Thick-walled Structures Research Articles

Perivascular PDGFRB+ cells accompany lesion formation and clinical evolution differentially in two different EAE models.

Multiple Sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) that may lead to progressive disability. Here, we explored the behavioral pattern and the role of vasculature especially PDGFRB+ pericytes/ perivascular cells, in MS pathogenesis. We have evaluated vascular changes in two different experimental allergic encephalomyelitis (EAE) mice models (MOG and PLP-induced). PDGFRB+ cells demonstrated distinct and different behavioral patterns. In both models, fibrosis formation was detected via collagen, fibronectin, and extracellular matrix accumulation. The PLP-induced animal model revealed that fibrosis predominantly occurs in perivascular locations and that PDGFRB+ cells are accumulated around vessels. Also, the expression of fibrotic genes and genes coding extracellular matrix (ECM) proteins are upregulated. Moreover, the perivascular thick wall structures in affected vessels of this model presented primarily increased PDGFRB+ cells but not NG2+ cells in the transgenic NG2-DsRed transgenic animal model. On the other hand, in MOG induced model, PDGFRB+ perivascular cells were accumulated at the lesion sites. PDGFRB+ cells colocalized with ECM proteins (collagen, fibronectin, and lysyl oxidase L3). Nevertheless, both MOG and PLP-immunized mice showed increasing EAE severity, and disability parallel with enhanced perivascular cell accumulation as the disease progressed from earlier (day 15) to later (day 40). As a result, we have concluded that PDGFRB+ perivascular cells may be participating in lesion progression and as well as demonstrating different responses in different EAE models.

STUDY OF THE MATERIAL PROPERTIES INFLUENCE AND CONTACT CONDITIONS ON THE STRESS-STRAIN STATE DURING THE INTERACTION OF A STAMP AND A PLATE

The article examines the results obtained when applying the perturbation method to the solution of individual contact problems.Attention is paid to the influence of non-ideal properties of materials of interaction bodies. The influence of the complex geometry of the contact zone is also taken into account. In the article, mathematical models of problems on the interaction of an elastic orthotropic semi-infinite plate with cylindrical anisotropy in the form of a curvilinear sector are constructed and considered. In the process of interaction between the stamp and the plate, there are areas of sliding and adhesion. The original problems of the theory of elasticity, difficult in their initial formulation, in the process of applying the perturbation method are reduced to the sequential solution of simpler problems of the theory of functions of a complex variable. Analytical solutions to the problem of the interaction of an elastic anisotropic semi-infinite plate in the form of a curvilinear sector and a rigid stamp were obtained, taking into account the presence of areas of sliding and adhesion in the contact zone. As significant results obtained after solving the formulated contact problems, it is possible to indicate the found regularities of stress distribution under the stamp, as well as the dependence of this distribution on the dimensions of the contact area. An analysis of the dependence of the size of the coupling zone on the stiffness characteristics of the sector was also carried out, taking into account different materials (for the sector), the opening angle of the sector and the dimensions of the stamp. In order to further develop the method and prove the convenience of applying the perturbation method in complex mixed boundary value problems, a study of the stress-strain state of an elastic anisotropic plate for an analogue of the Galin problem was carried out, while cases for different plate materials were considered. Corresponding analytical solutions were also obtained. The dependence of the size of the adhesion area on the dimensions of the stamp and the opening angle of the sector, as well as on the physical properties of the material of the sector, was analyzed. Possible boundary transitions are performed in the work and a comparison with known scientific results is made. The approach proposed by the authors makes it possible to obtain analytical solutions to practically important problems of contact interaction, to carry out possible assessments of the stress-strain state of thick-walled structures with reinforcing elements, stamps, overlays, etc. The results may also be useful. when designing mining works. At the same time, such important issues as the peculiarities of the physical properties of the materials of the interacting bodies, the complex geometry of the contact zone, the occurrence of areas of sliding and adhesion in the contact zone are taken into account.

