Selective Mapping Research Articles

Microstructure selection map for rapidly solidified Al-rich Al–Sr alloys

Abstract The effect of rapid solidification on the microstructure of Al-5Sr, Al-10Sr and Al-23Sr (wt.%) alloys has been investigated using X-ray diffraction and transmission electron microscopy. The phases present in the melt-spun Al –Sr alloys are the equilibrium phases a-Al and tetragonal Al4Sr. The microstructure of the melt-spun Al –Sr alloys is quite different from that of the ingot-like alloys. Microstructure selection map is established for the rapidly solidified Al-rich Al –Sr alloys, in light of the microstructure together with the estimated cooling rates. The undercooling obtained through quenching at ≈ 9.5 × 105 K s–1 is sufficient for the Al-10Sr alloy but insufficient for the Al-23Sr alloy to completely suppress the formation of primary Al4Sr. Rapid solidification has a significant effect on the morphology of primary Al4Sr and the higher level of undercooling enhances the formation of the Al4Sr dendrites with 45° branches in the melt-spun Al-23Sr alloy.

Enhanced SLM based OFDM-DCSK communication system for PAPR reduction

In this research, a selective mapping (SLM) technique using the Walsh Hadamard (WH) matrix, the Riemann matrix, and the new enhanced Riemann matrix were introduced to reduce the peak to average power ratio (PAPR) of orthogonal frequency division multiplexing based differential chaos shift keying (OFDM-DCSK). Using a new algorithm to reduce the size of the Riemann matrix, which in turn enhances the computational complexity of the SLM system without affecting the performance of PAPR in the main method. The simulation results show that the SLM technique using the Riemann matrix gives better PAPR performance than WH and conventional techniques by gaining about (6.3, 6.15) dB, respectively, for complementary cumulative distribution function (CCDF)=10-3 and the number of candidates U=16. Also, the results show that the SLM technique based enhanced Riemann matrix gives a reduction in computational complexity by reducing the number of candidates U to 4, while maintaining the same PAPR performance.

Elevated temperature compression behaviors of 3D printed hollow pyramidal lattice sandwich structure reinforced by truncated square honeycomb

This paper focuses on the influence of temperatures on the out-of-plane compressive performance of novel truncated-square honeycomb reinforced hollow pyramidal lattice sandwich structure (TSH-HP) by combining theoretical prediction, experiment and finite element analysis. As the temperature go up from 25 ℃ to 450 ℃, compressive modulus, initial failure strength, peak strength and energy-absorption performance of TSH-HPs prepared by selective laser melting (SLM) techniques decrease by 46.2%, 46.9% 42.3% and 46.3%, respectively, which are in well agreement with experiment and numerical simulation. In addition, the initial failure strength and peak strength of TSH-HPs are 5–10% higher than those of hollow pyramid lattice structure (HP) with same mass under different temperature. Compared with competing cellular materials, TSH-HPs exhibit superiority in the specific strength on the material selection map.

PEAK TO AVERAGE POWER RATIO REDUCTION TECHNIQUES

The most extensively used wireless communication system Multiple input multiple affair and orthogonal frequency division multiplexing because of their large benefits and advantages. MIMO OFDM has a major debit which makes the system noisy because of the harpoons in the transmitting signal. Harpoons produce noice and deformation. Different ways are used to avoid these harpoons. Then we use three styles which are styles videlicet partial transmit sequence, clipping and filtering system, selective mapping technique. These styles are used to reduce the high peak to average rate by removing the harpoons in the signal. WE will see labors using MATLAB. This paper will discuss how MATLAB software is employed to decrease the PAPR within the MIMO OFDM systems. The very best rate of energy efficiency (PAPR) is that the major regression of the OFDM system reducing the performance of the transmitted signal.

