Three-step Scheme Research Articles

Throughput Maximization for Cognitive Radio With Wirelessly Powered Primary Users

This article deals with resource allocation to maximize the secondary user (SU) throughput in cognitive radio where primary users (PUs) are wirelessly powered by SU signals during the first part of a time-slot, and PUs and SUs share the spectrum during the second part of the time-slot. An optimization problem is formulated to maximize SU throughput under a constraint of minimum PU throughput (due to quality-of-service). As the optimization problem is NP-hard, we decompose the problem into two subproblems by introducing an auxiliary variable, i.e., the consumed energy at PU, and the subproblems are decoupled by minimizing the PU consumed energy. A three-step resource allocation scheme is then proposed to solve the optimization problem with low complexity. Numerical simulations are provided to demonstrate the superiority of the proposed scheme in terms of both performance and computational complexity.

A Study of Laser Photoionization of 177mLu Nuclear Isomer

The hyperfine structure of transitions of the three-step photoionization scheme of lutetium, 5d6s2 2D3/2−5d6s6p 4F$$_{{5/2}}^{^\circ }$$−5d6s7s 4D3/2−(53 375 cm–1)$$_{{1/2}}^{^\circ }$$, for 177mLu nuclear isomer has been investigated for the first time by laser resonance photoionization mass spectroscopy. Hyperfine-splitting constants, energy levels, and magnetic dipole and electrical quadrupole moments of the 177mLu nucleus are determined. Isotope shifts of the isomer spectral lines relative to natural isotopes and 177Lu have been investigated.

Multi-scale sensitivity analysis of structural vibration behaviors of three-dimensional braided composites with respect to material properties

Three-dimensional braided composites have a wide range of application in various industries. This article presents a three-step scheme enabling the multi-scale analysis of the vibration properties for three-dimensional braided composites. Firstly, a micro-scale model and meso‑scale mechanical model were constructed to predict the stiffness properties of the braided composites using both analytical and numerical methods. Secondly, the macro-scale vibration responses of the braided composites were carefully investigated both from analytical and numerical perspectives, followed by validation with experimental data. Thirdly, sensitivity analysis of the vibration properties, such as the modal frequencies, with respect to the braiding angle, fiber volume fraction, and braided structure was conducted. The results show that the macroscopic vibration properties strongly depend on the braiding angle, fiber volume fraction, and braided structure. Three-dimensional braided composites are quite promising for the integrated design of materials and structures, as their macroscopic structural vibration behaviors can be optimized by properly regulating their microscopic material characteristics.

Thermal Analysis and Cone Calorimeter Study of Engineered Wood with an Emphasis on Fire Modelling

Engineered wood products (EWPs) are a group of materials having a very similar chemical composition but having different and non-uniform thermo-physical properties throughout their thickness. Such materials present a significant challenge from the pyrolysis modelling point of view. The main focus of the paper is to study and compare the differences between six EWPs—oriented strand board (OSB), plywood, particle board (PB), low-density (LDF), medium-density (MDF) and high-density (HDF) fibreboard—in terms of their pyrolysis and burning behaviour. Vertical density profiles (VDPs), thermal degradation behaviour, and burning behaviour were studied and compared. There is a considerable need for a consistent and systematic approach in estimating pyrolysis model complexity and model input parameters. A systematic method to determine the minimum level of the EWPs decomposition model complexity to reproduce the thermal degradation behaviour as measured using thermogravimetric analysis and using the set of parallel reactions was applied. EWPs were found to have similar thermal decomposition onset and range. Maximal decomposition rates were within 25%. OSB, PB, LDF and HDF decomposition can be modelled using three-step parallel reactions scheme, MDF using four parallel reactions. A set of parallel reactions cannot describe the thermal degradation behaviour of plywood. Cone calorimeter tests at heat flux levels of 20 kW/m2, 50 kW/m2 and $$80\, \hbox {kW}/\hbox {m}^{2}$$ revealed that influence of the different thermo-physical properties on time to ignition and time to peak heat release rate (HRR) is not significant except LDF and HDF due to their very different density. Peak HRR varies between EWPs, which is attributed primarily to charring and different thermo-physical properties of the EWPs char. EWPs gas phase combustion parameters for the fire models were derived.

