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排序方式: 共有90条查询结果,搜索用时 15 毫秒
11.
SW Sakr N Attia M Haourigui JL Paul T Soni D Vacher A Girard-Globa 《Canadian Metallurgical Quarterly》1997,77(1):19-31
This paper outlines the demographic characteristics of the Baiga tribe, one of the most primitive of the aboriginal tribal groups of Central India. The Baiga population has grown steadily since the first anthropological study of the tribe in the 1930s. Age at menarche, age at marriage, breast-feeding, and time interval between marriage and first conception are natural. There are more females than males. Sub-tribe endogamy is common; consanguineous marriage is favoured (34% of marriages are between first cousins) and marital distance is low (mean 7.1 km). Though the mean menarcheal age is high (15.2 years), mean age at first marriage is low (16.6 years), giving a long reproductive period. 相似文献
12.
Acta Informatica - We present an algorithm for solving two-player safety games that combines a mixed forward/backward search strategy with a symbolic representation of the state space. By combining... 相似文献
13.
A laboratory study was performed to investigate the impact of the concentration of pollutants in the air on emissions from building materials. Building materials were placed in ventilated test chambers. The experimental set-up allowed the concentration of pollution in the exhaust air to be changed either by diluting exhaust air with clean air (changing the dilution factor) or by varying the area of the material inside the chamber when keeping the ventilation rate constant (changing the area factor). Four different building materials and three combinations of two or three building materials were studied in ventilated small-scale test chambers. Each individual material and three of their combinations were examined at four different dilution factors and four different area factors. An untrained panel of 23 subjects assessed the air quality from the chambers. The results show that a certain increase in dilution improves the perceived air quality more than a similar decrease in area. The reason for this may be that the emission rate of odorous pollutants increases when the concentration in the chamber decreases. The results demonstrate that, in some cases the effect of increased ventilation on the air quality may be less than expected from a simple dilution model. 相似文献
14.
Samah M S El‐Shafei Sally S Sakr Nagwa H I Abou‐Soliman 《International Journal of Dairy Technology》2020,73(1):126-133
This study investigated the impact of supplementing goats' milk with quinoa extracts, in the range of 5, 10 and 15 g/100 g on the milk fermentation. The properties of yoghurt produced from this milk, which include viscosity, microstructure and sensory acceptability, were assessed. The supplementation of goats' milk with quinoa extracts, particularly permeate extract, reduced the fermentation time and enhanced the viability of lactic acid bacteria. Supplementation of yoghurt with increased levels of quinoa extracts increased the apparent viscosity and changed the yoghurt protein matrix. Panellists highly accepted the yoghurt that contained quinoa permeate extract. 相似文献
15.
Study the effect of recycled pressurized air on oxygen transfer design parameters in sequencing batch reactor technology
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Hesham M. Elkaramany Amro A. Elbaz Amal N. Mohamed Alhassan H. Sakr 《Water and Environment Journal》2017,31(1):90-96
Aeration process consumes more than 60% of the total energy required for wastewater treatment. The present study aims to save power consumption within wastewater treatment aeration process through recycling of the air flow. A new technique of aeration is used to increase oxygen transfer efficiency via exploiting recycled pressurized air. A pilot plant has been constructed to study the effect of using recycled pressurized air within sequencing batch reactor (SBR) model. The results showed that the new technique comparing with the conventional SBR model improved Standard oxygen transfer rate (SORT), Standard oxygen transfer efficiency (SOTE) and Standard aeration efficiency (SAE). In particular, the new technique enhanced (SAE) with 10 and 4% at gauge pressure values 0.5 atm. and 2 atm. respectively. On the other hand, intermittent aeration enhanced (SAE) with 15 and 5% at gauge pressure values 0.5 atm. and 2 atm. respectively. 相似文献
16.
17.
I.S. Yahia M. FadelG.B. Sakr F. Yakuphanoglu S.S. ShenoudaW.A. Farooq 《Journal of Alloys and Compounds》2011,509(12):4414-4419
The polycrystalline ZnGa2Se4 thin film was prepared by thermal evaporation technique on n-Si wafer followed by annealing at 700 K. Then, the Al/p- ZnGa2Se4/n-Si/Al heterojunction diode was fabricated. XRD pattern shows that the annealed ZnGa2Se4 film has a polycrystalline structure. AFM images indicate that the ZnGa2Se4 film is formed of nanoparticles. The dark current-voltage characteristics of the heterojunction diode at various temperatures have been investigated to determine the electrical parameters and conduction mechanism. The Al/p-ZnGa2Se4/n-Si/Al diode shows a rectification ratio of 2.644 × 102 at ±2 V at room temperature. It was found that at forward bias voltages ≤0.5 V, the conduction mechanism of the diode is controlled by the thermionic emission mechanism, while at bias voltages higher than 0.5 V, it is controlled by the space charge limited current mechanism. The series resistance Rs, the ideality factor n and the barrier height ?b values of the diode are determined by performing different plots from the forward current-voltage characteristics. The reverse current mechanism of the diode is controlled by the carrier generation-recombination process in the depletion region. The obtained results show that the Al/p-ZnGa2Se4/n-Si/Al heterojunction is a good candidate for the electronic device applications. 相似文献
18.