A simple and effective multi-focus image fusion method based on local standard deviations enhanced by the guided filter

This paper develops a simple and effective multi-focus image fusion method based on local standard deviations of the corresponding Laplacian images of source images and further enhanced by the guided filter. The underlying idea of this pixel-based approach is that the sharper pixels generally should have a comparatively higher local variance and hence higher local standard deviation. We first apply the Laplacian operation on each partially focused source image of the same scene, estimate the local standard deviation for each pixel, and enhance the local standard deviations using the guided filter. We then employ the filtered local standard deviation of the Laplacian image as an initial focus measure and combine it with the small region removal strategy to construct a decision map for pixel selection. Finally, according to the decision map, the target all-in-focus fused image is formed pixel-by-pixel. A variant of the proposed method with further guided filtering on the decision map is also developed. Numerical results demonstrate the proposed methods’ high performance compared with some state-of-the-art techniques.

A Novel Peak-to-Average Power Ratio Reduction for 5G Advanced Waveforms

Multi and single carrier waveforms are utilized in cellular systems for high-speed data transmission. In The Fifth Generation (5G) system, several waveform techniques based on multi carrier waveforms are proposed. However, the Peak to Average Power Ratio (PAPR) is seen as one of the significant concerns in advanced waveforms as it degrades the efficiency of the framework. The proposed article documents the study, progress, and implementation of PAPR reduction algorithms for the 5G radio framework. We compare the PAPR algorithm performance for advanced and conventional waveforms. The simulation results reveal that the advanced Partial Transmission Sequence (PTS) and Selective Mapping (SLM) methods enhanced the throughput and gain of the 5G waveforms. Furthermore, we have also analyzed the performance of Orthogonal Time Frequency Space Modulation (OTFSM) based on a single carrier system and found that PAPR is significantly low and is best suited to fading environments. It is seen that the conventional algorithms lower the PAPR but increase the complexity. The proposed PTS and SLM have shown good performance with low computational complexity.

Investment of Cyclic Prefix to Reduce the Peak-to-Average Power Ratio and Recover Original Phases Blindly

When dealing with the phenomenon of unexpected high peak-to-average power ratio (PAPR) caused by multicarrer techniques, it is rarely to find a proposed solution that addresses the most important challenges together, that are; reducing the PAPR, achieving performance identical, mostly, to the theoretical curve and a reasonable level of computational complexity. This paper presents a new proposal that is able to achieve these three criteria together as the following. First, reducing the PAPR curves through easy development in the selective mapping (SLM) structure. Second, identifying the original transmitted phase block by taking advantage of the cyclic prefix structure and its mechanism, without any explicit side information, while maintaining the system performance. Lastly, these achievements were obtained at low computational complexity comparing to the traditional methods of SLM PAPR reduction schemes. This proposed method is referred to as; Injected and Extracted Short-SLM to and from the Cyclic Prefix (IES-SLM-CP). The appropriate short phase sub-block is injected to a specific locations of CP, and at the receiver side, this sub-block can be extracted from the CP to reconstruct the whole original phase block.

A Construction Method of Phase Sequences for the Selected Mapping Scheme

In this paper, a construction method of phase sequences is proposed for the selected mapping (SLM) scheme. Three principles are applied to the construction process: periodicity, binary (±1), and maximization of the minimum Hamming distance between different sequences. Using the first and second principle, except the original frequency signal, the calculation process of other candidate time signals can be simplified as the linear addition of some intermediate signals, which are obtained in the inverse fast Fourier transform (IFFT) operation of the original frequency signal. Using the third principle, greater differences can be generated between different candidate signals, which is helpful to improve the peak-to-average power ratio (PAPR) reduction performance. Theoretical analysis and simulation results show that, with the help of new phase sequences, the SLM scheme can effectively reduce the computational complexity, while it shows almost the same performance of PAPR reduction as that of the traditional SLM scheme, whose phase sequences are from the odd row vectors in the Hadamard matrix.

