• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1515_1516
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• 2009

A 440MHz wireless and passive surface acoustic wave (SAW) based micro-sensor was developed for simultaneous measurement of temperature and humidity. The developed sensor is composed of a SAW reflective delay lines structured by an IDT (Inter-Digital Transducer), four reflectors and humidity sensitive film (polyimide). Polyimide was dry-ecthed by RIE (Reactive Ion Etching) to obtain high roughness, which gives the large reaction area resulting in high sensitivity. In wireless testing using a network analyzer, sharp reflection peaks with high S/N ratio, small signal attenuation, and few spurious peaks were observed in the time domain. High sensitivity towards the temperature and humidiy were also observed in the large concentration range. The obtained sensitivity was $16.8^{\circ}/^{\circ}C$ for temperature sensor and $15.8^{\circ}$/%RH for humidity sensor.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.5
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• pp.197-202
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• 2002

In this paper, the characteristics of the household AC power line network is analyzed for the low bit rate powerline communication (PLC) in the frequency range from 10㎑ to 450㎑ The PLC channel transfer characteristics including its characteristic impedance are derived based on the network topology which is constructed with the household power lines loaded with the various types of electric apparatus. Both the distributed circuit analysis and the lumped circuit model based analysis are applied for the characterization of the PLC channel and the results are compared by the computer simulations. The analysis illustrates very well the adverse effects caused by the loading of electric apparatus and as well those casued by the reflection of wavers in the household AC Power line communication network.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.226-229
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• 2001

The combined transmission lines with the underground power cables are continuously expanded in power systems. So the fault of combined transmission line is increased every year as the complication of underground transmission line. In this paper. traveling wave theory and DWT wavelet transform are used for fast and accurate detection of fault location at the combined transmission line. Traveling wave travels to each bus like surge and repeats reflection and transmission till transient signal is completely disappeared. When fault is occurred on overhead and underground tine, the fault location detecting algorithm was performed with using continuous peak value time-delay of traveling wave reflected from A bus.

• 한국가시화정보학회:학술대회논문집
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• 2004.04a
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• pp.1-7
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• 2004

When a vortex diffracts upon encountering a vortex, many strong and weak waves are produced in the course of interaction. They are the cause of shock wave attenuation and noise production. This phenomenon is fundamental to understanding the more complex supersonic turbulent Jet noise. In this paper we have reviewed the research on shock-vortex interaction we have carried on last seven years. We have computationally investigated the parameter effect. When a shock is strong, shock diffraction pattern becomes complex since the slip lines from the triple points on Mach stem curl into the vortex, causing an entropy layer. When the vortex is unstable, vortexlets are brought about each of which make shock diffraction of a reduced intensity. Strong vortex produces quadrupole noise as it impinges into a vortex. Elementary interaction models such as shock splitting, shock reflection, and shock penetration are presented based on shock tube experiment. These models are also verified by computational approach. They easily explain production and propagation of the aforementioned quadrupole noise, Diverging acoustics are explained in terms of shock-vortexlet interactions for which a computational model Is constructed.

• Research in Mathematical Education
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• v.9 no.3 s.23
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• pp.257-267
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• 2005

When notions of numbers are expanded from natural number to complex number, a similar mathematical phenomenon can be observed in each number. As a case study, to complex number, the phenomenon is investigated carefully and teaching materials are created. Then complex number is expressed with matrices and is geometrically treated, so a new number which is an extension of complex number is discovered. Thus, teaching material regarding to complex number and matrices is made for students of ordinary level. Moreover, for talented students, material about an extension of complex number can be added to the previous one.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.305-307
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• 2001

In this paper, the household AC power line network is characterized for the low bit rate power line communication (PLC) in the frequency range from 10kHz to 450kHz. Various types of electric apparatus and the power lines constitute the network topology, and the PLC channel transfer function and the channel impedance are derived based on the constructed network topology. The channel characteristics derived with the lumped circuit model and the distributed circuit model are compared using the computer simulations. The effect of the wave reflection and signal distortions are also investigated.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1670-1674
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• 1998

Now and then there are many electrical accidents between cable and line post insulator which is degraded by long time using, causing leakage current on the surface of insulator. In this paper it is denied that the 22.9 KV-y distribution lines are protected by binding cover which is needed from fog or rainy moisture, surges occurring by swiching or lightening pulse. It is analyzed to investgate the unballanced transfer characteristics and reflection coefficient by using bidding cover and non-cover. It was tested the radio interference voltage in the test room. In the factory it was tested the amount of leakage current causing on the surface of insulator in the state of no load and 70(%) load.

• Journal of Integrative Natural Science
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• v.3 no.1
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• pp.24-27
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• 2010

Multi-functionalized rugate porous silicon (PSi) for biosensor was developed by hydrosilylation with silole and its further reaction with biotin groups. PSi was generated by an electrochemical etching of silicon wafer in aqueous ethanolic HF solution PSi prepared by using etching conditions showed that many sharp spectral lines can be obtained in the optical reflectivity spectrum. 1,1-hydrovinyl-2,3,4,5-tetraphenylsilole was obtained from the reaction of 1,1-dilithio-2,3,4,5-tetraphenyl-1,3-butadiene with dichlorovinylsilane. Multi-functionalized PSi with silole and biotin groups was characterized by UV-vis absorption spectroscopy, Ocean optics 2000 spectrometer, and fluorescence spectroscopy. Optical characteristics such as reflectivity and photoluminescence (PL) were observed. An increase of the reflection wavelength in the reflectivity spectrum by 20 nm was observed, indicative of a change in refractive indices induced by hydrosilylation of the silole and biotin groups to the rugate PSi. This red-shift was attributed to the replacement of some of the Si-H group of fresh rugate PSi with silole and biotin group.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.788-795
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• 2000

In this paper, a method for the precise impedance measurement of coaxial loads using an offset open and short as the reflection standards and reference air lines with different lengths as the impedance standards is proposed. Measured input impedances of power sensors and thermistor mounts obtained from SWR bridges(5~400MHz) and a vector network analyzer(100~1,000MHz) are presented in the frequency range of 5MHz to 1,000 MHz.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1871-1873
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• 2000

There are many electrical accidents between bare wire and line post insulator which is degraded by long time using, causing leakage current on the surface of insulator. In this paper it is presented that the 22.9 Kv-y distribution lines are protected by binding cover which is needed from fog or rainy moisture, surges occurring by switching or lightening pulse. It is analyzed to investigate the unbalanced transfer characteristics and reflection coefficient by using binding cover and non-cover. It was tested the radio interference voltage in the test room and electric field strength by calculation between binding cover and non-cover. In the factory the leakage current causing on the surface of insulator was tested in the state of light load and heavy load.