Design of welding parameters for laser welding of thick-walled structures made of aluminum alloy

The paper deals with the laser welding of thick-walled plates with a thickness of 20 mm made of EN AW5083-H111 aluminum alloy. A simulation model for the analysis of the laser welding process is developed and verify using temperature measurement during experimental laser welding of samples by a TruDisk 4002 laser device. Based on the numerical simulation of the laser welding process in the ANSYS program code, suitable parameters for production of high-quality weld joints were suggested. For welding at a speed of 10 mm.s−1, the laser power of 7 kW is recommended. A laser with the power of 10 kW is required for the higher welding speed of 20 mm.s−1.

Temperature-mediated construction of a plantar pressure-relieving, thermally insulating, and biodegradable thick-walled cellulose sponge insole

Plantar pressure can be reduced and wearing comfort can be improved by using cushioning materials such as insoles. However, the biodegradation of most commercial insoles is difficult, incurring high disposal costs both economically and environmentally. Herein, we present a temperature-mediated approach for constructing a plantar pressure reducing, thermally insulating, and biodegradable thick-walled cellulose sponge (TWCS) insole from cotton linters. 3D Raman imaging and crystallographic test results demonstrated that freezing temperature affected the packing behavior of the dispersed cellulose at the ice crystal boundary, resulting in a marked distinction between wall thicknesses and crystallinity of sponges, from 0.36 μm and 0.39 to 7.74 μm and 0.46, at distinguishing temperatures (−25 ˚C, −78 ˚C, and − 198 ˚C). Benefiting from the thick-walled structure generated during the temperature-mediated interfacial assembly, the mechanical strength of the TWCS was significantly increased by 5.6 times to 569 kPa, accompanied by significantly enhanced structural stability, pressure-relieving, and thermal insulating characteristics. Subsequently, we designed TWCS as a biomass insole, and its performance was thoroughly examined using plantar pressure testing, thermal performance assessment, finite element simulation, and degradability investigations. The results demonstrate that TWCS can effectively decompress (1-fold pressure reduction), disperse external stresses, prevent heat loss and complete degradation within 50 days under biological conditions, and can potentially replace traditional petroleum-based sponge insoles.

A Sustainable Approach to Build Insulated External Timber Frame Walls for Passive Houses Using Natural and Waste Materials

This paper presents structures of timber-framed walls designed for passive houses, using natural and waste resources as insulation materials, such as wool, wood fibers, ground paper, reeds (Phragmites communis), and Acrylonitrile Butadiene Styrene (ABS) wastes. The insulation systems of stud walls composed of wool–ABS composite boards and five types of fillers (wool, ABS, wood fibers, ground paper, and reeds) were investigated to reach U-value requirements for passive houses. The wall structures were designed at a thickness of 175 mm, including gypsum board for internal wall lining and oriented strand board (OSB) for the exterior one. The testing protocol of thermal insulation properties of wall structures simulated conditions for indoor and outdoor temperatures during the winter and summer seasons using HFM-Lambda laboratory equipment. In situ measurements of U-values were determined for the experimental wall structures during winter time, when the temperature differences between outside and inside exceeded 10 °C. The results recorded for the U-values between 0.20 W/m2K and 0.35 W/m2K indicate that the proposed structures are energy-efficient walls for passive houses placed in the temperate-continental areas. The vapour flow rate calculation does not indicate the presence of condensation in the 175 mm thick wall structures, which proves that the selected thermal insulation materials are not prone to degradation due to condensation. The research is aligned to the international trend in civil engineering, oriented to the design and construction of low-energy buildings on the one hand and the use of environmentally friendly or recycled materials on the other.

Acoustic Black hole effects in Thin-walled structures: Realization and mechanisms

Vibrational Acoustic Black Holes (ABHs) on flexural waves are commonly achieved in thick-walled structures whose local thickness should undergo significant variation according to a power-law relationship. The topic has been widely explored despite the fact that the requirement imposed for structural thickness has been constantly challenged by practical applications. Existing open literature does not provide convincing answers to the practically important question of whether sensible ABH effects can still be produced in structures within a thin thickness range through proper design, and if so, what is the underlying mechanism. In this work, through numerical and experimental investigations, we demonstrate that ABH effects can be readily achieved in a compound ABH structure of thin thickness with viscoelastic material filling. The compound structural design makes effective use of both ABH effects and the shear effects of the damping material, mainly along the mid-plane of the structure, to collectively generate a significant enhancement of the structural damping. While the shear-induced damping dominates the lower frequency region, ABH-induced damping becomes dominant once the ABH effect is cut-on. A good compromise between the two effects requires the stiffness of the damping materials and other ABH parameters to be properly chosen in order to ensure broadband benefit in terms of vibration reduction through damping enhancement.

