• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.3
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• pp.301-312
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• 1999

Experiments were carried out to evaluate performance of the cold air distribution systems with an ice storage tank in test room. Cold air distribution systems provide primary air for comfort conditioning or process cooling at coil discharge temperatures$4^{\circ}C$ to$11^{\circ}C$. The application of a cold air distribution system allows for the downsizing of air distribution equipment and central plant equipment when ice storage tank is used. The benefit of a cold air distribution system include a decrease in the floor-to-floor height, increase floor space, reduced building capital costs, reduced energy use and demand. The use of cold air distribution can result in the most cost effective system and is currently being implemented world wise as the new standard in air conditioning systems. In this study, the cold air distribution system is compared with the general ice storage system. Under the same cooling load conditions, experimental results show that the supply air volume of cold air distribution system decrease 38%, and decrease 45% flow rate of brine for the general ice storage system.

• ETRI Journal
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• v.35 no.2
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• pp.344-347
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• 2013

This letter presents a compact dual-mode tri-band bandpass filter by using a short-circuited stub-loaded stepped-impedance resonator (SIR) and a short-circuited stub-loaded uniform impedance resonator. Also, a hairpin SIR geometry is introduced to miniature the size of this filter while maintaining excellent performance. The use of a short-circuited stub at the central point of the hairpin SIR can generate two resonant modes in two passbands. Its equivalent circuit structure is analyzed by using the even-odd mode theory. For demonstration purposes, a tri-band filter for the applications of the Global Positioning System at 1.57 GHz, Worldwide Interoperability for Microwave Access at 3.5 GHz, and wireless local area networks at 5.2 GHz is designed, fabricated, and measured.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.303-311
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• 2012

An innovative interpretation of the per-unit interior permanent magnet (IPM) machine model known as Design Space is presented in this paper. Based on the proposed Design Space formulation, an effective computation method to predict IPM machine performance factors, such as the current and power factor in a full range of speeds, is proposed. A systematic methodology is summarized, which translates the full speed range machine design procedure into the region determination on the so-called Design Space. The effect of dc-link voltage is also analyzed in a similar manner with the current and power factor. A series of IPM motors have been designed, and a preferred motor is selected with the help of the proposed Design Space Methodology (DSM), which has the best tradeoff between the nominal voltage and the dropped voltage condition. Experiment results show that the selected motor satisfies the machine requirements and all the design constrains, such as the current and back-EMF limitations.

• The KSFM Journal of Fluid Machinery
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• v.18 no.6
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• pp.71-75
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• 2015

The flow and noise characteristics of the regenerative blower are evaluated experimentally. To decrease the noise of regenerative blower at a high frequency, we arrange the impeller vanes unevenly by special formula. The uneven pitch formular consists of the combination of trigonometric function. The magnitude of degree between each vanes and the control parameters of trigonometric functions are main design parameters for the uneven pitch. The flow characteristics of even and uneven impellers are tested by the fan tester and compared each results. The efficiency of a blower is calculated by the axial power using a dynamo system. The noise property of designed impeller is measured in an anechoic room. In this study, we certify that the uneven pitch impeller is effective in the noise reduction at a high frequency.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.295-303
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• 2013

This paper reports an investigation of pulse width modulation (PWM) techniques for two-phase brushless DC (BLDC) motors fed by a two-phase eight-switch inverter in a fan application. The three-phase BLDC motor is widely applied in industry; however, a lower-cost two-phase BLDC motor and drive circuit has been greatly in demand in recent years. In this paper, we introduce a mathematical model of the two-phase BLDC motor with sinusoidal back electromotive forces (EMFs) based on traditional three-phase BLDC motors. To simplify the drive algorithm and speed up its application, we analyze the principle of block commutation for a two-phase BLDC motor drive in the 180-electrical-degree conduction mode, and we further propose five PWM schemes to improve the commutation performance of the two-phase BLDC drive. The effectiveness of the proposed PWM methods is verified through experiments.

