This contribution attempts to model the alteration of the in-plane elastic properties in laminates caused by stitching, and to predict the in-plane effective tensile strength of the stitched composite laminates. The d...This contribution attempts to model the alteration of the in-plane elastic properties in laminates caused by stitching, and to predict the in-plane effective tensile strength of the stitched composite laminates. The distortion of in-plane fibers is considered to be the main cause that affects the in-plane mechanical properties. A fiber distortion model is proposed to characterize the fiber misalignment and the fiber content concentration due to stitching. The undistorted region, the fiber distortion region, the resin-rich pocket and the through-thickness reinforcement section are taken into account. The fiber misalignment and inhomogeneous fiber content due to stitching have been formulated by introducing two parameters, the distortion width and maximum misalignment. It has been found that the ply stress concentration in stitched laminates is influenced by the two concurrent factors, the stitch hole and inhomogeneous fiber content. The stitch hole brings about the stress concentration whereas the higher fiber content at the local region induced by stitching restrains the local deformation of the composite. The model is used to predict the tensile strength of the [0/45/0/-45/90/45/0/-45]58 T300/QY9512 composite laminate stitched by Kevlar 29 yarn with different stitching configurations, showing an acceptable agreement with experimental data.展开更多
A representative volume element method and a novel mesomechanical-based polyline model are proposed to describe the misalignment of in-plane fibers induced by the insertion of stitch thread.A multi-scale mathematical ...A representative volume element method and a novel mesomechanical-based polyline model are proposed to describe the misalignment of in-plane fibers induced by the insertion of stitch thread.A multi-scale mathematical model of in-plane elastic parameters for stitched composite laminate is established with ply-angle and stitch parameters as well as material parameters taken into account.Based on the fabrication of specimens and the verification of experimental platform,the superposition influences of stitch on structural anisotropy are revealed by the developed theoretical model.Results indicate that the stitch orientation can increase the structural anisotropy.The decreases of stitch pitch and spacing as well as the increase of thread diameter obviously reduce the elastic and shear moduli of laminates.Furthermore,the elastic and shear moduli as well as Poisson’s ratios show sinusoidal changes with a period of 90°as the ply-angle increases.The theoretical model not only analyzes the in-plane mechanical properties of stitched laminate with ply-angle,but also lays a foundation for the dynamic studies of stitched sandwich structures with ribs in the future.展开更多
The mechanical properties of silica material in the monolithic form are ;far from acceptable levels. In this paper, 3D stitched quartz preform was used for the fiber reinforcement, and quartz fibers- reinforced silica...The mechanical properties of silica material in the monolithic form are ;far from acceptable levels. In this paper, 3D stitched quartz preform was used for the fiber reinforcement, and quartz fibers- reinforced silica composites were prepared by the silica sol-infiltration-sintering method. The density of the composite was up to 1.71 g/cm3 after 10 infiltration-sintering cycles. The flexural strength and the in-plane shear strength were 61.7 MPa and 20.3 MPa, respectively. The flexural stress-deflection curve exhibited mostly nonlinear behavior, which was different from that of monolithic ceramics. Because of the existence of the fiber in Z axis direction, shearing property between the different layers of 3D stitched composites were greatly enhanced. Toughness effect of the 3D stitched quartz preform was conspicuous. The as-fabricated composites showed non-catastronhic failure behavior resulting from weak fiber/matrix interface.展开更多
The recent advancements in the field of Virtual Reality(VR)and Augmented Reality(AR)have a substantial impact on modern day technology by digitizing each and everything related to human life and open the doors to the ...The recent advancements in the field of Virtual Reality(VR)and Augmented Reality(AR)have a substantial impact on modern day technology by digitizing each and everything related to human life and open the doors to the next generation Software Technology(Soft Tech).VR and AR technology provide astonishing immersive contents with the help of high quality stitched panoramic contents and 360°imagery that widely used in the education,gaming,entertainment,and production sector.The immersive quality of VR and AR contents are greatly dependent on the perceptual quality of panoramic or 360°images,in fact a minor visual distortion can significantly degrade the overall quality.Thus,to ensure the quality of constructed panoramic contents for VR and AR applications,numerous Stitched Image Quality Assessment(SIQA)methods have been proposed to assess the quality of panoramic contents before using in VR and AR.In this survey,we provide a detailed overview of the SIQA literature and exclusively focus on objective SIQA methods presented till date.For better understanding,the objective SIQA methods are classified into two classes namely Full-Reference SIQA and No-Reference SIQA approaches.Each class is further categorized into traditional and deep learning-based methods and examined their performance for SIQA task.Further,we shortlist the publicly available benchmark SIQA datasets and evaluation metrices used for quality assessment of panoramic contents.In last,we highlight the current challenges in this area based on the existing SIQA methods and suggest future research directions that need to be target for further improvement in SIQA domain.展开更多
This paper presents an application of stitched ground plane for microstrip patch antenna design. In this work Matlab interface to computer embroidery techniques were used to implement the felt and denim substrates on ...This paper presents an application of stitched ground plane for microstrip patch antenna design. In this work Matlab interface to computer embroidery techniques were used to implement the felt and denim substrates on microstrip patch antenna. These antennas were simulated using a commercial full 3D electromagnetic CST Microwave Studio 2019. A method to optimize the stitch patterns with conductive thread for antenna ground plane for 2.45 GHz industrial, scientific, and medical (ISM) band and 5 GHz wearable wireless local area networks (WLAN) frequencies was achieved. Rigid and flexible wearable antennas (microstrip patch antennas) were fabricated using the stitched ground plane. The electrical resistance was reduced between the meshes during the stitching design process. Results in terms of bandwidth, radiation patterns and reflection coefficients (S<sub>11</sub>) are presented.展开更多
