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Power Optimization for Energy Efficiency in Cell-Free Massive MIMO with ZF Receiver

期刊: 2019 21ST INTERNATIONAL CONFERENCE ON ADVANCED COMMUNICATION TECHNOLOGY (ICACT): ICT FOR 4TH INDUSTRIAL REVOLUTION, 2019; ()

In this paper, a pilot-contaminated uplink cell-free massive multiple-input multiple-output (mMIMO) system with zero-forcing (ZF) receiver is considered. Then this paper derives a novel lower-bound expression for uplink energy efficiency (EE), which enables us to propose a resource optimization problem to maximize the total EE. This considered power optimization scheme takes into account the quality-of-service (QoS) requirement, each user power constraint and power consumption. Specifically, the power consumption model includes circuit power, data transmission power and backhaul power. Since the proposed power control problem is non-convex, a novel path-following approximation algorithm is characterized to tackle this problem. Simulation results indicate that the proposed algorithm only needs a few iterations to converge. Moreover, compared with equal power control (EPC) scheme, our algorithm can significantly improve the total EE.

Vehicle Aerodynamic Optimization: On a Combination of Adjoint Method and Efficient Global Optimization Algorithm

期刊: SAE INTERNATIONAL JOURNAL OF PASSENGER CARS-MECHANICAL SYSTEMS, 2019; 12 (2)

This article presents a workflow for aerodynamic optimization of vehicles that for the first time combines the adjoint method and the efficient global optimization (EGO) algorithm in order to take advantage of both the gradient-based and gradient-free methods for aerodynamic optimization problems. In the workflow, the adjoint method is first applied to locate the sensitive surface regions of the baseline vehicle with respect to the objective functions and define a proper design space with reasonable design variables. Then the EGO algorithm is applied to search for the optimal site in the design space based on the expected improvement (EI) function. Such workflow has been applied to minimize the aerodynamic drag for a mass-produced electric vehicle. With the help of STAR-CCM+ and its adjoint solver, sensitive surface regions with respect to the aerodynamic drag are first located on the vehicle. Then the design samples are determined with the help of the uniform design (UD) method and trained by the EGO algorithm (written by MATLAB) for searching the optimum. The optimization results are analyzed to validate the workflow and provide more insights into the improvement of the flow field.

Real-time assessment and prediction on maritime risk state on the Arctic Route

期刊: MARITIME POLICY & MANAGEMENT, 0; ()

Recently, the Arctic Route has become busier with the continuous melting of Arctic ice. However, navigation on the Arctic Route would be much more complex than in normal water as harsh environmental conditions, such as ice-covered water and scarce costal ports that may cause more uncertainty. Nowadays, with the rapid development of sensors on board, more related data has become available. Thus, implementing comprehensive Arctic maritime risk assessment is urgent and necessary in practice. This study proposes an Arctic maritime risk state assessment method including real-time risk state assessment and risk prediction. Specifically, real-time observation samples' numerical risk state would be firstly obtained with projection pursuit method from 10 risk indicators. Due to the fuzzy uncertainty of single observation set, information diffusion would be applied to provide diffusion estimation on risk probability distribution in order to depict risk state precisely. Also, the accumulated distribution can be regarded as the risk prediction for next time slot and risk entropy is introduced to depict risk tendency directly. Case study based on 'Yongsheng' is conducted to demonstrate and verify the effectiveness of the proposed method. The findings can be useful for the operators and management on board during the Arctic voyage.

