• Progress in Medical Physics
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• v.11 no.2
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• pp.117-122
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• 2000

The IP(imaging plate) has been widely used to measure the two-dimensional distribution of incident radiation since it has a high sensitivity, reusability, a wide dynamic range, a high position resolution. Particularly, the easiness of acquiring digitized image using IP poses a strong merit because recent trend of data handling prefers image digitization. In order to test its usefulness in photon beam dosimetry, we measured the off-axis ratio(OAR) on portal planes and percent depth dose(PDD) within a phantom using IP, and compared the results with the data based on EGS4 Monte Carlo particle transport code, ion-chambers, conventional films. For the measurement, we used 6 MV X-rays, various field sizes. As a result, IP showed significant deviation from ion-chamber measurement: a significant overresponse, 100% greater than that of ion-chamber measurement at deep part of the phantom. Filtration of low-energy scattered photons at deep part of the phantom using 0.5 mm thick lead sheets did improve the result, only to the unacceptable extent. However, portal dose measurement showed possibilities of If as a dosimeter by showing errors less than 5%, as compared with film measurement.

• Environmental and Resource Economics Review
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• v.15 no.4
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• pp.673-692
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• 2006

In order to test for the dynamic optimality condition for the use of nonrenewable resource, it is necessary to estimate the shadow value of the resource in situ. In the previous literatures, a time series for in situ price has been derived either as the difference between marginal revenue and marginal cost or by differentiating with respect to the quantity of ore extracted the restricted cost function in which the quantity of ore is quasi-fixed. However, not only inconsistent estimates are likely to be generated due to the nonmalleability of capital, but the estimate of marginal revenue will be affected by market power. Since firms will likely fail to minimize the cost of the reproducible inputs subject to market prices under realistic circumstances where imperfect factor markets, strikes, or government regulations are present, the shadow in situ values obtained by estimating the restricted cost function can be biased. This paper provides a valid methodology for checking the dynamic optimality condition for a nonrenewable resource by using the input distance function. Our methodology has some advantages over previous ones: only data on quantities of inputs and outputs are required; nor is the maintained hypothesis of cost minimization required; adoption of linear programming enables us to circumvent autocorrelated errors problem caused by use of time series or panel data. The dynamic optimality condition for domestic coal mining does not hold for constant discount rates ranging from 2 to 20 percent over the period 1970~1993. The dynamic optimality condition also does not hold for variable rates ranging from fourth to four times the real interest rate.

• Journal of KIISE:Software and Applications
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• v.37 no.4
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• pp.323-339
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• 2010

The complexity of embedded systems and the effort to develop them has been rising in proportion with their importance. Also, the heterogeneity of the hardware and software parts in embedded systems makes it more challenging to develop. Errors caused by hardware/software interfaces, especially, account for up to 13 percent of failures with an increasing trend. Therefore, verifying the interface between hardware and software in embedded system is one of the most important research areas. However, current approaches such as co-simulation method and model checking have explicit limitations. In this paper, we propose the synthesizable interface co-verification framework for hardware/software co-design. Firstly, we introduce the separate interface specifications for the heterogeneous components to describe hardware design and software design. Our specifications are expressive enough to describe both. We also provide the transformation rules from the software specification to the hardware specification so that the whole system can be described from the software view. Secondly, we address the solution of verifying the interface of the software and hardware design by adopting and extending existing verification-techniques and extending them. In hardware interface verification, we exploit the model checking technique and provide more efficient verification by closing the hardware design from the assumption of the software behavior which is ensured by software verification step. Lastly, we generate the interface codes such as device APIs, device driver, and device controller from the specification so that verified hardware and software codes can be synthesized without extra efforts.

• Korean Journal of Construction Engineering and Management
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• v.11 no.6
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• pp.122-130
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• 2010

Seventy percent of Korea's national territory is covered with mountains, and the land is frequently exposed to typhoons and localized torrential downpours, particularly in July through September. For this reason, slope failure is one of the most frequent types of natural disasters in Korea. To prevent the damage caused by slope failure, the Korean government, academia and industry have strived together to develop and install a wired system for monitoring slope failures. However, conventional wired monitoring systems have been reported to have limitations, such as possible system errors caused by lightning, and the difficulties of restoration and management of the systems. To solve these problems, this research suggests a USN-based monitoring system for slope failures. First, the trend of slope measurement and USN technology was analyzed, and then the current status of damage caused by slope failures in Korea was reviewed. Next, a USN-based monitoring scenario for slope failures, incorporating both USN and slope monitoring technique, was developed. Finally, sensors were decided based on the developed scenario. It is expected that the results of this study will be utilized as fundamental data for the development of monitoring prototype systems for slope failures in the future. The development of the USN-based monitoring system for slope failures and its application in the field will also ultimately contribute to the prevention of slope failures and the minimization of related damage.

