• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.103-112
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• 1991

In this study, a numerical model was established and applied to simulate the steady-state groundwater and heat flow in an isotropic, heterogeneous, three dimensional aquifer system with uniform thermal properties and no change of state. This model was developed as an aid in screening large groundwater-flow systems as prospects for underground waste storage. Driving forces on the system are external hydrologic conditions of recharge from precipitation and fixed hydraulic head boundaries. Heat flux includes geothermal heat-flow, conduction to the land surface, advection from recharge, and advection to or from fixed-head boundaries. The model uses an iterative procedure that alternately solves the groundwater-flow and heat-flow equations, updating advective flux after solution of the groundwater-flow equation, and updating hydraulic conductivity after solution of the heat-flow equation. Dierect solution is used for each equation. Travel time is determined by particle tracking through the modeled space. Velocities within blocks are linear interpolations of velocities at block faces. Applying this model to the groundwater-flow system located in Jigyung-ri. Songla-myun, Youngil-gun. Kyungsangbuk-do, the groundwater-flow system including distribution of head, temperature and travel time and flow line, is analyzed.

• Progress in Medical Physics
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• v.26 no.3
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• pp.143-152
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• 2015

In this study, we aim to design the architecture of the kV imaging system for tumor tracking in the dual-head gantry system and analyze its accuracy by simulations. We established mathematical formulas and algorithms to track the tumor position with the two-pair kV imaging systems when they are in the non-orthogonal positions. The algorithms have been designed in the homogeneous coordinate framework and the position of the source and the detector coordinates are used to estimate the tumor position. 4D XCAT (4D extended cardiac-torso) software was used in the simulation to identify the influence of the angle between the two-pair kV imaging systems and the resolution of the detectors to the accuracy in the position estimation. A metal marker fiducial has been inserted in a numerical human phantom of XCAT and the kV projections were acquired at various angles and resolutions using CT projection software of the XCAT. As a result, a positional accuracy of less than about 1mm was achieved when the resolution of the detector is higher than 1.5 mm/pixel and the angle between the kV imaging systems is approximately between $90^{\circ}$ and $50^{\circ}$. When the resolution is lower than 1.5 mm/pixel, the positional errors were higher than 1mm and the error fluctuation by the angles was greater. The resolution of the detector was critical in the positional accuracy for the tumor tracking and determines the range for the acceptable angle range between the kV imaging systems. Also, we found that the positional accuracy analysis method using XCAT developed in this study is highly useful and will be a invaluable tool for further refined design of the kV imaging systems for tumor tracking systems.

• International Journal of Highway Engineering
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• v.6 no.4 s.22
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• pp.45-53
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• 2004

This study dealt with correlation analysis between deformation strength and rut resistance of asphalt concretes based on binder grade in Superpave specification with changing submerging time. Currently, Mashall mix design is known to have little correlation with rutting related performance. Therefore, some agencies started to use the Superpave method for asphalt mix design. But this method has a weak point in that it can not distinct mechanical property of the asphalt mixtures designed. For solution of these problem, this study used deformation strength, $S_D$, of Kim test which is a new approach under development for finding property which represents rut resistance characteristics of asphalt mixtures under static loading. This study used two aggregates from two regions and five PG asphalt binders. Final rut depth (DR) and dynamic stability (DS) from wheel tracking (WT) test were obtained. and $S_D$ value of the same mixture specimen which was made by gyratory compactor was obtained using loading head [4(1.0)]. Three submerging times 30min, 40min, 50min were used as a test variable at $60^{\circ}C$. Correlation analysis of DR and DS with $S_D$ were performed based on PG grade. It was found out that the $S_D$ has a high correlation with DR and DS of superpave mixtures. The highest $R^2$ was found from the $S_D$ values of 30min. submerged specimen.

• Annals of Clinical Neurophysiology
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• v.11 no.2
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• pp.54-58
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• 2009

Background: Obstructive sleep apnea (OSA) is associated with several cardiovascular diseases. However, the mechanisms are not completely understood. The measure of common carotid artery intima-media thickness (IMT) has been extensively used as an early marker of atherosclerosis. The aim of this study was to test the hypothesis that early signs of atherosclerosis are present in patients with OSA and correlate with OSA severity Methods: Eleven male patients with OSA were studied by using full standard overnight polysomnography and high-definition echo-tracking device to measure intima-media thickness and carotid artery diameter. Eight healthy volunteers matched for age and sex were studied by portable respiratory monitoring device. All participants were free of hypertension, diabetes, and were not on any medications. Patients with OSA were naive to treatment. Results: All patients and normal controls were male. There was no significant difference of age between patients and controls ($48.4{\pm}8.85$ and $48.0{\pm}9.77$). Significant differences existed between control subjects and patients with mild to moderate and severe OSA (apnea-hypopnea index, $1.51{\pm}1.15$ and $38.51{\pm}19.13$ respectively) in intima-media thickness ($0.59{\pm}0.064$ and $0.93{\pm}0.16$; P=0.0023), and carotid diameter ($5.79{\pm}0.44$ and $6.47{\pm}0.51$; P=0.0227). Multivariate analyses showed that the apnea-hypopnea index correlated independently with intima-media thickness and carotid diameter (r=0.79, P=0.0008, and r=0.47, P=0.0482). Conclusions: Middle-aged patients with OSA who are free of overt cardiovascular diseases have early signs of atherosclerosis, which further supports the hypothesis that OSA plays an independent role in atherosclerosis progression.

