• Economic and Environmental Geology
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• v.25 no.1
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• pp.73-77
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• 1992

This paper compares numerical quadrature techniques for computing an inverse Fourier transform integral in two-dimensional resistivity modeling. The quadrature techniques using exponential and cubic spline interpolations are examined for the case of a homogeneous earth model. In both methods the integral over the interval from 0 to ${\lambda}_{min}$, where ${\lambda}_{min}$, is the minimum sampling spatial wavenumber, is calculated by approximating Fourier transformed potentials to a logarithmic function. This scheme greatly reduces the inverse Fourier transform error associated with the logarithmic discontinuity at ${\lambda}=0$. Numrical results show that, if the sampling intervals are adequate, the cubic spline interpolation method is more accurate than the exponential interpolation method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.5
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• pp.1180-1188
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• 2015

In this paper, we propose a new subband quantizer which is a type of quad-tree for applying to digital hologram compression based on Fresenelet transform. After executing Fresnelet transform to the captured digital holgoram, we analyze effect of the designed quantizer for the reconstructed objects from analyzing average energy of each coefficient and visual importance in all subbands. We analyze distribution of coefficient and set dynamic range for each subband, and then design subband quantizer. For enhancing effectiveness of the designed quantize, we adopt a method using the coefficients which are located out of dynamic range, which are named by exception indices. From this, we can obtain more effective quantizer which has higher performance in a range of σ′ = 5.0.

• Korean Journal of Optics and Photonics
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• v.29 no.3
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• pp.104-109
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• 2018

We explain the basic principle of transformation optics, and introduce several design techniques for transformation cavities that can maintain the characteristics of whispering gallery modes (WGMs) even if the cavity is strongly deformed from a circular shape. As a method of obtaining various transformation cavities under a specific conformal mapping, we suggest a method of parallel movement of the initial cavity domain, and a method of rotating the ellipse as a cavity domain. The internal wave pattern and the far-field output characteristics of several designed resonant modes are numerically calculated. From these results, it is confirmed that a variety of GRIN resonators are possible for a given conformal coordinate transformation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.986-991
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• 2018

In this paper, an A/D conversion module was designed and fabricated to improve the dynamic range of wideband digital receivers. The A/D conversion module for expanding the dynamic range converts signals into a digital signal by branching the input signal into the normal path and the amplification path according to the input signal level. Test results of the fabricated module show that the normal path of the A/D conversion module converts an input level of -57 dBm to -12 dBm into a digital signal, and the amplification path converts an input level of -30 dBm to +12 dBm into a digital signal without distortion. This translates to an input dynamic range characteristic of 69 dB. Moreover, it is confirmed that the constant output characteristic is exhibited at an instantaneous bandwidth of 100 MHz.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.9
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• pp.431-438
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• 2001

This paper present experimental results of source identification for non-minimum phase system. Generally, a causal linear system may be described by matrix form. The inverse problem is considered as a matrix inversion. Direct inverse method can\`t be applied for a non-minimum phase system, the reason is that the system has ill-conditioning. Therefore, in this study to execute an effective inversion, SVD inverse technique is introduced. In a Non-minimum phase system, its system matrix may be singular or near-singular and has one more very small singular values. These very small singular values have information about a phase of the system and ill-conditioning. Using this property we could solve the ill-conditioned problem of the system and then verified it for the practical system(cantilever beam). The experimental results show that SVD inverse technique works well for non-minimum phase system.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.11a
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• pp.103-106
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• 2016

인터넷 사용의 발달로 디지털 미디어 영상에 대한 불법 복제, 불법 배포 등의 문제가 완연해짐에 따라 영상의 제작자의 소유권과 저작권을 보호할 수 있는 워터마크 기법이 많이 연구되고 있다. 워터마크 시스템은 워터마크 삽입 후, 삽입정보를 알 수 없어야하는 비가시성 특성과 여러 공격에도 훼손되지 않고 추출될 수 있는 강인함을 가지고 있어야 한다. 이에 본 논문은 이산 웨이블릿 변환(DWT)으로 생성되는 부대역의 점유 주파수대역 특성과 공격이 이 부대역들에 미치는 영향을 분석하고, 이를 사용하여 디지털 워터마킹을 수행하였을 때 추출률을 최고로 하기 위해서는 변환된 부대역이 특정 범위내의 해상도를 가져야 한다는 것을 보인다. 본 연구는 실험적 방법으로 모든 부분연구는 실험에 의해서 결정된다.

• Journal of Advanced Navigation Technology
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• v.14 no.3
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• pp.446-451
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• 2010

This paper addressed an another scheme of distortion estimation method based on simplified inverse quantization in H.264/AVC. The distortion is calculated by the difference of coefficient between quantized transform coefficients and that of inverse. In general, these process included such transforms as discrete cosine transform(DCT), quantization, inverse quantization(IQ), and Inverse DCT(IDCT). In proposed approach, IQ as well as IDCT process are skipped because of replacing a couple of approximated formulas. Some simulation have been conducted and it showed that the PSNR was almost the same, and reduced the rate-distortion optimization(RDO) mode decision time of 8~15% in comparison with conventional method.

• The Korean Journal of Applied Statistics
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• v.22 no.5
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• pp.971-979
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• 2009

In this paper, we introduce the method that reduces the bias when the transformation and back-transformation approach is applied in GARCH models. A parametric bootstrap is employed to compute the conditional expectation which is the prediction value to minimize mean square errors in the original scale. Through the analyese of returns of KOSPI and KOSDAQ, we verified that the proposed method provides a bias-reduced estimation for the prediction value.

• 전자공학회논문지 IE
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• v.49 no.2
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• pp.18-23
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• 2012

A method to determine the equivalent circuits of broadband ultrasound transducers is necessary for designing filters that match the impedances of the transducer and the analysis of the transducer. A method is proposed to determine the equivalent circuits of broadband transducers with 2 resonances in the frequency band of interest. The circuit parameters are estimated by iterative Levy method with the measured electrical conductance data. The method is illustrated by computing the conductance and susceptance of the equivalent circuits of 3 types of broadband transducers. The equivalent circuit of a transducer.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2003.11a
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• pp.7-10
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• 2003

인터프레임 웨이블렛 부호화(Interframe Wavelet Coding)는 3D 서브밴드(Subband) 부호화라고도 하며, 기존의 DCT기반 Hybrid 동영상 부호화 방식에 비해 압축 효율이 우수하고. 특히 스케일러빌리티 기능이 뛰어난 부호화 방법이다. 인터프레임 웨이블렛 부호화 방법에서 복호화 과정 중 가장 연산 량이 많이 요구되는 역(inverse) 웨이블렛 변환이다 역 웨이블렛 변환의 연산 량은 복호화 과정에서 적용된 웨이블렛 변환과 동일한 연산량을 요구한다. 이는 순방향과 역방향에서 동일 길이의 필터와 분해 레벨을 사용해야 하기 때문이다. 이 웨이블렛 변환의 연산 량을 줄이기 위해 본 논문에서는 기존의 시간 밴드 영상에 대해 동일 한 웨이블렛 필터를 사용하여 공간 웨이블렛 필터를 적용하던 것을. 로우밴드에는 9/7 필터를 적용하고 하이 밴드에는 Haar필터를 사용하는 방법을 제안한다. PSNR 실험에서 기존의 9/7 필터만을 사용하는 경우와 비교한 결과 거의 차이가 없었다.