Hollow Defects Research Articles

Large‐wavelength Gaussian deconvolution phase‐contrast computed tomography for THz continuous wave (0.11 THz)

AbstractThis letter was to present an attempt of large‐wavelength Gaussian deconvolution phase‐contrast computed tomography (LW‐GD‐PCCT) for promotion of image quality reconstructed in low‐frequency band of terahertz (THz) spectrum at 0.11 THz. The interaction between the imaging samples and the THz Gaussian beam were formulated firstly in this paper, where the unwrapped phase was extracted specifically to portray the spatial structure distribution of the samples. Additionally, a Gaussian deconvolution was employed for the further reduction of spatial distortions. Moreover, an image reconstruction was carried out with the obtained phase sinograms based on phase‐used inverse Radon transform from the different positions on the sample. For an experimental assessment of the concept of LW‐GD‐PCCT, a single ellipsoid reflector‐based THz Gaussian beam generating system was established and samples such as polystyrene (PS) foam cuboid (Sample 1), and cylinder (Sample 2) with hollow defects (air holes and triangles) were prepared carefully in this work. To experimentally evaluate the performance of the contributing to the structural imaging over soft samples. Two‐dimensional topographies of each sample were reconstructed successfully, and the obtained cross root‐mean‐square error (cross‐RMSE), cross peak signal‐to‐noise ratio (cross‐PSNR), and cross structural similarity (cross‐SSIM) were 151.6451, 26.3225, and 0.9616 for Sample 1 with a high dose of 180 projections respectively, as well as 30.3242, 33.3129, and 0.9711 for Sample 2 with a low dose of 36 projections, respectively. The obtained imaging indicators of this work showed a superiority of imaging quality over those of recent works. Furthermore, the investigation of the bearing capacity has shown promise in enhancing image quality even in low‐dose conditions. The presented results suggest that the unwrapped phase combining with Gaussian deconvolution in low‐frequency band of THz imaging would be useful to improve the reconstructed image quality, potential to highly feasible non‐destructive testing of polymer foam via large wavelength.

In situ study on nucleation mechanism and surface morphology of zinc thiourea sulfate crystals

Different nucleation phenomena and defect formation were observed in scanning experiments on the (100) faces of zinc thiourea sulfate (ZTS) crystals using Atomic Force Microscopy (AFM). It was found that nucleation is easily induced near microcrystals, but two-dimensional nuclei do not appear continuously. Edge dislocation can be preferred for nucleation, but the time of occurrence of two-dimensional nuclei near the surface of the edge dislocation is not the same as the growth rate. When two-dimensional nuclei and dislocations co-exist, the step heights have a significant impact on which growth mechanism ultimately dominates. In addition, the experimental results show that the defects produced on the surface of ZTS crystals mainly include hollow defects, pits and liquid inclusions. The causes of the different defects are discussed. It is found that the height of the step has an important influence on the formation of liquid inclusions and their possible influence on the surface morphology is analysed.

ANALISIS KUALITAS PRODUK PENYAMAKAN KULIT DENGAN METODE SQC dan FMEA

PT Adi Satria Abadi is a company engaged in tanning. The problem faced by the company is the presence of defective leather during the goat and sheep tanning production process. From these problems, the purpose of this study was to identify the level of product defects, analyze the factors that cause defects, and make recommendations for improvements to improve the quality of goat and sheep tanning products. Data processing in this study uses the SQC (Statistical Quality Control) and FMEA (Failure Mode and Effect Analysis) methods. Based on the identification results, it was found that there were 1,507 holes for holes, 1,066 for thick defects, 1,061 for louse defects, and 1,086 for size defects. The results of the SQC analysis still have uncontrolled data based on the control chart which is on size defects with a total of 1,086 defects, while for hollow defects, too thick defects, and tick defects are under control. The results of the FMEA analysis show that the order of completion with the first priority is spotting bugs with an RPN value of 36. The suggested improvements to the company are by directly selecting raw materials and supervising employees.
 
