Small Wall Thickness Research Articles

Experimental investigation on the compression-bending performance of rubberized concrete columns confined by galvanized corrugated steel tubes

In the construction of building structures, numerous components simultaneously experience axial pressure and lateral bending moments. This concurrent influence plays a pivotal role in structural design considerations. This paper presents an experimental investigation of the compression-bending performance of rubberized concrete-filled corrugated steel tubes (RuCFCST). Twenty-two specimens were tested to evaluate the effect of eccentricity, length-diameter ratio, and confinement factor on the failure mode, load-displacement response, stiffness, compression-bending capacity, and ductility of the columns. The study also conducted a stress analysis on the corrugated steel tube to understand its confinement effect on the core rubberized concrete. The results demonstrate that the confinement factor emerges as a pivotal and sensitive parameter that impacts the compression-bending bearing capacity of RuCFCST columns. The study further elucidated the non-uniform confinement and failure mechanisms of the RuCFCST column, and subsequently assessed the applicability of the specimen's compression-bending bearing capacity as calculated by current specifications. The proposed RuCFCST columns offer new insights and serve as a reference for developing composite member systems with large hoop stiffness, small wall thickness, and environmental sustainability.

Mechanical performances of thin-walled high-strength concrete-filled steel tube square columns with high-strength reinforced cages under biaxial eccentric compression

In the current research that both steel tube and concrete use high-strength materials, there are few studies on the small wall thickness of steel tube exceeding the standard. In order to make full use of the mechanical properties of high-strength steel and enhance its restraint ability on concrete, this paper designs a steel cage dominated by transverse steel bars. A total of 15 square high-strength steel tube high-strength concrete medium-long column test pieces are tested and studied. The main parameters of the specimens are slenderness ratio, loading eccentricity and the form of internal steel reinforcement cage. After the loading test, according to the test results, the failure mode of the specimen is obtained and the mechanical properties of middle-long concrete-filled steel tubular columns are analyzed. The research results show that the ultra-thin high-strength steel pipe can restrain concrete well, but with the increase of eccentricity, its restraint capacity is slightly insufficient; the built-in steel cage can slow down the bulging of the specimen and help the steel pipe to further strengthen the restraint on concrete, but the steel cage as an indirect constraint cannot avoid the final bulging damage. Due to the existing formula overestimating the effect of ultra-thin steel tubes, this paper proposes a calculation formula for the axial compression of thin-walled high-strength concrete-filled steel tubes with steel cage short columns. Based on this method, the bearing capacity of medium-long columns under biaxial eccentric compression is calculated with good accuracy.

Pathology-based brain arterial disease phenotypes and their radiographic correlates

IntroductionBrain arterial diseases, including atherosclerosis, vasculitis, and dissections, are major contributors to cerebrovascular morbidity and mortality worldwide. These diseases not only increase the risk of stroke but also play a significant role in neurodegeneration and dementia. Clear and unambiguous terminology and classification of brain arterial disease phenotypes is crucial for research and clinical practice. Material and methodsThis review aims to summarize and harmonize the terminology used for brain large and small arterial phenotypes based on pathology studies and relate them to imaging phenotypes used in medical research and clinical practice. Conclusions and resultsArteriosclerosis refers to hardening of the arteries but does not specify the underlying etiology. Specific terms such as atherosclerosis, calcification, or non-atherosclerotic fibroplasia are preferred. Atherosclerosis is defined pathologically by an atheroma. Other brain arterial pathologies occur and should be distinguished from atherosclerosis given therapeutic implications. On brain imaging, intracranial arterial luminal stenosis is usually attributed to atherosclerosis in the presence of atherosclerotic risk factors but advanced high-resolution arterial wall imaging has the potential to more accurately identify the underlying pathology. Regarding small vessel disease, arteriosclerosis is ambiguous and arteriolosclerosis is often used to denote the involvement of arterioles rather than arteries. Lipohyalinosis is sometimes used synonymously with arteriolosclerosis, but less accurately describes this common small vessel thickening which uncommonly shows lipid. Specific measures of small vessel wall thickness, the relationship to the lumen as well as changes in the layer composition might convey objective, measurable data regarding the status of brain small vessels.

