• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.106-107
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• 2003

The interest of THz technology has been growing fast due to the potential of its vast applications. Today´s THz technology pursues semiconductor based miniature electronic devices operating at undeveloped electromagnetic frequency band between 100 GHz and 10 THz. Tremendous research progresses on THz technology have been made for decades. However, it is limited in the power and performance of THz sources and systems for real applications. (omitted)

• Korean Journal of Community Nutrition
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• v.2 no.4
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• pp.505-514
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• 1997

Concern about body weight among young females is too much, so distorted body image and restrained eating are serious problems among Korean young females. A society preoccupied with thinness give a psychological burden to women, this burden may have adverse effects on health physically and psychologically. We tried this study to investigate body image, eating problems, and dietary intakes among female college students in urban areas of Korea. We satisfactorily surveyed using their body weight, desired weight dieting, binge eating, and night eating by self-questionnaires with 500 female college students. We evaluated their dietary intakes by semi-quantitative food frequency questionnaires to assess their usual intakes. After removing incomplete data, we analyzed 469 data by SAS 6.10. The 469 women aged 21.1 years. Their mean height, weight, and BMI were 161.4cm, 52.5kg, and 20.2kg/$m^2$ respectively. Though the frequency of obesity was only 2.6$\%$, the frequency of dissatisfaction with their body weight was 84.7$\%$. Female college students desired their hight, weight, and BMI to be 165.8cm, 48.2kg, and 17.5kg/$m^2$, respectively. The frequency of binge eating and night eating were 20.7$\%$and 6.8$\%$. The odds ratios for binge eating and night eating were 10.9(95$\%$ CI : 2.6-15.1) and 6.0(95% CI : 1.8-14.8) in the group satisfied with their body weight compared with the dissatisfied group. The odds ratios for binge eating and night eating were 2.6(95% CI : 1.6-4.4) and 2.4(95% CI : 1.1-5.4) in the dieting group compared with the non-dieting group. The mean caloric intake was 1, 840kacl and percent intakes of carbohydrate, protein, and fat wee 57.2$\%$, 16.3$\%$, and 24.0$\%$, respectively. The dieting group showed deficient intakes of protein and calcium significantly compared with the non-dieting group showed deficient intakes of protein and calcium significantly compared with the non-dieting group. Almost all women college students in urban area had dissatisfaction with their body shape, and desired severe undrerweight. The frequency of binge eating and night eating increased according to dissatisfaction with body weight, diet, and distortion of body image. Dieting has adverse effect on the intakes of essential nutrients. Educations is needed to correct distorted body image, and bad eating habits in young females, and marked preoccupation with thinness among women should then be reduced. (Korean J Community Nutrition2(4) : 505-514, 1997)

• Journal of Ecology and Environment
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• v.45 no.1
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• pp.54-61
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• 2021

Background: The sunfleck is an important light environmental factor for plants that live under the shade of trees. Currently, the smartfarm has a system that can artificially create these sunfleks. Therefore, it was intended to find optimal light conditions by measuring and analyzing photosynthetic responses of Eutrema japonica (Miq.) Koidz., a plant living in shade with high economic value under artificial sunflecks. Results: For this purpose, we used LED pulsed light as the simulated sunflecks and set the light frequency levels of six chambers to 20 Hz, 60 Hz, 180 Hz, 540 Hz, 1620 Hz, and 4860 Hz of a pulsed LED grow system in a plant factory and the duty ratio of the all chambers was set to 30%, 50%, and 70% every 2 weeks. We measured the photosynthetic rate, transpiration rate, stomatal conductance, and substomatal CO2 partial pressure of E. japonica under each light condition. We also calculated the results of measurement, A/Ci, and water use efficiency. According to our results, the photosynthetic rate was not different among different duty ratios, the transpiration rate was higher at the duty ratio of 70% than 30% and 50%, and stomatal conductance was higher at 50% and 70% than at 30%. In addition, the substomatal CO2 partial pressure was higher at the duty ratio of 50% than 30% and 70%, and A/Ci was higher at 30% than 50% and 70%. Water use efficiency was higher at 30% and 50% than at 70%. While the transpiration rate and stomatal conductance generally tended to become higher as the frequency level decreased, other physiological items did not change with different frequency levels. Conclusions: Our results showed that 30% and 50% duty ratios could be better in the cultivation of E. japonica due to suffering from water stress as well as light stress in environments with the 70% duty ratio by decreasing water use efficiency. These results suggest that E. japonica is adapted under the light environment with nature sunflecks around 30-50% duty ratio and low light frequency around 20 Hz.

