Single-stage Solution Research Articles

Adaptive Long-Neck Network With Atrous-Residual Structure for Instance Segmentation

Instance segmentation is an important yet challenging task in the computer vision field. Existing mainstream single-stage solution with parameterized mask representation has designed the neck models to fuse features of different layers; however, the performance of instance segmentation is still restricted to the layer-by-layer transmission scheme. In this article, an instance segmentation framework with an adaptive long-neck (ALN) network and atrous-residual structure is proposed. The long-neck network is composed of two bidirectional fusion units, which are cascaded to facilitate the information communication among features of different layers in top-down and bottom-up pathways. In particular, a new cross-layer transmission scheme is introduced in a top-down pathway to achieve a hybrid dense fusion of multiscale features and weights of different features are learned adaptively according to their respective contributions to promote the network convergence. Meanwhile, a bottom-up pathway further complements the features with more location clues. In this way, high-level semantic information and low-level location information are tightly integrated. Furthermore, an atrous-residual structure is added to the mask prototype branch of instance prediction to capture more contextual information. This contributes to the generation of high-quality masks. The experimental results indicate that the proposed method achieves effective segmentation and the outputted masks match the contours of objects.

Effect of two-stage solution on microstructure and mechanical property of IN718 alloy fabricated by selective laser melting

The substructure characteristics and mechanical properties of the IN718 alloy prepared via selective laser melting in the as-deposited state and different solid solution states were studied. The effects of the substructure characteristics, which include precipitates and grain boundary features, on the microhardness of the IN718 alloy were investigated. It was found that the main substructure of the as-deposited alloy is a cellular structure, which is formed owing to the 50-nm-thick segregation band of the Nb and Ti elements. The two-stage and single-stage solution processes can both prevent the microsegregation of the as-deposited state, but the two-stage solution process can make the composition more uniform; at the same time, it leads to a large number of twin boundaries. The δ phase precipitates mostly in the single-stage solution process at 980 °C, but the two-stage solution process can effectively inhibit the precipitation of the δ phase. The hardness of the alloy after the two-stage solution process is lower than that of the alloy after the single-stage solution process. The main strengthening mechanism of the as-deposited alloy consists of strain strengthening. The strengthening effect of the δ precipitate is lower than the strain strengthening caused by the grain boundaries of the alloy.

Experimental Investigation to Confirm the Presence of TiB2 Reinforcements in the Matrix and Effect of Artificial Aging on Hardness and Tensile Properties of Stir-Cast LM4-TiB2 Composite

The present work focuses on the effect of multistage solution heat treatment (MSHT) and artificial aging on two-stage stir-cast LM4 + TiB2 (1, 2, and 3 wt.%) composites on the mechanical properties as compared to as-cast and single-stage solution heat-treated (SSHT) composites. Two novel tests, viz. the confirmation hardness test and the chemical analysis test, were performed to ensure the soundness of the casting and uniform distribution of TiB2 within the matrix. Samples subjected to MSHT + aging at 100–200 °C displayed the highest hardness and UTS values compared to as-cast and SSHT + aging at 100–200 °C samples. Compared to as-cast alloy, peak-aged samples of 1–3 wt.% (MSHT + aging at 100 °C), hardness values improved from 107–150%, and UTS values improved from 47–68%. The presence of metastable phases (θ′-Al2Cu and θ″-Al3Cu) and of hard TiB2 particles are the reason for the improvement in the properties. Peak aged LM4 + 3 wt.% TiB2 composite displayed the highest hardness of 175 VHN and UTS of 251 MPa. Fracture analysis of the LM4 alloy showed dimple rupture, and its composites revealed quasi-cleavage fracture. Based on the overall results, the inclusion of TiB2, MSHT, and artificial aging treatment on the LM4 alloy significantly influenced the composites’ mechanical properties.

A Modulation Method for Capacitance Reduction in Active-Clamp Flyback-Based AC–DC Adapters

Recent developments of fast-charging power delivery protocols are driving ac–dc adapters to 100-W power ranges. Conventional solutions in this power range employing a two-stage topology and a big twice-line frequency buffer capacitor are generally costly and bulky. This article presents a patent-pending modulation method for an active-clamp flyback converter, allowing for a single-stage adapter design with reduced capacitance requirements and higher efficiency. This is achieved by exploiting the inherent energy storage capability of the clamping capacitor while turning it into an active power buffer. No hardware modifications are needed, while all salient features of active-clamp flyback converter, i.e., soft switching and leakage recycling, are retained. Operating principles and detailed controller design are discussed, and a 100-W laboratory prototype is built. The prototype achieves 94% peak efficiency and up to 92% size reduction of the buffer capacitor. The experimental evaluation shows that the new single-stage solution enabled by the proposed modulation method is superior to the conventional two-stage and single-stage solutions in terms of cost, conversion efficiency, and power density.

