• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.3
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• pp.232-239
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• 2009

The prediction of the separation trajectories of external stores carried by military aircraft is an important task in the area of aircraft design having the objective to define the operational, release envelopes. This paper presents the results obtained for safe store separation from a fighter aircraft by experimental methods in the subsonic wind tunnel. The problems associated with separation of external stores can be studied by the use of several wind-tunnel test techniques. Attention is given the two most useful techniques: 1) dynamically scaled drop-model testing, 2) grid testing. A description of each method is given and data obtained are shown to validate the similarity within acceptable limits.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.1-11
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• 2018

A system design and integrated design process for a space launch vehicle were established based on system engineering. With the mission design results for a given payload weight and trajectory, it is possible to perform optimal design by integrating each unit such as propulsion, weight estimation, and aerodynamic force after analysis, during in the system design process. The program is finally configured to verify that the designed vehicle can perform its mission through 3-DOF trajectory optimization simulation. Genetic algorithms are used as the optimization method, and the optimal design results of the variables and parameters to be considered during design are presented.

• Journal of agriculture & life science
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• v.52 no.6
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• pp.127-138
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• 2018

In this study, the operational characteristics of a domestic vegetable transplanter were investigated. The main functional components and power path of the tranplanter were analyzed. The link structure of transplanting device waskinematically analyzed, and 3D modeling and dynamic simulation were performed. Based on this analysis, the trajectory of the bottom end of the transplanting hopper was analyzed. Also, the plant spacing according to the engine speed and the shifting stage of transplanting transmission was analyzed and verified by field test. As main results of this study, the transplanting device is one degree of freedom(DOF) 4-bar link type mechanism which comprises 10 links and 13 rotating joints. The transplanting hopper plants seedlings in a vertical direction while maintaining a constant posture by the links of transplanting device. The power is transmitted to both the driving part and transplanting part from the engine, and the maximum and minimum plant spacing of the transplanting device were 428.97 mm and 261.20 mm.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.1
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• pp.49-61
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• 2007

Otter boards in the trawl are the one of essential equipments for the net mouth to be spread to the horizontal direction. Its performance should be considered in the light of the spreading force to the drag and the stability of towing in the water. Up to the present, studies of the otter boards have focused mainly on the drag and lift force, but not on the stability of otter boards movement in 3 dimensional space. In this study, the otter board is regarded as a rigid body, which has six degrees of freedom motion in three dimensional coordinate system. The forces acting on the otter boards are the underwater weight, the resistance of drag and spread forces and the tension on the warps and otter pendants. The equations of forces were derived and substituted into the governing equations of 6 degrees of freedom motion, then the second order of differential equations to the otter boards were established. For the stable numerical integration of this system, Backward Euler one of implicit methods was used. From the results of the numerical calculation, graphic simulation was carried out. The simulations were conducted for 3 types of otter boards having same area with different aspect ratio(${\lambda}=0.5,\;1.0,\;1.5$). The tested gear was mid-water trawl and the towing speed was 4k't. The length of warp was 350m and all conditions were same to each otter board. The results of this study are like this; First, the otter boards of ${\lambda}=1.0$ showed the longest spread distance, and the ${\lambda}=0.5$ showed the shorted spread distance. Second, the otter boards of ${\lambda}=1.0$ and 1.5 showed the upright at the towing speed of 4k't, but the one of ${\lambda}=0.5$ heeled outside. Third, the yawing angles of three otter boards were similar after 100 seconds with the small oscillation. Fourth, it was revealed that the net height and width are affected by the characteristics of otter boards such as the lift coefficient.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.772-778
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• 2012

In this paper, the states and the parameters in the dynamic system are simultaneously estimated by applying the UKF(Unscented Kalman Filter), which is widely used for estimating the state of non-linear systems. Estimating the parameter is very important in various fields, such as system control, modeling, analysis of performance, and prediction. Most of the dynamic systems which are dealt with in engineering have non-linearity as well as some noise. Therefore, the parameter estimation is difficult. This paper estimates the states and the parameters applying to the UKF, which is a non-linear filter and has strong noise. The augmented equation is used by including the addition of the parameter factors to the original state equation of the system. Moreover, it is simulated by applying to a 2-DOF(Degree of Freedom) dynamic system composed of the pendulum and the slide. The measurement noise of the dynamic equation is assumed to be a Gaussian distribution. As the simulation results show, the proposed parameter estimation performs better than the LSM(Least Square Method). Furthermore, the estimation errors and convergence time are within three percent and 0.1 second, respectively. Consequentially, the UKF is able to estimate the system states and the parameters for the system, despite having measurement data with noise.

