• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1107-1114
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• 2017

In this paper, a miniaturized distribution line was experimentally made. The smart grid distribution system was modeled by analyzing the distribution system, and a miniaturized micro three phase distribution system recloser was designed. The micro recloser was designed as a sensor part, a main part and a relay part, and the main part was designed to cut off the fault current by determining the fault from the input current based on the DSP. Finally, based on the results of the modeling, the micro three phase power distribution line and the micro three phase recloser were experimentally fabricated, and the basic making technology of the miniaturized micro smart grid was obtained through the making process.

• Journal of the Korean Society of Radiology
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• v.16 no.7
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• pp.863-870
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• 2022

DLG (Dosimetric Leaf Gap) and transmission factor are important parameters of MLC modeling in treatment planning system. In this study, DLG and transmission factor of HD-MLC were measured using detector with different measuring volumes, and the accuracy of the treatment plans was evaluated according to the DLG values. DLG was measured using the dynamic sweeping gap method with Semiflux3D and MicroDiamond detectors. Then, 10 radiation treatment plans were generated to optimize the DLG value and compared with the measurement results. Photon energies 6, 8, 10 MV, the DLG measured by Semiflux3D were 0.76, 0.83, and 0.85 mm, and DLG measured by MicroDiamond were 0.78, 0.86, and 0.9 mm. All plans were measured by portal dosimetry and analyzed using Gamma Evaluation. In the 6 MV photon beams, the average gamma passing rate were 94.3% and 98.4% for DLG 0.78 mm and 1.15 mm. In the 10 MV photon beam, the average gamma passing rate were 91.2% and 97.6% for DLG 0.9 mm and 1.25 mm. HD-MLC needs accurate modeling in the treatment planning system. DLG could be used measured data using small volume detector. However, for better radiation therapy, DLG should be optimized at the commissioning stage of LINAC.

• Smart Structures and Systems
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• v.19 no.5
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• pp.553-565
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• 2017

Structural modeling of unencapsulated ionic polymer metal composite (u-IPMC) actuators that are used for flapping the insect scale-flapping wing of micro air vehicles (FMAV) in dry environmental conditions is carried out. Structural modeling for optimization of design parameters for retention of water, maximize actuation performance and to study the influence of water activity on the actuation characteristics of u-IPMC is explored for use in FMAV. The influence of equivalent weight of Nafion polymer, cations, concentration of cations, pre-treatment procedures on retention of water of u-IPMCs and on actuation parameters, flapping angle, flexural stiffness and actuation displacement are investigated. IPMC designed with Nafion having equivalent weight 900-1100, pre-heated at $30^{\circ}C$ and with sodium as the cations is promising for optimum retention of water and actuation performance. The actuation parameters while in operation in dry and humid environment with varying water activity can be tuned to desirable frequency, deflection, flap angle and flexural stiffness by changing the water activity and operational temperature of the environment.

• Wind and Structures
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• v.13 no.6
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• pp.519-528
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• 2010

A meteorological model, RAMS, and a commercial computational fluid dynamics (CFD) model, FLUENT are combined as a one-way off-line nested modeling system, namely, RAMS/FLUENT system. The system is experimentally applied in the wind simulation over a complex terrain, with which numerical simulations of wind field over Foyeding weather station located in the northwest mountainous area of Beijing metropolis are performed. The results show that the method of combining a meteorological model and a CFD model as a modeling system is reasonable. In RAMS/FLUENT system, more realistic boundary conditions are provided for FLUENT rather than idealized vertical wind profiles, and the finite volume method (FVM) of FLUENT ensures the capability of the modeling system on describing complex terrain in the simulation. Thus, RAMS/FLUENT can provide fine-scale realistic wind data over complex terrains.

