• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.474-479
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• 1998

In this paper, we present a mathematical model of the piezoelectric pump and its application to the automobile brake system. The piezoelectric pump consists of a multi-layered piezoelectric element a diaphragm, pumping values, resonant pipes and accumulators, and the maximum pumping power of 62W nab obtained in the previous experiments by using the piezoelectric element of 22mm diameter and 55.5mm length. A detailed mathematical model of the pump is derived here by considering the compressibility of the working oil, nonlinear characteristics of piezoelectric element, the time delay of pumping values' action and be on. The validity of the model is illustrated by comparing the experimental data and the simulation results. Using the mathematical model of the piezoelectric pump, a brake system for automobile disk brake is also simulated in this paper. The brake system consists of a piezoelectric pump as a power source, calipers and its piston to generate brake force, and a three position solenoid value to change the brake situation. It is shown that 15mm/sec of piston speed and 20kN of piston force are obtained by using the piezoelectric element of 33mm diameter and 55.5mm length.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.1
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• pp.98-106
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• 1996

An irrigation scheduling model, IRIS developed to evaluate irrigation demand and irrigation time for upland crops. For IRlS modeling the soil moisture simulation model, SWATRER was adopted and modified. The developed model, IRIS operated under 5 different soil moisture level that is 20%, 40%, 60%, 80% of available soil moisture and optimum soil moisture level, OSML, which is different about the growing stage and no rainfall condition during growing period. As a result for IRIS simulation, irrigation demand for 5 different soil moisture level was 332.3, 409.8, 569.3, 732.2, 539.3mm, irrigation number was 5, 8, 18, 54, 16 times and irrigation interval during peak time of consumptive use was 20, 13, 6, 2, 6 days respectively. It is appeared that the higher soil moisture level the more irrigation demand and irrigation number and the higher soil moisture level the less irrigation interval.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.3
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• pp.309-323
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• 2006

We focus on the improvement in the simulation of sea surface wind over complex coastal area located in the southeastern Korea. In this study, it was carried out sensitivity experiment based on PBL schemes and dynamic frame of MM5 and WRF. Two widely used PBL parameterization schemes were chosen : Medium-Range Forecast (MRF) and Mellor-Yamada-Janjic (MYJ). Thereafter, two cases of sea fog days with weak wind speed and typhoon days with strong wind speed were simulated and analyzed. The result of experiments indicated that wind fold of WRF model was shown more similar distribution with observational data, compared with that of MM5. Simulation of sea surface wind during sea fog days with weak wind speed and typhoon days with strong wind speed were shown similar horizontal distribution with observational data using MYJ and MRF PBL schemes of WRF model, respectively. Horizontal distribution of sea surface wind was more sensitive according to dynamic frame and PBL Schemes of model during sea fog days and typhoon days, respectively.

• Journal of Power System Engineering
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• v.19 no.1
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• pp.76-82
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• 2015

An analysis model is developed using a commercial software 'simulationX' for designing hydraulic-pneumatic system of heave compensator for offshore drilling operations. Reliability verification of the analysis model for the test equipment of 1/5 scale compensator was conducted by comparing test results and simulation results. An analysis of full scale heave compensator is developed on the basis of verified a model. Then, the results of simulation were analyzed to obtain following conclusion. The displacement of crown block about excitation input amplitude (${\pm}3,000mm$) of the steward platform using a 'simulationX' is attenuated under ${\pm}35mm$, and the compensation rate is 98.7%. In this study, goal of a compensation rate is more than 95%. The previously results are satisfied with the objectives of compensation rate.

• Structural Engineering and Mechanics
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• v.85 no.3
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• pp.337-351
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• 2023

In this paper, the shear behavior of soft filling in rectangular-hollow concrete specimens was simulated using the 2D particle flow code (PFC2D). The laboratory-measured properties were used to calibrate some PFC2D micro-properties for modeling the behavior of geo-materials. The dimensions of prepared and modeled samples were 100 mm×100 mm. Some disc type narrow bands were removed from the central part of the model and different lengths of bridge areas (i.e., the distance between internal tips of two joints) with lengths of 30 mm, 50 mm, and 70 mm were produced. Then, the middle of the rectangular hollow was filled with cement material. Three filling sizes with dimensions of 5 mm×5 mm, 10 mm×5 mm, and 15 mm×5 mm were provided for different modeled samples. The parallel bond model was used to calibrate and re-produce these modeled specimens. Therefore, totally, 9 different types of samples were designed for the shear tests in PFC2D. The shear load was gradually applied to the model under a constant loading condition of 3 MPa (σc/3). The loading was continued till shear failure occur in the modeled concrete specimens. It has been shown that both tensile and shear cracks may occur in the fillings. The shear cracks mainly initiated from the crack (joint) tips and coalesced with another one. The shear displacements and shear strengths were both increased as the filling dimensions increased (for the case of a bridge area with a particular fixed length).