Application of 17 Classification Algorithms for Authentication Research of Various Boletus

期刊: SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019; 39 (2)

Many wild nocuous fungi are similar to the edible in morphology and biological characteristic, which easily leads to serious food safety incident because it is difficult for farmers to distinguish them just by experience. The progress of wild edible production makes a great contribution to rural economy of Yunnan province where the yield and export volume are highest in China. Rapid authentication of wild edible fungi variety is beneficial for wild edible industry towards healthy development. Meanwhile, the authentication also contributes to the analysis of the genetic relationship between edible mushroom and their breeding. Seven kinds of fungi were collected from Yunnan and other seven origins around Yunnan. Fingerprint of caps and stipe were obtained with Fourier transforms infrared (FTIR) spectrometer, respectively. Cap model, stipe model, low-level data fusion model and mid-level data fusion were established using prepressed spectra according to low- and mid-level fusion strategy combined with decision trees, discriminant analysis, logistic regression classifiers, support vector machines, nearest neighbor classifiers and ensemble classifiers that every model was computed 10 times. The optimal classification algorithm was selected based on the accuracy of training set. Hierarchical cluster analysis (HCA) was executed using the mid-level fusion dataset to judge genetic relationship between seven fungi. The results indicated; (1) The best algorithm of caps, stipe and low-level fusion is linear discrimination that accuracy is 92. 8% , 96. 4%, and 97. 6%, respectively. Subspace discriminant is the most optimal in mid-level fusion that accuracy is 100%. (2) The average accuracy of all samples is 93. 61%, 95. 54%, 96. 99% and 99. 88% based on the best model of stipe, cap, low-level data fusion and mid-level data fusion. The performance of mid-level fusion is better than other three models, which indicated that the model could distinguish the highly -similar samples by reducing the influence caused by their origins. (3) The result of HCA based on mid-level fusion dataset displayed that the distance between Boletus magnificus and B. edulis was very close, which showed their chemical information were similar and genetic relationship was close. (4) The result of HCA based on mid-level fusion dataset displayed that the distance between Boletus magni ficus and Leccinum duriusculum was very long, which showed their chemical information were different and genetic relationship was inferior. In a word, mid-level data fusion strategy combining FTIR spectra of different parts, subspace discriminant and HCA could effectively distinguish different kinds of edible fungi and judge the genetic relationship, which is a novel method used for variety authentication and genetic relationship judgment of wild edible fungi.

IF:0.43

An Absorbance-Based Prediction Method of Spot Color Formula for PET Film

期刊: SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019; 39 (2)

A model for predicting spot color ink formula for PET film printing is proposed based on the correlation between absorbance and the concentrations of primary inks. Firstly, according to the methodology with the concept of light propagation and the multiple internal reflectance of ink layer and substrate, a method for obtaining the spectral transmittance of the thin film prints with high transmission characteristic is established by making use of the reflectance of the film prints with back and white substrates. The absorption spectrum of the film prints in the visible spectrum is obtainedby the spectral transmittance. Then, the regression equation between the absorbance of spot color inks and the concentrations of a primary color ink is established to determine characteristic wavelengths with strong linear correlation. After that, according to Lambert-Beer law, the prediction model is established by using the absorbance of the spot color samples and the absorbance of the primary color samples at the characteristic wavelengths, in order to obtain the proportions of primary color inks. Finally, the deviation between the predicted formulas and the actual concentrations is analyzed. In order to evaluate the accuracy of the prediction method, the remade samples are compared with target samples in terms of chromatic difference and the spectralroot mean square error. Some dual-componentspot color samples produced on PET filmby gravureare used as experimental subjects to verify the proposed method. The analysis of spectrum shows that the reflectance on the black substrate is significantly different from the reflectance on the black substrate, but both have the same trend with the variation of primary ink concentration. The transmittance curves of spot color-samples are situated between the curves of primary color samples and movecloser to the primary color with higher concentration. The absorption spectrum of samples increase in the regionof 400 similar to 580 nm with the decrease of concentration of primary ink A, and decrease in the region of 580 similar to 700 nm as the concentration of A decreases. Except for the region of 570 similar to 590 nm, the linear correlation coefficients R-2 between absorbance of spot color inks and the concentration of primary color A are higher than 0. 95 and the average value is 0. 990 0, which means a strong linear correlation in the visible spectrum range. The absorbancevalues at the wavelength 520 nm (R-2 of 0. 994 2) and 700 nm (R-2 of 0. 998 5) of the primaryinks A and B are selected to predict the formulas of spot colors by using the least squares method. The results show that the 6 groups of predicted concentrations are with 2. 5% deviation from the actual concentrations of target samples, which means no significant difference. The maximum chromatic difference between the targetsamples and remade samples is estimated to be 1. 98, the minimum to be 0. 30, and the average value to be 0. 85, which satisfies the requirement of spot color reproduction. 5 of the 6 groups are smaller than 1. 5, which satisfies the requirement of faithful reproduction. The maximum RMSE is 2. 95% , and the minimum is 0. 49% , and the average value is 1. 40% , which means a high precision color reproduction in the visible spectrum. It is confirmed that the proposed method could effectively improve the printing quality and the spot color matching precision, which may provide a scientific method for the predictive study of spot color ink formula of PET film printing.

