Prognostics and RUL Estimations of SAC305, SAC105 and SnAg Solders Under Temperature and Vibration Using Long Short-Term Memory (LSTM) Deep Learning

Prognostics and Remaining Useful Life (RUL) estimations of complex systems are essential to operational safety, increased efficiency, and help to schedule maintenance proactively. Modeling the remaining useful life of a system with many complexities is possible with the rapid development in the field of deep learning as a computational technique for failure prediction. Deep learning can adapt to multivariate parameters complex and nonlinear behavior, which is difficult using traditional time-series models for forecasting and prediction purposes. In this paper, a deep learning approach based on Long Short-Term Memory (LSTM) network is used to predict the remaining useful life of the PCB at different conditions of temperature and vibration. This technique can identify the different underlying patterns in the time series that can predict the RUL. This study involves feature vector identification and RUL estimations for SAC305, SAC105, and Tin Lead solder PCBs under different vibration levels and temperature conditions. The acceleration levels of vibration are fixed at 5g and 10g, while the temperature levels are 55°C and 100°C. The test board is a multilayer FR4 configuration with JEDEC standard dimensions consists of twelve packages arranged in a rectangular pattern. Strain signals are acquired from the backside of the PCB at symmetric locations to identify the failure of all the packages during vibration. The strain signals are resistance values that are acquired simultaneously during the experiment until the failure of most of the packages on the board. The feature vectors are identified from statistical analysis on the strain signals frequency and instantaneous frequency components. The principal component analysis is used as a data reduction technique to identify the different patterns produced from the four strain signals with failures of the packages during vibration. LSTM deep learning method is used to model the RUL of the packages at different individual operating conditions of vibration for all three solder materials involved in this study. A combined model for RUL prediction for a material that can take care of the changes in the operating conditions is also modeled for each material.

A New Optimization Algorithm Based on the Fungi Kingdom Expansion Behavior for Antenna Applications

This paper presents a new optimization algorithm based on the behavior of the fungi kingdom expansion (FKE) to optimize the radiation pattern of the array antenna. The immobile mass expansion of the fungi is mimicked in this work as a chaotic behavior with a sinusoidal map function, while the mobile mass expansion is realized by a linear function. In addition, the random germination of the spores is utilized for randomly distributing the variables that are far away from the best solution. The proposed FKE algorithm is applied to optimize the radiation pattern of the antenna array, and then its performance is compared with that of some well-known algorithms. The MATLAB simulation results verify the superiority of the proposed algorithm in solving 20-element antenna array problems such as sidelobe reduction with sidelobe ratio (SLR = 25.6 dB), flat-top pattern with SLR = 23.5 dB, rectangular pattern with SLR = 19 dB, and anti-jamming systems. The algorithm also results in a 100% success rate for all of the mentioned antenna array problems.

Commodity Image Classification Based on Improved Bag-of-Visual-Words Model

With the increasing scale of e-commerce, the complexity of image content makes commodity image classification face great challenges. Image feature extraction often determines the quality of the final classification results. At present, the image feature extraction part mainly includes the underlying visual feature and the intermediate semantic feature. The intermediate semantics of the image acts as a bridge between the underlying features and the advanced semantics of the image, which can make up for the semantic gap to a certain extent and has strong robustness. As a typical intermediate semantic representation method, the bag-of-visual-words (BoVW) model has received extensive attention in image classification. However, the traditional BoVW model loses the location information of local features, and its local feature descriptors mainly focus on the texture shape information of local regions but lack the expression of color information. Therefore, in this paper, the improved bag-of-visual-words model is presented, which contains three aspects of improvement: (1) multiscale local region extraction; (2) local feature description by speeded up robust features (SURF) and color vector angle histogram (CVAH); and (3) diagonal concentric rectangular pattern. Experimental results show that the three aspects of improvement to the BoVW model are complementary, while compared with the traditional BoVW and the BoVW adopting SURF + SPM, the classification accuracy of the improved BoVW is increased by 3.60% and 2.33%, respectively.

