Matrix Solution Research Articles

Fracture behavior of a rapidly solidified thin-strip continuous cast AA5182 Al-Mg alloy with the Portevin-Le Chatelier effect under varying strain rates

This study investigates the strain-rate triggered PLC effect and fracture behavior of a rapidly solidified thin strip (TS) cast AA5182 alloy in comparison with those of direct chill (DC) counterparts. Higher cooling rates obtained via TS casting suppress the formation of phases in Al-Mg alloys and significantly enhance the matrix solute supersaturation beyond the equilibrium level, thereby impacting the interaction dynamics of mobile dislocations and solute atoms. This in turn affects the evolution of typical stress fluctuations in Al-Mg alloys, referred to as the Portevin-Le Chatelier (PLC) effect, occurring in specific strain rate-temperature domains, i.e., with type and characteristics dependent upon the microstructure. Tensile testing demonstrated a strain-rate dependent PLC effect, also aligning with the ductility trend in both negative and positive strain-rate sensitivity domains. The characteristics of PLC bands, as well as the magnitude of stress fluctuations, were shown to evolve with strain rate, facilitating distinct fracture mechanisms. In particular, the TS sample exhibited a higher strain rate sensitivity of the fracture mechanisms and PLC band characteristics and, thus, a narrower range of deformation rates for optimum ductility (attributed to increased solute in the matrix). Controlling the deformation rate to favor predominantly Type-B serrations and ensuring their stability with minimal fluctuations was shown to postpone necking and prevent material failure. The significance of rate sensitivity in alloys with reduced microsegregation is emphasized, suggesting the need for further exploration of mechanical properties.

General strong fuzzy solutions of complex fuzzy matrix equations involving the Moore-Penrose weak group inverse

In this paper, we investigate the fuzzy solutions of the complex fuzzy matrix equation (CFME) CZ˜=W˜, in which C is a complex crisp matrix, and W˜ is a complex fuzzy matrix. The purpose of this paper is three-fold. Firstly, the necessary and sufficient conditions for the existence of strong fuzzy solutions to the CFME are obtained using the MPWG inverse of the coefficient matrix. Secondly, we obtain a necessary and sufficient condition for the existence of S†,WG≥0 (S†,WG is called the Moore-Penrose weak group inverse of the coefficient matrix S) in order to obtain a strong fuzzy matrix solution of CFME. Moreover, general strong fuzzy solutions of the CFME are derived and an algorithm for obtaining general strong fuzzy solutions of CFME by the MPWG inverse is also established. Finally, some numerical examples are given to illustrate the main results.

Enhancing the performance of lightweight high-performance concrete through an alternative pre-wetting method for lightweight aggregates using simulated cement pore solution

Lightweight aggregates (LWAs) are typically pre-wetted to prepare lightweight concrete. However, the incorporation of pre-wetted LWAs by water, may dilute the pore solutions of the cement matrix surrounding the LWAs during the process of internal curing. To this end, this paper proposes an alternative pre-wetting method for LWAs using simulated cement pore solutions (saturated Ca(OH)2 or real cement solution) instead of water. The effects of LWAs pre-wetted by various agents on the performance of lightweight high-performance concrete (LW-HPC) were investigated and compared. Experimental results confirmed that water released from LWAs diluted the pore solutions of cement in LW-HPCs. By using cement solution and Ca(OH)2 solution, the compressive strengths of LW-HPCs were respectively increased by 41.7% and 28.2% at 3d, and 11.6% and 3.2% at 28d compared with LWAs pre-wetted by water only. Among the three pre-wetting agents, the saturated cement solution was found to be the optimal one for promoting the hydration of cement, elastic modulus of the interfacial transition zone, and compressive strength.