IF:0.43

Human Gastric Tubular Adenocarcinoma Tissue Detection Based on Terahertz Time Domain Spectroscopy and Tissue Microarray Technology

期刊: SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019; 39 (2)

Terahertz wave technique is very prospective in the biomedical application field, where there exists a practical problem that it is hard to register a terahertz time-domain spectroscopy (THz-TDS) detection point and its accurate corresponding position in pathology image. In this paper, complex human gastric tissue is taken as the experimental subject to search for accurate detection approach. This paper uses tissue microarray technology to process paraffin-embedded gastric tissue, and then contrasts the Terahertz absorption coefficient and refractive index spectrum of detection subjects which are divided into registered experimental group and unregistered control group using principal component analysis method. Meanwhile, this paper contrasts the gastric tubular adenocarcinoma THz-TDS discrimination methods using support vector machine and logistic regression respectively. The research result reveals that the detection accuracy brought by tissue microarray technology helps better discriminate tumor samples and normal samples.

IF:0.43

The Relationships between Uranium Polluted Leaf Reflectance Spectral Characteristics of Phytolacca acinosa Roxb. and Uranium Contents

期刊: SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019; 39 (4)

A pot cultivation experiment was carried out to investigate the relationship between uranium contents in leaves of Phytolacca acinosa Roxb. and original spectral datum and first derivative spectral datum with derivative technique, and to seek out the sensitive wavelengths and spectral characteristics of Phytolacca acinosa Roxb. under uranium pollution. Then by choosing sensitive bands and the best correlated spectrum characteristic parameters, uranium estimation models were constructed. The results showed that when the U contents in leaves were 5. 94 similar to 71. 74 mg . kg(-1), they correlated closely with the first derivative reflectance in the range of 749 similar to 766 nm. The chosen 14 spectral characteristic parameters were used to calculate the correlation coefficients with uranium contents in leaves, and correlations of the blue edge area, the red edge position, the ratio of red edge area to blue edge area and the normalized values of red edge area and blue edge area were significantat the 0. 05 level. The selected wavelengths of 757, 758, 760, 761 nm and the above-mentioned 4 best spectral characteristic parameters were used to establish the uranium estimation models,- and precision tests proved that the uranium estimation models established bythe ratio of red edge area to blue edge area, first derivative reflectanceat 757 and 760 nm achieved better test results, among them, the best model was the cubic function model using first derivative reflectance at 757 nm as a variable and the prediction accuracy of it was up to 89. 8%.

IF:0.43

Study on the Polyhydric Alcohol Liquefaction of Corn Stalk under Atmospheric Pressure and Analysis of Liquefied Products

期刊: SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019; 39 (5)