 Keywords: Quality, Product Defects, Seven Tools, SQC, FMEA.

Role of Hollow Defects in Lattice Phase Separation and Electronic Features in Quasi-One-Dimensional Bi4I4 Crystals

The defects play a crucial role in the determination of the crystal structure and electronic properties of the matter, evoking tremendous interest in the manipulation of defects and exploration of underlying mechanisms. In this work, we applied scanning tunneling microscopy to investigate the influence of the defects on the lattice structure and electronic properties of Bi4I4 crystals. A lattice phase separation in the nanoscale is identified in the vicinity of hollow defects, which is absent in the sample without defects. The scanning tunneling spectroscopy reveals a bandgap around 0.1 eV at the terrace of (001) surface of Bi4I4, which is consistent with the angle-resolved photoemission spectroscopy results and first-principles calculations. The hollow defects modulate the local density of the state, leading to the edge state residing in the gap region. This edge state is regarded as responsible for the varied resistivity in different Bi4I4 samples in previous reports as their densities of the hollow defects are diverse. Our results shed light on the argument over the lattice phase of Bi4I4 at low temperatures as well as the factors determining the electronic properties.

A high-accuracy hollowness inspection system with sensor fusion of ultra-wide-band radar and depth camera

AbstractWith the dangerous and troublesome nature of hollow defects inside building structures, hollowness inspection has always been a challenge in the field of construction quality assessment. Several methods have been proposed for inspecting hollowness inside concrete structures. These methods have shown great advantages compared to manual inspection but still lack autonomy and have several limitations. In this paper, we propose a range-point migration-based non-contact hollowness inspection system with sensor fusion of ultra-wide-band radar and laser-based depth camera to extract both outer surface and inner hollowness information accurately and efficiently. The simulation result evaluates the performance of the system based on the original range-point migration algorithm, and our proposed one and the result of our system show great competitiveness. Several simulation experiments of structures that are very common in reality are carried out to draw more convincing conclusions about the system. At the same time, a set of laboratory-made concrete components were used as experimental objects for the robotic system. Although still accompanied by some problems, these experiments demonstrate the availability of an automated hollow-core detection system.

Characterization of porosity and hollow defects in ceramic objects built by extrusion additive manufacturing

Direct ink writing, or robocasting, is an extrusion additive manufacturing technique for the fabrication of complex ceramic parts. Pores are common defects in post-sintered robocast parts that strongly influence the performance by changing the density, the transport properties, and the mechanical strength. In this work, the porosity (volumetric fraction, size distribution, geometry and topological distribution) of monolithic and 3D-lattice specimens made of hydroxyapatite was comprehensively characterized at multiple length scales through the six most widely used experimental methods for the study of porous materials. These two types of samples embrace the two most common types of additive manufactured ceramics and allowed the study of materials with pores in the submicron scale, as well as materials with a bimodal pore size distribution at significantly different length scales. Detected pores were divided into (1) engineered porosity set by the structural design, and (2) hollow defects, including intergranular porosity, trapped-air pores, cracks, and cavities, that overlapped at different length scales with the engineered porosity. The origin and mechanisms of formation of hollow defects are discussed, providing guidelines to avoid them. The experimental methods that allow discerning between pores and hollow defects are highlighted, and their advantages and drawbacks are discussed. This work might serve as a guide for the selection of the proper combination of methods for the pore evaluation of similar additive manufactured parts. • Hollow defects in robocast ceramic objects were characterized from the nano to the over micrometric scale. • Image analysis, He pycnometry, N 2 adsorption, MIP, µ-CT, and water saturation were used for characterization. • The types of hollow defects include intergranular porosity, trapped-air pores, cracks, and cavities. • The origin and mechanism of formation of hollow defects is discussed, providing general guidelines to avoid them. • Discussion of the advantages and limits of the methods for the evaluation of materials with a bimodal pore size distribution.

