• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.7
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• pp.537-548
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• 2014

In this paper, horn loudspeaker modeling was suggested, investigated and verified through comparison of test results and simulation ones based on input electrical impedance curves and acoustic sensitivity ones. First, Thiele Small parameters of horn driver were identified by using pseudo loudspeaker model concept and verified in case of both closed and open horndriver. Second, cone-shaped horn models were investigated and compared with input acoustic impedance curves for real horn(cone angle $6.6^{\circ}$) and short horn(cone angle $27.9^{\circ}$). It showed that Leach model for cone horn was well described to test results, which were electrical impedance and acoustic sensitivity, compared to Lemaitre one. To represent horn system model good approximation in wide frequency range, mass correction filter and lowpass filter were adopted and consequently showed good fitted to test results.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.54.1-54.1
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• 2018

For space weather forecast, it is important to determine three-dimensional parameters of coronal mass ejections (CMEs). To estimate three-dimensional parameters of CMEs, we have developed a full ice-cream cone model which is a combination of a symmetrical flat cone and a hemisphere. By applying this model to 12 SOHO/LASCO halo CMEs, we find that three-dimensional parameters from our method are similar to those from other stereoscopic methods. For several geoeffective CME events, we determine CME mass by applying the Solarsoft procedure (e.g., cme_mass.pro) to SOHO/LASCO C3 images. CME volumes are estimated from the full ice-cream cone structure. We derive CME mean density as a function of CME height for these CMEs, which are approximately fitted to power-law functions. We find that the ICME mean densities extrapolated from the power law functions, are correlated with their corresponding ICME ones in logarithmic scales.

• 한국전산유체공학회:학술대회논문집
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• 1997.10a
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• pp.143-148
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• 1997

Differential pressure Venturi cone flowmeter is an advanced flowmeter which has many advantages such as wide range of measurement, high accuracy, excellent flow turndown ratio, low headless, and short installation pipe length requirement, etc. Like other differential pressure flowmeter, Venturi cone flowmeter uses the law of energy conservation, but its shape and position make it perform better than others. The cone acts as its own flow conditioner and mixer, fully conditioning and mixing the flow prior to measurement. For the analysis, we use Reynolds-averaged Navier-Stokes equations and $k-{\omega}$ turbulence model. The equations are fully trans-formed in the computational coordinates, the pressure-velocity coupling is made through SIMPLER algorithm, and the equations are discretized using analytic solutions of the linearized equations(Finite Analytic Method). At the end of the paper, using the result of analysis, We propose a new shape of cone with the hope of drag reduction and high performance.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.1
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• pp.10-16
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• 2010

Mail centers are essential postal facilities that sort and dispatch postal items, and should be operated efficiently to provide customers high quality postal services. So the efficiency analysis of mail centers should be performed in order to induce better operation. But current performance evaluation system has 95 percent of predetermined and weighted non-quantitative indices. There is need to introduce objective efficiency measurement methodology. The main objectives of this study was to analyze the efficiency of 24 mail centers empirically using cone-ratio DEA and suggest the appropriate cone-ratio method. Consequently, this paper suggests that the cone-ratio DEA model integrating decision-maker's preferences is more desirable for efficiency analysis than that of using transformed data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2234-2241
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• 2015

This study has been undertaken to develop a relationship between the shear strength coefficients and the cone index. The theoretic mathematical equations for the relationship were rigorously investigated, and then a Artificial Neural Network(ANN) analysis was adapted to enhance the reliability of the investigation. The theoretical investigation involved various assumptions resulting in the significant error involvement of geotechnical behaviors of ground. Therefore, a model using the ANN has been learned to enhance the prediction of the cone index form the shear strength parameters. Site investigation reports from various construction fields were used for ANN model learning. The results of the study show that the model predicts the cone index from the shear strength parameters of soils very well. The further study that is undertaking has a potential promise of the generalized prediction technique for the cone index from the soil parameters.

