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1.
Amer Ibrahim Al-Omari Ibrahim M. Almanjahie Amal S. Hassan Heba F. Nagy 《计算机、材料和连续体(英文)》2020,64(2):835-857
In reliability analysis, the stress-strength model is often used to describe the life of
a component which has a random strength (X) and is subjected to a random stress (Y). In this
paper, we considered the problem of estimating the reliability R=P [Y<X] when the
distributions of both stress and strength are independent and follow exponentiated Pareto
distribution. The maximum likelihood estimator of the stress strength reliability is calculated
under simple random sample, ranked set sampling and median ranked set sampling methods.
Four different reliability estimators under median ranked set sampling are derived. Two
estimators are obtained when both strength and stress have an odd or an even set size. The
two other estimators are obtained when the strength has an odd size and the stress has an
even set size and vice versa. The performances of the suggested estimators are compared
with their competitors under simple random sample via a simulation study. The simulation
study revealed that the stress strength reliability estimates based on ranked set sampling and
median ranked set sampling are more efficient than their competitors via simple random
sample. In general, the stress strength reliability estimates based on median ranked set
sampling are smaller than the corresponding estimates under ranked set sampling and simple
random sample methods. 相似文献
2.
M. A. Amer D. B. Kupranycz B. E. Baker 《Journal of the American Oil Chemists' Society》1985,62(11):1551-1557
Both summer and winter butterfats were fractionated using a laboratory procedure which was designed to simulate a commercial
fractionation process. The process is based on a slow, controlled cooling of the melted fat, a short stabilization time at
the fractionation temperature, and separation of the crystals from the liquid oil by vacuum filtration using a stainless steel
perforated disc. Fractionation temperatures of 29, 26, 23 and 19 C for winter butterfat and 29 and 19 C for summer butterfat
were used to obtain solid and liquid fractions at each temperature. Three replications at each temperature showed good reproducibility
of results. The fractions were characterized by their fatty acid and triglyceride compositions, melting and crystallization
behavior, iodine value, peroxide value and melting point.
Presented at the AOCS meeting in Philadelphia in May 1985. 相似文献
3.
Interfacial hybridization kinetics of oligonucleotides immobilized onto fused silica surfaces 总被引:3,自引:0,他引:3
Jiang Zeng Amer Almadidy James Watterson Ulrich J. Krull 《Sensors and actuators. B, Chemical》2003,90(1-3):68-75
Fused silica optical fibers have been used in an intrinsic mode optical configuration as biosensors for fluorescence based detection of hybridization of nucleic acids. In this work, the kinetics of hybridization of single-stranded oligonucleotides that were covalently immobilized were studied. The probe DNA was dT20, and the target was Fluorescein-labeled non-complementary (dT20) or complementary (dA20) oligonucleotide. Chronofluorimetric monitoring of the adsorption and hybridization processes was used to investigate oligonucleotide films of different density, in different salt concentrations, at temperatures of 25 and 40 °C, with the concentration of the target DNA being 0.005–0.1 μM. Mathematical models based on first- and second-order Langmuir adsorption have been examined to describe both the adsorption and the hybridization processes. Experimental data were processed using the models, and the hybridization kinetics were calculated. Hybridization kinetics on these optical fiber DNA sensors was found to be up to three orders faster than results presented for a number of other experiments using different immobilization chemistries. 相似文献
4.
The dielectric constant, ε′, and dielectric loss, ε″, were determined for three solid carboxymethyl cellulose samples having different levels of substitution and different degrees of polymerization over a frequency range of 0.1 – 10 000 kHz at temperatures from 10–60°C. In contrast to the two relaxation processes, γ and β, previously observed in native cotton cellulose, only one relaxation process within a frequency range of 0.1 – 1 kHz was identified. It was found that the dielectric properties do not only depend on the degree of substitution, but also on the weight-average degree of polymerization and uniformity of distribution. 相似文献
5.
Stress Heterogeneity Effect on the Strength of Silicon Nitride 总被引:1,自引:0,他引:1
François Hild Elisabeth Amer Didier Marquis 《Journal of the American Ceramic Society》1992,75(3):700-702
The experiments reported in this paper demonstrate the causes of the failure of monolithic ceramics. The specimens are made of silicon nitride and tested at room temperature. The stress field within the specimen is different for each of four series of tests that have been conducted. Fractographic observations have also been made to identify the causes of the failures. A size effect analysis is performed. 相似文献
6.
