• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.5
• /
• pp.368-375
• /
• 2018

In the present study, aerodynamic load analysis for a floating off-shore wind turbine was conducted to examine the effect of periodic platform motion in the direction of 6-DOF on rotor aerodynamic performance. Blade-element momentum method(BEM) was used for a numerical simulation, the unsteady airload effects due to the flow separation and the shed wake were considered by adopting a dynamic stall model based on the indicial response method. Rotor induced downwash was estimated using the momentum theory, coupled with empirical corrections for the turbulent wake states. The periodic platform motions including the translational motion in the heave, sway and surge directions and the rotational motion in the roll, pitch and yaw directions were considered, and each platform motion was applied as a sinusoidal function. For the numerical simulation, NREL 5MW reference wind turbine was used as the target wind turbine. The results showed that among the translation modes, the surge motion has the largest influence on changing the rotor airloads, while the effect of pitch motion is predominant for the rotations.

• Radiation Oncology Journal
• /
• v.12 no.1
• /
• pp.117-121
• /
• 1994

In spite of remarkable improvement of surgical skills and anesthesia, local failure still occurred in 36-45$ \% $ of locally advanced colorectal cancer after curative resection with or without pre-or post-operative irradiation. Intraoperative radiation therapy(IORT) is the ideal modality which resectable lesions are removed surgically 3nd the remaining cancer nests are sterilized by irradiation during a surgical procedure. Therefore, the excellent local control without the damage of the adjacent normal tissues can be achieved. In IORT, judicious set up of the treatment cone on the treatment surface of the patient is required for accurate and homogenous dose distribution within treatment field, especially on the slopping surface of sacrum and pelvic sidewall which are the common sites of the local recurrence in rectal cancer. For this purpose, adequate co-ordination of gantry rotation and table tilting are essential. Adjusting gantry rotation is not difficult but tilting of the table is impossible inconventional treatment couch. Department of Therapeutic Radiology in Yeungnam University Medical Center developed the IORT table for colorectal cancer which is easy to set up and detach on the Linac treatment couch within 5 minutes. The range of tilting with head-up and head-down is about 30 degree which is efficient and easy-to-use, not only for IORT but also for colorectal surgery. So far, authors performed IORT with newly developed treatment table in 2 patients with rectal cancer and we found that this newly developed table could contribute in improving the dose distribution of IORT and surgical procedure for colorectal cancer.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.25 no.5
• /
• pp.455-463
• /
• 2012

In this study, we calculate dynamic constrained force of tower top and blade root of a floating offshore wind turbine. The floating offshore wind turbine is multibody system which consists of a floating platform, a tower, a nacelle, and a hub and three blades. All of these parts are regarded as a rigid body with six degree-of-freedom(DOF). The platform and the tower are connected with fixed joint, and the tower, the nacelle, and the hub are successively connected with revolute joint. The hub and three blades are connected with fixed joint. The recursive formulation is adopted for constructing the equations of motion for the floating wind turbine. The non-linear hydrostatic force, the linear hydrodynamic force, the aerodynamic force, the mooring force, and gravitational forces are considered as external forces. The dynamic load at the tower top, rotor shaft, and blade root of the floating wind turbine are simulated in time domain by solving the equations of motion numerically. From the simulation results, the mutual effects of the dynamic response between the each part of the floating wind turbine are discussed and can be used as input data for the structural analysis of the floating offshore wind turbine.

• Journal of the Society of Naval Architects of Korea
• /
• v.39 no.3
• /
• pp.48-56
• /
• 2002

The flow characteristics around KRISO 3600TEU container ship model have been experimentally investigated in a circulating water channel. The instantaneous velocity vectors were measured using 2-frame PIV measurement system. The mean velocity fields and turbulent statistics including turbulent kinetic energy and vorticity were obtained by ensemble-averaging 400 instantaneous velocity fields. The free stream velocity was fixed at 0.6m/s and the corresponding Reynolds number was $9{\times}10^5$. The test sections were divided into two regions, three transverse sections of the wake region(Station -0.5767, -1, -3) and five longitudinal sections of the wake((Z/(B/2)=0, 0.1, 0.2, 0.4, 0.6). In the wake region, large-scale longitudinal vortices of nearly same strength are symmetric with respect to the wake centerline and a relatively weak secondary vortex is formed near the waterline. With going downstream, the strength of longitudinal vortex is decreased and the wake region expands.

