Presence Of Different Defects Research Articles

Quality inspection of specific electronic boards by deep neural networks

Reliability and lifetime of specific electronics boards depends on the quality of manufacturing process. Especially soldering splashes in some areas of PCB (printed circuit board) can cause change of selected electrical parameters. Nowadays, the manual inspection is massively replaced by specialized visual systems checking the presence of different defects. The research carried out in this paper can be considered as industrial (industry requested) application of machine learning in automated object detection. Object of interest—solder splash—is characterized by its small area and similar properties (texture, color) as its surroundings. The aim of our research was to apply state-of-the art algorithms based on deep neural networks for detection such objects in relatively complex electronic board. The research compared seven different object detection models based on you-look-only-once (YOLO) and faster region based convolutional neural network architectures. Results show that our custom trained YOLOv8n detection model with 1.9 million parameters can detect solder splashes with low detection speed 90 ms and 96.6% mean average precision. Based on these results, the use of deep neural networks can be useful for early detection of solder splashes and potentially lead to higher productivity and cost savings.

ZnO-Based Materials: From Pauli’s Nonsense to a Key Enabling Technology

In this work, we aim to highlight the increasing interest in semiconductors, particularly ZnO. A revision of the evolution of the scientific production on three selected topics has been conducted. As an indicator of scientific production, the number of publications indexed in the Web of Science Data Base has been used. The search terms selected range from the general to the particular: semiconductors, oxide semiconductors, and ZnO. The period considered is from 1 January 1900 to 6 June 2023. The importance of doping processes in tailoring the properties of these materials, and the relevance of the most recently derived applications are also revised. Since many of the most recent applications that have been developed or are under development refer to optoelecronic properties, doping with rare earth elements has a central role. This was the reason behind choosing the system ZnO doped with Rare Earth elements (Eu, Gd, and Ce) and codoped with Ru to illustrate the materials’ tuning potential of doping processes. Morphology, crystal structure, and luminescent properties have been investigated. Upon doping, both the Near Band Edge and the Deep Level emissions show a remarkable difference due to the change in the relative weight of the components constituting these bands. The spectra in all cases extend over the whole visible range, with a main emission in the violet-blue region corresponding to the Near Band Edge, and a broad band extending from the blue-green to orange-red region associated with the presence of different defects.

Vibration response and safety control for blasting vibration of the existing tunnel with defects

Current studies on blasting construction of small clear-distance tunnels have not considered the impact of existing tunnel lining defects when establishing safety controls. This paper offers a series of study results based on the blasting project of a new tunnel adjacent to the existing defect Xinling tunnel to thoroughly examine the dynamic response, safety control standards, and measures of the existing defect tunnel. First, structural models were developed to investigate the influence of the presence or absence of specific defects (like lining cracks and cavities behind the lining) on the dynamic response of the current tunnel lining to identify the most unfavorable defect distribution. Then, establish safety control standards for intact linings and those with the most unfavorable defects. Eventually, two types of control measures, single safe charge and reasonable delay time, were studied based on the established safety control standards. In particular, the most adverse position of cracks was the wall facing the explosion, the rise in depth was more unfavorable for vibration response, and the impact of the longitudinal crack was restricted to the vicinity of the crack. While the vault was the most adverse cavity position, the rise in cavity area was more damaging, and the influence range varied with longitudinal cavity length. Moreover, the impact of cracks was mainly evident in the amplification effect of stress at the crack region. In contrast, cavities had varied degrees of amplification effects on the vibration velocity and stress response and a relatively extensive influence range. Safety control research was conducted, when the tunnel was intact, with a right wall crack, a vault cavity, and both vault cavity and crack for this project, the peak particle velocity (PPV) of the safety control standard for vibration velocity was 13, 10, 13, and 8 cm/s, respectively, and the respective single safe charge could be adjusted at 64, 53, 37, and 25 kg. However, the presence of different defects had a relatively negligible effect on the reasonable delay time; 25 ms was recommended for existing tunnel lining with and without the defect.

Machine learning sparse tight-binding parameters for defects

We employ machine learning to derive tight-binding parametrizations for the electronic structure of defects. We test several machine learning methods that map the atomic and electronic structure of a defect onto a sparse tight-binding parameterization. Since Multi-layer perceptrons (i.e., feed-forward neural networks) perform best we adopt them for our further investigations. We demonstrate the accuracy of our parameterizations for a range of important electronic structure properties such as band structure, local density of states, transport and level spacing simulations for two common defects in single layer graphene. Our machine learning approach achieves results comparable to maximally localized Wannier functions (i.e., DFT accuracy) without prior knowledge about the electronic structure of the defects while also allowing for a reduced interaction range which substantially reduces calculation time. It is general and can be applied to a wide range of other materials, enabling accurate large-scale simulations of material properties in the presence of different defects.