• Journal of the Korean Geotechnical Society
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• v.35 no.2
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• pp.37-51
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• 2019

This study focuses on the numerical simulations of the cone penetration tests in a sand ground. The mechanical responses of sand were described using the modified Mohr Coulomb plasticity model based on the critical state soil mechanics. In the plasticity model, the dilatancy angle was not a constant, but a function of the distance to the critical state line from the current state of void ratio and mean effective stress. To simulate cone penetration tests numerically, this study relied on Lagrangian finite element method under the axisymmetric condition. To enable penetration of the cone penetrometer without tearing elements along the symmetric axis, the penetration guide concept was adopted in this study. The results of numerical simulations on the calibration chamber cone penetration tests had good agreement with the experimental results.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.2
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• pp.177-184
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• 2013

This study analyzed the hydraulic characteristics of a venturi flume with a circular cone using a 3-D numerical model which uses RANS(Reynolds-Averaged Navier-Stokes Equation) as the governing equation. The venturi flume with the circular cone efficiently measures the discharge in the low-flow to high-flow range and offers the advantage of accurate discharge measurements in the case of a low flow. With no influence of the tail-water depth, the stage-discharge relationship and the flow behaviors were analyzed to verify the numerical simulation results. Additionally, this study reviewed the effect of the tail-water depth on the flow. The stage-discharge relationship resulting from a numerical simulation in the absence of an effect by the tail-water depth showed a maximum margin of error of 4 % in comparison to the result of a hydraulic experiment. The simulation results reproduced the overall flow behaviors observed in the hydraulic experiment well. The flow starts to become influenced by the tail-water depth when the ratio of the tail-water depth to the total head exceeds approximately 0.7. As the ratio increases, the effect on the flow tends to grow dramatically. As shown in this study, a numerical simulation is effective for identifying the stage-discharge relationship of a venturi flume with various types of venturi bodies, including a venturi flume with a circular cone.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.58-59
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• 2006

In Spray Forming, specific enthalpy is a key parameter in the deposition process as it influences the thermal condition of the impinging droplets as well as that of the deposit surface. An empirical model for the distribution of specific enthalpy in the spray cone was developed as an easy to handle alternative to numerical models with which the descriptive partial differential equations are solved numerically. The model results were compared with the experimental data to validate its applicability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.568-574
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• 1998

A systematic procedure for designing a direct-radiator-type loudspeaker has been developed, based on a numerical vibro-acoustic analysis and the Taguchi method. The finite-element model of the speaker cone has been used to calculate the vibration response of the cone excited by the voice coil. The vibration response of the speaker cone has been used as a boundary condition for the acoustic analysis, and the acoustic frequency characteristics of the loudspeaker have been calculated by the boundary element method. The numerical model has been confirmed by comparing the numerical results with experimental ones obtained in an anechoic chamber. Some design parameters contributing dominantly to the acoustic characteristics have been selected by using the Taguchi method, and the variations of the acoustic characteristics due to the changes of the parameter values have been examined using the numerical model.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.28.2-28.2
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• 2011

Coronal Mass Ejections (CMEs) are enormous eruptions of plasma ejected from the Sun into interplanetary space, and mainly responsible for geomagnetic storms and solar energetic particle events. It is very important to infer their direction of propagation, speed and their 3-dimensional configurations in terms of space weather forecast. Two STEREO satellites provide us with 3-dimensional stereoscopic measurements. Using the STEREO observations, we can determine the 3-dimensional structure and radial velocity of the CME. In this study, we applied three different methods to the 2008 April 26 event: (1) Ice cream Cone Model by Xue (2005) using the SOHO/LASCO data, (2) Flux rope model by Thernisien (2009) using the STEREO/SECCHI data, (3) Flux rope model with zero angle using the STEREO/SECCHI data. The last method in which separation angle of flux rope is zero, is similar to the ice cream cone model morphologically. The comparison shows that the radial speeds from three methods are estimated to be about 750km/s and are within ${\pm}120km/s$. We will extend this comparison to other CMEs observed by STEREO and SOHO/LASCO.