• Bulletin of the Korean Mathematical Society
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• 제52권4호
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• pp.1113-1122
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• 2015

This paper is concerned with the pattern formation of a diffusive predator-prey model with two time delays. Based upon an analysis of Hopf bifurcation, we demonstrate that time delays can induce spatial patterns under some conditions. Moreover, by use of a series of numerical simulations, we show that the type of spatial patterns is the spiral wave. Finally, we demonstrate that the spiral wave is asymptotically stable.

• Journal of the Korean Society for Nondestructive Testing
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• 제28권6호
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• pp.496-503
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• 2008

We propose rectangular type spiral coils with folded comers for the applications to low frequency guided wave magnetostrictive transducers and describe a method for making the proposed coils from insulated electrical wire such as enameled copper wire. Expressions for the electrical properties of the coils are also presented and compared with experimental measurements. An overlapped-2-channel folded-comer spiral-coil array is fabricated and applied to a magnetostrictive strip transducer generating and detecting fundamental torsional mode guided waves. From the results we conclude that the design and fabrication method make it possible to use the magnetostrictive transducers optimized for various guided wave applications and also will greatly help engineers gain easy access to the optimized transducers.

• The Bulletin of The Korean Astronomical Society
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• 제44권2호
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• pp.70.2-70.2
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• 2019

Recent observational works have reported spiral wave patterns (SWPs) in sunspots, but there is a lack of samples to derive the physical properties. In this presentation, we suggest the automatic method to detect the SWPs in observational data and present their statistical properties. From our method, we find more than 1000 SWPs observed by the Atmospheric Imaging Assembly onboard in the Solar Dynamic Observatory from 2013 to 2018. From our samples, more than half of the SWPs has the one spiral arm. The predominant oscillation period is 2 to 3 minutes. The rotating direction of the spiral arms does not depend on the latitude and the polarity of the sunspots. Our statistical results support the physical model suggested by Kang et al. (2019) that explain the generation of SWPs as the depth of the wave driving source and azimuthal modes in the straight vertical magnetic flux tube.

• Journal of the Korean Society for Nondestructive Testing
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• 제28권5호
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• pp.416-420
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• 2008

In EMAT field, spiral RF coils are much more widely used when compared with solenoid coils. In the field of the magnetostrictive strip transducers for long range ultrasonic testing of cylindrical structures, however, solenoid coils has been used. This seems to be attributed to the difficulty in fabricating low frequency (i.e., large size) spiral coils. In this paper, we describe a method for fabricating spiral coil magnetostrictive strip guided wave transducers from FFC (flexible flat cable). It is demonstrated through a comparison experiment that the spiral coil transducer has much superior performance (sensitivity, SNR, and guided wave direction control capability) than the previous transducer with solenoid coils.

• The Journal of the Korea institute of electronic communication sciences
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• 제16권1호
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• pp.203-210
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• 2021

Difficulties in treating chronic prostatitis cause physical pain and mental problems not only for the treating doctor, but also for the patient. Accordingly, the device of the present research was developed to help patients suffering from prostate symptoms due to the vibration effect of shock wave energy caused by thermal and mechanical interaction of the external shock wave. The purpose of this study is to provide an effective treatment means for prostatitis and BPH(Benign prostatic hyperplasia) by devising an extracorporeal shockwave therapy device that effectively applies the heat and vibration effects of concentrated energy by MCU and spiral coil module.

• The Bulletin of The Korean Astronomical Society
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• 제42권1호
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• pp.31.1-31.1
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• 2017

Spiral structure in disk galaxies is modeled with ncollisionless N-body simulations including live disks, halos, and bulges with a range of masses. Two of these simulations make long-lasting and strong two-arm spiral wave modes that last for about 5 Gyr with constant pattern speed. These two had a light stellar disk and the largest values of the Toomre Q parameter in the inner region at the time the spirals formed, suggesting the presence of a Q-barrier to wave propagation resulting from the bulge. The relative bulge mass in these cases is about 10%. Models with weak two-arm spirals had pattern speeds that followed the radial dependence of the Inner Lindblad Resonance. In addition to these, we also report a few more cases where two-armed spirals are developed and are maintained for a several rotation time scales.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.260-264
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• 2003

It is possible to design the high performance, integration and low cost radio frequency components by using LTCC(Low Temperature Cofired Ceramic) technology. But there is a critical point to design the spiral inductor because of crosstalk effects. of the crosstalk effect of the spiral inductor are investigated using full-wave analysis of the FEM(Finite Element Method) in this paper. The results show that input power of the spiral inductor are coupled from 0.1% to 10% above 3GHz. Therefore, we should consider the crosstalk effects when we design the LTCC.

• Journal of computational fluids engineering
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• 제14권3호
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• pp.16-24
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• 2009

Numerical simulation has been carried out to investigate the influence of radial temperature gradient on the Circular-Couette flow. Varying the Grashof number, we study the detailed flow and temperature fields. The current numerical results show good agreement with the analytical and experimental results currently available. It turns out that spiral vortices are generated by increasing temperature gradient. We classify the flow patterns for various Grashof number based on the characteristics of flow fields and spiral vortices. The correlation between Richardson number with wave number shows that the spiral angle and size of spiral vortices increase with increasing Richardson number.

• Asian Journal for Public Opinion Research
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• 제10권3호
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• pp.149-177
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• 2022

This study analyzes how inoculation affects the spiral of silence. Inoculation could be a beneficial tool in a democracy as it elevates citizens' resistance to attitude change "forced" by "the winning opinion" in the spiral of silence on a certain controversial issue. The study examines essential variables combined with the theories of inoculation and spiral of silence, such as resistance to counter-attitudinal attack, fear of isolation, and issue-involvement. A two-wave field experiment was employed to assess the formation of public opinion on Taiwan's political future with the People's Republic of China. Results support that inoculation enhanced people's resistance to attitude change and decreased their fear of isolation. Individuals who are more issue-involved were also shown to be more affected by inoculation, which allowed them to resist attitude change. The decreased fear of isolation, coupled with more issue involvement, might elevate people's willingness to speak out in public. More political discussions regarding an important public issue might be expected in a democracy.

• Steel and Composite Structures
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• 제22권1호
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• pp.45-61
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• 2016

The domestic and foreign scholars conducted many studies on mechanical properties of wave web steel beam and high-strength spiral stirrups confined concrete columns. Based on the previous research work, studies were conducted on the anti-seismic property of the end plate bolt connected wave web steel beam and high-strength spiral stirrups confined concrete column nodes applied with pre-tightening force. Four full-size node test models in two groups were designed for low-cycle repeated loading quasi-static test. Through observation of the stress, distortion, failure process and failure mode of node models, analysis was made on its load-carrying capacity, deformation performance and energy dissipation capacity, and the reliability of the new node was verified. The results showed that: under action of the beam-end stiffener, the plastic hinges on the end of wave web steel beam are displaced outward and played its role of energy dissipation capacity. The study results provided reliable theoretical basis for the engineering application of the new types of nodes.