• Journal of the Korean Society for Aviation and Aeronautics
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• v.25 no.3
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• pp.115-122
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• 2017

To achieve designed quality and reliability from R&D to force integration, an establishment of precise and distinct specifications and standards are required. However, the recent process of R&D standardization on defense acquisition system, has brought plenty of corrections on specifications and standards that may cause not only difficulties to production line and retardation to the military forces, but also a degradation of provided weapon systems. Therefore, a technical review should be performed by the developer, the producer, and the client, establishing the standard that include mass production requirements as well as clients' requirements. This paper propose a specified solution on process of R&D standardization, by applying a substantial FCA(Functional Configuration Audit) and PCA(Physical Configuration Audit) which implies participation of related agencies. By the improved PCA, 2,023 corrections on 74 types of QAR(Quality Assurance Requirement)s and 12,715 corrections on drawings are identified.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.9
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• pp.799-806
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• 2007

Direct Numerical Simulation was carried out to predict mass transfer in turbulent flow around a rotating stepped cylinder. This investigation is a follow-up study of DNS of turbulent flow in Nesic et al. [Corrosion, Vol. 56, No. 10, pp. 1005 - 1014] The original motivation of this work stemmed from the efforts to design a simple device which can generate flows of high turbulence intensity at low cost for corrosion researchers. Two cases were considered; Sc=1 and 10 both at Re=335. Here, Sc and Re stand for Schmidt number and Reynolds number, respectively, based on the step height and the surface speed of the cylinder upstream of the step. Main focus was placed on the correlation between turbulence and mass transfer. The spatio-temporal evolution of concentration field is discussed. The numerical results are qualitatively compared with those of the experiment conducted with a similar flow configuration.

• Smart Structures and Systems
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• v.10 no.2
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• pp.155-179
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• 2012

This paper aims at assessing the seismic performance of Tuned Mass Dampers (TMDs) based on sets of recorded ground motions. For the simplest configuration of a structure-TMD assembly, in a comprehensive study characteristic response quantities are derived and statistically evaluated. Optimal tuning of TMD parameters is discussed and evaluated. The response reduction by application of a TMD is quantified depending on the structural period, inherent damping of the stand-alone structure, and ratio of TMD mass to structural mass. The effect of detuning on the stroke of the TMD and on the structural response is assessed and quantified. It is verified that a TMD damping coefficient larger than the optimal one reduces the peak deflection of the TMD spring significantly, whereas the response reduction of the main structure remains almost unaffected. Analytical relations for quantifying the effect of a TMD are derived and subsequently evaluated. These relations allow the engineer in practice a fast and yet accurate assessment of the TMD performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.4
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• pp.237-243
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• 2016

It is necessary to investigate the input power as well as the mass transfer characteristics of the aeration process in order to improve the energy efficiency of an aerobic water treatment. The objective of this study is to experimentally investigate the effect of orifice nozzle design and input power on the flow and mass transfer characteristics of a vertical two-phase flow. The mass ratio, input power, volumetric mass transfer coefficient, and mass transfer efficiency were calculated using the measured data. It was found that as the input power increases the volumetric mass transfer coefficient increases, while the mass ratio and mass transfer efficiency decrease. The mass ratio, volumetric mass transfer coefficient, and mass transfer efficiency were higher for the orifice configuration with a smaller orifice nozzle area ratio. An empirical correlation was proposed to estimate the effect of mass ratio, input power, and Froude number on the volumetric mass transfer coefficient.

• Herbal Formula Science
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• v.21 no.2
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• pp.121-132
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• 2013

Objectives : The objectives of this study is to establish data-base to find out similar herbal formulas with a particular herbal formula by comparing composition ratio of configuring herbs. And this thesis is to analyze differences of prescriptions and find out similar prescriptions by utilizing galenical mass ratio, which is directly related to effectiveness of galenical. Methods : This study was proceeded by using Access 2007 with Window 7(MS) and 2,787 prescriptions of which herbal configuration could be indicated by weight unit were analysed from Donguibogam. We standardize all units of the prescription and input the mass ratio data when entered galenical data. Results : We could confirm a degree of similarity between compared prescriptions and a particular prescription according to the sum of differences of herb weight ratio and similarity ratio. Conclusions : A most similar herbal formula could be searched through comparing multi prescriptions by multi prescriptions of herbal configuration from established herbal formula data-base where herb weight ratio of prescriptions is to be input.