Polarized optical properties of hollowed-out 2D-gold-nanosheets studied using FDTD simulations

Hollowed-out gold-nanosheets (HoGNSs) are one of the special two-dimensional single-crystals on which their bodies (the body of HoGNS, abbreviated as NS-body) contain one or more hollow defects. There are many shape combinations of the outside NS-body and inside hollow-cavity [e.g., Triangle–Triangle (T–T), Hexagon–Triangle (H–T), etc.]. HoGNSs, especially the large-scaled ones, were found to have potential applications in remote surface-enhanced Raman scattering. However, owing to the anisotropy of the hollowed-out structure, the optical properties of different HoGNSs are closely related to the polarization of the incident wave and also to the relative orientations of the paired outer-NS-body and inner-hollow-cavity. Thus, the polarized optical properties of HoGNSs have been studied using finite-difference time-domain (FDTD) simulations. The local electric field near the vertex of the hollow-cavity will be affected by the size, the relative orientation, and the number of sides of the outer-NS-body. There are two different kinds of mechanisms for surface plasmon resonance,-that is, the excitation by the evanescent wave mainly concentrated on the surface of the outer-NS-body and the total internal reflection of the trapped wave between every two adjacent sides of the inner-hollow-cavity. The results have shown that there are strong interactions between the outer-NS-body and inner-hollow-cavity (including their size-, structure-, and orientation-interactions), which suggested that the optical properties of 2D-GNSs were influenced by many parameters but the best and optimum could be derived from FDTD simulations.

Proposed Improvement Product of Cake Pan Using The Six Sigma Method Approach (Case Study of PT. X)

PT. X is a manufacturing company that produces several cookware including Cake Pan. The total number of defects in Cake Pan for 3 months increased by a percentage of 0.384% of the total production of Cake Pan. The purpose of this study using the Six Sigma method is to identify and analyze proposals that can be given to control product quality in order to reduce defective products through the Six Sigma approach. This study found that the capability and sigma value of company performance in improving product quality amounted to 930.68 DPMO with a sigma value of 4.6. Based on the cause and effect diagram FMEA known causes of product defects are color defects, spiral defects, dent defects and hollow defects. Based on the results of the calculation of the RPN to determine the most critical and urgent focus priorities to be addressed, namely the quality of raw materials is not good to be the highest RPN value of 288 with a high severity level of 8. The proposals that can be given are in the form of worker SOPs and checking tables in the form of a system 5s. This research is expected to be useful for companies in providing input as well as an overview in the form of information to PT. X in giving more attention to product quality with several supporting factors that affect the quality of the product.

Novel Polarization Splitter Based on Highly Birefringent Dual-core Photonic Crystal Fibers with Hollow Ring Defects

Novel Polarization Splitter Based on Highly Birefringent Dual-core Photonic Crystal Fibers with Hollow Ring Defects

Design of Photonic Crystal Fibers Based Polarization Splitter with Hollow Ring Defects

A novel photonic crystal fibers (PCFs) based polarization splitter is proposed in this paper. It is designed by highly birefringent dual-core PCFs which hollow ring defects are used in its one direction to break the structural symmetry. Compared to the previous methods achieving high birefringence, this new type of PCFs can partly overcome the design and fabrication limitations for the PCF-based polarization splitter. Its transmission properties, coupling lengths for the two orthogonal polarizations and the performance of the proposed polarization splitter are investigated respectively. The results show that a 0.676-mm-long polarization splitter can be obtained. When the splitting ratio is better than -15dB, its bandwidth is about 45.8nm.

