• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.159-166
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• 2007

Mixing between two or more reagents is one of important processes in biochemical microfluidics. In efficient micromixer design, it is essential to analyze flow pattern and evaluate mixing efficiency with good precision. In this work, mixing efficiency for Y-channel micromixer is measured by fluorescence intensity using LIF(Laser Induced Fluorescence) Confocal Microscope. The Y-channel micromixers are fabricated with polydimethylsiloxane(PDMS) and those are bonded to glass plate through Plasma bonding. Nile Blue A is injected into the micromixer as a fluorescence dye for measuring of fluorescence intensity by He/Ne laser. For visualization of the flow pattern, dynamic image capturing is carried out using CAM scope. For the comparison with computer simulation, modified SIMPLE algorithm for incompressible flow equation is solved for the same geometry as in the experiment. Throughout the experiments and computer simulation, accurate mixing efficiency evaluation process for a PDMS Y-channel micromixer is established.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.834-839
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• 2004

In this paper, we have studied on the active vibration control of an automotive roof in passenger car's structure using piezoelectric material as the actuator and sensor attached on the surface of the automotive roof, As a control algorithm, negative velocity feedback control method is used in the study and the position of the sensor is almost attached on the nearest position of maximum normal stresses occurring while the roof is vibrating due to disturbance or exciting, Also, the actuator is attached on the other side mostly collocated to the sensor. The optimum positions have the maximum stresses of the roof which have been found in the result of the finite element analysis using Nastran software, As the fundamental experiments, a beam and plate have also been implemented to verify the performance of vibration suppression. Finally the experiment of the roof has been carried out and The roof experiment has just given a possibility to an active vibration control of the automotive structure still not applied for passenger cars.

• Journal of Ocean Engineering and Technology
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• v.30 no.5
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• pp.374-380
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• 2016

The large drift and angle of attack motion of an ROV (Remotely operated vehicle) cannot be modeled using the typical hydrodynamic coefficients of conventional straight running AUVs and specific slender bodies. In this paper, the ROV hull is divided into several simple-shaped components to model the hydrodynamic force and moment. The hydrodynamic force and moment acting on each component are modeled as the components of added mass force and drag using the known values for simple shapes such as a cylinder and flat plate. Since an ROV is operated under the water, the only environmental force considered is the current effect. The target ROV dealt with in this paper has six thrusters, and it is assumed that its maneuvering motion is determined using a thrust allocation algorithm. Tracking simulations are carried out on the ship’s surface near the stern, bow, and midship sections based on the modeling of the hydrodynamic force and current effect.

• Advances in Computational Design
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• v.5 no.1
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• pp.55-89
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• 2020

For the first time, an accurate analytical solution, based on coupled three-dimensional (3D) piezoelasticity equations, is presented for free vibration analysis of the angle-ply elastic and piezoelectric flat laminated panels under arbitrary boundary conditions. The present analytical solution is applicable to composite, sandwich and hybrid panels having arbitrary angle-ply lay-up, material properties, and boundary conditions. The modified Hamiltons principle approach has been applied to derive the weak form of governing equations where stresses, displacements, electric potential, and electric displacement field variables are considered as primary variables. Thereafter, multi-term multi-field extended Kantorovich approach (MMEKM) is employed to transform the governing equation into two sets of algebraic-ordinary differential equations (ODEs), one along in-plane (x) and other along the thickness (z) direction, respectively. These ODEs are solved in closed-form manner, which ensures the same order of accuracy for all the variables (stresses, displacements, and electric variables) by satisfying the boundary and continuity equations in exact manners. A robust algorithm is developed for extracting the natural frequencies and mode shapes. The numerical results are reported for various configurations such as elastic panels, sandwich panels and piezoelectric panels under different sets of boundary conditions. The effect of ply-angle and thickness to span ratio (s) on the dynamic behavior of the panels are also investigated. The presented 3D analytical solution will be helpful in the assessment of various 1D theories and numerical methods.

• Smart Structures and Systems
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• v.24 no.2
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• pp.173-182
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• 2019

Due to the degradation of beamforming properties at angles close to $0^{\circ}$ to $180^{\circ}$, linear array does not have a complete $180^{\circ}$ inspection range but a smaller one. This paper develops a improved sensor array with two additional sensors above and below the linear sensor array, and presents time difference and two dimensional multiple signal classification (2D-MUSIC) based impact localization for omni-directional localization on composite structures. Firstly, the arrival times of impact signal observed by two additional sensors are determined using the wavelet transform and compared, and the direction range of impact source can be decided in general, $0^{\circ}$ to $180^{\circ}$ or $180^{\circ}$ to $360^{\circ}$. And then, 2D-MUSIC based spatial spectrum formula using uniform linear array is applied for locate accurate position of impact source. When the arrival time of impact signal observed by two additional sensors is equal, the direction of impact source can be located at $0^{\circ}$ or $180^{\circ}$ by comparing the first and last sensor of linear array. And then the distance is estimated by time difference algorithm. To verify the proposed approach, it is applied to a quasi-isotropic epoxy laminate plate and a stiffened composite panel. The results are in good agreement with the actual impact occurring position.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.413-422
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• 2022