The influence of char particle morphology on char burnout behavior by atomistic simulation

Bituminous coal char particles will differ in morphology, porosity, reactivity, and behavior within the zone II regime (where most practical system operates) due to the influence of maceral, rank, and time–temperature-histories. Effective boiler design requires simulations that appropriately capture char behavior. Most simulations, however, assume solid spherical particles that have homogeneous physical and chemical properties. Unfortunately, coal and time–temperature-history variations make it impossible to make a direct comparison of morphologies alone using traditional experimental approaches. Thus, here the influences of coal char morphologies on its reaction behavior and physical structure were explored via small-scale atomistic simulations. Three (ash-free) chars of solid, thick-, and thin-walled morphologies were examined. The atomistic representations had ∼ 143000 carbon atoms, comprised of similar polycyclic aromatic hydrocarbons (PAH) sizes and stacking distributions. While these structures are far below the actual particle size, the approach permits a direct comparison with a level of control not possible via physical experimentation. The densities of the thick- and thin-walled char models were similar to literature observations (apparent and helium densities). The specific surface area for the solid, thick-, and thin-walled char models were 110, 368, and 509 m2/g, with the latter two being closer to experimental data. A simplified combustion simulation (diffusion and oxygen proximity calculations) demonstrated that the char morphology had a significant impact upon their relative reactivities. The thin-walled structure had the highest overall reactivity due to greater reactive surface access, while the solid and thick-walled structure was respectively 27 and 23% lower. The reaction rate profiles with char conversion for these three structures are close to the experimental observations for pulverized bituminous coal chars, where the rate peak occurs at ∼ 20% conversion. The changes in char size, density, and specific surface area (with char conversion) indicated the thick-walled structure was more similar to the literature data. These atomistic approaches have the potential to aid in exploring the reaction behavior of char particles with various morphologies and complicated structures. With scale-up additional behaviors such as particle fragmentation and ash behavior could be incorporated.

Discovering the chlamydospore regulatory network in Candida albicans

A normal resident of healthy humans and warm-blooded animals, C. albicans is a commensal fungus that is also among the most common opportunistic pathogens of humans. C. albicans forms unique morphological structures called chlamydospores, which are large, spherical, thick-walled structures formed at the ends of hyphae that have unknown biological function. My goal is to discover the regulatory network controlling chlamydospore formation in C. albicans. By determining this network, we can gain insight into the biological roles of chlamydospores in the C. albicans lifestyle, better understand C. albicans morphological transitions, and determine the selective advantage (if any) provided by chlamydospores to this pathogenic fungus. To determine this regulatory network, I have screened a library of 211 C. albicans transcription factor (TF) homozygous deletion mutants to assay for their abilities to form chlamydospores under standard chlamydospore-inducing growth conditions. I have identified seven TF mutants that fail to produce any chlamydospores andthree TF mutants that produce high levels of chlamydospores relative to WT. To characterize the transcriptional changes occurring during chlamydospore formation, I have performed RNA sequencing (RNA-seq) on these identified regulator mutants to uncover the differentially regulated target genes of each chlamydospore regulator. I will use genome-wide chromatin immunoprecipitation followed by sequencing (ChIP-seq) on epitope-tagged versions of these regulators to determine which genes are directly under the control of each TF. RNA-seq coupled with ChIP-seq will allow me to determine the regulatory network controlling chlamydospore formation in C. albicans.

