• Investigative Magnetic Resonance Imaging
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• 제24권3호
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• pp.95-122
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• 2020

In this article, we evaluated the performance of radiofrequency (RF) coils in terms of the signal-to-noise ratio (S/N) and homogeneity of magnetic resonance images when used for ultrahigh-frequency (UHF) 7T magnetic resonance imaging (MRI). High-quality MRI can be obtained when these two basic requirements are met. However, because of the dielectric effect, 7T magnetic resonance imaging still produces essentially a non-uniform magnetic flux (|B₁|) density distribution. In general, heterogeneous and homogeneous RF coils may be designed using electromagnetic (EM) modeling. Heterogeneous coils, which are surface coils, are used in consideration of scalability in the |B₁| region with a high S/N as multichannel loop coils rather than selecting a single loop. Loop coils are considered state of the art for their simplicity yet effective |B₁|-field distribution and intensity. In addition, combining multiple loop coils allows phase arrays (PA). PA coils have gained great interest for use in receiving signals because of parallel imaging (PI) techniques, such as sensitivity encoding (SENSE) and generalized autocalibrating partial parallel acquisition (GRAPPA), which drastically reduce the acquisition time. With the introduction of a parallel transmit coil (pTx) system, a form of transceiver loop arrays has also been proposed. In this article, we discussed the applications and proposed designs of loop coils. RF homogeneous coils for volume imaging include Alderman-Grant resonators, birdcage coils, saddle coils, traveling wave coils, transmission line arrays, composite right-/left-handed arrays, and fusion coils. In this article, we also discussed the basic operation, design, and applications of these coils.

• 대한전자공학회논문지SP
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• 제47권6호
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• pp.48-56
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• 2010

최근 멀티미디어 서비스에 대한 사용자들의 고화질, 고해상도 요구에 따라 비디오 코덱의 연산량이 크게 증가되었기 때문에, 모바일 장치 멀티미디어 장치에서 실시간 영상 서비스를 위해서는 많은 속도 개선이 필요하다. 이에 새롭게 등장한 멀티 코어 플랫폼을 이용한 코덱 병렬화에 대한 연구가 많이 이루어지고 있다. 본 논문에서는 비디오 코덱을 슬라이스 기반으로 병렬화 하는 방법을 제안한다. 병렬화를 위한 새로운 병렬 슬라이스(parallel slice)를 정의하고, 부호화 효율을 고려하여 병렬 슬라이스에 적합한 부호화 순서를 제안한다. 또한, 제안하는 슬라이스간의 동기화 시간을 최소화하기 위하여 복호화 가능 여부를 각각의 슬라이스에서 판단하는 동기화 방법을 제안한다. 제안하는 병렬화 슬라이스를 H.264/AVC에 적용하여 CIF 영상에 대해서 3.4%의 비트율 증가에 27.5%의 병렬화 속도 개선을 얻었으며, 720p 영상에 대해서는 2.7%의 비트율 증가에 40.7%의 병렬화 속도 개선을 얻었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.1101-1104
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• 1998

The modern multimedia applications which are video processor, video conference or video phone and so forth require real time processing. Because of a large amount of image data, those require high compression performance. In this paper, the prosposed image processing encoder was designed by using wavelet transform encoding. The proposed filter block can process imae data on the high speed because of composing individual function blocks by parallel and compute both highpass and lowpass coefficient in the same clock cycle. When image data is decomposed into multiresolution, the proposed scheme needs external memory and controller to save intermediate results and it can operate within 33MHz.

• Biomolecules & Therapeutics
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• 제22권2호
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• pp.83-92
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• 2014

Fatty acids (FAs) are highly diverse in terms of carbon (C) chain-length and number of double bonds. FAs with C>20 are called very long-chain fatty acids (VLCFAs). VLCFAs are found not only as constituents of cellular lipids such as sphingolipids and glycerophospholipids but also as precursors of lipid mediators. Our understanding on the function of VLCFAs is growing in parallel with the identification of enzymes involved in VLCFA synthesis or degradation. A variety of inherited diseases, such as ichthyosis, macular degeneration, myopathy, mental retardation, and demyelination, are caused by mutations in the genes encoding VLCFA metabolizing enzymes. In this review, we describe mammalian VLCFAs by highlighting their tissue distribution and metabolic pathways, and we discuss responsible genes and enzymes with reference to their roles in pathophysiology.