• The Journal of the Acoustical Society of Korea
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• v.39 no.2
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• pp.87-97
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• 2020

In this paper, the design of piezoelectric Micro-machined Ultrasonic Transducer (pMUT) for wideband ultrasonic radiation in air was investigated. One of the methods to achieve wide frequency bandwidth in single device is modeling the transducer to multi-resonance system. The new pMUT was designed as a multi-resonance system with the addition of a suitable acoustic structure to the front and back of a thin film structure. A new pMUT consisting of thin film parts, radiation parts, and packaging parts is designed with a Lumped Parameter Model (L.P.M). Finally, it was validated as a Finite Element Method (FEM) simulation. The final designed pMUT achieved a frequency band of 102 kHz ~ 132 kHz (-3 dB).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1202-1208
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• 2009

An inverse finite element (FE) model parameter estimation algorithm can be used to characterize mechanical properties of biological tissues. Using this algorithm, we can consider the influence of material nonlinearity, contact mechanics, complex boundary conditions, and geometrical constraints in the modeling. In this study, biomechanical experiments on macro and micro samples are conducted and characterized with the developed algorithm. Macro scale experiments were performed to measure the force response of porcine livers against mechanical loadings using one-dimensional indentation device. The force response of the human liver cancer cells was also measured by the atomic force microscope (AFM). The mechanical behavior of porcine livers (macro) and human liver cancer cells (micro) were characterized with the algorithm via hyperelastic and linear viscoelastic models. The developed models are suitable for computing accurate reaction force on tools and deformation of biomechanical tissues.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.215-218
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• 2007

Internal Ballistic modeling and performance prediction for solid propellant micro thruster was performed with heat loss to the chamber wall as an important factor of miniaturization. Simple l-D end-burner type thruster and general HTPB-AP type composite propellant were selected for computation model. The results showed that the performance loss with the heat loss to the surroundings becomes larger as the surface-to-volume ratio is increased. In this case, the total impulse was reduced about 3% of the case in adiabatic condition.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.612-614
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• 1997

Silicon based micro mirror array is a highly efficient component for use in optical applications such as adaptive optical systems and optical correlators. A micro mirror array designed, fabricated and tested here is consisted of $5{\times}5$ single layer polysilicon, electrostatically driven actuators. In this paper, deflection characteristics and pull-in behavior of the actuators for analog control was studied and particularly, the influence of the residual stress in flexure beams for the restorative force of actuators was considered. The springs are modeled as a residual stress-free spring and a spring with residual stress. In calculation, a mirror with the residual stress-free springs has 30.3N/m spring constant and 31.1V pull-in voltage. On the other hand, a mirror with the stressed springs has 23.6N/m and 27.4V respectively. The experimental result, which is 20.5N/m and 25.5V, shows that the stressed springs ore well modeled.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.7
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• pp.919-926
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• 2002

Down scaled combustor undergoes increased heat loss that results in incomplete combustion or quenching of the flame as a consequence. Therefore, effect of enhanced heat loss should be understood to design a MEMS scale combustion devices. Existing combustion models are inadequate for micro combustors because they were developed for analysis of regular scale combustor where heat loss can be ignored during the flame propagation. In this research a combustion model is proposed in order to estimate the heat loss and predict quenching limit of flame in a down scaled combustor. Heat loss in the burned region is expressed in a convective form as a product of wall surface area, heat transfer coefficient and temperature difference. Comparison to the measurements showed satisfactory agreement of the pressure and temperature drop. Quenching is accounted for by introducing a correlation of quenching parameter and heat loss. The present model predicted burnt fraction of gases with reasonable accuracy and proved to be applicable in thermal design of a micro combustor.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.3
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• pp.229-236
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• 2013

This paper presents the experimental investigation of a biplane micro air vehicle. The effects of geometric parameters, gap, stagger, and decalage angle are investigated at low Reynolds number (~150,000) in a low-speed wind tunnel. A rigid flat plate with an aspect ratio of one and square planform shape is used to evaluate all three geometric parameters. The side dimension of the single flat plate is 0.15 m. The goal is to find an optimal biplane configuration that should exceed monoplane performance by generating high lift and flying as slow as possible, in order to capture high-quality visual recordings. This configuration will directly help to fly at a lower velocity and to make tighter turns that are advantageous in restricted environments. The results show that the aerodynamic performance of the biplane MAV is significantly enhanced through the combination of gap and stagger effects. A performance comparison demonstrates the superiority of the optimal biplane configuration compared to a monoplane in cruise and glide phases. Moreover, no significant compromise is found for the range, endurance, and climb performance.