• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.293-294
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• 2009

The spectral responsivity of solar cells has been measured under high background irradiance using an LED-based differential spectral responsivity Comparator (DSR-C). The comparator developed is fully automated and has some advantages: It does not need a chopper to modulate the light. Unlike the conventional method, it does not require a monochromator to select wavelength. It covers a wavelength range up to 1200 nm. The wavelength range of the comparator is limited by the spectral power distribution of the LEDs and the spectral responsivity of the standard detector. An active temperature control was utilized to meet the specified standard conditions of solar cell test. This work shows the effect of different levels of background irradiance on the spectral responsivity and the importance of same background irradiance for solar cell test as specified by the corresponding standard.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.9
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• pp.616-623
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• 2001

Effects of the grating period fluctuation on the wavelength distribution have been studied by an effective index transfer matrix method in quarter wavelength shifted (QWS) DFB lasers. The wavelength distribution is expressed by a probability density that is an analytical function of the correlation coefficient and normalized standard deviation of the grating period fluctuation. The probability density function of wavelength distribution is shown to be nearly Gaussian, and its standard deviation increases with normalized standard deviation of the grating period fluctuation, and decreases with the negative correlation between adjacent half-periods.

• Restorative Dentistry and Endodontics
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• v.26 no.2
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• pp.127-133
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• 2001

There are several factors affecting the effectiveness of polymerization of the esthetic restorative materials. Among those factors, the initiator. camphoroquinone has the unique characteristic. of which the light sensitivity is very dependent on the wavelength of blue light. Camphoroquinone shows the most light absorption ability in the wavelength range of 470nm. So most of clinically used light curing systems adopt this phenomenon as their polymerization mechanism. The most popular way of light curing system is standard 40 second curing. But the problem of standard curing technique shows the rapid increase of resin viscosity followed by the acceleration of polymerization and the limited resin flow, resulted in reduction of the physicalproperty of restoration by retained stress. The object of this study was to verify the effects of narrow-banded wavelength on the microhardness of the esthetic restorative materials. a composite resin and a compomer, using filters which have peak wave length of 430nm, 450nm, 470nm, respectively. The results were as follows: 1. All the experimental groups showed lower hardness value than the control group. 2. In DyractAP, the hardness value by wavelength showed the same changing pattern on both upper and lower surfaces. 3. In DenFil, the hardness value by wavelength showed different changing pattern on upper and lower surfaces. 4. The hardness ratio showed similar pattern to the hardness variation of lower surface. but there was no significant difference between measurement in 10 minutes and 3 days later, besides the increase of hardness value.

• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.329-330
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• 2008

We experimentally demonstrate resonant-wavelength control of a series of an Si-based photonic crystal nanocavity. The cavities show a linear dependence on these parameters, a 1 nm increase of lattice constant leading to 4.2 nm increase of the resonant wavelength. The results have a small standard deviation of wavelength 1.1 nm between samples on a single chip.

• Journal of Biosystems Engineering
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• v.23 no.6
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• pp.591-598
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• 1998

Light intensity and spectral characteristics of different types of fluorescent lamps were tested to investigate their possibility as the artificial lighting sources for the close illumination applied in the transplant production factory. Photosynthetic photon flux densitiy(PPF), illuminance and irradiance for all lamps decreased logarithmically with an increase of the vertical distance from the lighting source. The fluorescent lamp specially designed plant growth (PG lamp) showed a maximum spectral irradiance at the wavelength of 660nm. However, it showed lower irradiance than that of a standard fluorescent lamp at the range of wavelength between 500 and 600nm. On the other hand, PG lamp showed higher PPF and lower illuminance than those of the standard fluorescent lamp. The maximum peak of spectral characteristics for both of the single and twin three-bind fluorescent lamps was shorn at the wavelength of 545m and the next peaks were shown at the wavelength of 610nm and 435nm, respectively. Since the red fluorescent lamp has a narrower peak at the wavelength of 660nm, it may be useful for the supplementary red lighting. For three of standard, single three-band and twin three-band fluorescent lamps, the values of conversion factor for converting illuminance to PPF fell within the narrow range from 76 to 791x/$\mu$molㆍm$^{-2}$ ㆍs$^{-l}$ . However, for PG lamp, it was 29.71x/$\mu$molㆍm$^{-2}$ ㆍs$^{-1}$. Also, the values of conversion factor for converting PPF to irradiance of fluorescent lamp used in this study ranged between 4.85 and 5.34$\mu$molㆍm$^{-2}$ ㆍs$^{-1}$/Wㆍm$^{-2}$ .

