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191.
Equations are proposed for the instantaneous and average power input and for the forces acting on various parts of vibrating-plate and pulsed columns. The inertia and friction forces are separated on assumption that in the practical range of frequencies the instantaneous friction forces are equal to those under the steady flow at the same velocity. Two experimental methods are used: the measurement of pressure pulsations near the bottom of the column using a capacity probe, and the measurement of forces acting on the rod connecting the plates to the eccentric by means of a tensiometer. A relation between these quantities is derived and its validity proved experimentally. Processing of the signals of the two transducers is described and the differences in dynamic behaviour of vibrating-plate and pulsed columns discussed. 相似文献
192.
Fernando Vidal-Verdú Moustapha Hafez 《IEEE transactions on neural systems and rehabilitation engineering》2007,15(1):119-130
This paper presents an up-to-date survey of graphical tactile displays. These devices provide information through the sense of touch. At best, they should display both text and graphics (text may be considered a type of graphic). Graphs made with shapeable sheets result in bulky items awkward to store and transport; their production is expensive and time-consuming and they deteriorate quickly. Research is ongoing for a refreshable tactile display that acts as an output device for a computer or other information source and can present the information in text and graphics. The work in this field has branched into diverse areas, from physiological studies to technological aspects and challenges. Moreover, interest in these devices is now being shown by other fields such as virtual reality, minimally invasive surgery and teleoperation. It is attracting more and more people, research and money. Many proposals have been put forward, several of them succeeding in the task of presenting tactile information. However, most are research prototypes and very expensive to produce commercially. Thus the goal of an efficient low-cost tactile display for visually-impaired people has not yet been reached. 相似文献
193.
Abdel Hamid Harhash Mohamed Hilmy Elnagdi Ebtisam Abdel Aziz Hafez 《Advanced Synthesis \u0026amp; Catalysis》1971,313(4):706-714
Treatment of 4-arylazo-2-alkoxy-2-thiazolin-5-ones 4a – f with glycine or phenylhydrazine effects their conversion into 1-aryl-5-alkoxy-1 H-1,2,4-triazole-3-carboxylic acid derivatives 5a – j , with the loss of hydrogen sulfide. On the other hand, the reaction of the 2-ethoxy ( 4a – c ) and the 2-isopropyloxy ( 4g – i ) derivatives with strong basic amines involves the loss of an alkyl mercaptan to yield the N-substituted amines 7d – j of 1-aryl-Δ2-1,2,4-triazolin-5-one-3-carboxylic acids. The 2-benzyloxy derivatives 4d – f react with the same reagents to give the N-substituted amides 2a – g of 1-aryl-Δ2-1,2,4-triazolin-5-thione-3-carboxylic acids, with the loss of benzyl alcohol. Hetero-ring opening of 4 , followed by recyclisation, occurs upon treatment with ethyl or phenyl magnesium halides to yield the triazolinethione derivatives 13 a – c . 相似文献
194.
Hafez R. S. Ramadan Rania El-Khiyami S. S. 《Journal of Materials Science: Materials in Electronics》2021,32(11):14557-14568
Journal of Materials Science: Materials in Electronics - This research deals with structural, optical, electrical, and magnetic properties of nanocomposite composed of polymethyl methacrylate... 相似文献
195.
Objective: To describe Philip Morris'' global market research and international promotional strategies targeting young adults. Methods: : Analysis of previously secret tobacco industry documents. Results: Philip Morris pursued standardised market research and strategic marketing plans in different regions throughout the world using research on young adults with three principle foci: lifestyle/psychographic research, brand studies, and advertising/communication effectiveness. Philip Morris identified core similarities in the lifestyles and needs of young consumers worldwide, such as independence, hedonism, freedom, and comfort. In the early 1990s Philip Morris adopted standardised global marketing efforts, creating a central advertising production bank and guidelines for brand images and promotions, but allowing regional managers to create regionally appropriate individual advertisements. Conclusions: Values and lifestyles play a central role in the global marketing of tobacco to young adults. Worldwide counter marketing initiatives, coupled with strong, coherent global marketing policies such as the Framework Convention on Tobacco Control, are needed to break associations between young adult values and tobacco brands. As globalisation promotes the homogenisation of values and lifestyles, tobacco control messages that resonate with young adults in one part of the world may appeal to young adults in other countries. Successful tobacco control messages that appeal to young people, such as industry denormalisation, may be expanded globally with appropriate tailoring to appeal to regional values. 相似文献
196.
