Fluorescence spectra, H-1 NMR, thermoanalysis and molecular modeling were used to investigate the host-guest inclusion system of hydroxypropyl-beta-cydodextrin (HP beta CD) with capsaicin. Job's plot was employed to confirm a 1:2 host-guest stoichiometry. Phase solubility study indicated that the apparent stability constant was 3.76 x 10(6) M-2. With the enhancing fluorescence of capsaidn complexation with HP beta CD, a spectrofluorirnetric method approach to determine the capsaidn in bulk aqueous solution was developed. Linearity was achieved wide ranges (0.05-60 mu g/mL), with low detection limit of 0.04 mu g/mL, and the relative standard deviation was 1.30%. Application to the analysis of chili powder samples obtained a satisfactory recovery of 99.5-105.6%. (C) 2019 Elsevier B.V. All rights reserved.
In order to improve the adhesion strength between diamond-like carbon (DLC) coatings and the austenitic stainless steels, DLC coatings were prepared on the surface of untreated and nitridied AISI 316L at different deposition temperatures by plasma-enhanced chemical vapor deposition (PECVD) technology. Phase structure and tribological properties of the coating were investigated. X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the phase structure of the coatings. The cross-sectional morphology was observed by scanning electron microscope (SEM), and the depth distribution of nitrogen and carbon elements was measured by EDS. Nano-indentation instrument, friction and wear tester, 3D optical microscope and scratch tester were used to evaluate the tribological properties of DLC coatings. The results show that the adhesion strength and wear resistance of DLC coatings combined with nitriding are higher than that of the single DLC coatings. Deposited at 100 degrees C, accompanied by the best modification, the hardness and adhesion strength increases by 25% and 175%, respectively, and the comprehensive performance is the best. During the deposition of DLC coatings, the nitrogen atoms in the nitrided layer are re-distributed due to the diffusion, increasing the thickness of the nitrided layer and decreasing the gradient of hardness, which contributes to a better transition between the substrate and the DLC coatings.
This clinical case report describes the fabrication of monolithic self-glazed zirconia prostheses via a digital workflow, for full-arch rehabilitation in a patient with a severely worn dentition. Prostheses composed of self-glazed zirconia are less prone to chipping, and have a lower risk of progressive wear of the opposing natural teeth. The use of a digital workflow not only ensures a higher degree of precision in the fabrication of self-glazed zirconia prostheses, but it also greatly improves patient comfort, and reduces the clinical chairside time required for adjustments.
A multi-functional nanohybrid (PyAnOH-Ag) with both a two-photon photothermal therapy (TP-PTT) effect and two-photon excited fluorescence (TPEF) imaging performance has been fabricated based on interfacial coordination interactions. The hybrid possesses a high two-photon absorption cross section (delta(TPA), 4638 GM) and detectable TPEF signals, which leads to excellent two-photon photothermal conversion. Upon irradiation at 840 nm, the temperature of the PyAnOH-Ag-PBS suspension reaches 42 degrees C in just 4 min, which results in 80% photothermal toxicity on HepG2 cells. The detectable TPEF signals can be used to monitor the cell ablation procedure. Moreover, PyAnOH-Ag exhibits a good phototherapeutic effect on tumor tissue of H22-modelled mice with almost 100% tumor growth inhibition under 840 nm irradiation for 10 min, which is superior to many reported photothermal agents. This strategy of TPEF guided TP-PTT agents can be potentially applied in a variety of therapeutic agents with monitoring ability.
High-rise steel storage racks are characterized by the asymmetrical bracing layout since only the rear plane of the racks can be braced in the bay direction. The bracing system locates at a distance from the rack, which further requires a bracket to connect the rack and the spine bracing system. This paper investigates the behavior of the bracket-to-rack connection and the bracket-to-spine-bracing connection and their influence on the elastic buckling load of the asymmetrically braced high-rise storage racks. As a general statement, the elastic buckling load of the high-rise braced racks is strongly intertwined by the initial rotational stiffness of the bracket-to-rack connection and the bracket-to-spine-bracing connection. Assuming such connections to be rotational-rigid in the analysis would lead to up to 19.7% overestimation in the elastic buckling load prediction.
Coordinate Measurement Machines (CMMs) have been extensively used in inspecting mechanical parts with higher accuracy. In order to enhance the efficiency and precision of the measurement of aviation engine blades, a sampling method of profile measurement of aviation engine blade based on the firefly algorithm is researched. Then, by comparing with the equal arc-length sampling algorithm (EAS) and the equi-parametric sampling algorithm (EPS) in one simulation, the proposed sampling algorithm shows its better sampling quality than the other two algorithms. Finally, the effectiveness of the algorithm is verified by an experimental example of blade profile. Both simulated and experimental results show that the method proposed in this paper can ensure the measurement accuracy by measuring a smaller number of points.
