Performance analysis of PDMA-based hybrid satellite–terrestrial networks with decode-and-forward relaying

As one of the most promising non-orthogonal multiple access (NOMA) technologies in 5G communication, pattern division multiple access (PDMA) has theoretically higher spectrum utilization and a larger communication capacity than conventional orthogonal multiple access (OMA) technologies. In this letter, PDMA is applied to hybrid satellite–terrestrial networks with decode-and-forward (DF) relaying in the downlink, and an in-depth study on the performance of outage probability (OP), ergodic capacity and system throughput is performed. For a more comprehensive analysis, hybrid satellite–terrestrial relay networks (HSTRNs) with conventional OMA technology are used in the comparative analysis. Analysis and simulation results show that PDMA-based hybrid satellite–terrestrial relay networks outperform the other system in terms of OP and ergodic capacity.     

High speed integrated RF–VLC data communication system: Performance constraints and capacity considerations

In this research paper, we propose a two-hop integrated radio frequency–visible light communication (RF–VLC) system which may provide a better option to transceive between the hospitals and some laboratory to transfer patient’s information. In the proposed system model, the data (such as patient’s lab test reports) is transmitted towards the amplify and forward (AF) relay mounted on the top of the hospital building via the RF channel. Further, the AF relay amplifies and converts the received information into corresponding optical signal using light emitting diodes (LED) and supporting circuitry. This optical signal is then forwarded towards the destination device (equipped with VLC transceiver), via the VLC channel. To analyse the performance of the system, we first derive the closed form analytical expressions for the cumulative distribution function (CDF) of the end-to-end (e2e) signal to noise ratio (SNR) of the system by using the moment generating function (MGF) of the SNR of the individual RF and VLC channels. Further, we use these statistical expressions to obtain the outage probability, average bit error rate (BER) and the average capacity of the system. Moreover, the asymptotic performance of the proposed system is also analysed to study the system’s behaviour at high SNR regimes. Finally, we studied the impact of the variations in channel parameters on the proposed system model performance through numerically simulated plots.     

Dynamic contact analysis of a tensioned beam with a moving mass–spring system

The dynamic contact problem of a tensioned beam with clamped-pinned ends is analyzed when the beam contacts a moving mass–spring system. The contact and contact loss conditions are expressed in terms of constraint equations after considering the dynamic contact between the beam and the moving mass. Using these constraints and equations of motion for the beam and moving mass, dynamic contact equations are derived and then discretized using the finite element method, which is based on the Lagrange multiplier method. The time responses for the contact forces are computed from these discretized equations. The contact force variations and contact loss are investigated for the variations of the moving mass velocity, the beam tension, the moving mass, and the stiffness of the moving mass–spring system. In addition, the possibility of contact loss and safe contact conditions between the moving mass and the tensioned beam are also studied.     

Stability analysis of a rotor–bearing system with time-varying bearing stiffness due to finite number of balls and unbalanced force

Previous investigations have indicated that the finite number of balls can cause the bearing stiffness to vary periodically. However, effects of unbalanced force in a rotor–bearing system on the bearing stiffness have not received sufficient attention. The present work reveals that the unbalanced force can also make the bearing stiffness vary periodically. The parametric excitations from the time-varying bearing stiffness can cause instability and severe vibration under certain operating conditions. Therefore, the determination of the operating conditions of parametric instability is crucial to the design of high speed rotating machinery. In this paper, an extended Jones–Harris stiffness model is presented to ascertain the stiffness of the angular contact ball bearing considering five degrees of freedom. Stability analysis of a rigid rotor–bearing system is performed utilizing the discrete state transition matrix (DSTM) method. The effects of unbalanced force, bearing loads and damping on the instability regions are discussed thoroughly. Investigations mainly show that the time-varying bearing stiffness fluctuates sinusoidally due to finite number of balls and unbalanced force. The locations and widths of the instability regions caused by these two parametric excitations differ distinctly. Unbalanced force could change the widths of the instability regions, but without altering their central positions. The axial and radial loads of the bearing only change the positions of the instability regions, without affecting their widths. Besides, damping can reduce the widths of the instability regions.     

