• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.3
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• pp.425-433
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• 1994

The conventional weakly-coupled tap-off for CATV and/or MATV transmitting circuits has been fabricated empirically and experimentally. So, the theoretical analysis or the design method of the conventional one has not been established, the characteristics of which were not good. To solve these problems, we have proposed a modified weakly-coupled freedom in design. This paper describes the design theories and analysis method of the theoretical frequency characteristics of a Modified Weakly-coupled Tap-off with high density of coupling intervals for CATV and/or MATV system. From the theoretical analysis it has been shown that the frequency characteristics of the tap-off proposed here are improved much in comparision with the conventional one. Furthermore, the practical measurements of frequency characteristics for the fabricated circuits show agreement with the theoretical results, and hence, the validity of proposed design and analysis methods has been confirmed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.2
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• pp.105-110
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• 2004

The objective of this study is to obtain the instability characteristics of the plane jet impinging on circular cylinder associated with the cylinder-tone. It is found that the characteristics depends upon he ratio of the cylinder diameter to the nozzle width, D/h, and the jet velocity. When the ratio is oderate the cylinder-tone is similar to the edge-tone. With increase of the ratio, its characteristics ecomes similar to that of the plate-tone in which only the high-speed tone associated with turbulent et is generated. When D/h 〈1. the frequency range, especially the lower limit of frequency, is ignificantly influenced by the cylinder diameter. At around D/h = 1/2, while low speed tones are nduced with the antisymmetric mode of instability and affected by the vortex shedding from the ylinder, high-speed tones are generated, at first, with the symmetric mode of instability. and then, ith antisymmetric mode, as the jet velocity increases.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.5
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• pp.352-357
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• 2000

This paper presents about an example of circuit design and characteristics of inverter according to the variable capacitance of the DC voltage source separation capacitor used in ZVS-HB type high frequency resonant inverter. The soft switching technology known as ZVS is used to reduce turn off loss at switching. In the event the capacitance of the DC voltage source separation capacitor is varied, the analysis of inverter circuit has generally described by using normalized parameter and operating characteristics have been evaluated in terms of switching frequency and parameters. According to the calculated characteristics value, a method of the circuit designs and operating characteristic of the inverter is also presented in this paper. In addition, this paper proves the validity of theoretical analysis through the experiment. This proposed inverter shows that it can be practically used in future as power source system for the lighting equipment of discharge lamp, DC-DC converter etc.

• Journal of the Korean Society of Clothing and Textiles
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• v.47 no.1
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• pp.35-51
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• 2023

This study used text mining to extract 2,842 keywords from 7,397 product names and organized them into categories in order to analyze the characteristics of keywords appearing in the product names of jeans after 2020. The item category included denim and Chungbaji [청바지], and Ilja [일자], while the silhouette category included wide and bootcut. In addition, high-waist and banding comprised the making sector, and the materials category consisted of napping, spandex, and soft blue. Denim surpassed the others in frequency, co-occurrence frequency, and centrality, and co-appeared with various other keywords. Also, the co-appearance of item and silhouette was prominent, and there were many keyword combinations that showed characteristics related to (a) high waist; (b) hemline detail; (c) rubber band; and (d) partial tearing. Furthermore, idiom expressions such as 'slim fit' and 'back tearing', which were not highlighted in the co-occurrence frequency, were additionally confirmed through correlation. Therefore, the product name analysis effectively identified the detailed characteristics of the silhouette and the making of jeans preferred by consumers.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.2
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• pp.1-7
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• 2010

This paper presents empirical equations indicating the high frequency performance characteristics of air-cored induction coil sensors with their constructional parameters. An air-cored induction coil sensor is widely used due to good linearity at low frequency ranges but the sensor has weakness of relatively low sensitivity to the magnetic field. At high frequency ranges, the sensitivity can be dramatically increased, largely depending on the frequency of the injected field, and this property can be a great asset to some electromagnetic inspections, since they utilize the interrogating current with a fixed frequency. The application of this property of the coil sensor requires the estimation of its high frequency performance. We made experiments on the frequency responses of the coil sensors under diverse constructional conditions and, on the basis of the experimental results, the high frequency performance, such as the resonant frequency and the sensitivity at the frequency, was estimated, as a function of the constructional parameters of the coil sensor. The good agreements between experimental and estimated data were reported.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2002.11a
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• pp.293-296
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• 2002

This paper describes the instantaneous current resultant type load parallel high frequency resonant inverter consisting of three unit half-bridge serial and parallel resonant inverter can be used as power source of induction heating. This proposed inverter can reduce distribution of the switching current because of using the current of serial resonant circuit to the input current of the parallel one. The analysis of the proposed circuit is generally described by using the normalized parameters. Also, the principle of basic operating and the its characteristics are estimated by the parameters such as switching frequency($\mu$), load resistance(λ). Experimental results are presented to verify theoretical discussion. This proposed inverter will can be practically used as a power supply in various fields as induction heating application, DC-DC converter etc.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.83-88
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• 2004

High voltage AC electric field has been applied to turbulent propane jets to investigate the effect of electric field on liftoff characteristics. Liftoff velocity and liftoff height have been measured by varying the applied voltage and frequency. Liftoff velocities were delayed and liftoff heights were reduced by applying AC, not by DC. The electric effect became disappeared with further increasing jet velocities, which shows that the effect can be explained by the balance between inertia force and electric force. The flame stabilization effect was intensified as either applied voltage or frequency increased. Plasma streamers were generated between the flame and the jet under high voltage conditions. Liftoff velocity in the absence of plasma can be well correlated by the function of voltage and frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.664-669
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• 2000

Angular misalignment is one of the important causes for shaft vibration of turbine-generator in 1000MW nuclear power plant. It may cause the plant unexpected shutdown and subsequent accident. The change of dynamic characteristics in journal bearing and rotor due to angular misalignment in high pressure turbine is analyzed. The stiffness/damping coefficients of journal bearing increase as angular misalignment. Subsequently the natural frequency of HP turbine is changed. It was found that the natural frequency may locate near 2 times operating frequency in case of severe misalignment.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.447-451
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• 1998

This paper conducts a study on a non-contact power delivering system using high-frequency inverter with the purpose of discussing the non-contact electric power transmission characteristics through circuit analysis, magnetic analysis and feasible experiments. In this power delivering scheme, various properties pertaining to the non-contact transformer of the power system such as the design, the core depth, core material, primary side frequency etc. are considered with a view of improving the non-contact power dilivery to the secondary.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.223-230
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• 2005

The unsteady nature of vortex structures has been investigated by a large eddy simulation (LES) in an axial flow fan with a shroud covering only the rear region of its rotor tip. The simulation shows that the tip vortex plays a major role in the structure and unsteady behavior of the vortical flow in the fan. The movements of the vortex structures induce high-pressure fluctuations on the rotor blade and in the blade passage. Frequency characteristics of the fluctuating pressure on the rotor blade are analyzed using wavelet transform. The dominant frequency of the real-time pressure selected at the high pressure fluctuation region corresponds well to that of the fluctuating rotor torque and the experimental result of fan noise. It is mainly generated due to the unsteady behavior of the vortical flow, such as the tip vortex and the leading edge separation vortex.