• Bulletin of the Korean Mathematical Society
• /
• v.51 no.1
• /
• pp.29-41
• /
• 2014

In this paper, we prove that infinite-dimensional vector spaces of -dense curves are generated by means of the functional equations f(x)+f(2x)+${\cdots}$+f(nx) = 0, with $n{\geq}2$, which are related to the partial sums of the Riemann zeta function. These curves ${\alpha}$-densify a large class of compact sets of the plane for arbitrary small ${\alpha}$, extending the known result that this holds for the cases n = 2, 3. Finally, we prove the existence of a family of solutions of such functional equation which has the property of quadrature in the compact that densifies, that is, the product of the length of the curve by the $n^{th}$ power of the density approaches the Jordan content of the compact set which the curve densifies.

• 한국연소학회:학술대회논문집
• /
• 2012.11a
• /
• pp.355-357
• /
• 2012

A probability density function (PDF) approach to account for turbulence-chemistry interaction in the context of large eddy simulation (LES) based simulation of scramjets is developed. To solve the high-dimensional joint-composition PDF transport equation robustly, the semi-discrete quadrature method of moments (SeQMOM) is recently proposed [1]. The SeQMOM approach addresses key numerical issues in LES related to the inaccuracies in computing filter-scale gradients, enabling an efficient and numerically consistent solution of the PDF transport equation. The computational tool is used to simulate a cavity-stabilized Mach 2.2 supersonic combustor.

• Journal of Communications and Networks
• /
• v.8 no.1
• /
• pp.1-7
• /
• 2006

Quadrature amplitude modulation-spread spectrum (QAM-SS) and code division multiplexing (CDM) are multi-level modulation schemes with high performance but they cause a large peak-average power ratio (PAPR). Therefore, this paper proposes a novel modulation scheme for high-rate transmission which follows a sequence of CDM-mapping-CDM not only to correct the above-mentioned problem but also offer a high flexibility in obtaining arbitrary multilevel modulation with very low implementation complexity and high performance.

• The Journal of the Acoustical Society of Korea
• /
• v.23 no.3
• /
• pp.221-227
• /
• 2004

This paper presents the subband affine projection algorithm(SAPA). The improved performance of SAPA is achieved by applying the affine projection algorithm to the subband adaptive structure. In this algorithm, the weight updating formula of adaptive filter is simply derived by using the orthogonal quadrature filter(OQF) as an analysis filter bank for subband filtering. The derived SAPA has the fast convergence speed and small computational complexity. The efficiency of the proposed algorithm for colored input signal is evaluated through some experiments.

• Proceedings of the KIEE Conference
• /
• 1999.07c
• /
• pp.1158-1160
• /
• 1999

This paper proposes a SSSC(Static Synchronous Series Compensator) power flow model to be incorporated into power flow calculation for the steady state analysis of the power system. SSSC provides controllable compensating voltage, which is in quadrature with the line current, over an capacitive and an inductive range, independently of the magnitude of the line current. This SSSC model is obtained from the injection model for series connected VSC(Voltage Source Converter) by adding a constraint that the injected voltage should be in quadrature with the line current. In this paper the static model is implemented into the continuation power-flow (CPF) program. It is shown that SSSC has its intrinsic superiority over TCSC in controllable power flow range.

• Proceedings of the IEEK Conference
• /
• 2009.05a
• /
• pp.9-11
• /
• 2009

It is well-known that the performance of turbo codes can be improved by allocating different energies per code symbol. In this paper, based on this observation, we propose a joint encoding and modulation scheme for quadrature amplitude modulated turbo code systems. In the proposed scheme, the amount of energy difference between the turbo coded symbols is optimized by optimizing the constellation of quadrature amplitude modulation(QAM). The proposed scheme offers better coding gain compared to the conventional combination of binary turbo code and QAM at the bit error rate of $10^{-5}$.

• ETRI Journal
• /
• v.25 no.4
• /
• pp.231-237
• /
• 2003

We derive and analyze the exact closed-form expression for the average bit error probability (BEP) of M-ary square quadrature amplitude modulation (QAM) for diversity reception in frequency-nonselective Nakagami fading. A maximal ratio combining (MRC) diversity technique with independent or correlated fading cases are considered. Numerical results demonstrate error performance improvement with the use of MRC diversity reception. The presented new expressions offer a convenient way to evaluate the performance of M-ary square QAM with an MRC diversity combiner for various cases of practical interest.

• ETRI Journal
• /
• v.34 no.4
• /
• pp.617-620
• /
• 2012

The denoising mapping with the closest-neighbor clustering (CNC) method in denoise-and-forward two-way relay channels is studied. Specifically, the symmetry of the constellations in source terminals A and B is utilized to reduce the complexity of the CNC method. The specific case considered first to illustrate how the constellation symmetry works in the CNC method is the quadrature phase-shift keying constellation in A and B and the single-antenna deployment in all terminals. This case study shows that an enormous complexity reduction can be achieved. Next, the result is extended to multiple-antenna scenarios and square quadrature amplitude modulations.

• Proceedings of the KSMRM Conference
• /
• 2001.11a
• /
• pp.175-175
• /
• 2001

목적： 현재 3.0T MRI system은 세계적으로 개발이 진행되고 있는 가운데, 3.0T에서 사용할 수 있는 RF coil의 개발이 시급한 상황이다. 1.0T 및 1.5T MRI 와는 달리 3.0T에서 사용할수 있는 Body coil 및 그에 따른 High power RF amplifier 제작에 많은 제약이 있다. 작은 용량의 RF amplifier를 이용하여 신체의 부분을 촬영 하고자 한다면, Tx/Rx 가능한 coil을 이용하면 가능할 것이다. 이러한 이유로 본 연구에서는 Tx/Rx 가능한 Quadrature type T/L-spine RF coil을 설계, 제작하여 3.0T 고자장 자기공명 영상장치에서의 임상진단 활용범위를 확대하였다. 3.0 Tesla 자기공명 영상장치에 사용을 위한 Quadrature type의 L-spine TX/RX RF 코일을 개발하여 고자장 자기공명 영상장치에서의 임상진단 활용범위의 확대를 목적으로 한다.

• Proceedings of the KSMRM Conference
• /
• 2001.11a
• /
• pp.145-145
• /
• 2001

목적 현재 3.0T MRI system은 세계적으로 개발이 진행되고 있는 가운데, 3.0T에서 사용 할 수 있는 RF coil의 개발이 시급한 상황이다. 1.0T 및 1.5T MRI 와는 달리 3.0T에서 사용할 수 있는 Body coil 및 그에 따른 High power RF amplifier 제작에 많은 제약이 있다. 작은 용량의 RF amplifier를 이용하여 신체의 부분을 촬영 하고자 한다면, Tx/Rx 가능한 coil을 이용하면 가능할 것이다. 이러한 이유로 본 연구에서는 Tx/Rx 가능한 Quadrature type Th-spine RF coil을 설계, 제작하여 3.0T 고자장 자기공명 영상장치에서의 임상진단 활용범위를 확대하였다. 3.0 Tesla 자기공명 영상장치에 사용을 위한 Quadrature type의 L-spine TX/RX RF 코일을 개발하여 고자장 자기공명 영상장치에서의 임상진단 활용범위의 확대를 목적으로 한다.