• Journal of Mechanical Science and Technology
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• v.18 no.2
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• pp.294-301
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• 2004

The natural convective heat transfer in a rectangular enclosure with a heating source has been studied by experiment and numerical analysis. The governing equations were solved by a finite volume method, a SIMPLE algorithm was adopted to solve a pressure term. The parameters for the numerical study are positions and surface temperatures of a heating source i.e., Y /H =0.25, 0.5, 0.75 and 11$^{\circ}C$ $\leq$ΔT$\leq$59$^{\circ}C$. The results of isotherms and velocity vectors have been represented, and the numerical results showed a good agreement with experimental values. Based on the numerical results, the mean Nusselt number of the rectangular enclosure wall could be expressed as a function of Grashof number.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.303-306
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• 2005

We report the self-aligned low temperature poly silicon (LTPS) TFT process using simple doping process. In conventional LTPS-TFT, the Lightly Doped Drain (LDD) doping and source/drain doping are processed separately by aligning the gate with the source and drain during the gate lithography step. This ne w process not only fabricates fully self-aligned low temperature poly silicon TFTs with symmetric LDD structure but also simplifies the process flow with combined source/drain doping and LDD doping in one step. LDD doping process can be achieved using only source/drain doping process according to the new structure. In this paper, the TFT characteristics of NMOS and PMOS using the new doping process will be discussed.

• Journal of Information Technology Applications and Management
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• v.24 no.1
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• pp.157-167
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• 2017

This paper proposes a simple sound source localization (SSL) method based on signal energies comparison and partial cross correlation for TDOA computation. Many sound source localization methods include multiple TDOA computations in order to eliminate front-back confusion. Multiple TDOA computations however increase the methods' computation times which need to be as minimal as possible for real-time applications. Our aim in this paper is to achieve the same results of localization using fewer computations. Using three microphones, we first compare signal energies to predict which quadrant the sound source is in, and then we use partial cross correlation to estimate the TDOA value before computing the azimuth value. Also, we apply a threshold value to reinforce our prediction method. Our experimental results show that the proposed method has less computation time; spending approximately 30% less time than previous three microphone methods.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.121-124
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• 2001

Dynamic Source Route(DSR) protocol is a simple and efficient routing protocol designed specially for use of the multi-hop Ad Hoc Network. DSR allows the network to be completely self-organized and self-configured without the need for any existing infrastructure or administration. DSR protocol consists of the two mechanisms of Router discovery and Router Maintenance, works entirely On-demand in all aspects. In this paper, we will present the performance of DSR protocol on the multi-hop wireless Ad Hoc Networks, illustrate it with simulation, and then analysis the algorism of DSR.

• 전기의세계
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• v.14 no.5
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• pp.20-27
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• 1965

There are several methods of speed control in induction motors. One of which is to change the frequency of source but was not used frequently because of the difficulty of frequency-change. Then, the development of frequency changer using semiconductor enables the method useful. In this paper the speed characteristics of mechanical output, secondary input torque and secondary power factor are described when the frequency of source and voltage which is proportional to the frequency of source in order to make the flux in the air gap in constant, are changed. The above characteristics are searched on the basis of the rated characteristics of the motor. Because the ratio of these is proportional to that of the secondary current or the square value of it. To get the ratio of the secondary current, a current circle diagram is introduced, and the magnitude of the ratio from this diagram is accurate and simple. Experimental results are in good agreement with theoretical predictions.

• Current Optics and Photonics
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• v.2 no.6
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• pp.563-567
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• 2018

We propose and experimentally demonstrate a simple tunable photonic microwave band-pass filter with high resolution using a reflective semiconductor optical amplifier (RSOA) and an optical time-delay line. The RSOA is used as a gain medium for generating cross-gain modulation (XGM) effect as well as an optical source. The optical source provides narrow spectral width by self-injection locking the RSOA in conjunction with a partial reflection filter with specific center wavelength. Then, when the RSOA is operated in the saturation region and the modulated recursive signal is injected into the RSOA, the recursive signal is inversely copied to the injection locked optical source due to the XGM effect. Also, the tunability of the passband of the proposed microwave filter is shown by controlling an optical time-delay line in a recursive loop.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.1
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• pp.9-15
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• 2021

