992 research outputs found
Enhanced hydrogen storage properties of LiAlH4 catalyzed by CoFe2O4 nanoparticles
The catalytic effects of CoFe2O4 nanoparticles on the hydrogen storage properties of LiAlH4 prepared by ball milling were investigated. The onset desorption temperature of the LiAlH4 + 2 mol% CoFe2O4 sample is 65 °C, which is 90 °C lower that of the as-received LiAlH4, with approximately 7.2 wt% hydrogen released at 250 °C. The isothermal desorption results show that for the 2 mol% CoFe2O4 doped sample dehydrogenated at 120 °C, 6.8 wt% of hydrogen can be released within 160 min, which is 6.1 wt% higher than that of the as-received LiAlH4 under the same conditions. Through the differential scanning calorimetry (DSC) and the Kissinger desorption kinetics analyses, the apparent activation energy, Ea, of the 2 mol% CoFe2O4 doped sample is calculated as 52.4 kJ mol -1 H2 and 86.5 kJ mol-1 H2 for the first two decomposition processes. This is 42.4 kJ mol-1 H 2 and 86.1 kJ mol-1 H2 lower compared with the pristine LiAlH4, respectively, indicating considerably improved dehydrogenation kinetics by doping the CoFe2O4 catalyst in the LiAlH4 matrix. From the Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses, a series of finely dispersed Fe and Co species with a range of valence states, produced from the reactions between LiAlH4 and CoFe2O4, play a synergistic role in remarkably improving LiAlH4 dehydrogenation properties. The rehydrogenation properties of the LiAlH4 + 2 mol% CoFe 2O4 sample have also been investigated at 140 °C under 6.5 MPa pressure held for 2.5 hPeer ReviewedPostprint (published version
Effect of Empoasca onukii Puncturing Aroma- and Taste-Active Metabolites of Qingxindamao Beauty Tea
To explore the effects of Empoasca onukii puncturing on metabolites in beauty tea produced from the cultivar Qingxindamao, sensory evaluation, ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and gas chromatography-mass spectrometry (GC-MS) were used to compare the sensory quality and metabolites of beauty tea processed from fresh tea leaves punctured or not punctured by E. onukii. The results showed that the quality of beauty tea with E. onukii puncturing was better. The contents of flavones, flavanols and their glycosides, phenolic acids, theaflavins, glycoside derivatives and tannins increased compared with beauty tea without E. onukii puncturing, while the contents of amino acids, saccharides and lipids decreased. Based on odor activity value (OAV) and partial least squares discriminant analysis (PLS-DA), a total of five characteristic volatile components, including geraniol, linalool, β-myrcene, methyl salicylate and D-limonene, were identified
A review on modelling methods, tools and service of integrated energy systems in China
An integrated energy system (IES) is responsible for aggregating various energy carriers, such as electricity, gas, heating, and cooling, with a focus on integrating these components to provide an efficient, low-carbon, and reliable energy supply. This paper aims to review the modeling methods, tools, and service modes of IES in China to evaluate opportunities for improving current practices. The models reviewed in this paper are classified as demand forecasting or energy system optimization models based on their modeling progress. Additionally, the main components involved in the IES modeling process are presented, and typical domestic tools utilized in the modeling processes are discussed. Finally, based on a review of several demonstration projects of IES, future development directions of IES are summarized as the integration of data-driven and engineering models, improvements in policies and mechanisms, the establishment of regional energy management centers, and the promotion of new energy equipment
Search for the decay
We search for radiative decays into a weakly interacting neutral
particle, namely an invisible particle, using the produced through the
process in a data sample of
decays collected by the BESIII detector
at BEPCII. No significant signal is observed. Using a modified frequentist
method, upper limits on the branching fractions are set under different
assumptions of invisible particle masses up to 1.2 . The upper limit corresponding to an invisible particle with zero mass
is 7.0 at the 90\% confidence level
Search for the reaction e+e−→χcJπ+π− and a charmoniumlike structure decaying to χcJπ± between 4.18 and 4.60 GeV
We search for the process e+e-→χcJπ+π- (J=0, 1, 2) and for a charged charmoniumlike state in the χcJπ± subsystem. The search uses datasets collected with the BESIII detector at the BEPCII storage ring at center-of-mass energies between 4.18 GeV and 4.60 GeV. No significant χcJπ+π- signals are observed at any center-of-mass energy, and thus upper limits are provided which also serve as limits for a possible charmoniumlike structure in the invariant χcJπ± mass
Observation of a structure in at from 2.05 to 3.08 GeV
The process has been studied for the
first time in detail using data sample collected with the BESIII detector at
the BEPCII collider at center of mass energies from 2.05 to 3.08 GeV. A
resonance with quantum numbers is observed with mass =
(2177.5 4.8 (stat) 19.5 (syst)) MeV/ and
width = (149.0 15.6 (stat) 8.9 (syst)) MeV with a
statistical significance larger than 10. The observed structure could
be identified with the , then the ratio of partial width between
the by BESIII and by BABAR is
( = 0.23 0.10 (stat) 0.18 (syst),
which is smaller than the prediction of the hybrid models by
several orders of magnitude
Amplitude analysis of
Utilizing the data set corresponding to an integrated luminosity of
fb collected by the BESIII detector at a center-of-mass energy of 4.178
GeV, we perform an amplitude analysis of the decay.
The sample contains 13,797 candidates with a signal purity of 80%. The
amplitude and phase of the contributing wave are measured
based on a quasi-model-independent approach, along with the amplitudes and
phases of the and waves parametrized by Breit-Wigner
models. The fit fractions of different intermediate decay channels are also
reported.Comment: 14 pages, 6 figure
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