Efficient Rationalization of Triplet Halfband Filter Banks and its Application to Image Compression

This paper presents a novel approach for rationalization of irrational coefficients of filters designed using three-step lifting scheme. The existing three-step lifting schemes result in the irrational filter coefficients which require infinite precision for implementation. In this work, Euler-Frobenius halfband polynomials are designed to obtain the required kernels of three-step lifting structure. Next, the efficient rationalization of the designed filter banks (FBs) is proposed to reduce the arithmetic complexity. The proposed rational FBs preserve perfect reconstruction, near-orthogonality and regularity properties of wavelet FBs. These filters with rational coefficients are then used in image compression algorithms to compress the test images in well-known Classic, EPFL, RAISE, FiveK datasets and chromosome image datasets. The performance of the proposed rational FBs is compared with the existing rational FBs. It is observed that the performance of the proposed rational FBs is improved in terms of computational cost, encoding-decoding time and compression ratio as compared to existing rational FBs.

Principles of tRNAAla Selection by Alanyl-tRNA Synthetase Based on the Critical G3·U70 Base Pair.

Throughout evolution, the presence of a single G3·U70 mismatch in the acceptor stem of tRNAAla is the major determinant for aminoacylation with alanine by alanyl–tRNA synthetase (AlaRS). Recently reported crystal structures of the complexes AlaRS–tRNAAla/G3·U70 and AlaRS–tRNAAla/A3·U70 suggest two very different conformations, representing a reactive and a nonreactive state, respectively. On the basis of these structures, it has been proposed that the G3·U70 base pair guides the −CCA end of the tRNA acceptor stem into the active site of AlaRS, thereby enabling aminoacylation. The crystal structures open up the possibility of directly computing the energetics of tRNA specificity by AlaRS. We have carried out molecular dynamics free-energy simulations to quantitatively estimate tRNA discrimination by AlaRS, focusing on the mutations of the single critical base pair G3·U70 to uncover the energetics underlying the accuracy of tRNA selection. The calculations show that the reactive complex is highly selective in favor of the cognate tRNAAla/G3·U70 over its noncognate analogues (A3·U70/G3·C70/A3·C70). In contrast, the nonreactive complex is predicted to be unselective between tRNAAla/G3·U70 and tRNAAla/A3·U70. Utilizing our calculated relative binding free energies, we show how a simple three-step kinetic scheme for aminoacylation, involving both an initial nonspecific binding step and a subsequent transition to a selective reactive complex, accounts for the observed kinetics of the process.

Accuracy of the aerodynamic performance of wind turbines using vortex core models in the free vortex wake method

The size of the vortex core of the vortex model is very important for the accurate prediction of the aerodynamic characteristics of wind turbines in the free vortex wake (FVW) method. The size of the vortex core includes its initial radius and the variation in the wake due to the dissipation effect. In the FVW method, the governing equation of the vortex line is discretized by the three-step and third-order predictor-corrector difference scheme. The classical Lamb-Oseen model and the Scully model are adopted for the vortex core model, and the vortex dissipation effect and stretching effect are taken into account. First, the value range of the initial radius of the vortex core is obtained through the analysis of the aerodynamic load and the mean value of the tip vorticity. Then, based on the tip vortex dissipation characteristics, the empirical constants reflecting the increase in the vortex core radius are determined. Finally, the effect of the vortex core size on the shape of the tip vortex line is analyzed. The results demonstrate that in both vortex core models when the radius of the initial vortex core is greater than 50% of the chord length, the FVW method converges stably and can accurately predict the aerodynamic load of the wind turbine. Considering the aerodynamic load of the wind turbine and the dissipation characteristics of the tip vorticity, it is advisable to use a chord length from 60% to 70% as the initial radius of the vortex core. In addition, the corresponding empirical constant of vortex-viscous dissipation is also different; the aerodynamic load of the wind turbine which is related to the mean value of the tip vorticity and the shape of the tip vortex is mainly affected by the radius of the initial vortex core, and the empirical constant has little influence on it, while it mainly affects the dissipation characteristics of the tip vorticity in the downstream wake field.

