• Proceedings of the KIPE Conference
• /
• 2015.07a
• /
• pp.377-378
• /
• 2015

본 논문에서는 유기랭킨 사이클(organic rankine cycle: ORC) 발전 시스템에서 터빈과 발전기의 속도를 추정하는 방법을 제안한다. 다이오드 정류기에 의해 왜곡된 발전기 3상 단자 전압은 PLL 기법을 이용한 속도추정의 성능을 저하시키므로, 정상분 추출과 맥동성분 제거를 위한 상태관측기와 주파수 가변형 PR 제어기를 동기좌표계 PLL 기법에 적용하여 발전기의 속도를 추정한다. 제안하는 터빈과 발전기의 속도추정 방법은 실험 결과를 통해 그 성능을 검증한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.299-299
• /
• 2007

This paper presents an omni-directional piezoelectric actuator which utilizes only one actuator. The actuator has a simple structure of cone type consists of two piezoelectric ceramics of ring type and electrodes divided four segments and a stainless steel body. To find the optimal operating condition of the actuator, the frequency characteristics of the actuator are analyzed by ATILA, FEM and measured by Impedance Analyzer. We have also developed a stage using the omni-directional actuator and an actuator driver circuit to create four sinusoidal waves with a variable frequency and phase difference.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.10
• /
• pp.1073-1079
• /
• 1998

The potential energy surface (PES) of the non-identical SN2 reactions, F- + CH3Cl → FCH3 + Cl and (H2O)F + CH3Cl → FCH3 + Cl-(H2O), were investigated with ab initio MO calculations. The ab initio minimum energy reaction path (MERP) of the F- + CH3Cl → FCH3 + Cl- was obtained and it was expressed with an intermediate variable t. The ab initio PES was obtained near around t. Analytical potential energy function (PEF) was determined as a function of the t in order to reproduce the ab initio PES. Based on Morse-type potential energy function, a Varying Repulsive Cores Model (VRCM) was proposed for the description of the bond forming and the bond breaking which occur simultaneously during the SN2 reaction. The MERP calculated with the PEF is well agreed with the ab initio MERP and PEF could reproduce the ab initio PES well. The potential parameters for the interactions between the gas phase molecules in the reactions and water were also obtained. ST2 type model was used for the water.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2019.05a
• /
• pp.159-159
• /
• 2019

In this study, the simulation of sediment deposition at Sangju weir reservoir, South Korea, was carried out using artificial neural networks. The ANNs have typically been used in water resources engineering problems for their robustness and high degree of accuracy. Three basic variables namely turbid water inflow, outflow, and water stage have been used as input variables. It was found that ANNs were able to establish valid relationship between input variables and target variable of sedimentation. The R value was 0.9806, 0.9091, and 0.8758 for training, validation, and testing phase respectively. Comparative analysis was also performed to find optimum structure of ANN for sediment deposition prediction. 3-14-1 network architecture using BR algorithm outperformed all other combinations. It was concluded that ANN possess mapping capabilities for complex, non-linear phenomenon of reservoir sedimentation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.32 no.2
• /
• pp.141-146
• /
• 2019

Non-emissive LCDs need a backlight, and have difficulty implementing wide viewing angles due to differences in phase retardation depending on the behavior of the liquid crystals. Although wide viewing angles are good characteristics for devices such as TVs, they are not good for mobile devices. In this paper, we propose ways to design diffusers with ELC lenses to achieve wide and narrow viewing angles depending on the circumstances. A study was conducted on optimizing the design of a liquid lens diffuser with the same light as that for an OLED, by extracting design factors that affect the performance of the diffuser and applying the Taguchi method to them.

