Sharif Digital Repository

Quasi-3D plasmonic nanostructures consisting of a metallic film perforated as an array of nanoholes, separated by a gap from a nanodisk array, are theoretically investigated under plane wave illumination with transverse electric and transverse magnetic polarizations. The results are compared with the results of a simple nanodisk array. A full discussion involving the couplings between plasmon resonance in nanodisks, surface plasmon polaritons on the interfaces of metallic film, and different diffractive grating orders that contribute in the couplings will be presented. The large difference between the plasmon behavior of the nanodisk array alone and nanodisk array in the presence of nanohole... 

Optical transmission through double-layer metallic subwavelength holes array is studied under oblique incidence by split-field finite-difference time-domain method. Both TM and TE polarizations are investigated. It is proved that the transmission peaks can also be observed for TE polarization due to the excitation of surface plasmon polaritons (SPP) through diffraction orders. By changing the incident angle, these transmission peaks follow the SPP wavelength shift. The field profiles, even for the field components not present in the incident field, clearly show the SPP excitation. The mechanism of enhanced transmission will be fully discussed  

Split-field finite-difference time-domain (SF-FDTD) method can overcome the limitation of ordinary FDTD in analyzing periodic structures under oblique incidence. On the other hand, huge run times of 3D SF-FDTD, is practically a major burden in its usage for analysis and design of nanostructures, particularly when having dispersive media. Here, details of parallel implementation of 3D SF-FDTD method for dispersive media, combined with totalfield/ scattered-field (TF/SF) method for injecting oblique plane wave, are discussed. Graphics processing unit (GPU) has been used for this purpose, and very large speed up factors have been achieved. Also a previously reported formulation of SF-FDTD based... 

The three-dimensional split-field finite-difference time-domain (SF-FDTD) method is combined with the totalfield- scattered-field method for injecting a plane wave. A formulation is derived for calculating the incidence transformed fields of SF-FDTD on a one-dimensional auxiliary grid. The resulting fields obtained in the scattered zone are used to calculate the far fields, based on a proposed fully time-domain near-to-far-field transformation. The far-field information is used to calculate the extinction cross section of the periodic structure under oblique incidence. To analyze metallic periodic structures, a formulation with a reduced number of variables is proposed based on the auxiliary... 

We have previously reported the results of plasmonic behavior of an Au nanodisk array in the far-field coupling regime under oblique illumination with transverse electric polarization. In this paper, those results are studied in more detail. Here, results for transverse magnetic polarization are also presented and discussed. In addition to the far-field coupling regime, the results for the near-field coupling regime are also reported. Effects of different parameters, such as substrate thickness and array periodicity on the shape of plasmon spectra are discussed. It will be shown that in the far-field coupling regime, the diffractive grating orders can have a major role in the behavior of the... 

In this paper, a new transport layer method is proposed utilizing a diversity scheme to make an end to end communication reliable and consequently reduce power consumption in large scale sensor networks. Sensor networks are composed of large number of battery powered nodes. Energy consumption is the most important design objective in sensor networks while delay and throughput are taken less into account. Wireless transmission is the other important characteristic of these networks. Small-scale fading decreases wireless communication performance. In a fading channel higher SNRs is needed and consequently more energy is consumed. In addition to error occurred because of poor communication... 

Tunability of the Fermi level of graphene is exploited to implement a plasmonic nano-color-sorter for scanning near-field optical microscope (SNOM) applications capable of handling large tip sample couplings. Nano-color-sorting has been used in SNOM through creating multiple spatially separated hot spots for different incident wavelengths. We show that in the presence of high-refractive-index samples an unwanted redshift in the spectral response of the dual-color probe occurs. This limitation can be compensated for using graphene and adjusting its chemical potential to obtain a blueshift in probe spectral response. The Method of Moments analysis technique is employed to engineer the probe... 

This paper proposes a new medium-access control (MAC) protocol designed for wireless sensor networks. A wireless sensor network is an array of large number of sensors interconnected by a multi-hop ad-hoc network. The fundamental objective for sensor network is low-power consumption while latency is usually less important. This characteristic of sensor network motivates different MAC laver design from the conventional wireless network to reduce power consumption. In this paper novel algorithm based on distributed mediation device (DMD) protocol has been introduced that utilized distributed node scheduling strategy to dramatically increase energy saving principally in intermediate devices... 

Subradiant modes can exhibit sharper spectral response, and lower radiative loss compared to the super-radiant modes of plasmonic nanostructures. Selective excitation of these modes is challenging, and has practical importance. In this paper, a systematic procedure for determining, and individually exciting the subradiant modes of a plasmonic nanostructure is presented by utilizing our previously reported T-matrix formulation. As an example, we calculate various modes of a gold nanodimer, and determine the incident field required for exciting a subradiant mode of this nanostructure. This field is then generated by a modified zone plate lens. The expansion of scattered field, as well as the... 