Performance Analysis of PTS PAPR Reduction Method for NOMA Waveform

Cellular systems utilize single and multicarrier waveforms for high-speed data transmission. The Fifth-Generation (5G) system proposes several techniques based on multicarrier waveforms. However, the Peak to Average Power Ratio (PAPR) is one of the significant concerns in advanced waveforms as it degrades the framework's efficiency. Non Orthogonal Multiple Access (NOMA) can provide massive connectivity, which is the crucial requirement of the Internet of Things (IoT). The 3rd generation tested NOMA applications in downlink and uplink transmission. However, NOMA uplink transmission in the power domain has performance degradation and is not considered a possible technique in 3rd generation power projects (3GPP). Presently, NOMA is not just a concept but has been introduced as a standard method in various transmission schemes. NOMA suffers from a high peak to average power ratio (PAPR), which forces the power amplifier (PA) to shift into a nonlinear region. The high value of PAPR leads the power amplifier of the multicarrier technique into a nonlinear region. As the performance of the power amplifier degrades, the overall system performance goes down. In this work, we suggest different methods to overcome the issue of PAPR in multicarrier techniques such as Selective Mapping (SLM) and Partial Transmit Sequence (PTS). The simulation results reveal that the performance of the proposed PTS is better than that of the conventional SLM and PTS.

Improved Reptile Search Optimization Algorithm Using Chaotic Map and Simulated Annealing for Feature Selection in Medical Field

The increased volume of medical datasets has produced high dimensional features, negatively affecting machine learning (ML) classifiers. In ML, the feature selection process is fundamental for selecting the most relevant features and reducing redundant and irrelevant ones. The optimization algorithms demonstrate its capability to solve feature selection problems. Reptile Search Algorithm (RSA) is a new nature-inspired optimization algorithm that stimulates Crocodiles’ encircling and hunting behavior. The unique search of the RSA algorithm obtains promising results compared to other optimization algorithms. However, when applied to high-dimensional feature selection problems, RSA suffers from population diversity and local optima limitations. An improved metaheuristic optimizer, namely the Improved Reptile Search Algorithm (IRSA), is proposed to overcome these limitations and adapt the RSA to solve the feature selection problem. Two main improvements adding value to the standard RSA; the first improvement is to apply the chaos theory at the initialization phase of RSA to enhance its exploration capabilities in the search space. The second improvement is to combine the Simulated Annealing (SA) algorithm with the exploitation search to avoid the local optima problem. The IRSA performance was evaluated over 20 medical benchmark datasets from the UCI machine learning repository. Also, IRSA is compared with the standard RSA and state-of-the-art optimization algorithms, including Particle Swarm Optimization (PSO), Genetic Algorithm (GA), Grasshopper Optimization algorithm (GOA) and Slime Mould Optimization (SMO). The evaluation metrics include the number of selected features, classification accuracy, fitness value, Wilcoxon statistical test (p-value), and convergence curve. Based on the results obtained, IRSA confirmed its superiority over the original RSA algorithm and other optimized algorithms on the majority of the medical datasets.

Research on Greenway Route Selection of Traditional Villages Based on GIS: A Case Study of Xingtai County, China

Greenway is a green linear corridor connecting scenic spots, residential areas, nature reserves, road traffic, etc. Rational greenway route selection can not only attract tourists to increase the income of local villages, but also arouse people’s awareness of the protection of traditional villages. This paper took Xingtai County, Hebei Province, China as an example to practice greenway route selection in the county territory. Eight factors were selected for greenway route planning, namely elevation, water body, mountain, ecological protection redline, cultural relics protection units, population density, road traffic network, and important transportation hub. These eight factors were assigned in the GIS platform, and the suitability evaluation system of each factor was constructed. The analytic hierarchy process (AHP) and entropy weight method were combined to calculate the weight of these eight factors. The raster calculator was used to weight and overlay the suitability evaluation system of each factor, and the comprehensive suitability evaluation map of greenway route selection was obtained. Based on an important transport hub, along with the water body and the road traffic, the final selection greenway route of traditional villages in Xingtai county was formed. The results of the research can provide a certain reference for the greenway route selection at the county scale.