• Journal of the Korean Society of Radiology
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• v.12 no.7
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• pp.801-806
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• 2018

Germanium crystals have a dead layer that causes efficiency deterioration because the layer is not useful for detection but strongly weakens the photons. Thus, when the data provided by the manufacturer is used in the detector simulation model, there is a slight difference between the calculated efficiency and the measured efficiency.The shape and dimensions of the high purity germanium (HPGe) detector were determined by CT scans to accurately characterize the shape for the Monte Carlo roll simulation. It is found that the adjustment of the dead layer is a good match with the relative deviation of ${\pm}3%$ between the measurement efficiency and the simulation efficiency at the energy range of 50 - 1500 keV. Simulation data were compared by varying the thickness of the dead layer. The new Monte Carlo simulations were compared with the experimental results to obtain new blank layer thicknesses. The difference in dead layer results for the 1.5 mm thick end cap simulation model in 1.4 and 1.6 mm thick End Cap simulation models was a systematic error due to the accuracy of the end cap dimensions. After considering all errors including statistical errors and systematic errors, the thickness of the detector was calculated as $1.02{\pm}0.14mm$. Therefore, it was confirmed that the increase in the thickness of the dead layer causes the effect to be effected on the efficiency reduction.

• Journal of Electrical Engineering and information Science
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• v.2 no.6
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• pp.202-207
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• 1997

Design and fabrication issues for an L-band GaAs Monolithic Microwave Integrated Circuit(MMIC) Voltage Controlled Oscillator(VCO) as a component of Personal Communications Systems(PCS) Radio Frequency(RF) transceiver are discussed. An ion-implanted GaAs MESFET tailored toward low current and low noise with 0.5mm gate length and 300mm gate width has been used as an active device, while an FET with the drain shorted to the source has been used as the voltage variable capacitor. The principal design was based on a self-biased FET with capacitive feedback. A tuning range of 140MHz and 58MHz has been obtained by 3V change for a 600mm and a 300mm devices, respectively. The oscillator output power was 6.5dBm wth 14mA DC current supply at 3.6V. The phase noise without any buffer or PLL was 93dB/1Hz at 100KHz offset. Harmonic balance analysis was used for the non-linear simulation after a linear simulation. All layout induced parasitics were incorporated into the simulation with EEFET2 non-linear FET model. The fabricated circuits were measured using a coplanar-type probe for bare chips and test jigs with ceramic packages.

• Journal of IKEEE
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• v.27 no.4
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• pp.650-656
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• 2023

This paper implements a channel model for mmWave bands using an NS-3-based 5G system-level simulator and analyzes the reliability and validity of the implemented model through RF performance verification. The channel model for RF performance verification in the mmWave bands consider parameters such as characteristics defined in 3GPP TR 38.901, beam-forming, antenna configuration, scenarios, among others. Furthermore, the simulation results verify compliance within the ranges permitted by the 3GPP standards and verify reliability in indoor environmental scenarios by exploiting the Radio Environment Map (REM). Therefore, the channel model implemented in this study is applicable to the actual design and establishment of 5G networks, presenting a method to evaluate and validate RF performance by adjusting various parameters.

• Journal of the Semiconductor & Display Technology
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• v.11 no.4
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• pp.37-42
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• 2012

Nanoimprint lithography (NIL) has attracted broad interest as a low cost method to define nanometer scale patterns in recent years. A major disadvantage of thermal NIL is the thermal cycle, that is, heating over glass transition temperature and then cooling below it, which requires a significant amount of processing time and limits the throughput. One of the methods to overcome this disadvantage is to improve the cooling performance in NIL process. In this paper, the performance of the cooling system of thermal NIL is numerically investigated by SolidWorks Flow Simulation program. The calculated temperatures of nanoimprint device were verified by the measurements. By using the analysis model, the effects of the change of flow velocity and cooler location on the cooling performance are investigated. For the 6 cases (0.1 m/s, 0.5 m/s, 1 m/s, 3 m/s, 5 m/s, 10 m/s) of flow velocity and for the 6 cases of distances (50 mm, 40 mm, 30 mm, 20 mm, 10 mm, 1 mm) of cooler location, the heat conjugated flow analyses are performed and discussed.

• Structural Engineering and Mechanics
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• v.67 no.5
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• pp.493-504
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• 2018

In this paper, the tensile failure behaviour of transversally bedding layers was numerically simulated by using particle flow code in two dimensions. Firstly, numerical model was calibrated by uniaxial, Brazilian and triaxial experimental results to ensure the conformity of the simulated numerical model's response. Secondly, 21 circular models with diameter of 54 mm were built. Each model contains two transversely bedding layers. The first bedding layer has low mechanical properties, less than mechanical properties of intact material, and second bedding layer has high mechanical properties, more than mechanical properties of intact material. The angle of first bedding layer, with weak mechanical properties, related to loading direction was $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$ and $90^{\circ}$ while the angle of second layer, with high mechanical properties, related to loading direction was $90^{\circ}$, $105^{\circ}$, $120^{\circ}$, $135^{\circ}$, $150^{\circ}$, $160^{\circ}$ and $180^{\circ}$. Is to be note that the angle between bedding layer was $90^{\circ}$ in all bedding configurations. Also, three different pairs of the thickness was chosen in models; i.e., 5 mm/10 mm, 10 mm/10 mm and 20 mm/10 mm. The result shows that In all configurations, shear cracks develop between the weaker bedding layers. Shear cracks angel related to normal load change from $0^{\circ}$ to $90^{\circ}$ with increment of $15^{\circ}$. Numbers of shear cracks are constant by increasing the bedding thickness. It's to be note that in some configuration, tensile cracks develop through the intact area of material model. There is not any failure in direction of bedding plane interface with higher strength.