Effect of the Root Gap on the Structure and Properties of High Strength Steel S700MC Welds

Nowadays, the use of high strength (HS) and ultra-high strength steels (UHS) increases, notably in welded constructions. These steels are mainly exploited in heavy loaded welded constructions such as bridges, cranes and excavators, in pressure vessels, vehicles, ships, drilling rigs etc. working at room or lower temperatures. As the welded constructions have specific requirements, the development of high strength and ultra-high strength steels imposes the need for research on the factors influencing their weldability. Among the possible negative implications are: cold cracks formation, softening of the heat affected zone, brittleness in the coarse grained zone. When complying with the generally accepted rules for welding, HS and UHS are readily welded by all conventional welding methods. Recommendations for welding of steels after normalization, thermo-mechanical treatment and quenching and tempering are given in the standard EN 1011 -1, 2. The use of thermo-mechanically treated (hot-rolled) steels with low carbon equivalent, such as S700MC, allows reduction in time required for welding as the preheating temperature is lowered or even preheating is not necessary. A more pronounced negative effect on the weld quality has the presence of different defects. S700MC can be welded by all conventional methods, and a reduction in the softened zone can be achieved by using appropriate welding parameters. Joint preparation for welding of HS and UHS steels is described in the standards EN ISO 9692-1:2013 and EN ISO 9692-2:2001. Nevertheless, the root gap is often the closing part in constructions and does not comply with the standard recommendations. That is why the effect of the root gap on welds has to be researched. The present work introduces results of a research studying the effect of the root gap on the structure and some mechanical and technological properties of S700MS welds, welded by submerged arc welding.

Formation of health culture of student youth

In students ' years there is active intellectual, physical development and socialization of the person. It is known that in Ukraine among the students there is a tendency to the growth of various diseases, deterioration of functional reserves of the body, the presence of different defects of the musculoskeletal system, reducing the level of physical preparedness and the like.
 In the process of analyzing scientific researches and publications, it is determined that different authors pay close attention to the problem of preserving and strengthening the health of modern students, the formation of a culture of health, the creation of health saving educational environment in higher education institutions. The common opinion of researchers is that the need for health should integrate in the cultural need and become a norm of personality life.
 The main purpose of this work is analysis and synthesis of scientific sources and results of researches of individual authors on the problem of formation of a culture of students ' health.
 Theoretical comprehension of this problem gave an opportunity to define the essence and content of culture of health as a whole and for students. According to this we believe that physical education is a powerful mechanism of forming a culture of students ' health. In our opinion, an integral part of the formation of students ' health culture is the use of different types and forms of motive activity for active recreation, health and fitness classes and physical recreation in compliance with recommendations on the duration and intensity of motor activity during the week, as well as the requirements to physical condition, a healthy lifestyle.
 Prospects for further development see in a more in-depth analysis of the formation of health culture of students of different specialties.

Electrical and optical properties in O-polar and Zn-polar ZnO films grown by pulsed laser deposition

O-polar and Zn-polar ZnO films were grown on c-sapphire by pulsed laser deposition. Positron annihilation spectroscopy study reveals that the VZn-related defects in the ZnO films with different polarities are different in structure and their thermal evolution is different. Hall effect measurement and luminescence spectroscopy reveal that the electrical and optical properties and their corresponding thermal evolution are strongly dependent on the polarity of the film. The luminescence spectra of the as-grown Zn-polar ZnO film is signified by a negligible green defect emission (at ~ 2.4 eV) and strong near band edge emission as compared with the O-polar film. The as-grown Zn-polar film exhibited a lower electron concentration (2 × 1018 cm−3) than that of the O-polar film (6 × 1018 cm−3); this difference is attributed to their different H concentrations. For the O-polar film, the electron concentration decreased with annealing temperature Tanneal, reaching a minimum at 700°C and then increased to 4 × 1018 cm−3 at Tanneal = 900 °C. In comparison, the electron concentration of the Zn-polar ZnO film monotonically decreased with Tanneal attaining a value of ~1 × 1017 cm−3 at Tanneal = 900 °C, 40 times smaller than that of the O-polar film. The cause for the differences in the optical and electrical properties for the O-polar and Zn-polar films is explained by the presence of different defects in these films.

Model Development for Nanosecond Laser-Induced Damage Caused by Manufacturing-Induced Defects on Potassium Dihydrogen Phosphate Crystals.

