The measured equation of invariance: a new concept in field computation

Computations of electromagnetic fields are based either on differential equations or on integral equations. The differential equation approach using finite difference or finite element methods results in sparse matrices, which is an advantage, but has to cover large volumes, which is a disadvantage. The integral equation approach using the method of moments (MOM) limits the mesh to the surface of the object, which is an advantage, but results in full matrices, which is a disadvantage. It is noted that the ideal case would be to reduce the finite difference type equations close to the object surface and still preserve the sparsity of the matrices. The measured equation of invariance is a new concept in field computation capable of approaching this ideal situation. The mathematics and reasonings to reach a novel computational method based on this concept are presented. It is shown that the method is robust for both convex and concave objects, is much faster than the MOM, and uses a fraction of the memory.Peer ReviewedPostprint (published version

Measured equation of invariance: a new concept in field computations

Numerical computations of frequency domain field problems or elliptical partial differential equations may be based on differential equations or integral equations. The new concept of field computation presented in this paper is based on the postulate of the existence of linear equations of the discretized nodal values of the fields, different from the conventional equations, but leading to the same solutions. The postulated equations are local and invariant to excitation. It is shown how the equations can be determined by a sequence ofPeer ReviewedPostprint (published version

Pulsed Eddy Current Testing of Inner Wall Flaws in Pipe under Insulation

AbstractThe localized inner wall corrosions in the pipe under insulation are especially hazardous to pipelines. An inspection system is designed to detect inner wall flaws in pipe based on pulsed eddy current technique. Simulation specimens with large area thinning, localized grove-like corrosions and pit-like corrosions are machined, and probes are designed and manufactured. A series of experiments are performed to optimize testing parameters and improve detection sensitivity. The experiments show that the system can detect 10 percent thinning of wall under insulation when the thickness of pipe and insulation is respectively 10mm and 110mm. The detection accuracy can meet the requirement in the inspection of pressure pipeline. The system can also detect some localized corrosions under insulation

Hardening mechanism of commercially pure Mg processed by high pressure torsion at room temperature

Coarse-grained Mg in the as-cast condition and fine-grained Mg in the extruded condition were processed by high pressure torsion (HPT) at room temperature for up to 16 turns. Microstructure observation and texture analysis indicate that to fulfil the Von Mises criterion, the non-basal slip is activated in the as-cast Mg and tension twinning is activated in the as-extruded Mg. Although the deformation mechanism is different in the as-cast Mg and the as-extruded Mg during HPT, their hardening evolutions are similar, i.e. after 1/8 turn of HPT, microhardness of the as-cast Mg and the extruded Mg both show a significant increase and further HPT processing does not significantly further increase the microhardness. Texture strengthening can explain the rapid hardening. Hardness anisotropy and texture data results suggest that texture strengthening plays an important role for both types of samples. Texture strengthening weakens with decreasing grain size

Dynamic Analysis of a Rotating Shaft Subject to the Double Cutting Force and Time-varying Mass Effects of the Rod

AbstractThis paper investigates the dynamic behaviors of a rotating shaft subjected to the double cutting force and time-varying mass effects. The Timoshenko beam theory is used to model the rotating shaft, and the general boundary condition is assumed as the clamped-hinged supports. This system is used to simulate the manufacture process of the double turret CNC lathes, and the mass of the rod which is reduced gradually in cutting process. The system equations of motion are derived based on the global assumed mode method, and the dynamic responses of the system are obtained by Runge-Kutta numerical method. The transformation matrix is derived to make the equation of motion completing the boundary geometric constraints. The numerical results compare the dynamic response in different moving speeds and skew angles of the cutting forces with/without the time-varying mass effects. Additionally, this paper compares the response with single cutting force and double force. The results show that the double moving force system can reduce not only the machining time but also the amplitude of shaft vibration

Synthesis and Properties of Ag / CuO / SiO2 Nanocomposites

In this paper the composites Ag / SiO2 with regularly distributed in bulk matrix silver and copper oxide nanoparticles were synthesized. Herewith, copper ions was introduced into porous support at the stage of sol-gel synthesis. Sample Ag / CuO / SiO2 was tested by the catalytic reaction of CO oxidation and com-pared with Ag / SiO2. It was revealed that sample with introduced copper show lower activity .This fact can be explained by formation of silver cuprate during preparation of composite Ag / CuO / SiO2. Treatment by reaction mixture (CO and O2) led to release of silver in ionic, clusters and metal states that increased cata-lytic activity of the composite. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3561

Effect of Different Presentation Orders on Processing Time and Time Estimation of Verbal Working Memory

This research explored the effect of different presentation orders on processing time and time estimation, from the perspective of verbal working memory dual-task mode task. 108 participants took part in memorizing order or disorder French word, it showed that the presentation order significantly shortens the processing time and estimation time, thus it proved that the orderly presentation can enhance the work efficiency compared with the disorderly presentation. This research highlights the impact of presentation upon the verbal working memory, which had important theoretical and practical implications.</p