Fateme Salehi  Mohammad‐Hassan Majidi  Naaser Neda 《International Journal of Communication Systems》2018,31(12)

The abundant benefits of Orthogonal Frequency‐Division Multiplexing and its high flexibility have resulted in its widespread applications in many telecommunication standards. One important parameter for improving wireless system's efficiency is the accurate estimation of channel state information. In the literatures, many techniques have been studied in order to estimate the channel state information. Nowadays, the techniques based on intelligent algorithms such as genetic algorithm and particle swarm optimization (PSO) have attracted attention of researchers. With a very low pilot overhead, these techniques are able to estimate the channel frequency response properly only using the received signals. Unfortunately, each of these techniques suffers a common weakness: they have a slow convergence rate. In this paper, a new intelligent and different method has been presented for channel estimation using learning automata, entitled LA estimator, where the learning automata are search agents, and each pair is responsible for searching 1 complex coefficient of the channel frequency response. This method can achieve an accurate channel estimation with a moderate computational complexity in comparison with GA and PSO estimators. Furthermore, with higher convergence rate, our proposed method is capable of providing the same performance as GA and PSO. For a 2‐path fast fading channel, simulation results demonstrate the robustness of our proposed scheme according to the bit error rate and the mean square error.  相似文献   

    

Fakhreddin Salehi 《Journal of Food Processing and Preservation》2020,44(11):e14879

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Leila Monjazeb Marvdashti  Seyed Abdulmajid Ayatollahi  Bahare Salehi  Javad Sharifi-Rad  Anna Abdolshahi  Razieh Sharifi-Rad  Filippo Maggi 《Journal of Food Safety》2020,40(4):e12805

Edible coating based on Alyssum homalocarpum seed gum (AHSG) and chitosan for coating of fresh apricot was optimized using response surface methodology (RSM). The independent variables included concentrations of AHSG and chitosan in coating solution. The response variables studied were total soluble solid, weight loss, titratably acidity, pH, reducing sugar, moisture content, and firmness. Results indicated that RSM models were significantly (p < .05) qualified for all response variables, except for total soluble solid and titratable acidity. The regression models demonstrated R² ranging from .78 to .99. AHSG concentration influenced the weight loss, pH, and firmness, while chitosan concentration had an effect on pH and moisture content. This study showed that the coating can improve apricot firmness and stability in terms of weight loss, pH, and moisture content. The study suggested that a combination of AHSG 1.02% (w/w) and chitosan 0.33% (w/w) is the best one to achieve the desirable responses.  相似文献   

    

Saeid Shadmani  Zeinab Salehi  Hamid Doosthosseini  Shams Mohajerzadeh  Sahar Roozbahani 《加拿大化工杂志》2018,96(2):531-536

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Abolfazl Salehi  Seyed Hassan Jafari  Hossein Ali Khonakdar  Hassan Ebadi‐Dehaghani 《应用聚合物科学杂志》2018,135(35)

Polypropylene (PP)/poly(lactic acid) (PLA)/clay nanocomposite films with various compositions (PP‐rich and PLA‐rich) were prepared. Their structural and barrier properties against CO₂, O₂, and N₂ were investigated. The microstructure of the nanocomposites was studied by scanning electron microscopy, transmission electron microscopy, and wide angle X‐ray scattering. The PP‐rich with 75/25 composition revealed the best barrier properties against all the gases which could be justified according to its microstructure. Selectivity of O₂/N₂ and CO₂/N₂ was also measured. It was found that the addition of nanoclay as a gas barrier component reduced the permeability in both systems. The permselectivity was also reduced in the PP‐rich films while it was increased in the PLA‐rich system. Moreover, the temperature dependency of permeability, selectivity, and permselectivity for PP, PLA, and PP/PLA (75/25) samples was examined. The results showed that the temperature dependence of permeability obeyed an Arrhenius equation and order of activation energy of permeability for O₂, CO₂, and N₂ gases was found to be E_P < E_P/PLA < E_PLA. According to solubility measurements, the order of solubility coefficient for gases was as follows: CO₂ > O₂ > N₂. Finally, the molecular dynamics (MD) simulation was performed to estimate the diffusivity coefficients of the gases and showed that solubility increases with increasing temperature, which was in accordance with the experiments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46665.  相似文献   

    

Zahra Hemmat  Poya Yasaei  Jeremy F. Schultz  Liang Hong  Leily Majidi  Amirhossein Behranginia  Louisiane Verger  Nan Jiang  Michel W. Barsoum  Robert F. Klie  Amin Salehi‐Khojin 《Advanced functional materials》2019,29(19)

Heat transport across vertical interfaces of heterogeneous 2D materials is usually governed by the weak Van der Waals interactions of the surface‐terminating atoms. Such interactions play a significant role in thermal transport across transition metal carbide and nitride (MXene) atomic layers due to their hydrophilic nature and variations in surface terminations. Here, the metallicity of atomically thin Ti₃C₂T_z MXene, which is also verified by scanning tunneling spectroscopy for the first time, is exploited to develop a self‐heating/self‐sensing platform to carry out direct‐current annealing experiments in high (<10^?8 bar) vacuum, while simultaneously evaluating the interfacial heat transport across a Ti₃C₂T_z/SiO₂ interface. At room temperature, the thermal boundary conductance (TBC) of this interface is found, on average, to increase from 10 to 27 MW m^?2 K^?1 upon current annealing up to the breakdown limit. In situ heating X‐ray diffraction and X‐ray photo‐electron spectroscopy reveal that the TBC values are mainly affected by interlayer and interface spacing due to the removal of absorbents, while the effect of surface termination is negligible. This study provides key insights into understanding energy transport in MXene nanostructures and other 2D material systems.  相似文献   