Differential expression of mast cells in the small airways and alveolar septa of current smokers and patients with small airway disease and COPD.

COPD patients suffer from dysregulated and suppressed immune functionality, determined by their loss of degranulating capacity. Here we provide crucial information on the presence of degranulated mast cells (MCs) in COPD airways and demonstrate their relationship to lung physiology and airway remodelling. Small airway lung resections from non-smoking controls (NC), normal lung function smokers (NLFS), small airway disease (SAD), and mild-to-moderate COPD current smokers (COPD-CS) and ex-smokers (COPD-ES) were dual immuno-stained with MC tryptase and degranulation marker lysosome-associated membrane protein (LAMP)-1. Total MCs, degranulating MCs and non-MCs were enumerated in small airway epithelium and subepithelium, and in alveolar septa. In the small airway wall subepithelial areas, COPD-CS and COPD-ES patients had significantly lower MCs than the NC group (p<0.05), although the numbers were considerably higher in the small airway epithelium (p<0.01). Degranulating non-MCs were higher in SAD (p<0.05) than in COPD in the small airway subepithelium. In contrast, there were significant increases in total MCs (degranulated and non-degranulated) and degranulated non-MCs in the alveolar septum of COPD patients compared with the NC group (p<001). The lower numbers of MCs in the subepithelium correlated with lower forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) and forced expiratory flow at 25-75% of FVC (FEF25-75%), higher smoking rates in COPD patients, and increased small airway wall thickness and extracellular matrix. The increase in MCs in the alveolar septum negatively correlated with FEF25-75%. This study is the first to assess the differential pattern of MC, degranulating MC and non-MC populations in the small airways and alveoli of COPD patients. The spatial positioning of the MCs within the airways showed variable correlations with lung function.

Small airways morphological alterations associated with functional impairment in lymphangioleiomyomatosis

BackgroundLymphangioleiomyomatosis (LAM) is a rare neoplastic and cystic pulmonary disease characterized by abnormal proliferation of the so-called LAM cells. Despite the functional obstructive pattern observed in most patients, few studies investigated the morphological changes in the small airways, most of them in patients with severe and advanced LAM undergoing lung transplantation. Understanding the morphological changes in the airways that may occur early in the disease can help us understand the pathophysiology of disease progression and understand the rationale for possible therapeutic approaches, such as the use of bronchodilators. Our study aimed to characterize the morphological alterations of the small airways in patients with LAM with different severities compared to controls, and their association with variables at the pulmonary function test and with LAM Histological Score (LHS).MethodsThirty-nine women with LAM who had undergone open lung biopsy or lung transplantation, and nine controls were evaluated. The histological severity of the disease was assessed as LHS, based on the percentage of tissue involvement by cysts and infiltration by LAM cells. The following morphometric parameters were obtained: airway thickness, airway closure index, collagen and airway smooth muscle content, airway epithelial TGF-β expression, and infiltration of LAM cells and inflammatory cells within the small airway walls.ResultsThe age of patients with LAM was 39 ± 8 years, with FEV1 and DLCO of 62 ± 30% predicted and 62 ± 32% predicted, respectively. Patients with LAM had increased small airway closure index, collagen and smooth muscle content, and epithelial TGF-beta expression compared with controls. Patients with LAM with the more severe LHS and with greater functional severity (FEV1 ≤ 30%) presented higher thicknesses of the airways. Bronchiolar inflammation was mild; infiltration of the small airway walls by LAM cells was rare. LHS was associated with an obstructive pattern, air trapping, and reduced DLCO, whereas small airway wall thickness was associated with FEV1, FVC, and collagen content.ConclusionLAM is associated with small airway remodelling and partial airway closure, with structural alterations observed at different airway compartments. Functional impairment in LAM is associated with airway remodelling and, most importantly, with histological severity (LHS).

