• Progress in Medical Physics
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• v.24 no.4
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• pp.243-252
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• 2013

The aim of this study was to clarify the impacts of acquisition parameters on artifacts in four-dimensional computed tomography (4D CT) images, such as the partial volume effect (PVE), partial projection effect (PPE), and mis-matching of initial motion phases between adjacent beds (MMimph) in cine mode scanning. A thoracic phantom and two cylindrical phantoms (2 cm diameter and heights of 0.5 cm for No.1 and 10 cm for No.2) were scanned using 4D CT. For the thoracic phantom, acquisition was started automatically in the first scan with 5 sec and 8 sec of gantry rotation, thereby allowing a different phase at the initial projection of each bed. In the second scan, the initial projection at each bed was manually synchronized with the inhalation phase to minimize the MMimph. The third scan was intentionally un-synchronized with the inhalation phase. In the cylindrical phantom scan, one bed (2 cm) and three beds (6 cm) were used for 2 and 6 sec motion periods. Measured target volume to true volume ratios (MsTrueV) were computed. The relationships among MMimph, MsTrueV, and velocity were investigated. In the thoracic phantom, shorter gantry rotation provided more precise volume and was highly correlated with velocity when MMimph was minimal. MMimph reduced the correlation. For moving cylinder No. 1, MsTrueV was correlated with velocity, but the larger MMimph for 2 sec of motion removed the correlation. The volume of No. 2 was similar to the static volume due to the small PVE, PPE, and MMimph. Smaller target velocity and faster gantry rotation resulted in a more accurate volume description. The MMimph was the main parameter weakening the correlation between MsTrueV and velocity. Without reducing the MMimph, controlling target velocity and gantry rotation will not guarantee accurate image presentation given current 4D CT technology.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1828-1831
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• 1997

this paper, to represent the robot motion approximately in space, delas with algorithm for position recognition of space robot, target and obstacle with vision system in 2-D. And also there are algorithms for precise distance-measuring and calibration usign laser displacement system, and for trajectory selection for optimizing moving to object, and for robot locomtion with air-thrust valve. And the software synthesizing of these algorithms hleps operator to realize the situation certainly and perform the job without any difficulty.

• The Journal of the Convergence on Culture Technology
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• v.6 no.3
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• pp.353-359
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• 2020

In this study, the controller structure and control algorithm of medical robot bed developed for pressure ulcer prevention and healing are described. The existing pressure ulcer prevention mattress is operated manually and the remaining maximum body pressure exceeds the pressure of ulcer generation, so there is always room for pressure ulcers. However, the system developed in this study does not generate the pressure ulcers because the body pressure drops to zero when the keyboard of the bed descends using the active electric driving keyboard. In addition, even if the bed is raised and the pressure above the critical body ulcer pressure is abnormal, the device and the control algorithm are designed so that the lasting time is within the pressure ulcer generation critical time and the pressure ulcer itself is not generated. The bed key board motor is a motor designed with the BLDC servos suitable for medical use and these can communicate each other easily through CAN(Car Area Network). The system is new medical robot bed that is effective in preventing pressure ulcers and will be distributed to many patients suffering from pressure ulcers.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.446-449
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• 2002

Recently, advanced manufacturing system with high speed and intelligent have been developed for the betterment of machining ability. In this case, reliability prediction work with motion characteristic evaluation of sliding cover has also important roll from design procedure to manufacturing and assembly process. Accordingly in this study, H/W test -bed system for reliability evaluation of sliding cover has been developed to obtain proper reference data for design of new model, and also prevention trouble, quality and life cycle improvement extremely for advanced mother machinary.

• Water Engineering Research
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• v.3 no.2
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• pp.75-84
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• 2002

An Euler-Lagrange two-phase flow model is presented fur simulation sheet-flow transport under wave and current. The flow is computed by solving the Reynolds Averaged Navier-Stokes equation in conjunction with the k-$\varepsilon$ turbulence model for turbulence closure. The sediment transport is introduced as a motion of granular media under the action of unsteady flow from the Lagragian point of view. In other word, motion of every single particle is numerically traced with Movable Bed Simulator (MBS) code based on the Distinct Element Method (DEM), in which the frequent interparticle collision of the moving particles during the sheet-flow transport is sophisticatedly taken into account. The particle diameter effect on time-dependent developing process of sheet-flow transport is investigated, by using three different diameter sizes of sediment. The influence of an imposed current on oscillatory sheet-flow transport is also investigated. It is concluded that the sediment transport rate increases due to the relaxation process related to the time-lag between flow velocity and sediment motion.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.1
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• pp.86-94
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• 1984