• Structural Engineering and Mechanics
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• v.61 no.2
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• pp.193-207
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• 2017

In this study, the vibration of an electrostatically actuated micro cantilever beam is analyzed in which a viscoelastic layer covers a portion of the micro beam length. This proposed model is considered as the main element of mass and pollutant micro sensors. The nonlinear motion equation is extracted by means of Hamilton principle, considering nonlinear shortening effect for Euler-Bernoulli beam. The non-linear effects of electrostatic excitation, geometry and inertia have been taken into account. The viscoelastic model is assumed as Kelvin-Voigt model. The motion equation is discretized by Galerkin approach. The linear free vibration mode shapes of non-uniform micro beam i.e. the linear mode shape of the system by considering the geometric and inertia effects of viscoelastic layer, have been employed as comparison function in the process of the motion equation discretization. The discretized equation of motion is solved by the use of multiple scale method of perturbation theory and the results are compared with the results of numerical Runge-Kutta approach. The frequency response variations for different lengths and thicknesses of the viscoelastic layer have been founded. The results indicate that if a constant volume of viscoelastic layer is to be deposited on the micro beam for mass or gas sensor applications, then a modified configuration may be found by using the analysis of this paper.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.1
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• pp.73-85
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• 2003

Four different methods of reducing the heat transfer coefficients from experimental data under dehumidifying conditions are compared. The four methods consist of two different heat and mass transfer models and two different fin efficiency models. Data are obtained from two heat exchanger samples having plain fins or wave fins. Comparison of the data with the reduction methods revealed that the single potential heat and mass transfer model yielded the humidity independent heat transfer coefficients. Two different fin efficiency models - enthalpy model and humidity model - yielded approximately the same fin efficiencies and accordingly approximately the same heat transfer coefficients. The heat transfer coefficients under wet conditions were approximately the same as those of the dry conditions for the plain fin configuration. For the wave fin configuration, however, wet surface heat transfer coefficients were approximately 12% higher. The pressure drops of the wet surface were 10% to 45% larger than those of the dry surface.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1123-1128
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• 2009

The refrigerant R-134a flow distributions are experimentally studied for a round header/ten flat tube test section simulating a brazed aluminum heat exchanger. Three different inlet orientations (parallel, normal, vertical) were investigated. Tests were conducted with downward flow for the mass flux from 70 to $130\;kg/m^2s$ and quality from 0.2 to 0.6. In the test section, tubes were flush-mounted with no protrusion into the header. It is shown that normal and vertical inlet yielded approximately similar flow distribution. At high mass fluxes or high qualities, however, slightly better results were obtained for normal inlet configuration. The flow distribution was worst for the parallel inlet configuration. Possible explanation is provided based on flow visualization results.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.329-334
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• 2001

In order to investigate the operating characteristics of a supersonic steam ejector, the axisymmetric, compressible, Reynolds-averaged, Navier-Stokes computations are performed using a finite volume method. The secondary and back pressures of the ejector system with a second throat are changed to investigate their effects on the suction mass flow. Three operation modes of the steam ejector system, the critical mode, subcritical mode and back flow mode, are discussed to predict the critical suction mass flow. The present computations are validated with some experimental results. The secondary and back pressures of the supersonic steam ejector significantly affect the critical suction mass flow. The present computations predict the experimented critical mass flow with fairly good accuracy. A good correlation is obtained for the critical suction mass flow. The present results show that provided the primary nozzle configuration and secondary pressure are known, we can predict the critical mass flow with good accuracy.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2211-2218
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• 2003

The present study investigates heat/mass transfer characteristics in a rotating two-pass duct for smooth and ribbed surfaces. The duct has an aspect ratio of 0.5 and a hydraulic diameter of 26.67 mm. 70-angled rib turbulators are attached on the leading and trailing sides of the duct in parallel and cross arrangements. The pitch-to-rib height ratio is 7.5 and the rib height-to-hydraulic diameter ratio is 0.075. The Reynolds number based on the hydraulic diameter is constant at 10,000 and the rotation number ranges from 0.0 to 0.2 Detailed local heat/mass transfer coefficients are measured using a naphthalene sublimation technique. The results show that the secondary flows generated by the $180^{\circ}-turn$, rib turbulators, and duct rotation affect the wall heat/mass transfer distribution significantly, As the duct rotates, the rotaion-induced Coriolis force deflects the main flow and results in differences on the heat/mass transfer distribution between the leading and trailing surfaces. Its effects become more dominant as the rotaion number increases. Discussions are presented describing how the rib configuration and the rotaion speed affect the flow patterns and local heat/mass transfer in the duct.