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61.
The continuous increase in the utilization of polymeric materials in many specific applications has demanded detailed knowledge of their physical properties, both during their processing as raw material, as well as in the overall range of the working temperature of the final polymer product. Nowadays, mathematical modeling has become an established tool for improving process control and product quality in polymer processing. As models become more sophisticated, there is an increasing need for reliable thermo-physical properties data. In this work, a very simple and low cost arrangement, a variation of the well-known split column method, is employed in the experimental determination of the thermal conductivity of some selected polymers. Rectangular parallelepiped shaped samples, (200 × 100 × 20) mm were prepared by cutting such pieces from long commercial plates or through an extrusion process starting from the powder or pellets of the solid polymer. Experimental results show a solid consistence when they are checked against results obtained by other techniques. 相似文献
62.
In this paper we present several relaxed inexact projection methods for the split feasibility problem (SFP). Each iteration of the first proposed algorithm consists of a projection onto a halfspace containing the given closed convex set. The algorithm can be implemented easily and its global convergence to the solution can be established under suitable conditions. Moreover,we present some modifications of the relaxed inexact projection method with constant stepsize by adopting Armijo-like search. We furthermore present a variable-step relaxed inexact projection method which does not require the computation of the matrix inverses and the largest eigenvalue of the matrix ATA, and the objective function can decrease sufficiently at each iteration. We show convergence of these modified algorithms under mild conditions. Finally, we perform some numerical experiments, which show the behavior of the algorithms proposed. 相似文献
63.
We study randomized confidence intervals for binomial proportions, comparing coverage, length and the impact of the randomization. It is seen that the recently proposed split sample intervals can be improved upon in various ways. Criticisms of randomized intervals are discussed. 相似文献
64.
Loading and unloading split hopkinson pressure bar pulse-shaping techniques for dynamic hysteretic loops 总被引:4,自引:0,他引:4
Pulse-shaping techniques are developed for both the loading and unloading paths of a split Hopkinson pressure bar (SHPB) experiment
to obtain valid dynamic stress-strain loops for engineering materials. Front and rear pulse-shapers, in association with a
momentum trap, are used to precisely control the profiles of the loading and unloading portions of the incident pulse. The
modifications, ensure that the specimen deforms at the same constant strain rate under dynamic stress equilibrium during both
loading and unloading stages of an experiment so that dynamic stress-strain loops can be accurately determined. Dynamic stress-strain
loops with a constant strain rate for a nickel-titanium shape memory alloy and polymethyl methacrylate are determined using
the modified SHPB. The modified momentum trap prevents repeated loading on a specimen without affecting the amplitude of the
desired loading pulse and without damaging the bar at high stress levels. 相似文献
65.
We proposed and numerically investigated the influence of spatial topology on the infrared frequency region response of chiral metamaterials based on discrete deformed split ring resonators. Compared with the well studied continuous helix, the proposed metamaterials with discrete topology exhibit broad band chiral electromagnetic response. It is shown that the conversion between left and right circular polarization waves for our model is much broader than the continuous helix model. The observed cross-coupling between electric and magnetic fields results from the chiral electric currents on the resonators due to the broken mirror symmetry. The findings are useful for the design of future real three-dimensional chiral metamaterials with tunable optical response. 相似文献
66.
In the paper, a multiframe blind image deconvolution method based on total variation and framelet regularizer is proposed. An adapted version of the split Bregman method is proposed to efficiently solve the resulting minimization problems. In each iteration, four sub-problems need to be solved, one of which can be very efficiently and easily solved via fast Fourier transform implementation or closed form solution. Both simulated noisy and blurred frames and real degraded frames are used to verify the effectiveness of the proposed method. Comparative experimental results show that the proposed method can efficiently remove the blur and noises and restore high quality sharp image. 相似文献
67.
We combine different split ring resonator (SRR) unit cells along three axes respectively and study the electromagnetic behaviors of combinations numerically, with the purpose of broadening the frequency band of negative permeability. When combining SRRs in z-direction, the wave propagation direction, it is found that the bandwidth of negative permeability is broadened by 0.22 GHz. The same bandwidth expansion effects, however, are not observed along the other two axes. In addition, it is feasible to obtain two isolated frequency bands with negative permeability by combining SRRs along three axes. 相似文献
68.
Studies are presented on in-plane shear properties of a typical plain weave E-glass/epoxy composite under high strain rate loading. In-plane shear properties were determined with ±45 degree off-axis compression and tension tests using a split Hopkinson pressure bar apparatus. In-plane shear properties are presented as a function of axial and shear strain rates. The range of axial strain rates for off-axis compression tests was 819–2003 per sec, and for off-axis tension tests was 91–180 per sec, whereas the range of shear strain rates for off-axis compression tests was 1388–3442 per sec and for off-axis tension tests was 153–303 per sec. In general, it was observed that in-plane shear strength was enhanced at high strain rate loading compared to that at quasi-static loading. Also, it was observed that in-plane shear strength increased with increasing strain rate within the range of strain rates considered. 相似文献
69.
70.
A column generation approach is presented for the split delivery vehicle routing problem with large demand. Columns include route and delivery amount information. Pricing sub-problems are solved by a limited-search-with-bound algorithm. Feasible solutions are obtained iteratively by fixing one route once. Numerical experiments show better solutions than in the literature. 相似文献