• Journal of Radiation Protection and Research
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• v.8 no.1
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• pp.26-32
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• 1983

A somewhat detailed energy spectra in terms of the track length resulting from coupled electron-photon slowing down are calculated throughout the ICRU standard tissue with uniformly distributed gamma sources of $^{60}Co\;and\;^{137}Cs$, respectively. The calculation was accomplished by utilizing the latest available cross-section data as input to a carefully optimized computer code. In this report, the calculational method is described in detail. Furthermore, results of calculations are given in graphical form. The results show that the energy spectrum defined in terms of differential track length has about same shape although the energies of gamma source are different. The discontinuity in the energy spectrum appears at the energy of $T=(1/T_0+2/m_0c^2)^{-1}$, because a primary photon can not be degrade to a point below this energy.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.591-599
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• 1994

A design system for power transmission bevel gears(straight, zerol, and spiral) is developed, in which the strength and durability of bevel gears can be estimated and the size of bevel gears can be minimized by introducing optimal techniques. The size of bevel gear pair as the object function to be minimized is the volume of equivalent spur gear pair at mean normal section, and the design variables to be determined are considered as the number of teeth, face width, diametral pitch, and spiral angle in spiral bevel gear. The strength(bending strength, pitting resistance) according to the AGMA standards, geometrical quantities, and operating characteristics(interference of pinion, contact ratio, etc.) are considered as the constraints in design optimization. The optimization with these constraints becomes nonlinear problem and that is solved with ALM(Augmented Lagrange Multiplier) method. The developed design method is applied to the example designs of straight, zerol, and spiral bevel gears. The design results are acceptable from the viewpoint of strength and durability within the design ranges of all other constraint, and the bevel gears are designed toward minimizing the size of gear pair. This design method is easily applicable to the design of bevel gears used as power transmitting devices in machineries, and is expected to be used for weight minimization of bevel gear unit.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.261-268
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• 1998

Deflections due to shrinkage are frequently ignored in design calculation. Especially for thin member, shrinkage often causes considerable deformations as wellas appreciable stress changes. Several methods for computing shringkage curvature have been proposed by many researchers. Some of the approximte methods widely used in the recent years are the equivalent tensile force method, Miller's method and Branson's method. These methods were, however, somewhat oversimplified and could be too conservative in the case of well cured concrete structure. In this paper, an approximate method for computing shrinkage curvature and deflection is proposed. Curvature due to shrinkage is derived from the requirements of strain compatibility and equilibrium of a section and the age-adjusted effective modulus method. The proposed method is verified by comparison with several experimental measurements. The correlations between calculated and measured curvatures is very good.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.603-607
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• 2011

Structure of flashback and reignition occurring near flameholder was experimentally investigated in a model combustor with V-gutter flameholder. The combustor has a long duct shape with cross section of $40{\times}40mm$ and City Nature Gas(CNG) were used as fuel. Measurements of chemiluminescence with high speed camera was used for visualization of flame structure. In the lean case, flashback distance depend on equivalent ratio. New flame occurred at the front tip of flameholder when flashback. Flashback flame moved toward downstream direction of combustor because mixture flow velocity had increased, and then re-ignition was caused by entering flow into recirculation zone that is formed behind the flameholder.

• Smart Structures and Systems
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• v.4 no.1
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• pp.1-17
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• 2008

This study proposes a conceptual framework of in-situ vibration tests and analyses for quality appraisal of non-slender, cast-in-place piles with irregular cross-section configuration. It evaluates a frequency index from vibration recordings to a series of impulse loadings that is related to total soil-resistance forces around a pile, so as to assess if the pile achieves the design requirement in terms of bearing capacity. In particular, in-situ pile-vibration tests in sequential are carried out, in which dropping a weight from different heights generates series impulse loadings with low-to-high amplitudes. The high-amplitude impulse is designed in way that the load will generate equivalent static load that is equal to or larger than the designed bearing capacity of the pile. This study then uses empirical mode decomposition and Hilbert spectral analysis for processing the nonstationary, short-period recordings, so as to single out with accuracy the frequency index. Comparison of the frequency indices identified from the recordings to the series loadings with the design-based one would tell if the total soil resistance force remains linear or nonlinear and subsequently for the quality appraisal of the pile. As an example, this study investigates six data sets collected from the in-situ tests of two piles in Taipu water pump project, Jiangshu Province of China. It concludes that the two piles have the actual axial load capacity higher than the designed bearing capacity. The true bearing capacity of the piles under investigation can be estimated with accuracy if the amplitude of impact loadings is further increased and the analyses are calibrated with the static testing results.

