Ultra-small Co nanoparticles embedded in hierarchically porous carbon were made in situ from metal–organic frameworks and used as catalysts in the Fischer–Tropsch synthesis.
Abstract Buoy-based observations of surface waves during three typhoons in the South China Sea were used to obtain the wave characteristics. With the local wind speeds kept below 35 m s −1 , the surface waves over an area with a radius 5 times that of the area in which the maximum sustained wind was found were mainly dominated by wind-wave components, and the wave energy distribution was consistent with fetch-limited waves. Swells dominated the surface waves at the front of and outside the central typhoon region. Next, the dynamics of the typhoon waves were studied numerically using a state-of-the-art third-generation wave model. Wind forcing errors made a negligible contribution to the surface wave results obtained using hindcasting. Near-realistic wind fields were constructed by correcting the idealized wind vortex using in situ observational data. If the different sets of source terms were further considered for the forcing stage of the typhoon, which was defined as the half inertial period before and after the typhoon arrival time, the best model performance had mean relative biases and root-mean-square errors of −0.7% and 0.76 m, respectively, for the significant wave height, and −3.4% and 1.115 s, respectively, for the peak wave period. Different sets of source terms for wind inputs and whitecapping breaking dissipation were also used and the results compared. Finally, twin numerical experiments were performed to investigate the importance of nonlinear wave–wave interactions on the spectrum formed. There was evidence that nonlinear wave–wave interactions efficiently transfer wave energy from high frequencies to low frequencies and prevent double-peak structures occurring in the frequency-based spectrum.
A broadband antireflective coating containing two layers of silica with different pore structures, showing excellent optical performance for solar applications.
Deformation control is a key problem to soft pneumatic actuators. The existing deformation control methods are mostly based on pressure sensors and shape detection technologies, which make soft pneumatic actuators need complex structures and fabrication processes. Based on the soft pneumatic actuator we designed actuated by electrochemical reactions on a reversible proton exchange membrane fuel cell (RPEMFC) structure, we developed a deformation control method based on reaction current. With the deformation control method, the designed soft pneumatic actuator can be accurately controlled to deform to desired angles without complex structures and control system.
The geometries and IR frequencies of uranyl complexes were calculated by B3LYP method in density functional theory (DFT) using the relative effective core potential (RECP) on uranium and 6-31+G(d) basis set on other elements. Both gaseous and aqueous phases were considered and conductor-like polarized continuum model(CPCM) was used to consider the solvation effect of water. Ligands investigated in the present paper were F-,CO230-,and NO3-. A linear correlation between the frequency of the O=U=O symmetrical stretching vibration and the number (n) of ligands was established for the above-mentioned ligands according to the following two equations:νs=-Agasn+983 and νs=-Aaqn+ 821,where Agas and Aaq are characteristic coefficients that represent the shift in vibrational frequency for the addition of each ligand to the uranyl center. Results obtained for F-fit the equations with Agas=53 cm-1 and Aaq=11 cm-1; CO230-with Agas=85 cm-1 and Aaq=19 cm-1; NO3-with Agas=48 cm-1 and Aaq=-10 cm-1. The value of Aaq was found to correspond to the experimental results.
Siloxane-based hybrid lamellar materials with ordered nanostructure units paralleling to the substrate have been widely used for water vapor barrier. However, it is very difficult to control the orientation of the lamellar units at molecular level. In this Research Article, a new lamellar bridged polysilsesquioxane (BPSQ) film, whose voids between lamellae were filled by pendant alkyl chains in the organic bridge, was prepared via the stoichiometric reaction between 3-glycidoxypropyltrimethoxysilane and aliphatic monoamine at 60 °C without catalyst. Experimental evidence obtained from FT-IR, MS, NMR, and GIXRD techniques suggested that the as-prepared BPSQ films were constructed by lamellar units with disordered orientation. Nonetheless, they possessed satisfactory water vapor barrier performance for potassium dihydrogen phosphate (KDP) and deuterated potassium dihydrogen phosphate (DKDP) optical crystals, and the water vapor transmission rate through BPSQ film with thickness of 25 μm was as low as 20.3 g·m(-2)·d(-1). Those results proved that filling the voids between molecular lamellae with alkyl chains greatly weakened the effect of lamellar unit orientation on the vapor barrier property of BPSQ film.
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