1,130 research outputs found
Theoretical model for the analysis of rotational behavior of penetrated mortise-tenon joints in traditional timber structures
Pd/CeO2/SiC Chemical Sensors
The incorporation of nanostructured interfacial layers of CeO2 has been proposed to enhance the performances of Pd/SiC Schottky diodes used to sense hydrogen and hydrocarbons at high temperatures. If successful, this development could prove beneficial in numerous applications in which there are requirements to sense hydrogen and hydrocarbons at high temperatures: examples include monitoring of exhaust gases from engines and detecting fires. Sensitivity and thermal stability are major considerations affecting the development of high-temperature chemical sensors. In the case of a metal/SiC Schottky diode for a number of metals, the SiC becomes more chemically active in the presence of the thin metal film on the SiC surface at high temperature. This increase in chemical reactivity causes changes in chemical composition and structure of the metal/SiC interface. The practical effect of the changes is to alter the electronic and other properties of the device in such a manner as to degrade its performance as a chemical sensor. To delay or prevent these changes, it is necessary to limit operation to a temperature <450 C for these sensor structures. The present proposal to incorporate interfacial CeO2 films is based partly on the observation that nanostructured materials in general have potentially useful electrical properties, including an ability to enhance the transfer of electrons. In particular, nanostructured CeO2, that is CeO2 with nanosized grains, has shown promise for incorporation into hightemperature electronic devices. Nanostructured CeO2 films can be formed on SiC and have been shown to exhibit high thermal stability on SiC, characterized by the ability to withstand temperatures somewhat greater than 700 C for limited times. The exchanges of oxygen between CeO2 and SiC prevent the formation of carbon and other chemical species that are unfavorable for operation of a SiC-based Schottky diode as a chemical sensor. Consequently, it is anticipated that in a Pd/CeO2/SiC Schottky diode, the nanostructured interfacial CeO2 layer would contribute to thermal stability and, by contributing to transfer of electrons, would also contribute to sensitivity
Vibronic fine structure in the nitrogen 1s photoelectron spectra from Franck-Condon simulations II: Indoles
The vibronic coupling effect in nitrogen 1s X-ray photoelectron spectra (XPS)
was systematically studied for a family of 17 bicyclic indole molecules by
combining Franck-Condon simulations (including the Duschinsky rotation effect)
and density functional theory. The simulated vibrationally-resolved spectra of
4 molecules agree well with available experiments. Reliable predictions for
this family further allowed us to summarize rules for spectral evolution in
response to three types of common structural changes (side chain substitution,
CHN replacement, and isomerization). Interestingly, vibronic
properties of amine and imine nitrogen are clearly separated: they show
negative and positive ZPE (zero-point vibration energy of the
core-ionized with respect to the ground state), respectively, indicating
flatter and steeper PESs induced by the N 1s ionization; amine N's show
stronger mode mixing effects than imine N's; the 1s ionizations on two types of
nitrogens led to distinct changes in local bond lengths and angles. The rules
are useful for a basic understanding of vibronic coupling in this family, and
the precise spectra are useful for future reference and data mining studies
Vibrationally-resolved X-ray spectra of diatomic systems: Time-independent and time-dependent simulations
We systematically investigated vibronic coupling effects in X-ray spectra of
diatomic systems using time-independent (TI) and time-dependent (TD) methods.
Under the TI framework, we studied 5 systems (N, N, NO, CO,
CO) in their lowest C/N/O 1s excited or ionized states, generating 10 X-ray
absorption (XAS) or photoelectron (XPS) spectra using density functional theory
(DFT) with two pure (BLYP, BP86) and two hybrid (B3LYP, M06-2X) functionals.
Excellent agreement between theoretical and experimental spectra was found in
most systems, except that in O1s XAS of CO and NO, intensities of
higher-energy peaks were underestimated. We established a connection between
their complex vibronic structures and the significant geometrical changes
induced by the O1s hole. Functional dependence in diatomic systems is generally
more pronounced than in polyatomic ones. In all examined cases, pure
functionals exhibit better or similar spectral accuracy to hybrid functionals,
attributed to superior prediction accuracy in bond lengths and vibrational
frequencies. With the TD wavepacket method, we simulated vibrationally-resolved
XAS of CO, NO, and CO using potential energy curves (PECs) generated at
both DFT and multiconfigurational levels. Both TD and TI generate similar C/O
1s XAS spectra of CO. For O1s XAS of NO and CO, TD calculations
significantly improved the corresponding TI results, demonstrating sensitivity
to the anharmonic effect and the PEC quality. TI and TD approaches are
complementary, with practical applications depending on the ease and accuracy
of excited-state geometry optimization or PEC scanning, and the significance of
anharmonicity. DFT with pure functionals is recommended for diatomic
calculations due to its easy execution and reliable accuracy. TI is optimal for
most scenarios, but TD is needed for problems with strong anharmonic effects.Comment: 11 figure
EFFECTS OF SHOE COLLAR HEIGHT ON SAGITTAL ANKLE ROM, KINETICS AND POWER OUTPUT DURING SINGLE-LEG AND DOUBLE-LEG JUMPS
The aim of this research was to examine the effects of high-top shoes and low-top shoes on sagittal ankle ROM, kinetics and power output during single-leg and double-leg jumps. Twelve male subjects were requested to wear high-top and low-top shoes to perform single-leg and double-leg jumps. Ankle joint kinematics and kinetics data were collected using Vicon system and force plates. Shoe collar heights did not influence the jump height in both single-leg and double-leg jump tasks. However, high-top shoes adopted in this study resulted in a significant smaller sagittal ankle ROM during a quasi-static movement. In addition, wearing high-top shoe could also decrease the dorsiflexion ankle joint torque and power output during the push-off phase in single-leg jump. These findings provide preliminary evidence suggesting that a changed ankle kinematic and kinetic behaviour in the sagittal plane may be induced when wearing high-top shoes
Editorial: Structure and mechanical properties of titanium alloys and Titanium Matrix Composites (TMCs)
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