• 대한수학회보
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• 제50권3호
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• pp.1049-1060
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• 2013

In this paper we study the infiniteness of Hilbert 2-class field towers of imaginary quadratic function fields over $\mathbb{F}_q(T)$, where $q$ is a power of an odd prime number.

• 충청수학회지
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• 제21권1호
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• pp.61-69
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• 2008

For a real subextension of some cyclotomic function field with a non-cyclic Galois group order $l^2$, l being a prime different from the characteristic of function field, we compute the index of the Sinnott group of circular units.

• 한국전기전자재료학회논문지
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• 제25권2호
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• pp.159-164
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• 2012

In this paper, it tried to develop the core sensor for detection of micro magnetic field in electric wires. The sensor is non contact type and is consisted of ferrite core for low price. To investigate their properties for variations of current, it changed the number of winding and the length of sample core, it examined, to check the live wire situation in built-in wires, electrical characteristics due to difference between electric wires and core sensor. As the results, it verified live wire situation at the number of winding(5,000) and within length of 6[cm]. Also, it obtained magnetic field magnitude decreased inverse proportion ratio to a square about difference between electric wires and core sensor.

• 전자공학회논문지B
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• 제31B권8호
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• pp.109-118
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• 1994

We proposed new field/frame mode selection quantization and buffer control strategy for interlaced digital HDTV image coding system. The field/frame mode selection is performed based on the mean square error and number of generated bits for each superblock. The quantization factor for each superblock is determined by the characteristics of human visual system and buffer status. The statistical characteristics of the number of generated bits for basis block and the prediction of buffer status are used for buffer control. Simulation results show that the proposed field/frame mode selection and rate buffer control. Simulation results show that the proposed field/frame mode selection and rate buffer control strategy have good subjective image quality and have stable buffer status.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.680-683
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• 1997

Fieldbus system should be designed by considering the number of sensors/actors(actuators+ controllers) and their sampling times. But the number of sensors/actors and which are connected to the network bus can be varied by addition and/or fault of the field devices. That variation decreases the efficiency of system which is off-line designed optimally. This paper proposes an algorithm that ensures transmission of cyclic data even though there is the number change in the field devices. We assign the different weight values to cyclic data and acyclic data. By simulation and experiment, the cyclic and acyclic data are processed via the proposed network, and the results are compared with those of the Profibus system. It is shown that the proposed algorithm is more robust with the uncertainties of the field devices of the control system.

• The Journal of the Acoustical Society of Korea
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• 제23권1E호
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• pp.3-9
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• 2004

An important inverse problem in the field of acoustics is that of reconstructing the strengths of a number of sources given a model of transmission paths from the sources to a number of sensors at which measurements are made. In dealing with this kind of the acoustical inverse problem, strengths of the discretised source distribution can be simply deduced from the measured pressure field data and the inversion of corresponding matrix of frequency response functions. However, deducing :he solution of such problems is not straightforward due to the practical difficulty caused by their inherent ill-conditioned behaviour. Therefore, in order to overcome this difficulty associated with the ill-conditioning, the problem is replaced by a nearby well-conditioned problem whose solution approximates the required solution. In this paper a microphone array are identified for which the inverse problem is optimally conditioned, which can be robust to contaminating errors. This involves sampling both source and field in a manner which results in the discrete pressures and source strengths constituting a discrete Fourier transform pair.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.54-60
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• 2006

This study looks over the relation between propeller and noise in ship stern structure. Near field noise and vibration measurements are compared with the analytical results using wave number method. To avoid singularity in wave number integration method, fast field method is introduced. Analytical results show that main transmission mechanism of high frequency noise is structure-borne type and that of low frequency noise is a air-borne type.

• Journal of Mechanical Science and Technology
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• 제19권3호
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• pp.913-923
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• 2005

The dynamic mixed model (DMM) combined with a box filter of Zang et. al. (1993) has been generalized for passive scalar transport and applied to large eddy simulation of turbulent channel flows with Prandtl number up to 10. Results from a priori test showed that DMM is capable of predicting both subgrid-scale (SGS) scalar flux and dissipation rather accurately for the Prandtl numbers considered. This would suggest that the favorable feature of DMM, originally developed for the velocity field, works equally well for scalar transport problem. The validity of the DMM has also been tested a posteriori. The results of the large eddy simulation showed that DMM is superior to the dynamic Smagorinsky model in the prediction of scalar field and the model performance of DMM depends to a lesser degree on the ratio of test to grid filter widths, unlike in the a priori test.

• Journal of applied mathematics & informatics
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• 제12권1_2호
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• pp.267-279
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• 2003

The present investigation deals with the application of Adomian's decomposition method to blood flow through a constricted artery in the presence of an external transverse magnetic field which is applied uniformly. The blood flowing through the tube is assumed to be Newtonian in character. The expressions for the two-term approximation to the solution of stream function, axial velocity component and wall shear stress are obtained in this analysis. The numerical solutions of the wall shear stress for different values of Reynold number and Hartmann number are shown graphically. The solution of this theoretical result for a particular Hart-mann number is compared with the integral method solution of Morgan and Young［17］.

• 대한조선학회논문집
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• 제41권2호
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• pp.70-78
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• 2004

The present study numerically investigates two-dimensional laminar flow past a circular cylinder in an aligned magnetic field using the spectral method. Numerical simulations are performed for flow fields with Re=100 and 200 in the range of 0$\leq$N$\leq$10, where Ν is the Stuart number that is the ratio of electromagnetic force to inertial force. The present study reports the detailed information of flow quantities on the cylinder surface at different Stuart numbers. It is shown that the vortex shedding can be controlled by the magnetic force representing the Stuart number. As Ν increases, the vortex shedding becomes weaker, resulting in drag reduction whose magnitude is the largest at a critical value. In addition, as the magnetic force increases, the lift amplitude decreases, reaching zero at the critical number.