• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.4
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• pp.49-55
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• 2004

This paper describes a 1550 nm multichannel source using Quatemary/quatemary multiple quantum well (MQW) InGaAsP/InGaAsP quantum confined Stark effect (QCSE) tuning for dense wavelength division multiplex (DWDM) systems with 140 ㎓ channel spacing and 32 nm channel selection bandwidth.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1729-1734
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• 2000

Complex dispersion relations in a cylindrical, foam-lined duct were successfully identified by using an iterative Prony series method. Techniques for using the iterative procedure successfully are described in detail, particularly with regard to model order selection and the identification of parameter starting values. It is shown that modal wave speeds and spatial attenuations per wavelength can be derived from the complex dispersion relations obtained using the iterative procedure. In addition, a finite element simulation is shown to well represent corresponding experimental measurement in terms of modal wave speeds and spatial attenuations.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.37.2-37.2
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• 2010

The IMS (Infrared or Intermediate-wide, Medium-deep Survey) program for the search of z~7 quasars has been running since last year. In order to discover enough number of quasars at z~7, a strategy sufficing both survey area (~150 square deg.) and image depth (23 AB mag in J filter), together with using existing multi-wavelength data is chosen. We have been carrying imaging observations with the UKIRT 4m telescope, now covering ~50 square deg. (including UKIDSS survey area) of J-band data. We then used selection in color-color space to choose high-z quasar candidates having the rest-frame Ly-alpha break, and to exclude contamination from stars and galaxies at low-z. We show quasar candidates of redshift z~7 and z~6, out of 25 square deg. data analyzed, and note implications and future plans.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.454-460
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• 2013

We present qualitative and quantitative component analyses on compound explosives via Terahertz time-domain spectroscopy (THz-TDS) based on a combination of wavelet thresholding and wavelength selection. Despite its importance, the field of signal processing of THz signals of compound plastic explosives is relatively unexplored. In this paper, experiment results from explosives Composition B-3 and Pentolite are newly presented, suggesting a novel signal processing procedure for in situ compound explosives detection. The proposed signal processing method demonstrates effective component analysis even in noisy and humid environments, showing significant decrease in component concentration percentage error of approximately 22.7% for Composition B-3 and 48.8% for Pentolite.

• Journal of Communications and Networks
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• v.6 no.2
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• pp.147-155
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• 2004

In this paper, we propose an efficient sequencing technique, namely minimum Row time scheduling (MFTS), to manage variable-Iength message transmissions for single-hop passive starcoupled WDM optical networks. By considering not only the message length but also the state of the receivers and the tuning latency, the proposed protocol can reduce the average delay of the network greatly. This paper also introduces a new channel assignment technique latency minimizing scheduling (LMS), which aims to reduce the scheduling latency. We evaluate the proposed algorithm, using extensive discrete-event simulations, by comparing its performance with shortest job first (SJF) algorithm. We find that significant improvement in average delay could be achieved by MFTS algorithm. By combining the proposed message sequencing technique with the channel selection technique, the performance of the optical network could be further improved.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1165-1171
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• 1999

The analysis of trace herbicides using the on-line SPE-HPLC system and a photochemical reaction was studied. 18 compounds of herbicides including eight triazines, six phenoxy acids and esters, and four other herbicides were examined. The on-line SPE-HPLC system developed for selection of eluting solvent improved chromatographic efficiency. The recoveries of herbicides were higher than 77%. With 100 mL tap water samples, the detection limits for all analytes were in the 0.1-2.3×10-10 M range. Detection was done by a UV or fluorescence spectrometer after photochemical reaction at the end of the column with 2W or 450W mercury lamp. Without a photochemical reaction, all compounds responded to 230 nm UV detector, but phenoxy acids and esters were weakly detected. However, with a photochemical reaction, these compounds were selectively detected at 320 nm wavelength of UV absorption and 400 nm emission of the fluorescence detectors. This method can be used for the analysis of environmental water containing herbicides at trace levels.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.6
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• pp.597-602
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• 2004