In multi-string light-emitting diode (LED) driver system, current balancing is crucial because the brightness of LED is directly related to its forward current. This paper presents a novel LED current balancing topology using current-fed Z-source converter. With the proposed structure, currents flowing through two LED strings are automatically balanced owing to the charge-balance condition on capacitors. Operation of the proposed converter is simple and the proposed converter uses only one active switch and one diode. Moreover, low-side gate driving can be used to operate the active switch. To verify the operation of the proposed LED current balancing converter, a prototype is built and tested with different numbers of LEDs.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.1
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• pp.46-52
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• 2012

Separate extraction of source ($R_S$) and drain ($R_D$) resistances caused by process, layout variations and long term degradation is very important in modeling and characterization of MOSFETs. In this work, we propose "Avalanche Hot-Source Method (AHSM)" for simple separated extraction of $R_S$ and $R_D$ in a single device. In AHSM, the high field region near the drain works as a new source for abundant carriers governing the current-voltage relationship in the MOSFET at high drain bias. We applied AHSM to n-channel MOSFETs as single-finger type with different channel width/length (W/L) combinations and verified its usefulness in the extraction of $R_S$ and $R_D$. We also confirmed that there is a negligible drift in the threshold voltage ($V_T$) and the subthreshold slope (SSW) even after application of the method to devices under practical conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.8
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• pp.737-743
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• 2006

[ $Li[Co_{0.50}Li_{0.17}Mn_{0.33}]O_2$ ] powder was prepared using a simple combustion method. specially, ratio of 2:1, 3:2, 1:1, 2:3, 1:2 was adopted as acetate source/nitrate source. The diffraction pattern of $Li[Co_{0.50}Li_{0.17}Mn_{0.33}]O_2$ powder showed that this compound could be classified as hexagonal $a-NaFeO_2$ structure (space group : $R\bar{3}m$). The size of powder was less than $1{\mu}m$. Small particle size of cathode powder would give a good ionic and electronic conductivity to cathode electrode, which made of cathode powder. As the increase of nitrate source-ratio, discharge capacity of $Li[Co_{0.50}Li_{0.17}Mn_{0.33}]O_2$ at high charge-discharge rate was increased. When the ratio of acetate source/nitrate source was 1:2, discharge capacity at 10 C rate (2000 mA/g) was 180 mAh/g. It was $10{\sim}15%$ larger than that of powder, which have 2:1 as acetate source/nitrate ratio.

• Journal of environmental and Sanitary engineering
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• v.14 no.2
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• pp.56-67
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• 1999

This study was performed to suggest the basic data and plans for the establishment of safe water supply plans in simple water supply piped system in the rural areas. In 4 different places, 24 points of water sources 36 points of taps from water sources were sampled. Of the whole 60 points, 55 points were ground water and 5 points were surface water. 14 items were measured for the analysis of water quality on each samples. The measured items were analyzed again by statistical method ; cluster analysis and principle components analysis. The results of this study are as followed. 1) In water quality analysis on water sources, 4 items, bacteria, E.coli, NH3-N and Fe exceed the standard. Of 24 points, 20 points(83%) on bacteria, 1 point(4%) on NH3-N and Fe exceed the standard. 2) In water quality analysis on near and remote taps, 4 items, bacteria, E.coli, NH3-N and Fe , exceed the standard. Of 36 points, 20 points (81%) on bactria, 1 pint(3%) on NH3-N and Fe exceed the standard. 3)Cluster analysis on water quality shows the differences by the kinds of water sources, geographical characteristics and distance from water sources. 4) Principle components analysis on ground water shows that Factor 1 and Factor 3 are natural fluctuation by the content of soil. Also, Factor 2 and Factor 4 are penetration of pollutants to underground. Therefore, it is needed to take deeper ground water in order to prevent from pollution in the areas which have ground water as water source . 5) Principle components analysis on surface water shows that Factor 1 is penetration of vacteria from surface to water source when rainfalls. Also, Factor 2 is fluctuation of water quality by the geographical characteristics. Therefore, the counterplans against non-point pollution source must be taken. Filtration and disinfection facilities are needed in the areas which have surface water as water source.