• Journal of the Korean Institute of Telematics and Electronics
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• v.15 no.2
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• pp.22-27
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• 1978

An improved active R filter is proposed which contains only resistors and two operational amplifiers represented by their single pole model. The filter has very low sensitivities to all circuit parameters, is suitable for low frequency and low 9 applications in addition to high frequency and high 0, and realizes various biquadratic transfer functions simultaneously with lower resistance ratios. The independent control of design specifications is possible in the circuit. Experimental results in laboratory are presented.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.102-105
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• 1993

In this paper, we examine the method of articulation test which is effective in evaluating the speech quality in mobile communication. The korean monosyllable lists for articulation test are developed based upon the frequency of occurrence of korean monosyllables used under natural environment. The monosyllable articulation lists are recorded through the public switch telecommunication network(PSTN) and mobile telecommunication system. The recorded lists are presented to the listeners through the headphone in order to deep the listening conditions equal. It is showen that the articulation lists perform well under different signal-to-noise ratios and the restriction of some frequency ranges. Some articulation scores obtained within the PSTN and between the mobile communication system and PSTN are presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.61-68
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• 2008

A set of modal parameters of a stay-cable have been extracted from a moving picture captured by a digital camera supported by shaking hands. It is hard to identify the center of targets attached on the cable surface from the blurred cable motion image, because of the high speed motion of cable, low sampling frequency of camera, and the shaking effect of camera. This study proposes a multi-template matching algorithm to resolve such difficulties. In addition, a sensitivity-based system identification algorithm is introduced to extract the natural frequencies and damping ratios from the ambient cable vibration data. Three sets of vibration tests are conducted to examine the validity of the proposed algorithms. The results show that the proposed technique is pretty feasible for extracting modal parameters from the severely shaking motion pictures.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.1
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• pp.66-73
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• 2011

This paper deals with free vibrations of the tapered beams with the constant surface area. The surface area of the objective beams are always held constant regardless shape functions of the cross-sectional depth. The shape functions are chosen as the linear and parabolic ones. Ordinary differential equations governing free vibrations of such beams are derived and solved numerically for determining the natural frequencies. In the numerical examples, hinged-hinged, hinged-clamped and clamped-clamped end constraints are considered. As the numerical results, the relationships between non-dimensional frequency parameters and various beam parameters such as section ratio, surface area ratio, end constraint and taper type are reported in tables and figures. Especially, section ratios of the strongest beam are calculated, under which the maximum frequencies are achieved.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.202-211
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• 1998

The present paper proposes a modal analysis procedure to obtain exact modal parameters (natural frequencies, damping ratios, eigenvectors) for general, non-uniform beam-like structures. The proposed method includes a derivation of the system dynamic matrix for a Timoshenko beam element. The proposed method provides not only exact modal parameters but also exact frequency response functions (FRFs) for general beam structures. A time domain analysis method is also proposed. Two examples are provided for validating and illustrating the proposed method. The first numerical example compares the proposed method with FEM. The second example deals with a non-uniform beam structure supported in joints with damping property. The numerical study proves that the proposed method is useful for the dynamic analysis of continuous systems consisting of beam-like structures.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.364-367
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• 2000

This paper describes a Push-Pull type high fre-quency resonant inverter conposed of consolidation of boost converter circuit and resonant circuit. By using a boost converter circuit the proposed inverter can obtain a twice input voltage of reson ant circuit and reduce a secondary turn ratios. By using both boost-converter and switching device can be reduce by half. Also the ana-lysis of the proposed circuit was described by using normalized parameter and operating characteristics have been evaluated as to switching frequency and parameters. In the future this pro-posed inverter shows that it can be practically used as a power source system for the lighting equipment of discharge lamp induction heating applications.

• Journal of the Korean Society of Marine Environment & Safety
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• v.5 no.2
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• pp.35-44
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• 1999

High negative pressure coefficient is formed in the corner of the bluff body structures. For many curtain wall designers this phenomena is of interest because this high negative pressure coefficient is adopted in structural calculation. The present study is aimed to investigate shedding vortex characteristics of two-dimensional rectangular prism flow. Unsteady calculation by finite difference method based upon SOLA is carried out for three aspect ratios(1:1, 1:2, 1:3) of Re=10$^4$ in viscous incompressible flow within infinite domain. Fluctuation of velocity components at various pick-up points and time variation of drag and lift coefficients are analysed by FFT method to reveal shedding vortex frequency patterns. At aspect ratio 1:1, one primary Strouhal number appears for about all pick-up points. At aspect ratio 1:2, two representative Strouhal numbers are classified by pick-up positions and their flows show two different reattachment patterns. For aspect ratio 1:3, frequency spectrum maintains multiple peaks.