This work reveals that the addition of periodically distributed stitches to sandwich structure enables a significant reduction of vibration in stop-band and this new functionality is systematically investigated.Firstl...This work reveals that the addition of periodically distributed stitches to sandwich structure enables a significant reduction of vibration in stop-band and this new functionality is systematically investigated.Firstly,a finite element model which is capable of taking into consideration the three layers of the sandwich as well as the stitches is developed.The diagram of dispersion is calculated by applying Floquet-Bloch theorem to the boundaries of unit cell.With properly chosen properties of stitches,a stop-band for flexural wave is observed.This stop-band is further confirmed by the forced response of a large stitched sandwich panel under point excitation.The level of vibration in the stop-band is significantly reduced.The influence of the stitch rigidity and density on upper and lower limits of stop-band is also examined,which confirms that stitched sandwich can be tuned to mitigate vibration in a certain frequency band with appropriate stitch properties.These investigations have demonstrated the potential application of stitched sandwich in the area of vibration reduction.展开更多
This work explores the optimal mesh structure, stitch density and production technique of stitched ground plane for microstrip patch antenna. Meshed ground plane was used as a generic problem. A stitched ground plane ...This work explores the optimal mesh structure, stitch density and production technique of stitched ground plane for microstrip patch antenna. Meshed ground plane was used as a generic problem. A stitched ground plane is pro-posed and designed using Matlab interface to computer embroidery. Using the meshed or stitched ground plane as a case study, the resistance between meshes was analysed and measured. The equivalent resistance between nodes is a function of their distance apart. A finite resistive grid was simulated and compared to measured sets of data. A microstrip patch antenna with stitched ground shows comparable performance to the conventional etched ground of the size in terms of bandwidth. The stitched ground plane has a higher band-width than the etched copper ground plane because of the increased thickness of the substrate. Thus, it can be concluded that the use of the interface method shows the possibilities of controlling the stitch density and distances between mesh nodes. The interface increases the stitching density and reduces the elec-trical resistance between mesh nodes making the antennas flexible and weara-ble. The functionality of these antenna samples has been tested and validated using microstrip patch ground at 2.45 GHz and 5 GHz. Measurement results on the proposed stitched ground planes were compared with the theory of infinite resistive network that shows good agreement.展开更多
Crack growth resistance plays a different role in crashworthiness analysis since the progressive energy absorption is based on controllable fracture mechanisms. In this regard, the present paper studies the efficient ...Crack growth resistance plays a different role in crashworthiness analysis since the progressive energy absorption is based on controllable fracture mechanisms. In this regard, the present paper studies the efficient crack growth resistance in off-axis crushing of composite tubular structures by implementing natural fiber yarns. One of the through-to-thickness reinforcement methods known as stitching has been chosen to influence the axial and off-axis crushing process. Improving the crack growth resistance and appropriate fiber breakage at different stages of crushing process can significantly improve the resistance force and consequently the energy absorption capability of composite absorbers in axial and off-axis crushing. This analysis will be applied to non-stitched and stitched CFRP composite boxes which showed brittle fracture and transverse shearing crushing modes under off-axis loading of 10 degrees. The analytical methods are also implemented to analysze the effect of various failure mechanisms such as bending, friction, bundle fracture, and interlaminar crack growth for the observed crushing modes. The proposed model is able to predict the crushing load and crush force efficiency in close agreement from experimental studies.展开更多
Low-velocity impact damage known as“imperceptible”damage usually destroys the structural integrity of the material and seriously affects the service life of the materials.To improve the low-velocity impact resistanc...Low-velocity impact damage known as“imperceptible”damage usually destroys the structural integrity of the material and seriously affects the service life of the materials.To improve the low-velocity impact resistance of foam sandwich composites,an innovative concept of a stitched multi-layer sandwich structure by organically combining the discrete splitting of foam layer with full thickness stitching was proposed,and its low-velocity impact resistance obtained through drop-hammer impact tests was explored.The results showed that the multi-layer foam sandwich structure acted as a stress disperser and reduced the irreversible impact damage.The depth and area of low-velocity impact damage of multi-layer foam sandwich composites gradually decreased with increasing the number of the layers.The stitched structure would improve the integrity of the foam sandwich composites and inhibit the propagation of cracks.The maximum impact load of the stitched foam sandwich composite increased by approximately 5% compared with that of the non-stitched material.In addition,the low-velocity impact damage depth,damage area and absorbed energy of the stitched three-layer foam sandwich composite were reduced by 37.7%,34.6% and 20.7%,respectively,compared with those of the non-stitched single-layer sandwich material.展开更多
With the development of computer vision technology,panoramic image stitching has been widely used in fields such as scene reconstruction.A single traditional image cannot fully capture the panoramic view of the iconic...With the development of computer vision technology,panoramic image stitching has been widely used in fields such as scene reconstruction.A single traditional image cannot fully capture the panoramic view of the iconic East Gate of the South Campus of Shaanxi University of Technology.Therefore,this project aims to technically fuse multiple partial images into a complete panoramic image,enabling comprehensive recording and visual presentation of the architectural landscapes and spatial environments in this area.This report first introduces the technical background and application scenarios,clarifying the necessity of panoramic image stitching in campus landscape recording.It then elaborates on the core objectives and practical values,highlighting the role of technical solutions in improving image quality.Technically,a modular system design based on OpenCV is adopted,including modules such as image preprocessing,feature extraction and matching,image registration,fusion,and post-processing.Specifically,the SIFT algorithm is applied for feature extraction,KNN combined with ratio testing is used for feature matching,image registration is achieved by calculating the homography matrix,the fusion process utilizes multiband blending and Laplacian pyramid,and post-processing includes operations such as black area filling and CLAHE contrast enhancement.The experiment was conducted in a specific hardware and software environment using five overlapping images.After preprocessing,stitching,detail enhancement,and black edge repair,a panoramic image was successfully generated.The results show that the panoramic image fully presents the relevant scenery,with concealed seams,balanced exposure differences,and strong hierarchical details.This report provides a systematic description of the project’s technical implementation and achievement application.展开更多