On the Similarity Relationship between the Structural-Steel Prototype and the 304-Stainless-Steel Dynamic Scale Model

Due to the size limitations of shaking tables, dynamic scale models of large-span space structures for engineering have small cross-sections and thin wall thicknesses. It is difficult to use the structural steels commonly used in prototypes to make dynamic scale models. In this paper, 304 stainless steel is proposed for making the scale model, and the similarity relationship between the structural-steel prototype and the 304-stainless-steel dynamic scale model was studied. Firstly, a uniaxial test was conducted to study the elastic modulus similarity and the yielding stress similarity. The test results demonstrated that the elastic modulus similarity ratio was 1:1, and the stress similarity ratios of the 304 stainless steel and the three typical structural steels were 1:1 (Q235 steel), 1:1.5 (Q355 steel) and 1:1.8 (Q420 steel). Then, the similarities of other variables were derived using the dimensional analysis method. In the end, a numerical analysis was conducted to verify the similarity relationship between the structural-steel prototype and the 304-stainless-steel dynamic scale model. In the numerical analysis, a single-layer spherical reticulated shell structure and a dynamic scale model with a length similarity ratio of 1:20 were established by using the ABAQUS 2021 software, and the node displacement, the element internal force and natural vibration characteristics were analyzed. The results show that standard deviations of the displacements, the internal forces and the natural vibration frequencies between the prototype and the scale model were within 5%. It turns out that the proposed similarity between the structural-steel prototype and the 304-stainless-steel dynamic scale model was applicable in the elastic stage. The findings provide a reference for designing a dynamic scale model of large-span space structures for engineering by using 304 stainless steel.

Evaluation of small bowel wall thickness with double balloon enteroscopy

Objectives: Double balloon enteroscopy (DBE) is an endoscopic method used for the evaluation of small bowel segments. Its advantage over other small bowel evaluation methods is that it allows treatment in addition to the detection of lesions. In this study, we evaluated the results of patients with small bowel abnormalities, especially wall thickness, on radiologic imaging who underwent double-balloon enteroscopy.&#x0D; Methods: The data of patients who were found to have wall thickness and stenosis in the small intestine on radiological imaging and who underwent DBE between January 2007 and December 2018 at Ankara City Training and Research Hospital were retrospectively analyzed. Patients with inadequate endoscopic images or medical records were excluded from this study.&#x0D; Results: The study included 112 patients. Of the patients, 69 (61.6%) were male and 43 (38.4%) were female. The mean age of the population was 45.59 ± 17 years. Abdominal pain was the main presenting symptom. The procedure was performed anterograde (oral) in 79 patients, retrograde (anal) in 25 patients, and both approaches in 8 patients. Various complications developed after 20 procedures, and no mortality was observed. Radiologically, small bowel wall thickness was most commonly detected on computed tomography, and the majority of the lesions detected were in the jejunum (63.9%). In 48 DBE procedures, no lesion was detected in the small intestine. The ulcer was the most common lesion detected during DBE (25.6%), and the majority were detected in the ileum. Crohn's disease was the most common pathology detected in the samples. Malignancy was the second most common pathology, and jejunal lymphoma was the most common malignancy.&#x0D; Conclusion: DBE should be used more frequently in clinical practice to evaluate radiologically detected small bowel lesions because of the possibility of biopsy and its high diagnostic accuracy.

Numerical simulation and experimental investigation for the dynamic rocking response of two stacked rigid blocks

