147,843 research outputs found
Constant Approximation for Capacitated k-Median with (1+epsilon)-Capacity Violation
No full textWe study the Capacitated k-Median problem for which existing constant-factor approximation algorithms are all pseudo-approximations that violate either the capacities or the upper bound k on the number of open facilities. Using the natural LP relaxation for the problem, one can only hope to get the violation factor down to 2. Li [SODA'16] introduced a novel LP to go beyond the limit of 2 and gave a constant-factor approximation algorithm that opens (1 + epsilon)*k facilities.
We use the configuration LP of Li [SODA'16] to give a constant-factor approximation for the Capacitated k-Median problem in a seemingly harder configuration: we violate only the capacities by 1 + epsilon. This result settles the problem as far as pseudo-approximation algorithms are concerned
Missing-mass spectroscopy with the Li-6(pi(-), K+)X reaction to search for H-6(Lambda)
No full textWe searched for the bound state of the neutron-rich Lambda-hypernucleus H-6(Lambda), using the Li-6(pi(-), K+)X double charge-exchange reaction at a pi-beam momentum of 1.2 GeV/c at J-PARC. A total of 1.4 x 10(12) pi(-) was driven onto a Li-6 target of 3.5-g/cm(2) thickness. No event was observed below the bound threshold, i.e., the mass of H-4(Lambda) + 2n, in the missing-mass spectrum of the Li-6(pi(-), K+) X reaction in the 2 degrees < theta(pi K) < 20 degrees angular range. Furthermore, no event was found up to 2.8 MeV/c(2) above the bound threshold. We obtained the double-differential cross section spectra of the Li-6(pi(-), K+)X reaction in the angular range of 2 degrees < theta(pi K) < 14 degrees. An upper limit of 0.56 nb/sr (90% C.L.) was obtained for the production cross section of the H-6(Lambda) hypernucleus bound state. In addition, not only the bound state region, but also the Lambda continuum region and part of the Sigma(-) quasifree production region of the Li-6(pi(-), K+) reaction were obtained with high statistics. The present missing-mass spectrum will facilitate the investigation of the Sigma(-) -nucleus optical potential for Sigma(-) -He-5 through spectrum shape analysis
Isotope fractionation of alkaline and alkaline-earth elements (Li, K, Rb, Mg, Ca, Sr, Ba) during diffusion in aqueous solutions
No full textSupplementary material for Manuscript entitled: "Isotope fractionation of alkaline and alkaline-earth elements (Li, K, Rb, Mg, Ca, Sr, Ba) during diffusion in aqueous solutions"The Supplementary Materials contains:(1) Supplementary material S1, which is a full mathematical proof of the key experimental concept of this study, (2) Table S2, which tabulates the detailed instrumental setting for analyses of Li, K, Rb, Mg, Ca, Sr, Ba isotopes using Nu 1700 Sapphire MC-ICP-MS, and (3) Tables S3-1 to S3-7, which are the detailed elemental and isotopic data table of all diffusion experiments reported in this study.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Li-Ion Conduction and Stability of Perovskite Li<sub>3/8</sub>Sr<sub>7/16</sub>Hf<sub>1/4</sub>Ta<sub>3/4</sub>O<sub>3</sub>
No full textA solid
Li-ion conductor with a high room temperature Li-ion conductivity
and small interfacial resistance is required for its application in
next-generation Li-ion batteries. Here, we prepared a cubic perovskite-related
oxide with the general formula Li3/8Sr7/16Hf1/4Ta3/4O3 (LSHT) by a conventional solid-state
reaction method, which was studied by X-ray diffraction, electrochemical
impedance spectroscopy, and 7Li MAS NMR. Li3/8Sr7/16Hf1/4Ta3/4O3 has
a high Li-ion conductivity of 3.8 × 10–4 S
cm–1 at 25 °C and a low activation energy of
0.36 eV in the temperature range 298–430 K. It exhibits both
high stability and small interfacial resistance with commercial organic
liquid electrolytes, which makes it promising as a separator in Li-ion
batteries
Theoretical Study on Cyclopeptides as the Nanocarriers for Li+, Na+, K+ and F-, Cl-, Br-
No full text
The interaction process between a series of cyclopeptide compounds cyclo(Gly)(n) (n = 4, 6, 8) and monovalent ions (Li+, Na+, K+, F-, Cl-, and Br-) was studied using theoretical calculation. The mechanism of combination between the cyclo(Gly)(n) and ions was discussed through binding energy, Mulliken electron population, and hydrogen bond. It was found that for the same cyclopeptide the binding energy has the order of cyclo(Gly)(n)-Li+ > cyclo(Gly)(n)-Na+ > cyclo(Gly)(n)-K+ and cyclo(Gly)(n)-F- > cyclo(Gly)(n)-Br- > cyclo(Gly)(n)-Cl-. The binding energy manifests the stable complex of cyclo(Gly)(n) and ions can be formed, and the different energy shows the potential use of cyclo(Gly)(n) as nanocarriers for metal ions or the extractant for ions separation.</p
Quantum view of Li-ion high mobility at carbon-coated cathode interfaces
