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排序方式: 共有144条查询结果,搜索用时 15 毫秒
1.
Oxidative electropolymerization of aniline (Ani) in phosphoric acid (H3PO4) on composite 2B pencil graphite was accomplished using selected inorganic salts as supporting electrolytes. These salts determined the degree of conductivity of polyaniline (PAni) formed. The conductivity was in the order of CaCl2 > KCl > ZnCl2 > ZnSO4 > Ca3(PO4)2. The three pairs of redox peaks in the voltammogram of PAni formed in the presence of 0.06 M Ca3(PO4)2 and 0.2 M ZnSO4 have shifted 300 mV to the negative potential. The shifting of peaks is strongly influenced by type of anions' presence in the salts. However, the nature of the available cations had no significant effect. The negative shifts of redox peaks were exploited to facilitate the electrocopolymerization of Ani and ortho-phenylenediamine (oPD). The formation of the poly(Ani-co-oPD) was confirmed by the FTIR spectra. 相似文献
2.
A boy with a large intracranial glioma of the optic tract and probable neurofibromatosis of the first type was observed for 8 years since the age of 7 years. A series of MR scans was made over this period. A notable decrease of the tumor size was seen on its signals on the MR scans. This was paralleled by an improvement of the vision acuity, color field, and visual field on the involved eye. Patient's grandmother had an intracranial glioma of the optic nerve with a slight but stable decrease of the visual functions. The tumor shape in the grandmother and grandchild is remarkably similar. This finding in the grandmother and stability of her vision decreased from childhood permit us to propose that the tumor did not develop and even regressed with time. 相似文献
3.
Nazanin Pourmand Vijay Parsa Angela Weaver 《International Journal of Speech Technology》2013,16(4):363-379
The performance of several noise reduction algorithms intended for wideband telephony was evaluated both subjectively and objectively. The chosen algorithms were based on statistical modeling, spectral subtraction, Wiener filtering, or subspace modelling principles. A customized wideband noise reduction database containing speech samples corrupted by three types of background noises at three SNR levels, along with their enhanced versions was created. The overall quality of the speech samples in the database was subsequently rated by a group of listeners with normal hearing capabilities. Comprehensive statistical analyses were performed to assess the reliability of the subjective data, and to assess the performance of noise reduction algorithms across varied noisy conditions. The subjective quality ratings were then used to investigate the performance of several auditory model-based objective quality metrics. Key results from these investigations include: (a) there was a high degree of inter- and intra-subject reliability in the subjective ratings, (b) noise reduction algorithms enhance speech quality for only a subset of the noise conditions, and (c) auditory model-based metrics perform similarly in predicting speech quality ratings, when speech quality scores pertaining to a particular noise condition were averaged. 相似文献
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To speed up data‐intensive programs, two complementary techniques, namely nested loops parallelization and data locality optimization, should be considered. Effective parallelization techniques distribute the computation and necessary data across different processors, whereas data locality places data on the same processor. Therefore, locality and parallelization may demand different loop transformations. As such, an integrated approach that combines these two can generate much better results than each individual approach. This paper proposes a unified approach that integrates these two techniques to obtain an appropriate loop transformation. Applying this transformation results in coarse grain parallelism through exploiting the largest possible groups of outer permutable loops in addition to data locality through dependence satisfaction at inner loops. These groups can be further tiled to improve data locality through exploiting data reuse in multiple dimensions. 相似文献
6.
Behrouz Parsa Moghaddam José António Tenreiro Machado 《Journal of scientific computing》2017,71(3):1351-1374
This paper proposes accurate and robust algorithms for approximating variable order fractional derivatives of arbitrary order. The proposed schemes are based on finite difference approximations. We compare the performance of algorithms by introducing a new formulation of experimental convergence order. Two initial value problems are considered and solved by means of the proposed methods. Numerical results are provided justifying the usefulness of the proposed methods. 相似文献
7.
A quantitative metallographic assessment of the evolution of porosity during processing and creep in single crystal Ni‐base super alloys 下载免费PDF全文
H. Buck P. Wollgramm A. B. Parsa G. Eggeler 《Materialwissenschaft und Werkstofftechnik》2015,46(6):577-590
The present work reviews previous research on the evolution of porosity. It presents new results from a detailed study on the evolution of porosity during casting, heat treatment and creep of a single crystal Ni‐base superalloy subjected to uniaxial tensile creep at 1050 °C and 160 MPa in [001] and [110] directions. A quantitative metallographic study was performed on carefully polished metallographic cross sections, monitoring sampling fields of 4500 × 1000 µm2 using the back scatter contrast of an analytical scanning electron microscope; evolutions of pore sizes and pore form factors were analyzed and all important details which were previously revealed in a synchrotron study could be reproduced. In addition, it was observed that micro cracks form at larger cast pores. They interlink and thus initiate final rupture. The [110] tensile creep tests showed lower rupture strains than the [001] experiments. In agreement with earlier work, this can be rationalized on the basis of aligned porosity along primary dendrites. 相似文献
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9.
RM Gipstein JW Coburn DA Adams DB Lee KP Parsa A Sellers WN Suki SG Massry 《Canadian Metallurgical Quarterly》1976,136(11):1273-1280
Eleven patients with chronic renal failure and presumed secondary hyperparathyroidism developed a syndrome of medial calcinosis of the arteries and painful ischemic ulcers of the fingers, legs, or thighs, or any combination of the three. Five patients required maintenance hemodialysis; six had functioning renal homografts. Severe hyperphosphatemia had existed in each; seven showed roentgenographic evidence of subperiosteal resorption. Similarities are evident between the lesions and experimentally produced calciphylaxix. The lesions demonstrated a relentless, progressive course, with serious morbidity and mortality. Hyperplastic or adenomatours parathyroid tissue was removed from ten of 11 patients unergoing surgical procedures; healing followed in seven patients. Treatment with phosphate-binding antacids to lower serum phosphorus levels may prevent this syndrome. Total or subtotal parathyroidectomy should be considered when ischemic skin lesions appear in uremic patients or in renal transplant recipients. 相似文献
10.
High torque pulsation is a major disadvantage of most interior permanent-magnet (IPM) motor configurations. Choosing the proper number of stator slots and winding distribution as well as increasing number of phases are among the possible solutions for reducing torque pulsation. In this paper, five-phase IPM motor with fractional-slot stator is studied. It is shown that despite other IPM motors, the new five-phase IPM motor with fractional slot has a very low torque pulsation. For comparison purposes, a five-phase IPM motor with common configuration is also considered. It is shown that the torque pulsation of the proposed fractional-slot five-phase IPM motor is much lower than the conventional five-phase IPM motor. Nonlinear finite-element method is used to analyze different machine configurations. A prototype four-pole five-phase IPM motor with 15 stator slots has been built and is used for experimental verification 相似文献