Nanosecond laser-induced damage on (potassium dihydrogen phosphate) KDP crystals is a complex process, which involves coupled actions of multi-physics fields. However, the mechanisms governing the laser damage behaviors have not been fully understood and there have been no available models to accurately describe this complex process. In this work, based on the theories of electromagnetic, thermodynamic, and hydrodynamic fields, a coupled multi-physics model is developed to describe the transient behavior of laser-supported energy deposition and diffusion accompanied by the surface defect (e.g., surface cracks)-initiated laser damage process. It is found that the light intensification caused by the defects near the crystal surface plays a significant role in triggering the laser-induced damage, and a large amount of energy is quickly deposited via the light intensity-activated nonlinear excitation. Using the developed model, the maximum temperature of the crystal material irradiated by a 3 ns pulse laser is calculated, which agrees well with previously reported experimental results. Furthermore, the modeling results suggest that physical processes such as material melting, boiling, and flowing have effects on the evolution of the laser damage process. In addition, the experimentally measured morphology of laser damage sites exhibits damage features of boiling cores, molten regions, and fracture zones, which are direct evidence of bowl-shaped high-temperature expansion predicted by the model. These results well validate that the proposed coupled multi-physics model is competent to describe the dynamic behaviors of laser damage, which can serve as a powerful tool to understand the general mechanisms of laser interactions with KDP optical crystals in the presence of different defects.

Study of MgCl2 activation treatment on the defects of CdTe solar cells by capacitance-voltage, drive level capacitance profiling and admittance spectroscopy techniques

CdTe solar cells have recently reached its highest conversion efficiencies, comparable to CuInGaSe2 and Si devices. One of the key factors for the success of these devices is the so-called “activation” treatment, which typically consists in depositing a CdCl2 film on the CdTe absorber layer and in a subsequent annealing in air or nitrogen atmosphere. Nevertheless CdCl2 is a carcinogenic and water-soluble compound; for this reason recent studies have found MgCl2 as a good alternative.In this work we have studied devices (exceeding 14% efficiency) prepared by low-substrate temperature CdTe deposition and activated with MgCl2 treatment (applied by wet deposition). The devices were characterized by means of current-voltage, capacitance-voltage, drive level capacitance profiling and admittance spectroscopy techniques. Carrier concentration and also concentration and distribution of shallow and deep defects are presented and compared with data obtained from analogous devices but activated with the standard CdCl2. Despite CdTe layers treated with the two different processes exhibit similar structural properties, the distribution of deep and shallow defects results to be different and moreover admittance spectroscopy technique reveals the presence of different defects, at 344 and 358meV, which are present only in MgCl2 treatment case.

Influence of intrinsic and artificial defects on the VHCF properties of 17-4PH stainless steel

In the present work, fatigue test results in the very high cycle fatigue (VHCF) regime are discussed. Experiments were performed with smooth specimens in which crack initiation mostly originated at non-metallic inclusions. Additionally, the influence of small artificial defect, i.e. circumferential notches, drilled holes and corrosion pits, was investigated. Fatigue tests in the VHCF regime were conducted using ultrasonic fatigue testing technique. Further experiments in the high cycle fatigue regime were performed using rotating bending and servo-hydraulic testing machines.For smooth specimens, fatigue fracture was observed even at more than 1010 number of cycles. In contrast, no fatigue failure occurred above approximately 107 cycles in the presence of artificial defects, i.e., a pronounced fatigue limit was determined. Furthermore, it was found that the fatigue limit is not only depending on the defect size but also on the notch root radius of a defect. Consequently, different approaches were used to predict the fatigue limit in the presence of different defects.

Requirements for the order and the procedure of estimating structural strength characteristics of metal alloys for the main and critical parts of aviation gas turbine engines

Requirements of the technical regulations for the order and procedure of estimating structural strength of metal alloys used in critical and main parts of aviation engines in their certification are outlined in the paper. The scope of work to be carried out by the engine designer, the developer of the material/semi-finished product and the engine manufacturer to confirm the compliance with the mentioned requirements is described. The tasks to be solved at different stages of general and special qualification of the material are discussed. The spectrum of the main mechanical characteristics of alloys, including mono-crystal alloys, to be determined during the qualification tests is presented. The standards in accordance to which the tests are to be performed are mentioned. Relationships for the determination of the material characteristics to be used in estimating the strength and service life of engine parts are given. The requirements for the statistical processing of the results of investigating the structural strength of alloys are discussed, as well as the requirements for setting the values of the mechanical properties guaranteed in the delivery of materials/semi-finished products. The necessity to have data on possible presence of different defects in the main (critical for safe operation) engine parts is mentioned. The reference list includes principal technical regulations the requirements of which are to be met during special qualification of alloys used for the manufacture of the main and critical aviation engine parts.