Effect of annealing time on solid solution microstructure and memory properties of additive Fe-Mn-Si-Cr-Ni alloy

Annealing plays a pivotal role in optimizing the morphology and quantity of cooling martensite within the solid solution matrix of additively manufactured Fe-based memory alloys. In this study, we utilized laser filament deposition to create Fe-17Mn-6Si-9Cr-5Ni alloy, and subsequently compared the microstructure and memory properties of the alloy following two treatments: a 900[Formula: see text]C× 60 min solution treatment and a solid solution + annealing treatment at various durations at 600[Formula: see text]C. Our aim was to investigate how annealing time impacts the memory properties of additively manufactured Fe-Mn-Si-Cr-Ni alloys in their solid solution state, focusing on microstructural changes during the metamorphic and revertive states. The findings reveal that after the solution treatment, the alloy contains a higher number of cooling martensite units, but their arrangement is disordered, indicating a lower degree of order. However, after a 10 min annealing treatment, the quantity of cooling martensite slightly diminishes, while their arrangement becomes more orderly. With prolonged annealing, both the quantity of cooling martensite and the grain size of the alloy decrease significantly. Consequently, after a 10-min annealing treatment, the alloy exhibits a 31% increase in shape recovery rate under a 6% pre-deformation compared to the alloy subjected solely to the solution treatment, and the recoverable strain reaches 4.59%. This demonstrates that an appropriately timed annealing process can transform the disordered cooling martensite within the solid solution structure of additive manufacturing Fe-based memory alloys into a more regular arrangement, thereby enhancing their memory performance.

PEREGRINATIONS ON THE STUDY OF THE OPTICAL PROPERTIES OF NONSPHERICAL PARTICLES

PEREGRINATIONS ON THE STUDY OF THE OPTICAL PROPERTIES OF NONSPHERICAL PARTICLES

The laboratory perspective: Confirming the integrity of fingermark enhancement reagents

Validation is particularly important in forensic science. Each process utilised by a forensic laboratory will undergo validation to ensure it is functioning as expected. Some pieces of equipment (hardware) will be simple to validate, and this will be conducted regularly. However, many commonly employed fingermark enhancement reagents, such as ninhydrin and 1,2-Indandione, do not have clearly defined and robust validation parameters. To that end, artificial fingermark solutions, particularly amino acid solutions, have previously been investigated as a controlled validation method, via deposition onto a substrate. Whilst amino acid reagents are important, there is also a wider group of latent fingermark constituents (targets) that require the use of other enhancement reagents within the forensic laboratory. The work presented herein seeks to expand on the concept of amino acid printing, by exploring the possibilities of depositing a sebaceous solution matrix, thereby facilitating the testing of reagents such as Oil-Red-O and Physical Developer. In addition, we present a method that extends capabilities beyond fingermark enhancement reagents for porous substrates, by developing a methodology that enables process validation of the cyanoacrylate fuming technique to be easily facilitated. These simple and effective solutions have the capacity to serve as a crucial process validation check within the laboratory validation workflow.

Mechanical and high-temperature wear resistance properties of WC-reinforced AlCoCrFeNiTi0.5 high entropy alloy matrix composite

x wt.% WC/AlCoCrFeNiTi0.5 (x = 0, 5, 8, 10, 15) high entropy matrix composites (HEAC) with different mass fractions of WC particles were prepared by mechanical alloying (MA) and spark plasma sintering (SPS). Their microstructure, mechanical properties, room-temperature (RT) and high-temperature (HT) wear resistance properties were investigated. It shows the sintered HEACs are mainly composed of a face-centered cubic (FCC) solid solution matrix, (Fe, Co)6W6C, and other carbides. The increase of WC particles leads to the fracture strength and wear resistance of AlCoCrFeNiTi0.5 being increased first and then decreased. The 8 wt% WC/AlCoCrFeNiTi0.5 HEAC shows higher strength and better wear resistance properties due to the formation of carbides and protection of the dense oxide film on the worn surface. The high-temperature wear mechanism is mainly adhesive wear, and oxidative wear in the case with lower WC content, but it becomes adhesive wear, abrasive wear, and oxidative wear in the case with higher WC content. This work provides light for investigating tribological properties of high-entropy matrix composites for surface engineering.