Relaxation process and ferromagnetic resonance investigation of ferrofluids with Mn–Zn and Mn–Fe mixed ferrite particles

The magnetic relaxation processes in two ferrofluids with Mn_0.4Zn_0.6Fe₂O₄ (sample F1) and Mn_0.6Fe_0.4Fe₂O₄ (sample F2) mixed ferrite particles, dispersed in n-decan and kerosene, respectively, are investigated through the determination of components χ′ and χ′′ of the complex magnetic susceptibility in the range of (2–30) MHz. The values of the saturation magnetization of the two ferrofluids are M_∞=5.28 kA/m for sample F1 and M_∞=10.99 kA/m for sample F2. A maximum of the imaginary component χ′′ was observed for both samples at frequencies of tens MHz. This maximum was assigned to relaxation processes of Néel type.The effective anisotropy constant K of the particles from the studied samples was evaluated, using both static and dynamic measurements and the values were found to be K₁=6.12×10³ J m⁻³ for the ferrofluid F1, and K₂=5.60×10³ J m⁻³ for the ferrofluid F2. From ferromagnetic resonance measurements, and based on the theoretical values computed for the Lande factor (g), the effective anisotropy constants for the mixed ferrite particles in the studied ferrofluids and the anisotropy field values were determined using a new method. The values obtained in this way for the anisotropy constants K₁ and K₂ are compared to the ones determined from magnetic relaxation measurements.     

Pedestrian lane formation with following–overtaking model and measurement of system order

Pedestrian self-organizing movement plays a significant role in evacuation studies and architectural design. Lane formation, a typical self-organizing phenomenon, helps pedestrian system to become more orderly, the majority of following behavior model and overtaking behavior model are imprecise and unrealistic compared with pedestrian movement in the real world. In this study, a pedestrian dynamic model considering detailed modelling of the following behavior and overtaking behavior is construct...     

Optimized electron–optical system of a static mass-spectrometer for simultaneous isotopic and chemical analysis

A new approach to control the linear dimensions of analytical electrophysical systems is suggested. This approach uses the lens properties of electron–optical elements with a curvilinear axis. It is shown that such an approach can be effectively applied, in particular, to synthesize ion–optical systems (IOSs) for static magnetic mass spectrometers and can be implemented owing to off-axis fundamental points, the “poles” of an electron–optical system, introduced earlier by one of the authors. The capabilities of the new approach are demonstrated with the synthesis of the IOS of a static mass spectrometer dedicated for isotopic and chemical analysis with an increased resolution. A new IOS not only provides desired high ion–optical parameters at decreased dimensions of the mass spectrometer as a whole but also makes it possible to loosen requirements for the manufacturing accuracy of IOS main elements.     

Preparation and probe analysis of Langmuir–Blodgett films with metal-containing dendritic and cluster structures

We aim to reveal the influence of?pH values of the working solution on spatial arrangement of metal-containing inclusions in the monolayer coatings prepared by Langmuir?CBlodgett (LB) technology and transferred to solid substrates with consequent modification of surface electrical properties. Consequently, films with inclusions in the form of dendrites and cluster shapes have been obtained. Submicron and micron lead-containing formations in Langmuir?CBlodgett films have been characterized by using the atomic force microscopy, Kelvin probe microscopy, and scanning electron microscopy methods. The results show that increasing?pH value of the subphase has caused the significant changes in the shape and composition of the inclusions in Langmuir?CBlodgett films. The synthesized inclusions on the solid substrate surface resulted in formation of the regions with the local electric fields and, as consequence, to significant modification of the structure and electrical properties. The location and length of the regions with surface potential disturbance depend on the shape of inclusions, and consequently, on?pH value of the subphase used in LB technology.     