    

Soroosh Sharifi‐Asl  Fernando A. Soto  Tara Foroozan  Mohammad Asadi  Yifei Yuan  Ramasubramonian Deivanayagam  Ramin Rojaee  Boao Song  Xuanxuan Bi  Khalil Amine  Jun Lu  Amin Salehi‐khojin  Perla B. Balbuena  Reza Shahbazian‐Yassar 《Advanced functional materials》2019,29(23)

LiCoO₂ is a prime example of widely used cathodes that suffer from the structural/thermal instability issues that lead to the release of their lattice oxygen under nonequilibrium conditions and safety concerns in Li‐ion batteries. Here, it is shown that an atomically thin layer of reduced graphene oxide can suppress oxygen release from Li_xCoO₂ particles and improve their structural stability. Electrochemical cycling, differential electrochemical mass spectroscopy, differential scanning calorimetry, and in situ heating transmission electron microscopy are performed to characterize the effectiveness of the graphene‐coating on the abusive tolerance of Li_xCoO₂. Electrochemical cycling mass spectroscopy results suggest that oxygen release is hindered at high cutoff voltage cycling when the cathode is coated with reduced graphene oxide. Thermal analysis, in situ heating transmission electron microscopy, and electron energy loss spectroscopy results show that the reduction of Co species from the graphene‐coated samples is delayed when compared with bare cathodes. Finally, density functional theory and ab initio molecular dynamics calculations show that the rGO layers could suppress O₂ formation more effectively due to the strong C? O_cathode bond formation at the interface of rGO/LCO where low coordination oxygens exist. This investigation uncovers a reliable approach for hindering the oxygen release reaction and improving the thermal stability of battery cathodes.  相似文献   

    

Hoang Pham  Jason Woodworth  Mohsen Amini Salehi 《Concurrency and Computation》2019,31(17)

Cloud computing has become a potential resource for businesses and individuals to outsource their data to remote but highly accessible servers. However, the potential of cloud services has not been fully realized due to users concerns about data privacy and security. User‐side encryption techniques can be employed to mitigate the security concerns, but once the data is encrypted, no processing (eg, searching) can be performed on the outsourced data. Searchable Encryption (SE) techniques have been widely studied to enable searching on the data while they are encrypted. These techniques enable various types of search on the encrypted data and offer different levels of security. While these techniques enable different search types and vary in details, they share similarities in their components and architectures. In this paper, we provide a comprehensive survey on different secure search techniques, a high‐level architecture for these systems, and an analysis of their performance and security level.  相似文献   

    

Prof. Dr.‐Ing. Wolfram Jäger  Hamidreza Salehi 《Mauerwerk》2019,23(4):227-231

Partial safety factors for resistance applied in the design equation of semi‐probabilistic formats can be obtained from the evaluation of a test database. These partial safety factors are influenced by two factors, the material uncertainty and the model uncertainty. This topic is covered in a former publication [1]. It includes the determination of a partial factor for the model uncertainty of unreinforced masonry shear walls. In this study the authors examine the next step, and calculate the partial factor of resistance applying the same method, as recommended i n EN 1990 – Annex D. In addition to the Coefficient of Variation (COV) for the model uncertainty, the calculation of the resistance partial factor considers deviations in geometry, as well as loading and material properties. The influence of the material uncertainty on structural performance is considered in the calculation by means of a weighted average of all COV values for various types of material properties, based on the number of relevant failure modes in the test database. In the last step, the resistance partial factors for models defined in DIN EN 1996‐1‐1/NA and DIN EN 1996‐1‐1/NA – Annex K are calculated by applying the probabilistic methods recommended in EN 1990 – Annex D and the model bias.  相似文献   

    

Alireza Ahmadiparidari  Robert E. Warburton  Leily Majidi  Mohammad Asadi  Amir Chamaani  Jacob R. Jokisaari  Sina Rastegar  Zahra Hemmat  Baharak Sayahpour  Rajeev S. Assary  Badri Narayanan  Pedram Abbasi  Paul C. Redfern  Anh Ngo  Mrton Vrs  Jeffrey Greeley  Robert Klie  Larry A. Curtiss  Amin Salehi‐Khojin 《Advanced materials (Deerfield Beach, Fla.)》2019,31(40)

Lithium–CO₂ batteries are attractive energy‐storage systems for fulfilling the demand of future large‐scale applications such as electric vehicles due to their high specific energy density. However, a major challenge with Li–CO₂ batteries is to attain reversible formation and decomposition of the Li₂CO₃ and carbon discharge products. A fully reversible Li–CO₂ battery is developed with overall carbon neutrality using MoS₂ nanoflakes as a cathode catalyst combined with an ionic liquid/dimethyl sulfoxide electrolyte. This combination of materials produces a multicomponent composite (Li₂CO₃/C) product. The battery shows a superior long cycle life of 500 for a fixed 500 mAh g^?1 capacity per cycle, far exceeding the best cycling stability reported in Li–CO₂ batteries. The long cycle life demonstrates that chemical transformations, making and breaking covalent C? O bonds can be used in energy‐storage systems. Theoretical calculations are used to deduce a mechanism for the reversible discharge/charge processes and explain how the carbon interface with Li₂CO₃ provides the electronic conduction needed for the oxidation of Li₂CO₃ and carbon to generate the CO₂ on charge. This achievement paves the way for the use of CO₂ in advanced energy‐storage systems.  相似文献