• Journal of the Korean Wood Science and Technology
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• v.37 no.2
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• pp.137-140
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• 2009

Chromated copper arsenate (CCA), a long history of successful preservative, have raised environmental concerns. Adsorption characteristics of domestic soils for chromium, copper, and arsenic were assessed by measuring distribution coefficient ($K_d$) values of these metal components in a laboratory scale. The results revealed that $K_d$ values were higher in chromium, followed by arsenic and copper in soil matrix. Different soil matrixes resulted in varying mobilities of CCA components. The values of $K_d$ for all three metals increased with organic matter contents. The results suggest that the mobility of metal components may be very limited to the surface area adjacent to CCA-treated wood due to their fairly large distribution coefficient ($K_d$). However, the metal components would be persistent and accumulated in the soil, resulting in high chemical concentration in service area of treated wood.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.2
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• pp.60-66
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• 1994

The scattering problem by E-polarized plane wave with oblique incidence on a tapered resistive strip grating with infinite resistivity at strip-edges is analyzed by the method of moments in the spectral domain. Then the induced surface current density is expanded in a series of Ultraspherical polynomials of the zeroth order. The expansion coefficients are calculated numerically in the spectral domain, the numerical results of the geometricoptical reflection coefficient for the tapered resistivity in this paper are compared with those for the existing uniform resistivity. And the position of sharp variation points in the magnitude of the geometric-optical reflection coefficient can be moved by varying the incident angle and the strip spacing. It is found out that these sharp variation points are due to the transition of higher modes between the propagation mode and the evanescent mode.

• Journal of Welding and Joining
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• v.20 no.3
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• pp.129-137
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• 2002

This study presents a new method to derive the constraint coefficient from the degree of angular deformation caused by welding, as measured experimentally by varying the shape of welded joints and the magnitude of constraints and from analysis results given by the elastic FEM method. The equivalent load was then calculated with this constraint coefficient. The validity of the numerical analysis involved in this new method was confirmed by its agreement with the experimental results. As for the effects of the constraints based on the shape of the welded joints in the case of Butt welding when the constraint coefficients are not considered, the deformed quantity produced by analysis is larger that produced by experiment and consequently is largely affected by the constraints. However, in the case of Fillet welding, the deformed quantity is seldom affected regardless of constraint coefficient considerations.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.1
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• pp.95-101
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• 2012

An internal type roller ring gear(RRG) system composed of either a pin or a roller ring gear and its conjugated cam pinion can improve the gear endurance from that of a conventional gear system by reducing the sliding contact, while increasing the rolling motion. In this paper, we first proposed the exact cam gear profile and the self-intersection conditions obtained when the profile shift coefficient is introduced. Then, we investigated contact stresses and surface pitting life to fmd characteristics for surface fatigue by varying the shape design parameters. The results show that the pitting life can be extended significantly by increasing the profile shift coefficient.

• 전기의세계
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• v.15 no.5
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• pp.1-5
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• 1966

The stability and safety of operation of a reactor is determined mainly by the sign and magnitude of its reactivity responses to temperature changes. Reactors are subject to temperature fluctuations due to the changes in reactor power and ambient temperature. These temperature fluctuations cause reactivity disturbances through changes in the nuclear and physical properties of the core. Because of these important phenomena by the temperature effects, a large portion of study and testing on a reactor design has been conducted. In this experiment the overall temperature coefficient of the TRIGA MARK-II reactor is measured. The basic procedure is to change the tgemperature of the water moderator, and from the movements of a newly recalibrated control rod(this is necessary due to the effects of fuel burn-up and control rod depression) required to mintain criticality, the reactivity worth of the temperature change is determined. From this measurement, the overall temperature coefficient seems to be smoothly varying, almost a linear function of temperature, and a value of approximately -0.267${\c}$/$^{\circ}C$ can be obtained for an average temperature range from $17.6^{\circ}C$ to $32.5^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.703-707
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• 1989