Dynamical analysis of bounded and unbounded orbits in a generalized Hénon–Heiles system

The Hénon–Heiles potential was first proposed as a simplified version of the gravitational potential experimented by a star in the presence of a galactic center. Currently, this system is considered a paradigm in dynamical systems because despite its simplicity exhibits a very complex dynamical behavior. In the present paper, we perform a series expansion up to the fifth-order of a potential with axial and reflection symmetries, which after some transformations, leads to a generalized Hénon–Heiles potential. Such new system is analyzed qualitatively in both regimes of bounded and unbounded motion via the Poincaré sections method and plotting the exit basins. On the other hand, the quantitative analysis is performed through the Lyapunov exponents and the basin entropy, respectively. We find that in both regimes the chaoticity of the system decreases as long as the test particle energy gets far from the critical energy. Additionally, we may conclude that despite the inclusion of higher order terms in the series expansion, the new system shows wider zones of regularity (islands) than the ones present in the Hénon–Heiles system.     

Hybrid uncertainty propagation of coupled structural–acoustic system with large fuzzy and interval parameters

Based on the finite element framework and uncertainty analysis theory, this paper proposes a first-order subinterval perturbation finite element method (FSPFEM) and a modified subinterval perturbation finite element method (MSPFEM) to solve the uncertain structural–acoustic problem with large fuzzy and interval parameters. Fuzzy variables are used to represent the subjective uncertainties associated with the expert opinions; whereas, interval variables are adopted to quantify the objective uncertainties with limited information. By using the level-cut strategy and subinterval methodology, the original large fuzzy and interval parameters are decomposed into several subintervals with small uncertainty level. In both FSPFEM and MSPFEM, the subinterval matrix and vector are expanded by the Taylor series. The inversion of subinterval matrix in FSPFEM is approximated by the first-order Neumann series, while the modified Neumann series with higher order terms is adopted in MSPFEM. The eventual fuzzy interval frequency responses are reconstructed by the interval union operation and fuzzy decomposition theorem. A numerical example evidences the remarkable accuracy and effectiveness of the proposed methods to solve engineering structural–acoustic problems with hybrid uncertain parameters.     

Free vibration analysis of a rotating hub–functionally graded material beam system with the dynamic stiffening effect

A comprehensive dynamic model of a rotating hub–functionally graded material (FGM) beam system is developed based on a rigid–flexible coupled dynamics theory to study its free vibration characteristics. The rigid–flexible coupled dynamic equations of the system are derived using the method of assumed modes and Lagrange's equations of the second kind. The dynamic stiffening effect of the rotating hub–FGM beam system is captured by a second-order coupling term that represents longitudinal shrinking of the beam caused by the transverse displacement. The natural frequencies and mode shapes of the system with the chordwise bending and stretching (B–S) coupling effect are calculated and compared with those with the coupling effect neglected. When the B–S coupling effect is included, interesting frequency veering and mode shift phenomena are observed. A two-mode model is introduced to accurately predict the most obvious frequency veering behavior between two adjacent modes associated with a chordwise bending and a stretching mode. The critical veering angular velocities of the FGM beam that are analytically determined from the two-mode model are in excellent agreement with those from the comprehensive dynamic model. The effects of material inhomogeneity and graded properties of FGM beams on their dynamic characteristics are investigated. The comprehensive dynamic model developed here can be used in graded material design of FGM beams for achieving specified dynamic characteristics.     

Elemental and phase composition analysis of hydrogen-sensitive Pd/Mg–Ni films

A magnesium–nickel (Mg–Ni) film with a palladium (Pd) overcoat is switchable between a conducting metallic state and a semiconducting state through hydridation and dehydridation processes. The Pd overcoat is added to suppress possible oxidation of the alloy layer. However, some Pd and oxygen (O) atoms are still able to diffuse into the alloy layer, such that the distributions of elemental and phase compositions along the direction of depth are quite complicated. In this work, we propose a method to obtain more detailed information on the elemental and phase compositions in a Pd/Mg–Ni film by means of analyzing Pd 3d_5/2, Pd 3p_3/2, Ni 2p_3/2, Mg 1s and O 1s photoelectron spectra. The method was applied to analyze a typical Pd/Mg–Ni film sample. Results verified that Pd can diffuse into the alloy layer. An Mg–O phase is formed near the surface. An Mg–Ni alloy phase dominates at deeper regions. The Mg–Ni phase contains 80% of the total number of atoms in the film, and is non-stoichiometric and highly disordered. Nevertheless, it can give a remarkable change of electrical resistivity during hydridation–dehydridation processes. PACS 79.60.-i; 61.05.C-; 79.60.Ht     

