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Kim, Chanho,Park, Hyunjung,Jang, Inyoung,Kim, Sungmin,Kim, Kijung,Yoon, Heesung,Paik, Ungyu Elsevier 2018 Journal of Power Sources Vol.378 No.-
<P><B>Abstract</B></P> <P>Controlling triple phase boundary (TPB), an intersection of the ionic conductor, electronic conductor and gas phase as a major reaction site, is a key to improve cell performances for low-temperature solid oxide fuel cells. We report a synthesis of morphologically well-defined Gd<SUB>0.1</SUB>Ce<SUB>0.9</SUB>O<SUB>1.95</SUB> (GDC) embedded Ba<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>0.8</SUB>Fe<SUB>0.2</SUB>O<SUB>3-δ</SUB> (BSCF) nanofibers and their electrochemical performances as a cathode. Electrospun fibers prepared with a polymeric solution that contains crystalline Ba<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>0.8</SUB>Fe<SUB>0.2</SUB>O<SUB>3-δ</SUB> particles in ∼200 nm size and Gd(NO<SUB>3</SUB>)<SUB>3</SUB>/Ce(NO<SUB>3</SUB>)<SUB>3</SUB> precursors in an optimized weight ratio of 3 to 2 result in one dimensional structure without severe agglomeration and morphological collapse even after a high calcination at 1000 °C. As-prepared nanofibers have fast electron pathways along the axial direction of fibers, a higher surface area of 7.5 m<SUP>2</SUP> g<SUP>−1</SUP>, and more oxygen reaction sites at TPBs than those of GDC/BSCF composite particles and core-shell nanofibers. As a result, the Gd<SUB>0.1</SUB>Ce<SUB>0.9</SUB>O<SUB>1.95</SUB> embedded Ba<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>0.8</SUB>Fe<SUB>0.2</SUB>O<SUB>3-δ</SUB> nanofiber cell shows excellent performances of the maximum power density of 0.65 W cm<SUP>−2</SUP> at 550 °C and 1.02 W cm<SUP>−2</SUP> at 600 °C, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fibrous cathode of SOFC was fabricated <I>via</I> facile electrospinning method. </LI> <LI> GDC/BSCF heterogeneous structure prevents the agglomeration during sintering. </LI> <LI> Ideal morphology was proposed in terms of high TPB density and fast charge transfer. </LI> <LI> GDC/BSCF fibrous cathode shows higher activity than particulate composite. </LI> </UL> </P>
김근영,김광선,명정호,윤찬호,신우람,김철순,고영조,문성현,김경표,김태중,Kim, Keunyoung,Kim, Kwang Seon,Myung, Jungho,Yoon, Chanho,Shin, Wooram,Kim, Cheulsoon,Ko, Young Jo,Moon, Sunghyun,Kim, Kyeongpyo,Kim, Tae Joong 한국전자통신연구원 2019 전자통신동향분석 Vol.34 No.1
The capacity of wireless communications has been considered to be restricted by their fundamental limits, which were first formulated by Shannon in 1948. These limits are for the communication environment that is composed of a transmitter and receiver pair. However, there are usually more than one simultaneously communicating pairs in the environment. In such cases, the capacity is not known. Moreover, performance requirements have been diversified with the development of technology. We believe that wireless communication technologies will eventually progress toward limitless connections. Various wireless transmission and access technologies are introduced in order to overcome their limitations.
Kim, Min-Cheol,So, Jin-Young,Moon, Sang-Hyun,Han, Sang-Beom,Choi, Sojeong,Kim, Eun-Soo,Shin, Yeon-Kyung,Lee, Ji-Eun,Kwak, Da-Hee,Lee, Chanho,Bae, Won-Gyu,Park, Kyung-Won The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.20
<P>Phenomena observed in nature can be considered to be the result of optimized outcomes that have been obtained through trial and error for many years. Researchers have thus attempted to apply the lessons provided by nature to real scientific problems. In particular, in nature, the fluidic behavior of eddy currents is frequently observed, such as in a river, whereby the eddy develops into a whirlpool with an increased flow velocity, vorticity, and inner pressure. However, in this study on the design of a cathode for Li-air batteries (LABs), the eddy current of oxygen gas as a fluid can also be found in the gas diffusion layer (GDL) in the cathode fabricated using an imprinting process with micro-scale patterned metal molds. Herein, the cathode with the patterned GDL containing an increased density of carbon paper exhibits increased velocity, vorticity, and inner pressure of O2 flow due to the increased eddy current effect (the inner structuring). In addition, the patterned cathode increases the catalytic active sites for the oxygen reduction reaction due to the outer structuring effect such as an increased roughness factor. According to the simulated data from COMSOL, an average O2 gas velocity of the patterned cathode prepared through inner/outer structuring is increased by 45.8%, compared to that of the bare electrode. In the LAB test, the micro-scale patterned cathode shows an increased energy density and decreased <I>IR</I> drop by 79.6% and 23.2%, respectively. Consequently, the inner and outer structured GDL in the cathode for the ORR could be predominantly responsible for the superior LAB performance.</P>
Digital n-γ Pulse Shape Discrimination in Organic Scintillators with a High-Speed Digitizer
Kim, Chanho,Yeom, Jung-Yeol,Kim, Geehyun The Korean Association for Radiation Protection 2019 방사선방어학회지 Vol.44 No.2
Background: As neutron fields are always accompanied by gamma rays, it is essential to distinguish neutrons from gamma rays in the detection of neutrons. Neutrons and gamma rays can be separated by pulse shape discrimination (PSD) methods. Recently, we performed characterization of a stilbene scintillator detector and an EJ-301 liquid scintillator detector with a high-speed digitizer DT5730 and investigated optimized PSD variables for both detectors. This study is for providing a basis for developing fast neutron/gamma-ray dual-particle imager. Materials and Methods: We conducted PSD experiments using stilbene scintillator and EJ-301 liquid scintillator and evaluated neutron and gamma ray discriminability of each PSD method with a $^{137}Cs$ gamma source and a $^{252}Cf$ neutron source. We implemented digital signal processing techniques to apply two PSD methods - the charge comparison (CC) method and the constant time discrimination (CTD) method - to distinguish neutrons from gamma rays. We tried to find optimized PSD variables giving the best discriminability in a given experimental condition. Results and Discussion: For the stilbene scintillator detector, the charge comparison method and the constant time discrimination method both delivered the PSD FOM values of 1.7. For the EJ-301 liquid scintillator detector, both PSD methods delivered the PSD FOM values of 1.79. With the same PSD variables, PSD performance was excellent in $300{\pm}100keVee$, $500{\pm}100keVee$, and $700{\pm}100keVee$ energy regions. This result shows that we can achieve an effective discrimination of neutrons from gamma rays using these scintillator detector systems. Conclusion: We applied both PSD methods to a stilbene and a liquid scintillator and optimized the PSD performance represented by FOM values. We observed a good separation performance of both scintillators combined with a high-speed digitizer and digital PSD. These results will provide reference values for the dual-particle imager we are developing, which can image both fast neutrons and gamma rays simultaneously.