• Journal of the Korean Chemical Society
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• v.59 no.2
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• pp.136-141
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• 2015

We have discovered that quercetin, once coated on the CdSe and CdSe-CdS quantum dots (QDs), becoming highly water soluble. In the present work, we have successfully synthesized CdSe/CdS/N-Acetyl-L-Cysteine(NAC)/Quercetin nano-composites in the aqueous solution. The products were characterized using UV-vis spectroscopy, X-ray powder diffraction, fluorescence spectroscopy, and Fourier transform infrared spectroscopy. The transmission electron microscopy (TEM) tests indicated that our nano-composite products are highly stable with homogeneous particle size and great monodispersity. Quercetin coated nano-composite CdSe/CdS/NAC/Quercetin showed different fluorescence behavior from that of CdSe/CdS/NAC. Most amazingly, the synthesized CdSe/CdS/NAC/Quercetin nano-composite exhibits strong antibacterial activity. The combination of the strong fluorescence and its antibacterial activity makes the quercetin modified quantum dots as a potential candidate for cancer targeted therapy and other cancer treatments.

• ETRI Journal
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• v.39 no.5
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• pp.756-763
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• 2017

A switchable single-wideband (SWB)-to-dual-wideband (DWB) bandpass filter (BPF), which is realized by using lumped switches, is presented in this paper. By alternating the operation modes-ON and OFF-in which the ON mode is achieved by placing the capacitors at the switching spots and the OFF mode is achieved by replacing the capacitors with inductors, DWB-to-SWB BPF can be achieved on the same device. In addition, by changing the capacitor values, the center frequency (CF) of the lower passband of DWB BPF can be easily tuned from 1.69 GHz to 2.22 GHz, while the higher passband stays almost unchanged. As an example, an SWB-to-DWB BPF is designed, fabricated, and measured. This BPF exhibits good performance including wideband, high isolation, compact size, and ability to switch.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.170-178
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• 1999

In general, an impeller of centrifugal turbomachinery is designed at isolated condition without considering the presence of a volute, but when the impeller is operating with its volute, the performance of impeller can be different. This is largely caused by the interaction between the impeller and volute flow fields. The magnitude of distortion is increased as the operating point is away from the design point and, as a result, the interaction between the impeller and volute is stronger. In the present calculation, the flow through the impeller is simulated using coarse grids. The flow within the impeller and the volute is naturally unsteady, but the flow is assumed to be steady across the interface between the volute and impeller flow fields. Under the assumption of steady three-dimensional incompressible turbulent flow, the time averaged N-S equations involving standard k-$\epsilon$ turbulent model was solved by the F.V.M. The calculation results are compared with the experimental results obtained for an industrial fan by Sakai etc. and the Hood agreement is demonstrated. And the effects of the impeller-volute interaction are studied.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.905-910
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• 2012

This paper reports an investigation of pulse width modulation (PWM) techniques for twophase brushless DC (BLDC) motors fed by a two-phase eight-switch inverter in a fan application. The three-phase BLDC motor is widely applied in industry; however, a lower-cost two-phase BLDC motor and drive circuit has been greatly in demand in recent years. In this paper, we introduce a mathematical model of the two-phase BLDC motor with sinusoidal back electromotive forces (EMFs) based on traditional three-phase BLDC motors. To simplify the drive algorithm and speed up its application, we analyze the principle of block commutation for a two-phase BLDC motor drive in the 180-electricaldegree conduction mode, and we further propose five PWM schemes to improve the commutation performance of the two-phase BLDC drive. The effectiveness of the proposed PWM methods is verified through experiments.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.16-20
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• 2003

Recently, The fast change of fishing boat fishery surrounding environment is connected by request of fan shape development that meet in restructuring of existing fishing boat fishery and new community, economical surrounding. In southern sea district along the coast work and district along the coast fishing bats that sail to exposed propeller fishing net, rope etc.. cold real condition that accident is increasing every year. This study is thing which analyze main performance of minuteness water jet type district along the coast fishing boat through model examination to propeller protection tunnel sticking district along the coast fishing boat that correct existing stem shape for marine accident prevention of district along the coast fishing boat in viewpoint such as ideal and examines.