Search Results (7)

With the rise of smart manufacturing, defect detection in small-size liquid crystal display (LCD) screens has become essential for ensuring product quality. Traditional manual inspection is inefficient and labor-intensive, making it unsuitable for modern automated production. Although machine vision techniques offer improved efficiency, the lack of high-quality defect datasets limits their performance. To overcome this, we propose a symmetry-aware generative framework, the Squeeze-and-Excitation Wasserstein GAN with Gradient Penalty and Visual Geometry Group(VGG)-based perceptual loss (SWG-VGG), for realistic defect image synthesis.By leveraging the symmetry of feature channels through attention mechanisms and perceptual consistency, the model generates high-fidelity defect images that align with real-world structural patterns. Evaluation using the You Only Look Once version 8(YOLOv8) detection model shows that the synthetic dataset improves mAP@0.5 to 0.976—an increase of 10.5% over real-data-only training. Further assessment using Peak Signal-to-Noise Ratio (PSNR), Structural Similarity Index Measure (SSIM), Root Mean Square Error (RMSE), and Content Similarity (CS) confirms the visual and structural quality of the generated images.This symmetry-guided method provides an effective solution for defect data augmentation and aligns closely with Symmetry’s emphasis on structured pattern generation in intelligent vision systems. Full article

The mechanical properties of PBT-based azide propellants, composed of a 3,3′-bis(azidomethyl)oxetane/tetrahydrofuran (PBT) copolymer matrix and defective ammonium perchlorate (AP) crystals, are significantly influenced by the matrix–crystal interface. This study employed molecular dynamics (MD) simulations to examine interfacial effects on mechanical performance under uniaxial tensile deformation. Models with varying cross-linking densities (70%, 80%, 90%) and AP defect widths (20 Å, 30 Å, 40 Å) were analyzed to assess the effects of temperature, strain rate, cross-linking degree, and defect size on interfacial adhesion strength and failure mechanisms. Results indicate that at low temperatures, the interface exhibited high stress peaks and brittleness characteristics, transitioning to plastic flow and enhanced ductility at higher temperatures. Cross-linking density significantly affects interfacial strength: a 90% cross-linking degree achieved the highest stress peak and optimal tensile resistance, whereas lower cross-linking resulted in weaker stress transfer and accelerated post-peak stress decay. Higher strain rates increased peak stress and shortened deformation times, while lower strain rates promoted molecular rearrangement, enhancing tensile resistance. Defect size also plays a crucial role, with smaller defects maintaining interfacial dominance, whereas larger defects shift failure toward the bulk matrix, reducing stress transfer efficiency. These findings provide atomic-scale insights into interfacial defects and key material parameters, offering theoretical guidance for optimizing the structural stability of composite propellants. Full article

A GaN layer with a thickness of 2 µm was grown on a sapphire substrate using atmospheric pressure metal–organic chemical vapor deposition (AP-MOCVD). Subsequently, the layer was annealed under a nitrogen atmosphere at temperatures ranging from 1000 °C to 1120 °C. High-resolution X-ray diffraction (HRXRD) analysis reveals the impact of thermal annealing on the mosaic structure of the GaN, specifically the tilt and twist variations in four planes: (00.2), (10.3), (10.2), and (10.1). Interestingly, the observed trends suggest a differential effect of annealing on screw and edge dislocation densities. The annealing process reduces the edge and screw dislocation density. Lower values (D_screw = 1.2 × 10⁸ cm⁻²; D_edge = 1.6 × 10⁹ cm⁻²) were obtained for the sample annealed at 1050 °C. Notably, both tilt and twist angles exhibited a minimum at 1050 °C (tilt = 252 arcsecs, and twist = 558 arcsecs), indicating improved crystal quality at this specific temperature. Photoluminescence (PL) spectroscopy further complemented the structural analysis. The intensity and broadening of the yellow band (YL) in the PL spectra progressively increased with the increasing annealing temperature, suggesting the presence of additional defect states. The near band edge PL emission (3.35 and 3.41 eV) variation upon thermal annealing was correlated with the mosaic structure evolution. Full article