In practical applications of guided wave techniques, it is very important but also difficult to identify the propagating modes, and it is preferred to generate and detect a single or less dispersive mode. Also the noncontact method is required in the automated field application. So this paper considers a non-contact guided wave technique with enhanced mode-selectivity, where a laser beam illuminated through arrayed line slits is used as the transmitter and the air-coupled transducer is used as the receiver. The line arrayed laser illumination is a wavelength matching technique that ran generate only a few modes. The air-coupled transducer detects the leaky wave of the propagated guided wave, and by tuning its detection angle we ran detect the selected single mode. Experimental results for a 1mm thick aluminum plate proved the usefulness of the proposed method, and especially it was shown that this method was powerful in the generation and detection of the $a_0$ mode.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2002.11a
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• pp.59-62
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• 2002

Wavelength selection and prediction algorithm for determining hematocrit are investigated. A model based on the difference in optical density induced by the pulsation of heart beat is developed by taking approximation of Twersky's theory on the assumption that the variation of blood vessel size is small during arterial pulsing[1]. A device is constructed with a five-wavelength LED array as light source. The selected wavelengths are two isobestic points and three in compensation for tissue scattering. Data are collected from 549 out-patients who are randomly grouped as calibration and prediction sets. The range of percent hematocrit was 19.3∼51.8. The ratio of the variations of optical density between systole and diastole at two different wavelengths is used as a variable. We selected several such variables that show high reproducibility among all variables. Multiple linear regression analysis is made. The relative percent error is 8% and the standard deviation is 3.67 for the calibration set. The relative % error and standard deviation of the prediction set are 8.2% and 3.69 respectively. We successfully demonstrate the possibility of non-invasive hematocrit measurement, particularly, using the wavelengths below 1000nm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.951-958
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• 2000

In wavelength-routed all-optical networks, signals are transmitted on a direct optical path, or a lightpath, in a single-hop manner without opto-electronic/electro-optic(OE/EO) conversion at intermediate nodes. However, due to the physical constraints of optical elements such as ASE noise and crosstalk signals can be degraded un a long path. To establish a connection under such impairments, the optical signal may need to be regenerated at intermediate nodes, dividing a lightpath into two or more fragments. However, since signal regeneration at intermediate nodes requires additional network resources, the selection of these nodes should be made carefully to minimize blocking of other lightpaths. In this paper, we deal with the problem of establishing a lightpath in a multihop manner under physical constraints. We provide both minimal-cost and heuristic algorithms for locating signal regeneration nodes(SRNs). For a minimal-cost algorithm, we formulate the problem using dynamic programming(DP) such that blocking of other lightpaths due to the lack of transmitters/receivers(TXs/RXs) and wavelengths is minimized throughout the network.

• Journal of Advanced Navigation Technology
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• v.27 no.6
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• pp.855-860
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• 2023

Long-haul transmission of multiple transmission signals, such as wavelength division multiplexed (WDM), has became possible, because the signal distortion caused by chromatic dispersion and nonlinearity can be compensated by applying dispersion management, optical phase conjugation and combination of the two methods into the transmission link. The biggest obstacle to applying optical phase conjugation to an optical link is that the optical phase conjugator (OPC) must be located only in the middle of the entire transmission line. This paper shows that the location constraints of OPC can be overcome through the application of an asymmetric dispersion map. The location of the OPC considered in this paper exists between the 8th and 9th fiber spans out of a total of 48 fiber spans. Additionally, the dispersion map has an asymmetric cumulative dispersion profile with respect to the OPC. As a result of the simulation, it was confirmed that the distortion compensation effect of the WDM channel can be increased compared to the link to which the traditional dispersion map is applied, depending on the overall shape of the cumulative dispersion profile distribution of the proposed asymmetric dispersion map and the selection of the profile slope.