Characterization,electrical and magnetic properties of PVA films filled with FeCl3–MnCl2 mixed fillers

Polyvinyl alcohol (PVA) films filled with different filling levels (FLs) of XFeCL₃(15−X)MnCl₂ were studied. The DSC thermograms exhibited an increase in the melting temperature with filling, indicating better thermal stability of the filled polymer of interesting industrial applications. The amorphous feature of the filled polymer was depicted using XRD scans. Vibrational studies displayed significant structural deformations. The FL dependence of certain IR absorption peaks was discussed. The dc electrical conduction mechanism was interpreted on the basis of the modified interpolaron hopping model. The present results of the dc magnetic susceptibility (χ) suggested the temperature dependence of Curie–Weiss behavior characterized by localized magnetic moments. The effective paramagnetic moment (μ_eff) was estimated; its dependence on the FL exhibited a non-linear character. The electron spin resonance (ESR) study revealed unresolved broad distorted signals characterized by the hyperfine structure. The ESR parameters were evaluated. A correlation between the above-mentioned studies was discussed to relate the structural, electrical and magnetic properties of the filled PVA polymer.     

Investigation of sound field for a standing wave tube system with flow and with lateral Helmholtz resonator Ⅰ. Theoretical analysis

A lateral Helmholtz resonator added to a standing wave tube without flow has been validated as a method of noise reduction for combustion noise radiated from combustion channel of rockets or turbines. But in fact there is a flow with low velocity in the combustion channel. Therefore the theoretical analysis carried out is aimed at sound field of standing wave tube with flow and with lateral Helmholtz resonator. Certainly a relevant math-physical model should first be formulated. Here three key problems need to be solved: (1) To formulate the discontinuity condition at the joint between the standing wave tube and Helmholtz resonator in the case of flow. (2) To determine the acoustic impedance of Helmholtz resonator, considering the effects of flow, viscous and multihole. (3) To formulate the reflection condition at the end of the standing wave tube. Some formulas for analysis of the sound field in the tube with flow and with lateral Helmholtz resonator are deduced. These theoretical works have been validated by experiments.     

Chain structures and clusters of particles with the mixed dipole–quadrupole interaction in smectic freely suspended nanofilms

The formation of unusual chain structures and clusters of particles with the mixed dipole–quadrupole interaction has been found in smectic nanofilms. Unlike topological dipoles and quadrupoles, the interaction between which leads to the formation of structures with finite interparticle distances, the particles with the mixed interaction touch each other and form stable chains and two-dimensional clusters. The orientation of particles in chains is intermediate between dipole and quadrupole chains. The variation of the interparticle distance and orientation of chains is explained qualitatively on the basis of the calculation of the с-director (field lines) near particles and the mutual arrangement of particles providing the minimum distortion of field lines.     

New solutions for conformable fractional Nizhnik–Novikov–Veselov system via $$G'/G$$ expansion method and homotopy analysis methods

The main purpose of this paper is to find the exact and approximate analytical solution of Nizhnik–Novikov–Veselov system which may be considered as a model for an incompressible fluid with newly defined conformable derivative by using \(G'/G\) expansion method and homotopy analysis method (HAM) respectively. Authors used conformable derivative because of its applicability and lucidity. It is known that, the NNV system of equations is an isotropic Lax integrable extension of the well-known KdV equation and has physical significance. Also, NNV system of equations can be derived from the inner parameter-dependent symmetry constraint of the KP equation. Then the exact solutions obtained by using \(G'/G\) expansion method are compared with the approximate analytical solutions attained by employing HAM.     

