• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.1892-1897
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• 2012

In this paper, efficient CNU(Check Node Update) algorithms are analyzed for high speed LDPC decoding in DVB-S2 standard. In aspect to CNU methods, there are some kinds of CNU methods. Among of them, MP (Min Product) method is quite often used in LDPC decoding. However MP needs LUT (Look Up Table) that is critical path in LDPC decoding speed. A new SC-NMS (Self-Corrected Normalized Min-Sum) method is proposed in the paper. NMS needs only normalized scaling factor instead of LUT and compensates the overestimation of MP approximation. In addition, SC method is proposed. It gives a faster convergence toward a decoded codeword. If a message change its sign between two iterations, it is not reliable and to avoid to propagate noisy information, its module is set to 0. The performance of SC-NMS has a little degrade compare to MP by 0.1 dB, however considering computational complexity and decoding speed, SC-NMS algorithm is optimal method for CNU algorithm.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.3 s.309
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• pp.43-53
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• 2006

As wireless network technology has advanced, demands for multimedia contents through mobile environment have tendered to upward. Since network situation is changing every moment and types of user terminals are diverse, it is difficult for a content provider to consider network situation and type of user terminal to provide multimedia contents. As one solution, transcoding techniques have been proposed, but those have much complexity. In this paper, in order to reduce computational complexity, we propose a fast mode decision using input modes, motion vectors, and residual energies which are obtained from input bitstream for 2:1 down-scaling spatial transcoding application. The proposed method reduces processing time in mode decision by restricting possible mode types based on input information. Experimental results show that the proposed method achieves about 2.66 times improvement in encoding time compared to the normal encoding process while the PSNR is degraded by about 0.04dB, and bit-rate is increased by 1.6%.

• Journal of Broadcast Engineering
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• v.22 no.3
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• pp.397-400
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• 2017

Recently, a lot of images containing various global movements have been generated by the activation of the photographic equipment such as the drone and the action cam. In this case, when the motion such as rotation, scaling is generated, it is difficult to expect a high coding efficiency in the conventional inter-picture prediction method using the 2D motion vector. In this paper, we propose a video coding method that reflects global motion through homography reference pictures. As a proposed method, there are 1) a method of generating a new reference picture by grasping a global motion relation between a current picture and a reference picture by homography, and 2) a method of utilizing a homography reference picture for inter-picture prediction. The experiment was applied to the HEVC reference software HM 14.0, and the experimental result showed an increase in encoding efficiency of 6.6% based on RA. Especially, the results using the videos with rotational motion have a maximum coding efficiency of 32.6%, which is expected to show high efficiency in video, which is often represented by complex global motion such as drones.

• Journal of Aerospace System Engineering
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• v.13 no.1
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• pp.38-46
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• 2019

There is a growing interest in engine diagnostic technology for gas turbine engines. An engine simulation program, precisely simulating the engine performance, is required in order to apply it to the engine diagnosis technology for engine health monitoring. In particular, the simulation program can predict not only design point performance but also off-design point and partial load performance in accurate. So the engine simulation program for the 2-spool separate flow type turbofan engine was developed and the JT9D-7R4G engine of PW(Pratt & Whitney) was analyzed. The steady-sate performance analysis is conducted at both design and off-design points in flight path and the differences between analysis results of takeoff and cruise conditions are compared. The effect of Reynold's correction method was analyzed as a scaling method of the engine component performance. The simulation results was compared with NPSS.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.3
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• pp.93-101
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• 2001

In this paper, we propose an image downscaler used in multimedia video applications, such as DTV, TV-PIP, PC-video, camcorder, videophone and so on. The proposed image downscaler provides a scaled image of high-quality and high-performance. This paper will explain the scaling theory using two-dimensional digital filters. It is the method that removes an aliasing noise and decreases the hardware complexity, compared with Pixel-drop and Upsamling. Also, this paper will prove it improves scaling precisians and decreases the loss of data, compared with the Scaler32, the Bt829 of Brooktree, and the SAA7114H of Philips. The proposed downscaler consists of the following four blocks: line memory, vertical scaler, horizontal scaler, and FIFO memory. In order to reduce the hardware complexity, the using digital filters are implemented by the multiplexer-adder type scheme and their all the coefficients can be simply implemented by using shifters and adders. It also decreases the loss of high frequency data because it provides the wider BW of 6MHz as adding the compensation filter. The proposed downscaler is modeled by using the Verilog-HDL and the model is verified by using the Cadence simulator. After the verification is done, the model is synthesized into gates by using the Synopsys. The synthesized downscaler is Placed and routed by the Mentor with the IDEC-C632 0.65${\mu}{\textrm}{m}$ library for further IC implementation. The IC master is fixed in size by 4,500${\mu}{\textrm}{m}$$\times$4,500${\mu}{\textrm}{m}$. The active layout size of the proposed downscaler is 2,528${\mu}{\textrm}{m}$$\times$3,237${\mu}{\textrm}{m}$.

