Structural optimization to include material selection

The mini-max dual method ia applied for solving the material selection structural optimization problems. A somewhat general objective function is introduced to consider structural weight and material cost simultaneously. It is expressed by the sum of scaled structural weight and material cost. The present formulation can yield minimum cost and minimum weight designs as two distinct special cases. It is shown that practically useful intermediate optimal designs can exist between the two extremes. Only truss structures are considered as a representative example. One numerical example is provided to illustrate the change in optimal material distribution when various objective functions are employed. A particular advantage in using the dual method for the material selection problem is also described.     

An alternative definition of material properties

The stresslstrain relation is initially discussed in general form. The normal matrix formulation employing the Lamé Constants and the more 'practical' formulation based on the Elastic Modulus and Poisson's Ratio are detailed.
An alternative approach employing the wave speeds of the material as the basic material parameters is discussed. This approach has a number of advantages over the present tensile testing methods. The main advantages are that the properties can be obtained on the actual part or specimen without resorting to destructive testing means, and the data can be collected with the same strain gauge equipment that is to be employed in subsequent testing procedures.
The problem associated with the measurement of short duration, low amplitude pulses is discussed and the broad details of the required instrumentation are given.
Two simple experiments are illustrated in which firstly, the wave velocity in a bar is obtained and secondly, the dilatational and shear wave speeds are obtained in a plate structure.     

ac losses of multifilament superconductors reduced below the level of filament hysteresis losses due to field screening by filament coupling currents

In measurements on multifilament superconductors, it was found that overall ac losses fall below the level of filament hysteresis losses at sufficiently high frequencies, due to field screening by filament coupling currents. At low frequencies, overall loss should also fall below the hysteresis loss level, provided f?>_m a critical frequency defined in the next text). This may be arranged by the choice of large values of the twist pitch, or small values of the mean transverse resistivity p_e.     

On the coupling current losses in a multifilamentary superconducting composite

The coupling current losses in a superconducting multifilamentary composite exposed to trapezoidally varying external magnetic field and carrying a small transport current are investigated for the volume pinning force density described with the dependence: F_v = α B^1?γ. Such a model allows estimation of the deviations from the solution based on Bean's (γ = 0) critical state model. Results indicate that there exists a region of small magnetic field amplitudes for which discrepancies are largest. They are also very sensitive to the rate of magnetic field change.     

Q-factor measurements of open resonators in the millimeter-waverange including coupling losses

The unloaded quality factor as well as the coupling coefficient of open resonators are determined by evaluating measured complex reflection coefficients. The cavity is described by an equivalent circuit, the parameters of this circuit are calculated by means of a least-square fit of the simulated to the measured reflection coefficients. The solution is obtained using the Householder-algorithm, which promises very fast and stable computation. This approach is capable of evaluating quality-factor measurements for each type of resonator, even with losses in the coupling aperture. Its validity is illustrated by measurements in the cm- and mm-wave range     

Experimental evidence for an interaction effect in the coupling losses of cabled superconductors

It is experimentally demonstrated on a series of one-stage superconducting cables, composed from multifilamentary superconducting wires, that the coupling current losses being induced in the wire and in the cable matrix, contain interaction loss terms directly proportional to the wire twist pitch I_w. This proves partly their theoretically expected l_c.l_w-dependence. Different twisting directions in a one or multistage superconducting cable increase the ac losses and should be avoided. The magnitude of the effect can become important.     

