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A kind of multiscale β-sialon grain-reinforced Al2O3 matrix composite ceramic tool material, named ASN, was prepared and studied. For the ASN, β-sialon (molecular formula: Si4Al2O2N6) was synthesized in situ by a hot-pressing and solid-solution reaction process. A total of six samples were prepared at varying sintering temperatures and holding times under vacuum conditions. The solid solution reaction mechanism of β-sialon, the phase composition, mechanical properties, microstructure, and strengthening and toughening mechanisms of the composite ASN were investigated. As a result, within the experimental parameters, an optimal ASN tool material was obtained under a pressure of 32 MPa and at a temperature of 1550 °C for 20 min. The tested mechanical properties of the optimal sample were as follows: flexural strength 997 ± 59 MPa, fracture toughness 6.4 ± 0.3 MPa·m1/2, Vickers hardness 18.2 ± 0.4 GPa, and relative density 98.1 ± 0.2%. According to crystal defect theory, the solid solution reaction mechanism of in-situ-synthesized β-sialon in an Al2O3 matrix involves a double mechanism of unequivalence (or hetero-valence) and interstitial filling. The multiscale β-sialon grains mainly consisted of four grains, which were elongated β-sialon grains with a diameter of 0.3–0.4 μm and an aspect ratio of 6–9, elongated β-sialon grains with a diameter of 70 nm and an aspect ratio of 10, β-sialon whiskers with a diameter of 0.2 μm and an aspect ratio of 12–15, and intragranular β-sialon whiskers with a diameter of 70 nm. The mechanical properties were improved due to strengthening and toughening mechanisms, such as mixed structure mode (intergranular and transgranular), elongated grain pullout, interface bonding, crack reflection, pinning, and bridging.

The metastable zone widths of ammonium sulphate in aqueous solution during cooling crystallization were predicted by modifying of the nucleation potential model in an electrolyte system.

Novel lignin/paraffin/epoxy resin composite coated urea (LPECCU) was successfully prepared. Paraffin and epoxy resin (ER) were used to improve the slow-release properties of the lignin-based polyurethane (LPU) coated urea. The relationships among the N release characteristics, liquid-solid rate, -CNO/-OH molar rate and film formation rate in the coating material of LPECCU were investigated. The results showed that the water contact angle (WCA) of the LPU-paraffin increased with the rate of liquid-solid rate (73.61-88.19°) and -CNO/-OH molar rate (65.17-82.24°) increased. The average particle hardness of LPECCU decreased with the increased of liquid-solid rate (57.10-66.80 N) and the reduced of -CNO/-OH molar rate (48.11-63.00 N). The LPECCU emerged compact micro-structure, low sustained release and high compressive resistance by adding paraffin and ER. The coating material of LPECCU appeared excellent biodegradability in the soil. The optimal N cumulative release rate (72.49 %) of LPECCU was obtained (liquid-solid rate of 1.43, -CNO/-OH molar rate of 2, and the film formation rate of 6.66 %). The lettuce growth study was conducted to further evaluate the pot application of the LPECCU. In comparison to conventional urea, LPECCU could improve the total dry matter accumulation and N use efficiency of the lettuce.

Background: Currently, there are few reports about the sustained-release time of single-layer non-modified lignin-based coated urea that meets the sustained-release standard. Therefore, the unmodified lignin-based material by adding a hydrophobic polymer can improve the hydrophobicity of the coating material.Results: A novel green double layer coating with lignin-based polyurethane (LPU) as the inner coating and epoxy resin (EP) as the outer coating was effectively constructed for coated urea. Fourier transform infrared spectra confirmed that lignin and polycaprolactone diol successfully reacted with Hexamethylene diisocyanate. The loss weight and water contact angle (WCA, 75.6-63.6°) of the LPUs decreased with the increased lignin content. The average particle hardness of the LDCU first increased from 58.1 N (lignin of 30%) to 67.0 N (lignin of 60%), but then decreased to 62.3 N (lignin of 70%). The release longevity of the coated urea was closely related to the preparation parameters of the coating material. The optimal cumulative nutrient release rate (79.4%) of LDCU was obtained (lignin of 50%, -CNO/-OH molar ratios of 1.15, EP of 35%, and coating ratio of 5%). The aggregates of hydrone on the LDCU caused the dissolution and swelling of nutrients, and then the diffusion of nutrients through the concentration gradient. Conclusion: Although the nutrient release of the LDCUs was affected by many factors, the successful development of the LDCUs will improve the rapid development of the coated fertilizer industry.