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.123-127
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• 2002

We have measured the wavelengths of the absorption lines of the $^{13}$ C$_2$H$_2$molecule by using a wavelength meter calibrated against the national optical frequency standard (iodine Stabilized He-Ne Laser, KRISS-R701) in the visible wavelength region. To measure the absolute wavelengths of the absorption lines, the frequency of the laser has been stabilized in the peaks and the sides of the absorption lines of $^{13}$ C$_2$H$_2$. Also, we have proposed the development of a frequency standard source of ITU-T grid using stabilization in the sides of the absorption lines of $^{13}$ C$_2$H$_2$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.67-76
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• 1989

Although the standard 2-CR network filter, one of the filters used for measuring surface roughness, is being used widely in the field of industry it possesses a weak point of causing Phase-distortion when the wavelength is passing through. Phase-corrected filter is used for eliminating these phase-distortion and the difference of phase characteristics between these two filters is thought to have considerable amount of effect on the surface roughness value. Moveover, the definition on this is as yet unclear. Therefore, the Rt and Rz value, obtained when the wavelength are passed through the standard and phase-corrected filters from the same random machine-processed surface, and its standard deviation are compared and experimented in this paper. Also, the ratio of relative bearing curve complying to the phase characteristics of these two filters are acquired. As a result, the use of phese-corrected filter is appropriate in experiments where the form of wavelength is important, and the standard deviation on the same experimented values appeared greater with when using the standard filter. The rate of relative bearing curve became greater as .lambda.$_{c}$, the cut-off value of filter, became smaller.r.

• Near Infrared Analysis
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• v.1 no.1
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• pp.1-7
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• 2000

A convenient algorithm for optimizing wavelength selection in multiple linear regression (MLR) has been developed. MOP (MLP Optimization Program) has been developed to test all possible MLR calibration models in a given spectral range and finally find an optimal MLR model with external validation capability. MOP generates all calibration models from all possible combinations of wavelength, and simultaneously calculates SEC (Standard Error of Calibration) and SEV (Standard Error of Validation) by predicting samples in a validation data set. Finally, with determined SEC and SEV, it calculates another parameter called SAD (Sum of SEC, SEV, and Absolute Difference between SEC and SEV: sum(SEC+SEV+Abs(SEC-SEV)). SAD is an useful parameter to find an optimal calibration model without over-fitting by simultaneously evaluating SEC, SEV, and difference of error between calibration and validation. The calibration model corresponding to the smallest SAD value is chosen as an optimum because the errors in both calibration and validation are minimal as well as similar in scale. To evaluate the capability of MOP, the determination of benzene content in unleaded gasoline has been examined. MOP successfully found the optimal calibration model and showed the better calibration and independent prediction performance compared to conventional MLR calibration.

• Publications of The Korean Astronomical Society
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• v.12 no.1
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• pp.167-172
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• 1997

Detailed low spectral resolution observations of the spectrum have been made for three early spectral type standard stars, HR718, HR1544, HR3454, respectively, for the wavelength region 4,300 A to 7,500 A, using the Bohyunsan Optical Astronomy Observatory (BOAO) Middle- Dispersion Spectrograph. These standard stars were chosen from well-known bright northern standard stars. All of the observed long slit spectral data has been reduced and analyzed using the IRAF reduction procedure. The derived extinction coefficients are compared with the other observatory result. The derived value can be used in the determination of flux calibration of BOAO spectroscopic observation. However, until the high quality data are secured from a new series of observation in the blue region and are re-analyzed together, the extinction coefficients below the 4,000 A wavelength remains unknown.

• Journal of Soil and Groundwater Environment
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• v.17 no.3
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• pp.1-9
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• 2012

According to the agreement on WTO/TBT, we are under the situation to adopt international standard (ISO standard) as a national standard if it exists. However, in case of environmental area, it is a domestic legal obligation to use Korean environmental standard method(KESM) for analyzing various contaminants. Therefore it is necessary to assess the comparability between KEM and ISO standard prior to apply ISO standard to soil conservation law in Korea. The main purpose of this study is to assess the comparability of both methods for analyzing heavy metals in soil. We looked over various aspects like pre-treatment, calibration curve range, detection wavelength, soil organic matter content and so on. Apparently, the procedure of both methods is almost same. However in details, both methods are different in stationary time before aqua-regia extraction using reflux system, calibration curve range for Cu, Pb, Ni and measuring wavelength for Pb. According to the results of comparison test, the results were significantly different when the different calibration range was used. In case that all the extracts independent of methods were reanalyzed with the same calibration range of each method, both methods showed statistically same results. Other conditions like different stationary time, measuring wavelength of AAS and soil organic matter content did not have any influence on the analytical result. Therefore, we suggest to extend the calibration curve range to 0~8 mg/L which is used in KS I ISO standard(Korean standard related with environment which is translation version of ISO standard without any technical change). In case of $Cr^{6+}$, the results showed no significant differences between two methods even though the pretreatment, instrumentation and other analysis conditions were different. In addition to UV/Visble spectrometry of KESM for soil contamination, we suggest to adopt ion chromatography of ISO 15192(US EPA method 7199) for analyzing $Cr^{6+}$ with the consideration of laboratory work efficiency.