• Journal of Korean Society of Transportation
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• v.22 no.3 s.74
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• pp.109-125
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• 2004

In recent decades, microscopic simulation models have become powerful tools to analyze traffic flow on highways and to assist the investigation of level of service. The existing microscopic simulation models simulate an individual vehicle's speed based on a constant free-flow speed dominantly specified by users and driver's behavior models reflecting vehicle interactions, such as car following and lane changing. They set a single free-flow speed for a single vehicle on a given link and neglect to consider the effects of highway design elements to it in their internal simulation. Due to this, the existing models are limitted to provide with identical simulation results on both curved and tangent sections of highways. This paper presents a model developed to estimate the change of free-flow speeds based on highway design elements. Nine neural network models were trained based on the field data collected from seven different freeway curve sections and three different locations at each section to capture the percent changes of free-flow speeds: 100 m upstream of the point of curve (PC) and the middle of the curve. The model employing seven highway design elements as its input variables was selected as the best : radius of curve, length of curve, superelevation, the number of lanes, grade variations, and the approaching free-flow speed on 100 m upstream of PC. Tests showed that the free-flow speeds estimated by the proposed model were statistically identical to the ones from the field at 95% confidence level at each three different locations described above. The root mean square errors at the starting and the middle of curve section were 6.68 and 10.06, and the R-squares at these points were 0.77 and 0.65, respectively. It was concluded from the study that the proposed model would be one of the potential tools introducing the effects of highway design elements to free-flow speeds in simulation.

• 대한방사선치료학회:학술대회논문집
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• 2005.06a
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• pp.13-17
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• 2005

Introduction : For stereotactic radiosurgery (SRS) of a tumor in the region whose movement due to respiration is significant, like Lung lower lobe, the gated therapy, which delivers radiation dose to the selected respiratory phases when tumor motion is small, was peformed using the Respiratory gating system and its clinical effectiveness was evaluated. Methode and Materials : For two SRS patients with a tumor in Lung lower lobe, a marker block (infrared reflector) was attached on the abdomen. While patient' respiratory cycle was monitored with Real-time Position Management (RPM, Varian, USA), 4D CT was performed (10 phases per a cycle). Phases in which tumor motion did not change rapidly were decided as treatment phases. The treatment volume was contoured on the CT images for selected treatment phases using maximum intensity projection (MIP) method. In order to verify setup reproducibility and positional variation, 4D CT was repeated. Result : Gross tumor volume (GTV) showed maximum movement in superior-inferior direction. For patient $\#$1, motion of GTV was reduced to 2.6 mm in treatment phases ($30\%\~60\%$), while that was 9.4 mm in full phases ($0\%\~90\%$) and for patient $\#$2, it was reduced to 2.3 mm in treatment phases ($30\%\~70\%$), while it was 11.7 mm in full phases ($0\%\~90\%$). When comparing two sets of CT images, setup errors in all the directions were within 3 mm. Conclusion : Since tumor motion was reduced less than 5 mm, the Respiratory gating system for SRS of Lung lower lobe is useful.

• Journal of Korean Society of Forest Science
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• v.100 no.4
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• pp.535-539
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• 2011

This study was conducted to examine the bootstrap evaluation of the stem density and biomass expansion factor for Pinus rigida plantations in Korea. The stem density ($g/cm^3$) in less than 20 tree years were 0.460 while more than 21 tree years were 0.456 respectively. Biomass expansion factor of less than 20 years and more than 21 years were 2.013, 1.171, respectively. The results of 100 and 500 bootstrap iterations, stem density ($g/cm^3$) in less than 20 years were 0.456~0.462 while more than 21 years were 0.457~0.456 respectively. Biomass expansion factor of less than 20 years and more than 21 years were 1.990~2.039, 1.173~1.170, respectively. The mean differences between observed biomass factor and average parameter estimates showed within 5 percent differences. The split datasets of younger stands and old stands were compared to the results of bootstrap simulations. The stem density in less than 20 years of mean difference were 0.441~1.049% while more than 21years were 0.123~0.206% respectively. Biomass expansion factor in less than 20 years and more than 21 years were -1.102~1.340%, -0.024~0.215% respectively. Younger stand had relatively higher errors compared to the old stand. The results of stem density and biomass expansion factor using the bootstrap simulation method indicated approximately 1.1% and 1.4%, respectively.

