Search

The combination of ASA-0.4 and ASA-2 produces new acidic OH groups by increasing the contact points between silicon and aluminum. These OH groups improve the density of acid sites and increases the area of the active adsorption area of the support.

In this paper, the preparation process of low viscosity light curing silicon oxide ceramic slurry and the properties of sintered samples were studied. By studying the effects of the type and concentration of dispersant and the solid content of ceramic powder on the viscosity and stability of slurry, silicon oxide ceramic slurry with low viscosity, high solid content and good stability was prepared. The properties of sintered samples of silicon oxide ceramics were verified by the compressive strength, shrinkage test and SEM observation. The results show that with stearic acid as dispersant, the mass fraction is 2wt % and the particle size of silicon powder is 10μm. When the solid content is 45wt%, the light curing ceramic slurry with the lowest viscosity and the most stable can be obtained. After curing, degreasing and sintering, the compressive strength of the SiO2 ceramic sample prepared with the optimized parameters is 70.01 MPa, and the average shrinkage is 94.67%. It has good performance. The silicon oxide grains are arranged orderly, the structure is dense.

This paper presents an analytical solution to inverse kinematics problem of a 6-DOF robot arm based on geometric method. The solution only utilizes relations between vectors in frames attached in the robot arm. Experiments with the solution are conducted to test the approach and results show that the correctness and accuracy of the solution are verified.

Anesthetic cardioprotection reduces myocardial infarct size following ischemia-reperfusion injury. However, the underlying mechanisms that drive ischemia-reperfusion injury in cardiomyocytes remain unclear. In this study, we report that isoflurane, a commonly used inhaled anesthetic, can protect cardiomyocytes from anoxia/reoxygenation injury by a nucleotide binding oligomerization domain containing 2 (NOD2)-dependent mechanism. The results showed that isoflurane increased cell viability, and decreased autophagosome generation in primary cardiomyocytes under anoxia/reoxygenation conditions. In addition, western blot revealed that isoflurane reduces the expression of NOD2. Overexpression of NOD2 is accompanied by an increased expression of autophagy-related genes, decreased cell viability, and enhanced expression of phosphorylation p38-mitogen-activated protein kinase (p38MAPK), while NOD2 knockdown exerted the opposite effect. Following preconditioning with SB203580, a p38MAPK inhibitor, the inhibitory effect of isoflurane on cardiomyocytes autophagy was further enhanced, which suggests that p38MAPK is involved in the mechanism of cardioprotection provided by isoflurane. These findings reveal a novel mechanism underlying isoflurane-afford protection of myocardial injury.

This study presents a two-step fault diagnosis scheme combined with statistical classification and random forests-based classification for rolling element bearings. Considering the inequality of features sensitivity in different diagnosis steps, the proposed method utilizes permutation entropy and variational mode decomposition to depict vibration signals under single scale and multiscale. In the first step, the permutation entropy features on the single scale of original signals are extracted and the statistical classification model based on Chebyshev&rsquo, s inequality is constructed to detect the faults with a preliminary acquaintance of the bearing condition. In the second step, vibration signals with fault conditions are firstly decomposed into a collection of intrinsic mode functions by using variational mode decomposition and then multiscale permutation entropy features derived from each mono-component are extracted to identify the specific fault types. In order to improve the classification ability of the characteristic data, the out-of-bag estimation of random forests is firstly employed to reelect and refine the original multiscale permutation entropy features. Then the refined features are considered as the input data to train the random forests-based classification model. Finally, the condition data of bearings with different fault conditions are employed to evaluate the performance of the proposed method. The results indicate that the proposed method can effectively identify the working conditions and fault types of rolling element bearings.

Glycerol (C3H8O3), an organic waste generated by the biodiesel industry, has recently been proposed as a valuable green additive. The influence of glycerol on the morphology, composition and corrosion resistance of ZK60 magnesium alloys during the plasma electrolytic oxidation process has been investigated. The adsorption behavior of C3H8O3 molecules on Mg (002) surface has been studied by using molecular dynamics simulations. Results predict that C3H8O3 could be used as a promising leveler during the plasma electrolytic oxidation process. The silicate electrolyte with glycerol could increase the unit-area adsorptive capacity of the negative ions at the anode–electrolyte interface, and thus improves the smoothness and corrosion resistance of the coating.

