• International Journal of Internet, Broadcasting and Communication
• /
• v.12 no.1
• /
• pp.67-72
• /
• 2020

The fifth generation (5G) mobile communication has an impact on the human life over the whole world, nowadays, through the artificial intelligence (AI) and the internet of things (IoT). The low latency of the 5G new radio (NR) access is implemented by the state-of-the art technologies, such as non-orthogonal multiple access (NOMA). This paper investigates a practical issue that in NOMA, for the practical channel models, such as fading channel environments, the successive interference cancellation (SIC) should be performed on the stronger channel users with low power allocation. Only if the SIC is performed on the user with the stronger channel gain, NOMA performs better than orthogonal multiple access (OMA). Otherwise, NOMA performs worse than OMA. Such the superiority requirement can be easily implemented for the channel being static or slow varying, compared to the block interval time. However, most mobile channels experience fading. And symbol by symbol channel estimations and in turn each symbol time, selections of the SIC-performing user look infeasible in the practical environments. Then practically the block of symbols uses the single channel estimation, which is obtained by the training sequence at the head of the block. In this case, not all the symbol times the SIC is performed on the stronger channel user. Sometimes, we do perform the SIC on the weaker channel user; such cases, NOMA performs worse than OMA. Thus, we can say that by what percent NOMA is better than OMA. This paper calculates analytically the percentage by which NOMA performs better than OMA in the practical mobile communication systems. We show analytically that the percentage for NOMA being better than OMA is only the function of the ratio of the stronger channel gain variance to weaker. In result, not always, but almost time, NOMA could perform better than OMA.

• Environmental and Resource Economics Review
• /
• v.23 no.3
• /
• pp.409-434
• /
• 2014

This paper estimates household demand for electricity using a micro-level household expenditure data set. A two-stage estimation method where the endogenous block price estimates are obtained from a discrete block choice model is used. This method successfully identifies a downward sloping conditional demand function with the data, while both the usual two-stage method with instrumental variable estimation and the Hewitt-Hanemann discrete-continuous model fail to do that. The paper simulates the impacts of two hypothetical pricing reforms that reduce the number of blocks and make the price gap smaller. It is shown that the reform may increase the overall consumer benefit, but is regressive.

• Journal of the Korean GEO-environmental Society
• /
• v.15 no.3
• /
• pp.15-19
• /
• 2014

Spilling pollutants and its contamination to the ground have serious impact to public resulting in various research about remediation techniques. In this study, the use of amphiphilic block copolymer for remediation was investigated with a series of laboratory tests on removal of hydrophobic contaminant in soil. Four types of amphiphilic block copolymer were developed and the efficiency of the cleaning was compared with surfactant using arbitrary diesel-contaminated soils. The results of the study show that the use of amphiphilic polymer in the soil washing process significantly enhanced the remediation of the contaminated soil and a potential of new methodology of eco-friendly remediation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.6C
• /
• pp.523-529
• /
• 2010

We propose a very low complexity lattice reduction (LR) algorithm for MIMO detection in time varying channels. The proposed scheme reduces the complexity by performing LR in a block-wise manner. The proposed scheme takes advantage of the temporal correlation of the channel matrices in a block and its impact on the unimodular matrices during LR process. From this, the proposed scheme can skip a number of redundant LR processes for consecutive channel matrices and performs a single LR in a block. The simulation results investigated in this letter reveal that the proposed detection scheme requires only 43.4% multiplications and 17.3% divisions of LLL-LR and only 50.2% multiplications and 68.2% divisions of the conventional adaptive LR with almost no performance degradation.

• Journal of Advanced Navigation Technology
• /
• v.17 no.6
• /
• pp.798-803
• /
• 2013

In this paper, the activities of North America to enhance the flight safety of helicopter were introduced. In North America, by 2009, 49% of worldwide civil helicopters are in operation. The development trends of North America to enhance the flight safety of helicopter are expected to have a significant impact to the other helicopter operating areas. The analysis of the case of Gulf of Mexico where large fleet of Helicopter in operations, FAA's NextGen program, and the Canadian plan to comply with the ICAO's Aviation System Block Upgrades plan shows the direction of helicopter avionic development for enhancing the flight safety of helicopter.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.18 no.1
• /
• pp.192-210
• /
• 2024

Most frequency-domain remote sensing image watermarking algorithms embed watermarks at random locations, which have negative impact on the watermark invisibility. In this study, we propose an adaptive watermarking scheme for remote sensing images that considers the information complexity to select where to embed watermarks to improve watermark invisibility without affecting algorithm robustness. The scheme converts remote sensing images from RGB to YCbCr color space, performs two-level DWT on luminance Y, and selects the high frequency coefficient of the low frequency component (HH^Y₂) as the watermark embedding domain. To achieve adaptive embedding, HH^Y₂ is divided into several 8*8 blocks, the entropy of each sub-block is calculated, and the block with the maximum entropy is chosen as the watermark embedding location. During embedding phase, the watermark image is also decomposed by two-level DWT, and the resulting high frequency coefficient (HH^W₂) is then embedded into the block with maximum entropy using α- blending. The experimental results show that the watermarked remote sensing images have high fidelity, indicating good invisibility. Under varying degrees of geometric, cropping, filtering, and noise attacks, the proposed watermarking can always extract high identifiable watermark images. Moreover, it is extremely stable and impervious to attack intensity interference.