In the present work we obtained a series of NIR luminescent platinum(II) complexes with a pincer N^N^C ligand based on the conjugated {benzoimidazo[1,2-a]pyrazine} system with the [Pt(N^N^C)L]n+ structural motif (L = phosphine, alkynyl or pyridine-type ligands). We have also synthesized two complexes with bidentate phosphines that demonstrate different types of coordination: 1) as chelating ligand (in case of 1,2-bis(diphenylphosphino)benzene), that led to de-coordination of pyridine ring of N^N^C ligand and formation of a [Pt(N^C)dppb]+ complex; 2) as a bridging ligand (in case of bis(diphenylphosphino)methane) between two {Pt(N^N^C)} fragments in a dimeric complex of type... 

The combined action of ultraviolet irradiation and microwave heating onto acetonitrile solution of [Re((Formula presented.))(CO)3(NCMe)]OTf ((Formula presented.) =phenantroline and neocuproine) afforded cis,trans-Re((Formula presented.))(CO)2(NCMe)2]+ acetonitrile derivatives. Substitution of relatively labile NCMe with a series of aromatic N-donor ligands (pyridine, pyrazine, 4,4’-bipyridine, N-methyl-4,4’-bipyridine) gave a novel family of the diimine cis,trans-[Re((Formula presented.))(CO)2(L)2]+ complexes. Photophysical studies of the obtained compounds in solution revealed unusually high absorption across the visible region and NIR phosphorescence with emission band maxima ranging from... 

A Deza graph with parameters (n, k, b, a) is a k-regular graph with n vertices such that any two of its vertices have b or a common neighbours, where b ≥ a. In this paper we investigate spectra of Deza graphs. In particular, using the eigenvalues of a Deza graph we determine the eigenvalues of its children. Divisible design graphs are significant cases of Deza graphs. Sufficient conditions for Deza graphs to be divisible design graphs are given, a few families of divisible design graphs are presented and their properties are studied. Our special attention goes to the invertibility of the adjacency matrices of Deza graphs. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group  

A Deza graph with parameters (Formula presented.) is a k-regular graph with n vertices such that any two of its vertices have b or a common neighbours, where (Formula presented.). In this paper we investigate spectra of Deza graphs. In particular, using the eigenvalues of a Deza graph we determine the eigenvalues of its children. Divisible design graphs are significant cases of Deza graphs. Sufficient conditions for Deza graphs to be divisible design graphs are given, a few families of divisible design graphs are presented and their properties are studied. Our special attention goes to the invertibility of the adjacency matrices of Deza graphs. © 2020 Informa UK Limited, trading as Taylor &... 

The influence of the addition of the nonionic surfactants C12DMPO, C14DMPO, C10OH, and C10EO5 at concentrations between 10-5 and 10-1 mmol/L to solutions of β-casein (BCS) and β-lactoglobulin (BLG) at a fixed concentration of 10-5 mmol/L on the dilational surface rheology is studied. A maximum in the viscoelasticity modulus |E| occurs at very low surfactant concentrations (10-4 to 10-3 mmol/L) for mixtures of BCS with C12DMPO and C14DMPO and for mixtures of BLG with C10EO5, while for mixture of BCS with C10EO5 the value of |E| only slightly increased. The |E| values... 

The aim of this work was to study the treatment of strong beet sugar wastewater by an upflow anaerobic fixed bed (UAFB) at pilot plant scale. Three fixed bed bioreactors (each 60 L) were filled with standard industrial packing, inoculated with anaerobic culture (chicken manure, cow manure, anaerobic sludge digested from domestic wastewater) and operated at 32-34 °C with 20 h hydraulic retention time (HRT) and influent COD ranging between 2000-8000 mg/L. Under these conditions the maximum efficiency of organic content reduction in the reactor ranged from 75% to 93%. The reactor filled with standard pall rings made of polypropylene with an effective surface area of 206 m2/m3 performed best in... 

Let two coordinate systems, in possession of Alice and Bob, be related to each other by an unknown rotation R∈ SO (3). Alice is to send identical states | ψ⟩ to Bob who will make measurements on the received state and will determine the rotation R. The task of Bob is to estimate these parameters of the rotation R by the best possible measurements. Based on the quantum Fisher information, we show that Greenberger–Horne–Zeilinger (GHZ) states are near optimal states for this task. We show concrete measurements which will allow Bob to determine the rotation R. This shows that GHZ states, as superposition of macroscopically distinct states, are useful in yet another context in quantum... 

A Deza graph G with parameters (n,k,b,a) is a k-regular graph with n vertices such that any two distinct vertices have b or a common neighbours. The children GA and GB of a Deza graph G are defined on the vertex set of G such that every two distinct vertices are adjacent in GA or GB if and only if they have a or b common neighbours, respectively. A strongly Deza graph is a Deza graph with strongly regular children. In this paper we give a spectral characterisation of strongly Deza graphs, show relationships between eigenvalues, and study strongly Deza graphs which are distance-regular. © 2021 Elsevier B.V