It is a significant technique for choosing proper solvents during liquefaction of biomass process to produce fuel additives and valuable chemicals. In this study, the mixtures of new low-cost diethylene glycol (DEG) with 1, 2-Propanediol (PG) and the traditional ethylene glycol (EG) with PG (6 : 1 omega/omega) were adopted as liquefying agents. And analyses were conducted to throw light on the effects of these two different liquefying agents on the liquefaction yield and the properties of the biomass liquefaction oil products. The properties of the corn stalk, bio-oil and residue were studied with gas chromatography and mass spectrometry (GC-MS), Fourier transform infrared spectroscopy ( FTIR) , pyrolysis-gas chromatrography/mass spectrometry (PyGC/MS) and X-rays diffraction (XRD). The results indicated that when the DEG and PG were cooperatively used as liquefying agent, the liquefaction yield was 98. 57%. And there was a liquefaction yield of 96. 08%, with the mixture of EG and PG as liquefying agent. GC-MS analysis results showed that the main components of bio oils were alcohols and organic acids, with a total content of more than 97%. However, the bio oil obtained by EG mixed PG liquefaction contained nearly 60% of organic acids, which was the main cause of the acidity and corrosiveness of the bio oil, and was not conducive to the liquefaction. The characteristic absorption peaks of the corresponding functional groups of some oligomers in the bio oil were detected by FTIR to compensate for the limitation of the GC-MS characterization. It turned out that many active chemical bonds were generated in the liquefaction system, leading to improving the activity of the reaction system, and the bio oil contained a large number of C-O and C=O functional groups, which strongly supported the results of the conclusions of GC-MS. Furthermore, Py-GC/MS, FTIR and XRD were applied for the characterization of the liquefaction residues. Py-GC/MS explained that the liquefaction residue composition produced in this way was complicated and contained a certain amount of large molecular substances which were very difficult to degrade. The liquefaction residues were mainly originated from the polycondensates or derivatives of interactions between small molecules of lignin or hemicellulose degradation or unreacted cellulose, and the macromolecular substances generated by the reaction of the degradation products of three components and liquefying agents. The signals of FTIR reported that the functional groups of cellulose, hemicellulose and lignin were disappeared and the liquefaction degree of lignin was the largest. Results from XRD presented that because of the destruction of crystalline structure of carbohydrates, the cellulose molecules was cracked, indicating that the cellulose was degraded and the degree of liquefaction was high. Consequently, all the results successfully confirmed that the liquefaction effect of DEG mixed PG was better than the mixture of EG and PG. Even it provided an efficient and environmental process for generating bio-oil from lignocellulosic mass at a low cost in liquefaction of corn stalk.

IF:0.43

Effect of Dy3+ on Luminescence Properties of Tb3+ Activated Silicate Oxyfluoride Scintillating Glass

期刊: SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019; 39 (5)