Simulation and analysis of dispersion compensation schemes for 100 Gbps PDM–OFDM optical communication system

In this paper, the implementation of 100 Gbps optical communication system exploiting polarization diversity at transmitter and receiver is developed and investigated with pre-, post- and symmetrical dispersion compensation schemes by using dispersion shifted and dispersion compensated fibers through simulations to optimize high data rate optical transmission. Motivation to the current analysis is to compare all 3 compensation schemes and it's found that the pre compensation technique is superior to post and symmetrical compensation techniques in 100 Gbps PDM–OFDM communication system. On examination of symmetrical and post dispersion compensation schemes, it's found that the later is superior to the previous in this case. A 100 Gbps coherent optical OFDM workplace has been discovered in which two 50 Gbps data streams are combined into one wavelength by polarization beam combiner. By comparing one can get a promising system to the symmetrical high capacity access network with high spectral efficiency, cost effective, good flexibility.     

Rotational and vibrational analysis of bands of the f1Δ-a1Δ system of titanium oxide

Five new bands of the f¹Δ-a¹Δ TiO system have been observed in emission between 17774.0 cm^?1 and 19801.0 cm^?1. Rotational and vibrational analyses of the 0-1, 1-0, 1-2, 2-1, and 1-1 bands, as well as a reanalysis of the 0-0 band, yielded the following molecular constants (cm^?1):

     

20.

An optimal analysis for Darcy–Forchheimer 3D flow of nanofluid with convective condition and homogeneous–heterogeneous reactions     

Tasawar Hayat  Arsalan Aziz  Taseer Muhammad  Ahmed Alsaedi 《Physics letters. A》2018,382(39):2846-2855

Here Darcy–Forchheimer 3D stretching flow of nanoliquid in the presence of convective condition and homogeneous–heterogeneous reactions is analyzed. Impacts of thermophoresis, Brownian diffusion and zero nanoparticles mass flux condition are considered. Adequate transformation procedure give rise to system in terms of ordinary differential equations. The governing mathematical system has been tackled by optimal homotopic technique. Graphical results have been presented for temperature and concentration dsitributions. Numerical benchmark is provided to study the values of skin friction coefficients and local Nusselt number. Skin friction coefficients are declared increasing functions of porosity and Forchheimer parameters. Furthermore the local Nusselt number is reduced for larger values of porosity and Forchheimer parameters.     

		$\text{f}{}^1\text{Δ}$		$\text{a}{}^1\text{Δ}$
v	$\text{B}{}_{\mathrm{v}}$	$\text{D}{}_{\mathrm{v}}$ (×106)	$\text{B}{}_{\mathrm{v}}$	$\text{D}{}_{\mathrm{v}}$ (×106)
0	0.502277 (17)	0.6411 (57)	0.536168 (20)	0.5938 (76)
1	0.499198 (32)	0.630 (15)	0.533227 (13)	0.5971 (46)
2			0.530335 (26)	0.636 (13)
	$\text{ω}{}_{\mathrm{e}}\text{= 874.104 (4)}$		$\text{ω}{}_{\mathrm{e}}\text{= 1018.273 (4)}$
	$\text{ω}{}_{\mathrm{e}}\text{χ}{}_{\mathrm{e}}\text{= 2.501 (4)}$		$\text{ω}{}_{\mathrm{e}}\text{χ}{}_{\mathrm{e}}\text{= 4.521 (4)}$
	$\text{T′}{}_{\mathrm{e}}\text{?T″}{}_{\mathrm{e}}\text{= 19140.567 (8)}$

An optimal analysis for Darcy–Forchheimer 3D flow of nanofluid with convective condition and homogeneous–heterogeneous reactions

Here Darcy–Forchheimer 3D stretching flow of nanoliquid in the presence of convective condition and homogeneous–heterogeneous reactions is analyzed. Impacts of thermophoresis, Brownian diffusion and zero nanoparticles mass flux condition are considered. Adequate transformation procedure give rise to system in terms of ordinary differential equations. The governing mathematical system has been tackled by optimal homotopic technique. Graphical results have been presented for temperature and concentration dsitributions. Numerical benchmark is provided to study the values of skin friction coefficients and local Nusselt number. Skin friction coefficients are declared increasing functions of porosity and Forchheimer parameters. Furthermore the local Nusselt number is reduced for larger values of porosity and Forchheimer parameters.