Millimeter-wave spectroscopy of Zn I in triplet F Rydberg states

We continue our experiments on millimeter-wave spectroscopy of higly-excited Rydberg atoms with two valence electrons. In this work we have measured frequencies of 16 transitions between Rydberg triplet 4snf3FJ and singlet 4snd1D2, 4sng1G4 levels of neutral zinc (Zn I) in the frequency range 87–141 GHz and in the principal quantum number range n=30–37. The observed transitions were driven predominantly from triplet 4snf3F3 levels that were excited by a three-step laser excitation scheme 4s21S0 → 4s4p3P1 → 4s4d3D2 → 4snf3F3. The measured frequencies as well as those obtained in our previous work (Kutsenko et al., 2015, J. Phys. B: At. Mol. Opt. Phys. 48, 245,005) were used to derive the Ritz expansion coefficients for triplet F states in the framework of the single-channel quantum defect theory.

An inverse modeling approach for predicting filled rubber performance

In this paper, a computational procedure combining experimental data and interphase inverse modeling is presented to predict filled rubber compound properties. The Fast Fourier Transformation (FFT) based numerical homogenization scheme is applied on the high quality filled rubber 3D Transmission Electron Microscope (TEM) image to compute its complex shear moduli. The 3D TEM filled rubber image is then compressed into a material microstructure database using a novel Reduced Order Modeling (ROM) technique, namely Self-consistent Clustering Analysis (a two-stage offline database creation from training and learning, followed by data compression via unsupervised learning, and online prediction approach), for improved efficiency and accuracy. An inverse modeling approach is formulated for quantitatively computing interphase complex shear moduli in order to understand the interphase behaviors. The two-stage SCA and the inverse modeling approach formulate a three-step prediction scheme for studying filled rubber, whose loss tangent curve can be computed in agreement with test data.

Mechanism and predictive model development of reaction rate constants for N-center radicals with O2

Atmospheric oxidation of NHx-containing (x = 1, 2) compounds can produce N-center radicals, a precursor of toxic nitrosamines. The reaction rate constant (kO2) with O2 has been considered as an important parameter to determine the nitrosamines yield in the subsequent reactions of N-center radicals. However, available kO2 values of N-center radicals are limited. Here, a three-step scheme including mechanistic analysis and kinetics calculation of the reactions of 28 various N-center radicals with O2, and model development was taken to solve the kO2 data shortage. Mainly employed tools include highly cost-expensive coupled-cluster theory (CCSD(T)), kinetic model and statistics. The results indicate that the direct H-abstraction pathway is the most favorable for the reactions of all considered N-center radicals with O2. The specific molecular conformation and the C–H bond energy of the N-center radicals are two important factors to determine kO2 values. Based on the mechanistic understanding of kO2 values, a quantitative structure-activity relationship (QSAR) model of kO2 values was developed. The model has satisfactory goodness-of-fit, robustness and predictive ability. The determined kO2 values and the in silico methods provide a scientific base for assessing formation risk of toxic nitrosamines in the atmosphere.

Acidification and decarbonization in seawater: Potential pretreatment steps for biofouling control in SWRO membranes

Biofouling of seawater reverse osmosis (SWRO) membranes is a major problem that SWRO freshwater production facilities face worldwide. A three-step pretreatment scheme, initially designed to assist the SWRO process in boron rejection, was examined as a potential membrane biofouling inhibitor. The conventional pretreatment procedure in this study includes acidification, CO2 stripping and pH elevation, and its effect on planktonic cell mortality and biofilm formation on the membrane was analyzed. An in-situ electrolytic production of free chlorine in seawater, during the low pH phase, was suggested as an additional pretreatment step, with the goal of serving as an aggressive disinfection course. In addition, 48-hour enhanced biofouling experiments using an RO membrane cell assembly were conducted in order to observe the flux decline pattern as affected by the various treatments. The conventional pretreatment scheme was found to have a moderate effect on membrane biofouling, increasing the membrane permeability by 25% relative to an untreated experimental run. Moreover, the conventional pretreatment did not significantly promote cell mortality; however, it caused an increase in extracellular polysaccharide production during biofilm formation. The additional chlorination step increased the biofouling phenomenon, causing the production of particulate matter, likely due to cell wall oxidation.