A system of two stacked rigid blocks (TSRBs), such as a statue on a pedestal, is extensively constructed and utilized. However, the numerical simulation of its dynamic response has been a crucial and challenging problem due to the diversity of motion patterns and the nonlinearity in the impacts. Therefore, a high-accuracy and appropriate numerical simulation approach for solving the rocking response of TSRBs was proposed in this paper. First, their rocking patterns were presented, and the judgment diagram of their transitions was defined. Then, the rocking equations of the motion and the formulas of the post-impact angular velocities were introduced. Next, to solve the rocking response of TSRBs, a novel numerical method stemming from the Rosenbrock method and the substep-two-step method was proposed and preliminarily verified. Moreover, free and forced vibration experiments were conducted to verify its accuracy further, and the regularity of the motion was summarized. Finally, parametric analyses of the applications was performed on statue-pedestal systems to investigate the influence of the wall thicknesses and height-to-width ratios of the pedestals on the dynamic response. The results indicate that the proposed method has favorable stability, acceptable accuracy, and high computational efficiency due to its accurate impact point identification and rocking pattern determination. In practice, to reduce the dynamic response of statues, it is preferred to place pedestals with smaller wall thicknesses and larger height-to-width ratios under statues.

Optimization analysis of variable gradient structures with shape memory characteristics in zero poisson’s ratio metamaterials

Mechanical metamaterials can achieve fantastic properties fabricated using artificial structural design. In this study, shape memory polymers (SMP) were combined to design variable gradient zero Poisson ratio mechanical metamaterials and 3D printing was used to fabricate complex structures. The shape memory performance of these structures was investigated by conducting simulation calculations to analyze the variations of zero Poisson’s ratio structures with different wall thicknesses, cell internal angles, and inclined wall length gradients. Through the analysis of structural dimension factors, it is concluded that the structures with smaller wall thickness and intracellular angle exhibit better shape memory performance. In order to further enhance the shape memory performance, several models with identical wall thickness and internal angles were designed to investigate the influence of inclined wall length gradients on shape memory characteristics, leading to the identification of optimal gradient structures. Finally, thermal cycling experiments were conducted on samples to validate the accuracy of the simulation results. The investigation of shape memory recovery characteristics in variable gradient zero Poisson’s ratio structures provides new insight and method for the optimization design and application of smart materials in mechanical metamaterial structures.

Методика расчета толщины стенки лепестка манжетного цилиндропоршневого уплотнения

The presented article describes a method for calculating the wall thickness of the lip seal lobe in the ANSYS Workbench Mechanical software package. The main problem that designers face when choosing the wall thickness of the lobe of cuff seals for reciprocating compressor units operating without lubrication is described. As a result of the work, the maximum and minimum wall thickness are calculated for the materials most common in oil-free compressor units. Antifriction materials of the Flubon and Fluvis groups containing up to 20 % carbon fibers have the smallest wall thickness in all pressure ranges considered. At the same time, the results obtained allow us to speak about the low efficiency of cuff seals with a maximum wall thickness at pressures below 1 MPa.

Evaluation of the findings affecting the treatment decision in cases of adhesive intestinal obstruction

To establish a standard approach in patient management by determining the parameters that affect the decision of surgical or conservative treatment in adhesive small bowel obstructions. 94 patients who were admitted to the emergency department with symptoms of ileus and were diagnosed with adhesive intestinal obstruction according to clinical, examination and imaging findings were grouped as patients who were followed up with conservative methods (Group 1) and patients who underwent surgery (Group 2). All patients' laboratory values (hemoglobin, white blood cell (WBC), C- reactive protein (CRP), Blodd urea nitrogen (BUN)/creatinin, sodium, potassium, Lactate dehydrogenase (LDH), lactate and amylase) and imaging findings (air-fluid level in direct abdominal X-ray, increase in small intestine diameter (≥3.95 cm) in computerized tomography), wall thickness increase (&gt;3mm), transition zone, fecal sign, and presence of contrast in the colon) were evaluated, and criteria for early surgery and non-operative follow-up-treatment criteria were determined. 72% (n:68) of the patients were classified as Group 1 and 28% (n:26) as Group 2, and no significant difference was found between the groups according to age and gender. Surgical treatment with increased lactate (r:0.326, p=0.001), diameter increase in the small intestine (r:0.299, p=0.003) and wall thickness increase (r:0.540, p&lt;0.001), change in air-fluid levels on direct X-ray ( A significant correlation was found between r:-0.291, p=0.004) and contrast transfer to the colon on tomography (r:-0.668, p&lt;0.001) and the decision for conservative treatment. Although adhesive intestinal obstruction is a condition that can mostly be managed non-operatively, the early surgical decision significantly reduces mortality and morbidity in cases with an operation indication. It was concluded that the standard approach protocol based on laboratory and imaging findings determined in the non-operative or operative treatment management helps in the differential diagnosis and early surgical decision and reduces the length of stay of the patient.