• The KIPS Transactions:PartB
• /
• v.9B no.6
• /
• pp.745-752
• /
• 2002

The purpose of the paper is to enable a format transcoding between a heterogeneous compression format in a real time, and to enhance the compression ratio using characteristics of the compressed frame. In this paper, for the heterogeneous format transcoding, we tried to transcode from MPEG2 having a lower compression ratio to H.263 having a higher compression ratio. After analyzing MPEG 2 bit stream and H.263 bit stream of the same original video, we found that the number of intra coded macro blocks in MPEG 2 data is much higher than the number of the intra coded macro blocks in H.263 data. In the process of P frame generation, a intra coded macro block is generated when a motion estimation value representing the similarity between the previous frame and current frame does not meet a threshold. Especially the intra coded macro block has a great impact on the compression ratio. Hence the paper, we tried to minimize the number of intra coded macro blocks in H.263 data stream which is transcoded from MPEG 2 in a compressed domain. For the purpose, we propose a guided search method for transcoding the INTRA coded block into INTER coded block using the information about motion vectors surrounding the intra macro block in order to minimize the complexity of the motion estimation process. The experimental results show that the transcoding of MPEG 2 into H.263 can be done in a real time successfully.

• Journal of the Korean earth science society
• /
• v.32 no.6
• /
• pp.525-536
• /
• 2011

In any applications using various types of spatial data, it is very important to account for the scale differences among available data sets and to change the scale to the target one as well. In this paper, we propose to use a geostatistical downscaling approach based on vaiorgram deconvloution and block simulation to generate fine-scale categorical thematic maps from coarse-scale fraction data. First, an iterative variogram deconvolution method is applied to estimate a point-support variogram model from a block-support variogram model. Then, both a direct sequential simulation based on area-to-point kriging and the estimated point-support variogram are applied to produce alternative fine-scale fraction realizations. Finally, a maximum a posteriori decision rule is applied to generate the fine-scale categorical thematic maps. These analytical steps are illustrated through a case study of land-cover mapping only using the block fraction data of thematic classes without point data. Alternative fine-scale fraction maps by the downscaling method presented in this study reproduce the coarse-scale block fraction values. The final fine-scale land-cover realizations can reflect overall spatial patterns of the reference land-cover map, thus providing reasonable inputs for the impact assessment in change of support problems.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.12 no.2
• /
• pp.10-18
• /
• 2009

In order to determine the violation of right of light impact at adjacent residential area by high-rise building, analysis on the right of light for high-rise residential commercial complex building block at Gahngnam-ku, Seoul, Korea was carried out using Google Sketchup Pro. After the analysis th sunshine duration of B apartment decreased from 5 hours 16 minutes 3 hours 48 minutes by I hour 42 minutes after construction. It shows that the total sunshine duration is less than the Seoul City Government Standard which is more than 4 hours a day, or more than 2 consecutive hours. Lowering the heights of apartments by 54m would increase the total sunshine duration which would meet the Seoul City Government Standard by four hours seven minutes. Problems that rna lead to the violation on the right of light in the adjacent area should be discussed in advance and minimized by analyzing the right of light among buildings and structures which are scheduled to be constructed on the site during construction penni! process when high-rise building is proposed.

• International conference on construction engineering and project management
• /
• 2020.12a
• /
• pp.129-136
• /
• 2020

Augmented reality (AR) technology assists construction workers by superimposing additional virtual information onto their real worksite environments. Ideally, this provides them with a better understanding of their tasks and hence boosts task performance. However, the additional information that AR places in users' field of view could limit their ability to understand what is going on in their surroundings and to predict how conditions may change in the near future. AR-assisted systems on construction sites could therefore expose their users to safety risks due to disturbance from the system. Hence, it is important to understand how AR-assisted systems can block users' understanding of their immediate environments, and in turn, how worksite safety in the construction industry could be improved through better design of such systems. This preliminary research conducted a laboratory experiment that simulated rebar inspection tasks and compared the situational awareness of AR users against that of subjects using traditional paper-based inspection methods, as measured by the Situation Awareness Rating Technique. Based on the results, we discuss the safety impact of head-mounted AR-assisted displays on situational awareness during construction tasks.