Dy3+, Tb3+ doped and Dy3+/Tb3+ co-doped silicate oxyfluoride scintillating glass were prepared by high temperature melting method. The Fourier transform infrared spectra, transmission spectra, photoluminescence excitation and emission spectra, X-ray excited luminescence spectra and luminescence decay curves were analyzed. The influence of the energy transfer between Dy3+ and Tb3+ ions and Dy3+ doping onluminescence properties of Tb3+ activated silicate oxyfluoride scintillating glass was studied. The results indicated that Dy3+/Tb3+ co-doped silicate oxyfluoride scintillating glass has relatively high density and good transmittance in visible region. The networkstructure of glass isconstituted of tetrahedral [SiO4] and [AlO4]. Under the irradiation of ultraviolet light, the luminescence of Dy3+-doped glass originates from F-4(9/2) -> H- 6(15/2) (483 nm) and H-6(13/2) ( 576 nm) transition emission of Dy3+ ions, while the luminescence of Tb3+-doped glass originates from D-5(4) -> F-7(6) (489 nm), F-7(5) (544 nm), F-7(4) (586 nm) and F-7(6) (623 nm) transition emission of Tb3+ ions. As for Dy3+/Tb3+ co-doped silicate oxyfluoride scintillating glasses, the emission spectra aremainly due to fluorescence emission of Tb3+ ions. The emission spectra under ultraviolet excitation with different wavelengths revealed that Dy3+/Tb3+ co-doped scintillating glass includes manifold energy transfers. When Tb3+-doped glass is excited by the characteristic excitation wavelength (452 nm) of Dy3+ ions, the luminous intensity of Tb3+-doped glass is very weak. With the introduction of Dy3+ ions, Tb3+ ions emission are sensitized and enhanced by the energy transfer of F-4(9/2) (Dy3+) -> D-5(4) (Tb3+). The luminous intensity of Dy3+/Tb3+ co-doped glassesis improved with the increase of Dy2O3. The luminous intensity of Dy3+/Tb3+ co-doped glasses reaches the maximum when the content of Dy2O3 is 1mol%. However, when the content of Dy2O3 is further increased, the concentration of Dy3+ ions is quenched, which results in the decrease of the energy transfer to Tb3+ ions and the reduction of the luminous intensity. When the excitation wavelength is decreased to 350 nm, Dy3+ and Tb3+ ions are excited to higher energy levels of P-6(7/2)(Dy3+) and L-5(9) (Tb3+). At this point, the energy transfer of both F-4(9/2) (Dy3+) -> D-5(4) (Tb3+) and D-5(4) (Tb3+) -> F-4(9/2) (Dy3+) occurs. When the doping concentration of Dy3+ ions is relatively low, the energy transfer of Dy3+.Tb3+ is stronger than that of Tb3+ -> Dy3+, which enhancesthe luminescence of Tb3+ ions by sensitization. With the increase of Dy2O3 content, the energy transfer of Tb3+ -> Dy3+ is enhanced. When the content of Dy2O3 is above 0. 4 mol%, the energy transfer of Tb3+ -> Dy3+ is strongerthan that of Dy3+ -> Tb3+, which reduces the transition luminescence of Tb3+ ions and thus decreases theluminous intensity of Dy3+/Tb3+ co-doped glass. Due to the efficient energy transfer from Gd3+ to Dy3+ or Tb3+, the competition of energy transferfrom Gd3+ to Dy3+ and Tb3+ ion soccurs under characteristic excitation wavelength of Gd3+ ion at 274 nm. With the increase of content of Dy2O3, the captured energy of Tb3+ ions decreases constantly. At the same time, the energy backtransfer of Tb3+ -> Dy3+ and the nonradiative cross relaxation between Dy3+ ions appear, which leads to the reduction of theluminous intensity of Dy3+/Tb3+ co-doped glass. The D-5(4) -> F-7(5) luminescence decay curves of Tb3+ ions for Dy3+/Tb3+ co-doped scintillating glass showed that with the increase of Dy2O3 content, the lifetime of D-5(4) (Tb3+) reduces from 2. 24 to 1. 15 ms and the curve changes from single-exponential to double-exponential form, indicating the possibility of the energy back transfer of D-5(4) (Tb3+) -> F-4(9/2) (Dy3+) in the glass. The X-ray excited luminescence emission spectra showed that the introduction of Dy3+ ions has a negative effect on the luminescence of Tb3+ activated scintillating glass. Because that negative effect is not enough to make up for the Dy3+ -> Tb3+ energy transfer, the radiation luminescence intensity of Dy3+ /Tb3+ co-doped glass decreases with the increase of the Dy2O3 content. Therefore, Dy3+ ions should not be used as sensitizers to enhance the luminescence intensity of Tb3+ ions in Tb3+ activated silicate oxyfluoride scintillating glass.

IF:0.43

Determination of Water Content in Watered Anhydrous Coolant Liquid and Brake Fluid of Automobile Using Fourier Transform Near-Infrared Spectroscopy

期刊: SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019; 39 (7)

