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On Rate-adaptive LDPC-based Cross-layer SVC over Bursty Wireless Channels
( Yongju Cho ),( Jihun Cha ),( Hayder Radha ),( Kwang-deok Seo ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.9
Recent studies have indicated that a significant improvement in wireless video throughput can be achieved by Cross Layer Design with Side-information (CLDS) protocols. In this paper, we derive the operational rate of a CLDS protocol operating over a realistic wireless channel. Then, a Rate-Distortion (R-D) empirical model for above-capacity Scalable Video Coding (SVC) is deduced to estimate the loss of video quality incurred under inaccurate rate estimation scenarios. Finally, we develop a novel Unequal Error Protection (UEP) scheme which leverages the characteristics of LDPC codes to reduce the distortion of video quality in case of typically-observed burst wireless errors. The efficacy of the proposed rate adaptation architecture over conventional protocols is demonstrated by realistic video simulations using actual IEEE 802.11b wireless traces.
Multihop Rate Adaptive Wireless Scalable Video Using Syndrome-Based Partial Decoding
Yongju Cho,Jungil Seo,Jungwon Kang,Hayder Radha,Jinwoo Hong 한국전자통신연구원 2010 ETRI Journal Vol.32 No.2
The overall channel capacity of a multihop wireless path drops progressively over each hop due to the cascading effect of noise and interference. Hence, without optimal rate adaptation, the video quality is expected to degrade significantly at any client located at a far-edge of an ad-hoc network. To overcome this limitation, decoding and forwarding (DF), which fully decodes codewords at each intermediate node, can be employed to provide the best video quality. However, complexity and memory usage for DF are significantly high. Consequently, we propose syndrome-based partial decoding (SPD). In the SPD framework an intermediate node partially decodes a codeword and relays the packet along with its syndromes if the packet is corrupted. We demonstrate the efficacy of the proposed scheme by simulations using actual 802.11b wireless traces. The trace-driven simulations show that the proposed SPD framework, which reduces the overall processing requirements of intermediate nodes, provides reasonably high goodput when compared to simple forwarding and less complexity and memory requirements when compared to DF.
Seo, Jeong Gil,Youn, Min Hye,Bang, Yongju,Song, In Kyu Elsevier 2010 International journal of hydrogen energy Vol.35 No.22
<P><B>Abstract</B></P><P>Mesoporous Ni–Al<SUB>2</SUB>O<SUB>3</SUB> (<I>X</I>NiAE) aerogel catalysts with different Ni/Al atomic ratio (<I>X</I>) were prepared by a single-step sol-gel method and a subsequent CO<SUB>2</SUB> supercritical drying method. The effect of Ni/Al atomic ratio of mesoporous <I>X</I>NiAE aerogel catalysts on their physicochemical properties and catalytic activity for steam reforming of liquefied natural gas (LNG) was investigated. Textural properties and chemical properties of <I>X</I>NiAE catalysts were strongly influenced by Ni/Al atomic ratio. Nickel species were highly dispersed on the surface of <I>X</I>NiAE catalysts through the formation of surface nickel aluminate phase. In the steam reforming of LNG, both LNG conversion and hydrogen yield showed volcano-shaped curves with respect to Ni/Al atomic ratio. Average nickel diameter of <I>X</I>NiAl catalysts was well correlated with LNG conversion and hydrogen yield over the catalysts. Among the catalysts tested, 0.35NiAE (Ni/Al=0.35) catalyst with the smallest average nickel diameter showed the best catalytic performance. The highest surface area, the largest pore volume, the largest average pore size, and the highest reducibility of 0.35NiAE catalyst were also partly responsible for its superior catalytic performance.</P> <P><B>Research highlights</B></P><P>►Hydrogen was produced by steam reforming of liquefied natural gas (LNG). ►Mesoporous Ni–Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalysts were used. ►Catalytic performance strongly depended on Ni/Al atomic ratio. ►Average nickel diameter played an important role.</P>
On a Quasitoric Virtual Braid Presentation of a Virtual Link
Bae, Yongju,Seo, Seogman Department of Mathematics 2015 Kyungpook mathematical journal Vol.55 No.1
We introduce a quasitoric virtual braid and show that every virtual link can be obtained by the closure of a quasitoric virtual braid. Also, we show that the set of quasitoric virtual braids with n strands forms a group which is a subgroup of the n-virtual braid group.
