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- 2019
- low-temperature electronics
- class AB operation
- optimization of analog electronic circuit
- operational amplifier
- LTspice environment
- buffer amplifier
- junction field-effect transistors
- Electronic Science and Technology
- Don State Technical University
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Optimization of Residual Stresses in Laser-Mixed WC(Co, Ni) Coatings
摘要： A ternary mixture of tungsten carbide (WC), cobalt (Co), and nickel (Ni) powders is prepared to form ceramic-metal composite coatings employed for laser cladding of 40Cr steel. This coating is investigated using the mixture design to evaluate the influence of its ratios on the residual stresses in the clads. The WC/Co/Ni ternary mixture exhibits higher residual stresses than those of the Co/Ni or WC/Ni binary mixtures, except for the WC/Co one. Single WC, Co, or Ni designs illustrate a high sensitivity of residual stresses, cracks pass through the interior of WC particles rather than around them, and the cracks mostly propagate along the eutectic phases at 50%Co–50%WC. A reduced special quartic model in the mixture design exhibits excellent fit, predicted and experimental values of residual stresses for these laser clads are in good agreement.
关键词： residual stress optimization,mixture,reduced special quartic model,tungsten carbide
更新于2025-11-28 14:24:20
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Color Reproduction Accuracy Promotion of 3D-Printed Surfaces Based on Microscopic Image Analysis
摘要： Full-color 3D printing technology is a powerful process to manufacture intelligent customized colorful objects with improved surface qualities; however, poor surface color optimization methods are the main impeding factors for its commercialization. As such, the paper explored the correlation between microstructure and color reproduction, then an assessment and prediction method of color optimization based on microscopic image analysis was proposed. The experimental models were divided into 24-color plates and 4-color cubes printed by ProJet 860 3D printer, then impregnated according to preset parameters, at last measured by a spectrophotometer and observed using both a digital microscope and a scanning electron microscope. The results revealed that the samples manifested higher saturation and smaller chromatic aberration (ΔE) after post-processing. Moreover, the brightness of the same color surface increased with the increasing soaked surface roughness. Further, reduction in surface roughness, impregnation into surface pores, and enhancement of coating transparency effectively improved the accuracy of color reproduction, which could be verified by the measured values. Finally, the chromatic aberration caused by positioning errors on different faces of the samples was optimized, and the value of ΔE for a black cube was reduced from 8.12 to 0.82, which is undetectable to human eyes.
关键词： Structural characterisation,Impregnating process,Scanning electron microscope,Image analysis,Color optimization,Full-color printing
更新于2025-11-21 11:18:25
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Dynamically Optimized Multi-Interface Novel BiSI-Promoted Redox Sites Spatially Separated N-p-n Double Heterojunctions BiSI/MoS2/CdS for Hydrogen Evolution
摘要： Novel BiSI promoted n-p-n double heterojunctions multi-interface photocatalyst BiSI/MoS2/CdS was constructed. BiSI is applied to photocatalytic hydrogen evolution. It possesses a small band gap and a strong optical absorption coefficient, therefore, the optical absorption scope and coefficient of MoS2/CdS have been effectively enhanced by compounding with BiSI. The continuous heterojunctions strengthened the function of single junction and guided the carriers’ transfer direction, thus the redox reactions occur at spatially separated sites. Built-in electric field along the radial direction of BiSI nanorod and MoS2 interlayer helps to transport carriers within lifetime. Carrier dynamics is optimized by multi-interface structure. In general, a new material BiSI is introduced to construct a multi-interface structure to optimize carrier dynamics, which resulted in a 46-fold increase in hydrogen production efficiency.
关键词： multi-interface,dynamics optimization,enhanced optical absorption,photocatalytic water splitting,n-p-n continuous heterojunctions,BiSI
更新于2025-11-14 15:29:11
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Optimization of a parallel-plate RF probe for high resolution thin film imaging
摘要： Choosing an MR probe with the correct dimensions and high sensitivity is critical for magnetic resonance imaging, especially high resolution thin film imaging. In this work, a parallel‐plate resonator has been optimized for strength and uniformity of the B1 magnetic field. The parallel‐plate resonator is designed for high resolution imaging in the direction perpendicular to the plates. The optimization process was undertaken through simulation with CST Micro Wave Studio, followed by experiment. A 400 μm capillary tube, filled with doped water, was used for testing the optimized probe in a 2.4 T magnet. It is shown that increasing the width of the copper leads connected to the plates increases the homogeneity of the B1 magnetic field by almost 90%. The best approach to increase the sensitivity and the homogeneity of the probe was to maintain the dimensions of the plates and copper leads but to add additional capacitors at the corners to distribute the current. This approach produces a 40% stronger B1 magnetic field and increases the homogeneity by almost 85%. The experimental B1 magnetic field of the parallel‐plate prototype agrees within 20% of the value found through simulation, for specified power. The experimental MRI results show that it is possible to achieve a nominal resolution of 10 μm between the plates for suitable samples using the optimized probe. The optimized parallel‐plate resonator, combined with a phase encode SE SPI method, may be used for high resolution studies of lithium‐ion transport in the electrolyte solution of lithium‐ion batteries.