Lifetime prediction of bonded structural patch repairs for wind turbine pitch bearing strengthening

ABSTRACT There is a growing trend in the use of adhesively bonded patches to repair structures that are subjected to fatigue loads in an attempt to reduce the propagation of an existing crack. The fatigue lifetime prediction of the adhesive used in bonded patch repair is a state-of-the-art challenge, especially when in-service conditions must also be considered. Different approaches have been identified in the literature to analyse structural failure; the methods based on fracture mechanics seem more promising for adhesives because the presence of defects is also considered in the analysis. A considerable amount of work has been undertaken to analyse the delamination of layered structures using cohesive zone modelling (CZM). However, research analysing fatigue delamination in bonded thick-walled structures (> 30 mm) is lacking. The present work proposes a methodology to predict the lifetime of an adhesively bonded patch repair applied to a thick-walled structure, specifically looking at the bearing ring structural fatigue (RSF) life extension of a pitch bearing commonly used in wind turbines.

Numerical Estimation of the Geometry of the Deposited Layers during Direct Laser Deposition of Multi-Pass Walls

Direct laser deposition (DLD) is a promising additive technology that allows for the rapid and cheap production of metal parts of complex geometry in various sectors of mechanical engineering. Thick-walled metal structures occupy a significant part in mechanical engineering. The purpose of this study was to develop and test an algorithm for predicting the geometry of deposited multi-pass walls. To achieve this goal, the main interrelated processes involved in the formation of a multi-pass wall were described—the process of laser radiation propagation, the process of heat transfer and the process of bead formation. To construct the calculation algorithm, five characteristic types of beads are identified. For these five types, the features of the bead formation and the features of the laser radiation intensity distribution are described. The calculated data were verified. A good match of the calculated data with the geometry of the deposited walls from AISI321 steel, Inconel718 and Ti-6Al-4V alloys was obtained.

Gradient-extended damage analysis with reduced integration-based solid-shells at large deformations

The present contribution is concerned with the extension of a recently presented non-local damage analysis of shells to the geometrically non-linear regime. For this purpose, a gradient-extended two-surface damage-plasticity model for finite strains is incorporated into a low-order solid-shell finite element formulation for large deformations which is based on reduced integration with hourglass stabilization. Due to a specific combination of the assumed natural strain (ANS) and the enhanced assumed strain (EAS) method, the most relevant locking pathologies which stem from the linear interpolation of the displacement field are eliminated. Furthermore, an additional micromorphic nodal degree of freedom which comes from the gradient extension is considered. A polynomial approximation of the kinematic as well as the constitutively dependent quantities within the weak forms provides a suitable hourglass stabilization which is computationally highly efficient, since the corresponding element residual vectors and stiffness matrices can be determined analytically. Three numerical examples of different elastic as well as elasto-plastic plate and shell configurations, reveal the ability of the present framework to efficiently and accurately predict the damage processes within both geometrically non-linear thin and thick-walled structures.

Analysis of Thick-Walled Spherical Shells Subjected to Various Temperature Gradients: Thermo-Elasto-Plastic and Residual Stress Studies

In this paper, the elastic, elastoplastic, and thermal residual stresses due to autofrettage in a thick-walled spherical structure have been investigated. A steady-state radial temperature gradient has been applied throughout the thickness of the shell structure made of elastic-perfect-plastic constitutive material. This temperature gradient is assumed to be in both directions from inward to outward and vice versa. To calculate the equivalent stress and initial yield point, the Von Mises yield criterion (failure criterion) is used, and all relations are derived analytically. Then, the differences between the elastic–plastic behavior and the residual stresses in the thick-walled structure, caused by loading in two states of the temperature gradient, are investigated. Finally, the conditions for the occurrence of reverse yielding and its relation with the thickness and temperature gradient are carefully studied.

EP.TH.665Where’s the gallbladder? A rare case of gallbladder agenesis with cystic duct stone