First-principles study of hydrogen and fluorine intercalation into graphene-SiC(0001) interface

The properties of epitaxial graphene on SiC substrates can be modified by intercalation of different atomic species. In this work, mechanisms of hydrogen intercalation into the graphene-SiC(0001) interface, and properties of hydrogen and fluorine intercalated structures have been studied with the use of density functional theory. Our calculations show that the intercalation of hydrogen and fluorine into the interface is energetically favorable. Energy barriers for diffusion of atomic and molecular hydrogen through the interface graphene layer with no defects and graphene layers containing Stone-Wales defect or two- and four-vacancy clusters have been calculated. It is argued that diffusion of hydrogen towards the SiC surface occurs through the hollow defects in the interface graphene layer. It is further shown that hydrogen easily migrates between the graphene layer and the SiC substrate and passivates the surface Si bonds, thus causing the graphene layer decoupling. According to the band structure calculations the graphene layer decoupled from the SiC(0001) surface by hydrogen intercalation is undoped, while that obtained by the fluorine intercalation is $p$-type doped.

Dispersion control in square lattice photonic crystal fiber using hollow ring defects

We propose a new dispersion control scheme by introducing hollow ring defects having a central air hole and a GeO2-or F-doped silica ring with in a square lattice photonic crystal fiber. We confirmed the flexible dispersion controllability in the proposed structure in two aspects of dispersion managements: ultra-flattened near-zero dispersion in the 530 nm-bandwidth over all communication bands and dispersion compensation in C, L, and U band with a high compensation ratio of 0.96~1.0 in reference to the standard single mode fiber. The proposed SLPCFs were also estimated to have an inherently low splice loss due to the index contrast between the doped-ring and silica that kept a good guidance even along with collapsed air holes, which cannot be achieved in conventional PCFs.

Characterization of Cu Reflows on Ru

As compared to conventional Cu reflows on Ta, lower temperature reflow anneals of Cu on Ru are achieved. Cu films are reflowed into 40-nm-wide features at an optimum temperature of 250°C with a measured activation energy of 0.8 eV. Although higher anneal temperatures can shorten the process time, they also tend to increase hollow metal defects (missing Cu within patterned features). Compared to the control electroplated samples, the reflow-annealed samples do not show bigger Cu grains in the final structure. The observed resistance reduction from the reflowed samples is attributed to higher purity within the Cu interconnects.

Effects of Locations of Adhesive Hollows on Interfacial Stress

Fiber Reinforced Polymer (FRP) has been effectively used for strengthening concrete beams. In this study, nonlinear finite element (FE) model of the beam strengthened with CFRP is established to analyze the debonding failure caused by the adhesive hollow defects. The constitutive relationship of the adhesive layer in the FE models is similar to Monti’s bi-linear mode. Three different locations of the hollows are considered in the FE models. The principal stresses in the concrete, the debonding stresses in the adhesive and the stress in CFRP are calculated. The results show that the effect of the locations of the hollow is marginal on the principal stresses in the concrete. When the hollow appears close to the interfacial end, the debonding stresses in the adhesive and the shear stress in the CFRP are significant, which easily causes the debonding failure.

A Study of Hollow Defects in 1st Transfer Process

A Study of Hollow Defects in 1st Transfer Process

Examination of Focused-Ion-Beam Repair Resolution for UV-Nanoimprint Templates

UV-nanoimprint lithography (NIL) has the potentiality to enable fabrication of nanostructures with high-throughput and low cost. The template is a key element in UV-NIL. Template patterns are directly transferred into the replicated materials. A repair technique is indispensable for UV-NIL template fabrication. However, only a few reports have appeared on the repair of UV-NIL templates. In this study, program protrusion and hollow defects on UV-NIL templates have been repaired by focused-ion-beam (FIB) etching and SiOx chemical vapor deposition (CVD) using tetraethoxysilane as a source gas. The imprinted line patterns were successfully replicated by UV-NIL using the repaired templates. Moreover, it has been confirmed that FIB etching and CVD can be applied to repair 30-nm defects on quartz templates.

