Synthesis of full concentration gradient cathode studied by high energy X-ray diffraction

Li, Yan,Xu, Rui,Ren, Yang,Lu, Jun,Wu, Huiming,Wang, Lifen,Miller, Dean J.,Sun, Yang-Kook,Amine, Khalil,Chen, Zonghai Elsevier 2016 Nano energy Vol.19 No.-

<P><B>Abstract</B></P> <P>Nickel-rich metal oxides have been widely pursued as promising cathode materials for high energy-density lithium-ion batteries. Nickel-rich lithium transition metal oxides can deliver a high specific capacity during cycling, but can react with non-aqueous electrolytes. In this work, we have employed a full concentration gradient (FCG) design to provide a nickel-rich core to deliver high capacity and a manganese-rich outer layer to provide enhanced stability and cycle life. <I>In situ</I> high-energy X-ray diffraction was utilized to study the structural evolution of oxides during the solid-state synthesis of FCG lithium transition metal oxide with a nominal composition of LiNi<SUB>0.6</SUB>Mn<SUB>0.2</SUB>Co<SUB>0.2</SUB>O<SUB>2</SUB>. We found that both the pre-heating step and the sintering temperature were critical in controlling phase separation of the transition metal oxides and minimizing the content of Li<SUB>2</SUB>CO<SUB>3</SUB> and NiO, both of which deteriorate the electrochemical performance of the final material. The insights revealed in this work can also be utilized for the design of other nickel-rich high energy-density cathode materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Solid-state synthesis of FCG cathode is investigated by <I>in situ</I> XRD. </LI> <LI> Covariance analysis and Rietveld refinement are used to analyze the HEXRD data. </LI> <LI> Synthetic optimization of FCG cathode with excellent electrochemical performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Benefit from the covariance analysis and Rietveld refinement of <I>in situ</I> HEXRD data during the solid state synthesis, we can optimized the solid state synthesis conditions in a short time. And the full concentration gradient cathode composites (nickel-rich core and manganese-rich outer layer) with excellent electrochemical performance are obtained.</P> <P>[DISPLAY OMISSION]</P>

J-Sim: a simulation and emulation environment for wireless sensor networks

Sobeih, A.,Hou, J.C.,Lu-Chuan Kung,Ning Li,Honghai Zhang,Wei-Peng Chen,Hung-Ying Tyan,Hyuk Lim IEEE 2006 IEEE wireless communications Vol.13 No.4

<P>Wireless sensor networks have gained considerable attention in the past few years. They have found application domains in battlefield communication, homeland security, pollution sensing, and traffic monitoring. As such, there has been an increasing need to define and develop simulation frameworks for carrying out high-fidelity WSN simulation. In this article we present a modeling, simulation, and emulation framework for WSNs in J-Sim - an open source, component-based compositional network simulation environment developed entirely in Java. This framework is built on the autonomous component architecture and extensible internetworking framework of J-Sim, and provides an object-oriented definition of target, sensor, and sink nodes, sensor and wireless communication channels, and physical media such as seismic channels, mobility models, and power models (both energy-producing and energy-consuming components). Application-specific models can be defined by subclassing classes in the simulation framework and customizing their behaviors. We also include in J-Sim a set of classes and mechanisms to realize network emulation. We demonstrate the use of the proposed WSN simulation framework by implementing several well-known localization, geographic routing, and directed diffusion protocols, and perform performance comparisons (in terms of the execution time incurred and memory used) in simulating WSN scenarios in J-Sim and ns-2. The simulation study indicates the WSN framework in J-Sim is much more scalable than ns-2 (especially in memory usage). We also demonstrate the use of the WSN framework in carrying out real-life full-fledged Future Combat System (FCS) simulation and emulation</P>

수험생활 중 경주 및 포항 지진 경험

김선주,김유영,김은주,박솔민,배지윤,이민영,이유진,정재원,Li Keying,Wuyingjinzhu,신수진,도지영 이화여자대학교 간호과학대학 2019 이화간호학회지 Vol.- No.53

Purpose: The purpose of this study was to understand the experiences of Gyeongju and Pohang earthquakes during the examinees’ life. Methods: This study applied Colaizzis’s Phenomenological method. The Data was collected through in-depth interviews with a total 8 students of university in Seoul. Results: On the analysis of the interviews, their experience can be expressed as ‘Feeling embarrassed and frightened by earthquakes’, ‘Reduced susceptibility to earthquake hazards due to heavy exam pressure’, ‘Increased exam stress due to earthquake’, ‘Feeling the inadequacy of examinees' earthquake related safety measures in retrospect’. Conclusion: This study was meaningful in deeply understanding of their experiences and revealing that the examinees were more focused on studying rather than actively coping with the disaster. Furthermore, it reconsider the social climate surrounding college admission exams. This study meaningfully discovered that examinees could not stably prepare for both the exam and the earthquake evacuation procedures due to the timing of the earthquake in relation to their upcoming college admission test. Therefore, this study highlighted the examinees’ difficulties due to the earthquakes and increased the necessity of acute phase nursing intervention in relation to the seismic safety education system.

