Time filter

Source Type

Pohang, South Korea

Hong S.-M.,Kyungpook National University | Jung B.-H.,Yongin Songdam College | Ruan D.,University of California at Los Angeles
Physics in Medicine and Biology | Year: 2011

Motion-adaptive radiotherapy aims to deliver ablative radiation dose to the tumor target with minimal normal tissue exposure, by accounting for real-time target movement. In practice, prediction is usually necessary to compensate for system latency induced by measurement, communication and control. This work focuses on predicting respiratory motion, which is most dominant for thoracic and abdominal tumors. We develop and investigate the use of a local dynamic model in an augmented space, motivated by the observation that respiratory movement exhibits a locally circular pattern in a plane augmented with a delayed axis. By including the angular velocity as part of the system state, the proposed dynamic model effectively captures the natural evolution of respiratory motion. The first-order extended Kalman filter is used to propagate and update the state estimate. The target location is predicted by evaluating the local dynamic model equations at the required prediction length. This method is complementary to existing work in that (1) the local circular motion model characterizes 'turning', overcoming the limitation of linear motion models; (2) it uses a natural state representation including the local angular velocity and updates the state estimate systematically, offering explicit physical interpretations; (3) it relies on a parametric model and is much less data-satiate than the typical adaptive semiparametric or nonparametric method. We tested the performance of the proposed method with ten RPM traces, using the normalized root mean squared difference between the predicted value and the retrospective observation as the error metric. Its performance was compared with predictors based on the linear model, the interacting multiple linear models and the kernel density estimator for various combinations of prediction lengths and observation rates. The local dynamic model based approach provides the best performance for short to medium prediction lengths under relatively low observation rate. Sensitivity analysis indicates its robustness toward the choice of parameters. Its simplicity, robustness and low computation cost makes the proposed local dynamic model an attractive tool for real-time prediction with system latencies below 0.4 s. © 2011 Institute of Physics and Engineering in Medicine. Source

Lim S.,Myongji University | Kim K.,Yongin Songdam College | Shim J.,TUR Co. | Cha K.,Agency for Defense Development | Cho C.,Agency for Defense Development
International Journal of Precision Engineering and Manufacturing | Year: 2012

The rotating chamber is expected to significantly benefit mid-caliber automatic guns with the high firepower-to-armament space ratio. However, the parallel index, which is a core component of the chamber system, tends to be flexible in rapid operation. This may cause the chamber prone to torsional vibration so that serious misalignment problems arise during ammunition loading as well as firing processes. In this context, an active control algorithm is proposed incorporating a reaction wheel as the actuator, suppressing only the residual vibration and optionally self-adapting the shooting rate to the actuator condition. For assessment of the idea, the entire system is mathematically modeled and then simulated in several cases. The comparative simulation results support that by the proposed method the chamber vibration can be reduced even to 6.5 percent at the expense of relatively small amount of actuator energy. © KSPE and Springer 2012. Source

Lim S.,Myongji University | Kim K.,Yongin Songdam College | Kil S.,TUR Co. | Shim J.,TUR Co. | Cha K.,Agency for Defense Development
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2011

It is reported that an intermittently rotating chamber system will improve the ratio of firepower to armament space in the case of mid-calibre automatic guns. However, the parallel index, which is a main component of the system, tends to be torsionally flexible due to the low lateral stiffness of cam followers on the index turret. This may cause the shaft system connecting the turret with the chamber prone to considerable residual torsional vibration so that serious misalignment problems occur during ammunition loading and firing processes. Herein, an electrorhelogical (ER) fluid actuator that can suppress such vibrations and the associated semiactive control algorithm are proposed. By mathematical modeling and computer simulations, the performance of the entire system is proved satisfactory. © 2011 The Korean Society of Mechanical Engineers. Source

Lee H.-J.,Yongin Songdam College | Kang K.-J.,Pai Chai University | Park S.-H.,Kyung Hee University | Ju S.-J.,University of Seoul | And 2 more authors.
Healthcare Informatics Research | Year: 2012

Objectives: Body weight, body mass index (BMI), body fat, and blood pressure are important indicators of a person's health. In this experimental study, we evaluated the effectiveness of an integrated personalized health care system, Health Improvement and Management System (HIMS)-everyday, which instantly provides subjects with biofeedback on their measured body weight, BMI, body fat and blood pressure using a database that stores subjects-customized information. Methods: The subjects of this study used the system once or twice a week for 8 weeks. We analyzed the changes in their body weight, BMI, body fat, and blood pressure according to their respective usage of the system, and analyzed the changes in their perceived health status and health promoting behavior accordingly. Results: Subjects' body weight, BMI, and blood pressure decreased significantly with respect to their individual usage of the system. Subjects who used the system more frequently showed significant improvement in their body weight, BMI, and body fat. However, subjects' perceived health status and health promoting behavior did not improve significantly. Conclusions: The study showed that the biofeedback-based personalized health care system was effective in controlling middle-aged and elderly women' body weight, BMI, body fat, and blood pressure. © 2012 The Korean Society of Medical Informatics. Source

Min C.,Yongin Songdam College | Jo J.,Yongin Songdam College | Shin J.,Yongin Songdam College | Lee S.,Korea Food Research Institute
Palpu Chongi Gisul/Journal of Korea Technical Association of the Pulp and Paper Industry | Year: 2011

Antimicrobial activities of the Acidic Liquid originated from Carbonized Rice Hull(ALCRH) and the paper treated with ALCRH were investigated to apply ALCRH to functional paper products as a natural antimicrobial agent. ALCRH showed antimicrobial activity for bacteria and yeast, with higher performance for bacteria than for yeast. Antimicrobial activity was not developed on paper coated with ALCRH by bar coater probably due to the evaporation of antimicrobial compounds of ALCRH from the paper surface with time. Saturation of paper with ALCRH was essential to develop antimicrobial activity on the paper. Dipping paper in ALCRH solution was recommended as one of the effective ways to make antimicrobial paper. Source

Discover hidden collaborations