• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.33-34
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• 2006

• Atmosphere
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• v.15 no.4
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• pp.203-211
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• 2005

One algorithm has been developed for retrieving aerosol optical thickness from GMS-5 visible channel measurements, and then the algorithm was applied for obtaining the geographical distribution of aerosol optical thickness over East Asia during April 2002. Algorithm employs a look-up table based upon radiative transfer calculations with solar geometry, aerosol optical thickness, and surface albedo as inputs. Validation was conducted by comparing retrieved aerosol optical thickness with measured values from ground-based sky radiation measurements at Anmyon Do, Korea. It was found that the correlation coefficient is 0.71 with -0.03 of bias and 0.34 of root mean square error, suggesting that the algorithm developed in this study can be used for estimating aerosol optical thickness in a quantitative sense.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.4
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• pp.1-5
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• 2011

A new code structure for spectral-amplitude-coding optical CDMA based upon reconstructed modified double weight codes is proposed. The newly proposed code possesses ideal cross-correlation properties. By using fiber Bragg grating(FBG) in front of optical decoder, we can get the improved performance of the proposed system with the consideration of phase-induced intensity noise(PIIN).

• Proceedings of the Korean Environmental Health Society Conference
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• 2002.04a
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• pp.44-46
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• 2002

This study was conducted to identify the proper analytical conditions regarding optical density for endotoxin analysis in the workplace using metalworking fludis. Our study found the "onset method" was more accurate than "time to Vmax" Reproducibility and accuracy analyzed by "onset method" was more greater than those by "time to Vmax""0.03"of optical density was the most appropriate analytical condition among onset method. Through this analytical condition, 0.998 of linearity was obtained and recovery rate ranged from 88％ to 105％ at endotoxin concentration below 5 EU/$m\ell$. No significant difference of endotoxins between "0.03"and "0.05" of optical density was observed from this study. Furthermore, correlation coefficients between them were statistically significant(p＜0.01). This study concluded that 0.03”or "0.05" of optical density is used to analyze endotoxin. Of these optical density value, value with higher linearity should be used to analyze endotoxin in environmental samples.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1134-1141
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• 1999

In this paper, we implement an optical code division multiple access(OCDMA) system and analyze the performance of the implemented system. In the implemented system, a transmitter encodes input data into optical pulses by using laser diode, and spreads the encoded pulses in an encoder which consists of 4 stage delay lines. The decoder which is the same structure as that of encoder delays and combines the spreaded pulses, and thus recovers the original data. At first, we discuss the auto- and cross-correlations of OCDMA signals under both environments of single user and multi-users, and then verify the simulation results with experimental results. We also evaluate the effect of a number of stages of delay line and code length on the system performance through computer simulations. As experimental results we can see that if the decoder have the same configuration as that of encoder, the peak auto-correlation characteristics can be achieved, and thus we can recover the original data from received data. As simulation results we can see that although bit error rate decreases as code length decreases or the number of stage of delay line increases, it is difficult to implement the system because the pulse width becomes narrow. From the results, we can apply CDMA technologies to optical communication networks.

• Journal of Power System Engineering
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• v.19 no.3
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• pp.11-15
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• 2015

In this paper, the multi-point hydrogen detection system based on the combination of the hetero-core optical fiber SPR hydrogen tip sensor and interrogator by pseudorandom noise (PN) code correlation reflectometry has been developed. In a light intensity-based experiment with an LED operating at 850 nm, it has been presented that a transmitted loss change of 0.32dB was induced with a response time of 25 s for 4% $H_2$ in $N_2$ in the case of the 25-nm Au, 60-nm $Ta_2O_5$, and 5-nm Pd multi-layers film. The proposed sensor characteristic shows excellent reproducibility in terms of loss level and time response for the in- and out- $H_2$ action. In addition, in the experiment for multi-point hydrogen detection, all sensors show the real-time response for 4% hydrogen adding with reproducible working. As a result, the real-time multi-point hydrogen detection could be realized by means of the combination of interrogating system and hetero-core optical fiber SPR hydrogen tip sensors.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.1
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• pp.1-8
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• 2016

Optical particle sizer (OPS), optical particle counter (OPC), and aethalomter were deployed to measure the particle number concentrations from 0.3 to $10.0{\mu}m$ and black carbon (BC) concentrations. Comparisons of particle number concentrations measured by OPS and OPC were conducted to evaluate the performance of the each optical instrument at the Gwangju sampling site ($35.23^{\circ}N$, $126.84^{\circ}E$) for 14 days from Dec. 27 in 2014. Although a good correlation ($r^2=0.99$) between the OPS and OPC was observed for both the particle number and volume concentrations, different relationships by BC concentrations can be associated with the intensities by different light scattering angles. In addition, based on diurnal patterns of size distributions in 24 hr running correlation coefficient determination, BC concentrations were highly related to the particles less than $0.3{\mu}m$ observed in the morning traffic hour.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1C
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• pp.1-5
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• 2008

Optical code division multiple access(OCDMA) systems make the active users to share the bandwidth by simply assigning distinct optical orthogonal codeword to each active user. An optical orthogonal code(OOC) is a collection of binary sequences with good correlation properties which are important factors of determining the capacity of OCDMA systems. Recently, 2-D OOC construction method is frequently researched which is able to support more users than 1-D OOC. In this paper, a combinatorial construction of simple multi-weight 2-D OOC with autocorrelation 0 and crosscorrelation 1 is proposed and the bound on the size of these codes is derived.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.7
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• pp.749-757
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• 1992

In this paper, as a more effective approach for maneuvering target tracking a realtime optical tracking system based of optical JTC(Joint Transform Correlator) which is capable of transforming the massive input target data into a few correlation peaks is implemented. And for real-time implementation the high resolution LCD(Liquid Crystal Display) spatialight modulator is used to construct the optical JTC system, and the mean binarization method is used to reduce the effects of background noises on correlation signal. From the good experimental results on maneuvering targets, the possibility of real-time moving target tarcking system based on optical JTC is a suggested.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.6
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• pp.1070-1074
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• 2008

Body fat correlation formula induced by using optical method was used white light LED source and electrical method used BIA(Bio-electrical Impedance Analysis) method measured at same time. In the case of BIA method confirmed phase difference of 6 degree and voltage drop of 2.7V at 5V and 50kHz's input signal. In the case of optical method confirmed that optical intensity increased by order of the biceps, the fleshy inside of the thigh and the triceps. We obtained percent body fat of 20% with the body fat correlation formula induced by photo-electricity method.