SEARCHES FOR MILLISECOND PULSAR CANDIDATES AMONG THE UNIDENTIFIED<i>FERMI</i>OBJECTS

Hui, C. Y.,Park, S. M.,Hu, C. P.,Lin, L. C. C.,Li, K. L.,Kong, A. K. H.,Tam, P. H. T.,Takata, J.,Cheng, K. S.,Jin, Ruolan,Yen, T.-C.,Kim, Chunglee IOP Publishing 2015 The Astrophysical journal Vol.809 No.1

<P>Here we report the results of searching millisecond pulsar (MSP) candidates from the Fermi LAT second source catalog (2FGL). Seven unassociated gamma-ray sources in this catalog are identified as promising MSP candidates based on their gamma-ray properties. Through the X-ray analysis, we have detected possible X-ray counterparts, localized to an arcsecond accuracy. We have systematically estimated their X-ray fluxes and compared them with the corresponding gamma-ray fluxes. The X-ray to gamma-ray flux ratios for 2FGL J1653.6-0159 and 2FGL J1946.4-5402 are comparable with the typical value for pulsars. For 2FGL J1625.2-0020, 2FGL J1653.6-0159, and 2FGL J1946.4-5402, their candidate X-ray counterparts are bright enough to perform a detailed spectral and temporal analysis to discriminate their thermal/non-thermal nature and search for the periodic signal. We have also searched for possible optical/IR counterparts at the X-ray positions. For the optical/IR source coincident with the brightest X-ray object associated with 2FGL J1120.0-2204, its spectral energy distribution is comparable with a late-type star. Evidence for the variability has also been found by examining its optical light curve. All the aforementioned 2FGL sources resemble a pulsar in one or more aspects, making them promising targets for follow-up investigations.</P>

Electrolyte effect on the catalytic performance of Ni-based catalysts for direct internal reforming molten carbonate fuel cell

Li, Z.,Devianto, H.,Yoon, S.P.,Han, J.,Lim, T.H.,Lee, H.I. Pergamon Press ; Elsevier Science Ltd 2010 International journal of hydrogen energy Vol.35 No.23

An active and tolerant Ni-based catalyst for methane steam reforming in direct internal reforming molten carbonate fuel cells (DIR-MCFCs) was developed. Deactivation of reforming catalysts by alkali metals from the electrolyte composed of Li<SUB>2</SUB>CO<SUB>3</SUB> and K<SUB>2</SUB>CO<SUB>3</SUB> is one of the major obstacles to be overcome in commercialization of DIR-MCFCs. Newly developed Ni/MgSiO<SUB>3</SUB> and Ni/Mg<SUB>2</SUB>SiO<SUB>4</SUB> reforming catalysts show activities of ca. 80% methane conversion. Subsequent to electrolyte addition to the catalyst, however, the activity of Ni/Mg<SUB>2</SUB>SiO<SUB>4</SUB> decreases to ca. 50% of its initial value, whereas Ni/MgSiO<SUB>3</SUB> catalyst retains its initial activity. Results obtained from temperature-programmed reduction and X-ray photoelectron spectroscopy identify unreduced Ni<SUP>3+</SUP> as a decisive factor in keeping catalytic activity from the electrolyte.

