• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.562-567
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• 2012

Noises from the large scale marine propeller are calculated numerically on non-cavitation condition. The hydrodynamic analysis are carried out by potential based panel method with time marching free wake approach. The distribution of hyrodynamic loads on the propeller surface and noise signals are obtained using the unsteady Bernoulli's equation and the Farasssat formula respectively. It turns out that the noise signal shows strong peak at the blade passage frequency. Noise signals and directivity patterns for both the thickness and the loading noise are compared with each other. The directivity pattern for the loading noise shows minor lobe at the backward side of the rotating disc plane.

• Culinary science and hospitality research
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• v.10 no.4
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• pp.201-214
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• 2004

The brand image had an effect on customer loyalty degree "Traditional characteristic", "Reliability", "Future events sliced raw fish directivity". With it appears, causing the effect which is powerful in customer loyalty degree "Traditional characteristic or reputation of restaurant", "Reliability of advertisement". The brand image had an effect on customer satisfaction "Reliability", "Customer directivity", "Traditional characteristic". With appears and with it is referred from above together "Traditional characteristic of restaurant" or "Reliability of advertisement public information", "Policy of the restaurant management customer first of all poem".

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1453-1462
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• 1996

A numerical simulation is carried out on the directiveity synthesis of ultrasonic transducers by point source array. Directive method with combined LMS(Least-Mean-Square) method is practiced by means of a iterative method to realize the desired directivity. The directiviey of quasi-ideal beam with a beam width and a directive arbitrary specified was chosen. On the numerical resut, Proposed algorithm shows higher speed of clculating simulation than that of LMS method, and make adaptive control, which enables the desired directivity. Numerical simulations are carried out by PC(CPU:80486 DX2, RAM 16Mbyte).

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.3
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• pp.392-403
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• 2013

For the analysis of radiating noise problems in medium-to-high frequency ranges, the Energy Flow Boundary Element Method (EFBEM) was developed. EFBEM is the analysis technique that applies the Boundary Element Method (BEM) to Energy Flow Analysis (EFA). The fundamental solutions representing spherical wave property for radiating noise problems in open field and considering the free surface effect in underwater are developed. Also the directivity factor is developed to express wave's directivity patterns in medium-to-high frequency ranges. Indirect EFBEM by using fundamental solutions and fictitious source was applied to open field and underwater noise problems successfully. Through numerical applications, the acoustic energy density distributions due to vibration of a simple plate model and a sphere model were compared with those of commercial code, and the comparison showed good agreement in the level and pattern of the energy density distributions.

• Structural Engineering and Mechanics
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• v.56 no.5
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• pp.855-870
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• 2015

In this paper the effects of fling-step and forward-directivity on the seismic performance of steel eccentrically braced frames (EBFs) are addressed. Four EBFs with various numbers of stories (4-, 8-, 12- and 15-story) were designed for an area with high seismic hazard. Fourteen near-fault ground motions including seven with forward-directivity and seven with fling-step effects are selected to carry out nonlinear time history (NTH) analyses of the frames. Furthermore, seven more far-field records were selected for comparison. Findings from the study reveal that the median maximum links rotation of the frames subjected to three set of ground motions are in acceptable range and the links completely satisfy the requirement stated in FEMA 356 for LS performance level. The arrival of the velocity pulse in a near-fault record causes few significant plastic deformations, while many reversed inelastic cycles result in low-cycle fatigue damage in far-fault records. Near-fault records in some cases are more destructive and the results of these records are so dispersed, especially the records having fling-step effects.

• Journal of the Korean Institute of Navigation
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• v.20 no.4
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• pp.129-137
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• 1996

In this paper, we simulated a radiation pattern directivity of microstrip patch antenna for 9[GHz] using the computer. It is analyzed and compared the directivity of field characteristics at two different aspects. One is that of 1-dimension and 2-dimension array, the other is that of a linear and planar array antenna. We tried the constants for the simulation of teflon substrate, dielectric constant ${\varepsilon}r=2.50$, ground plane conductor thickness t=0.03556, substrate height h=0.72188, dielectric loss degree $tan{\delta}$=0.00085, characteristics impedence of line $Zo=50({\Omega})$. The major advantage of microstrip patch antenna is that the arrangement of antenna is associated with the directivity and effectiveness. We have been studied the difference of the radiation pattern of antenna with wave variety through computer simulation.

• Earthquakes and Structures
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• v.17 no.1
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• pp.1-15
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• 2019

In the structures with high level of ductility, the earthquake energy dissipation in structural components is an important factor that describes their seismic behavior. Since the connection details play a major role in the ductile behavior of structure, in this paper, the seismic response of 3-, 5- and 8-story steel special moment frames (SMFs) is investigated by considering the effects of panel zone modeling and the influence of forward-directivity near-field ground motions. To provide a reasonable comparison, selected records of both near and far-field are used in the nonlinear time-history analysis of models. The results of the comparison of the median maximum inter-story drift under excitation by near-field (NF) records and the far-field (FF) ground motions show that the inter-story drift demands can be obtained 3.47, 4.86 and 5.92 times in 3-, 5- and 8-story structures, respectively, undergoing near-field earthquakes.

• International Journal of Contents
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• v.7 no.4
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• pp.44-49
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• 2011

The scattering solutions for multiple rectangular metallic gratings in a perfectly conducting plane excited by the TE and TM delta sources are presented using an overlapping T-block method. A reflectarray composed of rectangular metallic gratings shows fanbeam radiation patterns that are useful for an electromagnetic fence. The scattering characteristics of multiple rectangular gratings were computed in terms of total radiated power and antenna directivity. The design method of a fan-beam reflectarray to obtain high directivity was also compared with superdirective radiation and parabolic reflector phase.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.338-341
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• 2003

In this paper, we designed and implemented a microstrip directional coupler that has high directivity at 2.14 GHz. To design coupler that has high directivity, we used interdigital capacitors instead of lumped elements. The measured results show the diretivity is higher than 30 dB at 2.14 GHz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1002-1006
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• 2000

It is diffuse sound field that measuring condition of absorption ratio and sound transmission loss for material consist of building are measured in reverberartion room and on-site. In this study, for upkeeping diffuse sound field in reverberation room, it is measured and etimated that sound field is effected according to sound source lacation and characteristics of emission directivity for sound source.