• Journal of Korean Society for Atmospheric Environment
• /
• v.21 no.E2
• /
• pp.49-56
• /
• 2005

A long-path transmissometer is one of the optical instruments widely used to measure atmospheric light extinction coefficient without enclosing a light beam and perturbing aerosols. Over the past two decades, a number of measurements have been carried out using the long-path transmissometer manufactured by OPTEC, Inc. Calibration of the transmissometer should be performed when any component of the transmissometer system is interchanged or installation condition is changed. For a better calibration of the transmissometer, application of a modified calibration method for the existing neutral density (ND)-filter method was recommended for the computation of the atmospheric transmittance using model MODTRAN 4 in this study. It was revealed that the measured light extinction coefficient from the transmissometer which was calibrated using the existing ND-filter method could be overestimated due to the assumption of the atmospheric transmittance suggested by OPTEC, Inc. The uncertainty of the measured light extinction coefficient from the transmissometer calibrated based on the modified ND-filter method was calculated to be approximately $13Mm^{-1}$.

• Communications for Statistical Applications and Methods
• /
• v.25 no.5
• /
• pp.545-557
• /
• 2018

The inclusion of covariates in the model often affects not only the estimates of meaningful variables of interest but also its statistical significance. Such gap between statistical and subject-matter significance is a critical issue in huge sample studies. A popular huge sample study, the sample cohort data from Korean National Health Insurance Service, showed such gap of significance in the inference for the effect of obesity on cause of mortality, requiring careful consideration. In this regard, this paper proposes a sample size calibration method based on a Monte Carlo t (or z)-test approach without Monte Carlo simulation, and also proposes a test procedure for subject-matter significance using this calibration method in order to complement the deflated p-value in the huge sample size. Our calibration method shows no subject-matter significance of the obesity paradox regardless of race, sex, and age groups, unlike traditional statistical suggestions based on p-values.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.33B no.7
• /
• pp.127-137
• /
• 1996

The 3-dimensional measurement using stereo vision system must achieve a camera calibration. So far, the 3-dimensional calibration technique that uses two-dimensional grid papar and a non-linear least square method has been developed and tested. But, this method is inefficient because it has many calculation procedure and a non-linear analysis. Therefore, this paper proposed the projective geometric method which produced the calibration parameter by vanishing point. The vanishing point is producted by a cross ratio and a parallel line pairs. The results of the computer simulation show utility of the proposed method.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.1278-1284
• /
• 2008

This study carried out bender element tests in a calibration chamber in order to estimate the characteristics of soil specimen prepared in a calibration chamber. Basically, the purpose of bender element test is to measure the shear wave velocity. Bender element test cannot only confirm the status of soil specimen deposited in a chamber, but also estimate the consolidation process indirectly. In order to carry out bender element test in a calibration chamber, a pair of bender elements was installed inside the chamber, using the 'ㄷ' shaped frame. For the sandy soils having various relative densities in various stress conditions, the maximum shear modulus was estimated. From the comparison with bender element test results in a triaxial testing device, testing device and procedure was validated.

• Proceedings of the KIEE Conference
• /
• 2003.07d
• /
• pp.2020-2021
• /
• 2003

Korea Research Institute of Standards and Science (KRISS) has developed a Web-based, remote, Internet calibration system to calibrate the Fluke 5700A/5720A calibrator using a transportable standard: specifically, multifunction transfer standard 4950. Although the uncertainty for the Internet calibration is up to two times larger than that using conventional manual calibration, it has many advantages: no need to transport the customer equipment, a reduction in the calibration service time, a directly enforced traceability to the national standards, convenience, and ease of use for the customers.