• Journal of agriculture & life science
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• v.53 no.4
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• pp.113-124
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• 2019

In this study, the operational characteristics of a cam-type vegetable transplanter which usually used in domestic was analyzed and operating mechanism of a transplanting device was analyzed. The main components and power path of the transplanter were analyzed. The maximum and minimum control cycles according to the moving speed and the plant spacing were analyzed. 3D modeling and simulation were performed to derive the trajectory of the bottom end of the transplanting hopper and the plant spacing at the each operating condition. The simulation results were verified by the field tests. As main findings of this study, the transplanting device has one degree of freedom (DOF) which consist of 13 links, 17 rotating joints and 1 half joint, and each part has composite structure with cam and links. By continuous and repetitive motion of the structures of transplanting device, the transplanting hopper plants the seedling in the ground with a vertical direction, and the seedling was planted stably. The power is transmitted to the driving part and transplanting device from the engine, and the maximum and minimum plant spacing of the transplanting device were about 900 mm and 350 mm, respectively.

• Journal of Biomedical Engineering Research
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• v.23 no.5
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• pp.351-364
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• 2002

Conventional 3D ultrasound imaging using mechanical ID arrays suffers from poor elevation resolution due to the limited depth-of-focus (DOF). On the other hand, 3D imaging systems using 2D phased arrays have a large number of active channels and hence require a very expensive and bulky beamforming hardware. To overcome these limitations, a new real-time volumetric imaging method using curved 2-D arrays is presented, in which a small subaperture, consisting of 256 elements, moves across the array surface to scan a volume of interest. For this purpose, a 2-D curved array is designed which consists of 90$\times$46 elements with 1.5λ inter-element spacing and has the same view angles along both the lateral and elevation directions as those of a commercial mechanical 1-D array. In the proposed method, transmit and receive subapertures are constructed by cutting the four corners of a rectangular aperture to obtain a required image qualify with a small number of active channels. In addition the receive subaperture size is increased by using a sparse array scheme that uses every other elements in both directions. To suppress the grating lobes elevated due to the increase in clement spacing, fold-over array scheme is adopted in transmit, which doubles the effective size of a transmit aperture in each direction. Computer simulation results show that the proposed method can provide almost the same and greatly improved resolutions in the lateral and elevation directions, respectively compared with the conventional 3D imaging with a mechanical 1-D array.

• Plant Journal
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• v.9 no.3
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• pp.38-42
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• 2013

Submarine gas fields have focused because of the increasing fuel cost, the environmental regulations, and the safety & NIMBY problems. LNG-FPSO which is available for acid gas removal, recovery of the condensate & LPG and Liquefaction in topside process is one of high technology offshore structures. On the other hands, it is necessary to verify the pre-treatment efficiency by the ship motion and to apply to the design for LNG-FPSO. This study is to develop the pre-treatment technology for LNG-FPSO as taking account to the process efficiency by ship motion effects and the area optimization. Based on the simulation results, it founds that hybrid process shows the low circulate rate, the low heat duty and the small size of column dimensions compared to typical amine process. It will be verified the process efficiency in the various conditions by sea states as performing the 6-DOF motion test and CFD simulation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.5
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• pp.455-463
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• 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 Navigation and Port Research
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• v.34 no.3
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• pp.195-203
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• 2010

This paper concerns about total dynamic analysis of integrated mining system. This system consists of vertical steel pipe, intermediate buffer station, flexible pipe and self-propelled miner. The self-propelled miner and buffer are assumed as rigid-body of 6-dof. Discrete models of vertical steel pipe and flexible pipe are adopted, which are obtained by means of lumped-parameter method. The motion of mining vessel is not considered. Instead, the motion of mining vessel is taken into account in form of various boundary conditions (e.g. forced excitation in slow motion and/or fast oscillation and so on). A terramechanics model of extremely cohesive soft soil is applied to the self-propelled miner. Hinged and ball constraints are used to define the connections between sub-systems (vertical steel pipe, buffer, flexible pipe, self-propelled miner). Equations of motion of the coupled model are derived with respect to the each local coordinates system. Four Euler parameters are used to express the orientations of the sub-systems. To solve the equations of motion of the total dynamic model, an incremental-iterative formulation is employed. Newmark-${\beta}$ method is used for time-domain integration. The total dynamic responses of integrated mining system are investigated.