There is still a dearth of systematic study on picture stitching techniques for the natural tubular structures of intestines,and traditional stitching techniques have a poor application to endoscopic images with deep ...There is still a dearth of systematic study on picture stitching techniques for the natural tubular structures of intestines,and traditional stitching techniques have a poor application to endoscopic images with deep scenes.In order to recreate the intestinal wall in two dimensions,a method is developed.The normalized Laplacian algorithm is used to enhance the image and transform it into polar coordinates according to the characteristics that intestinal images are not obvious and usually arranged in a circle,in order to extract the new image segments of the current image relative to the previous image.The improved weighted fusion algorithm is then used to sequentially splice the segment images.The experimental results demonstrate that the suggested approach can improve image clarity and minimize noise while maintaining the information content of intestinal images.In addition,the method's seamless transition between the final portions of a panoramic image also demonstrates that the stitching trace has been removed.展开更多
Optical microscopes are essential tools for scientific research,but traditional microscopes are restricted to capturing only two-dimensional(2D)texture information,lacking comprehensive three-dimensional(3D)morphology...Optical microscopes are essential tools for scientific research,but traditional microscopes are restricted to capturing only two-dimensional(2D)texture information,lacking comprehensive three-dimensional(3D)morphology capabilities.Additionally,traditional microscopes are inherently constrained by the limited space-bandwidth product of optical systems,resulting in restricted depth of field(DOF)and field of view(FOV).Attempts to expand DOF and FOV typically come at the cost of diminished resolution.In this paper,we propose a texture-driven FOV stitching algorithm specifically designed for extended depth-of-field(EDOF)microscopy,allowing for the integration of 2D texture and 3D depth data to achieve high-resolution,high-throughput multimodal imaging.Experimental results demonstrate an 11-fold enhancement in DOF and an 8-fold expansion in FOV compared to traditional microscopes,while maintaining axial resolution after FOV extension.展开更多
Blended-Wing-Body(BWB)aircraft is promoted as one of the most possible layouts to achieve more sustainable civil aviation.Due to the non-circular cross-section of the center-body,a bulge deformation forms over the upp...Blended-Wing-Body(BWB)aircraft is promoted as one of the most possible layouts to achieve more sustainable civil aviation.Due to the non-circular cross-section of the center-body,a bulge deformation forms over the upper surface of the body under the coupled loads of the internal pressurization of the cabin and the aerodynamic bending moments of the wing,which reduces the lift-to-drag ratio of BWB aircraft.Under a limited deformation,the relationship between the aerodynamic performance and the structural weight needs to be studied.In this work,the effects of stiffness constraints on the center-body deformation,structural weight of the airframe and aerodynamic performance were investigated by using an analytical model of the Pultruded Rod Stitched Efficient Unitized Structure(PRSEUS)for the airframe and the computational fluid dynamics method,respectively.The results show that as the stiffness constraint increases,the spacings between the rod stringers and the frame stiffeners decrease,and the structural weight increases inversely.A 5.2% reduction of the lift-to-drag ratio is encountered at cruise for a medium deformation design of 42.8 mm/m.A higher aerodynamic penalty is suffered when the stiffness constraint is further released.The final deformation criterion is different when the weight vector of the aerodynamic performance and structural weight is different.展开更多
Traditional feature-based image stitching techniques often encounter obstacles when dealing with images lackingunique attributes or suffering from quality degradation. The scarcity of annotated datasets in real-life s...Traditional feature-based image stitching techniques often encounter obstacles when dealing with images lackingunique attributes or suffering from quality degradation. The scarcity of annotated datasets in real-life scenesseverely undermines the reliability of supervised learning methods in image stitching. Furthermore, existing deeplearning architectures designed for image stitching are often too bulky to be deployed on mobile and peripheralcomputing devices. To address these challenges, this study proposes a novel unsupervised image stitching methodbased on the YOLOv8 (You Only Look Once version 8) framework that introduces deep homography networksand attentionmechanisms. Themethodology is partitioned into three distinct stages. The initial stage combines theattention mechanism with a pooling pyramid model to enhance the detection and recognition of compact objectsin images, the task of the deep homography networks module is to estimate the global homography of the inputimages consideringmultiple viewpoints. The second stage involves preliminary stitching of the masks generated inthe initial stage and further enhancement through weighted computation to eliminate common stitching artifacts.The final stage is characterized by adaptive reconstruction and careful refinement of the initial stitching results.Comprehensive experiments acrossmultiple datasets are executed tometiculously assess the proposed model. Ourmethod’s Peak Signal-to-Noise Ratio (PSNR) and Structure Similarity Index Measure (SSIM) improved by 10.6%and 6%. These experimental results confirm the efficacy and utility of the presented model in this paper.展开更多