The purpose of this work is to investigate the effect of the WC content on the surface characteristics and nanoindentation behaviors of WC/Ni-based composite laser-clad coatings. Four NiCrSiBC coatings with WC wt% of 30%, 40%, 50%, and 60%, respectively, were clad on carbon steel substrates using a laser. The morphologies and phase compositions of four clad coatings were comparatively observed. In addition, the hardness and elastic modulus values of the four coatings were measured and quantitatively calculated. As a result, with the increase in WC, the coating grains were more refined. Meanwhile, cracks and WC particle breakage occurred in the 50–60% WC coatings, whereas this was not found in the 30–40% WC coatings. When the WC content increased from 40% up to 50%, the coating hardness and elastic modulus significantly increased. However, a further increase in WC from 50% to 60% did not result in considerable improvement in coating quality but considerably worsened the coating’s cracking behavior instead. Therefore, for WC/Ni-based composite coatings, a threshold exists for the WC content, and this value was 50% within the experimental scope of this study.

BACKGROUND Sepsis is one of the most common critical illnesses in intensive care unit (ICU) clinical practice. Intravenous infusion technology is an important method for life support. The commonly used deep vein indwelling is expensive, and the incidence of infection due to long-term placement is high. Ultrasound technology can guide clinical puncture operations in real time and greatly improve the success rate of puncture. In the present study, we aimed to explore the effect of ultrasound-guided external jugular vein puncture and catheterization in patients with sepsis. METHODS From December 2018 to December 2019, a total of 61 patients with sepsis from the ICU or neurology care unit (NCU) were included in the present study and were randomly divided into the experimental group (n=30) and control group (n=31). Ultrasound-guided indwelling cannula needle was used in the experimental group, and blind indwelling cannula needle was used in the control group. The success rate of puncture at first operation, indwelling complications (e.g., bleeding, redness, infection, poor infusion), and operation time of the 2 methods were compared. RESULTS A comparison of the patients in the control group with the experimental group indicated no significant differences in age, body mass index, sex, temperature, mean aortic pressure, sequential organ failure score, need for vasopressors, central venous pressure, leucocytes, hemoglobin, platelets, albumin, and mechanical ventilation (all P>0.05). The duration of ICU or NCU stay was 5 days in the experimental group compared with 7 days in the control group (P=0.009). Compared with the control group, the experimental group had shorter successful puncture time (4.0 vs. 6.0 min, P

Mechanical design is an important course combined with theory and practice. Usually, the course design is arranged after the theory course to train the ability of the machine design. The practice content of course design can be reasonably separated according to the theory knowledge of the relevant chapter. In the reform process, the course specific chapter and the content of the design example are combined and studied. By means of detailing and early studying the design practicing content, student can know the purpose and significance of studying after the part of course studying. In the paper, the measures are also put forward in response to the problems during the reform implementation.

An economical and facile method for high-yield production of cobalt and nitrogen co-doped carbon by employing Cobalt salicylate/1,3-dimethylurea though pre-pyrolysis in high pressure is presented. The pre-pyrolysis process helped to produce more carbon, resulting in a weight loss of only 27% after twice pyrolysis. The as-prepared Co@N-doped carbon was charactered and applied as catalyst for the carbonylation of amines to form formamides for the first time in an atomic economic method. A new strategy for synthesis of Co@N-doped carbon materials which is scalable and of high-yield provides highly efficient cost-effective catalyst for economic carbonylation of amines to form formamides.