• 전자공학회논문지 IE
• /
• v.43 no.4
• /
• pp.28-36
• /
• 2006

In this paper, an algorithm to classify the 4 motions of arm and a control system to position control the prosthesis are studied. To classify the 4 motions, we use flex sensors which is electrical resistance type sensor that can measure warp of muscle. The flex sensors are attached to the biceps brchii muscle and coracobrachialis muscle and the sensor signals are passed the sensing system. 4 motion of the forearm - flexion and extension, the pronation and supination are classified from this. Also position of forearm is measured from the classified signals. Finally, A two D.O.F prosthesis arm with RC servo-motor is designed to verify the validity of the algorithm. At this time, fuzzy controller is used to reduce the position error by rotary inertia and noise. From the experiment, the position error had occurred within about 5 degree.

• Journal of the Korean Chemical Society
• /
• v.33 no.2
• /
• pp.225-231
• /
• 1989

The heterogeneous rate constants for the electrochemical reduction by $trans-[Co(en)_2X_2](ClO_4)_n$(where X is cyanide, nitrite, ammonia, and isothiocyanate) at mercury and glassy carbon electrode were investigated by cyclic voltammetry, DC polarography, and by using rotating disk electrode. The good linear relationship was obtained between the activation energy of reduction and absorption wave number of complexes on glassy carbon electrode. At mercury electrode, $NO_2^-$ ligated complex showed the large deviation from the linear relationship. The difference in the value of rate constants for $NO_2^-$ ligated complex between mercury and glassy carbon electrode was about three order of magnitude which was much larger than the other complexes. It was suggested that $NO_^-$ ligated complex was reduced by inner-sphere mechanism on mercury electrode from the larger value of activation energy and entropy on mercury than carbon electrode.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.26 no.2
• /
• pp.13-24
• /
• 1989

The geometrical characteristics of sculls which are in use for propulsion of Korean traditional row boats were briefly surveyed. A typical dimension of the scull was selected and prototype for test was prepared. Angular displacements and the force components at handle and pivoting point were measured when the scull was operated in moored condition by skilled fisherman. Time histories and trajectories of motion were analyzed with the force generated at the scull blade. It was found out that the thrust of the scull was generated mainly by reaction force. The direction of improvement for better rowing motion could be also suggested. Continued study on this topic in a self-propulsion condition will provide us another interesting informations and prepare a possibility of application in evaluating rowing motion of oar.

• 한국HCI학회:학술대회논문집
• /
• 2008.02a
• /
• pp.534-539
• /
• 2008

This paper is about intelligent hexapod robot for the support walking of the aged person. The robot using various sensors and small camera has various abilities of forward backward walking, turing left or right, control the speed of walking, avoiding the obstacles and detecting risky situation of fire or gas. To let the aged feel soft and safe walking, we used special servo motor and developed hexapod walking mechanism and effective algorithm.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.11 no.4
• /
• pp.45-54
• /
• 1991

The closed forms of mass matrix with rotational inertia matrix are developed for free vibration analysis in space structures containing linearing tapered members with cross section of thin-walled tube. The exact displacement functions are used for formulating mass matrix. The very small slopes of the tapered member are used in usual practice, such that the series expansion forms of these are also developed to avoid numerical failure in vibration analysis. Significant improvements of accuracy and efficiency of free vibration analysis are achieved by using the mass matrices developed in this study. Frequencies of free vibration of tapered members are compared with solutions based upon stepped representation of beam element.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.6
• /
• pp.2015-2025
• /
• 1991

A long and light-weight forearm of the vertical 2 DOF robot manipulator with a heavy payload driven by parallel drive mechanism is modelled as a Euler-Bernoulli beam with a tip mass subjected to a high speed rotation. Governing equation is obtained by Hamilton's principle and represented as state variable form using the perturbed variables which describe the perturbed errors at the manipulator's final configuration. Digitial optimal control and observer theory are used to suppress the forearm vibration and control the positions of the joint angles with measured/estimated state feedback. Computer simulations and experimental results are obtained and compared each other.