High Throughput Omnidirectional Printing of Tubular Microstructures from Elastomeric Polymers.

Bioelastomers are extensively used in biomedical applications due to their desirable mechanical strength, tunable properties, and chemical versatility; however, three-dimensional (3D) printing bioelastomers into microscale structures has proven elusive. Herein, a high throughput omnidirectional printing approach via coaxial extrusion is described that fabricates perfusable elastomeric microtubes of unprecedently small inner diameter (350-550µm) and wall thickness (40-60µm). The versatility of this approach is shown through the printing of two different polymeric elastomers, followed by photocrosslinking and removal of the fugitive inner phase. Designed experiments are used to tune the microtube dimensions and stiffness to match that of native ex vivo rat vasculature. This approach affords the fabrication of multiple biomimetic shapes resembling cochlea and kidney glomerulus and affords facile, high-throughput generation of perfusable structures that can be seeded with endothelial cells for biomedical applications. Post-printing laser micromachining is performed to generate micro-sized holes (520µm) in the tube wall to tune microstructure permeability. Importantly, for organ-on-a-chip applications, the described approach takes only 3.6min to print microtubes (without microholes) over an entire 96-well plate device, in contrast to comparable hole-free structures that take between 1.5 and 6.5days to fabricate using a manual 3D stamping approach.

Influence of layer thickness on formation quality, microstructure, mechanical properties, and corrosion resistance of WE43 magnesium alloy fabricated by laser powder bed fusion

Laser powder bed fusion (L-PBF) of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts. Layer thickness (LT) is of great significance to the L-PBF process but has not been studied for Mg alloys. In this study, WE43 Mg alloy bulk cubes, porous scaffolds, and thin walls with layer thicknesses of 10, 20, 30, and 40 μm were fabricated. The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds. Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input. For thin wall parts, a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used, and the porosity disappeared by reducing the layer thickness or laser energy input. A deeper keyhole penetration was found in all occasions with porosity, explaining the influence of layer thickness, geometrical structure, and laser energy input on the porosity. All the samples achieved a high fusion quality with a relative density of over 99.5% using the optimized laser energy input. The increased layer thickness resulted to more precipitation phases, finer grain sizes and decreased grain texture. With the similar high fusion quality, the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41% with the 10 μm layer to 287 MPa and 15.12 % with the 40 μm layer, in accordance with the microstructural change. The effect of layer thickness on the compressive properties of porous scaffolds was limited, however. The corrosion rate of bulk samples accelerated with increasing the layer thickness, mainly attributed to the increased number of precipitation phases.

Expression Profile of IL-17 in lung tissues of patients with lung cancer and COPD and clinical significance

