• Progress in Medical Physics
• /
• v.16 no.4
• /
• pp.166-175
• /
• 2005

The purpose of this study is to develop the optimization method for adjusting the film isocenter shift and to suggest the quantitative acceptable criteria for film dosimetry after optimization In the dynamic conformal arc radiation therapy (DCAR). The DCAR planning was peformed In 7 patients with brain metastasis. Both absolute dosimetry with ion chamber and relative film dosimetry were peformed throughout the DCAR using BrainLab's micro-multileaf collimator. An optimization method for obtaining the global minimum was used to adjust for the error in the film isocenter shift, which is the largest pan of systemic errors. The mean of point dose difference between measured value using ion chamber and calculated value acquired from planning system was $0.51{\pm}0.43\%$ and maximum was $1.14\%$ with absolute dosimetry These results were within the AAPM criteria of below $5\%$. The translation values of film isocenter shift with optimization were within ${\pm}$1 mm in all patients. The mean of average dose difference before and after optimization was $1.70{\pm}0.35\%$ and $1.34{\pm}0.20\%$, respectively, and the mean ratios over $5\%$ dose difference was $4.54{\pm}3.94\%$ and $0.11{\pm}0.12\%$, respectively. After optimization, the dose differences decreased dramatically and a ratio over $5\%$ dose difference and average dose difference was less than $2\%$. This optimization method is effective in adjusting the error of the film isocenter shift, which Is the largest part of systemic errors, and the results of this research suggested the quantitative acceptable criteria could be accurate and useful in clinical application of dosimetric verification using film dosimetry as follows; film isocenter shift with optimization should be within ${\pm}$1 mm, and a ratio over $5\%$ dose difference and average dose difference were less than $2\%$.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2000.11c
• /
• pp.698-706
• /
• 2000

It is very difficult to mechanize tomato harvesting because identifying a tomato partly covered with leaves and stalks is not easy. This research was conducted to develop tomato harvesting robot which can identify a target tomato, determine its three dimensional position, and harvest it in a limited time. Followings were major findings in this study. The first visual system of the harvesting robot was composed of two CCD cameras, however, this could not detect tomatoes which are not seen on the view finder of the camera especially those partly covered by leaves or stalks. The second visual device, combined with two CCD cameras and pan/tilt procedures was designed to minimize the positioning errors within ${\pm}10mm$, but this is still not enough to detect tomatoes partly covered with leaves etc. Finally, laser distance detector was added to the visual system that could reduce the position detecting errors within 10mm in X-Y direction and 5mm in Z direction for the partly covered tomatoes.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.8 no.4
• /
• pp.19-28
• /
• 1999

In order to control thermal deformation of the machine origin of machine tools a empirical model and a compensation system have been developed, Prior to empirical modeling the volumetric error considering shape errors and joint errors of slides is formulated through the homogeneous transformation matrix (HTM) and kinematic chain. Simulation results of the HTM method show that the thermal error of the machine origin is more critical than position-dependent errors. In order to make a stable and effective software error compensation system the GMDH (Group Method of Data Handling) models are constructed to estimate the thermal deformation of the machine origin by measuring deformation data and temperature data. A test bar and gap sensors are used to measure the deformation data. In order to compensate the estimated error the work origin shift method is developed by implementing a digital I/O interface board between a CNC controller and an IBM PC. The method shifts the work origin as much as the amounts which are calculated by the pre-established thermal error model. The experiment results for a vertical machining center show that the thermal deformation of the machine origin is reduced within $\pm$5$mu extrm{m}$.

• Journal of Korean Society of Forest Science
• /
• v.99 no.3
• /
• pp.285-291
• /
• 2010

Since 2006, the $5^{th}$ National Forest Inventory (NFI) has been implemented to provide forest resources statistics at the national level and at the county level as well. However, it needs a small-area estimator for estimating forest statistics at the county-level due to a small number of samples collected within a county. This study was conducted to evaluate the applicability of a geographical-based synthetic estimator for estimating forest growing stock volumes at the county level. The NFI-field plots surveyed were post-stratified into three forest cover types. In the synthetic estimator, field plots within a geographical-based super-county for each county were used to estimate stratum weights and stratum mean volumes. It was resulted that estimated stratum weights using the synthetic estimation were significantly differ from forest cover maps. The standard errors of estimated mean by the synthetic estimation that ranged from ${\pm}3.5\;m^3$/ha to ${\pm}7.7\;m^3$/ha were more smaller than those (${\pm}7.8\;m^3/ha{\sim}{\pm}24.7\;m^3/ha$) by the direct estimation. This means that the synthetic estimation is possible to provide more precise estimates of mean volumes.

• Journal of Astronomy and Space Sciences
• /
• v.17 no.2
• /
• pp.211-220
• /
• 2000

Korea Astronomy Observatory(KAO) is working to retrofit its 1m robotic telescope in collaboration with a company (ACE, Astronomical Consultants & Equipment). The telescope system is being totally refurbished to make a fully automatic telescope which can operate in both interactive and fully autonomous robotic modes. Progress has been made in design and manufacturing of the telescope mount, mechanics, and optical performance system tests are being made for re-configured primary and secondary mirrors. The optical system is designed to collect 80% incident light within 0.5 arcsec with f/7.5 Ritchey-Chretien design. The telescope mount is an equatorial fork with a friction drive system. The design allows fully programmable tracking speeds with typical range of 15 arcsec/sec with accuracy of $\pm5$ arcsec/hour. The mount system has integral pointing model software to correct for refraction, and all mechanical errors and misalignments. The pointing model will permit positioning to better than 30 arcsec RMS within $75^{\circ}$ from zenith and 45 arcsec RMS elsewhere on the sky. The software is designed for interactive, remote and robotic modes of operation. In interactive and remote mode the user can manually enter coordinates or retrieve them from a computer file. In robotic mode the telescope controller downloads the coordinates in the order determined by the scheduler. The telescope will be equipped with a CCD camera and will be accessible via the internet.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.14 no.3
• /
• pp.177-184
• /
• 1994

