• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.9
• /
• pp.1710-1718
• /
• 2015

Selected mapping (SLM) is an effective scheme to reduce the peak to average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) system. For data recovery, the receiver needs to know the side information (SI) on the scrambling sequence selected by the transmitter. In this paper, a new SLM scheme is proposed, which can reduce implementation complexity substantially by allowing the receiver to recover the data without SI. In the proposed SLM method, the concept of virtual channel corresponding to the convolution of the multipath channel and the inverse discrete fourier transform (IDFT) of the scrambling sequence is assumed. The receiver can recover the data without SI by using the virtual channel estimated with pilot signals. It is shown by simulation that the proposed SLM has PAPR reduction and BER performances similar to the previous SLM schemes while it can reduce implementation complexity substantially.

• KIPS Transactions on Software and Data Engineering
• /
• v.4 no.4
• /
• pp.187-194
• /
• 2015

In this paper, we present an effective visual odometry estimation system to track the real-time pose of a camera moving in 3D space. In order to meet the real-time requirement as well as to make full use of rich information from color and depth images, our system adopts a feature-based sparse odometry estimation method. After matching features extracted from across image frames, it repeats both the additional inlier set refinement and the motion refinement to get more accurate estimate of camera odometry. Moreover, even when the remaining inlier set is not sufficient, our system computes the final odometry estimate in proportion to the size of the inlier set, which improves the tracking success rate greatly. Through experiments with TUM benchmark datasets and implementation of the 3D scene reconstruction application, we confirmed the high performance of the proposed visual odometry estimation method.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.3C
• /
• pp.288-296
• /
• 2009

In POCS (projection onto convex sets)-based reconstruction of HR (high resolution) image, the quality of reconstructed image is gradually improved through iterative motion estimation and image restoration. The amount of computation, however, increases because of the repeated inter-frame motion estimation. In this paper, an HR reconstruction algorithm is proposed where modified ARPS (adaptive rood pattern search) and POCS are simultaneously performed. In the modified ARPS, the motion estimates obtained from phase correlation or from the previous steps in POCS restoration are utilized as the initial reference in the motion estimation. Moreover, estimated motion is regularized with reference to the neighboring blocks' motion to enhance the reliability. Computer simulation results show that, when compared to conventional methods which are composed of full search block matching and POCS restoration, the proposed method is about 30 times faster and yet produces HR images of almost equal or better quality.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.9C
• /
• pp.712-719
• /
• 2008

Temporal error concealment indicates the algorithm that restores the lost video data using temporal correlation between previous frame and current frame with lost data. It can be categorized into the methods of block-based and pixel-based concealment. The proposed method in this paper is for pixel-based temporal error concealment using affine transform. It outperforms especially when the object or background in lost block has geometric transform which can be modeled using affine transform, that is, rotation, magnification, reduction, etc. Furthermore, in order to maintain good performance even though one or more motion vector represents the motion of different objects, we defines a cost function. According to cost from the cost function, the proposed method adopts affine error concealment adaptively. Simulation results show that the proposed method yields better performance up to 1.9 dB than the method embedded in reference software of H.264/AVC.

• Journal of Korean Society of Environmental Engineers
• /
• v.33 no.1
• /
• pp.1-8
• /
• 2011

This article proposes a hybrid approach involved in determining the size of stormwater control facilities as part of a very large scale urban retrofit project. The objective of the proposed hybrid approach is to restore the pre-development hydrologic cycle. Firstly, an appropriate IETD is determined to isolate single storm events from the continuous rainfall record. Then, using the NRCS-CN method, direct runoff and infiltration volume are computed for every storm events. Long-term statistics of direct runoff and infiltration volume are analyzed in each case of pre-development, post development, post development with detention only, and post-development with the proposed hybrid approach. In order to preserve long-term statistics of direct runoff and infiltration volume in the case of pre-development, the size of detention and infiltration-based retention are estimated using the genetic algorithm. The result shows that the proposed hybrid approach is very useful for restoring statistics of natural direct runoff and infiltration volume.

• Economic and Environmental Geology
• /
• v.48 no.6
• /
• pp.477-490
• /
• 2015

In this study, we investigated the restoration possibility of the old streams by enhancing the rainwater infiltration in the watershed of Deokjin Park, Jeonju City. This study was performed by modeling groundwater discharge to the streams under various conditions. We assessed the amount and location of groundwater recharge enhancement to restore the streams and evaluated whether the baseflows of the restored streams are sufficient to keep the water ecosystem of the Deokjin Pond. The results show that the baseflow of the streams can persist for a longer time even during the dry season when the rainwater drainage system is recovered similarly to the those before development using low impact development (LID) techniques. The enhancements of recharge in the headwater area, which is the area around the zoo and Daeji Village in the Deokjin Park watershed, is useful to increase the baseflows of the downstream reaches. Furthermore, spreaded recharge over a widespread area is better to prevent the streams from drying than the intensive recharge at a few sites.

