155,126 research outputs found
Mesophilic-hydrothermal-thermophilic (M-H-T) digestion of green corn straw
No full textMesophilic-hydrothermal (80-160 degrees C, 30 min)-thermophilic (M-H-T) digestion and control tests of mesophilic (M), thermophilic (T), hydrothermal-mesophilic (H-M), and mesophilic-thermophilic digestion (M-T) of green corn straw were conducted for a 20-day fermentation period. The results indicate that M-H-T is an efficient method to improve methane production. A maximum methane yield of 371.74 mL/g volatile solid was obtained by the M (3 days)-H (140 degrees C)-T (17 days) process, which was 20.44%, 16.55%, 31.44%, and 14.31% higher than the yields of the M, T, 140-M, and M-T processes. The enhanced methane production was attributed to (1) the improved hemicellulose degradation and lignin disorganization; (2) prevention of the degradation of soluble sugar, easily hydrolyzed hemicellulose and cellulose into furfural and methylfurfural; and (3) lack of formation of Maillard reaction products during initial hydrothermal treatment. (C) 2015 Elsevier Ltd. All rights reserved
The full gradient design in Li-rich cathode for high performance lithium ion batteries with reduced voltage decay
No full textLi-rich nickel cobalt manganese oxides (LNCM) cathode with full gradient compounds is prepared by using an ethanol assisted co-precipitation method. The rationally designed procedure involves gradient distributions of transition-metal ions, in which the Ni content increases continuously, Mn content decreases gradually and Co keeps at a low level. The employing ethanol during the synthesis adjusts the surface state to further improve the rate performance of the sample. The full gradient cathode not only provides superior cycling capacity, but also improves operating voltage and mitigates voltage decay due to the high Ni/Mn ratio of out layer with decreased Li2MnO3. The prepared material exhibits high specific capacity of 213.1 mAh g−1 after 100 cycling with voltage decay per cycle about 3.36 mV at 1 C. Even more notably, the voltage decay during cycling could still be significantly limited at high rates and capacity retention rates of 84% and 75% can be reached after 100 cycling at 2 C and 5 C, respectively. Hence, this state-of-art full gradient cathode provides an interesting model to promote a further application of LNCM
Synthesis of 2,6-Hexa-Tert-Butylterphenyl Derivatives, 2,6-(2,4,6-t-Bu₃C₆H₂)₂C₆H₃X, Where X = I, Li, OH, SH, N₃, or NH₂
Full text linkA “double benzyne” reaction between 1,3-dichloro-2-iodobenzene and 2,4,6-t-Bu₃C₆H₂MgBr followed by the addition of iodine led to 2,6-(2,4,6-t-Bu₃C₆H₂)₂C₆H₃I (HTBTI) in 65% yield. Lithiation of HTBTI with Li-t-Bu gave Li(Et₂O)₂HTBT from which HTBTSH, HTBTN₃, HTBTNH₂, and HTBTOH were prepared. An X-ray structure of W(OHTBT)₂Cl₄ shows that the two HTBTO ligands are trans to one another with the t-Bu₃C6H₂ groups on one HTBTO interdigitated with the t-Bu₃C6H₂ groups on the other HTBTO.National Institutes of Health (U.S.) (Award GM-59426
Finite-Time Event-Triggered H∞ Control for T-S Fuzzy Markov Jump Systems
Full text linkThis paper investigates the finite-time event-triggered H-infinity control problem for Takagi-Sugeno Markov jump fuzzy systems. Because of the sampling behaviors and the effect of network environment, the premise variables considered in this paper are subject to asynchronous constraints. The aim of this paper is to synthesize a controller via an event-triggered communication scheme such that not only the resulting closed-loop system is finite-time bounded and satisfies a prescribed H-infinity performance level, but also the communication burden is reduced. First, a sufficient condition is established for the finite-time bounded H-infinity performance analysis of the closed-loop fuzzy system with fully considering the asynchronous premises. Then, based on the derived condition, the method of the desired controller design is presented. Two illustrative examples are finally presented to demonstrate the practicability and efficacy of the proposed method
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
Pleurospermum tripartitum sp nov (Umbelliferae) from western Yunnan, China
No full textPleurospermum tripartitum Pu, R. Li & H. Li, a new species of Umbelliferae from western Yunnan, China, is described and illustrated. It is closely similar to P. macrochlaenum K. T. Fu & Y. C. Ho, but differs by having unbranched stem, conspicuous calyx teeth, and white petals
The Presence and Absence of Agostic Electrostatic Si−H···M Interactions in [M{Me<sub>2</sub>Si(H)N-<i>t</i>-Bu}] (M = Li, Mg<sub>1/2</sub>) Species
No full textAgostic Si−H···Li contacts (i.e.
significantly less than ∼3.0 Å) are not present in the
solvent-free X-ray structure of
[Li{Me2Si(H)N-t-Bu}]3;
shorter
(t-Bu)CH3···Li
distances (∼2.8 Å) are
observed instead. The situation in solution is different.
While the 1H−6Li HOESY
spectrum
of
[Li{Me2Si(H)N-t-Bu}]
in toluene at −80 °C evidently detects the same trimeric
species
(lacking Si−H···Li interactions, but with short
(t-Bu)CH3···Li
contacts), two major species
with strong Si−H···Li interactions also are present.
In the Li−HN−SiH3 computational
model system, Si−H···Li interactions are favored
energetically and result in increased Si−H
distances and decreased Si−H frequencies. Agostic
Si−H···metal contacts in the solid state
are found in the X-ray crystal structure of
[Mg2{Me2Si(H)N-t-Bu}4],
where Li“+” is replaced
by the more highly charged Mg“2+”. The two short
agostic Si−H···Mg interactions (2.2, 2.5
Å) which result also are shown by the two low ν(Si−H)
frequencies (2040, 1880 cm-1) in
the
IR spectrum (Nujol mull) of
[Mg2{Me2Si(H)N-t-Bu}4]
H∞ consensus and synchronization of nonlinear systems based on a novel fuzzy model
No full textThis paper investigates the H∞ consensus control problem of nonlinear multiagent systems under an arbitrary topological structure. A novel Takagi-Sukeno (T-S) fuzzy modeling method is proposed to describe the problem of nonlinear follower agents approaching a time-varying leader, i.e., the error dynamics between the follower agents and the leader, whose dynamics is evolving according to an isolated unforced nonlinear agent model, is described as a set of T-S fuzzy models. Based on the model, a leader-following consensus algorithm is designed so that, under an arbitrary network topology, all the follower agents reach consensus with the leader subject to external disturbances, preserving a guaranteed H∞ performance level. In addition, we obtain a sufficient condition for choosing the pinned nodes to make the entire multiagent network reach consensus. Moreover, the fuzzy modeling method is extended to solve the synchronization problem of nonlinear systems, and a fuzzy H∞ controller is designed so that two nonlinear systems reach synchronization with a prescribed H∞ performance level. The controller design procedure is greatly simplified by utilization of the proposed fuzzy modeling method. Finally, numerical simulations on chaotic systems and arbitrary nonlinear functions are provided to illustrate the effectiveness of the obtained theoretical results. © 2013 IEEE
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