Junho Ko

Estimation of photoneutron yield in linear accelerator with different collimation systems by Geant4 and MCNPX simulation codes

At present, the bremsstrahlung photon beams produced by linear accelerators are the most commonly employed method of radiotherapy for tumor treatments. A photoneutron source based on three different energies (6, 10 and 15 MeV) of a linac electron beam was designed by means of Geant4 and Monte Carlo N-Particle eXtended (MCNPX) simulation codes. To obtain maximum neutron yield, two arrangements for the photo neutron convertor were studied: (a) without a collimator, and (b) placement of the convertor after the collimator. The maximum photon intensities in tungsten were 0.73, 1.24 and 2.07 photon/e at 6, 10 and 15 MeV, respectively. There was no considerable increase in the photon fluence spectra from 6 to 15 MeV at the optimum thickness between 0.8 mm and 2 mm of tungsten. The optimum dimensions of the collimator were determined to be a length of 140 mm with an aperture of 5 mm  ×  70 mm for iron in a slit shape. According to the neutron yield, the best thickness obtained for the studied materials was 30 mm. The number of neutrons generated in BeO achieved the maximum value at 6 MeV, unlike that in Be, where the highest number of neutrons was observed at 15 MeV. Statistical uncertainty in all simulations was less than 0.3% and 0.05% for MCNPX and the standard electromagnetic (EM) physics packages of Geant4, respectively. Differences among spectra in various regions are due to various cross-section and stopping power data and different simulations of the physics processes.

A review of network technologies in power monitoring systems in Korea

With recent introduction of IT in power systems, a number of studies are being conducted regarding the implementation of monitoring systems that utilize various technologies for monitoring transmission facilities. A power monitoring system monitors power system status based on realtime data acquired by various sensor elements installed on power transmission lines and facilities. A power monitoring system consists of multiple sensors on wired and wireless networks. This paper reviews various wired and wireless communication technologies used in sensor networks deployed in power monitoring systems in Korea.

Distributed Sensor Network-Based Virtual FDR System

We propose an application for power facility monitoring using distributed sensor networks. The proposed application is a virtual frequency disturbance recorder (FDR) system that estimates the frequency of a power grid using the data from a modeled grid and sends the information to the server for monitoring via wireless communication. To verify the validity of the proposed application, we conducted experiments using actual system data. The functionality of the proposed system was also verified by establishing a ZigBee-based wireless network for power monitoring and diagnosis of disturbances.

Development of epiduroscopy training simulator using haptic master device

Epiduroscopy is one of the widely implemented procedures in effective diagnosing and curing lumbago patients. Such endoscopic surgery requires much skill to control the surgical instruments well. Therefore, this paper proposes an epiduroscopy training simulator using a haptic master device. The proposed training simulator calculates forces using virtual fixture implemented in a catheter insertion path. The calculated forces are provided as haptic feedback to a user through the haptic master device, and the user is trained to catheter insertion path of expert through the haptic feedback.

Development of a Sensor Network-Based SMPS System: A Smart LED Monitoring Application Based on Wireless Sensor Network

As the specifications of personal, industrial, and medical devices become increasingly sophisticated, the demand for high power devices is also growing rapidly. Because high power supply devices are needed in order to operate high power devices with high specifications, stability and reliability are important factors to consider when it comes to high power supply devices. Therefore, there have been calls for further research on high quality power supply and monitoring system for high power supply. This paper proposes a sensor network-based smart SMPS (switch mode power supply) system. The proposed system makes power supply stable and efficient by providing output current control and sensor network-based monitoring. The functions of the proposed system were verified through both LED control simulation and monitoring simulation. The feasibility of the proposed system was also examined through various experiments and the results were discussed.