The ignition of solid particle under strong convective heating has been investigated by applying an asymptotic analysis to a semi-infinite body for varying values of gas recovery temperature and convective heat transfer coefficient. It was found that if the scale of the reaction zone is much smaller than the characteristic length of the body size, then infinite body theory can be used to estimate the ignition delay time. Furthermore, the convective heat transfer coefficient was found to have more influence on predicting the ignition delay times of particle exposed to an incident shock wave rather than the gas recovery temperature.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.2
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• pp.23-34
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• 1995

This paper is concerned with effective and reliable tool breakage detection method using pattern characteristics of feed motor current in milling operations. Correlation coefficient is derived from the feature vector of signal for two consecutive which are extracted feed motor current over three spindle revolutions. The changing pattern of correlation coefficient is continuously compared to detect tool breakage and monitor cutting conditions. This proposed monitoring scheme is not affected by different tools, friction of motion, and varying cutting conditions and material shapes. Experimental results are presented to support the proposed monitoring scheme.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.147-157
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• 2005

In this study, consolidation analysis methods reflecting various ground condition and changing coefficient of consolidation with consolidation process are presented. Research activities include development of numerical program consists of two parts considering vertical drainage only and both drainage condition with vertical and radial direction. Also, interface equation of adjacent two layers and function for changing coefficient of consolidation are added to developed program. This paper presents the results from a detailed consolidation analyses, which explores consolidation process with time in varying layered system and changing coefficient of consolidation

• Structural Engineering and Mechanics
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• v.90 no.3
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• pp.273-285
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• 2024

Tapered girders emerged as an economical remedy for the challenges associated with constructing long-span buildings. From an economic standpoint, these systems offer significant advantages, such as wide spans, quick assembly, and convenient access to utilities between the beam's shallow sections and the ceiling below. Elastic-local buckling is among the various failure modes that structural designers must account for during the design process. Despite decades of study, there remains a demand for efficient and comprehensive procedures to streamline product design. One of the most pressing requirements is a better understanding of the tapered web plate girder's local buckling behavior. This paper conducts a comprehensive numerical analysis to estimate the critical buckling coefficient for simply supported tapered steel web plates, considering loading conditions involving compression and bending stresses. An eigenvalue analysis was carried out to determine the natural frequencies and corresponding mode shapes of tapered web plates with varying geometric parameters. Additionally, the study highlights the relative significance of various parameters affecting the local buckling phenomenon, including the tapering ratio of the panel, normalized plate length, and ratio of minimum to maximum compressive stresses. The regression analysis and optimization techniques were performed using MATLAB software for the results of the finite element models to propose a separate formula for each load case and a unified formula covering different compression and bending cases of the elastic local buckling coefficient. The results indicate that the proposed formulas are applicable for estimating the critical buckling coefficient for simply supported tapered steel web plates.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.2
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• pp.136-144
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• 1999

The study on the wear characteristics of compound layers formed during gaseous nitrocarburising in the medium carbon boron steels and the plain carbon steel has been carried out by using a pin-on-disc type wear test machine under the oil lubricating condition at room temperature and by varying applied loads, sliding speeds and wear distances. Values of friction coefficient measured at the sliding speed of 0.4m/sec under the oil lubricating condition have been shown to decrease considerably with increasing applied load and become gradually a constant value as load is increased to a higher value, showing that the transition load for friction coefficient appears at an applied load of 247.2N. The length and volume wear rates of compound layer have been revealed to relatively constantly increase, also showing that the wear life per unit thickness of compound layer turns out to be superior as porous layer has a denser and thinner appearance. As the sliding speed increases during wear test performed by varying sliding speed at a load of 63.2N under the oil lubricating condition for medium carbon boron steel nitrocarburised in gas atmosphere, the wear rate has been found to increase, the friction coefficient to decrease and the wear life per unit thickness of compound layer to decrease considerably.