The X-Ray Modulation of PSR J2032+4127/MT91 213 during the Periastron Passage in 2017

Li, K. L.,Takata, J.,Ng, C. W.,Kong, A. K. H.,Tam, P. H. T.,Hui, C. Y.,Cheng, K. S. American Astronomical Society 2018 The Astrophysical journal Vol.857 No.2

유형별 완전혼합사료 급여가 반추위내의 발효성상 및 영양소 소화율에 미치는 영향

이덕윤,고종렬,최낙진,이상석,송재용,이세영,박성호,성하균,하종규 한국동물자원과학회 2003 한국축산학회지 Vol.45 No.5

This study was conducted to examine effects of feeding dry TMR(DTMR), wet TMR(WTMR) and fermented TMR(FTMR) on rumen fermentation, enzyme activity and digestibility in the total tract of sheep. Three rumen cannulated sheep were used in a 3 × 3 latin square design. The present results showed that ?, NH_(3)-N, total and individual VFA, A/P ratio and enzymes (CMCase, Xylanase and Protease) activity in the rumen were higher in WTMR and FTMR compared with DTMR. In addition, dry matter, organic matter, crude protein, ether extract, NDF and ADF digestibility in the total tract were also higher in WTMR and FTMR compared with DTMR. Therefore, the present results showed that WTMR and FTMr are better than DTMR for rumen fermentation and nutrients digestibility.

Tailoring the defects and carrier density for beyond 10% efficient CZTSe thin film solar cells

Li, J.,Kim, S.,Nam, D.,Liu, X.,Kim, J.,Cheong, H.,Liu, W.,Li, H.,Sun, Y.,Zhang, Y. North-Holland ; Elsevier Science Ltd 2017 Solar energy materials and solar cells Vol.159 No.-

The defects states and carrier density of CZTSe absorber layers are two of the crucial factors that decide the photovoltaic performance of CZTSe thin film solar cells. Fine tailoring the defects and carrier density is a key to push the power conversion efficiency of CZTSe solar cells to a more competitive level. In this work, the phase properties, defect states, and carrier density of CZTSe thin film are well controlled by fine tuning the ratio of Zn/Sn in the range from 0.75 to 1.27. Capacity-Voltage measurements and Admittance Spectroscopy are used to characterize the carrier density, depletion region width, and defect states of the CZTSe solar cells. The results indicate that the defects states and carrier density of CZTSe layer are very sensitive to the ratio of Zn/Sn. Combining experimental results and numerical simulation, the statistic regularities of the photovoltaic parameters of the CZTSe solar cells with different ratios of Zn/Sn is well explained. The increase of V<SUB>OC</SUB> of CZTSe solar cells with the ratio of Zn/Sn is related to both the increased carrier density and the decreased deep level defects states. The decline of J<SUB>SC</SUB> of the Zn-rich solar cells is caused by both the shrunken depletion region width and a large barrier caused by ZnSe phase. This barrier is the cause for a low fill factor in the Zn-rich solar cells. Overall, the CZTSe solar cells with a stoichiometric ratio of Zn/Sn=1.02 have favorable defects property and carrier density, thus resulting in the highest photovoltaic efficiency of 10.21%.

<i>Swift</i>,<i>XMM</i>-<i>Newton</i>, and<i>NuSTAR</i>Observations of PSR J2032+4127/MT91 213

Li, K. L.,Kong, A. K. H.,Tam, P. H. T.,Hou, X.,Takata, J.,Hui, and C. Y. American Astronomical Society 2017 The Astrophysical journal Vol.843 No.2

<P>We report our recent Swift, NuSTAR, and XMM-Newton X-ray and Lijiang optical observations on PSR J2032 + 4127/MT91 213, the gamma-ray binary candidate with a period of 45-50 years. The coming periastron of the system was predicted to be in 2017 November, around which high-energy flares from keV to TeV are expected. Recent studies with Chandra and Swift X-ray observations taken in 2015/2016 showed that its X-ray emission has been brighter by a factors of similar to 10 than that before 2013, probably revealing some ongoing activities between the pulsar wind and the stellar wind. Our new Swift/XRT lightcurve shows no strong evidence of a single vigorous brightening trend, but rather several strong X-ray flares on weekly to monthly timescales with a slowly brightening baseline, namely the low state. The NuSTAR and XMM-Newton observations taken during the flaring and the low states, respectively, show a denser environment and a softer power-law index during the flaring state, implying that the pulsar wind interacted with the stronger stellar winds of the companion to produce the flares. These precursors would be crucial in studying the predicted giant outburst from this extreme gamma-ray binary during the periastron passage in late 2017.</P>

하이브리드 다층 인쇄회로기판의 굽힘 강도 개선에 관한 해석 및 실험적 연구

Le Li,김상목(S.M. Kim),송승호(S.H. Song),구태완(T.W. Ku),송우진(W.J. Song),김정(J. Kim),강범수(B.S. Kang) 한국정밀공학회 2007 한국정밀공학회 학술발표대회 논문집 Vol.2007 No.11월