• Journal of the Korean Society of Radiology
• /
• v.17 no.4
• /
• pp.531-539
• /
• 2023

Self-absorption is the most important factor affecting the accuracy of gamma spectroscopy measurements in environmental samples. In particular, it is affected by other factors such as the chemical composition of the sample, geometric shape, thickness, density, atomic number, distance between the sample and detector, energy of the emitted gamma photon, and humidity coefficient or percentage in the sample. To test the calibration method, a 450 ml CRM standard source (9 nuclide) Marinelli beaker was used. Five soil samples among environmental samples were measured by density by applying the corrected values. Therefore, it can be seen that the self-absorption value is more effective for somewhat large and low photon energy. In the case of environmental samples, it was confirmed that the overall energy peak efficiency through self-absorption of the source greatly depends on the density of the sample.

• Journal of Drive and Control
• /
• v.18 no.1
• /
• pp.31-38
• /
• 2021

This study presents a new principle for driving the robot aimed at reducing the position error for the boresonic examination of turbine rotor. The conventional method of inspection is performed by installing manipulator onto the flange of the turbine rotor and connecting a pipe, which is then being pushed into the bore. The longer the pipe gets, the greater sagging and distortion appear, making it difficult for the ultrasonic sensor to contact with the internal surface of the bore. A pneumatic pressure will ensure the front or rear feet of the robot in close contact with the inner wall to prevent slipping, while the ball screw on the body of the robot will rotate to drive it in the axial direction. The compression force required for tight contact was calculated in the form of a three-point support, and a static structural simulation analysis was performed by designing and modeling the robot mechanism. The driving performance and ultrasonic detection ability have been tested by fabricating the robot, the test piece for ultrasonic calibration and the transparent mock-up for robot demonstration. The tests have confirmed that no slipping occurs at a certain pneumatic pressure or over.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.38 no.7
• /
• pp.22-27
• /
• 2001

In this paper, the complex permittivity of various dielectrics such as powder(sugar and flour) and solid(teflon and acrvl) are measured by using an open ended coaxial-line probe, which is self designed and manufactured, The probe is connected to a vector network analyzer(VNA) through a coaxial cable, The end of the cable is corrected by using an OSL(open, short, and load) calibration kit, The phase difference, which is produced by inserting the probe at the end of the line. is compensated by using the numerically calculated reflection coefficient of distilled water, The complex permittivity is reconstructed by inserting the measured reflection coefficient, which is produced at the interface between the probe and measuring material, into ,an virtual conical cable conversion model. Over a wide frequency range from 30 MHz to 3 GHz, the measured complex permittivitis of various powder and solid using the our method are compared with the results, which are measured by using an transmission-line method of the Korea Research Institute of Standards and Science(KRISS).

• Journal of KIISE:Computer Systems and Theory
• /
• v.32 no.1
• /
• pp.1-8
• /
• 2005

Image morphing to generate 2D transitions between images may be difficult even to express simple 3D transformations. In addition, previous view morphing method requires control points for postwarping, and is much affected by self- occlusion. This paper presents a new morphing algorithm that can generate automatically in-between scenes from un-calibrated images. Our algorithm rectifies input images based on the fundamental matrix, which is followed by linear interpolation with bilinear disparity map. In final, we generate in-between views by inverse mapping of homography between the rectified images. The proposed method nay be applied to photographs and drawings, because neither knowledge of 3D shape nor camera calibration, which is complex process generally, is required. The generated in-between views can be used in various application areas such as simulation system of virtual environment and image communication.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.49 no.2
• /
• pp.130-136
• /
• 2012

In this paper, we propose a near-field range estimation method for a uniform linear array that can calibrate bearing estimation error which give a bad influence on a range estimation process. When a range is fixed, the bearing error is calibrated to maximize the beamformer output by the proposed algorithm based on the gradient method. Simulation results show that the proposed algorithm can compensate the bearing error which is less than the mainlobe beamwidth so that reduce the range estimation error as similar as the case of no bearing error.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.43 no.3
• /
• pp.337-352
• /
• 2023

In general, Rainfall-Runoff model parameter set is optimized using the entire data to calculate unique parameter set. However, Korea has a large precipitation deviation according to the season, and it is expected to even worsen due to climate change. Therefore, the need for hydrological data considering seasonal characteristics. In this study, we conducted regional sensitivity analysis(RSA) using the conceptual Rainfall-Runoff model, GR4J aimed at the Soyanggang dam basin, and clustered combining the RSA results with hydrometeorological data using Self-Organizing map(SOM). In order to consider the climate characteristics in parameter estimation, the data was divided based on clustering, and a calibration approach of the Rainfall-Runoff model was developed by comparing the objective functions of the Global Optimization method. The performance of calibration was evaluated by statistical techniques. As a result, it was confirmed that the model performance during the Cold period(November~April) with a relatively low flow rate was improved. This is expected to improve the performance and predictability of the hydrological model for areas that have a large precipitation deviation such as Monsoon climate.

• The KIPS Transactions:PartB
• /
• v.12B no.4 s.100
• /
• pp.387-394
• /
• 2005

This paper describes an idea for determining self-localization using visual landmark. The critical geometric dimensions of a pentagon are used here to locate the relative position of the mobile robot with respect to the pattern. This method has the advantages of simplicity and flexibility. This pentagon is also provided nth a unique identification, using invariant features and colors that enable the system to find the absolute location of the patterns. This algorithm determines both the correspondence between observed landmarks and a stored sequence, computes the absolute location of the observer using those correspondences, and calculates relative position from a pentagon using its (ive vortices. The algorithm has been implemented and tested. In several trials it computes location accurate to within 5 centimeters in less than 0.3 second.

• Journal of the Korean Society for Precision Engineering
• /
• v.31 no.7
• /
• pp.605-613
• /
• 2014

Scanning white-light interferometry is an important measurement option for many surfaces. However, serious profile measurement errors can be present when measuring free-form surfaces being highly curved or tilted. When the object surface slope is not zero, the object and reference rays are no longer common path and optical aberrations impact the measurement. Aberrations mainly occur at the beam splitter in the interference objective and from misalignment in the optical system. Both effects distort the white-light interference signal when the surface slope is not zero. In this paper, we describe a modified version of white-light interferometry for eliminating these measurement errors and improving the accuracy of white-light interferometry. Moreover, we report systematic errors that are caused by optical aberrations when the object is not flat, and compare our proposed method with the conventional processing algorithm using the random ball test.

• Journal of Astronomy and Space Sciences
• /
• v.12 no.1
• /
• pp.66-77
• /
• 1995

It is possible to distinguish X-ray events from non X-ray events in proportional conters using the method of rise time discrimination (RTD). In order to subtract non X-ray background, we have developed a simple RTD circuit which will be applied to the proportional counter planned for a sounding rocket experiment. The entire circuit consists of two parts ; the rise time measurement circuit and the time to amplitude conversion circuit which includes the self-calibration mode. From the test with X-ray detecting system, we obtained that the background can be rejected more than 80% in the energy band 2∼12 keV. However we confirmed that the RDT method is not proper to be used for the energy range above 12kV.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.9 no.1
• /
• pp.47-54
• /
• 1991

In this study, the accuracy of three dimensional location was improved by self calibration bundle method with additional parameter, which is to correct systematic error through detection and elimination of the gross error from updated reference variance for observation values in photogram-metry. In this study, with the result of comparing accuracy of each method, correcting systematic error is more effective after gross error detection and when observation values are contained more than two gross error the point with maximum correlation value is detected by masking effect of least square adjustment.