Osteochondral Allografts in Knee Surgery: Narrative Review of Evidence to Date.

Knee articular cartilage defects can result in significant pain and loss of function in active patients. Osteochondral allograft (OCA) transplantation offers a single-stage solution to address large chondral and osteochondral defects by resurfacing focal cartilage defects with mature hyaline cartilage. To date, OCA transplantation of the knee has demonstrated excellent clinical outcomes and long-term survivorship. However, significant variability still exists among clinicians with regard to parameters for graft acceptance, surgical technique, and rehabilitation. Technologies to optimize graft viability during storage, improve osseous integration of the allograft, and shorten recovery timelines after surgery continue to evolve. The purpose of this review is to examine the latest evidence on treatment indications, graft storage and surgical technique, patient outcomes and survivorship, and rehabilitation after surgery.

Towards strength-ductility synergy through an optimized two-stage solution treatment in Al–7Si–3Cu-0.5Mg alloys

In order to obtain superior mechanical properties, the incipient melting and maximum dissolution of Cu-containing phases, spheroidization and coarsening of eutectic Si phase in Al–Si–Cu–Mg alloy are important factors that should be considered during solution treatment. However, the conventional single-stage solution treatment was difficult to meet this requirement. In this study, an optimized two-stage solution treatment (495 °C/8 h + 515 °C/4 h) was established for Al–7Si–3Cu-0.5 Mg casting alloys through systematically investigating the microstructure evolution at different solution temperatures (470 °C, 495 °C, 515 °C and 525 °C). The first stage (495 °C/8 h) was applied to dissolve most Cu-containing phases and avoid incipient melting, while the employ of the second one (515 °C/4 h) was to promote fast spheroidization of eutectic Si phase and prevent severe overheating. Two modified quality indexes evaluated the synergy of strength and ductility indicated that the optimized two-stage solution treatment and the subsequent aging treatment (175 °C/8 h) gave rise to an optimization (QIU = 537.1 MPa, QIT = 0.47) on the strength and ductility of Al–7Si–3Cu-0.5 Mg alloys, as compared with the alloys (QIU = 527.4 MPa, QIT = 0.46) under the conventional heat treatment including a single-stage solution treatment (515 °C/16 h). The strength-ductility synergy was arisen from the fuller dissolution of Cu-containing phases, the finer eutectic Si phase, the depletion in number density of micropores and the precipitation of nano-sized Q′ and θ′ particles. 0.3 wt% Zr addition further increased the modified quality indexes (QIU = 549.5 MPa, QIT = 0.50), which was attributed to the grain refinement and the formation of nanoscale Al–Si–Zr precipitates. Furthermore, the fracture mechanism of the obtained alloys was also discussed.

Artificial Neural Network for Predicting Hardness of Multistage Solutionized and Artificially Aged LM4 + TiB2 Composites

Aluminium casting alloy LM4 (EN 1706 AC-45200) composites with TiB2 (1, 2, and 3 wt.%) as reinforcements were produced using the two-stage stir casting method. OM and SEM study shows uniform and homogeneous reinforcement distribution in LM4 + TiB2 composites. As-cast composites were subjected to single-stage solution treatment at 520°C for 2 h and multistage solution treatment at 495 and 520°C for 2 and 4 h, followed by hot water quenching at 60°C and aging at 100 and 200°C for different time intervals. The hardness of as-cast and artificially aged composites were compared in both conditions. Compared to as-cast LM4 alloy, 20-45% improvement in hardness was observed for LM4 + TiB2 as-cast composites. 60-150% improvement in hardness was observed in artificially aged LM4 + 3 wt.% TiB2 composites when aged at 100 and 200°C during peak aged conditions. TEM images confirmed the presence of primary strengthening solute-rich phases after age hardening treatment such as θ’-Al2Cu and θ”-Al3Cu, which are responsible for hardness increment. An artificial neural network (ANN) model was created to predict the hardness trend of these composite samples using MATLAB R2021b, and results proved that the ANN model developed can be utilized as an effective tool to predict the hardness of treated composite samples.