Microwave joining of SS-430 with a nano SS-316L powder

In this study, a hybrid microwave heating (MH) approach was employed to fabricate SS-430 to SS-430 joints using a nano-based SS-316L powder as a binding agent. The microstructural aspects of the developed fusion zone (FZ) revealed the perfect diffusion bonding between the faying surfaces through the fully melting of the filler material. The formation of martensite was observed at the diffused zone/heat-affected zone along both interfacing surfaces of the SS-430 base metals to be butt welded. The phase analysis of the developed reaction layer in the FZ showed the presence of small amounts of carbide particles (mainly chromium carbides) along with the presence of the main Ni-Fe-Cr enriched solid solution matrix. The hardness of the diffused zone/heat-affected zone is significantly high (760 ± 15HV) due to the presence of martensite followed by FZ hardness (410 ± 8HV) and then followed by base metal hardness (190 ± 4HV). The tensile properties of the fabricated weldment were evaluated by employing a computer-controlled universal testing machine. The tested weldment exhibits 475 MPa with an elongation of about 35%.

Determination of Ag in high-purity solutions of copper and nickel by high-resolution continuum-source electrothermal atomic absorption spectrometry (HR-CS-ETAAS)

A need to control the silver content in high-purity copper and nickel samples is attributed to the deterioration of the technical characteristics of materials when the presence of such impurities exceeds the permissible levels. In this study, modes for the determination of Ag in copper and nickel by high-resolution electrothermal atomic absorption spectrometry with a continuum source at a content of 10–6 – 10–5 % have been developed. The optimal temperature regimes of the atomizer program and the amount of chemical modifier introduced were developed proceeding from the results of studying the regularities of atomic absorption measurements of silver in matrix solutions of Cu and Ni (with a concentration of 10 g/liter each). To construct calibration dependences, aqueous standard solutions of the analyte (determination in copper) and aqueous standard solutions of the analyte with the addition of nickel nitrate 10 mg/liter (determination in nickel) were used. The atomization temperature was chosen to be 1600°C. The dosing volume of the solutions in the graphite furnace was always 20 μl. When determining Ag in high-purity copper, different temperatures of the pyrolysis stage were used for measurements with dosing of standard analyte solutions (600°C) and for measurements with dosing of the analyzed copper solution (800°C). In the determination of silver in nickel solutions, the temperature of the pyrolysis stage was 800°C. The developed conditions for the determination of silver were tested in the analysis of high-purity samples of copper and nickel (standard solutions of Inorganic Ventures, USA with a concentration of 10 g/liter) using spiked tests. The maximum value of the relative error of determinations does not exceed 13%. The detection limits for silver were: 1.8 × 10–6 % in copper and 3.2 × 10–6 % in nickel.

Automated Fixing Cost Estimation of Photovoltaic System Failures for the Creation of a Decision Support System

The increasing focus on sustainability connected to extended lifetimes with guaranteed high energy yields in the photovoltaic (PV) sector brings new challenges in operating and maintaining PV systems. Additionally, as the PV Terawatt Age has been reached in 2022 and a sustained exponential PV deployment growth is expected, operation and maintenance (O&M) companies have an ever‐increasing portfolio of PV plants to operate while maintaining cost competitive. Therefore, a shift from manual fault detection and solution toward smart and automated alternatives is required to keep downtime due to faults at a minimum while ensuring that PV systems can operate safely and efficiently. This work extends past developments of an automated O&M decision support system (DSS) by focusing on the automation of selecting and prioritizing solutions in case of PV system event/failure appearance. Thereby, the TRUST‐PV Solution Matrix is added to the published TRUST‐PV Risk Matrix, providing a standardized list of solutions for all events and failures which can appear in a PV system. Furthermore, the Cost Priority Number, a prioritization methodology to assess technical failures and their economic impact in energy systems, is improved by integrating automated fixing cost calculations into the DSS.

