• Steel and Composite Structures
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• v.1 no.2
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• pp.187-200
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• 2001

Most of the portal frames are designed these days by the application of plastic analysis, with the normal assumption being made that the column bases are pinned. However, the couple produced by the compression action of the inner column flange and the tension in the holding down bolts will inevitably generate some moment resistance and rotational stiffness. Full-scale portal frame tests conducted during a previous research program had suggested that this moment can be as much as 20% of the moment of resistance of the column. The size of this moment of resistance is particularly important for the design of the tensile capacity of the holding down bolts and also the bearing resistance of the foundation. The present research program is aiming at defining this moment of resistance in simple design terms so that it could be included in the design of the frame. The investigation also included the study of the semi-rigid behaviour of the column base/foundation, which, to a certain extent, affects the overall loading capacity and stiffness of the portal frames. A series of column bases with various details were tested and were used to calibrate a finite element model which is able to simulate the action of the holding down bolts, the effect of the concrete foundation and the deformation of the base plate.

• KSBB Journal
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• v.15 no.5
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• pp.444-451
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• 2000

Nonliving methanotrophic biomass was used as biosorbent to remove lead which is one of representative pollutants in metal-bearing wastewater. Solution pH, maximum uptake, biosorbent dose and ionic strength were considered as major factors for adsorption experiments. The optimum pH range for lead removal was increased 3.8∼11.0 for methanotrophic biomass compared to biosorbent-free control, pH of 8.4∼11.2. Removal efficiency of lead by methanotrophic biomass was pH dependent, but less sensitive than that of control. In isotherm experiments with 0.2g biosorbent/L at initial solution pH 5.0, methanotrophic biomass took up lead from aqueous solutions to the extent of 1085 mg/g biomass. Removal amount of lead increased with an increase of biomass dose. According to biomass dose for initial 1000 mg Pb/L at initial pH 5.0, the optimum amount of biomass for maximum lead removal per unit methanotrophic biomass was 0.2 g biomass/L. As a result of scanning electron microscope (SEM) micrographs equipped with energy dispersive spectroscopy (EDS), lead removal by methanotrophic biomass seemed to be through adsorptions on the surface of methanotrophic biomass and exopolymers around the biomass. EDS spectra confirmed that lead adsorption appeared on the biomass and exopolymers that may be effective to lead removal comparing before and after contact with lead. Removal efficiency of lead was slightly affected by ionic strength up to 2.0 M of NaCl and NaNO$_3$respectively.

• Journal of the Korean earth science society
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• v.29 no.7
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• pp.640-644
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• 2008

A type and origin of Buyeo and Jecheon mine as the domestic leading feldspar mines are classified by using the petrological characteristics. Jecheon mine is a weathered residual mine formed by the weathering of K-feldspar megacryst bearing porphyritic granite of which forming P-T is 840-5 Kb with the igneous origin of megacryst. On the other hand, Buyeo mine is made by the metasomatic alteration of hydrothermal solution from the biotite granite intrusion. Pure albite as a main ore mineral and garnet and sericite as accessaries are observed in this mine. In addition, the mine is typically characterized by the well recrystallized mineral texture.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.5
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• pp.390-395
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• 2000

The ultrasonic motor have recently begun to be used for certain unique practical utilizations in the fields of industrial medical consumer and automotive applications. Ultrasonic motor stimulated to ultrasonic oscillations by piezoelectrics to drive a rotor via friction contact. The metal and ceramic composite component was used as the stator element to generate ultrasonic vibrations. The ultrasonic motor used here was the windmill type ultrasonic motor operated by single-phase AC source. The windmill type ultrasonic motors has only three components; a stator element of two windmill shape slotted metal endcaps a rotor and a bearing. In this paper a prototype motor with 11.35 mm diameter was fabricated then relationship between the pressing force applied to a rotor and the rotation characteristic of windmill type ultrasonic motor are investigated when stator’s slots was changed from 4, 6, 8 and thickness changed from 0.15, 0.20 mm, respectively. Optimum pressing force applied to a rotor in the six stators was 1.2 mN.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.160-169
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• 1999