A study on surgical robot image stabilization

This study aims to investigate and analyze various image stabilization methods used in surgical robotics. An in-vitro phantom experiment was conducted using a master slave tele-manipulated system. An articulable image probe on a tool (eye-on-tool) was installed on an open-source surgical robot, RAVEN. The 2D non-stereo camera image was used to validate the image stabilization methods, which were evaluated individually for each processing step: preprocessing, motion estimation, and motion compensation. During the preprocessing procedure, the performance of three different filters was tested for effective noise suppression. Various algorithms were compared to estimate the global motion vectors (GMVs) in the motion estimation step. Finally, three filters were analyzed to estimate the compensation motion vector (CMV) during the motion estimation procedure.

A Study on Tracking and Augmentation in Mobile AR for e-Leisure

Recently, a mobile augmented reality (AR) system with AR technology that requires high performance has become popular due to the improved performance of smartphones. In particular, mobile AR that directly interacts with outdoor environments has been in development because of increasing interest in e-leisure due to improvements in living standards. Therefore, this paper aims to study tracking and augmentation in mobile AR for e-leisure. We analyzed the performance of human body tracking application implemented in a mobile system (smartphone) using three methods (marker-based, markerless, and sensor-based) for the feasibility examination of human body tracking in mobile AR. Furthermore, game information augmentation was examined through the implementation of mobile AR using two methods (marker- and sensor-based).

A Real-Time Video Abstraction Technique for AR Content Synthesis on Android Platform

In this paper, we offer an efficient real-time video abstraction technique that enables interaction with the real-world environment using a smart device for combining augmented reality (AR) and virtual content. The conventional video abstraction technique is inappropriate for the real-time processing of AR content. Therefore, real-time video abstraction through the GPU approach is necessary to minimize the CPU processing of AR content. The methods other than the abstraction technique using the Open GL-ES shader have constraints regarding hardware and the dependency of AR content data. Consequently, this paper proposes a real-time video abstraction technique using the Open GL-ES shader. The proposed real-time video abstraction technique is a method for minimizing the disharmony between virtual and real-world content occurring on AR performing in the limited computing resources of a smart device. To do this, we performed research on video abstraction and applied three filtering algorithms (Sobel operator, Striped pattern-based toon, Non-boundary-based color quantization). In addition, we considered the applicability of AR content through real-time video abstraction experiments using adjusted and monitoring parameters.

An evaluation on CT image acquisition method for medical VR applications

Recent medical virtual reality (VR) applications to minimize re-operations are being studied for improvements in surgical efficiency and reduction of operation error. The CT image acquisition method considering three-dimensional (3D) modeling for medical VR applications is important, because the realistic model is required for the actual human organ. However, the research for medical VR applications has focused on 3D modeling techniques and utilized 3D models. In addition, research on a CT image acquisition method considering 3D modeling has never been reported. The conventional CT image acquisition method involves scanning a limited area of the lesion for the diagnosis of doctors once or twice. However, the medical VR application is required to acquire the CT image considering patients’ various postures and a wider area than the lesion. A wider area than the lesion is required because of the necessary process of comparing bilateral sides for dyskinesia diagnosis of the shoulder, pelvis, and leg. Moreover, patients’ various postures are required due to the different effects on the musculoskeletal system. Therefore, in this paper, we perform a comparative experiment on the acquired CT images considering image area (unilateral/bilateral) and patients’ postures (neutral/abducted). CT images are acquired from 10 patients for the experiments, and the acquired CT images are evaluated based on the length per pixel and the morphological deviation. Finally, by comparing the experiment results, we evaluate the CT image acquisition method for medical VR applications.

Development of a Multiple SMPS System Controlling Variable Load Based on Wireless Network

This paper proposes a multiple switch mode power supply (SMPS) system based on the wireless network which controls variable load. The system enables power supply of up to 600W using 200W SMPS as a unit module and provides a controlling function of output power based on variable load and a monitoring function based on wireless network. The controlling function for output power measures the variation of output power and facilitates efficient power supply by controlling output power based on the measured variation value. The monitoring function guarantees a stable power supply by observing the multiple SMPS system in real time via wireless network. The performance of the proposed system was examined by various experiments. In addition, it was verified through standardized test of Korea Testing Certification. The results were given and discussed.