Oral endoscope image stitching algorithm is studied to obtain wide-field oral images through regis-tration and stitching,which is of great significance for auxiliary diagnosis.Compared with natural images,oral images ...Oral endoscope image stitching algorithm is studied to obtain wide-field oral images through regis-tration and stitching,which is of great significance for auxiliary diagnosis.Compared with natural images,oral images have lower textures and fewer features.However,traditional feature-based image stitching methods rely heavily on feature extraction quality,often showing an unsatisfactory performance when stitching images with few features.Moreover,due to the hand-held shooting,there are large depth and perspective disparities between the captured images,which also pose a challenge to image stitching.To overcome the above problems,we propose an unsupervised oral endoscope image stitching algorithm based on the extraction of overlapping regions and the loss of deep features.In the registration stage,we extract the overlapping region of the input images by sketching polygon intersection for feature points screening and estimate homography from coarse to fine on a three-layer feature pyramid structure.Moreover,we calculate loss using deep features instead of pixel values to emphasize the importance of depth disparities in homography estimation.Finally,we reconstruct the stitched images from feature to pixel,which can eliminate artifacts caused by large parallax.Our method is compared with both feature-based and previous deep-based methods on the UDIS-D dataset and our oral endoscopy image dataset.The experimental results show that our algorithm can achieve higher homography estimation accuracy,and better visual quality,and can be effectively applied to oral endoscope image stitching.展开更多
Stomachache is one of the most common diseases of digestive system, among which stomach pain of deficiency cold of spleen and stomach is the most common. Acupuncture and moxibustion therapy as an external treatment of...Stomachache is one of the most common diseases of digestive system, among which stomach pain of deficiency cold of spleen and stomach is the most common. Acupuncture and moxibustion therapy as an external treatment of traditional Chinese medicine for relieving stomach pain due to deficiency of spleen and stomach, has the advantages of convenient operation, small adverse reactions and remarkable curative effect, which is easy for patients to accept. In this paper, acupuncture and moxibustion therapy such as moxibustion and warm acupuncture therapy for stomach pain of spleen and stomach deficiency cold type is summarized to provide evidence-based basis for clinical treatment of stomach pain of spleen and stomach deficiency cold type.展开更多
Stitch density is one of the critical quality parameters of knit fabrics. This parameter is closely related to other physical quality parameters like fabric weight, fabric tightness factor, fiber types, blend ratio, y...Stitch density is one of the critical quality parameters of knit fabrics. This parameter is closely related to other physical quality parameters like fabric weight, fabric tightness factor, fiber types, blend ratio, yarn diameter and linear density, and fabric structure. Selecting stitch density (wales per inch, course per inch) is essential to getting the appropriate fabric weight and desired quality. Usually, no rules or assumptions exist to get the desired stitch density in the finished fabric stage. Fifteen types of blended knit fabrics were prepared to conduct the study. The varying percentages of cotton, polyester, and elastane are incorporated in the blends. Regression analysis and regression ANOVA tests were done to predict the stitch density of finished fabrics. A suitable regression equation is established to get the desired results. The study also found that the stitch density value in the finished stage fabric decreases by approximately 15% compared to the stitch density in the grey fabric stage. This study will help the fabric manufacturers get the finished fabric stitch density in advance by utilizing the grey fabric stitch density data set. The author expects this research to benefit the knitting and dyeing industry, new researchers, and advanced researchers.展开更多
Ceramic matrix composites (CMCs) are the preferred materials for solving advanced aerospace high-temperature structural components;it has the comprehensive advantages of higher temperature (~1500˚C) and low density. I...Ceramic matrix composites (CMCs) are the preferred materials for solving advanced aerospace high-temperature structural components;it has the comprehensive advantages of higher temperature (~1500˚C) and low density. In service environments, CMCs exhibit complex damage mechanisms and failure modes, which are affected by constituent materials, meso-architecture and inhere defects. In this paper, the in-plane tensile mechanical behavior of a plain-woven SiCf/SiC composite at room and elevated temperatures was investigated, and the factors affecting the tensile strength of the material were discussed in depth. The results show that the tensile modulus and strength of SiCf/SiC composites at high temperature are lower, but the fracture strain increases and the toughness of the composites is enhanced;the stitching holes significantly weaken the tensile strength of the material, resulting in the material is easy to break at the cross-section with stitching holes.展开更多
Stitched composite materials are emerging as a promising material due to their high interlaminar strength,combined performance and light weight.The mechanical properties of stitch yarns are very essential for stitched...Stitched composite materials are emerging as a promising material due to their high interlaminar strength,combined performance and light weight.The mechanical properties of stitch yarns are very essential for stitched composite structures.In this study,the tensile behaviors of the twisted fiber yarn in stitched composites were investigated experimentally,analytically and numerically.Two kinds of cross-sectional area of twisted yarn are proposed and discussed.The paper presents an intersecting circle model to describe the cross-section of twisted fiber yarns,and a physics-based theoretical model to predict the effective tensile moduli.The numerical models take into account the cross-sectional characteristic and the twist architecture.The investigation shows that:the sum of each fiber area should be used for experimental analysis;and the crosssectional area surrounded by the yarn profile should be used for theoretical predictions and finite element(FE)simulations.The relative errors of the prediction method and the FE simulation are less than 2%and 1%,respectively.The friction between the fibers is derived,and the effect of friction on mechanical properties is discussed.The investigation method will serve as a fundamental component of twisted fiber bundle/yarn analysis.展开更多
Tension and shear tests are carried out on composite cross-joints, produced by resin transfer moulding (RTM), stitch-RTM and cobonding techniques separately, to investigate the influences of different production metho...Tension and shear tests are carried out on composite cross-joints, produced by resin transfer moulding (RTM), stitch-RTM and cobonding techniques separately, to investigate the influences of different production methods on their mechanical properties and their failure mechanism. It is concluded from test results that, in terms of mechanical properties, the RTM-made cross-joint holds superiority over other two, and both stitch-RTM and cobonding methods have significant adverse effects on mechanical proper- t...展开更多
基金Project supported by the Excellent Young Teachers Program of the Ministry of Education of Chinathe Shu-Guang Program of the City of Shanghai+1 种基金the National Natural Sciences Foundation of China(No.10372120)Shanghai Leading Academic Discipline Project(No.Y0103).