• Current Optics and Photonics
• /
• v.3 no.3
• /
• pp.243-247
• /
• 2019

We have developed a compact, wavelength-selectable, Q-switched Nd:YAG laser at mid ultraviolet for chemical warfare agent detection. The fundamental wave at 1064 nm is delivered by a pulsed solid state laser incorporating with a square-type Nd:YAG rod in a resonator closed by two crossed Porro prisms for environmental reliability. The output energy at 213 nm ($5{\omega}$) and 266 nm ($4{\omega}$) by ${\chi}^{(2)}$ process in the sequentially disposed BBO crystals are measured to be 6.8 mJ and 15.1 mJ, respectively. The output wavelength is selected for $5{\omega}$ and $4{\omega}$ by a motorized wavelength switch. The energy ratio of the $5{\omega}$ to the $4{\omega}$ is varied from 0.05 to 0.85 by controlling the phase matching temperature of the nonlinear crystal for sum-frequency generation without change of the output pulse parameters.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.61.4-61.4
• /
• 2019

The key science goal of the KMTNet Supernova Program (KSP) is to detect and study the early explosions of supernovae using one fifth of the KMTNet time. The BVI-band observations of the nearby target fields mostly closer than 30 Mpc distance and the follow-up spectroscopy provide valuable information on the early phase of the supernovae. These data can also be used for the studies of optical transients such as novae, dwarf novae, variable stars, and active galactic nuclei. Stacked images of several hundred images obtained from the time domain observations can be used for the search of low surface brightness galaxies reaching $28mag\;arcsec^{-2}$. Results and status of the KSP including ${\geq}20$ infant supernovae and ${\geq}100$ faint dwarf galaxies will be presented in this talk.

• Journal of KIBIM
• /
• v.12 no.1
• /
• pp.10-22
• /
• 2022

Prefabricated bridges require strict management of tolerance during fabrication and assembly. In this paper, digital engineering models for prefabricated bridge components such as deck, girder, pier, abutment are suggested to support information delivery through the life-cycle of the bridge. Rule-based modeling is used to define geometry of the members considering variable dimensions due to fabrication and assembly error. DfMA(design for manufacturing and assembly) provides the rules for ease of fabrication and assembly. The digital engineering model consists of geometry, constraints and corresponding parameters for each phase. Alignment and control points are defined to manage tolerances of the prefabricated bridge during fabrication and assembly. Quality control by digital measurement of dimensions was also considered in the model definition. A pilot bridge was defined virtually to validate the suggested digital engineering models. The digital engineering models for DfMA showed excellent potential to realize prefabricated bridges.

• Coupled systems mechanics
• /
• v.12 no.4
• /
• pp.337-364
• /
• 2023

The Rayleigh wave propagation is considered in the structure of the functionally graded piezoelectric material (FGPM) layer over the elastic substrate. The elastic substrate loosely bonds the layer through a corrugated interface, whereas its upper boundary is also corrugated but stress-free. Additionally, the solutions for the FGPM layer and substrate are derived using the fundamental variable separable approach to convert the partial differential equation to an ordinary differential equation. The results with boundary conditions lead to dispersion relations for the electrically open and electrically short cases in the determinant form. The outcomes have been numerically analyzed using a specific model. The findings were presented in the form of graphs, which were created using Mathematica 7. Graphs are plotted for variations in wavenumber and phase velocity. The outcomes may help measure interface defects and design Surface Acoustic Wave (SAW) devices.

• Korean Journal of Radiology
• /
• v.24 no.8
• /
• pp.795-806
• /
• 2023

Occupational lung diseases (OLD) are a group of preventable conditions caused by noxious inhalation exposure in the workplace. Workers in various industries are at a higher risk of developing OLD. Despite regulations contributing to a decreased incidence, OLD remain among the most frequently diagnosed work-related conditions, contributing to significant morbidity and mortality. A multidisciplinary discussion (MDD) is necessary for a timely diagnosis. Imaging, particularly computed tomography, plays a central role in diagnosing OLD and excluding other inhalational lung diseases. OLD can be broadly classified into fibrotic and non-fibrotic forms. Imaging reflects variable degrees of inflammation and fibrosis involving the airways, parenchyma, and pleura. Common manifestations include classical pneumoconioses, chronic granulomatous diseases (CGD), and small and large airway diseases. Imaging is influenced by the type of inciting exposure. The findings of airway disease may be subtle or solely uncovered upon expiration. High-resolution chest CT, including expiratory-phase imaging, should be performed in all patients with suspected OLD. Radiologists should familiarize themselves with these imaging features to improve diagnostic accuracy.