Requirements for the order and the procedure of estimating structural strength characteristics of metal alloys for the main and critical parts of aviation gas turbine engines

Requirements of the technical regulations for the order and procedure of estimating structural strength of metal alloys used in critical and main parts of aviation engines in their certification are outlined in the paper. The scope of work to be carried out by the engine designer, the developer of the material/semi-finished product and the engine manufacturer to confirm the compliance with the mentioned requirements is described. The tasks to be solved at different stages of general and special qualification of the material are discussed. The spectrum of the main mechanical characteristics of alloys, including mono-crystal alloys, to be determined during the qualification tests is presented. The standards in accordance to which the tests are to be performed are mentioned. Relationships for the determination of the material characteristics to be used in estimating the strength and service life of engine parts are given. The requirements for the statistical processing of the results of investigating the structural strength of alloys are discussed, as well as the requirements for setting the values of the mechanical properties guaranteed in the delivery of materials/semi-finished products. The necessity to have data on possible presence of different defects in the main (critical for safe operation) engine parts is mentioned. The reference list includes principal technical regulations the requirements of which are to be met during special qualification of alloys used for the manufacture of the main and critical aviation engine parts.

Structural, morphological and optical studies of ripple-structured ZnO thin films

Ripple-structured ZnO thin films were prepared on Si (100) substrate by sol–gel spin-coating method with different heating rates during preheating process and finally sintered at 500 °C for 2 h in ambient condition. The structural, morphological and photoluminescence (PL) properties of the nanostructured films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and PL spectroscopy. XRD analysis revealed that films have hexagonal wurtzite structure and texture coefficient increases along (002) plane with preheating rate. The faster heating rate produced higher crystallization and larger average crystallite size. The AFM and SEM images indicate that all the films have uniformly distributed ripple structure with skeletal branches. The number of ripples increases, while the rms roughness, amplitude and correlation length of the ripple structure decrease with preheating rates. The PL spectra show the presence of different defects in the structure. The ultraviolet emission improved with the heating rate which indicates its better crystallinity.

Ultra-long multicolor belts and unique morphologies of tin-doped zinc oxide nanostructures

We demonstrate the synthesis, characterization and application of pure and tin (Sn) doped zinc oxide (ZnO) nanostructures with unique optical properties. Pencil-shaped nanorods were synthesized using a mixture of pure ZnO and carbon as starting material. The growth mechanism of these nanorods is discussed in detail. Sn-doped ultra-long belt-shape ZnO structures show many different colors in a single belt under fluorescent light in an optical microscope. These different colors are attributed to the presence of different defects in the ZnO lattice. X-ray diffraction and UV–VIS spectroscopy results are in good agreement with each other. A major application for these belts is likely to be in a single-particle sensor. A single belt based UV sensor is also fabricated and the results suggest that these photoconducting belts can serve as highly sensitive UV-light detectors.

Detecting defects in outdoor non-ceramic insulators using near-field microwave non-destructive testing

This paper presents a novel near-field microwave nondestructive testing technique for defect detection in non-ceramic insulators (NCI). In this work, distribution class 33 kV NCI samples with no defects, air voids in silicone rubber, cracks in the fiberglass core and small metallic inclusion between the fiber core and shank were inspected. The microwave inspection system utilizes an open-ended rectangular waveguide sensor operating in the near-field at a frequency of 24 GHz. The used inspection system is simple, safe and relatively inexpensive. A data acquisition system was used to record the measured data. The results showed that all defects were repeatedly detected with high sensitivity. Line scans of the samples were obtained revealing the presence of different defects and their location. The technique also demonstrated ability to detect thickness variations in the silicon rubber shank.

Corrosion of sputtered titanium nitride films deposited on iron and stainless steel

TiN coatings were deposited by reactive sputtering on Armco iron, AISI 430 and AISI 304 substrates. The electrochemical behaviour of the samples was investigated using d.c. and a.c. electrochemical techniques in H 2SO 4 and NaCl solutions. Scanning electron microscopy was used to study the microstructure of the TiN coating in cross-section. The electrochemical tests show that the corrosion resistance of these materials is linked to the presence of different defects (pinholes, pores, etc.). An attempt was made to improve the corrosion resistance, first by modifying the sputtering conditions and secondly by the pre-sputtering of a pure titanium underlayer. The effects of these different methods are discussed.

Crystal growth and hysteresis phenomena of rubidium tetrachlorozincate Rb2ZnCl4

Abstract Phase transitions in Rb2ZnCl4 crystals grown by various methods are examined with differential scanning calorimetry and dielectric measurements. For most of the studied samples the permittivity along the ferroelectric axis shows a large thermal hysteresis over a wide temperature range including the incommensurate phase and the lock-in point. This hysteresis depends on the presence of different defects which appear during crystal growth or after a thermal and mechanical treatment. It is shown that dielectric measurements are quite well suited to characterize the crystals exhibiting on incommensurate phase and a ferroelectric phase.