文摘This contribution attempts to model the alteration of the in-plane elastic properties in laminates caused by stitching, and to predict the in-plane effective tensile strength of the stitched composite laminates. The distortion of in-plane fibers is considered to be the main cause that affects the in-plane mechanical properties. A fiber distortion model is proposed to characterize the fiber misalignment and the fiber content concentration due to stitching. The undistorted region, the fiber distortion region, the resin-rich pocket and the through-thickness reinforcement section are taken into account. The fiber misalignment and inhomogeneous fiber content due to stitching have been formulated by introducing two parameters, the distortion width and maximum misalignment. It has been found that the ply stress concentration in stitched laminates is influenced by the two concurrent factors, the stitch hole and inhomogeneous fiber content. The stitch hole brings about the stress concentration whereas the higher fiber content at the local region induced by stitching restrains the local deformation of the composite. The model is used to predict the tensile strength of the [0/45/0/-45/90/45/0/-45]58 T300/QY9512 composite laminate stitched by Kevlar 29 yarn with different stitching configurations, showing an acceptable agreement with experimental data.
基金National Natural Science Foundation of China(No.52075280)Natural Science Foundation of Shandong province(No.ZR2019MEE088)。
文摘A representative volume element method and a novel mesomechanical-based polyline model are proposed to describe the misalignment of in-plane fibers induced by the insertion of stitch thread.A multi-scale mathematical model of in-plane elastic parameters for stitched composite laminate is established with ply-angle and stitch parameters as well as material parameters taken into account.Based on the fabrication of specimens and the verification of experimental platform,the superposition influences of stitch on structural anisotropy are revealed by the developed theoretical model.Results indicate that the stitch orientation can increase the structural anisotropy.The decreases of stitch pitch and spacing as well as the increase of thread diameter obviously reduce the elastic and shear moduli of laminates.Furthermore,the elastic and shear moduli as well as Poisson’s ratios show sinusoidal changes with a period of 90°as the ply-angle increases.The theoretical model not only analyzes the in-plane mechanical properties of stitched laminate with ply-angle,but also lays a foundation for the dynamic studies of stitched sandwich structures with ribs in the future.
文摘The mechanical properties of silica material in the monolithic form are ;far from acceptable levels. In this paper, 3D stitched quartz preform was used for the fiber reinforcement, and quartz fibers- reinforced silica composites were prepared by the silica sol-infiltration-sintering method. The density of the composite was up to 1.71 g/cm3 after 10 infiltration-sintering cycles. The flexural strength and the in-plane shear strength were 61.7 MPa and 20.3 MPa, respectively. The flexural stress-deflection curve exhibited mostly nonlinear behavior, which was different from that of monolithic ceramics. Because of the existence of the fiber in Z axis direction, shearing property between the different layers of 3D stitched composites were greatly enhanced. Toughness effect of the 3D stitched quartz preform was conspicuous. The as-fabricated composites showed non-catastronhic failure behavior resulting from weak fiber/matrix interface.
文摘The recent advancements in the field of Virtual Reality(VR)and Augmented Reality(AR)have a substantial impact on modern day technology by digitizing each and everything related to human life and open the doors to the next generation Software Technology(Soft Tech).VR and AR technology provide astonishing immersive contents with the help of high quality stitched panoramic contents and 360°imagery that widely used in the education,gaming,entertainment,and production sector.The immersive quality of VR and AR contents are greatly dependent on the perceptual quality of panoramic or 360°images,in fact a minor visual distortion can significantly degrade the overall quality.Thus,to ensure the quality of constructed panoramic contents for VR and AR applications,numerous Stitched Image Quality Assessment(SIQA)methods have been proposed to assess the quality of panoramic contents before using in VR and AR.In this survey,we provide a detailed overview of the SIQA literature and exclusively focus on objective SIQA methods presented till date.For better understanding,the objective SIQA methods are classified into two classes namely Full-Reference SIQA and No-Reference SIQA approaches.Each class is further categorized into traditional and deep learning-based methods and examined their performance for SIQA task.Further,we shortlist the publicly available benchmark SIQA datasets and evaluation metrices used for quality assessment of panoramic contents.In last,we highlight the current challenges in this area based on the existing SIQA methods and suggest future research directions that need to be target for further improvement in SIQA domain.
