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排序方式: 共有133条查询结果,搜索用时 15 毫秒
1.
M. S. Rizk Y. M. Issa M. A. Ahmed S. M. Shaaban 《Journal of Materials Science: Materials in Electronics》1993,4(2):109-112
The charge transfer complexes produced by the reaction between picric acid and some aniline derivatives were prepared. The prepared charge transfer complexes (CTC) were investigated using infrared and nuclear magnetic resonance spectroscopy aiming to throw more light on their molecular structure. It was proved that a proton transfer interaction takes place between PiOH and x-Ph.NH2 leading to the formation of PiO} and x-Ph.NH3
+ ions. The normal -1 electronic interaction takes place by transferring an electron from the aniline ring to the picric acid. The semiconducting properties of the CTC were investigated. All the prepared complexes were proved to have a semiconducting character within the temperature range investigated. 相似文献
2.
AM Attallah H Ismail SA El Masry H Rizk A Handousa M El Bendary A Tabll F Ezzat 《Canadian Metallurgical Quarterly》1999,37(2):354-357
Schistosoma circulating antigens were used to indicate the infection intensity and to assess cure. An immunoglobulin G2a (IgG2a) mouse monoclonal antibody was used in a fast dot-enzyme-linked immunosorbent assay (ELISA; FDA) for rapid and simple diagnosis of schistosomiasis in the field. Seven hundred Egyptians were parasitologically examined for Schistosoma mansoni and other parasitic infections. A rectal biopsy was done as a "gold standard" for individuals showing no S. mansoni eggs in their feces. Egg counts were obtained by the Kato smear method for only 100 of 152 individuals with eggs in their feces. Specific anti-schistosome IgG antibodies were evaluated in sera by ELISA. Urine samples from the 700 individuals were tested by FDA for detection of the circulating antigen. The assay showed a sensitivity of 93% among 433 infected individuals and a specificity of 89% among 267 noninfected individuals. FDA showed the highest efficiency of antigen detection (91%) compared with the efficiency of antibody detection by ELISA (75%) and stool analysis (60%). In addition, FDA detected infected patients with 20 eggs/g of feces. Also, the sensitivity of FDA ranged from 90 to 94% among samples from patients with different clinical stages of schistosomiasis. All the assay steps can be completed within 30 min at room temperature for 96 urine samples. The monoclonal antibody identified a 74-kDa antigen in different antigenic extracts of S. mansoni and Schistosoma haematobium and in the urine of infected individuals. In addition, a 30-kDa degradation product was identified only in the urine samples. On the basis of these results, FDA should be used as a rapid tool for the sensitive and specific diagnosis of Schistosoma infection. 相似文献
3.
This paper presents a simulation study based on actual load, sunshine and wind data. A distribution feeder simulation model was constructed using this data to determine what potential benefit embedded wind, solar and storage elements could give to the distribution network. The results were compared to earlier studies. It was discovered that over the past 5–10 years, the hot weather peak load has extended from 3 pm to 6 pm and that a more northwesterly orientation of solar panels is of assistance. It was also found that wind is of little assistance in hot weather peaks, in contrast to data for the NSW central tablelands region; however solar contributes at least 50% of its nominal peak capacity. As hot weather peaks are now extending into the early evening, it was found that storage would be of great benefit and would enhance the use of renewable energy sources. As part of the feeder model, the optimal method of Var control from the embedded sources was also studied. 相似文献
4.
5.
The unstable conveying zone has been recognized by many authors in their attempts to define the minimum conveying velocitv on the dilute phase side of this zone. It was found that the gas flow rate influences the magnitude and frequency of the pressure fluctuations experienced during this type of flow. Generally a reduction of gas flow rate will reduce both the intensity and frequency of the fluctuations.
During the measurement of data for the previous experiments, it was recognized that the pressure fluctuations of dilute and strand flow can serve as simple indicators of the flow stability. An analysis of these fluctuations is presented, which suggests that simple statistical factors can be used to estimate the system condition of operation with respect to the pressure minimum or unstable zone. These elementary trends in the data can be useful for one attempting to optimize a system. This analysis lead to a more intensive approach using Hurst's rescaled range analysis, to examine the changes in pressure fluctuations, which occur when a system undergoes a simulated optimization procedure. The analysis suggested that Hurst's exponent may be used as an indicator of the onset of instability. 相似文献
During the measurement of data for the previous experiments, it was recognized that the pressure fluctuations of dilute and strand flow can serve as simple indicators of the flow stability. An analysis of these fluctuations is presented, which suggests that simple statistical factors can be used to estimate the system condition of operation with respect to the pressure minimum or unstable zone. These elementary trends in the data can be useful for one attempting to optimize a system. This analysis lead to a more intensive approach using Hurst's rescaled range analysis, to examine the changes in pressure fluctuations, which occur when a system undergoes a simulated optimization procedure. The analysis suggested that Hurst's exponent may be used as an indicator of the onset of instability. 相似文献
6.