A model for solute evolution in laser powder bed fused Al-Si alloys and its application to improve thermal conductivity

A model capable of describing the solute evolution in laser powder bed fused (LPBF) Al-Si alloys has been proposed. The proposed model incorporates the use of three-dimensional Rosenthal equation and a rapid dendrite growth theory. Due to the analytical nature of the equation and the theory, the avoidance of modeling detailed microstructure of cells/dendrites as well as the eutectic, and the neglect of grain nucleation/elimination process, the proposed model is efficient at calculating, taking merely ∼10 min for portraying the spatial distribution of dissolved solute in an entire melt pool. The model was validated by scanning transmission electron microscopic-energy disperse spectrum (STEM-EDS) analysis. The validated model was subsequently applied in designing fabrication strategy of LPBF Al-Si alloys, in hope of improving the alloys’ thermal conductivity through purposefully adjusting processing parameters. This objective was successfully achieved, based on the fact that among imperfections induced by LPBF, dissolved solute atoms are the dominant influencing factor for thermal conductivity, and that the model can reveal the correlations between the overall amount of dissolved solute in the solid solution matrix and laser/feedstock powder parameters.

Metasurface-assisted Lab-on-fiber optrode for highly sensitive detection of vitamin D

The increasing demand for vitamin D status assessment has highlighted the need for rapid, sensitive, and user-friendly methods for its detection in biological samples potentially integrated in Point-of-Care (PoC) diagnostic devices. Detection of the major circulating form of vitamin D, 25-hydroxyvitamin D3-25(OH)D3, is particularly challenging due to the laborious procedures for sample preparation and its low molecular weight (∼400 Da), which requires highly sensitive detection methods. In this study, we developed a novel label-free Lab-on-Fiber biosensing platform for highly sensitive detection of 25(OH)D3 based on the integration of plasmonic metasurfaces (MSs) on the tip of a single-mode optical fiber (OF). A dedicated pipeline was carefully designed and developed to optimize the bio-functionalization of the plasmonic sensor tip to specifically detect the target biomolecule. The resulting MS-assisted Lab-on-fiber platform enables direct and highly sensitive detection of 25(OH)D3 in clinically relevant ranges (4–160 ng/mL), both in buffer solution and complex matrix, with limits of detection (LOD) of 1.40 ng/mL in saline buffer and 0.85 ng/mL in complex matrix. Overall, these results demonstrate that our platform can successfully and specifically detect small molecules in label-free configuration, with performances comparable to those of conventional methods used in clinical practice. The high degree of miniaturization combined with its high sensitivity makes our platform an exceptional building block for realizing valid diagnostic alternatives for label-free detection of clinically relevant analytes, which can be transformed into new low-cost, fast, simple, and ready-to-use PoC diagnostic devices with improved processability and performance compared to current methods.

Quantification of Total Sulfite in Shrimps by BIOFISH 300 SUL Method: First Action 2021.09.

Sulfite is the oldest and most widely used additive in our food supply with antioxidant and preservative properties. Due to its allergenic-like reactions and other adverse health effects, its use is regulated by international regulatory bodies. Therefore, food industries as well as regulatory laboratories must ensure that the maximum concentration of sulfite permitted is not exceeded. The AOAC INTERNATIONAL-approved official method for the quantification of sulfites is the Optimized Monier-Williams Method (AOAC Official Method 990.28), which consists of a time-consuming titration. The present study aims to demonstrate the reliability of the BIOFISH 300 SUL, a simple, fast, and accurate method, as an alternative, for the quantification of total sulfites in shrimp, with a lower LOQ than that of the OMA 990.28, set at 10 mg/Kg. The BIOFISH 300 SUL method is a highly specific biosensor based on its proprietary enzyme-based electrode, for the rapid quantification of total sulfite. The test kit consists of an electrochemical reader (biosensor BIOFISH 300) and disposable electrodes (Biotest) that are capable of providing an electrical signal proportional to the amount of sulfite in the sample analyzed. The method mainly consists of the extraction of sulfite from the solid matrix in an aqueous solution, and its subsequent quantification by the device in less than 3 min. Comparative studies between BIOFISH 300 SUL and OMA 990.28 were conducted for naturally contaminated and spiked samples of raw and boiled shrimp with sulfite levels covering the 7-150 mg/kg range in order to determine linearity, recovery, repeatability, intermediate reproducibility, and accuracy. The BIOFISH 300 SUL method demonstrated high accuracy and precision for the whole range of quantification (7-150 mg/kg). Its ease of use and fast response make it the ideal technology to be implemented by the industry. BIOFISH 300 SUL was adopted as a First Action Official MethodSM by the AOAC Expert Review Panel for Sulfites in Seafood Methods in February 2021 after rigorous review.