The refractive index change obtained after annealed proton exchange (APE) in lithium niobate (LiNbO₃) crystals depends on both the proton exchange process carried out in hot acid and the structure of the crystals. In devices produced by the APE method, dislocations and lattice defects within the crystal structure are considered to be primary contributors to refractive index discontinuities and waveguide instability. In this study, the effects of pre-annealing LiNbO₃ crystals at 500 °C on multifunctional integrated optical chips (MIOCs) were investigated through interferometric fiber-optic gyroscope (IFOG) system-level tests. It was observed that the pre-annealing process resulted in an improvement in the optical throughput of MIOCs (from %34 to %51) and the temperature-dependent bias drift stability of the IFOG (from 0.031–0.038°/h to 0.012–0.019°/h). The angle random walk (ARW) was measured as 0.0056 deg/√h. Full article

Laser Powder Bed Fusion (LPBF) technology exhibits significant advantages in the manufacturing of components with high dimensional accuracy and intricate internal cavities. However, due to the inherent room-temperature brittleness and high-temperature gradient induced by the laser forming process, the LPBF fabrication of γ-TiAl alloy is often accompanied by the initiation and propagation of defects. The aim of this study is to investigate the forming process of γ-TiAl alloy by the LPBF method through molecular dynamics simulation, and to explain the microparticle arrangement and displacement evolution of the melting and crystallization processes, thus elucidating the link between the variations in the laser process parameters and defect generation during microscopic laser heating. The results show that during the melting process, the peaks of the radial distribution function (RDF) decrease rapidly or even disappear due to laser heating, and the atomic disorder is increased. Although subsequent cooling crystallization reorders the atomic arrangement, the peak value of the RDF after crystallization is still 19.3% lower than that of the original structure. By setting different laser powers (200–800 eV/ps) and scanning speeds (0.2–0.8 Å/ps), the effects of various process parameters on microforming and defect evolution are clarified. When the laser power increases from 200 to 400 eV/ps, the stable value of atomic displacement rises from 6.66 to 320.87, while it rises from 300.54 to 550.14 when the scanning speed is attenuated from 0.8 to 0.4 Å/ps, which indicates that, compared with the scanning speed, the atomic mean-square displacements are relatively more sensitive to the fluctuation of laser power. Dislocation analysis reveals that a higher laser power significantly increases the cooling rate during the forming process, which further aggravates the generation and expansion of dislocation defects. Full article

The present work deals with a 10 × 10 array of (Lu_0.7Y_0.3)AP:Ce 2 × 2 × 10 mm³ pixels, manufactured by Crytur (Cz), that has been utilized in a previous paper. The crystal-array has been coupled to an 8 × 8 anodes H10966 model Hamamatsu (Jp) Position-Sensitive Photo Multiplier Tube (PSPMT) connected to electronics for single events scintillation read-out. The response of such a detector has been studied under Co-57, or Ba-133, or Cs-137 gamma-ray emissions, as well as with Lu-176 self-activity only. The present work is aimed at characterizing the individual crystal-pixels’ single-event responses in terms of pulse-height and of spreads of the 2-D charge-distributions. In particular, the charge-spread characterization pointed out several defects in the crystal-array assembly, not detected by usual pulse-height studies. The diagnostic method based on charge-spread analysis seems also well suited for scintillation array characterizations for gamma-ray detectors studies, as well as for quality controls of such pixelated devices during the lifetime of systems in the field of radionuclide medical imaging (SPECT and PET). The method is also appropriate for other applications where gamma-ray spectroscopy is required, like nuclear physics, astrophysics, astroparticle physics, homeland security, and non-proliferation. Full article

Carbonate apatite (CO₃Ap) block, which is a bone replacement used to repair defects, was fabricated through a dissolution–precipitation reaction using a calcium hydrogen phosphate dihydrate (DCPD) block as a precursor. When the DCPD block was immersed in NaHCO₃ or Na₂CO₃ solution at 80 °C, DCPD converted to CO₃Ap within 3 days. β-Tricalcium phosphate was formed as an intermediate phase, and it was completely converted to CO₃Ap within 2 weeks when the DCPD block was immersed in Na₂CO₃ solution. Although the crystal structures of the DCPD and CO₃Ap blocks were different, the macroscopic structure was maintained during the compositional transformation through the dissolution–precipitation reaction. CO₃Ap block fabricated in NaHCO₃ or Na₂CO₃ solution contained 12.9 and 15.8 wt % carbonate, respectively. The diametral tensile strength of the CO₃Ap block was 2 MPa, and the porosity was approximately 57% regardless of the carbonate solution. DCPD is a useful precursor for the fabrication of CO₃Ap block. Full article