Influence of magnet winding geometry on coupling losses of multifilament superconductors

Coupling current losses have been investigated for magnet windings made from multifilament wires. The influence of the collective interactions on the decay time constant and on the coupling losses is discussed in terms of the demagnetization factor. The analysis, based on a simplified model, is confirmed by the τ and loss measurements for samples with different geometries     

双层交换耦合电波吸收材料的研究

由永磁体和软磁性复合电波吸收材料制成双层交换耦合吸波材料，其吸波特性较两种单层吸波材料有较大提高：最大吸收量A从15－17dB提高到23．5dB，10dB带宽也由2．3－3．25GHz增加到3．75GHz，匹配厚度1．79mm。软磁层厚度的改变和两层间添加介质均对交换耦合效应有较大的影响，导电性能好的介质可大幅度提高双层交换耦合吸波材料的性能。     

Power factor definition in single phase system with arbitrary waveform according to similarity

Abstract

A new definition of power factor, which is suitable for an arbitrary waveform of voltage and current in a single‐phase system, is presented according to similarity between voltage and current waveforms. The similarity is described in infinite dimensions real vector space, and the power factor is defined as the multiplication of rootmean‐ square (RMS) value factor λ _RMS and phase factor λ_?. The new definition is compatible with IEEE Trial‐Use Standard 1459–2000, and can be a useful reference for power factor measurement, power factor correction and power compensation.     

Predicting different losses of photonic crystal fibers in material and hetero-core domain

In order to develop the effective transmission in photonic crystal fiber (PCF), the (realizable fiber i.e.,) losses arising from bending as well as splicing are very vital issues. We report here macrobending loss of PCFs in different material composites. Further, we make comprehensive numerical analysis related to splice loss issues arising from joining PCF with PCF and single mode fiber as well. We additionally investigate dependence of all these losses with respect to structural parameters of PCF. Hetero core systems are found to yield lower losses as compared to their identical counterpart. The numerical estimates reported here will provide a base for engineering effective communication guides in the context of material and hybrid core domain.     

Generalization of the Zgoubi method for ray-tracing to include electric fields

The ray-tracing and spin tracking code Zgoubi, originally dedicated to the numerical integration of Lorentz equation in magnetic fields, has been improved in order to allow ray-tracing in electric and electromagnetic fields. This report describes the method, and presents detailed examples of application, including the achromatic quadrupole.     

Selffield losses and selffield stability of superconducting wires with low conductivity matrix material

The influence of the normal material in a superconducting wire on the selffield losses has been investigated. The results show that the contribution of the normal material is considerable in the case of a highly conductive material like Cu. Measurements on wires with CuNi-material show no significant contribution of the normal material to the losses. In the latter case, however, special attention should be paid to stability. Measurements show that the obtainable maximum current under a.c. conditions obeys the adiabatic stability criterion rather well. The dependence of the maximum current amplitude on the critical current density and the diameter of the wire has been obtained. Wires with Al cores inside the NbTi filaments for better stabilization have also been investigated regarding maximum current and selffield losses.     

Effect of the respective positions of filament bundles and stabilizing copper on coupling losses in superconducting composites

Superconductor stabilization is ensured by embedding filaments in a copper matrix. Calculations show that a central copper region always leads to an increase in loss in comparison with the case where the filaments are located in a central region surrounded by an outer copper sheath. Practical cases with a copper matrix and also mixed matrix conductors are discussed. Attention is drawn to the comparative roles played by the effective transverse resistivity of the matrix and the copper resistivity.     

Generalization of equivalent crystal theory to include angular dependence

The original equivalent crystal theory is a semi-empirical method for calculating the configurational energy of atomic systems. Each atomic site in the real crystal with defects is assigned an equivalent lattice constant, in general different from the ground state value. This parameter corresponds to a local compression or expansion of the perfect lattice. The basic method considers these volumetric transformations and, in addition, introduces the possibility that the reference lattice is anisotropically distorted. These distortions however, were introduced ad-hoc. In this work, we generalize the original Equivalent Crystal Theory by introducing site-dependent directional distortions of the lattice which account for the dependence of the energy on anisotropic local density variations. This is done in the spirit of the original framework of ECT, but includes a gradient in the density. This approach is introduced to ECT and may apply to other semi-empirical methods by making use of readily available first-principles results to fix parameters. We develop here the basic framework, and apply it to the calculation of Fe(1 1 0) and Fe(1 1 1) surface energy formation, and to the vacancy energy curve. The results, compared with first-principles calculations, show an improvement over previous semi-empirical approaches.