• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.284-286
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• 2009

In this paper, we consider a cognitive radio system operating as secondary user. It uses an empty channel that is not currently used by primary users having the license to the channel. In the previous works, secondary user looks for an empty channel by choosing any channel in order or randomly and by sensing the channel to distinguish whether primary users are using. But if primary user is fixed type, we will find an empty channel faster than the mentioned channel selecting methods by using a method considering prior information about cases that primary user used the channel, since it is possible to analogize the channel access possibility of primary user according to regular time and position. Therefore, we propose a channel searching method based on the channel list for the purpose of reducing the channel searching time and improving throughput of secondary users. Firstly, we determine a weighting value of each channel based on the history of channel activities of primary users. This value is added to current channel state buffer and we search an empty channel from channel with smallest value to one with the biggest value. Finally, we compare the performances of the proposed method with those of the sequential channel searching and the random channel searching methods in terms of the average channel searching time and the average number of transmissions of secondary user.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2003.04a
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• pp.108-111
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• 2003

Altimeter data from the Topex/Poseidon (T/P) were analyzed to study the sea surface circulation and its variability in the North East Asian Seas. Long term averaged T/P sea level time series data where compared with in situ sea level measurements from a float-operated type tide gauge around of south Korea and Japan. Tf data are a large contaminated by 60-day tidal aliasing effect, very near the alias periods of M2 and S2. When this 60-day effect is removed, the data agree well with the tide gauge data with 4.6 cm averaged RMS difference. The T/P derived sea level variability reveals clearly the well-known, strong current-topography such as Kuroshio. The T/P mean sea level of North Pacific (NP) was higher than Yellow Sea (YS) and East Sea (ES). The T/P sea level variability, with strong eddy and meandering, was the largest in eastern part of Japan and this variability was mainly due to the influence of bottom topography in Kuroshio Extension area.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.6
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• pp.10-19
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• 2003

As the technical demand for biometrics is increasing, users expect that fingerprint recognition systems are operable with various fingerprint readers. However, current commercial off-the-shelf fingerprint recognition systems are no interoperable due to the lack of standardization in application program interfaces for fingerprint readers. A cross-matching fingerprint recognition system is a person authentication system based on fingerprints and utilizing different types of fingerprint readers. It should be able to overcome variations in fingerprint images acquired by different readers, such as the size, resolution, contrast of images. The purpose of this research is to develop across-matching fingerprint recognition system for fingerprint research of different sensing mechanism. The fingerprint readers tested in this study are optical, semiconductor and thermal sensor modules, and the prpoposed cross-matching system utilizes both a minutiae-based similarity and a ridge count-based similarity in matching fingerprint images acquired by different sensors.

• Journal of the Korean Magnetics Society
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• v.11 no.2
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• pp.50-57
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• 2001

Magnetic inductive probe was designed and assembled for sensing the residual stress developed in the ferromagnetic thin sheet. The residual stress measurement system with this probe could resolve the residual stresses developed in the sheet in terms of principal stress orientation, and magnitude of the principal stress. It was consumed that the obtained probe output voltage from the qualified ferromagnetic Fe-42Ni lead frame sheet and quality-rejected sheet is effectively determined using the developed device. The lead frame sheet which has accumulated a high level of residual stress always showed a distinctive stress distribution and magnitude compared with those of qualified lead frame sheet. Those differences were well resolved as functions of input current or used frequency.

• Journal of Sensor Science and Technology
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• v.1 no.1
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• pp.35-41
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• 1992

A constant temperature type of flow sensor using a solid state micromachining technology was developed for measuring the velocity of gas or liquid. It was designed to detect only the heat convection related to flow velocity. Other heat transfer terms and common mode interferences are canceled by differentiating both reference and exposed flow sensor. It employs the principle that the change of current through the sensing element can be used to measure the flow velocity. An experimental study of the behavior on this flow sensor was performed in a narrow tube(diameter : 8mm) for city water. The relation between power consumption of the flow sensor and square-root of flow velocity is almost linear in the low velocity range(0-200 cm/sec).