Home-range habitat selection by Ferruginous Hawks in western Canada: implications for wind-energy conflicts

Global wind-energy development has increased exponentially in recent decades and is expected to double in capacity in Canada by 2040. Wind-farm development has significant implications for wildlife, particularly for raptors, where injury or death from turbine strikes and other cumulative effects are well documented. Minimizing conflict is important for species at risk, such as the Ferruginous Hawk (<em>Buteo regalis</em>), because negative impacts from wind farms may hinder conservation and recovery actions. Understanding Ferruginous Hawk habitat selection is needed to assess the potential spatial overlap with wind-farm development and make spatially explicit predictions of conflict risk. Our objectives were (1) to develop a predictive map of habitat selection by Ferruginous Hawks at the home-range scale; and (2) to identify areas of high and low potential conflict with current and future wind-energy developments, by overlaying predictive habitat maps with wind potential within the Canadian Ferruginous Hawk range. We showed that landscape composition and configuration, current industrial development, soil characteristics, and seasonal climate influenced Ferruginous Hawk home-range habitat selection. Our risk analyses identified areas at medium to very high risk of conflict with wind energy, but also large areas with low wind-energy development potential and high conservation value that would be valuable for species conservation and management. Importantly, how wind potential is measured has a strong influence on the level of risk. Our habitat model and risk assessment do not replace ground assessments, but can be used during the pre-development phase to proactively site new wind farms away from potential risk for Ferruginous Hawks.

The influence of spontaneous and visual activity on the development of direction selectivity maps in mouse retina.

SUMMARYIn mice, retinal direction selectivity is organized in a map that aligns to the body and gravitational axes of optic flow, and little is known about how this map develops. We find direction selectivity maps are largely present at eye opening and develop normally in the absence of visual experience. Remarkably, in mice lacking the beta2 subunit of neuronal nicotinic acetylcholine receptors (β2-nAChR-KO), which exhibit drastically reduced cholinergic retinal waves in the first postnatal week, selectivity to horizontal motion is absent while selectivity to vertical motion remains. We tested several possible mechanisms that could explain the loss of horizontal direction selectivity in β2-nAChR-KO mice (wave propagation bias, FRMD7 expression, starburst amacrine cell morphology), but all were found to be intact when compared with WT mice. This work establishes a role for retinal waves in the development of asymmetric circuitry that mediates retinal direction selectivity via an unknown mechanism.

PAPR Reduction in Optical OFDM Using Lexicographical Permutations With Low Complexity

Efficient utilization of the spectrum, increased resilience to inter-symbol interference (ISI) and simpler channel equalization are becoming important considerations in the design of wireless communication systems including visible light communication (VLC) systems. In this regard, orthogonal frequency division multiplexing (OFDM) has become a preferred modulation technique in wireless communication systems design. However, one of its major challenges is the high peak-to-average power ratio that leads to major inefficiencies. Symbol position permutation (SPP) is a distortion-less technique that achieves substantial PAPR reduction without BER degradation. However, the existing works focus on PAPR reduction using SPP for the radio frequency (RF) OFDM and the use of this technique in optical OFDM is not properly investigated. Therefore, in this paper, we present a new PAPR reduction technique based on lexicographical permutations called lexicographical symbol position permutation (LSPP) for PAPR reduction in direct current optical OFDM (DCO-OFDM). The proposed scheme is less complex than the conventional selective mapping (CSLM) scheme since there is no multiplication of the phase sequences with the DCO OFDM symbol to generate the candidate signals. We further introduce a new way of reducing the complexity by introducing a threshold PAPR and demonstrate that the complexity in terms of inverse fast Fourier transform (IFFT) operations can be reduced substantially depending on the selected threshold and the number of candidate signals.