In order to improve the rotational performances of NC lathe spindle system in high speed range, a new type(Floating-type driven by V-belt)spindle system was optimally designed and experimented. Through the results of the experiments, the rotational performances of the new type spindle system was discussed and compared with the three equivalent conventional lathe spindle systems. The spindle rotational accuracy( radial error motion of spindle axis), the accelation and the temperature rise of the front spindle bearings for the non-cutting operation were considered as the spindle rotational performances. The radial error motion of the spindle axis was measured by applying the modified L.R.L. method. Compared with the equivalent conventional spindle systems, the following results were obtained. (1) The new type spindle system reduces the radial error motion of the spindle axis in high speed range(1800rpm-2000rpm). (2) The new type spindle system reduces the acceleration and the temperature rise of the spindle bearings considerably with increasing the spindle speed. It is also confirmed that, by this new type spindle system, the max. allowable speed can be increased with satisfying the spindle rotational performances.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.267-277
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• 1993

A finite element method(FEM) is presented and applied to the two-dimensional bottom turbulent boundary layer. The time-dependent incompressible motion of a viscous fluid is formulated by using the well-known Navier-Stokes equations and vorticity equation in terms of the velocity and pressure fields. The general numerical formulation is based on Galerkin method and solved by introducing the mixing length theory of Prandtl for eddy kinematic viscosity of a turbulent flow field. Numerical computations of the transport of sediment on an arbitrary sea-bed due to wave motion in the turbulent boundary layer are carried out. The results obtained by the FEM made clear the difference in characteristic features between the boundary layer due to oscillatory flow and the boundary layer due to wave motion.

• Journal of computational fluids engineering
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• v.20 no.1
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• pp.1-9
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• 2015

A developed code is applied to simulate relative motion of floating bodies in a side-by-side arrangement, including effects of a fender and a hawser. The developed code is based on the flux-difference splitting scheme for immiscible incompressible fluids and the hybrid Cartesian/immersed boundary method. To validate the developed code for free surface flows around deforming boundaries, the water wave generation is simulated, which is caused by bed movement. The computed wave profile and time histories of wave elevation are compared with other experimental and computational results. The effects of a fender and a hawser are modeled by asymmetric force acting on the floating bodies according to a relative displacement with the bounds, in which the fender and the hawser exert no force on the bodies. It has been observed that the floating body can be accelerated by a gap flow due to a phase difference caused by the free surface. Grid independency is established for the computed time history of the body velocity, based on three different size grids.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.57-62
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• 2003

This paper describes the design and simulation of a multivariable optimal control system for the combined speed, heading and depth control of a Semi-Autonomous Underwater Vehicle (SAUV) developed in Korea Ocean Research and Development Institute (KRODI). The SAUV is a test-bed for the evaluation of the navigation and manipulator technologies developed for a mine disposal vehicle (MDV) in military use and for a light working underwater vehicle in scientific use. The vehicle was designed to control its cruising speed, heading and depth with 4 horizontal thrusters installed at the rear of the hull. Therefore, the decoupled control methods are limited to apply to the SAUV because the thrust forces are highly coupled with the surging, yawing, and pitching motion of the vehicle. The multivariable Linear Quadratic (LQ) control method is chosen to control steering and diving in variable speed motion automatically. A series of simulation is carried out with fully nonlinear six degree of freedom dynamic model to validate the controller.

• Radiation Oncology Journal
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• v.37 no.1
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• pp.43-50
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• 2019

Purpose: The aim of this retrospective study was to investigate the use of a radiopaque tissue fiducial marker (TFM) in the treatment of prostate cancer patients who undergo post-prostatectomy radiotherapy (PPRT). TFM safety, its role and benefit in quantifying the set-up uncertainties in patients undergoing PPRT image-guided radiotherapy were assessed. Materials and Methods: A total of 45 consecutive PPRT patients underwent transperineal implantation of TFM at the level of vesicourethral anastomosis in the retrovesical tissue prior to intensity-modulated radiotherapy. Prostate bed motion was calculated by measuring the position of the TFM relative to the pelvic bony anatomy on daily cone-beam computed tomography. The stability and visibility of the TFM were assessed in the initial 10 patients. Results: No postoperative complications were recorded. A total of 3,500 images were analysed. The calculated prostate bed motion for bony landmark matching relative to TFM were 2.25 mm in the left-right, 5.89 mm in the superior-inferior, and 6.59 mm in the anterior-posterior directions. A significant 36% reduction in the mean volume of rectum receiving 70 Gy (rV₇₀) was achieved for a uniform planning target volume (PTV) margin of 7 mm compared with the Australian and New Zealand Faculty of Radiation Oncology Genito-Urinary Group recommended PTV margin of 10 mm. Conclusion: The use of TFM was safe and can potentially eliminate set-up errors associated with bony landmark matching, thereby allowing for tighter PTV margins and a consequent favourable reduction in dose delivered to the bladder and rectum, with potential improvements in toxicities.