• Wind and Structures
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• v.27 no.2
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• pp.101-109
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• 2018

Wall jet flow exists widely in engineering applications, including the simulation of thunderstorm downburst outflows, and has been investigated extensively by both experimental and numerical methods. Most previous studies focused on the scaling laws and self-similarity, while the effect of lip thickness and external stream height on mean velocity has not been examined in detail. The present work is a numerical study, using steady Reynolds-Averaged Navier Stokes (RANS) simulations at a Reynolds number of $3.5{\times}10^4$, of a turbulent plane wall jet with an external stream to investigate the influence of the wall jet domain on downstream development of the flow. The comparisons of flow characteristics simulated by the Reynolds stress turbulence model closure (Stress-omega, SWRSM) and experimental results indicate that this model may be considered reasonable for simulating the wall jet. The confined wall jet is further analyzed in a parametric study, with the results compared to the experimental data. The results indicate that the height and the width of the wind tunnel and the lip thickness of the jet nozzle have a great effect on the wall jet development. The top plate of the tunnel does not confine the development of the wall jet within 200b of the nozzle when the height of the tunnel is more than 40b (b is the height of jet nozzle). The features of the centerline flow in the mid plane of the 3D numerical model are close to those of the 2D simulated plane wall jet when the width of the tunnel is more than 20b.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.6
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• pp.490-496
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• 2018

The consistency of the initially designed waves in the domain is essential for accurate calculation of the added resistance in waves through CFD. In particular, unwanted reflected waves at domain boundaries can cause incorrect numerical solutions due to the superposition with initially designed waves. Euler Overlay Method(EOM) is one of the methods for reducing wave reflections by adding an additional source term to momentum and phase conservation equations, respectively. In this study, we apply the Euler Overlay Method(EOM) to the open-source CFD library, OpenFOAM(R), to simulate the accurate free-surface waves in the domain and the parametric study is performed for efficient implementation of Euler Overlay Method(EOM). Considering that the damping efficiency depends on the selection of the overlay parameter in the added source terms, the size of overlay zone and the wave steepness, the influences of these factors are tested through the wave elevation measured at constant time intervals in the 2D numerical wave tank. Through this process, guidelines for selection of optimal overlay parameter and overlay zone size that can be applied according to the scaling law are finally presented.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.278-284
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• 1998

This paper describes a l0b CMOS A/D converter (ADC) for HDTV applications. The proposed ADC adopts a typical multi-step pipelined architecture. The proposed circuit design techniques are as fo1lows: A selective channel-length adjustment technique for a bias circuit minimizes the mismatch of the bias current due to the short channel effect by supply voltage variations. A power reduction technique for a high-speed two-stage operational amplifier decreases the power consumption of amplifiers with wide bandwidths by turning on and off bias currents in the suggested sequence. A typical capacitor scaling technique optimizes the chip area and power dissipation of the ADC. The proposed ADC is designed and fabricated in s 0.8 um double-poly double-metal n-well CMOS technology. The measured differential and integral nonlinearities of the prototype ADC show less than ${\pm}0.6LSB\;and\;{\pm}2.0LSB$, respectively. The typical ADC power consumption is 119 mW at 3 V with a 40 MHz sampling rate, and 320 mW at 5 V with a 50 MHz sampling rate.

• Journal of the Korean Magnetics Society
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• v.26 no.6
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• pp.219-225
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• 2016

In this study, for assessment of degenerative knee joint cartilage disease we acquired images by fat suppressed 3D spoiled gradient recalled (SPGR) and fat suppressed 3D $T2^*$ weighted imaging techniques. To do a quantitative evaluation, the knee joint cartilage was divided into medial femoral cartilage (MFC), medial tibial cartilage (MTC), lateral femoral cartilage (LFC), lateral femoral cartilage (LFC) and patella cartilage (Pat) to measure their respective signal intensity values, signal-to-noise ratio, and contrast-to-noise ratio. As for the measured values, statistical significance between two techniques was verified by using Mann-Whitney U-Test. To do a qualitative evaluation, two radiologists have examined images by techniques after which image artifact, cartilage surface, tissue contrast, and depiction of lesion distinguishing were evaluated based on 4-point scaling (1: bad, 2: appropriate, 3: good, 4: excellent), and based on the result, statistical significance was verified by using Kappa-value Test. 3.0T MR system and HD T/R 8ch knee array coil were used to acquire images. As a result of a quantitative analysis, based on SNR values measured by using two imaging techniques, MFC, LFC, LTC, and Pat showed statistical significance (p < 0.05), but MTC did not (p > 0.05). As a result of verifying statistical significance for measured CNR value, MFC, LFC, and Pat showed statistical significance (p < 0.05), while MTC and LTC did not show statistical significance (p > 0.05). As a result of a qualitative analysis, by comparing mean values for evaluated image items, 3D $T2^*$ weighted Image has indicated a slightly higher value. As for conformance verification between the two observers by using Kappa-value test, all evaluated items have indicated statistically significant results (p < 0.05). 3D $T2^*$ weighted technique holds a clinical value equal to or superior to 3D SPGR technique with respect to evaluating images, such as distinguishing knee joint cartilages, comparing nearby tissues contrast, and distinguishing lesions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.949-956
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• 2005

In this paper, a new CPW-fed cross shape fractal antenna having a self-affinity is presented. This novel configuration, which has anisotropic scaling symmetry, makes smaller profile characteristic compared to the fractal antenna using a self-similarity. Increase of the iteration coefficient, which leads to decrease of the fundamental resonant frequency, shows a good impedance matching condition and multi-band characteristics due to new surface current paths. The radiation patterns are similar to those of monopole antennas. In the K3 stage of iteration, the proposed antenna shows a measured maximum gain 2.27 dBi at 940 MHz. A commercially available software based on the FDTD algorithm has been used to obtain the predicted results. In addition, an RT/Duroid 5880 substrate has been employed for the experimental results.