The purpose of this experiment to analyze the expression and clinical significance of interleukin-17 (IL-17) in lung tissue of lung cancer patients with chronic obstructive pulmonary disease (COPD). For this aim, 68 patients with lung cancer and chronic obstructive pulmonary disease who were admitted to our hospital from February 2020 to February 2022 were selected as the research objects of the study group. The specimens were fresh lung tissue obtained after lobectomy; In addition, 54 healthy subjects were selected as the control group during the same period, and fresh lung tissue obtained by minimally invasive lung volume reduction was selected as the sample. The clinical baseline data of the two groups were observed and compared. The mean alveolar area, small airway inflammation score and Ma tube wall thickness were measured. The expression of IL-17 was detected by immunohistochemistry. Results showed that gender, average age and average body mass index of the two groups (P > 0.05); At present, the proportion of smokers, pulmonary artery systolic pressure, PaCO2 level and CRP level in the study group are high, PaO2 level, FEV1% predicted value, FEV1 / FVC and FIB level are low, and the number of acute exacerbations in the past year is high (P > 0.05). In the study group, the average alveolar area, the thickness of the Ma tube wall, the lymphocyte infiltration score of the tracheal wall and the total pathological score of the small airway were higher (P > 0.05). The expression of IL-17 in the airway wall and lung parenchyma was higher in the study group (P > 0.05). IL-17 expression in lung tissue of lung cancer patients with COPD was positively correlated with body mass index, and negatively correlated with CRP, FIB, FEV1% predicted value and the number of acute exacerbations in the past year; CRP and the number of acute exacerbations in the past year were independent variables and independent influencing factors of IL-17 expression (P < 0.05). In conclusion, IL-17 is highly expressed in the lung tissues of patients with lung cancer and COPD, which may play an important role in the occurrence and development of the disease.

High Quality and Maximizing the Production of CNTs from the Pyrolysis of Waste Polypropylene

Thermal decomposition of plastics by pyrolysis into oil is a successful way of treating wastes. Nevertheless, the production of carbon nanotubes (CNTs) from wastes improves the feasibility of the waste management process. An experimental setup was developed to study the influence of different heating rates on the produced oil by pyrolysis of waste polypropylene (WPP), and the influence of using foamed nickel on the produced CNTs as a function of operating temperature and heating rate. Different heating rates of 5, 10, and 20 °C/min were examined, as well as the different carbon vapor deposition (CVD) temperatures of 600, 700, and 800 °C were studied. It has been found that increasing the heating rate from 5 to 20 °C/min increases the oil yield from 59.3 to 71%, but on the other hand it decreases the quality of the oil. It has been also found that increasing the heating rate decreases the quality of CNTs, i.e., uniform CNTs with small diameter and small wall thickness, and as well as the quantity. The physical properties of the produced CNTs have been improved by increasing the CVD temperature; however, the quantity of CNTs decreased. The highest yield of CNTs produced was 43.12% at the lowest CVD temperature and heating rate examined, i.e., 600 and 5 °C/min, respectively. The optimum heating rate and CVD temperature for the pyrolysis of waste polypropylene to achieve the highest quality of CNTs with moderate production of 39.34%, is the lowest heating rate examined, i.e., 5 °C/min, with a moderate CVD temperature of 700 °C.

A Fabry–Pérot interferometer strain sensor composed of a rounded rectangular air cavity with a thin wall for high sensitivity and interference contrast

A Fabry–Pérot interferometer (FPI) strain sensor with high sensitivity and interference contrast is designed and fabricated by a simple, cost effective, and safe process which can be scaled up for commercial production. The excellent strain sensitivity of 8 pm/μɛ and interference contrast of 25 dB stem from the special structure with the unique air cavity, small wall thickness, and excellent reflection surface of the air cavity. The strain-temperature cross-sensitivity of the sensor is only 0.59 μɛ/°C in the temperature range of 20–80°C. The sensor has large potential in applications such as strain sensing.

Unsteady stretching of a glass tube with internal channel pressurization

Mathematical modeling is used to examine the unsteady problem of heating and pulling an axisymmetric cylindrical glass tube with an over-pressure applied within the tube to form tapers with a near uniform bore and small wall thickness at the tip. To allow for the dependence of viscosity on temperature, a prescribed axially varying viscosity is assumed. Our motivation is the manufacture of emitter tips for mass spectrometry which provide a continuous fluid flow and do not become blocked. We demonstrate, for the first time, the feasibility of producing such emitters by this process and examine the influence of the process parameters, in particular the pulling force and over-pressure, on the geometry. There is not a unique force and over-pressure combination to achieve the desired geometry at the tip but smaller over-pressure (hence force) yields a more uniform bore over the entire length of the emitter than does a larger over-pressure (and force). However, the sensitivity of the geometry to small fluctuations in the parameters increases as the over-pressure decreases. The best parameters depend on the accuracy of the puller used to manufacture the tapers and the permissible tolerances on the geometry. The model has wider application to the manufacture of other devices.