This study involves a new series granulate Ni modified La-Al2O3 (NLA) catalysts with high temperature resistant and large specific surface area for n-decane steam reforming. NLA catalysts were prepared by using a specially designed co-precipitation technique in combination with incipient wetness impregnation. Physicochemical characteristics of as-prepared catalysts were detected by using automatic adsorption instrument, X-ray diffraction (XRD), infrared spectroscopy (IR), temperature programmed reduction (H2-TPR), temperature programmed desorption (NH3-TPD), and scanning electron microscope-energy dispersive spectrometer (SEM-EDS). Significantly, the results of characterizations showed that the series NLA catalysts presented a typical mesoporous structure with a large surface area of ∼150.0 m2/g, and metal Ni was strongly interacted with Al2O3 to generate nickel aluminate spinel structures, and the addition of La improved the thermal stability of catalysts. Based on these data, the catalytic activities over NLA catalysts were evidently heightened compared with the corresponding La-Al2O3 catalyst, moreover, the 9.0 wt% NLA catalyst exhibited higher H2 yield and showed 100% n-decane conversion at 800 °C. The valuable information indicated in this work is that based on the special characters of NLA, bimetal particles can be supported on Al2O3 with different way, which should be an effective approach to maintain both catalytic activities and thermal stability.

A convenient and efficient Ni-catalyzed reaction has been developed for synthesis of mono-substituted o-carboranes, involving cross-coupling of readily available and sterically hindered 1-bromomethyl-o-carborane with various alkyl and aryl Grignard reagents under mild conditions, and the corresponding o-carborane derivatives were obtained in good to excellent yields. This method should provide a new strategy for construction of diverse and useful functionalized boron cluster compounds for medicinal chemistry and material chemistry.

A convenient and efficient Ni-catalyzed reaction has been developed for synthesis of mono-substituted o-carboranes, involving cross-coupling of readily available and sterically hindered 1-bromomethyl-o-carborane with various alkyl and aryl Grignard reagents under mild conditions, and the corresponding o-carborane derivatives were obtained in good to excellent yields. This method should provide a new strategy for construction of diverse and useful functionalized boron cluster compounds for medicinal chemistry and material chemistry.

An adaptive algorithm for the detection of burrs and cavities on a workpiece is proposed for the beburring process. The conventional force control method for the deburring process has the inherent characteristic of leaving the deburred surface or edge as an imprint of the original and can not distinguish the position deflection of the end-effector and the larger burrs. By the adaptive algorithm, the reference cutting force in normal direction and the feed-rate can be adjusted automatically according to the variation of the burr size to get smooth surface. A process force model considering the burrs effect is developed to predict the cutting force. Furthermore, the proposed algorithm is integrated into the impedance control for the deburring operation. The simulation experiment has shown that the adaptive algorithm is effective to determine the existence of the burrs, obtain the desired contour and improve the machining efficiency.

An intelligent compliance control strategy is proposed by employing a fuzzy impedance controller and a fuzzy velocity controller for improving the constrained motion control performance and the quality of the deburred surface. For the improvement of force control performance, impedance parameters can be modified according to the difference between the actual and the desired position by the fuzzy adaptation mechanism. The feedrate in tangential direction is adjusted for the special burrs and defects to get smooth surface. An empirical force model taking into consideration the burrs affection is developed to predict the cutting force. The simulation experiment shows that the algorithm is effective to obtain the desired contour and improve the control performance.

In this paper, an adaptive algorithm for the detection of burrs and cavities on a workpiece is proposed for the beburring process. The conventional force control method for the deburring process has the inherent characteristic of leaving the deburred surface or edge as an imprint of the original and can not distinguish the position deflection of the end-effector and the greater burrs. By the adaptive algorithm, the reference cutting force in normal direction and the feed-rate can be adjusted automatically according to the variation of the burr size to get smooth surface. A process force model considering the burrs effect is developed to predict the cutting force. Furthermore, the proposed algorithm is integrated into the impedance control for the deburring operation. The simulation experiment has shown that the adaptive algorithm is effective to determine the existence of the burrs, obtain the desired contour and improve the machining efficiency.