Abstract Aims Gallbladder agenesis is a rare congenital anatomical malformation with an incidence of 0.007-0.0027%. Although usually asymptomatic, clinically it may present similarly to biliary colic. There may be increased risk of de novo biliary duct stone formation due to biliary dyskinesia, subsequent duct dilatation and biliary stasis. We present a case of incidental gallbladder agenesis identified during intended laparoscopic cholecystectomy. Methods A 68 year-old female with no significant comorbidities presented with a 16 hour history of colicky right upper quadrant pain and vomiting. She had been awaiting cholecystectomy for increasingly symptomatic gallstones, most recently visualised within a contracted gallbladder on ultrasound two months prior. Recurrently obstructive LFT’s warranted urgent magnetic resonance cholangiopancreatography (MRCP), which identified a poorly-visualised contracted gallbladder and a 10mm common bile duct without filling defect. At index laparoscopic cholecystectomy, a very small thick-walled structure resembling the gallbladder was identified and safely excised in retrograde; a stone was seen within. Results Macroscopic examination revealed a 27 x 9 x 11mm piece of dark brown tissue containing soft orange material. Microscopic histological examination confirmed this to be cystic duct focally lined by mucinous epithelium with chronic inflammation. Findings were consistent with gallbladder agenesis. Conclusions Although rare, it is important for surgeons to maintain an index of suspicion for gallbladder agenesis, particularly if repeated imaging demonstrates a poorly-visualised or ‘contracted’ gallbladder despite adequate fasting. Furthermore, as in this case, the presence of ‘gallbladder’ stones radiologically does not preclude gallbladder agenesis. Anticipation of this malformation may aid interpretation of biliary anatomy, if incidentally found intra-operatively.

Gossypiboma Transduodenal Migration Causing Partial Gastric Outlet Obstruction

The term “gossypiboma” denotes a mass of cotton that is retained in the body following surgery. It is a rare but serious complication which is seldom reported because of the medicolegal implications. Gossypiboma usually has varied and vague presentation and is also difficult to detect on radiological investigations. It can even remain silent and present years after the operation. We report a case of a 46-year-old female who presented with vague upper abdominal pain associated with postprandial fullness and occasional vomiting. She had a history of open cholecystectomy 16 years ago. Abdominal X-ray and ultrasonogram examination of the abdomen were inconclusive. Her contrast-enhanced computed tomography of the abdomen revealed thickening of the wall of the pyloric antrum with air containing thick-walled structure in relation to the pyloric antrum and the first part of the duodenum possibility of the duodenal diverticulum with inflammatory/neoplastic thickening was suggested. Her esophagogastroduodenoscopy revealed large cotton sponge embedded in the anterior wall of the first part of the duodenum. On exploratory laparotomy, she was found to have a large gossypiboma embedded in the first part of the duodenum with dense adhesions to surrounding structures. Although rare, gossypiboma should be kept in mind as a differential diagnosis in postoperative cases presenting as vague pain even years after the operation.

WELDING OF S355J+N LOW ALLOY STEEL ELEMENTS IN RAILWAY CARRIAGES STRUCTURES

Various types of structures and materials play an important role in the creation modern means of transport, including various grades of steel with different mechanical properties. For the rolling stock, proper operation and meeting the operational conditions is very important. Welded structures play an important role in the construction of various means of transport. Correct welding of carriages is important both in production and when carrying out various types of repairs. Each repair a carriage depends on its advancement and condition and the time of its operation. Each inspection for a refurbished carriage is defined either by the service life or the big distance traveled by the carriage. Important factor that may lead to damage is the effect of the load transported in the carriage. Therefore, the causes of the wear of the rolling stock are investigated and measures are taken to prevent any damage. The appropriate technical condition of the carriage also ensures safety on railroads for users and owners of the rolling stock. In the case of welded structures in carriages, it is influenced by poorly materials choice, incorrectly selected production processes and wrong selection of parameters. The goal of this paper is the mechanical properties analyse of weld low alloy steel structure of carriages after MAG welding using the parameters of the process. Thick-walled steel structures are used to build carriages, which is often a serious welding problem. The main role of welding conditions is connected with filer materials, welding technology, state of stress and temperature. In this paper, the properties of low alloy steel S3555J+N structures after MAG welding are presented. Furthermore, metallographic structure, tensile strength, bending test and impact toughness welded joints were analysed regarding welding parameters. The amount of acicular ferrite in WMD oxygen after welding was tested. Gas mixtures of argon and carbon dioxide with various percentage was used for shielding gas.