文摘This paper presents an application of stitched ground plane for microstrip patch antenna design. In this work Matlab interface to computer embroidery techniques were used to implement the felt and denim substrates on microstrip patch antenna. These antennas were simulated using a commercial full 3D electromagnetic CST Microwave Studio 2019. A method to optimize the stitch patterns with conductive thread for antenna ground plane for 2.45 GHz industrial, scientific, and medical (ISM) band and 5 GHz wearable wireless local area networks (WLAN) frequencies was achieved. Rigid and flexible wearable antennas (microstrip patch antennas) were fabricated using the stitched ground plane. The electrical resistance was reduced between the meshes during the stitching design process. Results in terms of bandwidth, radiation patterns and reflection coefficients (S<sub>11</sub>) are presented.
文摘This work reveals that the addition of periodically distributed stitches to sandwich structure enables a significant reduction of vibration in stop-band and this new functionality is systematically investigated.Firstly,a finite element model which is capable of taking into consideration the three layers of the sandwich as well as the stitches is developed.The diagram of dispersion is calculated by applying Floquet-Bloch theorem to the boundaries of unit cell.With properly chosen properties of stitches,a stop-band for flexural wave is observed.This stop-band is further confirmed by the forced response of a large stitched sandwich panel under point excitation.The level of vibration in the stop-band is significantly reduced.The influence of the stitch rigidity and density on upper and lower limits of stop-band is also examined,which confirms that stitched sandwich can be tuned to mitigate vibration in a certain frequency band with appropriate stitch properties.These investigations have demonstrated the potential application of stitched sandwich in the area of vibration reduction.
文摘This work explores the optimal mesh structure, stitch density and production technique of stitched ground plane for microstrip patch antenna. Meshed ground plane was used as a generic problem. A stitched ground plane is pro-posed and designed using Matlab interface to computer embroidery. Using the meshed or stitched ground plane as a case study, the resistance between meshes was analysed and measured. The equivalent resistance between nodes is a function of their distance apart. A finite resistive grid was simulated and compared to measured sets of data. A microstrip patch antenna with stitched ground shows comparable performance to the conventional etched ground of the size in terms of bandwidth. The stitched ground plane has a higher band-width than the etched copper ground plane because of the increased thickness of the substrate. Thus, it can be concluded that the use of the interface method shows the possibilities of controlling the stitch density and distances between mesh nodes. The interface increases the stitching density and reduces the elec-trical resistance between mesh nodes making the antennas flexible and weara-ble. The functionality of these antenna samples has been tested and validated using microstrip patch ground at 2.45 GHz and 5 GHz. Measurement results on the proposed stitched ground planes were compared with the theory of infinite resistive network that shows good agreement.
文摘Crack growth resistance plays a different role in crashworthiness analysis since the progressive energy absorption is based on controllable fracture mechanisms. In this regard, the present paper studies the efficient crack growth resistance in off-axis crushing of composite tubular structures by implementing natural fiber yarns. One of the through-to-thickness reinforcement methods known as stitching has been chosen to influence the axial and off-axis crushing process. Improving the crack growth resistance and appropriate fiber breakage at different stages of crushing process can significantly improve the resistance force and consequently the energy absorption capability of composite absorbers in axial and off-axis crushing. This analysis will be applied to non-stitched and stitched CFRP composite boxes which showed brittle fracture and transverse shearing crushing modes under off-axis loading of 10 degrees. The analytical methods are also implemented to analysze the effect of various failure mechanisms such as bending, friction, bundle fracture, and interlaminar crack growth for the observed crushing modes. The proposed model is able to predict the crushing load and crush force efficiency in close agreement from experimental studies.
文摘Low-velocity impact damage known as“imperceptible”damage usually destroys the structural integrity of the material and seriously affects the service life of the materials.To improve the low-velocity impact resistance of foam sandwich composites,an innovative concept of a stitched multi-layer sandwich structure by organically combining the discrete splitting of foam layer with full thickness stitching was proposed,and its low-velocity impact resistance obtained through drop-hammer impact tests was explored.The results showed that the multi-layer foam sandwich structure acted as a stress disperser and reduced the irreversible impact damage.The depth and area of low-velocity impact damage of multi-layer foam sandwich composites gradually decreased with increasing the number of the layers.The stitched structure would improve the integrity of the foam sandwich composites and inhibit the propagation of cracks.The maximum impact load of the stitched foam sandwich composite increased by approximately 5% compared with that of the non-stitched material.In addition,the low-velocity impact damage depth,damage area and absorbed energy of the stitched three-layer foam sandwich composite were reduced by 37.7%,34.6% and 20.7%,respectively,compared with those of the non-stitched single-layer sandwich material.
