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"الإستاتيكا"
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Theoretical study on the reaction mechanism of cyclopropenylidene with cyclic CnH2nO (n=2, 3) compounds: Ring expansion process
The ring expansion reaction mechanisms between cyclopropenylidene and cyclic CnH2nO (n = 2, 3) compounds have been systematically investigated employing the second-order Møller-Plesset perturbation theory (MP2) method in order to better understand the reactivity of cyclopropenylidene with epoxy compounds (oxirane and epoxypropane). Geometry optimizations and vibration analyses have been performed for the stationary points on the potential energy surfaces of the system. The calculated results show that cyclopropenylidene can insert into oxirane at its C－O bond and into epoxypropane at its C－O or C－C bond. From the kinetic viewpoint, it is easier for cyclopropenylidene to insert into the C－O bond of oxirane than that of the C－O bond of epoxypropane. For insertion into epoxypropane, it is easier for cyclopropenylidene to insert into its C－O bond than C－C bond. Through the first insertion step and the second ring-opened step, spiro and carbene intermediates can been formed between cyclopropenylidene and epoxy compounds, respectively. Through the following two H-transfer steps, carbene intermediate forms the products of allenes and alkynes, respectively. From the thermodynamics viewpoint, the allenes are the dominant product for the title reaction.
Journal Article
الميكانيكا الهندسية = Engineering mechanics
هذا الكتاب يتحدث عن الميكانيكا الهندسية وهو يقدم عرض بسيط ومتدرج ومنطقي لموضعات الاستاتيكا مدعم بالأمثلة المحلولة والمسائل والأشكال التوضيحية للآفكار الصعبة وشرح واضح للأفكار الفيزيائية والعلاقات الرياضية ويتناول الكتاب علم الاستاتيكا ثم استاتيكا الجسيمات للقوى المتلاقية في مستوى والقوى الفراغية ثم استاتيكا الأجسام الجاسئة للقوى غير المتلاقية المستوية والفراغية.
BOOK
An Energy-Efficient MAC Protocol Employing Dynamic Threshold for Wireless Sensor Networks
Energy efficiency is a critical issue for sensor network since the network lifetime depends on efficient management of the energy resource of sensor nodes. Particularly, designing energy efficient MAC protocol has a significant influence on the performance of wireless sensor network with regards to the energy. The existing MAC protocols developed for sensor network try to avoid energy waste during idle listening time by controlling the duty cycle of the transmission period. Since the traffic conditions are diverse, they may not always display improvements in energy consumption. In this paper we propose a new energy efficient MAC protocol called dynamic threshold MAC (DT-MAC), which employs a dynamic threshold for the buffer of each sensor node to maximize the energy efficiency regardless of specific network traffic condition. Here the packets are stored in the buffer, and then transmitted when the number of packets in the buffer exceeds the threshold dynamically decided according to the number of hops of the node from the source in the path of packet forwarding. The simulation results using OMNnet++ show that DT-MAC enables significant improvement in energy consumption compared to the existing MAC protocols. The proposed DT-MAC protocol also reduces the number of transmissions of control packets.
Journal Article