• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.724-729
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• 2007

The study is a structure analysis by applying the output torque and tangential force on 47 ton excavator drive motor gear carrier. The finite element analysis for 3D model is performed by ABAQUS/Standard. We made an estimate by evaluating the results of the finite element analysis.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
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• pp.1041-1044
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• 2003

In this paper, a new CMOS fully integrated frequency-to-digital converter is proposed. The operation of the proposed circuit is based on a pulse-shrinking delay element. In the proposed circuit, a resolution of the converted digital output can be easily improved by increasing the number of the pulse-shrinking element. Also the input frequency range can be easily changed through controlling bias voltage in the pulse-shrinking element. The simulation of the designed circuit carried out by HSPICE using the CMOS 0.35${\mu}{\textrm}{m}$ process technology.

• 한국농촌건축학회논문집
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• 제22권3호
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• pp.41-48
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• 2020

The purpose of this research is to manage the physical sectors systematically, needed for the selection and direction of declining areas, such as urban regeneration and revitalization projects, by grading the density of decline indicators of buildings in small and medium cities. In five small and medium-sized cities in Jeollanam-do, the data were divided into three stages according to the density, according to the use, structure, and age of the building. Rating by element of Census Output Area, detailed designation, and management of declining areas in small and medium-sized cities are required, rather than setting the scope of declining areas based on administrative districts. It is also necessary to manage cities through complex and intra-element phasing rather than single elements in defining physical decline. The analysis based on the complex factors and boundary of the Census Output Area is meaningful in order to maintain and manage such cities in a more detailed and precise manner according to such characteristics of each region.

• 한국정보통신학회논문지
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• 제14권1호
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• pp.177-182
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• 2010

포워드 컨버터는 광범위하게 사용되는 파워공급기 중의 하나이다. 본 논문은 부하가 다양하게 변동하는 환경에서 출력 전압의 변동을 최소화하는 포워드 컨버터의 최적회로 소자 값을 구하기 위한 파라메터 동조방법을 제시한다. 위상여유의 개념을 사용하는 기존의 방법은 최적의 위상여유를 통해 출력 전압 응답에서 부분적인 성능 개선이 이루어지도록 확장되었다. 이를 위해서 위상여유를 동조 파라메터로 두고 유전자 알고리즘을 사용하여 최적화하였다. 다음으로 회로 소자 값들을 동조 파라메터로 직접 선택하고, 역시 유전자 알고리즘으로 최적화하여 포워드 컨버터의 출력 전압 제어에서 매우 개선된 성능을 갖도록 하였다.

• 한국전기전자재료학회논문지
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• 제29권2호
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• pp.84-89
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• 2016

We present the results of a study of a piezoelectric generator that generates electricity by the application of tension to an element. A device is named "EYE-type generator". The EYE-type generator consists of a rectangular ceramic and two elastic body plates that are attached to upper and lower surfaces of a ceramic. If tension is applied to both ends of the elastic body, that tension is transformed to pressure on the ceramic through a change in the form of the elastic body, causing a piezoelectric effect whereby electricity is generated by the ceramic. This generator is relatively durable because a forces are not applied directly to the ceramic. We examined dependencies of the generator's output characteristics on the size of the ceramic and elastic body. A resonance and output characteristics were analyzed by using a finite element method. The generator was fabricated based on results of the analysis, and this was attached to a frequency-controllable vibrator to measure the output characteristics. The measured results were compared with results of the simulation, and the results pointed to the practicality of the design.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2003년도 제27회 추계학술대회
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• pp.53-53
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• 2003

For evaluating the feasibility of treating recurrent lesions in the vaginal cuff and cervix by hyperthermia, ultrasound applicators were designed, constructed, and characterized. For the treatment A half-cylindrical transducer Cd=1cm, length=lcm) and cylindrical transducer (d=2.5cm, length= 1.5cm) were used to construct ovoid type and cylindrical applicators. For the ovoid type applicator, each element was operated at 1.5MHz and characterized by measuring transducer efficiency and acoustic power distribution. Thermocouple probes were used to measure the temperature rise in phantom. The element sizes used in this study were selected to be comparable for high dose rate brachytherapy colpostat applicator. Each element was powered separately to achieve a desired temperature pattern in a target. The acoustic output power as a function of applied electric power of the element 1 and 2 was linear over this 1 to 40 W range and efficiencies were 32.2${\pm}$3.4% and 46.2${\pm}$0.8%, respectively. The temperature measurements in phantom showed that 6$^{\circ}C$ temperature rise was achieved at 2 cm from the applicator surface. As a conclusion, the ability of the ultrasound colpostat applicator to be used for hyperthermia was demonstrated by measuring acoustic output power, ultrasound field distribution, and temperature rise in phantom. Based on the characteristics of this applicator, it has the potential to be useful for inducing hyperthermnia to the vaginal cuff in clinic.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.601-613
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• 2017