Expansive soil is a typical multi-crack soil, and the stability of expansive soil slope is significantly affected by cracks. In this study, pores (particles) and crack image analysis system (PCAS), a crack image processing software was used for the dynamic and quantitative measurement of the development of surface cracks in expansive soils with different compaction degree under the condition of dry-wet cycles. Furthermore, the shear strength of expansive soil with different degree of crack development was also tested. The test results showed that the greater the compaction degree, the smaller the cracking degree. The cohesion decreased with the increase of dry-wet cycles; however, the internal friction angle was less affected. For the same number of cycles, cohesion increased with the increase of the compaction degree. The relationship between the cohesion and the crack parameters including the number of crack joints, number of cracks, total length of cracks, and average width of cracks exhibited similar trends. This indicates that cohesion has some relevance with these crack parameters. The crack rate and fractal dimension exhibited linear relationship with cohesion. The research results provide an important basis for the application of crack parameters to calculate the strength parameter of expansive soil in engineering field.
Herein, the effect of cooling rate on the precipitation behavior and mechanical properties of V-added microalloyed steel is systematically investigated by nanoindentation test, X-ray diffraction, and transmission electron microscopy. The present observation reveals that random precipitates and interphase precipitates are simultaneously observed at the low cooling rate of 0.5 degrees C s(-1), whereas only random precipitates are obtained at the high cooling rate of 2 degrees C s(-1). The contribution of the nanoscale precipitates to yield strength is evaluated to be 199 MPa at the low cooling rate of 0.5 degrees C s(-1), which is almost 4 times higher than that of 2 degrees C s(-1). The predicted yield strength by semiempirical model based on the structural parameters is consistent with the result from tensile testing. In addition, the greater difference between upper and lower yield points in sample B is caused by dislocations motion, which is related to the smaller interparticle spacing of nanosized precipitates within ferrite matrix.
The exploration of an effective treatment is necessary to eliminate the emerging environmental pollutant tetrabromobisphenol A (TBBPA). In this study, a direct reduction reaction was adopted to synthesize millimetre-scale palladised sponge iron (Pd-0-s-Fe-0), the main influencing factors were further explored, the degradation intermediates were identified in detail, and the cosolvent effect on the degradation mechanism was determined. The results show that (1) within a 30 min reaction, Pd(II) ions in aqueous solution were successfully decorated onto the s-Fe-0 surface as supported by XPS, SEM, EDS, and ICP-OES analyses, (2) after 120 min of reaction, the normalized removal of TBBPA was similar to 92.2% over 0.06 wt%-Pd-0-s-Fe-0, compared with 98.2% over 0.06 wt%-Pd-nZVI and 44.4% over bare nZVI. Moreover, the extend of debromination of TBBPA surprisingly increased as the ratio of the CH3OH: H2O cosolvent decreased, compared with the debromination rates that were greatly restricted in CH3OH (100%, v/v), CH2Cl2 (100%, v/v) and isopropanol (100%, v/v), respectively. Furthermore, the O-methylation reactions over Pd-0-s-Fe-0 produced unique intermediates, including 2,6-dibromo-4-(2-(3,5-dibromo-4-methoxyphenyl) propan-2-yl) phenol (MeO-TBBPA) and 5,5'-(propane-2,2-diyl) bis(1,3-dibromo-2-methoxy-benzene) (diMeO-TBBPA) with lower toxicity. This study greatly enriches knowledge regarding the degradation mechanism of TBBPA over millimetre-scale sponge iron.