关键词： lithium-ion battery,optimization,MRI,parallel-plate resonator
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe) - Sarajevo, Bosnia and Herzegovina (2018.10.21-2018.10.25)] 2018 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe) - Optimization of Anoff-Grid PV System in Respect to the Capacity Shortage Value
摘要： The main goal of this paper is to describe optimization of off-grid PV system in respect to the capacity shortage value remote area in Osijek. The paper shows a model consisting of PV modules, converter, batteries and electrical load. The examined data are based on measured load values for the residential home. Finding an optimal size of off-grid PV system is shown using HOMER software. The investment costs are presented regarding different values of capacity shortage ranging from 0 % to 10 %. This paper also presents the influence of O&M ranging from 0 % to 3 % on the NPC.
关键词： optimization,O&M,HOMER,off-grid PV,Capacity shortage
更新于2025-09-23 15:23:52
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Computer-Assisted Diagnosis for Diabetic Retinopathy Based on Fundus Images Using Deep Convolutional Neural Network
摘要： Diabetic retinopathy (DR) is a complication of long-standing diabetes, which is hard to detect in its early stage because it only shows a few symptoms. Nowadays, the diagnosis of DR usually requires taking digital fundus images, as well as images using optical coherence tomography (OCT). Since OCT equipment is very expensive, it will benefit both the patients and the ophthalmologists if an accurate diagnosis can be made, based solely on reading digital fundus images. In the paper, we present a novel algorithm based on deep convolutional neural network (DCNN). Unlike the traditional DCNN approach, we replace the commonly used max-pooling layers with fractional max-pooling. Two of these DCNNs with a different number of layers are trained to derive more discriminative features for classification. After combining features from metadata of the image and DCNNs, we train a support vector machine (SVM) classifier to learn the underlying boundary of distributions of each class. For the experiments, we used the publicly available DR detection database provided by Kaggle. We used 34,124 training images and 1,000 validation images to build our model and tested with 53,572 testing images. The proposed DR classifier classifies the stages of DR into five categories, labeled with an integer ranging between zero and four. The experimental results show that the proposed method can achieve a recognition rate up to 86.17%, which is higher than previously reported in the literature. In addition to designing a machine learning algorithm, we also develop an app called 'Deep Retina.' Equipped with a handheld ophthalmoscope, the average person can take fundus images by themselves and obtain an immediate result, calculated by our algorithm. It is beneficial for home care, remote medical care, and self-examination.
关键词： deep convolutional neural network,mobile app,fractional max-pooling,support vector machine,diabetic retinopathy,fundus images,teaching-learning-based optimization
更新于2025-09-23 15:23:52
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Multi-objective optimization of a solar assisted heat pump-driven by hybrid PV
摘要： The role of renewable energy sources becomes more and more important in modern times. Solar energy utilization in the building sector is one attractive solution for covering heating and electricity needs. In this direction, the investigation of a solar heating-electricity production system ideal for building applications is investigated in this study. This cogeneration system includes hybrid PV (or PV/T) collectors and a heat pump which is driven totally (heat and electricity) by the solar collector. The system is designed properly in order to produce net electricity production except for the need of the heat pump. This system is optimized using an innovative multi-objective procedure with heating and electricity production as the objective functions. The optimization is performed in steady-state conditions for seven different working fluids in the heat pumps. The optimum design points for all the working fluids are compared and finally, R32 is selected as the most suitable choice with R1234yf to be the second one. In the optimum design conditions, 10 m2 of hybrid PV collector are able to feed the heat pump and finally 4.33 kWth of heating and 0.53 kWel of net electricity to be produced. The next step in this study is the investigation of the system with R32 for all the winter period in the climate conditions of Athens (Greece). Six different typical days (one for every month from November to April) are examined and the final results are given. For January, which is a representative winter month, it is found that the daily heating and electricity production is 34.9 kWh and 5.13 kWh respectively. Moreover, the mean daily energy efficiency is found 60.53% while the exergy 9.26% for this month.
