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31.
Hamed Alasarpanahi Vahid Ayatollahitafti Abolfazl Gandomi 《International Journal of Communication Systems》2020,33(6)
Underwater wireless sensor networks (UWSNs) consist of a group of sensors that send the information to the sonobuoys at the surface level. Void area, however, is one of the challenges faced by UWSNs. When a sensor falls in a void area of communication, it causes problems such as high latency, power consumption, or packet loss. In this paper, an energy‐efficient void avoidance geographic routing protocol (EVAGR) has been proposed to handle the void area with low amount of energy consumption. In this protocol, a suitable set of forwarding nodes is selected using a weight function, and the data packets are forwarded to the nodes inside the set. The weight function includes the consumed energy and the depth of the candidate neighboring nodes, and candidate neighboring node selection is based on the packet advancement of the neighboring nodes toward the sonobuoys. Extensive simulation experiments were performed to evaluate the efficiency of the proposed protocol. Simulation results revealed that the proposed protocol can effectively achieve better performance in terms of energy consumption, packet drop, and routing overhead compared with the similar routing protocol. 相似文献
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Harifi-Mood Mehrdad Bijari Abolfazl Alizadeh Hossein Forouzanfar Mehdi Kandalaft Nabeeh 《Analog Integrated Circuits and Signal Processing》2021,107(3):551-565
Analog Integrated Circuits and Signal Processing - The power amplifiers (PAs) are generally the most power-consuming building blocks in Radio Frequency (RF) transceivers. This paper presents a high... 相似文献
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Boghaei DM Askarizadeh E Bezaatpour A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(2):624-628
The water-soluble cobalt(II) tetradentate Schiff base complex [Co(II)L](ClO4)(2), L: (N,N'-bis(5-[(triphenylphosphonium)-methyl]salicylidine)-o-phenylenediamineperchlorate has been synthesized and characterized. This complex forms charge transfer (CT) complexes with imidazole and 1-methylimidazole. The formation constant, molar absorptivity (epsilon'), and thermodynamic parameters for charge transfer complexes formation of cobalt(II) Schiff base complexes with imidazole derivatives were determined by using UV-vis spectrophotometric method in aqueous solutions at constant ionic strength (I=0.2mol dm(-3) KNO3) at pH 6.0 and various temperatures between 292 and 315K. 相似文献
34.
Kiani A Alpuche-Aviles MA Eggers PK Jones M Gooding JJ Paddon-Row MN Bard AJ 《Langmuir : the ACS journal of surfaces and colloids》2008,24(6):2841-2849
Electron transfer (ET) rate kinetics through n-alkanethiol self-assembled monolayers (SAMs) of alkanethiols of different chain lengths [Me(CH2)nSH; n=8, 10, 11, 15] on Au and Hg surfaces and ferrocene (Fc)-terminated SAMs (poly-norbornylogous and HS(CH2)12CONHCH2Fc) on Au were studied using cyclic voltammetry and scanning electrochemical microscopy (SECM). The SECM results allow determination of the ET kinetics of solution-phase Ru(NH3)63+/2+ through the alkanethiol SAMs on Au and Hg. A model using the potential dependence of the measured rate constants is proposed to compensate for the pinhole contribution. Extrapolated values of koML for Ru(NH3)63+/2+ using the model follow the expected exponential decay (beta is 0.9) for different chain lengths. For a Fc-terminated poly-norbornyl SAM, the standard rate constant of direct tunneling (ko is 189+/-31 s(-1)) is in the same order as the ko value of HS(CH2)12CONHCH2Fc. In blocking and Fc SAMs, the rates of ET are demonstrated to follow Butler-Volmer kinetics with transfer coefficients alpha of 0.5. Lower values of alpha are treated as a result of the pinhole contribution. The normalized rates of ET are 3 orders of magnitude higher for Fc-terminated than for blocking monolayers. Scanning electron microscopy imaging of Pd nanoparticles electrochemically deposited in pinholes of blocking SAMs was used to confirm the presence of pinholes. 相似文献
35.
