• Journal of the Korean Applied Science and Technology
• /
• v.34 no.3
• /
• pp.562-567
• /
• 2017

The organic light-emitting diodes are fabricated with six anthracene derivatives containing simple substituents such as phenyl or naphthyl group. The device structure is as in the following: Indium tin oxide (ITO) (180 nm)/4,4-4,4',4"-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (2-TNATA) (30 nm)/4,4'-bis[N-(1-naphthyl)-N-phenyl-1-amino] biphenyl (NPB) (20 nm)/Emitting compound (30 nm)/2,2',2"-(1,3,5-Benzinetriyl)-tris (1-phenyl-1-H-benz-imidazole) TPBi (40 nm)/lithium quinolate (Liq) (2 nm)/Al (100 nm). In the emitting layer the anthracene derivatives are used without any dopant. All the six devices show blue emissions. Among the tested diodes, the one with 9-(2-naphthyl)-10-(p-tolyl) anthracene (2-NTA) exhibited luminous efficiency, power and external quantum efficiencies of 3.26 cd/A, 0.98 lm/A, 2.8 % at $20mA/cm^2$.

• Journal of Power Electronics
• /
• v.15 no.6
• /
• pp.1480-1488
• /
• 2015

In this paper, a revolutionary buck converter is proposed with soft-switching technology, which is realized by a coupled inductor. Both zero-voltage switching (ZVS) of main switch and zero-current switching (ZCS) of freewheeling diode are achieved at turn on and turn off without using any auxiliary circuits by the resonance between the parasitic capacitor and the coupled inductor. Furthermore, the peak voltages of the main switch and the peak current of the freewheeling diode are significantly reduced by the coupled inductor. As a result, the proposed converter has the advantages of simple circuit, convenient control, low consumption and so on. The detailed operation principles and steady-state analysis of the proposed ZVS-ZCS buck converter are presented, and detailed power loss analysis and some simulation results are also included. Finally, experimental results based on a 200-W prototype are provided to verify the theory and design of the proposed converter.

• Journal of Positioning, Navigation, and Timing
• /
• v.8 no.4
• /
• pp.153-164
• /
• 2019

This paper presents the development of an end-to-end numerical simulator for signal design of the next generation global navigation satellite system (GNSS). The GNSS services are an essential element of modern human life, becoming a core part of national infra-structure. Several countries are developing or modernizing their own positioning and timing system as their demand, and South Korea is also planning to develop a Korean Positioning System (KPS) based on its own technology, with the aim of operation in 2034. The developed simulator consists of three main units such as a signal generator, a channel unit, and a receiver. The signal generator is constructed based on the actual navigation satellite payload model. For channels, a simple Gaussian channel and land mobile satellite (LMS) multipath channel environments are implemented. A software receiver approach based on a commercial GNSS receiver model is employed. Through the simulator proposed in this paper, it is possible to simulate the entire transceiver chain process from signal generation to receiver processing including channel effect. Finally, numerical simulation results for a simple example scenario is analyzed. The use of the numerical signal simulator in this paper will be ideally suited to design a new navigation signal for the upcoming KPS by reducing the research and development efforts, tremendously.

• International Journal of High-Rise Buildings
• /
• v.5 no.3
• /
• pp.167-176
• /
• 2016

This paper describes a large tuned mass damper (TMD) developed as an effective seismic control device for an existing highrise building. To realize this system, two challenges needed to be overcome. One was how to support a huge mass that has to move in any direction, and the second was how to control mass displacement that reaches up to two meters. A simple pendulum mechanism with strong wires was adopted to solve the first problem. As a solution to the important latter problem, we developed a high-function oil damper with a unique hydraulic circuit. When the mass velocity reaches a certain value, which was predetermined by considering the permissible displacement, the damper automatically and drastically increases its damping coefficient and limits the mass velocity. This velocity limit function can effectively and stably control the mass displacement without any external power. This paper first examines the requirements of the TMD using a simple model and clarifies the constitution of the actual TMD system. Then the seismic upgrading project of an existing high-rise building is outlined, and the developed TMD system and the results of performance tests are described. Finally, control effects for design earthquakes are demonstrated through response analyses and construction progress is introduced.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• v.1 no.1
• /
• pp.13-23
• /
• 2001

Most current machine vision systems for industrial inspection were developed with one specific task in mind. Hence, these systems are inflexible in the sense that they cannot easily be adapted to other applications. In this paper, a general vision system framework has been developed that can be easily adapted to a variety of industrial web inspection problems. The objective of this system is to automatically locate and identify \\\"defects\\\" on the surface of the material being inspected. This framework is designed to be robust, to be flexible, and to be as computationally simple as possible. To assure robustness this framework employs a combined strategy of top-down and bottom-up control, hierarchical defect models, and uncertain reasoning methods. To make this framework flexible, a modular Blackboard framework is employed. To minimize computational complexity the system incorporates a simple multi-thresholding segmentation scheme, a fuzzy logic focus of attention mechanism for scene analysis operations, and a partitioning if knowledge that allows concurrent parallel processing during recognition.cognition.