• Bulletin of the Korean Chemical Society
• /
• v.22 no.1
• /
• pp.37-42
• /
• 2001

Ridge regression is compared with multiple linear regression (MLR) for determination of Research Octane Number (RON) when the baseline and signal-to-noise ratio are varied. MLR analysis of near-infrared (NIR) spectroscopic data usually encounters a collinearity problem, which adversely affects long-term prediction performance. The collinearity problem can be eliminated or greatly improved by using ridge regression, which is a biased estimation method. To evaluate the robustness of each calibration, the calibration models developed by both calibration methods were used to predict RONs of gasoline spectra in which the baseline and signal-to-noise ratio were varied. The prediction results of a ridge calibration model showed more stable prediction performance as compared to that of MLR, especially when the spectral baselines were varied. . In conclusion, ridge regression is shown to be a viable method for calibration of RON with the NIR data when only a few wavelengths are available such as hand-carry device using a few diodes.

• Geomechanics and Engineering
• /
• v.2 no.3
• /
• pp.177-190
• /
• 2010

This paper presents the details of indigenous development of the piezovibrocone and calibration chamber. The developed cone has a cylindrical friction sleeve of $150cm^2$ surface area, capped with a $60^{\circ}$ apex angle conical tip of $15cm^2$ cross sectional area. It has a hydraulic shaker, coupled to the cone penetrometer with a linear displacement unit. The hydraulic shaker can produce cyclic load in different types of wave forms (sine, Hover sine, triangular, rectangular and external wave) at a range of frequency 1-10 Hz with maximum amplitude of 10 cm. The piezovibrocone can be driven at the standard rate of 2 cm/sec using a loading unit of 10 ton capacity. The calibration chamber is of size $2m{\times}2m{\times}2m$. The sides of the chamber and the top as well as the bottom portions are rigid. It has a provision to apply confining pressure (to a maximum value of $4kg/cm^2$) through the flexible rubber membrane inlined with the side walls of the calibration chamber. The preliminary static as well as dynamic cone penetration tests have been done sand in the calibration chamber. From the experimental results, an attempt has been made to classify the soil based on friction ratio ($f_R$) and the cone tip resistance ($q_c$).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.1
• /
• pp.27-38
• /
• 2002

The effects of Reynolds number on the non-nulling calibrations of a cone-type ave-type probe in low-speed flows have been investigated at Reynolds numbers of 2.04$\times$10$^3$, 4.09$\times$10$^3$and 6.13$\times$10$^3$. The calibration is conducted at the pitch and yaw angles in ranges between -35 degrees and 35 degrees with an angle interval of 5 degrees. In addition to the calibration coefficients, reduced pitch and yaw angles, static and total pressures, and velocity magnitude are obtained through a typical non-nulling reduction procedure. The result shows that each calibration coefficient, in general, is a function of both the pitch and yaw angles, so that the pre-existing calibration data in a nulling mode are not enough in accounting far the full non-nulling calibration characteristics. Due to interference of the probe stem, the calibration coefficient are more sensitive to Reynolds number at positive pitch angles than at negative ones. The calibration data reduced in this study may serve as a guide line in the estimation of uncertainty intervals resulted from the Reynolds number effects at low Reynolds numbers.

• The Journal of the Korea Contents Association
• /
• v.10 no.6
• /
• pp.10-17
• /
• 2010

This paper presents a calibration method of an omnidirectional stereo camera which may be essentially performed for distance measurement to a certain point. In the calibration of the omnidirectional stereo camera, the independent calibrations of two cameras or the calibration of a stereo camera having the small baseline is feasible applying many methods studied in the past. However, the baseline should be large enough for long distance measurement by the omnidirectional stereo camera, since it is not easy to calibrate two cameras with a large baseline at the same time. It is because a test pattern for the calibration, which is simultaneously captured by two omnidirectional cameras, appears too small in at least one of the omnidirectional cameras. It causes inaccurate calibration. In this paper, therefore, we propose a calibration method of the omnidirectional stereo camera with a large baseline and empirically verify its feasibility.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.1679-1683
• /
• 1997

In this paper a linear Kalman filter for calibration of gimballed inertial navigation system(GINS) is designed and its performace is analyzed through the simulation with a real navigation data. Simulation results show that the proposed Kalman filter gives a good performance to calibrate the sensor errors.