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Optimized hard carbon derived from starch for rechargeable seawater batteries
Kim, Yongil,Kim, Jae-Kwang,Vaalma, Christoph,Bae, Geun Hyeong,Kim, Guk-Tae,Passerini, Stefano,Kim, Youngsik Elsevier 2018 Carbon Vol.129 No.-
<P><B>Abstract</B></P> <P>The recently introduced seawater battery concept is an eco-friendly energy storage system that offers appealing electrochemical performance. Its radically innovative design, compared to conventional lithium-ion batteries, makes use of seawater as an almost infinite sodium reservoir for the positive electrode and, thereby, avoids the use of expensive, scarce, and toxic elements like nickel and cobalt. So far, the problems identified mostly originate from the available negative electrode active materials. In this study, a starch-derived hard carbon was used to optimize the system. Due to its improved disordered structure compared with commercial hard carbon, the starch hard carbon exhibits an increased reversible capacity, current-rate capability, and cycling ability. The material, in fact, depicts a high maximum power density of 700 W kg<SUP>−1</SUP> (based on hard carbon weight) upon discharge at 900 mA g<SUP>−1</SUP>, while still being active at 2700 mA g<SUP>−1</SUP>. These results represent an important step toward practical application of the sodium-based seawater battery technology.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Design and construction of the GK immersed tunnel of Busan-Geoje Fixed Link Project
Yongil Kim(김용일),Woongku Kim(김웅구),Jechun Kim(김제춘),Jungsang Lee(이정상),Kyoungo Kim(김경오) 한국암반공학회 2009 터널과지하공간 Vol.19 No.2
GK침매터널은 침매터널공법으로는 국내 최초이다. 국내 시공사례의 부재, 최대 수심 약 50m에서 이루어지는 침매함체 연결 및 연약지반 등 시공상 많은 어려움에도 불구하고 현재 여덟 개의 침매함체가 성공적으로 시공되었으며 올해 안에 열 두번째 함체까지 시공될 예정이다. 본 논문의 목적은 GK 침매터널에 대한 설계 및 시공 조건을 유사 프로젝트를 수행하는 터널공학자들에게 소개하여 용이하게 프로젝트를 수행할 수 있게 하기 위함이다. The GK immersed tunnel as a part of Busan-Geoje Fixed Link Project, is the first attempt in Korea. In spite of existing of many difficulties in construction like the absent of construction cases in Korea, the connection work under approximately 50 m below sea level and weak ground condition, etc., now eight caissons were installed successfully on the accurate position and we are going to install upto the twelfth caisson in this year. The purpose of this paper is to introduce design and construction conditions of the GK immersed tunnel to advise the tunnel designers who will handle the similar project.
Na ion- Conducting Ceramic as Solid Electrolyte for Rechargeable Seawater Batteries
Kim, Yongil,Kim, Hyojin,Park, Sangmin,Seo, Inseok,Kim, Youngsik Elsevier 2016 ELECTROCHIMICA ACTA Vol.191 No.-
<P><B>Abstract</B></P> <P>This study describes the assembly of a rechargeable seawater battery using hard carbon as the anode, seawater as the cathode, and a fast Na ion-conducting ceramic as the solid electrolyte. Two different Na ion-conducting ceramics, β″-Al<SUB>2</SUB>O<SUB>3</SUB> and Na<SUB>3</SUB>Zr<SUB>2</SUB>Si<SUB>2</SUB>PO<SUB>12</SUB> (NASICON), are used as the solid electrolytes in this study. The discharge capacity of the seawater battery with the NASICON solid electrolyte is 120mAhg<SUP>−1</SUP> after the first cycle and over 91% coulombic efficiency after twenty cycles. However, under the same experimental conditions, the discharge capacity of the seawater battery with a β'-Al<SUB>2</SUB>O<SUB>3</SUB> electrolyte significantly drops to 10mAhg<SUP>−1</SUP> after one cycle. It is observed that the stability of NASICON in seawater is superior to that of β'-Al<SUB>2</SUB>O<SUB>3</SUB> and impedance results of NASICON are not changed significantly compared to that of β'-Al<SUB>2</SUB>O<SUB>3</SUB> after cycling tests. The stability of Na ion-conducting ceramics in seawater and their effects on the electrochemical performance of seawater batteries are presented and discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Rechargeable seawater batteries are assembled using two Na<SUP>+</SUP> conducting ceramics. </LI> <LI> The battery with β″-Al<SUB>2</SUB>O<SUB>3</SUB> electrolyte is irreversible even at 1 cycle. </LI> <LI> The battery with NASICON shows a coulombic efficiency of 91% after 20 cycles. </LI> <LI> NASICON is much more stable in seawater than β″-Al<SUB>2</SUB>O<SUB>3</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Bomi Kim,Hyung-Chul Lee,Seong-Hun Kim,Yongil Kim,Woosung Son,Seong Sik Kim 대한치과교정학회 2018 대한치과교정학회지 Vol.46 No.3
Objective: This study examined cone-beam computed tomography (CBCT)-derived multiplanar-reconstructed (MPR) cross-sections to clarify the salient characteristics of patients with skeletal class III malocclusion with midface deficiency (MD). Methods: The horizontal and sagittal plane intersection points were identified for middle-third facial analysis in 40 patients in the MD or normal (N) groups. MPR images acquired parallel to each horizontal plane were used for length and angular measurements. Results: A comparison of the MD and N groups revealed significant differences in the zygoma prominence among female patients. The convex zygomatic area in the N group was larger than that in the MD group, and the inferior part of the midface in the N group was smaller than that in the MD group for both male and female patients. A significant difference was observed in the concave middle maxillary area among male patients. Conclusions: This study was conducted to demonstrate the difference between MD and normal face through MPR images derived from CBCT. Male patients in the MD group had a more flattened face than did those in the N group. Female patients in the MD group showed a concave-shaped lower section of the zygoma, which tended to have more severe MD. These findings indicate that orthognathic surgery to improve skeletal discrepancy requires different approaches in male and female patients.
Bomi Kim,Hyung-Chul Lee,Seong-Hun Kim,Yongil Kim,Woosung Son,Seong Sik Kim 대한치과교정학회 2018 대한치과교정학회지 Vol.48 No.3
Objective: This study examined cone-beam computed tomography (CBCT)-derived multiplanar-reconstructed (MPR) cross-sections to clarify the salient characteristics of patients with skeletal class III malocclusion with midface deficiency (MD). Methods: The horizontal and sagittal plane intersection points were identified for middle-third facial analysis in 40 patients in the MD or normal (N) groups. MPR images acquired parallel to each horizontal plane were used for length and angular measurements. Results: A comparison of the MD and N groups revealed significant differences in the zygoma prominence among female patients. The convex zygomatic area in the N group was larger than that in the MD group, and the inferior part of the midface in the N group was smaller than that in the MD group for both male and female patients. A significant difference was observed in the concave middle maxillary area among male patients. Conclusions: This study was conducted to demonstrate the difference between MD and normal face through MPR images derived from CBCT. Male patients in the MD group had a more flattened face than did those in the N group. Female patients in the MD group showed a concave-shaped lower section of the zygoma, which tended to have more severe MD. These findings indicate that orthognathic surgery to improve skeletal discrepancy requires different approaches in male and female patients.