Linear pulse rootor (LPM) be suitable a field where smooth linear rootion of high precision is required, because it's structured with minute teeth pitch in airgap of between and stator and roover(forcer). Force and position of LPM are effected sensitively by the teeth pitch, air gap, permanent magnet and excitation current. So, LPM is much important to analyze the force characteristics. llis paper was awlied to perrreance roothed for force calculation at airgap. The airgap of LPM is maintained from the pressure generated by an air-bearing. Simplified airflow and permeance methods will be used to calculate the air gap under static conditions. Therefore, the maximum available force is then derived using the coenergy method with variable air gap, also normal force and linear thrust was acquired from variable minute displacement 1[mm]. 1[mm].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05b
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• pp.173-176
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• 2004

The piezoelectric ceramics for AE sensor piezoelectric devices are desirable to possess higher resonance vibrations. The compositions of $0.9Pb(Zr_xTi_{1-x})O_3-0.1Pb(Mn_{1/3}Nb_{1/3}Sb_{1/3})O_3$ (PZT-PMNS) in this work are selected for obtaining especially large electromechanical coupling factor, high mechanical quality factor and high Curie temperature. This ceramic has higher piezoelectric activity and higher electromechanical coupling factor, but the ceramic has lower Curie temperature. The piezoelectric and dielectric characteristics of PZT-PMNS ternary system are investigated as functions of $Ti^{2+}$, $Zi^{2+}$ mol rate. As the results, MPB(morphotropic phase boundary) in this piezoelectric ceramic is x=0.522. Resonance vibrations of PZT ceramics are investigated as ball-bearing drop test. For the use of AE sensor that driving with pre-amplifier, filter circuit after packed this ceramic and an elastic body.

• 대한공업교육학회지
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• v.31 no.2
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• pp.350-363
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• 2006

Recently, the micro end-milling processing is demanded the high-precise technique with good surface roughness and rapid time in milli-structure parts, micro machine parts and molding industry. The cutting conditions of micro end-milling has an effect on surface roughness of cutting surface. Therefore this study was carried out to cut stainless steel using high revolution air bearing spindle and micro end-mill and analyze the cutting condition to get the optimum surface roughness by design of experiment. From this study, surface roughness have an much effect according to priority on depth of cut, revolution of spindle and feed.

• Journal of the Korean Society of Safety
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• v.20 no.3 s.71
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• pp.152-157
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• 2005

This experimental study was devoted to investigate skin friction of H group piles with uplift loading conditions in granite soil under laboratory test. Model piles made of steel embedded in weathered granite soil were used in this study. Pile arrangements($2{\times}2,\;3{\times}3$), pile space(2D, 4D, 6D), and soil density($D_r=40%,\;80%$) were tested. The main results obtained from the model tests can be summarized as follows. The series of tests found that ultimate uplift load and displacement for group piles were increased as piles space ratio increases to $D_r=40%$ of soil density. In the relative density of $D_r=80%$, bearing capacity for group piles was greater than for single pile. In the relative density of $D_r=40%$, the theoretical value of skin friction for group piles was greater than practical value. In the relative density of $D_r=80%$, both theoretical and practical value of skin friction for group piles were increased as piles space ratio increases.

• The Korean Journal of Mycology
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• v.38 no.2
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• pp.197-198
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• 2010

The morphological and ecological characteristics of Russula eburneoareolata Hongo is reported first time in Korea. The fungus was collected from the mixed forest of Fagaceae in the Gyeryongsan Mountain National Park. The pileus is champagne to ivory, convex then expanded and depressed in the center afterward, and 4 to 9 cm broad. Stipe is 3 to 6 cm long, 12 to 20mm thick and tapering below. Spores are $7-8{\times}6-7\;{\mu}m$, subspherical oval and warty with some connecting lines. Basidia are about $35-40{\times}10-11\;{\mu}m$ and four-spore bearing type.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.34-39
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• 2014

In this study, the structural analysis and the modal analysis are conducted to investigate the stress level, the deformation characteristics and the natural modes of the casing of a planetary gear reducer for a 800kW grade pulverizer mill. The casing is subjected to the load, 2800 kN, from the lump coals in the pulverizing process. Because of the symmetry, the half portion of the reducer casing is modeled for the stress analysis. But the full model is used to find out the eigenvalues and natural modes for the modal analysis. The contact conditions are applied between the thrust pad bearing and the adjacent contacting parts. The results shows that the casing structure has the sufficient strength and stiffness to support the load under consideration. ANSYS version 15 is employed to perform the numerical study.