Multi-level Power Series Solution for Large Surface and Volume Electric Field Integral Equation

In this paper, we propose a new multi-level power series solution method for solving a large surface and volume electric field integral equation-based H-Matrix. The proposed solution method converges in a fixed number of iterations and is solved at each level of the H-Matrix computation. The solution method avoids the computation of a full matrix, as it can be solved independently at each level, starting from the leaf level. Solution at each level can be used as the final solution, thus saving the matrix computation time for full H-Matrix. The paper shows that the leaf level matrix computation and solution with power series gives as accurate results as the full H-Matrix iterative solver method. The method results in considerable savings time and memory savings compared to the H-Matrix iterative solver. Further, the proposed method retains the O(NlogN) solution complexity.

A novel complex variable solution for the stress and displacement fields around a shallow non-circular tunnel

A novel complex variable solution is derived in this paper for the stress and displacement fields around a shallow non-circular tunnel. The proposed method allows explicit computations in matrix form and has advantages of considerable efficiency and high accuracy. Firstly, the stress and displacement boundary conditions for the shallow non-circular tunnel are obtained using the generalized complex variable theory and conformal mapping technique. Then, the fast Fourier transform algorithm is employed to effectively perform the Fourier series fitting for these boundary conditions, and matrix equations for the potential functions in the frequency domain are established. Later, a matrix solution for the potential functions is formulated to determine the stress and displacement fields around the shallow non-circular tunnel. Finally, select numerical analyses are conducted to verify the proposed method, discuss the key parameters in the algorithm, and reveal the effect of the acceleration strategy using FFT as well as the effect of non-circular geometries on the stress and displacement fields.

Superhard bulk high-entropy carbides with enhanced toughness via metastable in-situ particles

Despite the extremely high hardness of recently proposed high-entropy carbides (HECs), the low fracture toughness limits their applications in harsh mechanical environment. Here, we introduce a metastability engineering strategy to achieve superhard HECs with enhanced toughness via in-situ metastable particles. This is realized by developing a (WTaNbZrTi)C HEC showing a solid solution matrix with uniformly dispersed in-situ tetragonal and monoclinic ZrO2 particles. Apart from a high hardness of 21.0 GPa, the HEC can obtain an enhanced fracture toughness of 5.89 MPa·m1/2, significantly exceeding the value predicted by rule of mixture and that of other reported HECs. The toughening effect is primarily attributed to the transformation of the metastable tetragonal ZrO2 particles under mechanical loading, which promotes crack tip shielding mechanisms including crack deflection, crack bridging and crack branching. The work demonstrates the concept of using in-situ metastable particles for toughening bulk high-entropy ceramics by taking advantage of their compositional flexibility.

FOESO-Net: A specific neural network for fast sensorless robot manipulator torque estimation

Contact torque sensing allows robot manipulators to cooperate with humans and detect accidental collisions in real time to ensure safety. Most sensorless torque estimation schemes, which are based on linear observer approaches, cannot compromise between non-negligible noise and high observation bandwidth. Therefore, fast time-varying nonlinear torque observation cannot be satisfied. To achieve this challenge, a customized network called FOESO-Net based on a novel fractional-order extended state observer is carefully designed in this paper. The network firstly chooses momentum as the benchmark state for torque estimation, which can avoid joint acceleration and model’s inverse inertia matrix solution. Then, a fractional-order extended state observer (FOESO) is proposed from the perspective of momentum control to better adapt to the nonlinear fast time varying torque. In addition, a fractional-order neural network and a weight update neural network parallel architecture are constructed to enable fractional-order and dynamic weight-based adaptive learning of FOESO parameters. Formal analysis and proofs are made to show that the error of FOESO-Net is convergent. Finally, the effectiveness of the proposed method is verified by numerical simulations and a real collaborative robot platform. Moreover, compared with existing methods, the FOESO-Net based torque estimation method can reduce the estimation error and response time, which illustrates the superiority of the designed method.