An Effective Classification Scheme for Hyperspectral Image Based on Superpixel and Discontinuity Preserving Relaxation

Hyperspectral image (HSI) classification is one of the most active topics in remote sensing. However, it is still a nontrivial task to classify the hyperspectral data accurately, since HSI always suffers from a large number of noise pixels, the complexity of the spatial structure of objects and the spectral similarity between different objects. In this study, an effective classification scheme for hyperspectral image based on superpixel and discontinuity preserving relaxation (DPR) is proposed to discriminate land covers of interest. A novel technique for measuring the similarity of a pair of pixels in HSI is suggested to improve the simple linear iterative clustering (SLIC) algorithm. Unlike the existing application of SLIC technique to HSI, the improved SLIC algorithm can be directly used to segment HSI into superpixels without using principal component analysis in advance, and is free of parameters. Furthermore, the proposed three-step classification scheme explores how to effectively use the global spectral information and local spatial structure of hyperspectral data for HSI classification. Compared with the existing two-step classification framework, the use of DPR technology in preprocessing significantly improves the classification accuracy. The effectiveness of the proposed method is verified on three public real hyperspectral datasets. The comparison results of several competitive methods show the superiority of this scheme.

Pilot-scale electro-kinetic remediation of lead polluted field sediments: model designation, numerical simulation, and feasibility evaluation

BackgroundThe accumulation of lead (Pb) in sediments from anthropogenic activities possesses serious threats to ecosystem and human health. Recycling of sediments for agricultural plantation is politically encouraged while their applications are still limited due to the high cost and poor environmental compatibility of existing remediation techniques. Electro-kinetic remediation (EKR) enhanced with electrode polarity inversion (EPI) strategy was an effective technique for Pb decontamination from low permeable matrix. However, lacking full understanding of the interactions between Pb and sediment constituents restricts the wide application of this technology.ResultsIn this study, an innovative approach based on model simulation and feasibility analysis was proposed for guiding the pilot-scale remediation and recycling of Pb-polluted sediments. Initially, a specific two-dimensional (2D) model that consisted of transport-reactive modules was designed, with assumptions of operating parameters and reaction equations. A three-step sequential non-iterative split-operator computation scheme was implemented to simulate the electrochemical variables of EKR. The predicted results indicated that the electrode reversal should be conducted around 48 h to avoid pH polarization and Pb precipitation. In addition, 12 h was suggested to be the preferable EPI duration as the shortest time required (226 h) to remove the target level of sediment Pb. Afterwards, a comparative study was performed between the experimental and simulated data to validate the model accuracy. Good agreements were achieved in spite of minor discrepancies which suggested the designed model could approximately predict the performance of EPI-enhanced EKR. Finally, the feasibility analysis was conducted based on a parametric study. In consideration of energy utilization efficiency, concentration of 220 mg/kg was determined as the lower limit of safety threshold for Pb removal. In this level, the maximum energy consumption (EC), materials, electrolyte post-treatment, and labor expenditure for sediments remediation were 110 $/m3, 450 $/remediation unit, 2 $/L, and 300 $/remediation unit, respectively, and the agricultural eco-environment was safe during the recycling process.ConclusionWe believed that the methodology and results in this study could be employed as an useful tool to support the designation of full-scale EKR and the reutilization of contaminated sediments.

A splitting method adapted to the simulation of mixed flows in pipes with a compressible two-layer model

The numerical resolution of the Compressible Two-Layer model proposed in [27] is addressed in this work with the aim of simulating mixed flows and entrapped air pockets in pipes. This five-equation model provides a unified two-phase description of such flows which involve transitions between stratified regimes (air–water herein) and pressurized or dry regimes (pipe full of water or air). In particular, strong interactions between both phases and entrapped air pockets are accounted for. At the discrete level, the coexistence of slow gravity waves in the stratified regime with fast acoustic waves in the pressurized regime is difficult to approximate. Furthermore, the two-phase description requires to deal with vanishing phases in pressurized and dry regimes. In that context, a robust splitting method combined with an implicit-explicit time discretization is derived. The overall strategy relies on the fast pressure relaxation in addition to a mimetic approach with the shallow water equations for the slow dynamics of the water phase. It results in a three-step scheme which ensures the positivity of heights and densities under a CFL condition based on the celerity of material and gravity waves. In that framework, an implicit relaxation-like approach provides stabilization terms which are activated according to the flow regime. Numerical experiments are performed beginning with a Riemann problem for the convective part. The overall approach is then assessed considering relevant mixed flow configurations involving regime transitions, vanishing phases and entrapped air pockets.