MG el-Sayed MR Hassanin MH Hafez AA el-Komy A Mohamed 《Canadian Metallurgical Quarterly》1997,104(11):481-487
The pharmacodynamic and nephrotoxic effects of cefamandole were investigated. Cefamandole at concentrations of 512 and 1024 micrograms/ml bath caused complete relaxation in isolated guinea pig ileum and rabbit duodenum, respectively. Concentrations of 2048 and 4096 micrograms cefamandole/ml bath caused marked stimulation in force and frequency of rat uterine muscle in all stages of sex cycle. Cefamandole in all tested concentrations did not induce any response on isolated guinea pig tracheal chain or isolated rabbit aortic strip. Cefamandole in concentrations of 256 to 1024 micrograms/ml bath as well as 256 and 512 micrograms/ml cannula produced marked inhibition on isolated guinea pig auricles and rabbit heart, respectively. The effect of graded increased concentrations on isolated frog gastrocnemius muscle, frog rectus abdominis muscle and rat phrenic nerve hemidiaphragm was recorded. Cefamandole in a dose of 53.2 mg/kg b. wt. in anaesthetized dogs caused very marked hypotensive effects and decrease in rate of respiration. Single intramuscular injection of cefamandole in a therapeutic (23.3 mg/kg b. wt.) and double therapeutic (46.6 mg/kg.b. wt.) doses in rabbits had no effect on electrocardiographic parameters among a period of 8 hours after injection. Effects of cefamandole on serum and urine concentrations of creatinine, urea, sodium, potassium, calcium, glucose and protein as well as clearance tests were investigated in rats. 相似文献
197.
El-Khiyami S. S. Ismail A. M. Hafez R. S. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(11):4313-4325
Journal of Inorganic and Organometallic Polymers and Materials - Different concentrations of nickel oxide (NiO) nanoparticles were successfully inserted into polystyrene (PS) polymer matrix using... 相似文献
198.
Susana Iglesias-Groth Yaser Hafez 《Fullerenes, Nanotubes and Carbon Nanostructures》2016,24(9):547-554
C60 and C70 fullerenes were neutron-bombarded to an integral dose of 3.28×1016 n cm?2. After the neutron treatment the trichloromethane soluble fraction was determined spectrophotometrically and C60 insoluble fraction was found at 3.8% while the insoluble fraction of C70 17.9%. The formation of the CHCl3 insoluble fraction is due to polymerization and incipient amorphization of the neutron-bombarded fullerenes where C70 appears more sensitive to radiation damage than C60. Raman spectroscopy was used for the characterization of the irradiated fullerenes as well as electron spin resonance (ESR) and electronic absorption spectroscopy on solid samples. Differential scanning calorimetry (DSC) to 630°C was employed for the determination of the Wigner energy of the neutron-damaged fullerenes. The results are consistent with a higher level of radiation damage reached by C70 in comparison to C60 at the same neutron dose. 相似文献
199.
G.H. Ibrahim A. Hafez A.H. Khalil 《AEUE-International Journal of Electronics and Communications》2013,67(11):967-974
An original proposal of using SRO-based receiver to demodulate QPSK signals is presented. The receiver is composed of an LNA and a super-regenerative oscillator (SRO), both combined in a single stacked configuration for current reuse. The demodulation of received RF signal is performed via a novel digital circuit capable of detecting phase information embedded in the SRO output. The receiver is able to demodulate incoming signal without the need of an LO, PLL or an ADC. The complete receiver was designed using a 0.13 μm technology and pre-layout simulation confirms proper and efficient operation, where the designed receiver operating in the 402–405 MHz MICS band shows 135 μW power consumption, while being able to properly detect and extract sent information of a −80 dBm, 2 Mbps signal. 相似文献