Inactivation of Escherichia coli using atmospheric pressure cold plasma jet with thin quartz tubes

In this study, the temporal evolution and electrical characteristics of atmospheric pressure cold plasma jet (APPJ) structures with different quartz tube wall thicknesses that used AC power were investigated via experimentation and simulation. The percentage increase of electron density based on the wall thickness was investigated. Based on the optimal electric field intensity distribution and flow field distribution, the quartz tube with the optimal wall thickness improved the electron density. We applied the optimized APPJ structures to inactivate E. coli. We demonstrated that the APPJ structures with thin-walled quartz tubes had better inactivation characteristics than those with thick-walled structures regardless of the duration of treatment. The electron density properties of APPJ structures with different quartz tube wall thicknesses have a prominent impact on the improvement in the killing rate in the sterilization processes.

A Novel Exact Plate Theory for Bending Vibrations Based on the Partial Differential Operator Theory

Thick wall structures are usually applied at a highly reduced frequency. It is crucial to study the refined dynamic modeling of a thick plate, as it is directly related to the dynamic mechanical characteristics of an engineering structure or device, elastic wave scattering and dynamic stress concentration, and motion stability and dynamic control of a distributed parameter system. In this paper, based on the partial differential operator theory, an exact elasto-dynamics theory without assumptions for bending vibrations is presented by using the formal solution proposed by Boussinesq–Galerkin, and its dynamic equations are obtained under appropriate gauge conditions. The exact plate theory is then compared with other theories of plates. Since the derivation of the dynamic equation is conducted without any prior assumption, the proposed dynamic equation of plates is more exact and can be applied to a wider frequency range and greater thickness.

Adult residual rectourethral fistula and diverticulum presenting decades after imperforate anus repair: a\xa0case report

BackgroundThis report describes a rare surgical case of an intraabdominal mass in a middle-aged patient 40 years after imperforate anus repair.Case presentationA 44-year-old Latino male with history of repaired anorectal malformation presented with recurrent urinary tract infections and rectal prolapse with bothersome bleeding and fecal incontinence. During his preoperative evaluation, he was initially diagnosed with a prostatic utricle cyst on the basis of magnetic resonance imaging findings, which demonstrated a cystic, thick-walled mass with low signal contents that extended inferiorly to insert into the distal prostatic urethra. However, at the time of surgical resection, the thick-walled structure contained an old, firm fecaloma. The final pathology report described findings consistent with colonic tissue, suggesting a retained remnant of the original fistula and diverticulum.ConclusionsAlthough rare, persistent rectourethral fistula tracts and rectal diverticula after imperforate anus repair can cause symptoms decades later, requiring surgical intervention. This is an important diagnostic consideration for any adult patient with history of imperforate anus.

Negative Poisson's ratio and effective Young's modulus of a vertex-based hierarchical re-entrant honeycomb structure

In this study, the mechanical properties of a vertex-based hierarchical re-entrant honeycomb structure (Hv) were investigated. Firstly, the overlapping effect of struts was considered in the calculation of the relative density. The results indicate that the overlapping has a great influence on the relative density, especially for a thick-walled structure. Secondly, the theoretical model for evaluating Young's modulus and Poisson's ratio of Hv was implemented based on Castigliano's second theorem and Timoshenko beam theory. It shows a good coincidence between the results of the finite element and theoretical models. Thirdly, based on the theoretical model, the variation of the mechanical properties of Hv with different geometric parameters was studied. The results indicate that the elastic properties of Hv can be designed by appropriately adjusting geometrical parameters. Additionally, the expressions for effective Young's modulus and Poisson's ratio of the conventional re-entrant honeycomb (Hc)* were given. Hc was compared with Hv in terms of the elastic properties by applying the same theory and calculation process. The resultant comparisons suggest that embedding a re-entrant honeycomb at the vertex of Hc is an effective way to enhance its elastic modulus and simultaneously maintain the negative Poisson's ratio in a wide range.

The laser heat-treatment process control by the non-stationary convective heat exchange modeling

Various technological processes allow to obtain high quality indicators, such as laser cutting, welding, hardening, etc. The article presents the results of modeling for laser cutting of thick-walled structures. The creation of computational tools for express analysis in a mathematical setting and a quantitative assessment of temperature fields in spatially variable and non-stationary conditions of laser exposure are of undoubted practical interest to minimize experimental costs.