Sensory evaluations were used to investigate the impact of sorption processes on indoor air quality. Experiments were carried out in four similar, adjacent, unfurnished offices. Samples of carpet, linoleum, painted gypsum board, and Semia (a specially designed high-sorbing fabric) were tested individually and in combination. Additionally, to investigate the interaction between the pollutants emitted from the building materials and the test room surfaces themselves, air streams polluted by two different building materials were vented into an empty test office. Each experiment lasted for either 1 week (adsorption stage only) or 10 days (adsorption and desorption stages). Untrained panels assessed the air quality at specified times after moving the materials into or out of the rooms. The results showed that, in comparison with air in a room with carpet or linoleum alone, the presence of painted gypsum board improved the perceived air quality. This improvement persisted throughout the 168 h of the 'adsorption stage' of the experiments. A mass balance model was used to quantify the improvement. Calculated results indicate that, for the conditions used in these experiments, pollutant removal via sorption to the relatively inert office surfaces was equivalent to an extra 0.4 air change per hour (ACH) of ventilation air, while sorption to painted gypsum board surfaces was equivalent to an extra 1-7 ACH of ventilation air. In the case of Semia, sorption was equivalent to an extra 16 ACH of ventilation air. During the 'desorption stage' of the experiments, after carpet or linoleum were taken out of a room, approximately 3 days were required before the air in the test office, ventilated at 0.8 ACH, was judged to be free of the sorbed pollutants. PRACTICAL IMPLICATIONS: Ventilation rates in non-industrial buildings are based largely on sensory pollution sources and a desired level of perceived air quality. This study documents that sorptive materials in a room influence the perceived air quality and should be considered when evaluating ventilation requirements. Indeed, it may be possible to deliberately use sorption/desorption to improve indoor air in a manner analogous to the way thermal storage/release is currently used in buildings as a means of conserving energy. 相似文献
19.
Optoelectronic buses for high-performance computing 总被引:2,自引:0,他引:2
Chiarulli D.M. Levitan S.P. Melhem R.G. Bidnurkar M. Ditmore R. Gravenstreter G. Zicheng Guo Chungming Qiao Sakr M.F. Teza J.P. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1994,82(11):1701-1710
Modern computer buses are typically organized by the three functions of data transfer, addressing, and arbitration/control. In this paper we present a fiber-based bus design which provides optical solutions for each of these functions. The design includes an all-optical addressing system, based on coincident pulse addressing, which eliminates the latency contribution and bandwidth limitation associated with electronic address decoding. The control system uses time-of-flight relationships between a priority chain and a feedback waveguide to implement fully distributed asynchronous and self-timed bus arbitration 相似文献
20.
Elias Warde Salam Sakr Maria Tchernycheva Francois Henry Julien 《Journal of Electronic Materials》2012,41(5):965-970
Using the transfer matrix formalism, we have theoretically studied the vertical ballistic transport in GaN/AlGaN resonant
tunneling diodes (RTDs) and superlattices with a small number of periods. We have calculated the transmission probability
versus the longitudinal electron energy (T–E) and the current density–voltage (J–V) characteristics. Calculations of both T–E and J–V characteristics have been performed for different Al contents in the barriers. The asymmetry effects due to the internal
electric field in the barriers are discussed. Applied to the RTD structure, our calculations demonstrate: (i) the increase
of the peak-to-valley ratio of the negative differential resistance (NDR) with increasing Al content in the barriers, (ii)
the dependence of the J–V resonance values on the current direction, and (iii) the asymmetry of the NDR with respect to the current direction due to
the huge internal electric field in the structure. In the case of multiple quantum well structure (MQWS), the calculation
results confirm the same trends as in the RTD case when the Al content is varied. In spite of the fact that it is more difficult
to analyze the results in the case of MQWS, the obtained calculations demonstrate the applicability of the used model and
of the numerical method to study GaN/AlGaN devices based on quantum well (QW) heterostructures. Furthermore, a design of an
optimized 7QW structure operating symmetrically whatever the direction of the applied voltage is presented. 相似文献