• 전자공학회논문지A
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• 제33A권5호
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• pp.155-164
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• 1996

The architecture of a programmable video codec IC is described that employs multiple vector processors in a single chip. The vector processors operate in parallel and communicate with one another through on-chip shared memories. A single scalar control processor schedules each vector processor independently to achieve real-tiem video coding with special vector instructions. With programmable interconnection buses, the proposed architecture performs multi-processing of tasks and data in video coding. Therefore, it can provide good parallelism as well as good programmability. especially, it can operate multithread video coding, which processes several independent image sequences simultaneously. We explain its scheduling, multithred video coding, and vector processor architectures. We implemented a prototype video codec with a 0.8um CMOS cell-based technology for the multi-standard videophone. This codec can execute video encoding and decoding simultaneously for the QCIF image at a frame rate of 30Hz.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.2271-2272
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• 2008

Recently, LDPC codes received a lot of attention in 4G. LDPC codes perform good error correction at high SNR. But LDPC codes are complex design and not good at low SNR. At low SNR, convolution codes and turbo codes show more good performance than LDPC codes. The main subject presented in this study is that parallel encoding and decoding according to SNR. The system chooses convolution codes at low SNR and chooses LDPC codes at high SNR.

• 한국경영과학회지
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• 제28권2호
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• pp.1-15
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• 2003

This paper presents a new evolutionary algorithm to solve complex multi-level integration problems, which is called multi-level symbiotic evolutionary algorithm (MEA). The MEA uses an efficient feedback mechanism to flow evolution information between and within levels, to enhance parallel search capability, and to improve convergence speed and population diversity. To show the MEA's applicability, It is applied to the integrated planning of production and distribution in supply chain management. The encoding and decoding methods are devised for the integrated problem. A set of experiments has been carried out, and the results are reported. The superiority of the algorithm's performance is demonstrated through experiments.

• Journal of Communications and Networks
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• 제13권1호
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• pp.63-69
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• 2011

In this paper, we propose a fixed-complexity sphere encoder (FSE) for multi-user multi-input multi-output (MU-MIMO) systems. The proposed FSE accomplishes a scalable tradeoff between performance and complexity. Also, because it has a parallel tree-search structure, the proposed encoder can be easily pipelined, leading to a tremendous reduction in the precoding latency. The complexity of the proposed encoder is also analyzed, and we propose two techniques that reduce it. Simulation and analytical results demonstrate that in a $4{\times}4$ MU-MIMO system, the proposed FSE requires only 11.5% of the computational complexity needed by the conventional QR decomposition with M-algorithm encoder (QRDM-E). Also, the encoding throughput of the proposed encoder is 7.5 times that of the QRDM-E with tolerable degradation in the BER performance, while achieving the optimum diversity order.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권3호
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• pp.397-403
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• 2015

This paper presents a new SOC test compression scheme in Embedded Deterministic Test (EDT) compression environment. Compressed test data is brought over the TAM from the tester to the cores in SOC and decompressed in the cores. The proposed scheme allows cores tested at the same time to share some test channels. By sharing free variables in these channels across test cubes of different cores decompressed at the same time, high encoding efficiency is achieved. Moreover, no excess control data is required in this scheme. The ability to reuse excess free variables eliminates the need for high precision in matching the number of test channels with the number of care bits for every core. Experimental results obtained for some SOC designs illustrate effectiveness of the proposed test application scheme.

• Journal of Communications and Networks
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• 제7권1호
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• pp.13-20
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• 2005

In this paper, a new multi carrier, direct sequence code division multiple access (MC-DS-CDMA) system is proposed. Our new signal construction is based on convolutional encoding of the transmitted data, serial-to-parallel (S/P) conversion of the encoded data, Walsh-Hadamard-transformation (WHT), a second S/P conversion of the WHT outputs, spread spectrum (SS) modulation with a common pseudo-noise (PN) sequence, and then multicarrier transmission. The system bit error rate (BER) performance in frequency selective fading channel in the presence of additive white Gaussian noise (AWGN) and a jamming tone is analyzed and simulated. The numerical results are compared with those from an orthogonal MC-DS-CDMA system of Sourour and Nakagawa [7]. It is shown that the two systems have almost the same BER performance, but the proposed scheme has better anti-jamming ability.