排序方式: 共有44条查询结果,搜索用时 818 毫秒
31.
Neville de Mestre Ted Catchpole 《International Journal of Mathematical Education in Science & Technology》2013,44(1):155-164
The kinematics of a projectile in flight provides an ideal opportunity for an introduction to (and a comparison between) discrete and continuous methods in applied mathematics. We use a graphical method in the discrete approach, which provides good physical insight and serves as an introduction to finite difference methods. The continuous approach is better in the no‐drag case, but the discrete approach is foundto be more effective when a nonlinear drag effect is included in the model. 相似文献
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J. Calbo A. Mestre A. Garcia M.A. Tena M. Llusar G. Monros 《Journal of Sol-Gel Science and Technology》2003,26(1-3):191-194
Ferrites and chromites of Ni and Co synthesised by solid reaction method are usually used as black colour ceramic pigments. Due to the presence of Co and Ni in their composition they are classified as harmful substances. In this work, Co, Cr and Fe have been partially substituted by harmless Mg and Al ions, and the optimised compositions have also been synthesised by coprecipitation and gel polymeric route. Samples obtained have been characterised by CIEL*a*b colour parameters, XRD, DTA-TG, and SEM-EDAX techniques. Samples obtained by gel polymeric route presents the best reactivity and black colouring results. 相似文献
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Jorge Pérez‐Chamorro Cyril Lahuec Fabrice Seguin Gérald Le Mestre Michel Jézéquel 《ETRI Journal》2009,31(5):585-592
This paper presents a method for decoding high minimal distance (dmin) short codes, termed Cortex codes. These codes are systematic block codes of rate 1/2 and can have higher dmin than turbo codes. Despite this characteristic, these codes have been impossible to decode with good performance because, to reach high dmin, several encoding stages are connected through interleavers. This generates a large number of hidden variables and increases the complexity of the scheduling and initialization. However, the structure of the encoder is well suited for analog decoding. A proof‐of‐concept Cortex decoder for the (8, 4, 4) Hamming code is implemented in subthreshold 0.25‐μm CMOS. It outperforms an equivalent LDPC‐like decoder by 1 dB at BER=10?5 and is 44 percent smaller and consumes 28 percent less energy per decoded bit. 相似文献
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Dr. Mingjun Xuan Rafael Mestre Dr. Changyong Gao Chang Zhou Prof. Qiang He Prof. Samuel Sánchez 《Angewandte Chemie (International ed. in English)》2018,57(23):6838-6842
We report a carbonaceous nanobottle (CNB) motor for near infrared (NIR) light‐driven jet propulsion. The bottle structure of the CNB motor is fabricated by soft‐template‐based polymerization. Upon illumination with NIR light, the photothermal effect of the CNB motor carbon shell causes a rapid increase in the temperature of the water inside the nanobottle and thus the ejection of the heated fluid from the open neck, which propels the CNB motor. The occurrence of an explosion, the on/off motion, and the swing behavior of the CNB motor can be modulated by adjusting the NIR light source. Moreover, we simulated the physical field distribution (temperature, fluid velocity, and pressure) of the CNB motor to demonstrate the mechanism of NIR light‐driven jet propulsion. This NIR light‐powered CNB motor exhibits fuel‐free propulsion and control of the swimming velocity by external light and has great potential for future biomedical applications. 相似文献
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J-F. Mestre 《Israel Journal of Mathematics》1998,107(1):333-341
We prove that 6A
6 and 6A
7 are Galois groups of regular extensions ofQ(t), therefore of infinitely many extensions ofQ.
相似文献
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Insertion of Isocyanides into N−Si Bonds: Multicomponent Reactions with Azines Leading to Potent Antiparasitic Compounds
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Kranti G. Kishore Ouldouz Ghashghaei Dr. Carolina Estarellas M. Mar Mestre Cristina Monturiol Dr. Nicola Kielland Prof. John M. Kelly Dr. Amanda Fortes Francisco Shiromani Jayawardhana Prof. Diego Muñoz‐Torrero Prof. Belén Pérez Prof. F. Javier Luque Prof. Rocío Gámez‐Montaño Prof. Rodolfo Lavilla 《Angewandte Chemie (International ed. in English)》2016,55(31):8994-8998
Trimethylsilyl chloride is an efficient activating agent for azines in isocyanide‐based reactions, which then proceed through a key insertion of the isocyanide into a N?Si bond. The reaction is initiated by N activation of the azine, followed by nucleophilic attack of an isocyanide in a Reissert‐type process. Finally, a second equivalent of the same or a different isocyanide inserts into the N?Si bond leading to the final adduct. The use of distinct nucleophiles leads to a variety of α‐substituted dihydroazines after a selective cascade process. Based on computational studies, a mechanistic hypothesis for the course of these reactions was proposed. The resulting products exhibit significant activity against Trypanosoma brucei and T. cruzi, featuring favorable drug‐like properties and safety profiles. 相似文献
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Smart antennas in software radio base stations 总被引:1,自引:0,他引:1
The application of adaptive antenna techniques to fixed-architecture base stations has been shown to offer wide-ranging benefits, including interference rejection capabilities or increased coverage and spectral efficiency. Unfortunately, the actual implementation of these techniques to mobile communication scenarios has traditionally been set back by two fundamental reasons. On one hand, the lack of flexibility of current transceiver architectures does not allow for the introduction of advanced add-on functionalities. On the other hand, the often oversimplified models for the spatiotemporal characteristics of the radio communications channel generally give rise to performance predictions that are, in practice, too optimistic. The advent of software radio architectures represents a big step toward the introduction of advanced receive/transmit capabilities. Thanks to their inherent flexibility and robustness, software radio architectures are the appropriate enabling technology for the implementation of array processing techniques. Moreover, given the exponential progression of communication standards in coexistence and their constant evolution, software reconfigurability will probably soon become the only cost-efficient alternative for the transceiver upgrade. This article analyzes the requirements for the introduction of software radio techniques and array processing architectures in multistandard scenarios. It basically summarizes the conclusions and results obtained within the ACTS project SUNBEAM, proposing algorithms and analyzing the feasibility of implementation of innovative and software-reconfigurable array processing architectures in multistandard settings 相似文献
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M. García-Gabaldn V. Prez-Herranz E. Snchez S. Mestre 《Journal of membrane science》2006,280(1-2):536-544
Different microporous ceramic membranes have been investigated to be used as separators in electrochemical reactors. The effect of porosity on the effective electrical conductivity of the ceramic membranes has been studied. The porosity of the membranes has been modified by changing the manufacturing pressure and by the addition of starch to the alumina–kaolin matrix. In the absence of starch the pore size distribution becomes more uniform with the increase of the manufacturing pressure, and lower porosities and average pore sizes are obtained. On the other hand, the porosity and the average pore size increase with the addition of starch to the alumina–kaolin matrix, but pore size distribution is less uniform and becomes bimodal with two different characteristic pore diameters.
The effective electrical conductivity of the membranes, κeff, increases with the decrease of manufacturing pressure and with the increase of starch content. The following correlation between the effective electrical conductivity and the porosity has been obtained: fc = κeff/κ = 0.35 1.04, where κ is the electrolyte electrical conductivity. 相似文献
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