S. E. Shalaby N. G. Al-Balakocy M. K. Beliakova O. M. Abdel-Fatah A. M. Elshafei 《应用聚合物科学杂志》2008,109(2):942-950
An effective two-stage method has been developed for imparting antimicrobial properties to regular polyethylene terephthalate (R-PET), polyethylene glycol modified polyethylene terephthalate (PEG-M-PET), R-PET/Cotton blend (R-PET/C) and PEG-M-PET/Cotton blend (PEG-M-PET/C) fabrics. The method consists of partial hydrolysis of the fabrics to create carboxylic groups in PET macromolecules followed by subsequent reaction with dimethylalkylbenzyl ammonium chloride (DMABAC) under alkaline conditions. The reaction conditions such as pH, reaction temperature and time, carboxylic content, and DMABAC concentration were studied. Characterization of the finished fabrics was carried out through scanning electron microscopy (SEM) and Fourier transform infrared spectra (FTIR). All the modified PET fabrics showed excellent antibacterial activity towards Gram-positive (Bacillus mycoides), Gram-negative (Escherichia coli), and nonfilamentous fungus (Candida albicans). The achieved antimicrobial functions on the PET fabrics are durable in repeated laundering processes. Even after laundering 10 times the fabrics could still provide more than 85% of its antimicrobial activity against B. mycoides, E. coli, and C. albicans. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
7.
This paper describes the design and implementation of a wideband merged LNA and mixer chip covering the frequency range from 0.1 to 3.85 GHz using 90-nm CMOS technology. Its high level of integration as well as its low power consumption makes it suitable for the rapidly growing software defined radio RF receivers. The chip performance achieves S11 below -10 dB along the entire band and a minimum single side band noise figure of 8.4 dB at IF frequency of 70 MHz. Power conversion gain is measured to be 12.1 dB while the input referred 1 dB compression point is measured to be -12.8 dBm. The chip core consumes only 9.8 mW from a 1.2 V supply with a die area, including the pads, of 0.88 mm2 相似文献
8.
M. H. El-Fouly A. F. Maged H. H. Amer M. A. Morsy 《Journal of Materials Science》1990,25(4):2264-2266
Temperature-induced transformations are considered to be interesting characteristic properties of amorphous materials including the Si
x
Te60–x
As30Ge10 system, withx=5, 10, 12 and 20. Density (), X-ray diffraction and differential thermal analysis (DTA) were used to characterize the compositions. DTA traces of each glass composition at different heating rates from 5 to 30° C min–1 were obtained and interpreted. Fast and slow cooling cycles were used to determine the rate of structure formation. Cycling studies of materials show no memory effect but only ovonic switching action. The compositional dependence of the crystallization activation energy (E) and the coefficient of glass-forming tendency (K
gl) have been calculated. The thermal transition temperatures and associated changes in specific heat have been examined as a function of the Te/Si ratio by differential scanning calorimetry. It was found that andE increase linearly with increasing tellurium content, while the heat capacity (c
p) andK
gl, decrease with increasing tellurium content.E=1.54 eV andc
p=0.246 J g–1 K–1 forx=20 whileE=2.74eV andc
p=0.22 J g–1 K–1 forx=5. 相似文献
9.
M. H. El-Fouly A. M. Morsy A. H. Ammar A. F. Maged H. H. Amer 《Journal of Materials Science》1989,24(7):2444-2448
The effect of composition on amorphous chalcogenide threshold switches of the system Si
x
Te60-x
As30Ge10, wherex = 5, 10, 12 and 20, has been studied. The compositionx = 5 shows the best switching characteristics, e.g. the smallest holding voltage (V
h = 0.4V), the highest ON state current (I
h = 45A) and smallest threshold voltage (V
s = 1.5V). Applying the three mechanisms of conductance of Mottet al. (Phil. Mag.
37 (1975) 961), it is found that for a particular composition
2 <
1 <
0 (the pre-exponential factors) andW
2 < (E
a –E
1 +W
1) < (E
c –E
f) (whereE
a,E
c andE
e = activation energies at band edge, fermi level and conduction band;W
1 andW
2 = activation energy for hopping). It was found that the density of states at the fermi levelN(E
f) increases with the decrease of silicon content. The results provided further evidence against thermal interpretations and thereby support electronic models of threshold switching for these glass systems. 相似文献
10.
A. Hebeish N. Y. Abou-Zeid E. El-Kharadly S. E. Shalaby E. A. El-Alfy S. H. Abdel-Fattah A. M. Bayazeed H. Nasr 《应用聚合物科学杂志》1983,28(3):1179-1193
Fabric samples of polyester/cotton blend were graft copolymerized to different levels (add-ons) with poly(acrylic acid) and poly(methacrylic acid) using the mutual γ-irradiation technique and the Fe2+–H2O2 redox system, respectively. The copolymers so obtained were given durable press treatments with and without conventional nonionic softener using DMDEU as the crosslinking agent. The susceptibility of the copolymers before and after crosslinking to aqueous and nonaqueous oily soiling and their ability to release the soils were examined. It was found that hydrophilization of the surface of polyester/cotton blend through grafting with the said carboxyl-containing polymers brings about a significant improvement in the resistance of the blend to aqueous and nonaqueous oily soil particularly after crosslinking in presence of nonionic softener. A certain improvement in the ease of oily soil removal could be achieved by grafting. The opposite holds true for aqueous soil release. Soiling and soil release depends on the magnitude and method of grafting, medium of soiling, as well as the formulation of crosslinking treatments. The effect of grafting on some properties of the blend fabric before and after crosslinking was also examined. 相似文献