Coolant liquid and brake fluid are important vehicle oils, and they are of great significance for the normal operation of vehicles. Adding water into the coolant liquid and brake fluid is the common adulteration method for coolant liquid and brake fluid. The active ingredients in adulterated coolant liquid and brake fluid will reduce, and function of coolant liquid and brake fluid will be influenced. This will result in the harm of vehicles, which will influence the normal operation of vehicles. Rapid and accurate detection of water content in coolant liquid and brake fluid is of importance for quality assurance. In this paper, Fourier transform near-infrared spectroscopy was used to determine water content in different brands of watered anhydrous coolant liquid and brake fluid. Three brands of anhydrous coolant liquid, and four brands of brake fluid were used. In addition, samples with water contents of 0%, 5% , 10%, 15%, 20% , 25%, 30% and 35% were prepared. Fourier transform near-infrared transmittance spectra of the samples were acquired, and the spectral range of 10 067 similar to 5 442 cm(-1) were used for analysis. There were differences on near-infrared transmittance spectra among samples with different water contents. Based on each brand of anhydrous coolant liquid and brake fluid, principal component analysis (PCA) indicated the obvious differences among samples with different water contents. Besides, second derivative spectra were used to select optimal wavenumbers for each brand of anhydrous coolant liquid and brake fluid, as well as the combination of all brands. The selected optimal wavenumbers were similar among different brands of anhydrous coolant liquid as well as the combination of brands, and the selected optimal wavenumbers were similar among different brands of brake fluid as well as the combination of brands. The number of wavenumbers reduced at least 98. 67% after selection. Based on the full spectra and the selected optimal wavenumbers, partial least squares (PLS) and least-squares support vector machine (LS-SVM) were built. All the models obtained quite good performances, with determination of coefficient (R-2) over 0. 9 and residual prediction deviation (RPD) over 3. These prediction models obtained good performances. The performances of models for single brands were similar to those for the combination of brands, indicating that it was feasible to build calibration models using the combination of brands which would benefit the practical application. The overall results indicated the feasibility of using Fourier transform near-infrared transmittance spectroscopy combined with chemometric methods could be used to determine water adulteration in different brands of anhydrous coolant liquid and brake fluid. The results would help to develop on-line detection systems for water adulteration in different brands of anhydrous coolant liquid and brake fluid, and would provide guidance for detecting water content other fluids for automobile.

IF:0.43

Rapid determination of trace nitrofurantoin in cosmetics by surface enhanced Raman spectroscopy using nanoarrayed hydroxyl polystyrene-based substrate

期刊: JOURNAL OF RAMAN SPECTROSCOPY, 2019; 50 (8)

The safety of cosmetics attributing to the illegal addition of antibiotics for quick effect is a big concern nowadays. Nitrofurans, one of commonly added illegal antibiotics, are strictly banned in cosmetics in China. It is still a great challenge for the rapid and precise analysis of trace nitrofurans when facing various cosmetics with complicated matrices. Surface-enhanced Raman spectroscopy (SERS) is emerging as a novel rapid on-site analytical technique. In this work, an accurate SERS method was developed for the rapid analysis of trace nitrofurantoin in various cosmetics by use of nanoarrayed hydroxyl polystyrene (PS-OH)-based substrate. A series of characterizations indicated the successful synthesis of Au@PS-OH substrate and the uniform distribution of gold nanoparticles on the substrate surface. The SERS substrate revealed good selectivity and reproducibility with an enhancement factor of 2.6x10(4). Finally, an analytical method for the determination of nitrofurantoin in cosmetics was established by SERS using Au@PS-OH substrate coupling with efficient sample preparation process. It was satisfied that trace nitrofurantoin could be actually detected and quantified to be 1.77 and 7.74 mg/L in a mouthwash and rose-mist sample, respectively, with good recoveries of 86.8-106% and relative standard deviations of 0.9-2.9%. The comparable analytical results for real samples were achieved by the traditional high-performance liquid chromatography (HPLC) method, which validated the reliability of the proposed method. It is expected that this SERS method has great potential for the rapid and on-site analysis of trace additives in cosmetics.

IF:2.81

Research Progress in Spectroscopic Diagnosis of Plasma Jet Characteristics Under PS-PVD

期刊: CHINA SURFACE ENGINEERING, 2019; 32 (5)

