Pushing the limit of layered transition metal oxide cathodes for high-energy density rechargeable Li ion batteries

Kim, U.-H.,Jun, D.-W.,Park, K.-J.,Zhang, Q.,Kaghazchi, P.,Aurbach, D.,Major, D. T.,Goobes, G.,Dixit, M.,Leifer, N.,Wang, C. M.,Yan, P.,Ahn, D.,Kim, K.-H.,Yoon, C. S.,Sun, Y.-K. The Royal Society of Chemistry 2018 Energy & environmental science Vol.11 No.5

<P>Development of advanced high energy density lithium ion batteries is important for promoting electromobility. Making electric vehicles attractive and competitive compared to conventional automobiles depends on the availability of reliable, safe, high power, and highly energetic batteries whose components are abundant and cost effective. Nickel rich Li[NixCoyMn1−x−y]O2 layered cathode materials (<I>x</I> > 0.5) are of interest because they can provide very high specific capacity without pushing charging potentials to levels that oxidize the electrolyte solutions. However, these cathode materials suffer from stability problems. We discovered that doping these materials with tungsten (1 mol%) remarkably increases their stability due to a partial layered to cubic (rock salt) phase transition. We demonstrate herein highly stable Li ion battery prototypes consisting of tungsten-stabilized Ni rich cathode materials (<I>x</I> > 0.9) with specific capacities >220 mA h g<SUP>-1</SUP>. This development can increase the energy density of Li ion batteries more than 30% above the state of the art without compromising durability.</P>

Sintering behavior of Y-doped ZrO₂ ceramics: the effect of additive rare earth oxides

G. Yan,H. Hui,Z. Yuan Li,L. Ying,Z. Fu Qiang 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.3

Rare earth element as colorants have been used in industry for many years. In this study, tooth-like dental ceramic has been prepared by adding rare earth oxides as colorants to nano 3Y-TZP. And the effect of Pr6O11 and CeO2 additions as dopants in yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) on the sintering densification, microstructure and transformation behavior of the composites was examined. The experimental results are discussed in terms of defect chemistry by aliovalent cation substitutions. It is found that a small amount of Pr6O11 and CeO2 additions has no significant effects on the material sintering properties, and by this means it is possible that bioceramics with a color similar to natural dentine could be developed. Rare earth element as colorants have been used in industry for many years. In this study, tooth-like dental ceramic has been prepared by adding rare earth oxides as colorants to nano 3Y-TZP. And the effect of Pr6O11 and CeO2 additions as dopants in yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) on the sintering densification, microstructure and transformation behavior of the composites was examined. The experimental results are discussed in terms of defect chemistry by aliovalent cation substitutions. It is found that a small amount of Pr6O11 and CeO2 additions has no significant effects on the material sintering properties, and by this means it is possible that bioceramics with a color similar to natural dentine could be developed.

Dissolved total hydrolyzable enantiomeric amino acids in precipitation: Implications on bacterial contributions to atmospheric organic matter

Yan, G.,Kim, G.,Kim, J.,Jeong, Y.S.,Kim, Y.I. Pergamon Press 2015 Geochimica et cosmochimica acta Vol.153 No.-

We analyzed dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and dissolved enantiomeric amino acids in precipitation samples collected at two sites in Korea over a one-year period. The average concentrations of DOC, DON, and total hydrolyzable amino acids at Seoul (an inland urban area) were lower than those at Uljin (a coastal rural area). The different bulk compositions of dissolved organic matter (DOM) at these two sites (reflected by qualitative indicators) were mainly attributed to differences in contributing sources. The d-enantiomers of four individual amino acids (aspartic acid, glutamic acid, serine, and alanine) were ubiquitously present, with average enantiomeric (d/l) ratios of 0.34, 0.26, 0.21, and 0.61 for Seoul, and 0.18, 0.11, 0.09, and 0.31 for Uljin, respectively. The much higher d/l ratios observed at Seoul than at Uljin might result from more advanced diagenetic stages as well as higher contributions from bacteria inhabiting terrestrial environments. The C- and N-normalized yields of d-alanine in DOM of our samples were found to be comparable to literature values reported for aquatic systems, where a significant portion of DOM was suggested to be of bacterial origin. Our study suggests that bacteria and their remnants might constitute an important fraction of OM in the atmosphere, contributing significantly to the quality of atmospheric OM and its post-depositional bioavailability in the surface ecosystems.