Mixed matrix membranes (MMMs) of poly(vinyl alcohol) (PVA) containing certain amounts of ZSM-5 zeolite were evaluated for pervaporation dehydration of highly concentrated isopropanol aqueous solution. The effects of zeolite content, feed composition and feed temperature on the membrane separation performance are in detail examined by using a preliminarily one-factor-each time method and a systematically response surface methodology (RSM). Preliminarily results show the dehydration separation factor/selectivity have been greatly boosted but without the cost of pervaporation flux/permeance after adding zeolite ZSM-5, and it is consistent very well with the Arrhenius activation energy estimations where water molecules require much less energy whereas ethanol molecules need much more energy to transport through the membrane, probably because of the favorable hydrophilic and porous features of zeolite ZSM-5 as revealed by swelling and water contact angle results. High feed isopropanol concentration and low feed temperature are both observed to lead to very low pervaporation flux/permeance but very relatively high separation factor/selectivity. The RSM results suggest that zeolite content, feed composition and feed temperature all have highly significant impacts on total pervaporation flux and separation factor. The interaction effect of zeolite content and feed temperature on separation factor is for the first time found to be also significant. The polynomial models established according to the RSM analysis can fit very well against the experimental data with a very high coefficient of determination and the predictions given for optimized conditions have been experimentally confirmed by the validation results with a deviation of less than 2.0%. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
High-precision profile reconstruction is a key issue in the profile detection and visualization of aero-engine blades. A method based on adaptive step size bat algorithm (ASSBA) for blade profile reconstruction and an adaptive mesh model for visualization analysis of the key machining errors are proposed. Firstly, the original bat algorithm (BA) is improved to introduce the global stage and local search stage. Then, combined with the node layer characteristics of the blade measurement data, the ASSBA is used to fit the optimal surface. Further, the adaptive mesh is planned on the blade profile to extract various evaluation parameters. Finally, the algorithm analysis and verification are carried out based on a certain type of blade. The results show this reconstruction method can get the fitted surface more quickly and accurately than other iterative methods. Simultaneously, the visualization method and corresponding software system can intuitively visualize the blade profile error, the twist deformation error, the swept deformation error, the bending deformation error and the cross-section line profile error.
Nonlinearities have been the major obstructions that limit the computational efficiency in power electronic circuit simulation for a long time. Yet there is no standard way for dealing with them. This paper presents a new method that makes the handling of nonlinearities fast and stable. In the proposed method, nonlinearities are transformed into a uniform representation-a constant resistor in parallel with a companion current source, thus making the system admittance matrix constant for fixed time-step simulation. To solve for the corresponding companion current source, nonlinearities are treated as either current or voltage sources and a diagonal time-varying matrix equation is developed. Three methods are proposed for solving the matrix equation-precomputed inversion or factorization, modified Gaussian elimination, and updating inverse using the Sherman-Morrison formula-that can fit different system sizes and applications. The proposed method is validated by two common power electronic converter topologies, both in offline and real-time simulation. Offline tests show that the proposed method achieved the same accuracy with themature simulation software while being more than ten times faster. The same test cases are also implemented into field programmable gate arrays based real-time simulation experiments for verification.
With the development of global economy and industry, reducing the development cost of oil and gas resources, and seeking the relationship between the oil industry and the new geo-energy industry, is becoming a tendency of the oil industry in the next decades. Radial jet drilling (RJD) is an unconventional drilling technology to reach the sweet spots by using the high-pressure liquid jet or abrasive jet, which has been proved as a cost-effective technique. Recently, RJD technique is expected to be applied in the development of some new-type geo-energy (shale gas and geothermal). In the present paper, technique feature, advantages, and limitation of the RJD technique are summarized. The key issues, drilling performance (which is influenced by cross-impacted factors, such as the equipment parameters, extended length of laterals and the operating pump displacement) and the trajectory measuring method are also discussed. Based on the advantages of RJD technique and the solutions of the key issues, RJD could be a flexible technique in the exploitation of new geo-energy. (C) 2019 The Authors. Published by Elsevier Ltd.
This paper presents an enhanced modulation technique for dual converters with isolated supplies. This unified modulation technique is applicable for any positive voltage ratio between the isolated supplies. The modulation technique enhances the quality of converter output voltage compared to using previously reported methods. The effectiveness of the proposed technique is validated and results are presented for an open-end winding induction motor to demonstrate the advantages.
Coal with high content of alkali metal has limited use in the combustion process. The slow and rapid pyrolysis and combustion characteristics of sodium-rich Zhundong coal were investigated using a thermal gravimetric analyzer and one-dimensional drop-tube furnace. The results show that the process was complete when the final temperature exceeds 900 degrees C in slow pyrolysis, while in rapid pyrolysis it lasts for short residence time in the whole furnace. The weight loss ratio in rapid pyrolysis was significantly higher than that in slow pyrolysis, and shows different trends at different reaction temperatures. There is an extremum value of weight loss ratio obtained at 800 degrees C in rapid pyrolysis, which is accompanied by the maximum value for the diameter of pores and the minimum value for specific surface area. Most alkali elements are released from the solid product, and the amounts of released alkali elements in combustion are higher than that in pyrolysis process. The apparent activation energy in the two pyrolysis processes and release of alkali in combustion were evaluated using different models, which demonstrates that the alkali release trend in combustion is easier than that of pyrolysis.