关键词： Working fluid investigation,Cogeneration,Space heating,Multi-objective optimization,PVT
更新于2025-09-23 15:23:52
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Inverse design and demonstration of broadband grating couplers
摘要： We present a gradient-based optimization strategy to design broadband grating couplers. Using this method, we are able to reach, and often surpass, a user-specified target bandwidth during optimization. The designs produced for 220 nm silicon-on-insulator are capable of achieving 3 dB bandwidths exceeding 100 nm while maintaining central coupling efficiencies ranging from -3.0 dB to -5.4 dB, depending on partial-etch fraction. We fabricate a subset of these structures and experimentally demonstrate gratings with 3 dB bandwidths exceeding 120 nm. This inverse design approach provides a flexible design paradigm, allowing for the creation of broadband grating couplers without requiring constraints on grating geometry.
关键词： inverse design,optimization,broadband,fiber-packaging,grating couplers
更新于2025-09-23 15:23:52
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Online Policies for Energy Harvesting Receivers With Time-Switching Architectures
摘要： In the real-world, it is virtually impossible to have non-causal knowledge of future events. Research in energy harvesting (EH) systems that assumes knowledge of future energy arrivals falls short in terms of practical utility, pointing to the need for online strategies. In addition, the modeling and analysis for EH transmitter and receiver are inherently different. Compared with EH transmitter, EH receiver has received less attention. In this paper, we formulate Markov decision process problems and perform online optimization to maximize the number of bits decoded for an EH receiver with a time-switching architecture, which harvests energy from both a dedicated transmitter and other sources. We consider both infinite and finite horizon scenarios. For the infinite horizon, we provide an upper bound on the average expected reward. Then, we find an optimal policy which can achieve performance arbitrarily close to this bound. For the finite horizon, we first provide a policy obtained from standard backward induction with space quantization. Its performance can be close to optimal online performance as the number of quantization intervals increases, at the cost of relatively high computational complexity. Then, by carefully restricting the state space, we present a computationally efficient policy, which achieves comparatively good performance.
关键词： Infinite horizon,Markov decision process,Energy harvesting,Online optimization,Finite horizon
更新于2025-09-23 15:23:52
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Image quality optimization using a narrow vertical detector dental cone-beam CT
摘要： Objectives: To determine the optimised kV setting for a narrow detector cone-beam CT (CBCT) unit. Methods: Clinical (CL) and quantitative (QUANT) evaluations of image quality were performed using an anthropomorphic phantom. Technical (TECH) evaluation was performed with a polymethyl methacrylate phantom. Images were obtained using a PaX-i3D Green CBCT (Vatech, Hwaseong, Korea) device, with a large 21x19 and a medium 12x9 cm field of view, and high-dose (HD– ranging from 85 to 110 kV) and low-dose (LD– ranging from 75 to 95 kV) protocols, totalling four groups (21x19 cm HD, 21x19 cm LD, 12x9 cm HD, 12x9 cm LD). The radiation dose within each group was fixed by adapting the mA according to a predetermined dose-area product. For CL evaluation, three observers assessed images based on overall quality, sharpness, contrast, artefacts, and noise. For QUANT evaluation, mean grey value shift, % increase of standard deviation (SD), % of beam-hardening and contrast-to-noise ratio (CNR) were calculated. For TECH evaluation, segmentation accuracy, CNR, metal artefact SD, metal object area, and sharpness were measured. Representative parameters were chosen for CL, QUANT and TECH evaluations to determine the optimal kV based on biplot graphs. kV values of the same protocol were compared by bootstrapping approach. The ones that had statistical differences with the best kV were considered as worse quality. Results: Overall, kV values within the same group showed similar quality (p>0.05), except for 110 kV in 21x19 cm HD and 85 kV in 12x9 cm HD of CL score; also 85, 90 kV in 21x19 cm HD and 75, 80 kV in 21x19 cm LD of QUANT score which were worse (p<0.05). Conclusion: At a constant dose, low and high kV protocols yield acceptable image quality for a narrow-detector CBCT unit.
关键词： Image Quality,Computed-assisted image analysis,Phantoms,Imaging,Optimization,Cone-beam computed tomography
更新于2025-09-23 15:23:52