• The Journal of the Acoustical Society of Korea
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• v.23 no.2
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• pp.90-102
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• 2004

According to the Mutual Recognition Arrangement (MRA), the calibration and/or test laboratories should satisfy the management and technical requirements ISO 17025 or equivalent. Chapter 5, Section 5.10.4 of the technical requirement of ISO 17025 suggests the required informations for calibration certificates, one of them is to state the uncertainty of measurement. The uncertainties of measurement in reciprocity calibration of standard laboratory microphone were calculated. The expanded uncertainties for 1 and 1/2 inch microphones were 0.03 dB in the middle frequency range and they increased up to 0.10 dB and 0.11 dB at 20 Hz, 0.07 dB and 0.08 dB at high frequency, respectively.

• International Journal of Highway Engineering
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• v.16 no.3
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• pp.119-129
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• 2014

PURPOSES : This investigational survey is to observe a proper spatial aggregation method for path travel time estimation using the hi-pass DSRC system. METHODS : The links which connect the nodes of section detectors location are used for path travel time estimation traditionally. It makes some problem such as increasing accumulation errors and processing times. In this background, the new links composition methods for spatial aggregation are considered by using some types of nodes as IC, JC, RSE combination. Path travel times estimated by new aggregation methods are compared with PBM travel times by MAE, MAPE and statistical hypothesis tests. RESULTS : The results of minimum sample size and missing rate for 5 minutes aggregation interval are satisfied except for JC link path travel time in Seoul TG~Kuemho JC. Thus, it was additionally observed for minimum sample size satisfaction. In 15, 30 minutes and 1 hour aggregation intervals, all conditions are satisfied by the minimum sample size criteria. For accuracy test and statistical hypothesis test, it has been proved that RSE, Conzone, IC, JC links have equivalent errors and statistical characteristics. CONCLUSIONS : There are some errors between the PBM and the LBM methods that come from dropping vehicles by rest areas. Consequently, this survey result means each of links compositions are available for the estimation of path travel time when PBM vehicles are missed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.56-63
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• 2020

The heat transfer phenomenon in the vicinity of the irradiated region of a focused laser beam of a DMT process greatly affects both the deposition characteristics of powders on a substrate and the properties of the deposited region. The goal of this paper is to investigate the heat transfer characteristics of a single bead deposition of Inconel 718 powders on S45C structural steel using a laser-aided direct metal tooling (DMT) process. The finite element analysis (FEA) model with a Gaussian volumetric heat flux is developed to simulate a three-dimensional transient heat transfer phenomenon. The cross-section of the bead for the FEA is estimated with an equivalent area method using experimental results. Through the comparison of the results of the experiments and those of the analysis, the effective beam radius of the bottom region of the volumetric heat flux and the efficiency of the heat flux model for different powers and travel speeds of the laser are predicted. From the results of the FEA, the influence of the power and the travel speed of the laser on the creation of a steady-state heat transfer region and the formation of the heat-affected zone (HAZ) in the substrate are investigated.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.341-346
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• 2001

The gun-type gas burner adopted in this study is generally composed of some slits and swirl vanes. Therefore, this paper is studied to investigate the effect of slits and swirl vanes on the turbulent flow fields in the horizontal plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rate $450\;{\ell}/min$, which is equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of subsonic wind tunnel. When the burner has only swirl vanes, the axial mean velocity component shows the characteristic that spreads more remarkably toward radial direction than axial one, but when it has only slits, that is developed spreading more toward axial direction than radial one. Therefore, because the biggest speed is spurted in slits and it derive main flow toward axial direction encircling rotational flow that comes out from swirl vane that is situated on the inside of slits, both slits and swirl vanes composing of cone type gas burner act role that decreases the speed near slits and increases the flow speed in the central part of a burner. Moreover, because rotational flow by swirl vanes and fast jet flow by slits increase turbulent intensities effectively coexisting, the turbulent kinetic energy is distributed with a bigger size fairly near slits than burner models which have only slit or swirl vanes within X/R<0.6410.

• Journal of Power System Engineering
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• v.5 no.2
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• pp.22-29
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• 2001

This paper represents axial mean velocity, turbulent kinetic energy and swirl number based on momentum flux measured in the X-Y plane and Y-Z plane respectively of a cone type gas swirl burner by using X-probe from the hot-wire anemometer system. This experiment is carried out at flow rates 350 and $450{\ell}/min$ respectively, which are equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of a subsonic wind tunnel. Axial mean velocities and turbulent kinetic energies show that their maximum values exist centering around narrow slits situated radially on the edge of and in the forefront of a burner until $X/R{\fallingdotseq}1.5$, but they have a peculiar shape like a starfish diffusing and developing into inward and outward of a burner by means of the mixing between flows ejected from narrow slits, an inclination baffle plate and swirl vanes respectively according to downstream regions. Moreover, they show a relatively large value in the inner region of 0.5$S_m$ obtained by integration of velocity profiles shows a characteristic that has an inflection point composing of the maximum and minimum value until X/R<3, but shows close agreement with the geometric swirl number after a distance of X/R=3.