Effects of single- and multi-stage solid solution treatments on microstructure and properties of as-extruded AA7055 helical profile

The effects of single-stage solution treatment (SST), enhanced solution treatment (EST), high-temperature pre-precipitation (HTPP) and multi-stage solution treatment (MST) on the microstructure, mechanical properties and corrosion resistance of the as-extruded 7055 aluminium alloy (AA7055) helical profile were investigated using differential scanning calorimetry (DSC), optical microscopy (OM), scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). It was observed that EST and MST could promote the dissolution of the second-phase particles compared with the traditional SST, and the intergranular phases were distinctly discontinuously distributed after HTPP and MST. There was obvious difference in the main texture type and texture strength for the alloy after different solid solution treatments. HTPP could improve the corrosion resistance of the alloy by regulating the intergranular phases, but the mechanical properties were severely weakened. While the good corrosion resistance of the alloy could be obtained by MST without obvious strength loss. As a result, the MST is an ideal solid solution treatment scheme for AA7055.

Effect of Heat Treatment on Microstructure and Properties of Al-7.0Zn-1.5Cu-1.5Mg-0.1Zr-0.1Ce Alloy

To obtain excellent properties in 7××× series aluminum alloys, the heat treatment process used is an important factor. This needs to be chosen according to the different alloy compositions. A 7××× series aluminum alloy with high zinc content (Zn/Mg > 4, Mg/Cu = 1) was prepared. Studying the heat treatment process of the alloy is important to guide companies in its industrial production. The optimum heat treatment process is explored from a microstructure point of view. The alloy was melted and cast in the laboratory using a metallurgical method. The microstructure, fracture morphology, and mechanical properties of the alloy were examined by metallographic microscopy, scanning electron microscopy, transmission electron microscopy (TEM), and tensile testing. Research on the alloy solution treatment was emphasized. The results showed that the solution effect was optimum at 470 °C × 1 h during a single-stage solution treatment. The recrystallization degree was low when the two-stage solution treatment process was 450 °C × 0.5 h + 475 °C × 0.5 h due to the release of deformation energy at low temperature; at the same time, the second-order solid-solution temperature was high, the solid-solution effect was better than in the single-stage solid-solution treatment, and the comprehensive mechanical properties of the alloy were better.

Emulation of Loss Free Resistor for Single-Stage Three-Phase PFC Converter in Electric Vehicle Charging Application

In this article, the modular three-phase ac-dc converter using single-phase isolated Ćuk rectifier modules for charging of electric vehicles is discussed. The converters are designed and analyzed for the continuous conduction mode (CCM). This article is based on a new concept of adaptive sliding-mode-based loss-free resistor (ASLFR). ASLFR is a control scheme, which allows dual aim of power factor correction along with tight voltage regulation; hence, the adopted topology serves as a fitting single-stage solution for balanced three-phase systems. Complete theory is developed for the application, and the effectiveness of the scheme is well-established. Various studies to confirm the robustness of the system to any load and line variation are carried out. Moreover, a qualitative analysis is also made to show the expediency of the proposed ASLFR. Simulation as well as experimental studies are claimed theoretically.

Three-Phase Split-Source Inverter-Fed PV Systems: Analysis and Mitigation of Common-Mode Voltage

Common-mode voltage (CMV), caused by standard high-frequency pulsewidth modulated (PWM) voltage source inverters (VSIs), is a major area of interest in various applications, such as electric motor drives, transformerless photovoltaic systems, and grid-tied inverters. Since VSIs have only the buck capability during the inversion mode, an additional boosting stage either in the dc side or in the ac side has to be utilized for low-voltage-fed applications. On the other hand, single-stage solutions, with buck and boost capabilities, represent an interesting alternative with reduced cost, complexity, and converter volume. Among the possible single-stage solutions, split-source inverter (SSI), which has been recently proposed, has several merits over its counterparts. One of the questionable aspects concerning this topology is the CMV, which has not been investigated yet. This article examines the induced CMV with the SSI. This is done by examining the CMV waveforms for VSI and SSI topologies, and then, comparing each other under different PWM schemes. Furthermore, this article proposes the use of the discontinuous space vector PWM scheme with the SSI to mitigate the CMV, where the analysis shows a significant reduction in the CMV compared to the other schemes. In order to validate the introduced analysis, simulation model has been designed using MATLAB/Simulink environment, and simulation results are presented. Moreover, a prototype has been built-up for testing the proposed concepts and the obtained experimental results are provided.