An adjoint-based error estimation and mesh adaptation study is conducted for two-dimensional viscous flows on unstructured hybrid meshes. The error in an integral output functional of interest is estimated by a dot product of the residual vector and adjoint variable vector. Regions for the mesh to be adapted are selected based on the amount of local error at each nodal point. Triangular cells in the adaptive regions are refined by regular refinement, and quadrangular cells near viscous walls are bisected accordingly. The present procedure is applied to single-element airfoils such as the RAE2822 at a transonic regime and a diamond-shaped airfoil at a supersonic regime. Then the 30P30N multi-element airfoil at a low subsonic regime with a high incidence angle (${\alpha}=21deg.$) is analyzed. The same level of prediction accuracy for lift and drag is achieved with much less mesh points than the uniform mesh refinement approach. The detailed procedure of the adjoint-based mesh refinement for the multi-element airfoil case show that the basic flow features around the airfoil should be resolved so that the adjoint method can accurately estimate an output error.

• Smart Structures and Systems
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• 제26권6호
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• pp.681-692
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• 2020

Conventional Piezoelectric Energy Harvesters (CPEH) have been extensively studied for maximizing their electrical output through material selection, geometric and structural optimization, and adoption of efficient interface circuits. In this paper, the performance of Stepped Piezoelectric Energy Harvester (SPEH) under harmonic base excitation is studied analytically, numerically and experimentally. The motivation is to compare the energy harvesting performance of CPEH and SPEHs with the same characteristics (resonant frequency). The results of this study challenge the notion of achieving higher voltage and power output through incorporation of geometric discontinuities such as step sections in the harvester beams. A CPEH consists of substrate material with a patch of piezoelectric material bonded over it and a tip mass at the free end to tune the resonant frequency. A SPEH is designed by introducing a step section near the root of substrate beam to induce higher dynamic strain for maximizing the electrical output. The incorporation of step section reduces the stiffness and consequently, a lower tip mass is used with SPEH to match the resonant frequency to that of CPEH. Moreover, the electromechanical coupling coefficient, forcing function and damping are significantly influenced because of the inclusion of step section, which consequently affects harvester's output. Three different configurations of SPEHs characterized by the same resonant frequency as that of CPEH are designed and analyzed using linear electromechanical model and their performances are compared. The variation of strain on the harvester beams is obtained using finite element analysis. The prototypes of CPEH and SPEHs are fabricated and experimentally tested. It is shown that the power output from SPEHs is lower than the CPEH. When the prototypes with resonant frequencies in the range of 56-56.5 Hz are tested at 1 m/s2, three SPEHs generate power output of 482 μW, 424 μW and 228 μW when compared with 674 μW from CPEH. It is concluded that the advantage of increasing dynamic strain using step section is negated by increase in damping and decrease in forcing function. However, SPEHs show slightly better performance in terms of specific power and thus making them suitable for practical scenarios where the ratio of power to system mass is critical.

• 한국철도학회논문집
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• 제6권3호
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• pp.174-178
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• 2003

This paper presents the development of 2-dimensional discrete element algorithm to generate circle and line elements for the simulation of the ballast and sleeper in railway. An example of randomly distributed circle elements show a good applicability of this algorithm for the modeling of the behaviors of ballast. The output about unbalaned force, particle velocity, and total energy conservation from the code is evaluated to check if the calculation is conducted properly.

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권6호
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• pp.220-223
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• 2003

In this paper, a new frequency-to-digital converter without an analog element is proposed. The proposed circuit consists of pulse-shrinking elements, latches and D flip-flops, and the operation is based on frequency comparison by the pulse-shrinking element. In the proposed circuit, the resolution of digital output can be easily improved by increasing the number of the pulse-shrinking elements. The FDC performance is improved in viewpoints of operating speed and chip area. In designed FDC, error of frequency-to-digital conversion is less than 0.1 %.