文摘With the development of computer vision technology,panoramic image stitching has been widely used in fields such as scene reconstruction.A single traditional image cannot fully capture the panoramic view of the iconic East Gate of the South Campus of Shaanxi University of Technology.Therefore,this project aims to technically fuse multiple partial images into a complete panoramic image,enabling comprehensive recording and visual presentation of the architectural landscapes and spatial environments in this area.This report first introduces the technical background and application scenarios,clarifying the necessity of panoramic image stitching in campus landscape recording.It then elaborates on the core objectives and practical values,highlighting the role of technical solutions in improving image quality.Technically,a modular system design based on OpenCV is adopted,including modules such as image preprocessing,feature extraction and matching,image registration,fusion,and post-processing.Specifically,the SIFT algorithm is applied for feature extraction,KNN combined with ratio testing is used for feature matching,image registration is achieved by calculating the homography matrix,the fusion process utilizes multiband blending and Laplacian pyramid,and post-processing includes operations such as black area filling and CLAHE contrast enhancement.The experiment was conducted in a specific hardware and software environment using five overlapping images.After preprocessing,stitching,detail enhancement,and black edge repair,a panoramic image was successfully generated.The results show that the panoramic image fully presents the relevant scenery,with concealed seams,balanced exposure differences,and strong hierarchical details.This report provides a systematic description of the project’s technical implementation and achievement application.
基金the Special Research Fund for the Natural Science Foundation of Chongqing(No.cstc2019jcyjmsxm1351)the Science and Technology Research Project of Chongqing Education Commission(No.KJQN2020006300)。
文摘There is still a dearth of systematic study on picture stitching techniques for the natural tubular structures of intestines,and traditional stitching techniques have a poor application to endoscopic images with deep scenes.In order to recreate the intestinal wall in two dimensions,a method is developed.The normalized Laplacian algorithm is used to enhance the image and transform it into polar coordinates according to the characteristics that intestinal images are not obvious and usually arranged in a circle,in order to extract the new image segments of the current image relative to the previous image.The improved weighted fusion algorithm is then used to sequentially splice the segment images.The experimental results demonstrate that the suggested approach can improve image clarity and minimize noise while maintaining the information content of intestinal images.In addition,the method's seamless transition between the final portions of a panoramic image also demonstrates that the stitching trace has been removed.
基金supported by Science Foundation of Donghai Lab-oratory(No.DH-2022KF01001).
文摘Optical microscopes are essential tools for scientific research,but traditional microscopes are restricted to capturing only two-dimensional(2D)texture information,lacking comprehensive three-dimensional(3D)morphology capabilities.Additionally,traditional microscopes are inherently constrained by the limited space-bandwidth product of optical systems,resulting in restricted depth of field(DOF)and field of view(FOV).Attempts to expand DOF and FOV typically come at the cost of diminished resolution.In this paper,we propose a texture-driven FOV stitching algorithm specifically designed for extended depth-of-field(EDOF)microscopy,allowing for the integration of 2D texture and 3D depth data to achieve high-resolution,high-throughput multimodal imaging.Experimental results demonstrate an 11-fold enhancement in DOF and an 8-fold expansion in FOV compared to traditional microscopes,while maintaining axial resolution after FOV extension.
基金supported partially by the National Key Laboratory Project,China(No.61422010201).
文摘Blended-Wing-Body(BWB)aircraft is promoted as one of the most possible layouts to achieve more sustainable civil aviation.Due to the non-circular cross-section of the center-body,a bulge deformation forms over the upper surface of the body under the coupled loads of the internal pressurization of the cabin and the aerodynamic bending moments of the wing,which reduces the lift-to-drag ratio of BWB aircraft.Under a limited deformation,the relationship between the aerodynamic performance and the structural weight needs to be studied.In this work,the effects of stiffness constraints on the center-body deformation,structural weight of the airframe and aerodynamic performance were investigated by using an analytical model of the Pultruded Rod Stitched Efficient Unitized Structure(PRSEUS)for the airframe and the computational fluid dynamics method,respectively.The results show that as the stiffness constraint increases,the spacings between the rod stringers and the frame stiffeners decrease,and the structural weight increases inversely.A 5.2% reduction of the lift-to-drag ratio is encountered at cruise for a medium deformation design of 42.8 mm/m.A higher aerodynamic penalty is suffered when the stiffness constraint is further released.The final deformation criterion is different when the weight vector of the aerodynamic performance and structural weight is different.
基金Science and Technology Research Project of the Henan Province(222102240014).
文摘Traditional feature-based image stitching techniques often encounter obstacles when dealing with images lackingunique attributes or suffering from quality degradation. The scarcity of annotated datasets in real-life scenesseverely undermines the reliability of supervised learning methods in image stitching. Furthermore, existing deeplearning architectures designed for image stitching are often too bulky to be deployed on mobile and peripheralcomputing devices. To address these challenges, this study proposes a novel unsupervised image stitching methodbased on the YOLOv8 (You Only Look Once version 8) framework that introduces deep homography networksand attentionmechanisms. Themethodology is partitioned into three distinct stages. The initial stage combines theattention mechanism with a pooling pyramid model to enhance the detection and recognition of compact objectsin images, the task of the deep homography networks module is to estimate the global homography of the inputimages consideringmultiple viewpoints. The second stage involves preliminary stitching of the masks generated inthe initial stage and further enhancement through weighted computation to eliminate common stitching artifacts.The final stage is characterized by adaptive reconstruction and careful refinement of the initial stitching results.Comprehensive experiments acrossmultiple datasets are executed tometiculously assess the proposed model. Ourmethod’s Peak Signal-to-Noise Ratio (PSNR) and Structure Similarity Index Measure (SSIM) improved by 10.6%and 6%. These experimental results confirm the efficacy and utility of the presented model in this paper.