• Journal of Positioning, Navigation, and Timing
• /
• v.7 no.1
• /
• pp.25-35
• /
• 2018

This paper describes the measurement of pulse positioning (input time) to calculate a time of arrival (TOA) that takes from transmitting a signal from the target of multilateration (MLAT) system to receiving the signal at the receiver. In this regard, this paper analyzes performances of simple threshold method and level adjust system (LAS) method, which is one of the adaptive threshold detector (ATD) methods, among many methods to calculate pulse positioning of signal received at the receiver. To this end, Cramer-rao lower bound (CRLB) with regard to pulse positioning, which was measured when signals transmitted from a transponder mounted at the target were received at the receiver, was induced and then deviation sizes with regard to pulse positioning, which was measured with simple threshold and LAS methods through MATLAB simulations, were compared. Next, problems occurring according to a difference in amplitude of signals inputted to each receiver are described when pulse positioning is measured at multiple receivers located at a different distance from the target as is the case in the MLAT system. Furthermore, LAS method to resolve the problems is explained. Lastly, this study analyzes whether a pulse positioning error occurring due to the signal noise satisfies the requirement (6 nsec. or lower) recommended for the MLAT system when using these two methods.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.23 no.11
• /
• pp.9-21
• /
• 2009

This paper proposes the alternative observer and controller design scheme based on T-S fuzzy model. Nonlinear systems are represented by fuzzy models since fuzzy logic systems are universal approximators. In order to estimate the unmeasurable states of a given unknown nonlinear system, T-S fuzzy modeling method is applied to get the dynamics of an observation system. T-S fuzzy system uses the linear combination of the input state variables and the modeling applications of them to various kinds of nonlinear systems can be found. The proposed indirect adaptive fuzzy observer based on T-S fuzzy model can cope with not only unknown states but also unknown parameters. The proposed controller is based on a simple output feedback method. Therefore, it solves the singularity problem, without any additional algorithm, which occurs in the inverse dynamics based on the feedback linearization method. The adaptive fuzzy scheme estimates the parameters and the feedback gain comprising the fuzzy model representing the observation system. In the process of deriving adaptive law, the Lyapunov theory and Lipchitz condition are used. To show the performance of the proposed observer and controller, they are applied to an inverted pendulum on a cart.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.1
• /
• pp.38-42
• /
• 2015

Polydimethylsiloxane (PDMS) is a widely used material for replicating micro-structures because of its transparency, deformability, and easy fabrication. At the nanoscale, however, it is hard to fill a nanohole template with uncured PDMS. This paper introduces several simple methods by changing the surface energy of a nanohole template and PDMS elastomer for replicating 100nm-scale structures. In the case of template, pristine anodic aluminum oxide (AAO), hydrophobically treated AAO, and hydrophillically treated AAO are used. For the surface energy change of the PDMS elastomer, a hydrophilic additive and dilution solvent are added in the PDMS prepolymer. During the molding process, a simple casting method is used for all combinations of the treated template and modified PDMS. The nanostructured PDMS surface was investigated with a scanning electron microscope after the molding process for verification.

• Korean System Dynamics Review
• /
• v.3 no.1
• /
• pp.79-104
• /
• 2002

A system dynamics project is going on for forecasting automobile market in Korea. The project is made up of three stages, and the first stage has been wrapped up. As the first attempt, most efforts have been focused on the sound foundation rather than the exact forecast. The model consists of three sectors; the supply sector, the demand sector, and the population sector. The supply sector is a simple stock and flow diagrams representing the supply capacities of all automobile types. The major effort is made on the demand sector and the population sector. The demands are divided into three categories; replacement demands, new demands, and additional demands. The model applies “one car per person" concept, and assumes there will be no additional demands for a while. The replacement demands are calculated based on a simple stock and flow diagram. The new demands are calculated via Bass models; each bass model represents a diffusion for each age group. The population is divided into 101 age groups (age 0 to age 100). The model has been calibrated with past 10 year data (1990 - 1999), and tested for the next two years (2000-2001). The results ware acceptable, although a fine tuning is required. Now the second stage is going on, and most of efforts are made how to incorporate the economic and cultural factors.

• Journal of the Optical Society of Korea
• /
• v.4 no.1
• /
• pp.66-70
• /
• 2000

The main problem of image projection on a transmission type holographic screen is color sepa-ration. And it can be overcome by using a long narrow slit type diffuser as a source of the object beam when we record the screen. But that screen is not optimized and so needs changing several conditions. To set up the system many complicate things should be taken into accounted so it is very important to analyze the basic structure by simple concepts and calculations. We designed the system so that recording and projection axis coincide in one line and showed that the analysis of the system is very simple. We did it by a 1st order paraxial approximation calculation and it was good enough to describe the system. The photo-emulsion layer shrinks after processing of the hologram. It induced unsatisfactory color matching at the viewing zone. To overcome this effect, we pre-checked the shrinkage rate of an emulsion layer by experiments and modified the recording set up to compensate for the amount of shrinkage.