• Journal of Biomedical Engineering Research
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• v.21 no.6
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• pp.615-621
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• 2000

A social phobia is an anxiety disorder characterized by extreme fear and phobic avoidance of social and performance situations. Medications or cognitive-behavior methods have been mainly used in treating it. These methods have some shortcomings such as being inefficient and difficult to apply to treatment. Lately the virtual rcality technology has been applied to dcal with the anxiety disorders in order to compcnsate for these defects. A virtual environment provides a patient with stimuli which cvokes a phobia. and the patient's exposure to the virtual phobic situation make him be able to overcome it. In this study, we suggested the public speaking simulator based on a personal computer for the treatment of social phobia. The public speaking simulator was composed of a position sensor. head mount display and audio system. And a virtual environment for the treatment was suggested to be a seminar room where 8 avatars are sitting. The virtual environment includes a tracking system the trace a participant's head-movement using a HMD with position sensor and 3D sound is added to the virtual environment so that he might fcel it realistic. We also made avatars' motion and facial expression change in reaction to a participant's speech. The goal of developing public speaking simulator is to apply to treat fear of public speaking efficiently and economically. In a future study. we should get more information about immergence and treatment efficiency by clinical test and apply it to this simulator.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.6
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• pp.68-76
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• 2011

We introduce a parallax barrier type autostereoscopic display in order to overcome the limited viewing angle of the conventional parallax barrier type displays. The proposed method adopts a special structure of double pairs of ITO that have a common TN-LC at the core of the conventional parallax barrier. Compared with the conventional parallax barrier type displays, the proposed display uses moving parallax barriers and eye tracking system to make stereoscopic view images adapted to the movement of viewer. We implemented a prototype of the proposed dual layer parallax barrier system, and verified that the proposed autostereoscopic display maintains seamless 3D views even when a viewer's head is moving.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.3
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• pp.61-69
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• 2010

This paper presents an efficient object selection algorithm by analyzing and detecting of human activity. Generally, when people point any something, they will put a face on the target direction. Therefore, the direction of the face and fingers and was ordered to be connected to a straight line. At first, in order to detect the moving objects from the input frames, we extract the interesting objects in real time using background subtraction. And the judgment of movement is determined by Principal Component Analysis and a designated time period. When user is motionless, we estimate the user's indication by estimation in relation to vector from the head to the hand. Through experiments using the multiple views, we confirm that the proposed algorithm can estimate the movement and indication of user more efficiently.

• Journal of the Korea Computer Graphics Society
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• v.17 no.4
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• pp.31-40
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• 2011

Projector-based visual systems are widely used for VR and experience display applications. But the illumination irregularity on the screen surface due to the screen material and its light reflection properties sometimes deteriorates the user experience. This phenomenon is particularly troublesome when the participants of the head tracking VR system such as CAVE or the motion generation experience system continually move around the system. One of reason to illumination irregularity is projector-screen specular reflection component to participant's eye's position and it's analysis needs high computation complexity. Similar to calculate specular lighting term using GPU's programmable shader, Our research adjusts every pixel's brightness in runtime with given 3D screen space model to reduce illumination irregularity. For doing that, Angle-based brightness compensate function are considered for specific screen installation and modified it for GPU-friendly compute and access. Two aspects are implemented, One is function access transformation from angular form to product and the other is piecewise linear interpolate approximation.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.30 no.1
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• pp.65-68
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• 2004

CyberKnife is a stereotactic radiosurgery system which could be used to treat many tumors and lesions. It provides the surgeon unparalleled flexibility in targeting using a compact light linear accelerator mounted on a robotic arm. Advanced image guidance technology tracks patient and target position during treatment, ensuring accuracy without the use of an invasive head frame. CyberKnife with Dynamic Tracking Software is cleared to provide radiosurgery for lesions anywhere in the body when radiation treatment is indicated. It has often been used to radiosurgically treat otherwise untreatable tumors and malformations. Moreover, this instrument treats tumors at body sites, most of which are unreachable by other stereotactic systems. Compared with conventional radiotherapy, it is fundamentally different that using non-invasive, frameless, no excessive radiation exposure to normal tissue. In oral malignant neoplasm, surgical excision and radiation therapy should be tried first, additionally chemotherapy could be considered. However, after failure of conventional therapies, patients had poor systemic condition and surgical limitation. So, CyberKnife could be a suitable therapy. A 49 years man was referred in recurred mandibular cancer treated by radiotherapy. The tumor was considered inoperable, because of extensive invasion and was not expected to good response to conventional therapies. We experienced a case of CyberKnife after 4 cycle chemotherapies, so we report it with review of literature.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.5
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• pp.923-932
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• 2017

In this paper, we propose a GRNN(: Generalized Regression Neural Network) algorithms for new eyes and face recognition identification system to solve the points that need corrective action in accordance with the existing problems of facial movements gaze upon it difficult to identify the user and. Using a Kalman filter structural information elements of a face feature to determine the authenticity of the face was estimated future location using the location information of the current head and the treatment time is relatively fast horizontal and vertical elements of the face using a histogram analysis the detected. And the light obtained by configuring the infrared illuminator pupil effects in real-time detection of the pupil, the pupil tracking was to extract the text print vector. The abstract is to be in fully-justified italicized text as it is here, below the author information.