The electrocardiogram signal consists in a character of smaller amplitude together with a larger interference range and the reconstructed signal, according to the classical compressed sensing theory, cannot be accurately conveyed by the signal. To solve this problem, compressed sensing based on the wavelet transform was stressed on. We carry out a compressed sensing algorithm based on wavelet transform, thus is to use the wavelet decomposition to separate the electrocardiogram, to reduce the noise pollution, to compress and reconstruct the high-frequency coefficient and to recover the signal by inversing the wavelet transform. Meanwhile, analysis on the data effect was also made. The result of the simulation shows that it obviously proves the noise suppressing effect on combining wavelet transform with compressed sensing to recover the signal. The integrity of useful information is enhanced, as well as obtaining a higher signal-to-noise ratio.

The effect of Yb3+ concentration on the fluorescence of 12CaO·7 Al2O3:Ho3+/Yb3+ polycrystals is investigated. The Raman spectra of pure C12A7 under 633-nm excitation show that the highest photon energy is 787.267 cm−1, which is not much bigger than general fluorides, so it can realize high efficiency upconversion. The upconversion emission spectra suggest that the green upconversion emission centered at 548 nm and the red upconversion emission at 662 nm correspond to the 5F4/5S2→5I8 and 5F5→5I8 transition of Ho3+ ions, respectively. The intensity of the upconversion luminescence and the ratio of red to green are changed with Yb3+ ion concentration. The pump dependence and luminescence decay dynamics spectra show the green and red upconversion emissions are populated by a two-photon process, and the upconversion mechanisms are analyzed. The relative luminous efficiencies of green and red emissions are 2.035% and 0.7%, respectively. The normalized efficiency obtained for green emission of Ho3+ at RT when the sample is excited by 980-nm light with an absorbed intensity of 7.5 W/cm2 is 0.27 cm2/W. This result is comparable to the values obtained in YF3 for the Yb3+, Er3+ green emission. The C12A7 with upconversion red and green light will be a promising luminous material.

Ir4+ ion-free 12CaO•7Al2O3 (C12A7) single crystals that were colorless and transparent have been grown by the CZ method under 0.5% oxygen-containing nitrogen atmospheres for the first time. Powder X-ray diffraction patterns and X-ray single-crystal diffraction were used to investigate the microstructure and quality of the C12A7 single crystal. The results show that the crystal was a C12A7 single crystal with tetragonal symmetry. The content of Ir4+ in the C12A7 single crystal was tested by ICP along with visible-light transmittance. There was no Ir4+ in the C12A7 crystal grown in a 0.5% oxygen-containing nitrogen atmosphere. Contents of Ir4+ in C12A7 crystal grown under 1% and 2% oxygen-containing nitrogen atmospheres were 500 ppm and 400 ppm, respectively. The microstructure of C12A7 single crystal was determined by the content of oxygen in the growth process: the occurrence of bubbles and color increase when the content of oxygen is increased. Bubbles and color decrease when the oxygen content is lowered, bubbles disappeared and the color of C12A7 turns into transparent when the content of oxygen is 0.5%, the C12A7 phase decomposed when the content of oxygen was lower than 0.5%. So, the content of oxygen was responsible for the bubbles, color and cracking, and these also can be limited by controlling the content of oxygen.

The optical properties of Er 3+ -doped and Yb 3+ /Er 3+ co-doped 12CaO·7Al 2 O 3 (C12A7) poly-crystals, synthesized by high temperature solid state method, were investigated in detail. For Er 3+ -doped and Yb 3+ /Er 3+ co-doped C12A7 poly-crystals, two main emission bands centered around 530/550 nm (green) and 660 nm (red) were observed under 980 nm diode laser excitation via an up-conversion process. The intensity of green up-conversion emission had a strong increase in Er 3+ (1.0 mol.%, 1.5 mol.%, 3.0 mol.%), and the intensity ratio of red to green up-conversion emission had an increase in Yb 3+ (1.0 mol.%, 2.0 mol.%, 10. 0 mol.%)/Er 3+ (fixed at 1.0 mol.%). This detailed study of the up-conversion processes allowed us to identify the dominant up-conversion mechanisms in Er 3+ -doped and Yb 3+ /Er 3+ co-doped C12A7 poly-crystals.

The effect of Yb 3 + concentration on the fluorescence of 12 CaO·7 Al 2 O 3 :Tm 3 + /Yb 3 + polycrystals is investigated. Under the excitation of 980 nm laser, the strong blue (477 nm) emission band is observed and attributed to 1 G 4 → 3 H 6 of Tm 3 + . The ratio of blue to red emission increases with the increasing of Yb 3 + and remains constant at 10 mol% Yb 3 + . The pump dependence and upconversion mechanisms show that the two-photon cooperative upconversion process is responsible for the enhancement of the blue upconversion emission. The Commission Internationale de l'eclairage chromaticity coordinates (x, y) illustrate that the 12 CaO·7 Al 2 O 3 :1 mol% Tm 3 + /10 mol% Yb 3 + can emit high-purity blue light.