• Steel and Composite Structures
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• v.2 no.5
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• pp.379-396
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• 2002

The paper describes the mechanical behavior of short concrete-filled steel tube (CFT) columns with circular section. The efficiency of the steel tube in confining the concrete core depending on concrete strength and the steel tube thickness was examined. Fifteen columns were tested to failure under concentric axial loading. Furthermore, a mechanical model based on the interaction between the concrete core and the steel tube was developed. The model employs a volumetric strain history for the concrete, characterized by the level of applied confining stress. The situation of passive confinement is accounted for by an incremental procedure, which continuously updates the confining stress. The post-yield behavior of the columns is greatly influenced by the confinement level and is related to the efficiency of the steel tube in confining the concrete core. It is possible to classify the post-yield behavior into three categories: strain softening, perfectly plastic and strain hardening behavior. The softening behavior, which is due to a shear plane failure in the concrete core, was found for some of the CFT columns with high-strength concrete. Nevertheless, with a CFT column, it is possible to use high-strength concrete to obtain higher load resistance and still achieve a good ductile behavior.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.168-171
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• 2005

The conception of the passive lossless snubber with the simpler is presented. Thus a necessity condition of the passive lossless soft switching converter with the simplest topology is directed. A novel passive regenerative snubber called soft snubber applied to a hard switching converter is proposed. The passive snubber consists of a snubber inductor, two snubber rectifiers, and a snubber capacitor. The losses are reduced by inserting a snubber inductor in the series path of the rectifier during it's turn off. It is so simple that can make energy reset or capacitor discharged directly without producing any current circulation. To show the superiority of this converter is verified through the experiment with a 640W, 100kHz prototype converter.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.2
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• pp.90-94
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• 2011

In this paper, the energy transfer is associated with high frequency band and try to analysis the rectifier circuit structure and characteristics and find ways to maximum efficiency. Input signal at 13.56MHz is converted output DC signal with the experiments and measurements. Rectifier cirsuits can be divided into the half-wave, full-wave, bridge rectifier circuit. Research to the present with the passive components are carried out with a focus on efficiency improvements. Factors affecting the efficiency of rectification is dependent on the characteristics of the device. In this experiment, about 70% efficiency can be measured. By using an improved device for high efficiency could be obtained higher efficiency.

• KIEAE Journal
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• v.13 no.3
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• pp.33-40
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• 2013

The world population is consuming more than 1/3 of the total energy for heating housings. Particularly in our country, 21% of the consumption energy is occupied by building section. Therefore, it is necessary to increase the energy efficiency in buildings, thus promoting a comfortable residential environment while minimizing energy consumption. Accordingly, this study presents considerations for implementing high-insulated and airtight passive houses. This study selected four houses with passive house design applied, performed building energy performance through PHPP2007, a German passive house design simulation program, and compared the building-specific heat loss and heat gain. As a result, the most vulnerable part to heat loss was turned out to be a window and the heat loss was caused by outer wall, roof, and ventilation. Accordingly, for the implementation of passive house, it is necessary to make a careful plan and airtight construction that are complementary to various parts through the energy performance analysis started from the design phase.

• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.1
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• pp.93-104
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• 2000

Passive agents participate in team activities passively, that is, only upon requst, whereas active agents involve themselves voluntarily. Teams composed of active agents are generally believed to perform better than those with passive agents. In this paper, by using a computational simulation model we examine the effect of agent activeness on the efficiency of decision-making teams that access different amout of information. "Team-Soar" is a computational fraemwork that consists of a group of interconnected individual Al agents (i.e., Soar). A simulation experiment using Tearm-Soar was performed. Results of the simulation provide valuable insights on the roles of agent activeness. For example, the impact of having more active agents becomes more sigfniciant as the amout of information to process increases and when the team decision efficiency is important. Some of the results are counter-intultive and therefore provides an opportunity to understand the roles of the agnet activeness more deeply. For instance, the simulation results reveal that having more active agents did not always enhance team efficiency. Conclusively, the simulation experiment demonstrates how computational models contribute to the research of agents social characteristics.teristics.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.47-54
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• 2020

Integration of active and passive waveguides is an essential component of the photonic integrated circuit and its elements. Butt joint is one of the important technologies to accomplish it with significant advantages. However, it suffers from high optical loss at the butt joint junction and need of accurate process control to align both waveguides. In this study, we used beam propagation method to simulate an integrated device composed of a laser diode and spot size converter (SSC). Two SSCs with different mode properties were combined with laser waveguide and optical coupling efficiency was simulated. The SSC with larger near field mode showed lower coupling efficiency, however its far field pattern was narrower and more symmetric. Tapered passive waveguide was utilized for enhancing the coupling efficiency and tolerance of waveguide offset at the butt joint without degrading the far field pattern. With this technique, high optical coupling efficiency of 89.6% with narrow far field divergence angle of 16°×16° was obtained.