The three dimensional measuring method with minimizing operational errors for the arbitrary shaped-internal cavity based on the information of the X-ray nondestructive test is presented. Two experimental tests using artificial cavities were considered in order to verify the availity of PEVACA. In these test, X-ray NDT was conducted for detecting cavities, and the comparion between the calculating values from PEVACA and the real values from measuring the cavities was performed. As a result of this study, three dimensional cavities information using PEVACA are in good agreement with the real measured values within ${\pm}0.5mm$. The computer code, "PEVACA", contributes not only to improvement of data accuracy but also to saving of the work time and data documentation.

• Radiation Oncology Journal
• /
• v.22 no.2
• /
• pp.155-163
• /
• 2004

Purpose : To confirm the reproducibility of in vivo transmission dosimetry system and the accuracy of the a1gorithms for the estimation of transmission dose in head and neck radiation therapy patients. Materials and Methods : From September 5 to 18, 2001, transmission dose measurements were peformed when radiotherapy was given to brain or head and neck cancer patients. The data of 35 patients who were treated more than three times and whose central axis of the beam was not blocked were analyzed in this study. To confirm the reproducibility of this system, transmission dose was measured before dally treatment and then repetitively every hour during the treatment time, with a field size of 10$\times$10 cm$^{2}$ and a delivery of 100 MU. The accuracy of the transmission dose calculation algorithms was confirmed by comparing estimated dose with measured dose. To accurately estimate transmission dose, tissue inhomogeneity correction was done. Results : The measurement variations during a day were within $\pm$0.5$\%$ and the dally variations in the checked period were within $\pm$ 1.0$\%$, which were acceptable for system reproducibility. The mean errors between estimated and measured doses were within $\pm$5.0$\%$ in Patients treated to the brain, $\pm$2.5$\%$ in head, and $\pm$ 5.0%$\%$in neck. Conclusion : The results of this study confirmed the reproducibility of our system and its usefulness and accuracy for dally treatment. We also found that tissue inhomogeneity correction was necessary for the accurate estimation of transmission dose in patients treated to the head and neck.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.29 no.2
• /
• pp.201-208
• /
• 2011

With the increase in the number of smartphone users, precise 3D positional information is required by various applications. The positioning accuracy using civilian single-frequency pseudoranges is at the level of 10 m or so, but most applications these days are asking for a sub-meter level Therefore, instead of an absolute positioning technique, the VRS-based differential approach is applied along with the correction of the double-differenced (DD) residual errors using FKP (Flachen-Korrektur-Parameter). The VRS (Virual Reference Station) is located close to the rover, and the measurements are generated by correcting the geometrical distance to those of the master reference station. Since the unmodeled errors are generally proportional to the length of the baselines, the correction parameters are estimated by fitting a plane to the DD pseudorange errors of the CORS network. The DD positioning accuracy using 24 hours of C/A code measurements provides the RMS errors of 37 cm, 28 cm for latitudinal and longitudinal direction, respectively, and 76 cm for height. The accuracy of the horizontal components is within ${\pm}0.5m$ for about 90% of total epochs, and in particular the biases are significantly decreased to the level of 2-3 cm due to the network-based error modeling. Consequently, it is possible to consistently achieve a sub-meter level accuracy from the single-frequency pseudoranges using the VRS and double-differenced error modeling.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.145-150
• /
• 2003

In this paper we have studied the characteristics of temperature fields in a Molded Case Circuit Breaker (MCCB). A switch and a trip device are arranged in narrow space of the MCCB. Thus, thermal factors have been risen to important problem. The temperature rise means an energy loss and it becomes the reason of fatal fault in devices. Also, the temperature rise on the connection and the contact parts is regulated up to $115^{\circ}C$ and $105^{\circ}C$, respectively. Therefore, a study for preventing the temperature rise should be investigated. A numerical analysis method that has confidence might be preceded for this purpose. In order to verify the confidence of temperature field analysis, the results of the numerical analysis are compared with those of experimental one for the same model. Comparison results show a qualitatively good agreement within ${\pm}5%$ errors.

• Journal of Radiation Protection and Research
• /
• v.28 no.1
• /
• pp.59-63
• /
• 2003

Purpose : Measurement of transmission dose is useful for in vivo dosimetry of QA purpose. The objective of this study is to develope an algorithm for estimation of tumor dose using measured transmission dose for open radiation field. Materials and Methods : Transmission dose was measured with various field size (FS), phantom thickness (Tp), and phantom chamber distance (PCD) with a acrylic phantom for 6 MV and 10 MV X-ray Source to chamber distance (SCD) was set to 150 cm. Measurement was conducted with a 0.6 cc Farmer type ion chamber. Using measured data and regression analysis, an algorithm was developed for estimation of expected reading of transmission dose. Accuracy of the algorithm was tested with flat solid phantom with various settings. Results : The algorithm consisted of quadratic function of log(A/P) (where A/P is area-perimeter ratio) and tertiary function of PCD. The algorithm could estimate dose with very high accuracy for open square field, with errors within ${\pm}0.5%$. For elongated radiation field, the errors were limited to ${\pm}1.0%$. Conclusion : The developed algorithm can accurately estimate the transmission dose in open radiation fields with various treatment settings.