One-Dimensional Consolidation of Viscoelastic Soils Incorporating Caputo-Fabrizio Fractional Derivative

In this paper, the Caputo-Fabrizio fractional derivative is introduced to investigate the one-dimensional consolidation behavior of viscoelastic soils. Using the Caputo-Fabrizio operator, a novel four-element fractional-derivative model is proposed to capture the viscoelastic properties of the soils, and further the one-dimensional consolidation equation is derived to simulate the consolidation behavior of the soils. Using the techniques of eigenfunction expansion and Laplace transform, a series of analytical solutions are derived to calculate the excess pore-water pressure and the average degree of consolidation of the soils. The total vertical stress in the soil is assumed to change linearly with depth, and its distribution patterns are classified to rectangular pattern, trapezoidal pattern and inverse trapezoidal pattern. Four loading types including instantaneous loading, ramp loading, sinusoidal loading and general cyclic loading are considered. Then, a comparison for several special cases is presented to verify the correctness of the proposed solutions through comparing with existing theories. Moreover, two examples considering ramp and sinusoidal loadings are given to study the consolidation behavior of the viscoelastic soils incorporating the Caputo-Fabrizio fractional derivative.

Influence of Various Pulse Waveforms during Fabrication of Micro Rectangular Pattern by Masked Tool using Electrochemical Micromachining

Maskless electrochemical micromachining (EMM) is an alternative method to fabricate microsurface textures on conductive substances, but it is still very challenging issue to create microsurface textures by this method. This paper proposes a new issue that maskless EMM process generates micro rectangular patterns using various pulse waveforms i.e. triangular, sine and square of pulsed DC power supply at constant voltage mode on stainless steel (SS-304) workpiece. A novel concept of maskless EMM setup consisting of EMM cell, electrode holding devices, electrical connections and vertical cross flow electrolyte system is introduced for the generation of high-quality micro rectangular patterns using various pulse waveforms. Another important finding is that SU-8 2150 negative photoresist can fabricate more than 28 micro rectangular patterned samples with higher dimensional accuracy and surface quality. The influence of machining voltage, inter electrode gap, pulse frequency, duty ratio and flow rate is investigated on machining performance such as length overcut, width overcut, machining depth and surface roughness ([Formula: see text] of micro rectangular pattern using three pulse waveforms. One mathematical model is developed to show the effectiveness of three pulse waveforms by the estimation of current efficiencies. From the experimental investigation, it is observed that higher frequency with square waveform at constant duty ratio is suitable to generate high-quality micro rectangular patterns under pulsed DC power supply.

Investigating the Economical Performance of Four Suggested Designs for the Heat Exchangers

It is required to investigate the economy of the performance of four suggested heat exchanger designs. The economy criteria are expressed by the ratio of the Nusselt number, Nu, and the pressure loss coefficient, ΔP∗. The four patterns are; rectangular, zigzag, spiral, and narrow-spiral. The air passages of each one of the four types have the same cross-section area and air passage length. Also, the inlet air temperature and flow rate for both; the air and water are the same in the four types. The narrow-spiral pattern has an equal passage thickness for both air and water. Reynolds number, Re, of values; 2535, 7606, 12677, 17748, 20284, 22819, 25355, (based on the hydraulic diameter of the cross-section) are investigated. For validation, the rectangular pattern type was checked experimentally, and the results were close to those of the prediction. For all values of the Reynolds number, the suggested narrow-spiral pattern exhibited the highest values of Nu/ΔP∗. At the Reynolds number of 25355, the ratio, Nu/ΔP∗ could achieve a value of about 15.74 for the narrow-spiral type. For each suggested pattern, (Nu/ΔP∗) and Re are correlated in a suitable formula.

Spectral Engineering via Complex Patterns of Circular Nano-object Miniarrays: I. Convex Patterns Tunable by Integrated Lithography Realized by Circularly Polarized Light

Illumination of colloid sphere monolayers by circularly polarized beams enables the fabrication of concave patterns composed of circular nanohole miniarrays that can be transferred into convex metal nano-object patterns via a lift-off procedure. Unique spectral and near-field properties are achievable by controlling the geometry of the central nanoring and quadrumer of slightly rotated satellite nanocrescents and by selecting those azimuthal orientations that promote localized plasmon resonances. The spectral and near-field effects of hexagonal patterns composed of uniform gold nanorings and nanocrescents, which can be prepared by transferring masks fabricated by a perpendicularly and obliquely incident single homogeneous circularly polarized beam, were studied to uncover the supported localized plasmonic modes. Artificial rectangular patterns composed of a singlet nanoring and singlet nanocrescent as well as quadrumer of four nanocrescents were investigated to analyze the effect of nano-object interactions and lattice type. It was proven that all nanophotonical phenomena are governed by the azimuthal orientation independent localized resonance on the nanorings and by the C2, C1, and U resonances on the nanocrescents in case of $\bar {E}$ Ē -field direction perpendicular and parallel to their symmetry axes. The interaction between localized surface plasmon resonances on individual nano-objects is weak, whereas scattered photonic modes have a perturbative role at the Rayleigh anomaly only on the larger periodic rectangular pattern of miniarrays. Considerable fluorescence enhancement of dipolar emitters is achievable at spectral locations promoting the C and U resonances on the constituent nano-object.