Development of a novel scheme for rapid screening for environmental micropollutants in emergency situations (REPE) and its application for comprehensive analysis of tsunami sediments deposited by the great east Japan earthquake

The tsunami triggered by the Great East Japan Earthquake of March 2011, the strongest quake ever recorded in Japan, deposited tsunami sediments along the coastline of the affected area. Because the sediments contained a wide variety of hazardous chemicals, including organic micropollutants, a method for rapidly evaluating the environmental and human health risks of such chemicals is necessary. For this purpose, we propose a novel three-step scheme designated “rapid screening for environmental micropollutants in emergency situations (REPE)”. In the first step, samples are subjected to target screening analysis using an automated identification and quantification system (TSA-AIQS) involving gas chromatography mass spectrometry (GC-MS). In the second step, the chemicals detected by TSA-AIQS analysis are quantified precisely by conventional target analysis. The third step is risk assessment of the target chemicals. TSA-AIQS analysis of the tsunami sediments detected 63 substances, including polycyclic aromatic hydrocarbons (both native and alkylated PAHs) at high concentrations. These PAHs were precisely quantified by target analysis, and the concentrations were used to assess the health risks posed by oral intake, which were found to be negligible. Our results suggest that the REPE scheme will be useful for rapid, comprehensive screening and risk assessment in emergency situations.

ON A CLASS OF EFFICIENT HIGHER ORDER NEWTON-LIKE METHODS

Based on a two-step Newton-like scheme, we propose a three-step scheme of convergence order p+2 (p >=3) for solving systems of nonlinear equations. Furthermore, on the basis of this scheme a generalized k+2-step scheme with increasing convergence order p+2k is presented. Local convergence analysis including radius of convergence and uniqueness results of the methods is presented. Computational efficiency in the general form is discussed. Theoretical results are verified through numerical experimentation. Finally, the performance is demonstrated by the application of the methods on some nonlinear systems of equations.

Исследование схемы селективной фотоионизации -=SUP=-177-=/SUP=-Lu

AbstractThe hyperfine structure of transitions in the three-step scheme 5 d 6 s ^22 D _3/2–5 d 6 s 6 p ^4 F $$_{{5/2}}^{^\circ }$$ –5 d 6 s 7 s ^4 D _3/2– (53 375 cm^–1) $$_{{1/2}}^{^\circ }$$ of lutetium ionization is studied for ^175Lu, ^176Lu, and ^177Lu isotopes using the photoionization laser spectroscopy method. Values of the magnetic dipole ( A ) and electric quadrupole ( B ) interaction constants are determined, as well as the energies, the isotope shifts, and the radiative lifetimes for the 5 d 6 s 7 s ^4 D _3/2 and (53 375 cm^–1) $$_{{1/2}}^{^\circ }$$ levels.

A Stable Difference Scheme for a Third-Order Partial Differential Equation

The nonlocal boundary-value problem for a third order partial differential equation in a Hilbert space H with a self-adjoint positive definite operator A is considered. A stable three-step difference scheme for the approximate solution of the problem is presented. The main theorem on stability of this difference scheme is established. In applications, the stability estimates for the solution of difference schemes of the approximate solution of three nonlocal boundary value problems for third order partial differential equations are obtained. Numerical results for oneand two-dimensional third order partial differential equations are provided.

Study of a Selective Photoionization Scheme of 177Lu

The hyperfine structure of transitions in the three-step scheme 5d6s22D3/2–5d6s6p4F $$_{{5/2}}^{^\circ }$$ –5d6s7s4D3/2– (53 375 cm–1) $$_{{1/2}}^{^\circ }$$ of lutetium ionization is studied for 175Lu, 176Lu, and 177Lu isotopes using the photoionization laser spectroscopy method. Values of the magnetic dipole (A) and electric quadrupole (B) interaction constants are determined, as well as the energies, the isotope shifts, and the radiative lifetimes for the 5d6s7s4D3/2 and (53 375 cm–1) $$_{{1/2}}^{^\circ }$$ levels.

Three-Step Averaging Scheme for Set-Valued Differential Equations with Generalized Derivative

We substantiate applicability of a three-step averaging scheme to set-valued differential equations with generalized derivative.