Plasma spray-physical vapor deposition (PS-PVD), as a new spray technology, combines the advantages of both vapor deposition and thermal spray processes. The plasma characteristics determine the micro structure and properties of the coatings. As a plasma jet characteristic diagnosis technology, optical emission spectroscopy (OES) can realize the in-situ detection of jet characteristics, which is a powerful means to judge the evaporation phenomenon in the jet. This paper introduced the changes of jet characteristics before and after the powder was inject and after the jet impacted the substrate. It shows the calculation of the state of each particle in the jet under the assumption of local thermodynamic equilibrium (LTE) and the theory of broadening, and explores the activities of mass and heat transfer in different regions of the jet. Ar/He has the highest temperature, and Ar has a high enthalpy value, which plays a major role in evaporating the powder. The He condensed jet energy plays a key role in the heating and evaporation of the powder. H2 expands the jet width and reduces the jet temperature to form a mixed layer with dense and columnar structure. Combined with simulation calcnlation and spectroscopy of the jet, it is known that the complex thermal interaction in the spray gun is the main reason for powder heating. The thermal energy and kinetic energy are alternately converted in the expansion/compression zone at the nozzle, and the middle and rear sections of the jet continue to vaporize due to low pressure and high temperature. After reaching the peak, the jet is in the stage of condensation and cooling, and some of the vapor phase atoms are agglomerated into cluster-like particles. The effects of power, current and powder feeding rate on plasma jet characteristics are also summarized.

Facile design of a domestic thermoelectric generator by tailoring the thermoelectric performance of volume-controlled expanded graphite/PVDF composites

期刊: COMPOSITES PART B-ENGINEERING, 2019; 176 ()

Polymer-based thermoelectric materials have attracted considerable interest for green energy conversion over the past decades. In this study, polymer/inorganic thermoelectric generators were prepared by integrating film-forming polyvinylidene fluoride (PVDF) and expanded graphites (EGs) to tailor the thermoelectric performance of the resulting PVDF/EG composites by adjusting the expansion volume of EGs with different thermal treatments. The charge carrier rate and phonon scattering are responsible for the divergent performance of the prepared polymer/EG composites. The prepared composites exhibited superior thermoelectric properties, where the PVDF/EG composite containing 20% EG expanded at 600 degrees C showed an electrical conductivity of 883 S/cm, a Seebeck coefficient of 8.77 mu V/K, and a high power factor of 6.79 mu W m(-1)K(-2). This composite outperforms many other graphene- or graphite-based composites reported in the literature. This study provides a facile avenue to prepare an inexpensive, lightweight, nontoxic, and highly efficient thermoelectric generator for green energy conversion and energy harvesting.

IF:6.86

Fabrication of mullite fiber porous ceramics with even structures by filtration freeze-drying

期刊: JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 2019; 127 (1)

In this study, mullite fibrous porous ceramics (MFPCs) were fabricated by freeze-drying wetted bodies formed using vacuum filtration. The effects of freezing temperatures on the microstructure and mechanical properties were investigated. The investigations revealed that freeze-drying could effectively stop silica sol migration and obtain a uniform porous ceramic microstructure in which the binder covered the fiber surfaces and bonded the fibers at nodes. Owing to the homogeneous microstructure, the compressive strength of the obtained MFPCs with open porosity of 85.4% was more than 2.0 MPa, and there were two elastic regimes and one plastic regime in the stress-strain curve of the MFPCs, moreover, which revealed that the MFPCs fractured step by step under compression. In addition, the freezing temperatures affected the properties of the MFPCs because of the formation of plates derived from the binder. (C) 2019 The Ceramic Society of Japan. All rights reserved.

IF:1.11

Dynamic Fracture Analysis of Functional Gradient Material Coating Based on the Peridynamic Method

期刊: COATINGS, 2019; 9 (1)

Functional gradient materials (FGMs) have tremendous potential due to their characteristic advantage of asymptotic continuous variation of their properties. When an FGM is used as a coating material, damage and failure of the interface with the substrate component can be effectively inhibited. In order to study the dynamic crack propagation in FGM coatings, a new method, peridynamics (PD), was used in the present study to simulate dynamic fractures of FGM coatings bonded to a homogeneous substrate under dynamic loading. The bond-based PD theory was employed to study crack propagation and branching in the FGM coating. The influences of the coating gradient pattern, loading, and the geometry and size of the structure on crack curving and propagation under impact loading were investigated. The numerical results show that different forms of the elastic modulus of graded material, the geometry of the structure, and the loading conditions have considerate effects on crack propagation in FGM coatings, but a specific form of elastic modulus had a limited effect on the dynamic fracture of FGM coating.

IF:2.33

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