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排序方式: 共有1134条查询结果,搜索用时 15 毫秒
111.
K. K. Abdullah K. Karunakaran Nair N. Ramachandran K. M. Varier B. R. S. Babu Antony Joseph Rajive Thomas P. Magudapathy K. G. M. Nair 《Pramana》2010,75(3):459-469
Mass attenuation coefficients (μ/ρ) for Zr, Nb, Mo and Pd elements around their K-edges are measured at 14 energies in the range 15.744–28.564 keV using secondary excitation from thin Zr, Nb, Mo, Rh, Pd,
Cd and Sn foils. The measurements were carried out at the K
α
and K
β
energy values of the target elements by two techniques: (1) Proton-induced X-ray emission (PIXE) and (2) 241Am (300 mCi) source. In PIXE, 2 MeV proton-excited X-rays were detected by a Si(Li) detector. In the second case, X-rays excited
by 59.54 keV photons from the targets were counted by an HPGe detector under a narrow beam good geometry set-up with sufficient
shielding. The results are consistent with theoretical values derived from the XCOM package and indicate that the PIXE data
have better statistical accuracy. 相似文献
112.
V. Ramakrishnan A. Sarua M. Kuball A. Fathima Abdullah 《Journal of Raman spectroscopy : JRS》2010,41(3):320-324
The molecular interaction in the binary mixture of 3‐phenoxybenzaldhyde (3Phbz) and 4‐ethoxybenzaldehyde (4Etob) was analysed in four different solvents. The concentration dependence of vibrational relaxation of the CO stretching band of 3Phbz in different solvents was investigated by varying the concentration of the solute molecule in the solvents by performing Raman spectroscopic measurements. The self‐associated nature and the formation of hydrogen‐bonded complexes in the solute molecule, 4Etob, were considered to analyse the wavenumber separation between the peaks of hydrogen‐bonded and free carbonyl groups. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
113.
Phase‐type distribution closure properties are utilized to devise algorithms for generating reliability functions of systems with basic structures. These structures include series, parallel, K‐out‐of‐N, and standby structures with perfect/imperfect switch. The algorithms form a method for system reliability modeling and analysis based on the relationship between the system lifetime and component lifetimes for general structures. The proposed method is suitable for functional system reliability analysis, which can produce reliability functions of systems with independent components instead of only system reliability values. Once the system reliability function is obtained, other reliability measures such as the system's hazard function and mean time to failure can be obtained efficiently using only matrix algebra. Dimensional and numerical comparisons with computerized symbolic processing are also presented to show the superiority of the proposed method. 相似文献
114.
Nuh Aydin Yasemin Cengellenmis Abdullah Dertli 《Designs, Codes and Cryptography》2018,86(6):1249-1255
In this paper, we study \(\lambda \)-constacyclic codes over the ring \(R=\mathbb {Z}_4+u\mathbb {Z}_4\) where \(u^{2}=1\), for \(\lambda =3+2u\) and \(2+3u\). Two new Gray maps from R to \(\mathbb {Z}_4^{3}\) are defined with the goal of obtaining new linear codes over \(\mathbb {Z}_4\). The Gray images of \(\lambda \)-constacyclic codes over R are determined. We then conducted a computer search and obtained many \(\lambda \)-constacyclic codes over R whose \(\mathbb {Z}_4\)-images have better parameters than currently best-known linear codes over \(\mathbb {Z}_4\). 相似文献
115.
116.
117.
Samsul Rizal E. M. Mistar A. A. Oyekanmi Abdul Khalil H.P.S. Tata Alfatah N. G. Olaiya C. K. Abdullah 《Molecules (Basel, Switzerland)》2021,26(14)
The use of chemical modification of cellulosic fibre is applied in order to increase the hydrophobicity, hence improving the compatibility between the fibre and matrix bonding. In this study, the effect of propionic anhydride modification of kenaf fibre was investigated to determine the role of bionanocarbon from oil palm shell agricultural wastes in the improvement of the functional properties of bionanocomposites. The vinyl esters reinforced with unmodified and propionic anhydride modified kenaf fibres bio nanocomposites were prepared using 0, 1, 3, 5 wt% of bio-nanocarbon. Characterisation of the fabricated bionanocomposite was carried out using FESEM, TEM, FT-IR and TGA to investigate the morphological analysis, surface properties, functional and thermal analyses, respectively. Mechanical performance of bionanocomposites was evaluated according to standard methods. The chemical modification of cellulosic fibre with the incorporation of bionanocarbon in the matrix exhibited high enhancement of the tensile, flexural, and impact strengths, for approximately 63.91%, 49.61% and 54.82%, respectively. The morphological, structural and functional analyses revealed that better compatibility of the modified fibre–matrix interaction was achieved at 3% bionanocarbon loading, which indicated improved properties of the bionanocomposite. The nanocomposites exhibited high degradation temperature which signified good thermal stability properties. The improved properties of the bionanocomposite were attributed to the effect of the surface modification and bionanocarbon enhancement of the fibre–matrix networks. 相似文献
118.
The present paper deal with the multi-component condensation of 8-hydroxy quinoline, aromatic aldehydes, and sulfone derivatives catalyzed by p-toluenesulfonic acid for the synthesis of a series of 4H-pyrano[3,2-h]quinoline derivatives in ethanol under ultrasonic irradiations. We provide a series of quinoline derivatives containing sulfone moiety interesting for biological screening tests. The reactions were carried out under both conventional and ultrasonic irradiation conditions. In general, improvement in rates and yields were observed when reactions were carried out under sonication compared with classical silent conditions. Also, also, sonochemical reaction give different reaction pathway other than silent reaction. These remarkable effects appeared in sonicated reactions can be reasonably interpreted in terms of acoustic cavitation phenomenon. Structures of the products were established on analytical and spectral data. 相似文献
119.
We present a high-gain erbium-doped fiber amplifier to be utilized as a preamplifier. A double-pass amplification technique is used in the first-stage amplifier together with a tunable bandpass filter. The secondstage amplifier is a counter-pumped configuration and another tunable bandpass filter is utilized to filter out amplified spontaneous emission from the first-stage amplifier. This design is able to produce a high gain of 55.6 dB and a noise figure of 6.02 dB at 1530 nm with a signal power of ?45 dBm. The receiver sensitivity measurement shows that the proposed amplifier improves the minimum detectable power from ?33.7 to ?40.8 dBm for a bit-error rate of 10?11 at 155 Mbps.
相似文献120.
An efficient method has been developed for the synthesis of 1-(arylimino)naphthalen-2(1H)-ones through the cascade reaction of anilines and 2-naphthols promoted by NaBr/K2S2O8/Ce(NH4)2(NO3)6. Using this protocol, a series of 1-(arylimino)naphthalen-2(1H)-ones was obtained in good to excellent yields (17 examples, 70–92% yields). The reactions may proceed through the following steps: bromination of 2-naphthols by in-situ-generated bromine from NaBr and K2S2O8 to afford 1-bromonaphthalen-2-ols, coupling of 1-bromonaphthalen-2-ols with anilines to afford the corresponding amines, and subsequent oxidation of the amines into the products by Ce(NH4)2(NO3)6. These newly obtained α-imine ketones have great potentials for synthesis of special optical materials bearing naphthalene moiety. 相似文献