Bang, Yongju,Seo, Jeong Gil,Youn, Min Hye,Song, In Kyu Elsevier 2012 International journal of hydrogen energy Vol.37 No.2
<P><B>Abstract</B></P> <P>A mesoporous Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalyst was prepared by a single-step epoxide-driven sol-gel method and a subsequent supercritical CO<SUB>2</SUB> drying method (NA-ES catalyst). For comparison, a mesoporous Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalyst was also prepared by a single-step alkoxide-based sol-gel method and a subsequent supercritical CO<SUB>2</SUB> drying method (NA-AS catalyst). Differences in physicochemical properties and catalytic activities of mesoporous Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalysts in the steam reforming of liquefied natural gas (LNG) were investigated. Textural properties of Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalysts were affected by the preparation method. Nickel species were highly dispersed in alumina through the formation of nickel aluminate phase in both NA-ES and NA-AS catalysts. However, chemical states of Al atoms in both catalysts were quite different. In addition, nickel species in the NA-ES catalyst exhibited high reducibility and high dispersion compared to those in the NA-AS catalyst. In the steam reforming of LNG, NA-ES catalyst exhibited a better catalytic performance than NA-AS catalyst in terms of LNG conversion and hydrogen yield, although both catalysts showed a stable catalytic performance during the reaction without deactivation behavior. Furthermore, NA-ES catalyst with small average nickel diameter suppressed water-gas shift reaction. Reducibility and dispersion of nickel species served as important factors determining the catalytic performance of the catalysts.</P> <P><B>Graphical abstract</B></P> <P>In the steam reforming of liquefied natural gas (LNG), NA-ES catalyst (a mesoporous Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalyst prepared by a single-step epoxide-driven sol-gel method) showed better LNG conversion and hydrogen yield than NA-AS catalyst (a mesoporous Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalyst prepared by a single-step alkoxide-based sol-gel method).</P> <P>[DISPLAY OMISSION]</P> <P><B>Highlights</B></P> <P>► Hydrogen was produced by steam reforming of liquefied natural gas (LNG). ► A Ni-Al<SUB>2</SUB>O<SUB>3</SUB> catalyst was prepared by an epoxide-driven sol-gel method (NA-ES). ► A Ni-Al<SUB>2</SUB>O<SUB>3</SUB> catalyst was prepared by an alkoxide-based sol-gel method (NA-AS). ► NA-ES showed higher LNG conversion and hydrogen yield than NA-AS.</P>
Bang, Yongju,Han, Seung Ju,Kwon, Soonchul,Hiremath, Vishwanath,Song, In Kyu,Seo, Jeong Gil American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.11
<P>Nano-structured alkaline-earth metal oxide adsorbents (denoted as MgO-Al2O3 and CaO-Al2O3) were prepared by an epoxide-driven one-pot sol-gel method, and they were applied to the dynamic and static CO2 adsorption. For comparison, a nano-structured aluminum oxide adsorbent (denoted as Al2O3) was also prepared by a similar method. MgO-Al2O3 adsorbent exhibited a well-developed mesopore structure through the formation of MgAl2O4 spinel phase, whereas CaO-Al2O3 adsorbent was composed of nano-sized CaO and CaAl2O4, resulting in a pore plugging. It was revealed that total basicity increased in the order of Al2O3 (0.11 mmol-CO2/g) < MgO-Al2O3 (0.37 mmol-CO2/g) < CaO-Al2O3, (1.21 mmol-CO2/g), which is in concurrent with adsorption energy obtained from DFT calculations. However, it was found that both basicity and base strength of the adsorbents played an important role in determining the CO2 adsorptive performance at different operating temperature. Among the adsorbents tested, MgO-Al2O3, which mostly retained medium basic sites, exhibited a best CO2 adsorptive performance at 200 degrees C. Furthermore, the experimental results are well supported by theoretical estimation, suggesting a useful design method of adsorbents for facile and regenerative adsorption in the applications of CO2 capture.</P>
전용주(Yongju Jeon),서정희(Jeong Hee Seo) 한국컴퓨터교육학회 2019 한국컴퓨터교육학회 학술발표대회논문집 Vol.23 No.2
정부는 지능정보사회에 적합한 인재양성을 위하여 초·중등학교에서 SW교육을 강화하고 있다. 이 노력의 일환으로 2021년까지 학교 SW교육을 주도하는 핵심교원 1만명 양성을 목표로 핵심교원 양성 연수 프로그램 개발의 필요성이 제기되었다. 2015 개정 교육과정에서 새롭게 도입된 SW교육과 관련한 내용 이해 중심의 기존 연수와의 연계성과 차별화의 맥락에서 2019년부터 학교 현장에서 구체적으로 실천될 초등 SW교육의 성공적 안착을 직접적으로 지원할 수 있는 연수 프로그램이어야 한다는 요구에 부응할 수 있는 연수프로그램의 개발이 요구되었다. 특히, SW교육 관련 전공자가 절대적으로 부족한 초등학교 현장에서는 국가교육과정을 기반으로 SW교육을 이해하고, 수업에서 이를 직접적으로 구현함과 아울러 동료 교사들과의 협력을 통한 학교 단위의 SW교육 실천을 선도할 있는 역량을 배양할 수 있는 보다 체계적이고 현장 적용성이 높은 연수프로그램을 개발하고자하였다. 본 연구에서는 초등SW교육 핵심교원 연수프로그램의 개발의 방향과 개발된 내용을 정리하였다. 이를 통해 2018년부터 2021년까지 매년 2,000명씩 전국단위로 진행할 SW교육 초등 핵심교원 연수의 보다 발전적인 모습을 탐색하고 향후 연수 결과와의 연계를 위한 기초자료를 마련하고자 한다.