Point interpolation method based on local residual formulation using radial basis functions

G. R. Liu,L.Yan,J.G.Wang,Y.T.Gu 국제구조공학회 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.6

Dissolved organic carbon in the precipitation of Seoul, Korea: Implications for global wet depositional flux of fossil-fuel derived organic carbon

Yan, G.,Kim, G. Pergamon Press ; Elsevier [distribution] 2012 Atmospheric environment Vol.59 No.-

Precipitation was sampled in Seoul over a one-year period from 2009 to 2010 to investigate the sources and fluxes of atmospheric dissolved organic carbon (DOC). The concentrations of DOC varied from 15 μM to 780 μM, with a volume-weighted average of 94 μM. On the basis of correlation analysis using the commonly acknowledged tracers, such as vanadium, the combustion of fossil-fuels was recognized to be the dominant source. With the aid of air mass backward trajectory analyses, we concluded that the primary fraction of DOC in our precipitation samples originated locally in Korea, albeit the frequent long-range transport from eastern and northeastern China might contribute substantially. In light of the relatively invariant organic carbon to sulfur mass ratios in precipitation over Seoul and other urban regions around the world, the global magnitude of wet depositional DOC originating from fossil-fuels was calculated to be 36 +/- 10 Tg C yr<SUP>-1</SUP>. Our study further underscores the potentially significant environmental impacts that might be brought about by this anthropogenically derived component of organic carbon in the atmosphere.

Sources and fluxes of organic nitrogen in precipitation over the southern East Sea/Sea of Japan

Yan, G.,Kim, G. Copernicus GmbH 2015 Atmospheric Chemistry and Physics Vol.15 No.5

<P>Abstract. We measured total dissolved reactive nitrogen in precipitation samples collected at Uljin, a Korean coastal site upwind of the southern East Sea/Sea of Japan (EJS), selected as a representative study site of atmospheric deposition over the northwestern Pacific margin. NO3- was found to be the most abundant nitrogen species, followed by NH4+ and dissolved organic nitrogen (DON). Air-mass back-trajectory (AMBT) analysis revealed that a significant fraction of the inorganic nitrogen (NO3- and NH4+) originated from mainland Asia, whereas the DON was primarily derived from Korea. Using varimax-rotated factor analysis in combination with major ions as tracers, agricultural activities in Korea were identified as the primary sources of DON in these samples. In addition, a positive correlation was found at Uljin between the size of organic fraction in total reactive nitrogen and nitrogen to carbon atomic ratio in organic matter. This correlation has also been observed at other locations worldwide, implying the utilization potential of atmospheric organic nitrogen might increase with its proportion in total nitrogen. Combining wet deposition measurements in this study with literature values for dry deposition observed at a remote island in the EJS, the total atmospheric depositional flux of reactive nitrogen was estimated to be 115 mmol N m−2 yr−1 over the southern EJS. Our study sheds new light on the potentially significant contribution to primary productivity of the northwestern Pacific Ocean by atmospheric deposition of nitrogen, especially the organic fraction. </P>

Organic composition of carbonaceous aerosols in an aged prescribed fire plume

Yan, B.,Zheng, M.,Hu, Y. T.,Lee, S.,Kim, H. K.,Russell, A. G. Copernicus GmbH 2008 Atmospheric Chemistry and Physics Vol.8 No.21