Precoded SLM and PTS Scheme for Reduced PAPR in OFDM for Wireless Communications

Orthogonal Frequency Division Multiplexing (OFDM) contribute high data rates in current as well as future wireless communication systems but it aches from high Peak to Average Power Ratio (PAPR). But this high PAPR makes the High-Power Amplifier (HPA) complex which increases the cost of it and leads to the drawbacks like Inter Carrier Interference (ICI) and rise in out of band radiation. Even though many techniques are there to decrease the complexity of HPA by reducing the PAPR, Selected Mapping (SLM) and the Partial Transmit Sequence (PTS) provides less PAPR with low complexity. In this paper, both PTS and SLM are combined with Discrete Sine Transform (DST) and their PAPR and efficiencies are also compared with OFDM signal. The proposed hybrid DST-PTS and DST-SLM provides less PAPR compared to OFDM, SLM and PTS techniques with low complexity. Also, the bit error rate for DST-SLM and DST-PTS techniques are compared for different values of SNR. In future wireless communication systems, these proposed techniques can be used as they provide less bit error rate and less PAPR with low complexity

Joint security enhancement and PAPR mitigation for OFDM-NOMA VLC systems

Security is of crucial importance to visible light communication (VLC) systems. In this paper, we propose and experimentally demonstrate a secure non-orthogonal multiple access (NOMA) VLC system with orthogonal frequency division multiplexing (OFDM) modulation, where the peak-to-average power ratio (PAPR) is also significantly reduced. Based on 2D chaotic map, the public key serves a two-fold purpose: to provide physical-layer security against eavesdropper, and to generate a set of phase-rotated candidate signals in the chaotic selected mapping (SLM) scheme where the signal with lowest PAPR is selected for transmission. The private keys further enhance the security and guarantee the privacy among the legitimate users via chaotic data scrambling. The experiment based on a direct current-biased optical OFDM (DCO-OFDM) VLC system with two legitimate users and one eavesdropper successfully verified the joint security enhancement and PAPR mitigation performance of the proposed scheme for NOMA VLC application.

PAPR-Degraded Secure OFDM-WDM-PON Based on Chaotic Set-Partitioned SLM

This letter proposes and experimentally demonstrates an orthogonal frequency division multiplexing wavelength division multiplexing passive optical network (OFDM-WDM-PON) system based on novel chaotic set-partitioned selective mapping (SP-SLM) scheme. With the implementation of a three-dimensional chaotic system, peak-to-average power ratio (PAPR) reduction and chaotic encryption are simultaneously realized on the process of OFDM signal modulation, so as to enhance the system performance in the presence of PAPR, bit error rate (BER), fiber nonlinear tolerance and security. The experimental results show that, when compared with original OFDM signal, the OFDM signal with SP-SLM can achieve 4 dB PAPR reduction at the complementary cumulative distribution function value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-4}$ </tex-math></inline-formula> , as well as a 1.1 dB gain in receiver sensitivity at a BER of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-3}$ </tex-math></inline-formula> . For fiber nonlinear tolerance, the optimal launch fiber power of OFDM signal with SP-SLM is 10 dBm, which is better than 9 dBm of original OFDM signal under the same received optical power of −16 dBm. Furthermore, the key space of the proposed scheme can reach up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{98}$ </tex-math></inline-formula> , which is large enough to effectively protect against illegal attackers.