Gain margin and Lyapunov analysis of discrete‐time network synchronization via Riccati design

SummaryThis paper deals with solution analysis and gain margin analysis of a modified algebraic Riccati matrix equation, and the Lyapunov analysis for discrete‐time network synchronization with directed graph topologies. First, the structure of the solution to the Riccati equation associated with a single‐input controllable system is analyzed. The solution matrix entries are represented using unknown closed‐loop pole variables that are solved via a system of scalar quadratic equations. Then, the gain margin is studied for the modified Riccati equation for both multi‐input and single‐input systems. A disc gain margin in the complex plane is obtained using the solution matrix. Finally, the feasibility of the Riccati design for the discrete‐time network synchronization with general directed graphs is solved via the Lyapunov analysis approach and the gain margin approach, respectively. In the design, a network Lyapunov function is constructed using the Kronecker product of two positive definite matrices: one is the graph positive definite matrix solved from a graph Lyapunov matrix inequality involving the graph Laplacian matrix; the other is the dynamical positive definite matrix solved from the modified Riccati equation. The synchronizing conditions are obtained for the two Riccati design approaches, respectively.

Raman spectroscopy applied to online monitoring of a bioreactor: Tackling the limit of detection

An in-situ monitoring model of alcoholic fermentation based on Raman spectroscopy was developed in this study. The optimized acquisition parameters were an 80 s exposure time with three accumulations. Standard solutions were prepared and used to populate a learning database. Two groups of mixed solutions were prepared for a validation database to simulate fermentation at different conditions. First, all spectra of the standards were evaluated by principal component analysis (PCA) to identify the spectral features of the target substances and observe their distribution and outliers. Second, three multivariate calibration models for prediction were developed using the partial least squares (PLS) method, either on the whole learning database or subsets. The limit of detection (LOD) of each model was estimated by using the root mean square error of cross validation (RMSECV), and the prediction ability was further tested with both validation datasets. As a result, improved LODs were obtained: 0.42 and 1.55 g·L−1 for ethanol and glucose using a sub-learning dataset with a concentration range of 0.5 to 10 g·L−1. An interesting prediction result was obtained from a cross-mixed validation set, which had a root mean square error of prediction (RMSEP) for ethanol and glucose of only 3.21 and 1.69, even with large differences in mixture concentrations. This result not only indicates that a model based on standard solutions can predict the concentration of a mixed solution in a complex matrix but also offers good prospects for applying the model in real bioreactors.

The Construction of the integration of ldeological and Political Curriculum for Graduate Students in Foreign Language Studies in the Context of New Liberal Arts and Big Data

Abstract Exploring the construction, of course, Civics of graduate students in foreign languages is to promote better the implementation of course, Civics in foreign languages. In this paper, in the context of the new liberal arts of big data, firstly, the method related to the sparrow search algorithm is described, and the parameters related to the sparrow search algorithm are optimized by using the good point set initialization and firefly update strategy. Then the basic principle of the extreme learning machine is given, and it is shown that the ELM model’s output weights are obtained using the inverse matrix solution. The ISSA-ELM algorithm model is elicited using the improved sparrow search algorithm with the extreme learning machine, and the ARE and RMSE performance validation is performed for this model using the UCI dataset. Finally, the ISSA-ELM algorithm was used to analyze and mine the indexes of the construction of the example of the postgraduate course Civics in foreign languages, including both teaching implementation and teaching content, using GZ University as an example. From the teaching implementation, the percentages of A, B, C and D evaluations are 16.12%, 18.44%, 18.12% and 47.32%, respectively. Regarding teaching content, the percentages of A, B, C, and D evaluations were 49.65%, 22.95%, 16.5%, and 10.89%, respectively. This indicates that the construction of the course Civics for graduate students in foreign language disciplines in the context of the new liberal arts is not optimistic, and effective reforms in teaching implementation and content are needed afterward.