• KIEAE Journal
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• v.15 no.6
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• pp.27-36
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• 2015

Purpose: The definition and factors of passive design being the sustainable method of building plan through the preceding research is deducted and the effect of passive design within the public library by applying the deducted factors in the case of built public libraries and further the realization plan of green library aimed to be reviewed in this research. Method: This study is to induce common elements of architecture plan for public library and passive design, and assess application level of re-classified elements of sustainable public library in order to analyze present condition of passive design applied on facilities of public library. First, related laws and planning standards of public library will be reviewed, then the definition of passive design will be considered using advanced research. Through advanced research related to planing elements and passive design for library induced from various plans for library standards, a common ground of induced passive design element will be transformed into assessment items and practices to be analyzed. Result: Libraries which are and are not preliminarily certified by G-SEED will be compared with each other in order to analyze the effects of passive design on G-SEED. Even though various passive elements such as load reduction of air conditioning and energy efficiency exist, there are no assessment tool within G-SEED. The fact that there are only standards for temporary methods such as utilization of construction material and installation of equipment highlights the challenges in quantitative evaluation.

• Journal of the Korean Institute of Rural Architecture
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• v.20 no.4
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• pp.1-8
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• 2018

In this study, we survey the 2 buildings at the Central 1 and 8 buildings at the Central 2, which are divided by each climate region in the rural regions. Major heat loss factors are 47% loss of the outer shell including outer wall, roof, and bottom, 30% loss through window, and 23% loss through crevice wind. We analyze the energy simulation of ECO2 program to construct a zero energy building regarding village hall located in Jung Juk 4-le at Centeral 2. We simulate the primary energy requirement regarding village hall and the simulated results show the $265.3kWh/m^2{\cdot}a$ and it may estimate '2' energy efficiency grade. The energy requirement regarding village hall is the $183.2kWh/m^2{\cdot}a$ when the passive technology are applied in village hall. We research total amount of energy requirement in village hall when the passive and active technologies such as solar cell with 3kW and solar thermal with $20m^2$, geothermal power with 17.5kW. The simulated results show the improved energy efficiency certification grade with $1^{{+}{+}{+}}$ due to the reduced primary energy requirement with 73% when passive technology including 3kW of solar panel is applied and the energy independence rate is 54%, which is estimated to be 4th grade of zero energy buildings. The order of energy consumption are solar panel, solar thermal, and geothermal power under applied passive technology in the building. In order to expand the zero energy building, it is necessary to introduce the zero energy evaluation system in the rural region.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.417-424
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• 2009

A micro-mixer with a quasi-active rotor was fabricated, and mixing characteristics were evaluated. The proposed micro-mixer combines an active type micro-mixer with a passive type micro-mixer. The micro-rotor, which is a moving part of an active type micro-mixer, is added in a micro-chamber of a passive type vortex micro-mixer. The rotor rotated by inflows tangent to a chamber, causing strong perturbations. The micro-mixers were fabricated using photosensitive glass. Mixing efficiency of the micro-mixers was measured using an image analysis method. Mixing efficiency and characteristics of the micro-rotor mixer were compared with the vortex micro-mixer without a rotor. Mixing efficiency was reduced as Reynolds number increased at a low Reynolds number due to decrease of residence time. Mixing efficiency at higher Reynolds number, on the other hand, was improved even though residence time decreased since the contact surface between fluids increased by twisted flow. The perturbation induced by rotating rotor at greater than Re 200 improved the efficiency of the rotor mixer.

• The Journal of Korea Robotics Society
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• v.9 no.2
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• pp.124-131
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• 2014

The robot mechanisms that were previously researched had only been conducted for the purpose of overcoming the obstacles stably at low speed driving and enhancing the stability against high speed circuitous driving, and yet, the mechanism satisfying two purposes. However, in order to stably drive with high speed on rough terrain, there is a need for satisfying both of these purposes, as well as testing the efficiency of the mechanisms at high speed driving. There, this paper simulated some of the passive mechanisms and focused on checking the performances of passive mechanisms through simulations and analyzing each mechanism on the basis of an evaluation index. The simulation was conducted by Adams (The Multi-body Dynamics Simulation Solution) and used various types of passive mechanisms which were introduced in the robotics field. As a result, the study confirmed that passive mechanisms have a number of situations that affect the driving stability on each direction of roll and pitch. Further study is needed about active mechanism.