Spectral Engineering Via Complex Patterns of Circular Nano-Object Miniarrays: II. Concave Patterns Tunable by Integrated Lithography Realized by Circularly Polarized Light

The use of circularly polarized beams in interferometric illumination of colloid sphere monolayers enables the direct fabrication of rectangular patterns composed of circular nanohole miniarrays in metal films. This paper presents a study on the spectral and near-field effects of complex rectangular patterns consisted of a central nanoring and slightly rotated satellite nanocrescents in azimuthal orientations, which promote coupling between localized and propagating plasmons. To inspect the localized modes separately, we investigate the spectral responses and near-field phenomena of hexagonal patterns composed of uniform nanorings and nanocrescents, which can be fabricated by a single, homogeneous, circularly polarized beam incident perpendicularly and obliquely, respectively. To understand the interaction of localized and propagating modes, we analyze artificial rectangular patterns composed of a singlet nanoring, a singlet horizontal nanocrescent, and a quadrumer of four slightly rotated nanocrescents. The results demonstrate that on the rectangular pattern of a singlet horizontal nanocrescent the interacting C2 and C1 localized resonances in the C orientation ($$0^{\circ }$$ 0 ∘ azimuthal angle) and the U localized resonance coupled with propagating surface plasmon polaritons (SPPs) in the U orientation ($$90^{\circ }$$ 90 ∘ azimuthal angle) manifest themselves in similar split spectra. Moreover, split spectra appear due to the coupling of the azimuthal orientation independent localized resonance on the nanorings and the SPPs propagating on their rectangular pattern in the U orientation. The spectral response of the complex miniarray pattern can be precisely tuned by varying the geometrical parameters of the moderately interacting nanoholes and the pattern period. In appropriate configurations, the fluorescence of the dipolar emitters is enhanced, which has potential applications in bio-object detection.

Permittivity of 3D-Printed Nylon Substrates with Different Infill Patterns and Densities for Design of Microwave Components

Printed circuit boards, chemical etching, and computer numerical control milling currently dominate industrial processes for manufacturing microwave components. However, these manufacturing methods do not provide the flexibility for customization possible with additive manufacturing. Additive manufacturing (AM) has the potential to fabricate microwave components for desired frequency ranges with less effort in prototyping and fabrication. Relative permittivity (εr) of materials is a critical parameter in microwave component design, yet the value changes during the AM process. This article investigates how relative permittivity for nylon substrates, created with AM, changes with different infill densities and infill patterns. The measurement method and procedure can be used to design AM microwave components like antennas or dielectric-filled waveguides with desired characteristics. The two-microstrip-line method was used and improved for the accurate and convenient measurement of the relative permittivity of AM nylon substrates. Several nylon substrates with different infill patterns, including rectangular, hexagonal, triangular, and solid, were fabricated with AM to demonstrate how the relative permittivity value changes as the infill density increases. A linear relationship between the infill density of the rectangular pattern and the substrate permittivity was found. The permittivity data were applied to the design of a rectangular patch antenna for use in the 2.5-GHz WiMAX band. The fabricated antenna with AM, which was tested using a vector network analyzer, showed good agreement with simulation results. The method and procedure of permittivity measurements are specially designed to be applied in the design of microwave components with AM dielectric substrates.

Influence of electron beam oscillation patterns on the microstructure, texture, residual stress and mechanical properties of Ti-5Al-2.5Sn alloy weldments

Vacuum electron beam welding is widely employed for the welding of titanium alloys using different beam oscillation patterns. Since these patterns influence the physical phenomenon in the weld pool, its effect on the microstructure, texture, mechanical properties and residual stresses is of prime interest. In order to understand this influence, electron beam welding was used to prepare Ti-5Al-2.5Sn weldments using beam oscillations of triangular and rectangular waveform. It was observed that a change of welding pattern had a strong influence on the residual stresses, impact properties and texture of weld zone while tensile properties were not significantly affected. A partial martensitic transformation was observed in both the triangular and rectangular waveform of oscillations. An increase in alpha lathe width was observed in the fusion zone and similar strength of the rectangular pattern as compared to triangular pattern. Despite of this, the observed higher Vickers hardness of the fusion zone of rectangular pattern as compared to triangular and no-oscillation was attributed to texture strengthening using rectangular waveform.