• Food Science and Preservation
• /
• v.17 no.6
• /
• pp.763-769
• /
• 2010

We examined variations in ginger dehydration and recovery rate upon use of dextrose of different equivalence values. The dehydration rate varied with dextrose equivalent and the dehydration rate increased as the equivalence value increased. Both dehydration and recovery rates varied with dextrose molecular weight. Moisture content was lowest in samples prepared by freeze-drying, and neither dextrose equivalent nor molecular weight affected moisture level. Upon color analysis, ginger dried using dextrose varying in equivalence and molecular weight was similar in color to the original material, unlike ginger dried by other methods. Hot-air-dried ginger scored lowest in all sensory tests, compared with ginger prepared by molecular press dehydration using dextrose varying in equivalence and molecular weight. With respect to the appearance of ginger, freeze-dried samples were optimal, but molecular press dehydration yielded samples that scored best upon overall evaluation. When all quality evaluation items were taken together, molecular press dehydration resulted in a better quality product than the older hot-air or freeze-drying methods.

• Journal of the Korea Computer Graphics Society
• /
• v.23 no.4
• /
• pp.11-19
• /
• 2017

We propose a new pipeline of fluid surface reconstruction that incorporates hybrid SDF(signed distance fields) and adaptive fluid surface techniques to finely reconstruct liquid-solid mixed surfaces. Previous particle-based fluid simulation suffer from a noisy surface problem when the particles are distributed irregularly. If a smoothing scheme is applied to reduce the problem, sharp and detailed features can be lost by over-smoothing artifacts. Our method constructs a hybrid SDF by combining signed distance values from the solid and liquid parts of the object. We also proposed a method of adaptively reconstructing the surface of the fluid to further improve the overall efficiency. This not only shows the detailed surface of the solid and liquid parts, but also the detail of the solid surface and the smooth fluid surface when both materials are mixed. We introduce the concept of guiding shape and propose a method to get signed distance value quickly. In addition, the hybrid SDF and mesh reconstruction techniques are integrated in the adaptive framework. As a result, our method improves the overall efficiency of the pipeline to restore fluid surfaces.

• Ecology and Resilient Infrastructure
• /
• v.10 no.2
• /
• pp.40-49
• /
• 2023

To reduce the damage of extreme flooding caused by climate change and to create flood mitigation sections in a nature-friendly riparian area, it is necessary to restore the floodplain area by referring to the past floodplain section of the current inland waterfront area before the levee was built. This study proposed a method of selecting a location for floodplain restoration using old maps of the Geum River study section and analyzed the effect of flood level reduction through unsteady flow numerical simulations using the floodplain as a flood mitigation space. As a result of analyzing changes in the river areas using old maps, the river section was estimated to gradually reduce by 27.8% (1,059,380 m²) in 2020 compared to 1919, and it was found to have an effective storage capacity of 2,200,868 m³ when restored to offline storage. The flood level and discharge control effects analyzed based on HEC-RAS unsteady flow simulation were 16 cm and 219.01 m³/s, respectively, in the downstream cross-section. In the numerical simulation in this paper, the flood mitigation space was applied as an offline reservoir. The effect of reducing the flood level may differ if levee retreat/relocation is applied.

• Proceedings of the Acoustical Society of Korea Conference
• /
• autumn
• /
• pp.85-88
• /
• 1999

Adapted Local Trigonometric Transforms은 매우 높은 energy compaction을 가지므로 음성 및 영상신호에 이용하려는 시도가 이루어지고 있다. [1] 그러나 이 경우 복원 된 신호에는 시간 영역에서 불연속점이 발생하여 일종의 tick noise가 발생한다. 또한 phase성분을 잃게 되어 금속성 잡음도 추가하여 나타난다. 본 논문에서는 이러한 문제점을 해결하기 위한 Polynomial fitting 방식과 Wavelet Packet Transforms 방식을 제안한다. Polynomial fitting 방식으로는 시간축상에서 발생하는 문제를 해결하고 Wavelet Packet Transforms으로 Phase 문제를 해결한다. [2,3] 실험결과, 압축이전의 신호와 비교할 때 SNR에 있어서 개선을 보이며 tick noise와 금속성 잡음이 제거된 개선된 신호음을 확인 할 수 있었다.