Blast Hardened Bulkheads (BHB) are used to suppress damage propagation by internal explosions to reduce ships'vulnerability. However, for this reason, the weight of the ship inevitably increased, and other functions such as the ships'mobility were bound to deteriorate. Therefore, it is essential in the initial design of the ship to optimize the dimensions of the bulkhead to minimize the weight while decreasing the vulnerability of the ship. Research on design optimization of BHB has been conducted, but it has not considered explosive load in various hit scenarios. This study proposed an optimal design method for the curtain plate type blast hardened bulkhead, which is currently frequently applied by the Korean Navy in consideration of various hit scenarios. Using genetic algorithms, multiobjective design optimizations that minimize weight increase as well as minimize damage to ships were obtained. By optimizing the dimensions of the BHB considering various hit scenarios, the ship's vulnerability was improved while maintaining its mobility due to weight reduction.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.456-458
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• 2022

Due to the environmental regulations of the International Maritime Organization, shipyards are conducting various researches to improve the efficiency of ships, and efforts are being made to reduce the weight of ships. Recently, composite materials including CNT materials have the advantage of being able to reduce weight by 40% or more compared to general steel plate materials, and have the advantage of being able to be used as a substitute for ship clamps or door skins. Therefore, in this study, to predict the life of composite materials including CNT materials, the results were compared through the accelerated deterioration test method and the life prediction using machine learning techniques. The accelerated degradation test used the Arrhenius model equation, and the machine learning method predicted the life using a regression analysis algorithm.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.3
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• pp.433-440
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• 2023

When the reflector is hit by a vehicle or returned by a storm, an event is generated by the impact sensor and a trigger is operated. The trigger processing algorithm of this paper compares the X, Y, and Z values of the gyro sensor with the registered values and proposes to drive them to the original values by the operation of the 3-axis driving motor. And by recognizing the vehicle license plate, if the vehicle is stolen or a social problem, information is provided to the police operation network. When the reflector is stolen or moved, it has a registered GPS value, so it operates the theft monitoring function to process it.

• Korean Journal of Construction Engineering and Management
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• v.13 no.1
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• pp.118-128
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• 2012

As the bearing wall structure, which has been widely applied to domestic apartment buildings since the 1980s, cause many problems during remodeling of buildings, the government encourages constructors to adopt flat plate or rahmen structure through legal incentives. In line with such a trend, the green frame, an eco-friendly rahmen structure that has removed the shortcomings of previous structures, was developed to enhance structural safety, constructability, and eco-friendliness. The construction of green frame can reduce the labor cost and facilitate the composition of iron bars to reduce rebar loss through calculating the quality and establishing the bar bending schedule automatically on the precast concrete member data collected over the design phase. Therefore, the purpose of this study is to develop the algorithm to automate the calculation of iron bar volume for the green frame designed on composite precast concrete members. Automated algorithm to calculate concrete structural design information and design information. Practices through the application site should prove efficacy. The database established by the developed algorithm will automate the establishment of iron bar processing map and bar cutting list and the calculation of optimal composition and order volume to minimize the rebar loss. This will also reduce the expenses on management staff and overall construction cost through the minimization of rebar loss.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.4
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• pp.213-220
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• 2023

This paper presents a model simulating the folding process and collision dynamics of "ddakji", a traditional Korean game played using paper tiles (which are also referred to as ddakji). The model uses two A4 sheets as the base materials for ddakji. The folding process involves a series of boundary conditions that transform the wing part of the paper structure into a twisted configuration. A rigid plate boundary condition is also adopted for squeezing, establishing the shape and stress state of the game-ready ddakji through dynamic relaxation analysis. The gaming process analysis involves a forced displacement of the striking ddakji to a predetermined collision position. Collision analysis then follows at a given speed, with the objective of overturning the struck ddakji--a winning condition. A genetic algorithm-based optimization analysis identifies the optimal collision conditions that result in the overturning of the struck ddakji. For efficiency, the collision analysis is divided into two stages, with the second stage carried out only if the first stage predicts a possible overturn. The fitness function for the genetic algorithm during the first stage is the direction cosine of the struck ddakji, whereas in the second stage, it is the inverse of the speed, thus targeting the lowest overall collision speed. Consequently, this analysis provides optimal collision conditions for various compression thicknesses.