<P>Abstract. Aged smoke from a prescribed fire (dominated by conifers) impacted Atlanta, GA on 28 February 2007 and dramatically increased hourly ambient concentrations of PM2.5 and organic carbon (OC) up to 140 and 72 μg m−3, respectively. It was estimated that over 1 million residents were exposed to the smoky air lasting from the late afternoon to midnight. To better understand the processes impacting the aging of fire plumes, a detailed chemical speciation of carbonaceous aerosols was conducted by gas chromatography/mass spectrometry (GC/MS) analysis. Ambient concentrations of many organic species (levoglucosan, resin acids, retene, n-alkanes and n-alkanoic acids) associated with wood burning emission were significantly elevated on the event day. Levoglucosan increased by a factor of 10, while hopanes, steranes, cholesterol and major polycyclic aromatic hydrocarbons (PAHs) did not show obvious increases. Strong odd over even carbon number predominance was found for n-alkanes versus even over odd predominance for n-alkanoic acids. Alteration of resin acids during transport from burning sites to monitors is suggested by the observations. Our study also suggests that large quantities of biogenic volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs) were released both as products of combustion and unburned vegetation heated by the fire. Higher leaf temperature can stimulate biogenic VOC and SVOC emissions, which enhanced formation of secondary organic aerosols (SOA) in the atmosphere. This is supported by elevated ambient concentrations of secondary organic tracers (dicarboxylic acids, 2-methyltetrols, pinonic acid and pinic acid). An approximate source profile was built for the aged fire plume to help better understand evolution of wood smoke emission and for use in source impact assessment. </P>

Measurement of the electron and ion temperatures by the x-ray imaging crystal spectrometer on joint Texas experimental tokamak

Yan, W.,Chen, Z. Y.,Jin, W.,Lee, S. G.,Shi, Y. J.,Huang, D. W.,Tong, R. H.,Wang, S. Y.,Wei, Y. N.,Ma, T. K.,Zhuang, G. American Institute of Physics 2016 Review of scientific instruments Vol.87 No.11

Significant emissions of ²¹⁰Po by coal burning into the urban atmosphere of Seoul, Korea

Yan, G.,Cho, H.M.,Lee, I.,Kim, G. Pergamon Press ; Elsevier [distribution] 2012 Atmospheric environment Vol.54 No.-

We conducted a year-round survey of precipitation samples to investigate the sources of excess <SUP>210</SUP>Po in the urban atmosphere of Seoul, Korea. The dominant fraction of <SUP>210</SUP>Po in our samples, independent of the in-situ decay of tropospheric <SUP>210</SUP>Pb, was linked with anthropogenic processes. Using vanadium and potassium as tracers, the excess <SUP>210</SUP>Po was mainly attributed to combustion of coal, with minor contributions from biomass burning. The annual integrated amount of <SUP>210</SUP>Po deposited over the Seoul area via precipitation was estimated to be 1.75 x 10<SUP>10</SUP> Bq yr<SUP>-1</SUP>, which might represent a potential public health risk in the vicinity of major point sources, due to its highly adverse biological effects. Since the world coal consumption is growing, the magnitude of coal burning derived <SUP>210</SUP>Po is expected to increase in the following decades, which should be carefully monitored.

Point interpolation method based on local residual formulation using radial basis functions

Liu, G.R.,Yan, L.,Wang, J.G.,Gu, Y.T. Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.6

A local radial point interpolation method (LRPIM) based on local residual formulation is presented and applied to solid mechanics in this paper. In LRPIM, the trial function is constructed by the radial point interpolation method (PIM) and establishes discrete equations through a local residual formulation, which can be carried out nodes by nodes. Therefore, element connectivity for trial function and background mesh for integration is not necessary. Radial PIM is used for interpolation so that singularity in polynomial PIM may be avoided. Essential boundary conditions can be imposed by a straightforward and effective manner due to its Delta properties. Moreover, the approximation quality of the radial PIM is evaluated by the surface fitting of given functions. Numerical performance for this LRPIM method is further studied through several numerical examples of solid mechanics.