Optoacoustic diagnostics of absorbing media

We have calculated the intensities of ultrasonic waves excited by counter-propagating light waves of different frequencies and scattered by spherical defects in absorbing isotropic media. We have analyzed the intensity of the scattered sound as a function of the scattering angle and the position of the defect relative to the entry face of the acoustic waveguide. We have shown that for hollow spherical defects, the intensity of the scattered sound tends toward zero for scattering angles close to 90o, and for significantly smaller angles for dense inclusions.

Effect of precursors stoichiometry on morphology, crystallinity and electrical properties of ZnTe epilayers grown on (100)GaAs by MOVPE

AbstractThe effect of precursors vapour stoichiometry on the morphological, structural and electrical properties of nominally undoped ZnTe grown on (100)GaAs by metalorganic vapour phase epitaxy is reported. The epilayers were grown at 350 °C using dimethylzinc (Me2Zn) and di‐isopropyltelluride, varying their molar flow rate ratios (MFRs) between 0.17 and 3.10. Growth in nearly stoichiometric (MFR = 1.03) conditions results in best surface morphology, while samples grown in Te‐rich conditions (MFR > 1.7) showed micron‐size hollow defects (with surface densities up to ∼106 cm–2) elongated in one of the 〈011〉 in‐plane directions. The defects are associated to a local structural disorder of the material, ascribed to the formation of a Ga2Te3 extrinsic phase at the ZnTe/GaAs interface. Ohmic contacts to p ‐ZnTe epilayers were prepared by tungsten evaporation and annealing at 350 °C. The RT hole concentration in the epilayers varies almost linearly with Me2Zn molar flow between 2 × 1015 cm–3 and 5 × 1016 cm–3. Temperature‐dependent Hall measurements performed on samples grown at MFR ≤ 1.03 demonstrate that the material p‐type conductivity originates from a single acceptor centre with an ionisation energy between 94.7 meV and 118 meV, its concentration being in the 1016 cm–3 range and slowly increasing with Me2Zn flow. We ascribe this acceptor to a complex formed by a substitutional carbon atom on a Te site and a donor on a nearest neighbor site (CTe‐DZn), the donor impurity being further identified as Ga diffusing from the substrate. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Reduction of Hollow Defects in 6H-SiC Single Crystals Grown by Sublimation Boule Growth Technique on (1120) 6H-SiC Substrates

Sublimation boule growth of 6H-SiC on (1120) 6H-SiC substrates was investigated. Hollow defects were generated in the crystals grown on (1120) substrates, and they penetrated along the growth direction to the as-grown surface. A new growth model of SiC on (1120) SiC substrates that distinguishes between two-dimensional growth and three-dimensional growth is proposed. The generation of both the stacking faults and the hollow defects on (1120) substrates was attributable to the three-dimensional growth. The growth conditions were modified and applied to suppress the generation of hollow defects. These conditions included the reduction of the growth temperature in the initial stage of the growth, and the increase of the nitrogen concentration in the vapor phase. Due to the changes in the growth conditions, the density of the hollow defects on (1120) substrates was reduced by one order of magnitude to approximately 103 cm-2. An atomically flat as-grown surface was obtained by the sublimation boule growth technique in nitrogen ambient.

Dislocation constraint by etch back process of seed crystal in the SiC sublimation growth

Dislocation constraint in the growth of SiC crystal by the modified Lely method was studied. In SiC single crystal growth, the dislocations and defects generally propagate from the seed crystal surface. However, when the etch back on the seed crystal surface in the sublimation process was performed prior to growth, defects and dislocation propagation in the interface between the seed crystal and the grown crystal were suppressed reasonably. The switchover from the etch back to the growth could be performed without changing heating condition during the initial process. We noticed that the density of the hollow defects called as micropipes in the grown crystal were decreased to 1 10 compared to that of the seed crystal used. We consider the etch back process of the seed crystal as an effective method for constraining the defects in the SiC crystal growth.