Effect of solid solution process on microstructure and properties of 6082 aluminum alloy

In this paper, the effect of solid solution on the microstructure and hardness of 6082 aluminum alloy experiencing hot rolling were investigated by optical microscopy, scanning electron microscopy (SEM), energy spectrum analysis (EDS) and Stretching test. The results showed that the second phase (Mg2Si) in the experimental alloy is a soluble phase, and the Fe-containing impurity is an insoluble phase. After the single-stage solution treatment, the degree of solid solution, recrystallization and the size of recrystal grain increased with the increasing of solid solution temperature. It was found that when the temperature increases, the recrystallization took place, and the crystal grains become coarse, resulting in the disappearance of the rolling effect and the deterioration of the mechanical properties. Moreover, the 6082 aluminum alloy exhibits high quench sensitivity, which can be alleviated by the two-stage solid solution. The results showed that the optimized two-stage solution is (515 °C, 0.5 h) + (545 °C, 0.5 h) under the conditions of the existing experiments in this study. In addition, after aging at 170 °C for 8 h, the tensile strength reached a maximum of 349 MPa.

Hot Deformation of 18 % Ni Maraging Steels: A Review

Abstract The published literature makes reference to the excellent hot workability of 18 % nickel maraging steels. However, production of large cross-sectioned products of 18 % nickel maraging steels by hot deformation can lead to different types of quality problems, such as (i) inadequate recrystallization and grain structure aligned in working direction, resulting in directionality of mechanical properties; (ii) thermal embrittlement that leads to poor values of ductility and fracture toughness; and (iii) sharp increase in flow stress with decreasing hot working temperature, necessitating the application of high loads for deformation at relatively low temperatures. To overcome these problems, primarily two sets of studies have been carried out by researchers. One set of studies was centered around the development of an optimum post–hot work solution treatment. Two-stage solution treatments, as opposed to standard single-stage solution treatment at 820°C, have been developed and are shown to lead to a fine-grained microstructure and an excellent combination of strength and fracture toughness with a high degree of isotropy. It has been documented that such heat treatments can also rejuvenate the quality of the products produced through a nonoptimum hot deformation schedule. The other set of studies was focused on establishing deformation processing maps using hot isothermal uniaxial compression testing. Different grades of 18 % nickel maraging steels have been the subject of investigation. Based on these studies, regimes of strain rate and temperature have been identified for optimum processing. Regimes in which flow localization occurs and hence need to be avoided have been identified. Processing regimes for obtaining fine-grained microstructures have been identified; regimes that lead to coarse grains, which need to be avoided, have been established. Constitutive equations have been developed to predict the deformation behavior as an aid to the design of the hot deformation process.

A Maximum-Output-Power-Point-Tracking-Controlled Dual-Active Bridge Converter for Photovoltaic Energy Integration Into MVDC Grids

This paper presents a novel maximum output power point tracking (MOPPT) strategy for a three-phase dual-active bridge (DAB3) converter to integrate a large-scale photovoltaic (PV) energy generation into medium-voltage dc grids. The DAB3 converter is employed as a single-stage solution to step up dc voltage levels and perform the maximum power point tracking of the PV farm at the same time. In order to achieve a high weighted average efficiency over a wide operation range, design considerations of the stray inductance and transformer's turns ratio are presented to shape the soft-switching region of the DAB3 converter in order to match the area of the maximum power points for the PV panels in the given environmental conditions. To further maximize the energy yield of the entire PV power generation system, a novel MOPPT method is proposed to track the maximum output power point of the DAB3 converter. The MOPPT is implemented by a cascaded closed-loop voltage control with the PV current feedforward compensation to improve the dynamic performance. The effectiveness of the proposed control strategy is validated by both simulations and the experimental verification of a down-scaled laboratory prototype.

High Power Density Z-Source Resonant Wireless Charger With Line Frequency Sinusoidal Charging

Wireless charger for electric vehicles (EVs) is an offline application and it needs power factor correction (PFC) function, which usually consists of a front-end boost PFC and a cascaded dc–dc converter. Z-source resonant converter (ZSRC), a single-stage solution with low cost and high efficiency, was proposed for EV wireless charger lately. The Z-source capacitors in the ZSRC are designed to absorb the double-line frequency ripple in this single-phase application. Sinusoidal charging, which allows the double-line frequency ripple propagate to the output, is another solution aiming at reducing the bulky capacitors. Recently, a comparison of low-frequency (120 Hz) sinusoidal charging and dc charging shows a negligible impact on Li-ion batteries’ performance. Therefore, the ZSRC's capacitor, the biggest component, can be reduced dramatically from millifarad to several microfarads with a sinusoidal charging technique, which features the ZSRC high power density. Also, it keeps the Z-source's benefit of boost ability and being immune to shoot-through problems. In this paper, the sinusoidal charging behavior for the ZSRC is modeled, and a control scheme that has both PFC function and load regulation for sinusoidal charging is proposed. This control scheme can pass IEC61000-3-2 Class A criterion. Experimental results based on a 1-kW prototype with 20 cm air gap between the primary and secondary side are presented to illustrate the proposed control scheme.