基金the National Natural Science Foundation of China(No.61976091)。
文摘Oral endoscope image stitching algorithm is studied to obtain wide-field oral images through regis-tration and stitching,which is of great significance for auxiliary diagnosis.Compared with natural images,oral images have lower textures and fewer features.However,traditional feature-based image stitching methods rely heavily on feature extraction quality,often showing an unsatisfactory performance when stitching images with few features.Moreover,due to the hand-held shooting,there are large depth and perspective disparities between the captured images,which also pose a challenge to image stitching.To overcome the above problems,we propose an unsupervised oral endoscope image stitching algorithm based on the extraction of overlapping regions and the loss of deep features.In the registration stage,we extract the overlapping region of the input images by sketching polygon intersection for feature points screening and estimate homography from coarse to fine on a three-layer feature pyramid structure.Moreover,we calculate loss using deep features instead of pixel values to emphasize the importance of depth disparities in homography estimation.Finally,we reconstruct the stitched images from feature to pixel,which can eliminate artifacts caused by large parallax.Our method is compared with both feature-based and previous deep-based methods on the UDIS-D dataset and our oral endoscopy image dataset.The experimental results show that our algorithm can achieve higher homography estimation accuracy,and better visual quality,and can be effectively applied to oral endoscope image stitching.
文摘Stomachache is one of the most common diseases of digestive system, among which stomach pain of deficiency cold of spleen and stomach is the most common. Acupuncture and moxibustion therapy as an external treatment of traditional Chinese medicine for relieving stomach pain due to deficiency of spleen and stomach, has the advantages of convenient operation, small adverse reactions and remarkable curative effect, which is easy for patients to accept. In this paper, acupuncture and moxibustion therapy such as moxibustion and warm acupuncture therapy for stomach pain of spleen and stomach deficiency cold type is summarized to provide evidence-based basis for clinical treatment of stomach pain of spleen and stomach deficiency cold type.
文摘Stitch density is one of the critical quality parameters of knit fabrics. This parameter is closely related to other physical quality parameters like fabric weight, fabric tightness factor, fiber types, blend ratio, yarn diameter and linear density, and fabric structure. Selecting stitch density (wales per inch, course per inch) is essential to getting the appropriate fabric weight and desired quality. Usually, no rules or assumptions exist to get the desired stitch density in the finished fabric stage. Fifteen types of blended knit fabrics were prepared to conduct the study. The varying percentages of cotton, polyester, and elastane are incorporated in the blends. Regression analysis and regression ANOVA tests were done to predict the stitch density of finished fabrics. A suitable regression equation is established to get the desired results. The study also found that the stitch density value in the finished stage fabric decreases by approximately 15% compared to the stitch density in the grey fabric stage. This study will help the fabric manufacturers get the finished fabric stitch density in advance by utilizing the grey fabric stitch density data set. The author expects this research to benefit the knitting and dyeing industry, new researchers, and advanced researchers.
文摘Ceramic matrix composites (CMCs) are the preferred materials for solving advanced aerospace high-temperature structural components;it has the comprehensive advantages of higher temperature (~1500˚C) and low density. In service environments, CMCs exhibit complex damage mechanisms and failure modes, which are affected by constituent materials, meso-architecture and inhere defects. In this paper, the in-plane tensile mechanical behavior of a plain-woven SiCf/SiC composite at room and elevated temperatures was investigated, and the factors affecting the tensile strength of the material were discussed in depth. The results show that the tensile modulus and strength of SiCf/SiC composites at high temperature are lower, but the fracture strain increases and the toughness of the composites is enhanced;the stitching holes significantly weaken the tensile strength of the material, resulting in the material is easy to break at the cross-section with stitching holes.
基金co-supported by the National Natural Science Foundation of China(Nos.51772009,51911530201,51802264 and 51275023)。
文摘Stitched composite materials are emerging as a promising material due to their high interlaminar strength,combined performance and light weight.The mechanical properties of stitch yarns are very essential for stitched composite structures.In this study,the tensile behaviors of the twisted fiber yarn in stitched composites were investigated experimentally,analytically and numerically.Two kinds of cross-sectional area of twisted yarn are proposed and discussed.The paper presents an intersecting circle model to describe the cross-section of twisted fiber yarns,and a physics-based theoretical model to predict the effective tensile moduli.The numerical models take into account the cross-sectional characteristic and the twist architecture.The investigation shows that:the sum of each fiber area should be used for experimental analysis;and the crosssectional area surrounded by the yarn profile should be used for theoretical predictions and finite element(FE)simulations.The relative errors of the prediction method and the FE simulation are less than 2%and 1%,respectively.The friction between the fibers is derived,and the effect of friction on mechanical properties is discussed.The investigation method will serve as a fundamental component of twisted fiber bundle/yarn analysis.
文摘Tension and shear tests are carried out on composite cross-joints, produced by resin transfer moulding (RTM), stitch-RTM and cobonding techniques separately, to investigate the influences of different production methods on their mechanical properties and their failure mechanism. It is concluded from test results that, in terms of mechanical properties, the RTM-made cross-joint holds superiority over other two, and both stitch-RTM and cobonding methods have significant adverse effects on mechanical proper- t...
