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961.
The effective resolution of AD converters is a crucial quantization quality parameter in modern instrumentation. A usual theoretical assumption about the quantized (training) signal is that it is a pure sine wave with a “zero” offset. This means that either the average value of the sine wave is equal to one of the threshold levels (quantizer without dead zone) or that it lies exactly in the middle of them (rounding quantizer). In the measurement technique this assumption is hardly fulfilled, and that is why we meet something intermediate between the above-mentioned hypothetical situations. Here we generalize the known results for “zero” offset to the case of unknown offset. A general problem of an arbitrary random offset distribution is considered first. Two important practical cases are then analyzed. The first one is an unknown and nonrandom offset (one-point distribution). The second one is a case of a uniform distribution of the offset (effect of dithering on quantizer input). In particular, the expected values and variances are derived and analyzed versus the offset and the number of quantizing levels. The results obtained are applied to the effective resolution measurement 相似文献
962.
Hydrogen is the lightest element in nature, and so, its detection and quantitative analysis is difficult by the conventional
methods utilized for other elements. In the recent years the technique of elastic recoil detection analysis (ERD) using 1–2
MeV He+ beam has been developed to quantitatively and simultaneously analyze hydrogen and its isotopes in solids. Such a facility
has been set up using the 2 MeV Van-de-Graaff accelerator at IIT Kanpur. It facilitates H and D analysis in a material up
to a depth of ∼ 1μm with a detection sensitivity of 0·1 at.% and depth resolution of about 300 ?. The application potential of this setup is
illustrated by presenting the results of measurements performed on Al:H:D systems prepared by plasma source ion implantation
and highT
c YBCO pellets exposed to humid atmosphere. 相似文献
963.
The effect of transverse stitching on the stresses in the adhesive is investigated using an adhesive sandwich model with nonlinear adhesive properties and a transverse stitching model for adhesive bonded composite single-lap and double-lap joints. Numerical results indicate that, among all stitching parameters, thread pretension and stitch density have significant effect on the peel stresses in the adhesive; increase in the thread pretension and the stitch density leads to a decrease in peel stress in the adhesive, while an increase in other parameters generally results in a negligible reduction in peel stress. The effect of stitching was found to be negligible on the shear stresses in the adhesive. Thus it is concluded that stitching is effective for the joints where peel stresses are critical and ineffective for those where shear stresses are critical. 相似文献
964.
965.
966.
K. A. Taylor J. B. Vander Sande M. Cohen 《Metallurgical and Materials Transactions A》1993,24(11):2585-2588
Y. OHMORI and I. TAMURA:Metall. Trans. A, 1992, vol. 23A, 相似文献
967.
Studies of the crystal chemistry of nonsuperconducting PrBa2Cu3O7 indicate that this compound is strictly isostructural with its superconducting RBa2Cu3O7 (R = Y, rare earth) analogs. Crystallographically, Pr is present in the trivalent state according to the structural trends exhibited by the RBa2Cu3O7 series as a function of R3+ ionic radius. The sole structural anomaly attributable to the presence of Pr3+ in the YBa2Cu3O7 structure is a next-next-nearest neighbor effect and consists of an unusually short axial Cu-O distance, i.e., a short bond length between the in-plane copper and the chain oxygen. The correlation of this anomaly with the nonmetallic/nonsuperconducting properties of PrBa2Cu3O7 supports a variety of literature reports, both theoretical and experimental, suggesting that the apical oxygen in the YBa2Cu3O7 structure plays a critical role in mediating the appearance of superconductivity. The mechanism by which the f-electrons in Pr3+ (f 2) interact with the Cu-O manifold to produce the nonmetallic behavior of PrBa2Cu3O7 remains unknown; however, superconductivity is “turned back on” for Nd3+ (f 3), immediately next to Pr and just slightly smaller. Careful comparative studies of superconducting NdBa2Cu3O7 and nonmetallic PrBa2Cu3O7 are needed to elucidate the critical difference in the behavior of the f-electrons and may shed light on the fundamental mechanism of high-temperature superconductivity in copper oxides. 相似文献
968.
S Saito M Izumitani R Shiroki K Ishiguro T Fujioka I Nagakubo 《Canadian Metallurgical Quarterly》1994,85(12):1777-1780
A 31-year-old man came to our hospital complaining of severe voiding pain. He had inserted a fishing line made of nylon into his urethra at the age of eighteen, which was unable to be taken out and had been left there for 13 years. Preoperative ultrasonogram showed severe bilateral hydronephrosis and the serum BUN and creatinine level were as high as 45.2 mg/dl and 4.8 mg/dl, respectively. A huge bladder stone was demonstrated in X-ray film, the patient was admitted and vesicolithotomy was performed. The size of the stone was 10.5 x 7.5 x 7.5 cm and the weight was 360 grams. The fishing line was found inside the stone and the length was over 3 meters. The serum BUN and creatinine level after the operation were still high as 28.4 mg/dl and 4.1 mg/dl, respectively, and they did not improve even after six months following. 相似文献
969.
S Murakami T Igarashi T Yuhiki T Tobe K Mikami S Akimoto J Shimazaki O Matsuzaki 《Canadian Metallurgical Quarterly》1994,85(8):1213-1217
In order to evaluate the significance of repeat transurethral resection (TUR) in differentiating stage A1 prostatic adenocarcinoma from those with stage A2, we performed repeat TUR in 34 patients with an initial diagnosis of stage A1 prostatic adenocarcinoma. It was found that residual adenocarcinoma was present in five cases (14.7%), but the diagnosis was changed from stage A1 to stage A2 in only one case (2.9%). In one patient with final diagnosis of stage A1 carcinoma, bone metastases were detected seven months after the repeat TUR. It was concluded that repeat TUR for stage A1 prostatic adenocarcinoma did not yield clinically significant information. 相似文献
970.
Mita T. Hirata M. Murata K. Zhang H. 《Industrial Electronics, IEEE Transactions on》1998,45(3):488-495
In the motion control field, a disturbance observer-based disturbance canceling control is often used as a robust control methodology. However, this method is nothing more than an alternative design of an integral controller, and the robust stability issue cannot be directly accounted for. In this paper, an extended H∞ control scheme is proposed as a new robust motion control method which achieves the disturbance cancellation ability and guarantees robust stability automatically 相似文献