Zero Defect Manufacturing Strategies for Reduction of Scrap and Inspection Effort in Multi-stage Production Systems

Multi-stage production systems offer a huge potential for defect compensation and defect propagation avoidance on system level, in contrast to current single-stage solutions, in order to reduce scrap and to minimize time-consuming and cost-intensive quality control. Integration of additional sensor systems and sophisticated analysis of the acquired signals enable strategies in the field of downstream compensation, inline rework and enhanced process control without including additional process and inspection stages. The presented strategies are validated in three emerging European industrial sectors (aerospace, railway and medical) yielding a universal solution for zero defect manufacturing in multi-stage production systems.

SiC-Based Z-Source Resonant Converter With Constant Frequency and Load Regulation for EV Wireless Charger

Traditional load regulation methods for a resonant converter mainly rely on frequency modulation. It is always a tradeoff between the design of the resonant network and the range of load. Especially for wireless power transfer (WPT) systems, the resonant network usually has a high quality factor. Small variation on frequency leads to huge drop in gain and efficiency. Due to this problem, many WPT systems are unregulated and they need one or two more front-end stages to regulate the dc bus voltage and perform power factor correction (PFC). In order to lower the cost and complexity of two- or three-stages structure, a single-stage solution with a silicon carbide (SiC) based Z-source resonant converter (ZSRC) was recently proposed. The Z-source network provides high reliability as being immune to shoot-through problems. Additionally, a ZSRC can boost the dc bus voltage while the traditional voltage-source inverter can only produce a lower voltage. However, the load regulation of this new topology has not been addressed. Two effective load regulation methods with constant frequency are presented for this SiC-based ZSRC specifically. Operation principle of the two load regulation methods are described in this paper. Experimental results based on a 200-W scale-down prototype with a full-bridge series resonant dc–dc converter are presented to illustrate the mechanism of these two methods.

A Technique for Reduction of Edentulous Fractures Using Dentures and SMARTLock Hybrid Fixation System.

Summary:Establishing anatomic reduction of an edentulous mandible fracture is a frequently acknowledged challenge in craniomaxillofacial trauma surgery. In this study, we report a novel method for the reduction of the edentulous mandible fracture, via fabrication of modified Gunning splints using existing dentures and SMARTLock hybrid arch bars. This technique dramatically simplifies the application of an arch bar to dentures, obviates the need for the fabrication of impressions and custom splints, and eliminates the lag time associated with the creation of splints. Furthermore, this method may be used with or without adjunctive rigid internal fixation. The technique described herein of creating Gunning splints with SMARTLock hybrid arch bars provides surgeons with a simple, rapid, single-stage solution for reduction of mandibular fractures in the edentulous patient.

Effect of Solution Treatment on the Properties and Microstructural Evolution of Al-Zn-Mg-Cu-Er-Zr Alloy

Effect of solution treatment on the properties and microstructural evolution of Al-Zn-Mg-Cu-Er-Zr alloy was investigated by hardness test, conductivity test, exfoliation corrosion test, scanning electron microscope (SEM), transmission electron microscopy (TEM). The results show that the hardness of single-stage solution treated samples first increase and then decrease, the conductivity and volume fraction of the residual phase particles decrease with increasing solution temperature. Compared to conventional multi-stage solution, slow heating process solution treatment can dissolve plenty of residual phases and further improve the hardness and decrease conductivity. Besides, the effect of solution treatment on EXCO is discussed, the result of exfoliation corrosion of SHT8 sample test is judged as EA. Moreover, the effect of the presence of nanometer-sized Al3(Er,Zr) particles on the microstructural evolution during solution treatment has also been discussed in detailed.

A solar PV water pumping solution using a three-level cascaded inverter connected induction motor drive

This paper presents a single-stage solution for PV fed three-phase induction motor (IM) water pumping system. The given solution uses time tested, two two-level cascaded H-bridge inverters to give three-level voltage output to the IM pump drive. The proposed system is operated using the control strategy which includes Maximum Power Point Tracking (MPPT), Space Vector Pulse Width Modulation (SVPWM) and V/f control. The MPPT algorithm generates the modulation index ‘ma’ which is used to operate the cascaded inverter and generates three-level output voltage under all environmental conditions. This helps in improving the THD of IM phase current, thereby reducing the torque ripple. In addition, the ‘ma’ value is used to define the IM operating frequency. This helps in further improvement in the IM performance. All the details of the proposed system regarding the system modeling along with simulation and experiment results are given in the manuscript. In addition, the comparison of the propsoed solution with the conventional system i.e., two-level inverter connected PV pumping system is presented.