7.
For pt.I see ibid., vol.9, no.1, p.162-71 (1994). The present paper comprises an extensive computer investigation of lightning incidence to tall masts, based on a theory presented in part I, for both flat and hilly regions. The investigation covers both downward negative lightning incidence and upward flash from tall masts under negative cloud. The factors investigated include: mast height, statistical distribution of the ground electric field, as well as mountain height and topology. Predicted lightning incidence and probability of upward flash are successfully verified against extensive field observations 相似文献
8.
Abo-el-Enein SA Eissa MA Diafullah AA Rizk MA Mohamed FM 《Journal of hazardous materials》2011,186(2-3):1200-1205
Different samples of rice husk ash (RHA) and sodium silicate were prepared and characterized using FTIR, NFTIR and XRD. The selected sample of RHA was obtained by calcination of untreated rice husk (RH) in a semi-closed system at 650°C. Four novel polyinorganic coagulants were also prepared, namely, poly aluminum chloride silicate, poly hydroxy aluminum sulphate silicate, poly ferric chloride silicate and poly ferric aluminum chloride silicate. Applications were carried out for the removal of some pollutants from ground, sewage and industrial waste waters. It was found that the maximum percentages removal of Fe(2+) and Mn(2+) ions in ground water reached 99 and 97%, respectively, the maximum percentage removal of, Pb(2+) ion in industrial waste water reached 97%. In addition, the maximum percentages removal of COD, BOD and TSS in sewage waste water reached 90, 92, and 93%, respectively. 相似文献
9.
El Khoury A Atoui A Rizk T Lteif R Kallassy M Lebrihi A 《Journal of food science》2011,76(4):M247-M253
Aflatoxins (AFs) represent the most important single mycotoxin-related food safety problem in developed and developing countries as they have adverse effects on human and animal health. They are produced mainly by Aspergillus flavus and A. parasiticus. Both species have different aflatoxinogenic profile. In order to distinguish between A. flavus and A. parasiticus, gene-specific primers were designed to target the intergenic spacer (IGS) for the AF biosynthesis genes, aflJ and aflR. Polymerase chain reaction (PCR) products were subjected to restriction endonuclease analysis using BglII to look for restriction fragment length polymorphisms (RFLPs). Our result showed that both species displayed different PCR-based RFLP (PCR-RFLP) profile. PCR products from A. flavus cleaved into 3 fragments of 362, 210, and 102 bp. However, there is only one restriction site for this enzyme in the sequence of A. parasiticus that produced only 2 fragments of 363 and 311 bp. The method was successfully applied to contaminated grapes samples. This approach of differentiating these 2 species would be simpler, less costly, and quicker than conventional sequencing of PCR products and/or morphological identification. 相似文献
10.
Heba Nashaat Rawya Rizk Hani Mahdi 《International Journal of Wireless Information Networks》2011,18(4):210-223
Mobile IP has been developed to provide the continuous information network access to mobile users. The performance of Mobile
IP mobility management scheme is dependent on traffic characteristics and user mobility. Consequently, it is important to
assess this performance in-depth through these factors. This paper introduces a novel analytical model of handoff management
in mobile IP networks. The proposed model focuses on the effect the traffic types and their frame error rates on the handoff
latency. It is derived based on general distribution of both successful transmission attempts and the residence time to be
applicable in all cases of traffic characteristics and user mobility. The impact of the behavior of wireless connection, cell
residence time, probability distribution of transmission time and the handoff time is investigated. Numerical results are
obtained and presented for both TCP and UDP traffics. As expected, the reliability of TCP leads to higher handoff latency
than UDP traffic. It is shown that, higher values of FER increase the probability of erroneous packet transfer across the
link layer. A short retransmission time leads to end the connection most likely in the existing FA; however a long retransmission
time leads to a large delivery time. The proposed model is robust in the sense that it covers the impact of all the effective
parameters and can be easily extended to any distribution. 相似文献