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Optimization of Nonlinear Vibration Characteristics for Seismic Isolation Rubber
Get PDFA method for reducing the damage to a structure caused by an earthquake namely, using laminated rubber for seismic isolation is proposed, and the vibration characteristics of the rubber (which minimizes the seismic response of the structure during an earthquake) is optimized. A method called “Equivalent Linear System using Restoring Force Model of Power Function Type” (PFT-ELS) is applied to nonlinear vibration analysis of the rubber. In that analysis, a building with 15 layers of the laminated rubber is modeled. The seismic response of the building is analyzed, and the usefulness of the laminated rubber is demonstrated by comparing the seismic responses in the cases with and without the laminated rubber. In addition, the hysteresis restoring-force characteristic of the laminated rubber, which minimizes the seismic response of the building, was optimized by using a genetic algorithm (GA). Based on these results, the optimum restoring-force characteristic for different earthquakes was determined. As a result, it was clarified that the developed optimization method can determine the vibration characteristics of the laminated rubber for minimizing the damage to the structure in the design phase
Stability Analysis of Cross-channel Excavation for Existing Anchor Removal Project in Subway Construction
Get PDFThe cutter head will be stuck when the shield machine pass through the area existing anchor left by foundation construction of surrounding high-rise building. Subsurface excavation method is an efficient way to remove the existed anchor. In this paper, a three-dimensional finite element model is developed to study stability of cross-channel excavation. The time-spatial effects of arch crown settlement, intrados uplift and side wall horizontal convergence are analyzed according to different excavation size, lining thickness and lining order. The results show that the excavation size is the main factor to control the deformation of the surrounding soil, especially in arch crown settlement; The influence of lining thickness on the spatial effect of surrounding soil deformation is obvious when the excavation size is large, but little on the time effect; The influence of the lining order on the deformation of the surrounding soil is obvious, in particular, the larger the excavation size, the more obvious advantages of the lining order. Finally, based on the time-spatial effects comparison of nine excavation schemes of the cross-channel, an optimum excavation scheme is adopted in the actual project
Numerical Simulation of Coal Deformation and Gas Flow Properties Around Borehole for Coal and Gas Outbursts
No full textThe lack of research on the effect of diffusion on methane extraction leads to low methane concentration and low utilization. The Comsol Multiphysics software is used to solve the numerical gas and solid coupled model which considers the diffusion of coal matrix, fracture seepage, permeability evolution and coal deformation. The simulation results reveal the effect of diffusion process on methane migration. The gas diffusion rate is relatively high in the initial stage. With the increase in time, the difference between coal fractures and coal matrix blocks becomes lower and the gas diffusion rate decreases gradually. The gas seepage rate decreases significantly near the borehole and the decrease degree becomes small when it is far away from borehole. The influence of diffusion time on gas drainage rate is not obvious
Anatomical Variations in Circle of Willis and Intracranial Aneurysm Formation
Get PDFBackground: Intracranial aneurysm (IA) can be commonly found in the circle of Willis (CoW), and a higher morbidity of IA is found to be associated with a higher percentage of an incomplete CoW. Hemodynamic factors are believed to play an important role in aneurysm formation. However, how the anatomical variations in CoW lead to hemodynamic difference and what hemodynamic parameters play important roles in aneurysm formation have not been quantified and assessed. Methods and Results: Thirty patients were included and based one computed tomography angiography, they were divided into three groups (10 patients per group): a normal group (normal CoW and without aneurysms), an absence group (lacking the anterior cerebral artery and with aneurysms), and a hypoplasia group (hypoplasia of the anterior cerebral artery and with aneurysms). Patient-specific 3D models of the CoW were reconstructed by removing all the aneurysms and CFD simulations were performed on the 30 patient-specific models. Six hemodynamic parameters (blood pressure, average wall shear stress (AWSS), AWSS gradient (AWSSG), oscillatory shear index (OSI), aneurysm formation indicator (AFI), and gradient oscillatory number (GON)) were analyzed and compared between the three groups. The hypoplasia group was found to be significantly higher in AWSS (7.41±1.70vs5.44±1.31, p=0.029) and AFI (0.9959±0.0012vs0.9945±0.0011, p=0.037) than those of the normal group. Conclusions: Anatomical variation in the anterior circulation of CoW resulted in abnormal hemodynamic environment of cerebral arteries, and this may lead to formation of intracranial aneurysm. AWSS and changes in the direction of WSS may be the important hemodynamic parameters leading to aneurysm formation
Amentoflavone Suppresses Cell Growth and Invasion in Renal Carcinoma Cells by Activating PPARγ
Get PDFThis study intends to investigate the role of amentoflavone(AF) in human clear-cell renal cell carcinoma (ccRCC) and to elucidate underlying molecular mechanisms. Materials and Methods: Human RCC cell lines Caki-1 and 786-O were used in this study. Cell proliferation, apoptosis, cell cycle distribution and invasion assays were conducted to analyze the effect of AF against ccRCC in vitro. Xenograft model and pulmonary metastasis animal model were established to evaluate the vivo therapeutic efficacy and against pulmonary metastasis ability of AF, respectively. Results: Our findings revealed that AF selectively suppressed tumor cell proliferation in a dose- and time-dependent manner. Treatment with AF significantly elevated the percent proportion of apoptotic cells and blocked cell cycle progression. Moreover, AF inhibited cell invasion in a dose-dependent fashion. Our findings revealed AF activated PPARγ, which accounts for its anti-tumor activities. Conclusions: Our findings suggest AF suppresses tumor growth and metastasis by activating PPARγ
