A new interval uncertainty optimization algorithm is proposed to replace two-layer nested optimization, owing to the low efficiency of the latter. The radial basis function network is established to obtain the first-order differential, which is difficult to achieve in practical engineering problems. The results obtained by this network differential method are verified by a mathematical example. The network differential method is combined with the interval perturbation method to compute the bounds of uncertain objective functions and constraints, and the subinterval method is introduced to address the large level of uncertainty. The example of a compression spring shows the feasibility of this interval analysis method. The interval uncertain optimization problem is transformed into a deterministic one through the interval order relationship and probability model, and solved using the genetic algorithm or non-dominated sorting genetic algorithm-II. A numerical example and electromagnetic buffer model demonstrate the accuracy, efficiency and practicability of this new method.
Abstract. With the development of motor technology, sensorless control attracts more and more attention. In this paper, an improved flux linkage observer is proposed to overcome issues including inaccurate initial positions and sampling noise. The voltage and current models are combined, and a sliding-mode observer is designed based on the hybrid model to obtain the compensation voltage. Therefore, the estimated flux linkage after compensation can greatly resist the influence caused by inaccurate initial positions or sampling noise. Phase-locked loop technology is used to process the estimated flux linkage to get the stable estimated speed and position. The proposed scheme has a simple structure and only one parameter. It is easy to use and adjust in practice. The simulation and experimental results verify that the proposed algorithm is effective, and the estimated flux linkage and position is accurate with an inaccurate initial position.
A PdO/CeO2 composite with a rod-like nanoporous skeletal structure was prepared by combining the dealloying of Al-Ce-Pd alloy ribbons with calcination. For CO oxidation and CH4 combustion, the nanoporous PdO/CeO2 composite exhibits excellent catalytic activity, and the complete reaction temperatures of CO and CH4 are 80 °C and 380 °C, respectively. In addition, the composite possesses excellent cycle stability, CO2 toxicity, and water resistance, and the catalytic activity hardly decreases after 100 h of long-term stability testing in the presence of water vapour (2 × 105 ppm). The results of a series of characterizations indicate that the enhanced catalytic activity can be attributed to the good dispersion of the PdO nanoparticles, large specific surface area, strong redox capacity, interaction between PdO and CeO2, and more surface active oxygen on PdO. The results of the characterization and experiments also indicate that the PdO nanoparticles, prepared by combining dealloying and calcination, have a stronger catalytic activity than do Pd nanoparticles. Finally, a simple model is used to summarize the catalytic mechanism of the PdO/CeO2 composite. It is hoped that this work will provide insights into the development of high-activity catalysts.
This paper explores the transient mechanics mechanism of the projectile with double rotating bands engraving into the rifle and the propellant gas pressure distribution law during the rotating band engraving process. Previous studies usually ignored the coupling of projectile, artillery, and gunpowder parameters during the engraving process. To end this, taking a large-caliber artillery system as the research object, a projectile-barrel-charge coupled finite element model is established based on the two-phase flow interior ballistic theory and the finite element method, followed by numerical simulation. Through the comparison with experimental results, such a modeling method is proved to be effective.
This article proposes a double-primaries tubular permanent magnet synchronous linear motor (DP-TPMSLM) with a low thrust ripple composed of two primaries, a secondary, and a flux barrier. For DP-TPMSLM, the odd harmonics in the detent force can be effectively eliminated by decoupling and modulating its cogging and end forces. The pole-slot combination and winding arrangement of the proposed motor are analyzed to realize the electromagnetic properties of the two primaries superimposed on each other. This article selects the 12-slot, 11-pole DP-TPMSLM as a sample, and a subdomain model considering the effects of cogging, ends, and magnetic barriers is developed through coordinate transformations. Subsequently, the structure of the motor end teeth is improved by combining the advantages of the proposed subdomain model and the finite-element method, which effectively suppresses the even harmonics present in the detent force, thus further reducing the thrust ripple of the motor. Finally, a prototype test and control platforms are built, and the experimental results show that the proposed DP-TPMSLM has a low thrust ripple and excellent working performance.
The in situ graft copolymerization of starch with D,L-lactide was investigated. It is found that lactide can be grafted onto starch via ring-opening polymerization in the presence of poly(ethylene glycol) (PEG), resulting starch-PLA graft copolymers. Increasing the amount of PEG to the reacting system results in the increase of the grafting of PLA onto starch, and the molecular weight of PEG plays a prominent role in affecting PLA grafting.
Language,the product of culture,cannot be considered separately from culture.To some extent,people cannot really master a certain country's language unless they understand the culture of a nation very well.Language teaching should be integrated with language teaching in Korean teaching.Language teaching need to be improved combining the specific cultural and knowledge background.Teachers should introduce the Korean culture into the language teaching.Only in this circumstance,Korean teaching can be improved effectively.
Gun firing is a process that converts propellant chemical energy to projectile kinetic energy and other kinds of energies. In order to explore the energy conversion process, firstly, the interior ballistics mathematical model and the barrel-projectile finite element model are built and solved. Then, the related variable values and energy values are obtained and discussed. Finally, for improving energy efficiency, the interval uncertainty optimization problem is modeled, and then solved using the two-layer nested optimization strategy and back-propagation (BP) neural network surrogate model. Calculation results show that, after optimization, the heat efficiency raises from 31.13% to 33.05% and the max rifling stress decreases from 893.68 to 859.76 Mpa, which would improve the firing performance and prolong the lifetime of the gun barrel.
Two model drugs,indomethacin and vitamin E( α-tocopherol),which have different physical stae and similar hydrophobicity,were incorporated respectively into polymerc micelles in aqueous media by dialysis method. The micelles were formed from two types of biodegradable amphiphilic block copolymers based on methoxy poly(ethylene glycol)(mPEG) as a hydrophilic block and either crystalline poly(e-caprolactone-b-L- lactide) ( P ( CL-b-LLA )) or amorphous poly(e-caprolactone-b-D,L-lactide) ( P ( CL-b-DLLA )) as a hydrophobic block. The morphology and drug loading property of the polymeric micelles were characterized by transmission electron microscopy ( TEM ),laser light scattering ( LLS ),ultraviolet ( UV ) spectroscopy measureemnts. It was found that incorporating drugs into the micelles resulted in significant changes of the micellar morphologies. The different behaviors of the morphological change depended mainly on the crystalline property of the core-forming blocks. The morphology of micelles formed with P( CL-b-LLA)-b-mPEG changed from short rod-like cylinders to wormike ones; whereas those formed with P( CL-b-DLLA)-b-mPEG changed from spheres to cylinders. In addition,the transformation of the micellar morphologies upon the drug entrapment was influenced by the hydrophobicity of the drugs more significantly than by the physical state of the drugs, while the drug loading amount was affected by the comatibility between carriers and drugs. Much more liquid- like drugs were entrapped in the amphiphilic copolymers with non-crystalline core.
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