Quality of automotive sand casting with different wall thickness from progressive secondary alloy

Abstract This paperwork is focused on the quality of AlSi6Cu4 casting with different wall thicknesses cast into the metal mold. Investigated are structural changes (the morphology, size, and distribution of structural components). The quantitative analysis is used to numerically evaluate the size and area fraction of structural parameters (α-phase, eutectic Si, intermetallic phases) between delivered experimental material and cast with different wall thicknesses. Additionally, the Brinell hardness is performed to obtain the mechanical property benefits of the thin-walled alloys. This research leads to the conclusion, that the AlSi6Cu4 alloy from metal mold has finer structural components, especially in small wall thicknesses, and thus has better mechanical properties (Brinell hardness). These secondary Al-castings have a high potential for use in the automotive industry, due to the thin thicknesses and thus lightweight of the construction.

Dynamic analysis of 10 MW offshore wind turbines with different support structures subjected to earthquake loadings

This paper investigates the structural dynamics of 10 MW offshore wind turbines (OWTs) supported by different substructures (Monopile, Tripod and Jacket) under wind, wave, current and earthquake loadings. The support structures are modeled using ANSYS, a finite element models (FEM) software package, by considering the nonlinear soil structure interaction (SSI) effects and earthquake loadings. A spring-displacement method has been employed to model the earthquake excitations on the support structures. FAST and AQWA tools have been used to analyze wind and wave loads which are fed into ANSYS via a dynamic link library (DLL) as external loads for combination with the earthquake loads to predict the support structures’ responses. Earthquakes of different magnitudes have been simulated in the study. Under the earthquake with a magnitude of 7 measured on a Richter scale, the tower top displacements of the tripod, jacket and monopile are 1.42 m, 1.75 m and 1.80 m, respectively. The relative position of the displacement trajectory of the tripod OWT is nearest to the centroid of the yaw bearing. The maximum stresses of the jacket and tripod are respectively 5.7 times and 2.3 times that of the monopile. The average stress of the jacket and tripod are respectively 0.74 times and 0.56 times that of the monopile. This phenomenon shows that the tripod and jacket have a good stability, but with a high risk of local failure under earthquakes. The responses of the piles are mainly dominated by the seismic loads, rather than the wind and current loads. It was observed that the piles of the jacket and tripod OWT, which have small diameters and thin wall thickness, are more sensitive to earthquakes. Thus, the jacket and tripod OWTs may rely on the large stiffness offered by substructures to improve their stability. These phenomena can provide powerful insight into the seismic design of different substructures.

Effects of Operating Conditions during Three-Layered Polymeric Balloon Catheter Extrusion

Multilayered balloon catheters are attracting more attention in recent years. Multilayered balloon catheters have some unique properties such as meso-/microscale dimensions, small wall thickness, and strict requirements of dimensional accuracy. In this study, three-layered polymeric balloon catheters composed of polyamide, ethylene vinyl acetate, and polypropylene (PA/EVA/PP) are successfully fabricated using a three-layered coextrusion die and the polymer melt flowing behavior through the extrusion die are analyzed. Both the diameter and wall thicknesses have been selected as the targeted structural parameters to investigate the effects of pulling speed, air injection volume rate, and screw speed on the quality of the extrudates. The optimal combination of these three operating conditions has been achieved. It is found that pulling speed can significantly affect the diameters of the extruded balloon catheters. The variation interval values of outer profile diameter and inner cavity diameter with the extrusion experiments are 20.95% and 13.04%, respectively. The screw speed of each layer has a great influence on the wall thickness of each layer. Through the influence of outer screw speed, middle screw speed and inner screw speed, the variation interval values for outer layer wall thickness, middle layer wall thickness, and inner layer wall thickness are 31.06%, 35.69%, and 31.35%, respectively. The air injection volume rate has negligible effect.