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.422-425
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• 2008

TerraSAR-X is new radar satellite operated at X-band, multi polarization, and multi beam mode. Compared with C-band or L-band SAR, the X-band system inherently suffers from more temporal decorrelation, but is more sensitive to surface deformation monitoring due to short wavelength (3.1 cm) and high spatial resolution (1m-3m). It is generally expected that sensitivity to estimate surface movement using TerraSAR-X will be increased by the factor of 10, compared to current C-band system with low spatial resolution such as ERS-2, Envisat. Many urban areas are experiencing land subsidence due to water, oil and natural gas withdrawal, underground excavation, sediment compaction, and so on. Monitoring of surface deformation is valuable for effectively limiting damage areas. In addition high accuracy and spatially dense subsidence map can be achieved by X-band InSAR observation, promoting identification and separation of various subsidence processes and leading to enhanced understanding via mechanical modeling. In this study we will introduce some initial InSAR results using new TerraSAR-X SAR data for surface deformation monitoring.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.92-95
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• 2008

The Geostationary Ocean Color Imager (GOCI) is under development to provide a monitoring of ocean-color around the Korean Peninsula from geostationary platforms. It is planned to be loaded on Communication, Ocean, and Meteorological Satellite (COMS) of Korea. The GOCI has been designed to provide multi-spectral data to detect, monitor, quantify, and predict short term changes of coastal ocean environment for marine science research and application purpose. The target area of GOCI observation covers sea area around the Korean Peninsula. Based on the nonlinear radiometric model, the GOCI calibration method has been derived. The radiometric model of GOCI has been validated through radiometric ground test. From this ground test result, GOCI radiometric model has been changed from second order to third order. In this paper, the radiometric test performed to evaluate the radiometric nonlinearity is described and the GOCI radiometric error propagation is analyzed. The GOCI radiometric calibration is based on onboard calibration devices; solar diffuser, DAMD (Diffuser Aging Monitoring Device). The radiometric model error due to the dark current nonlinearity is considered as a systematic error. Also the offset correction error due to gain/offset instability is considered. The radiometric accuracy depends mainly on the ground characterization accuracies of solar diffuser and DAMD.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.5
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• pp.916-922
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• 2001

A medium access control protocol is proposed for integrated voice and data services in the packet CDMA network with a small coverage. Uplink channels are composed of time slots and multiple spreading codes for each slot. This protocol gives higher access priority to the delay-sensitive voice traffic than to the data traffic. During a talkspurt, voice terminals reserve a spreading code to transmit multiple voice packets. On the other hand, whenever generating a data packet, data terminals transmit a packet based on the status Information of spreading codes in the current slot, which is received from base station. In this protocol, voice packet does not come into collision with data packet. Therefore, this protocol can increase the maximum number of voice terminals.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.571-574
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• 2008

In this paper, we propose $256{\times}256$ pixel array fingerprint sensor with an advanced circuits for detecting. The pixel level simple detection circuit converts from a small and variable sensing current to binary voltage out effectively. We minimizes an electrostatic discharge(ESD) influence by applying an effective isolation structure. The sensor circuit blocks were designed and simulated in standard CMOS $0.35{\mu}m$ process. Full custom layout is performed in the unit sensor pixel and auto placement and routing is performed in the full chip.

• BMB Reports
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• v.44 no.1
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• pp.1-10
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• 2011

Inter-cellular communication via diffusible small molecules is a defining character not only of multicellular forms of life but also of single-celled organisms. A large number of bacterial genes are regulated by the change of chemical milieu mediated by the local population density of its own species or others. The cell density-dependent "autoinducer" molecules regulate the expression of those genes involved in genetic competence, biofilm formation and persistence, virulence, sporulation, bioluminescence, antibiotic production, and many others. Recent innovations in recombinant DNA technology and micro-/nano-fluidics systems render the genetic circuitry responsible for cell-to-cell communication feasible to and malleable via synthetic biological approaches. Here we review the current understanding of the molecular biology of bacterial intercellular communication and the novel experimental protocols and platforms used to investigate this phenomenon. A particular emphasis is given to the genetic regulatory circuits that provide the standard building blocks which constitute the syntax of the biochemical communication network. Thus, this review gives focus to the engineering principles necessary for rewiring bacterial chemo-communication for various applications, ranging from population-level gene expression control to the study of host-pathogen interactions.