• Journal of the Korea Society of Computer and Information
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• v.14 no.6
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• pp.41-49
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• 2009

In this paper, the multi-camera calibration algorithm for optical motion capture system is proposed. This algorithm performs 1st camera calibration using DLT(Direct linear transformation} method and 3-axis calibration frame with 7 optical markers. And 2nd calibration is performed by waving with a wand of known length(so called wand dance} throughout desired calibration volume. In the 1st camera calibration, it is obtained not only camera parameter but also radial lens distortion parameters. These parameters are used initial solution for optimization in the 2nd camera calibration. In the 2nd camera calibration, the optimization is performed. The objective function is to minimize the difference of distance between real markers and reconstructed markers. For verification of the proposed algorithm, re-projection errors are calculated and the distance among markers in the 3-axis frame and in the wand calculated. And then it compares the proposed algorithm with commercial motion capture system. In the 3D reconstruction error of 3-axis frame, average error presents 1.7042mm(commercial system) and 0.8765mm(proposed algorithm). Average error reduces to 51.4 percent in commercial system. In the distance between markers in the wand, the average error shows 1.8897mm in the commercial system and 2.0183mm in the proposed algorithm.

• Progress in Medical Physics
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• v.26 no.4
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• pp.193-200
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• 2015

The aim of this study is to present commissioning results of the ViewRay system. We verified safety functions of the ViewRay system. For imaging system, we acquired signal to noise ratio (SNR) and image uniformity. In addition, we checked spatial integrity of the image. Couch movement accuracy and coincidence of isocenters (radiation therapy system, imaging system and virtual isocneter) was verified. Accuracy of MLC positioing was checked. We performed reference dosimetry according to American Association of Physicists in Medicine (AAPM) Task Group 51 (TG-51) in water phantom for head 1 and 3. The deviations between measurements and calculation of percent depth dose (PDD) and output factor were evaluated. Finally, we performed gamma evaluations with a total of 8 IMRT plans as an end-to-end (E2E) test of the system. Every safety system of ViewRay operated properly. The values of SNR and Uniformity met the tolerance level. Every point within 10 cm and 17.5 cm radii about the isocenter showed deviations less than 1 mm and 2 mm, respectively. The average couch movement errors in transverse (x), longitudinal (y) and vertical (z) directions were 0.2 mm, 0.1 mm and 0.2 mm, respectively. The deviations between radiation isocenter and virtual isocenter in x, y and z directions were 0 mm, 0 mm and 0.3 mm, respectively. Those between virtual isocenter and imaging isocenter were 0.6 mm, 0.5 mm and 0.2 mm, respectively. The average MLC positioning errors were less than 0.6 mm. The deviations of output, PDDs between mesured vs. BJR supplement 25, PDDs between measured and calculated and output factors of each head were less than 0.5%, 1%, 1% and 2%, respectively. For E2E test, average gamma passing rate with 3%/3 mm criterion was $99.9%{\pm}0.1%$.

• Pediatric Infection and Vaccine
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• v.30 no.3
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• pp.129-138
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• 2023

Purpose: Cancer incidence is known to be higher in patients with inborn errors of immunity (IEI) compared to the general population in addition to traditionally well-known infection susceptibility. We aimed to investigate cancer occurrence in patients with IEI in a single center. Methods: Medical records of IEI patients treated at Samsung Medical Center, Seoul, Korea were retrospectively reviewed from November 1994 to September 2023. Patients with IEI and cancer were identified. Results: Among 194 patients with IEI, seven patients (3.6%) were diagnosed with cancer. Five cases were lymphomas, 4 of which were Epstein-Barr virus (EBV)-associated lymphomas. The remaining cases included gastric cancer and multiple myeloma. The median age at cancer diagnosis was 18 years (range, 1-75 years). Among patients with cancer, underlying IEIs included X-linked lymphoproliferative disease-1 (XLP-1, n=3), activated phosphoinositide 3-kinase delta syndrome (APDS, n=2), and cytotoxic T-lymphocyte antigen 4 (CTLA-4) haploinsufficiency (n=2). Seventy-five percent (3/4) of XLP-1 patients, 40.0% (2/5) of APDS patients, and 50.0% (2/4) of CTLA-4 haplo-insufficiency patients developed cancer. Patients with XLP-1 developed cancer at earlier age (median age 5 years) compared to those with APDS and CTLA-4 (P<0.001). One patient with APDS died during hematopoietic cell transplantation. Conclusions: Cancer occurred in 3.6% of IEI patients at a single center in Korea. In addition to infectious complications and inflammation, physicians caring for IEI patients should be aware of the potential risk of cancer, especially in association with EBV infection.