A one-pot, three-component reaction of 2,3-dihydroxynaphthalene, aromatic aldehydes, and cyclic 1,3-dicarbonyl compounds in the presence of formic acid catalyst under solvent-free conditions provides access toward a new class of tetrahydrobenzo[a]xanthen-11-ones and naphthopyranopyrimidines. The scope of the process was explored under two different reaction conditions resulting in the generation of title compounds in high yields. Moreover, the key advantages of this process are cost effectiveness of catalyst, short reaction times, easy workup, and purification of products by nonchromatographic methods. 相似文献
36.
Guanidine Hydrochloride: A Highly Efficient Organocatalyst for the Synthesis of 12‐Aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthene‐11‐ones Under Solvent‐Free Conditions
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Mahdieh Sadeghpour Abolfazl Olyaei Mortaza Rezaei 《Journal of heterocyclic chemistry》2016,53(3):981-988
A new green protocol has been developed for the synthesis of 12‐aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthen‐11‐ones using guanidine hydrochloride as an organocatalyst under solvent‐free conditions. Operational simplicity, mild reaction conditions, enhanced rates, high isolated yields of the pure products, and purification of products by nonchromatographic methods are significant advantages of the protocol presented here. 相似文献
37.
Nested and interleaved direct sequence spread spectrum to enhance CDMA security and bit error rate performance
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Abolfazl Falahati Nader Sanandaji 《International Journal of Communication Systems》2016,29(12):1907-1915
Two new methods, the nested direct sequence spread spectrum and interleaved direct sequence spread spectrum, are introduced in view of the previously investigated spread spectrum methods. In the nested direct sequence method, the security is maintained, and the cross‐correlation between different codes resulting in multi‐user interference that corresponds to BER performance is improved, while in the interleaved direct sequence spread spectrum, the security is improved and BER performance is maintained. Both methods are analysed by mathematical relations as well as computer simulations and are compared with the existing methods. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Orthogonal array design (OAD) was applied for the first time to optimize cloud point extraction (CPE) conditions for Se(IV) determination by electrothermal atomic absorption spectrometry (ETAAS) in environmental and biological samples. Selenium was reacted with o-phenylenediamine to form piazselenol in an acidic medium (pH 2). Using Triton X-114, as surfactant, piazselenol was quantitatively extracted into small volume (about 30 μL) of the surfactant-rich phase after centrifugation. Five relevant factors, i.e. surfactant concentration, pH, ionic strength, equilibrium time and temperature were selected and the effects of each factor were studied at four levels on the extraction efficiency of Se(IV) and optimized. The statistical analysis revealed that the most important factors contributing to the extraction efficiency are ionic strength, pH and percent of surfactant. Based on the results obtained from the analysis of variance (ANOVA), the optimum conditions for extraction were established as: pH 6; vial temperature = 50 °C; extraction time = 7 min and 0.3% (w/v) of Triton X-114. The method was permitted to obtain a detection limit of 0.09 ng mL−1 and two linear calibration ranges from 0.6 to 1.0 and 1.0 to 80.0 ng mL−1 Se. The precision (%RSD) of the extraction and determination for the six replicates of Se at 20 ng mL−1 was better than 3.6% and the enrichment factor of 63.5 was achieved. The studied analyte was successfully extracted and determined with high efficiency using cloud point extraction method in water and biological matrices. 相似文献
40.
Even though various wireless Net-work Access Technologies (NATs) with dif-ferent specifications and applications have been developed in the recent years, no single wireless technology alone can satisfy the any-time, anywhere, and any service wire-less-access needs of mobile users. A real seamless wireless mobile environment is only realized by considering vertical and horizontal handoffs together. One of the major design issues in heterogeneous wireless networks is the support of Vertical Handoff (VHO). VHO occurs when a multi-interface enabled mobile terminal changes its Point of Attachment (PoA) from one type of wireless access technology to another, while maintaining an active session. In this paper we present a novel multi-criteria VHO algorithm, which chooses the target NAT based on several factors such as user preferences, system parameters, and traffic-types with varying Quality of Service (QoS) requirements. Two modules i.e., VHO Necessity Estimation (VHONE) module and target NAT selection module, are designed. Both modules utilize several “weighted” users’ and system’s parameters. To improve the robustness of the proposed algorithm, the weighting system is designed based on the concept of fuzzy linguistic variables. 相似文献