Role of Tumor Microvessel Architecture and Function in Chemotherapeutic Drug Delivery: A Three-Dimensional Numerical Study
Get PDFTo investigate the dynamic changes of solid tumor and neo-vasculature in response to chemotherapeutic agent, we proposed a multi-discipline three-dimensional mathematical model by coupling tumor growth, angiogenesis, vessel remodelling, microcirculation and drug delivery. The tumor growth is described by the cell automaton model, in which three cell phenotypes (proliferating cell, quiescent cell and necrotic cell) are assumed to reflect the dynamics of tumor progress. A 3D tree-like architecture network with different orders for vessel diameter is generated as pre-existing vasculature in host tissue. The chemical substances including oxygen, vascular endothelial growth factor, extra-cellular matrix and matrix degradation enzymes are calculated based on the reaction-diffusion equations associated with haemodynamic environment, which is obtained by coupled modelling of intravascular blood flow with interstitial fluid flow. The haemodynamic changes, including vessel diameter and permeability, are introduced to reflect a series of pathological characteristics of abnormal tumor vessels involving vessel dilation, leakage, angiogenesis, regression and collapse. The chemotherapeutic drug is transported across the vessel wall and through diffusion and convection mechanisms in the interstitial media, which is governed by the second Fick’s law. Finally, we coupled the tumor growth model and the vessel remodelling model according to the changes in the chemical and hemodynamical microenvironment, to investigate the tumor inhibition with different drug strategies. The results showed the growth histories of tumor cell population in response to chemotherapeutic agent. The efficacies of tumor inhibition by different drug strategies had been compared. In addition, we studied the influences of the pathological abnormalities of tumor microvessels, such as high density, heterogeneous capillary diameter and high permeability of vessel wall, on the drug transport and chemotherapeutic efficacy
Comparison of Right Ventricle Morphological and Mechanical Characteristics for Healthy and Patients with Tetralogy of Fallot: An In Vivo MRI-Based Modeling Study
Get PDFPatients with repaired tetralogy of Fallot (TOF) account for the majority of cases with late onset right ventricle failure. Comparing TOF patients with healthy people may provide information to address this challenge. Cardiac magnetic resonance (CMR) data were obtained from 16 TOF patients (patient group, PG) and 6 healthy volunteers (healthy group, HG). At begin-of-ejection, better patient group (n=5, BPG) stress was very close to HG stress (54.7±38.4 kPa vs. 51.2±55.7 kPa, p=0.6889) while worse patient group (n=11, WPG) stress was 84% higher than HG stress (p=0.0418). Stress may be used as an indicator to differentiate BPG patients from WPG patients, with further validations
Isocyanate-Free Polyurethanes by Coreaction of Condensed Tannins with Aminated Tannins
Get PDFIsocyanate-free polyurethane resins biosourced to a very high percentage level were prepared by the reaction of aminated mimosa tannin extract with commercial mimosa tannin extract prereacted with dimethyl carbonate. The reaction took place with ease at ambient temperature. Indications were that the polyurethanes obtained formed a hard film when cured at a temperature higher than 100 °C. Furthermore, the carbohydrate fraction of the tannin extract also appeared to be carbonated and reacted to generate isocyanate-free polyurethane linkages with the aminated tannins. This indicated that not only the polyphenolic fraction of the tannin extract, but also its other major component, can be used to prepare polyurethane resins. Flavonoid monomers and oligomers carbonated at different levels, both unreacted and urethane-linked to aminated flavonoid monomers and oligomers, were identified by FTIR and MALDI-TOF spectrometry
Polyol Preparation by Liquefaction of Technical Lignins in Crude Glycerol
Get PDFThis work reports a study of polyol synthesis through liquefaction of technical lignins in crude glycerol by means of 1H and 31P NMR spectroscopy. The polyols are intended for preparation of polyurethane foam; thus, it is important to know how different lignin types as well as crude glycerol influence and contribute to the final polyol hydroxyl contents. Polyols prepared from organosolv lignin, kraft lignin and lignosulphonate had hydroxyl numbers suitable for rigid foam of 435, 515 and 529 mgKOH/g, respectively. The polyols differed in composition with glycerol, showing significant variation. During liquefaction the glycerol content was mostly reduced through bonding with lignin, and to a lesser extent monoacylglycerol and diacylglycerol formation through transesterification with fatty acid ethyl esters. It is concluded that crude glycerol can potentially replace petroleum-derived polyols as liquefaction solvent and that different types of technical lignin have a strong impact on the resulting bio-based polyol hydroxyl contents
PLA Nanocomposites Reinforced with Cellulose Nanocrystals from Posidonia oceanica and ZnO Nanoparticles for Packaging Application
Get PDFPoly(lactic acid) (PLA) based nanocomposites reinforced with 1 wt% of surfactant-modified cellulose nanocrystals (s-CNC) extracted from Posidonia oceanica plant waste and zinc oxide nanoparticles (ZnO NPs) at different concentrations (0.1 and 0.5 wt%) were prepared by solvent casting process. Their thermal, morphological, optical, mechanical and water vapor permeability properties were investigated. Tensile testing showed increased values for strength and deformation at break in PLA based formulations reinforced with s-CNC and ZnO NPs as a consequence of better nanofiller dispersion compared to binary films reinforced only with ZnO NPs. Moreover, the effect of s-CNC and ZnO NPs provoked an improvement of barrier properties, highlighting the synergic ability of nanofillers to increase the tortuous path of gas molecules, reducing the water vapor permeability coefficients, a property of fundamental importance in food packaging applications. Finally, antimicrobial activity was evaluated using two bacterial strains, Escherichia coli and Listeria innocua