No full text: Lithium-ion batteries (LIBs) are among the most promising power sources for electric vehicles, portable electronics and smart grids. In LIBs, the cathode is a major bottleneck, with a particular reference to its low electrical conductivity and Li-ion diffusivity. The coating with carbon layers is generally employed to enhance the electrical conductivity and to protect the active material from degradation during operation. Here, we demonstrate that this layer has a primary role in the lithium diffusivity into the cathode nanoparticles. Positron is a useful quantum probe at the electroactive materials/carbon interface to sense the mobility of Li-ion. Broadband electrical spectroscopy demonstrates that only a small number of Li-ions are moving, and that their diffusion strongly depends on the type of carbon additive. Positron annihilation and broadband electrical spectroscopies are crucial complementary tools to investigate the electronic effect of the carbon phase on the cathode performance and Li-ion dynamics in electroactive materials
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Ionic conductivity and Raman spectra of Na--Li, K--Li, and K--Sn. beta. -Al/sub 2/O/sub 3/
No full textThe ionic conductivity and Raman spectra of Na, Na--Li, K, K--Li, and K--Sn ..beta..-Al/sub 2/O/sub 3/ were measured in order to understand the mechanisms of mixed-ion conduction. It was observed that at 300/sup 0/K, for example, the conductivity of a crystal with composition Na/sub 0/./sub 82/Li/sub 0/./sub 18/..beta..-Al/sub 2/O/sub 3/ was about one-fifth that of pure Na cyrstals, while the conductivity of K/sub 0/./sub 80/Li/sub 0/./sub 20/..beta..-Al/sub 2/O/sub 3/ was more than three orders of magnitude lower than that of pure K compounds. The results of a model calculation indicated that the Li/sup +/ ions are the main carrier species in the Na--Li and K--Li mixed compounds. Features observed in the Raman spectra were attributed to paired- and single-ion vibrations. It is concluded that the K/sup +/ ions which contribute to a band at 69 cm/sup -1/ in K ..beta..-Al/sub 2/O/sub 3/ are the effective carriers for conduction
Li Fang-Kuei (1902-1987)
No full textFang-Kuei Li was one of the foremost scholars of Thai and Sino-Tibetan studies and a major contributor to Amerind studies. Born in China, he was one of the early scholars sent to the United States to study. He had developed an interest in language while learning English, Latin, and German as part of his studies in China, and so he decided to study linguistics in the United States. In 1924, he went to the University of Michigan at Ann Arbor, receiving his B.A. 2 years later, then moved to the University of Chicago, where he received his M.A. and Ph.D., studying with Edward Sapir, Leonard Bloomfield, and Carl Darling Buck
The Viscosities of dry and hydrous XAlSi3O8 (X=Li, Na, K, Ca0.5, Mg0.5) melts
No full textThe low-temperature viscosities of dry and hydrous X (X=Li, Na, K, Ca0.5, Mg0.5)AlSi3O8 melts have been investigated. The samples were hydrated via piston cylinder synthesis, and the water contents were subsequently determined
by Karl-Fischer titration (KFT) and IR spectroscopy. Both the anhydrous and hydrous viscosities were measured using the
micropenetration technique in the range of viscosities between 108.5 to 1011.9 Pa s, at 1 atm pressure and in the temperature ranges of 745–990 °C and 400–790°C for the dry and wet melts, respectively. The range of water content varied for all of the
samples from 0.70 to 3.13 wt.% H2O. The viscosities of dry melts vary, at fixed temperature, as a complex function of the identity of the cation in the order Li<Na<Ca<Mg<K. This trend is interpreted as due to the combined effects of cation
field strength and (Si, Al) distribution in these melts.
With the introduction of water into these melts, the viscosity decreases for all of the compositions investigated. As water
is further dissolved, the array of anhydrous viscosities converges into two distinct curves, for alkali-bearing and
alkaline-earth-bearing aluminosilicate liquids, respectively. In contrast to the insensitivity of viscosity to alkali cation
identity for hydrous melts, the alkali-aluminium ratio remains a sensitive control on viscosity. Thus, the viscosities of a
slightly peralkaline albite glass (Naexc)are lower than all of the others, both for the dry and the hydrous systems. We suggest that, in the case of alkaline-earth-bearing melts, an aluminium pair must be closely related to a doubly charged cation, to maintain electrostatic neutrality. The increase in the size of smallest rearranging species, which participates in the viscous flow process, as well as clustering of silica-rich and alumina-rich domains on an Aintermediate-rangeB scale, may be the factors resulting in the higher viscosities of Ca- and Mg-bearing compared to alkali-bearing liquids
Thermodynamic Description of the ACl-ThCl<sub>4</sub> (A = Li, Na, K) Systems
No full textThe ACl-ThCl4 (A = Li, Na, K) systems could be of relevance to the nuclear industry in the near future. A thermodynamic investigation of the three binary systems is presented herein. The excess Gibbs energy of the liquid solutions is described using the quasi-chemical formalism in the quadruplet approximation. The phase diagram optimisations are based on the experimental data available in the literature. The thermodynamic stability of the liquid solutions increases in the order Li < Na < K, in agreement with idealised interactions and structural models
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