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Youngkwon Ryu,Iickho Song,Taejoo Chang,Suk Chan Kim 한국정보과학회 1996 Journal of Electrical Engineering and Information Vol.1 No.1
Adaptive code rate change schemes in DS-SSMA systems are proposed. In the proposed schemes, the error correcting code rate is changed according to the channel states, Two channel stales having significant effects on the bit error probability are considered: one is the effective number of users, and the other is the fading environment. These channel states are estimated based on retransmission requests. The criterion for the change of the code rate is to maximize the throughput under given error bound.
Acid mine drainage treatment by integrated submerged membrane distillation–sorption system
Ryu, Seongchul,Naidu, Gayathri,Hasan Johir, Md Abu,Choi, Youngkwon,Jeong, Sanghyun,Vigneswaran, Saravanamuthu Elsevier 2019 CHEMOSPHERE - Vol.218 No.-
<P><B>Abstract</B></P> <P>Acid mine drainage (AMD), an acidic effluent characterized by high concentrations of sulfate and heavy metals, is an environmental and economic concern. The performance of an integrated submerged direct contact membrane distillation (DCMD) – zeolite sorption system for AMD treatment was evaluated. The results showed that modified (heat treated) zeolite achieved 26–30% higher removal of heavy metals compared to natural untreated zeolite. Heavy metal sorption by heat treated zeolite followed the order of Fe > Al > Zn > Cu > Ni and the data fitted well to Langmuir and pseudo second order kinetics model. Slight pH adjustment from 2 to 4 significantly increased Fe and Al removal rate (close to 100%) due to a combination of sorption and partial precipitation. An integrated system of submerged DCMD with zeolite for AMD treatment enabled to achieve 50% water recovery in 30 h. The integrated system provided a favourable condition for zeolite to be used in powder form with full contact time. Likewise, heavy metal removal from AMD by zeolite, specifically Fe and Al, mitigated membrane fouling on the surface of the hollow fiber submerged membrane. The integrated system produced high quality fresh water while concentrating sulfuric acid and valuable heavy metals (Cu, Zn and Ni).</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
A critical review on remediation, reuse, and resource recovery from acid mine drainage
Naidu, Gayathri,Ryu, Seongchul,Thiruvenkatachari, Ramesh,Choi, Youngkwon,Jeong, Sanghyun,Vigneswaran, Saravanamuthu Elsevier Applied Science Publishers 2019 Environmental pollution Vol.247 No.-
<P><B>Abstract</B></P> <P>Acid mine drainage (AMD) is a global environmental issue. Conventionally, a number of active and passive remediation approaches are applied to treat and manage AMD. Case studies on remediation approaches applied in actual mining sites such as lime neutralization, bioremediation, wetlands and permeable reactive barriers provide an outlook on actual long-term implications of AMD remediation. Hence, in spite of available remediation approaches, AMD treatment remains a challenge. The need for sustainable AMD treatment approaches has led to much focus on water reuse and resource recovery. This review underscores (i) characteristics and implication of AMD, (ii) remediation approaches in mining sites, (iii) alternative treatment technologies for water reuse, and (iv) resource recovery. Specifically, the role of membrane processes and alternative treatment technologies to produce water for reuse from AMD is highlighted. Although membrane processes are favorable for water reuse, they cannot achieve resource recovery, specifically selective valuable metal recovery. The approach of integrated membrane and conventional treatment processes are especially promising for attaining both water reuse and recovery of resources such as sulfuric acid, metals and rare earth elements. Overall, this review provides insights in establishing reuse and resource recovery as the holistic approach towards sustainable AMD treatment. Finally, integrated technologies that deserve in depth future exploration is highlighted.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Acid mine drainage (AMD) is a global environmental and economic challenge. </LI> <LI> Current AMD remediation applied at real sites and its limitations are highlighted. </LI> <LI> AMD challenges must be addressed through sustainable treatment approaches. </LI> <LI> Water reuse and valuable resource recovery potentially offset AMD treatment cost. </LI> <LI> Integrated processes using membranes are prospective approaches for AMD treatment. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Ku, Kang Hee,Ryu, Ji Ho,Kim, Jinwoo,Yun, Hongseok,Nam, Chongyong,Shin, Jae Man,Kim, Youngkwon,Jang, Se Gyu,Lee, Won Bo,Kim, Bumjoon J. American Chemical Society 2018 Chemistry of materials Vol.30 No.23
<P>Interface engineering of evaporative emulsion droplets containing block copolymers (BCPs) provides an effective route to generate nonspherical particles. Here, we demonstrate the impact of length-controlled nanorods (NRs) on the interfacial properties of BCP emulsions to produce anisotropic BCP particles. A series of lamellae- and cylinder-forming polystyrene-<I>b</I>-poly(4-vinylpyridine) (PS-<I>b</I>-P4VP) and a series of NRs with different lengths (<I>l</I>) are coassembled, and selective arrangement of the NRs on the P4VP domain at the particle surface enables the production of striped football (prolate) and convex lens-shaped (oblate) particles. In particular, the ratio of the NR length to the size of the NR-hosting domain (<I>l</I>/<I>L</I>), which is varied from 0.07 to 3.60, is the key parameter in determining the location of the NRs in the BCP particles as well as the final particle shape. The oblate particles are generated only in the range of 0.36 ≤ <I>l</I>/<I>L</I> ≤ 0.96, whereas the prolate particles are produced for much wider range of <I>l</I>/<I>L</I> ≥ 0.83 without upper limit. This difference is attributed to larger entropic penalty for the NRs confined within the P4VP cylinders than the entropic penalty for those within the lamellae. To better understand and support our experimental observations, we performed dissipative particle dynamics simulation and calculated the free energy for the NR/BCP assembly within the emulsion droplets.</P> [FIG OMISSION]</BR>
Kim, Hyeong Jun,Kim, Jae-Han,Ryu, Ji-Ho,Kim, Youngkwon,Kang, Hyunbum,Lee, Won Bo,Kim, Taek-Soo,Kim, Bumjoon J. American Chemical Society 2014 ACS NANO Vol.8 No.10
<P>While most high-efficiency polymer solar cells (PSCs) are made of bulk heterojunction (BHJ) blends of conjugated polymers and fullerene derivatives, they have a significant morphological instability issue against mechanical and thermal stress. Herein, we developed an architecturally engineered compatibilizer, poly(3-hexylthiophene)-<I>graft</I>-poly(2-vinylpyridine) (P3HT-<I>g</I>-P2VP), that effectively modifies the sharp interface of a BHJ layer composed of a P3HT donor and various fullerene acceptors, resulting in a dramatic enhancement of mechanical and thermal stabilities. We directly measured the mechanical properties of active layer thin films without a supporting substrate by floating a thin film on water, and the enhancement of mechanical stability without loss of the electronic functions of PSCs was successfully demonstrated. Supramolecular interactions between the P2VP of the P3HT-<I>g</I>-P2VP polymers and the fullerenes generated their universal use as compatibilizers regardless of the type of fullerene acceptors, including mono- and bis-adduct fullerenes, while maintaining their high device efficiency. Most importantly, the P3HT-<I>g</I>-P2VP copolymer had better compatibilizing efficiency than linear type P3HT-<I>b</I>-P2VP with much enhanced mechanical and thermal stabilities. The graft architecture promotes preferential segregation at the interface, resulting in broader interfacial width and lower interfacial tension as supported by molecular dynamics simulations.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-10/nn503823z/production/images/medium/nn-2014-03823z_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn503823z'>ACS Electronic Supporting Info</A></P>