conduction loss (defined as Bi), dimensionless extinction coefficient (defined as BrJ, and dimensionless irradiation time (defined as Fo). Dependence of Fo on Nk and Bi has been observed by experiment, and the results have been compared with the numerical results obtained by solving a 2-dimensional conduction equation. Fo and explosion depth (from the surface to the point of maximun temperature) are increased when Nk and Bi are increased. To find out the minimum laser power for explosive evaporative removal process, steady state analysis has been also made. The limit of Nk to induce evaporative removal, which is proportional to the inverse of the laser power, has been obtained.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.4
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• pp.357-364
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• 2011

In this study, ring-shaped acoustic resonators were proposed to be installed in a silencer to increase the acoustic performance of silencer in the low-frequency range. Evaluation of noise reduction performance of acoustic resonator arrays was carried out by measuring the random-incidence absorption coefficient. It was found that the absorption coefficient of resonator array was measured up to 1 at 125 Hz of 1/3-octave band center frequency. Insertion losses of silencers with ring-shaped acoustic resonator arrays were measured based on ISO 7235. The results were shown that the ring-shaped resonator could increase the insertion loss up to 13 dB without flow, whereas 7 dB when flow speed reached 15 m/s. As increasing the flow speed above 15 m/s, the effect of acoustic resonator decreased due to the effect of nonlinear air damping of the resonator. It was also found that the increment of pressure drop by the presence of resonator arrays was about 9 % at flow speed of 25 m/s.

• Journal of the Korean Wood Science and Technology
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• v.32 no.6
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• pp.7-13
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• 2004

In this study, the Korean pine wood (Pinus densiflora Sieb. et Zucc) and Italian poplar wood (Populus euramericana Guinier) was treated with a mixture of monoammonium phosphate (MAP) and boric acid. Their usability as fire retardant and as decay-resistant construction and interior materials were evaluated by testing of chemicals, corrosion rate and absorption rate, weight loss and chemical contents. An experiment was performed to compare treated pine wood and Italian poplar wood. According to the results, Italian poplar wood had higher specific gravity and retention of chemicals than pine wood, and treated wood showed higher decay-resistance than untreated one. Weight loss was less in treated wood than untreated one because the degree of decay was lower in the former than the latter. Corrosion rate and absorption rate met the KS standard for wood preservative performance. The chemical contents analysis was carried out to determine the degree of decay and it was found that the preservative effect of chemical treatment was lower in Italian poplar wood than in pine wood.

• Journal of Biosystems Engineering
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• v.33 no.4
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• pp.224-229
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• 2008

This study was aimed to minimize the impact force and vibration transmitted to the transporting materials from the trailer and wheel shaft by installing the leaf spring suspension device at the space between the wheel shaft and frame of power tiller trailer. The developed trailer equipped with leaf spring suspension device was compared to the existing trailer without suspension device, in order to identify the vibration absorption effect of the leaf spring. The results of this study could be summarized as follows; (1) The length and the maximum bending amount of the leaf spring were designed as 1,000 mm and 42 mm, respectively, considering the possible space for installing at below the trailer. When 4 leaf springs were installed on both wheel shafts, the allowable maximum load was identified as 9,418 N. (2) The average vibration accelerations for the frequency less than 20 Hz, where the severe transporting loss could be represented, were $0.017\;m/s^2$ and $0.133\;m/s^2$ for the developed and the existing trailer, respectively, showing the vibration absorption effect of about 87%. And the average vibration accelerations on the driver's seat for the frequency less than 20 Hz were $0.01\;m/s^2$ and $0.20\;m/s^2$ for the developed and the existing trailer, respectively, which showed the similar vibration absorption effect. (3) The change of the average vibration accelerations for the frequency from 20 Hz to 80 Hz showed the similar tendency with the result for the frequency less than 20 Hz, but the effect for developed trailer was reduced slightly. And the effect of vibration absorption for the above 80 Hz was reduced highly. However, by installing the leaf spring suspension device at the trailer, the low frequency below 40 Hz, which could affect on transporting loss severely, could be reduced highly. (4) The maximum vibration acceleration for the frequency less than 20 Hz were $0.027\;m/s^2$ and $1.267\;m/s^2$ for the developed and the existing trailer, respectively. And the change of maximum acceleration between 20 Hz and 120 Hz was showed similar tendency with the result for the frequency less than 20 Hz, but the width of change was reduced highly.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.782-791
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• 1998

This paper presents a computer simulation of five types of triple effect absorption cycles employ-ing the refrigerant absorbent combinations of NH3/LiNO3 low-pressure type NH3/LiNO3+H2O/LiBr binary two-stage type series flow cycle and two types of parallel flow cycle for H2O/LiBr. The absorption systems is investigated through cycle simulation to obtain the system characteristics with the cooling water inlet temperature approach temperature of absorber loss temperature of absorber and chilled water outlet temperature. The most important characteristic temperature of absorber and chilled water outlet temperature. The most important characteristic of NH3/LiNO3 low-pressure type and a NH3/LINO3+H2O/LiBr binary two-stage type is that it obtains a coefficient of performance higher than the sum of the performance coefficients of its part operating independently. As a result of this analysis the optimum designs and operating conditions were determined based on the operating conditions and the coefficient of performance.

• Carbon letters
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• v.7 no.4
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• pp.245-248
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• 2006

Thin films of carbon-nano materials (CNMs) of different morphology have been successfully deposited on ceramic substrate by CVD at temperatures $800^{\circ}C$, $850^{\circ}C$ and $900^{\circ}C$ using plant based oils in the presence of transition metal catalysts (Ni, Co and Ni/Co alloys). Based on the return and insertion loss, microwave absorption properties of thin film of nanocarbon material are measured using passive micro-Strip line components. The result indicates that amongst CNMs synthesized from oil of natural precursors (mustered oil - Brassica napus, Karanja oil - Pongamia glabra, Cotton oil - Gossipium hirsuta and Neem oil - Azadirachta indica) carbon nano fibers obtained from neem's seed oil showed better microwave absorption (~20dB) in the range of 8.0 GHz to 17.90 GHz.