Optimal design of a hybrid thermal- and membrane-based desalination unit based on renewable geothermal energy

• A renewable-based hybrid desalination system consisting of HDH and RO is evaluated. • Two different operating modes of the introduced system are investigated. • Exergoeconomics is used to identify the optimal working condition of the system. • Maximum exergy efficiency of the plant is 28.86% for the second operating mode. • The first operating mode can provide freshwater at a maximum rate of 22070 m 3 /day. In this article, exergoeconomic analysis of a hybrid desalination system driven by renewable geothermal energy source is investigated. Freshwater and electrical power are the products of this system. Humidification – dehumidification (HDH) unit works in parallel with reverse osmosis (RO) unit to produce freshwater and Kalina cycle is the power generator unit. Thermoelectric generator (TEG) is responsible for providing the energy required by RO unit. As both HDH and TEG can operate with low-grade energy, two different modes are suggested for the proposed system. In the first mode, the geothermal low grade energy stream is passed to TEG unit, while in the second, it goes through the HDH unit. The effect of different parameters on four main objective functions is examined in parametric study. Moreover, with the aid of selection maps, the objectives of modes can be compared in different operating conditions. The maximum attainable exergy efficiency is calculated to be 28.86% for mode 2. Single objective optimization studies revealed that the first mode produces the largest amount of freshwater at a rate of 22,072 (m 3 /day), while the minimum achievable freshwater cost and total product cost rate can be obtained in the second mode, which is calculated to be 21.94 (¢/m3) and 37.19 ($/GJ). Besides, Sankey diagrams for exergy flow and mass flow of saline water are presented to unravel the impact of each sub-system on exergy and salinity.

Modified selective mapping based on squaring construction

SummaryThis study proposed a novel technology, squaring construction with selective mapping (SC‐SLM), aimed at reducing the peak‐to‐average power ratio (PAPR); the technology integrates squaring construction codes and selective mapping (SLM). SLM is a frequently adopted technology for reducing the PAPR of signals, and much SLM research has focused on designing a systematic structure for SLM's phase generation mechanisms. SLM involves a high overall system complexity because its phase generation mechanism does not incorporate a systematic structural design. Squaring construction codes were employed in this study to establish a phase generation mechanism with a systematic structure for SLM; additionally, the generator matrix of the squaring construction codes was used to encode the transmitted data to enable transmitted signals to correct errors. Using squaring construction is conducive to the design of codes with varying code lengths to correct errors and protect the transmission system. To ensure that SC‐SLM performs comparably with conventional SLM in terms of PAPR reduction, we established (1) two‐phase generation mechanisms in SC‐SLM and (2) a selection rule to determine the more suitable mechanism for generating scrambling phases under different circumstances. According to the simulation results, the performance of SC‐SLM in PAPR reduction was comparable with that of the conventional SLM, had systematically structured phase generation mechanisms, and was capable of error correction.

PAPR Reduction an effective approach for next frontier MIMO-OFDM systems

The ‘Orthogonal frequency division multiplexing (OFDM)’ is a well-accepted and effective technology employed today and in future wireless communication systems. The combinations of OFDM and ‘multiple-input multiple-output (MIMO’) offer high quality of services and better throughput. The multicarrier OFDM system experiences a high ‘peak-to-average power ratio (PAPR’), which is the major issue in the OFDM scheme and must be truncated to achieve trustworthy communication. Due to high PAPR in a signal to be transmitted, the power amplifier in the transmitter section enters into saturation region and amplifies the signal nonlinearly, resulting in loss of orthogonality and ultimately in ‘inter-carrier interference (ICI)’. In this article, the 'iterative clipping and filtering (ICF)' method is proposed to minimize the PAPR in the OFDM system. The simulation is carried out using MATLAB (version 2014b). The result of the proposed ICF method and the ‘selective mapping (SLM)’ scheme is analyzed and compared. From the analysis, it is shown that the proposed ICF technique is more suitable for minimizing the PAPR effectively without affecting ‘bit error rates (BER)’ much and the simplicity of the system. The simulation result of the proposed ICF scheme using ‘Quadrature Phase Shift Keying (QPSK)’, FFT size of 128, and clipping and filtering level up to 6 shows that the proposed ICF scheme for clipping level of 6 reduces PAPR to 5dB. Also, the BER is minimized at the level of 3×10−5 at 12 dB SNR.