Development of Finite Element Techniques to Simulate Concrete-Filled Fiber-Reinforced Polymer Tube Structures

This dissertation presents the development of finite-element (FE) techniques to simulate the behavior of concrete-filled fiber reinforced polymer (FRP) tubes (CFFTs) in support of more effective structural design and analysis methods for buried composite arch bridges (BCABs) that use CFFT arches as main structural members. The research includes three specific topics to make contributions in different aspects of the investigation of these complex structures. The first topic is the nonlinear three-dimensional FE modeling of steel-free CFFT splices. For model validation, comparisons were made between the model predictions and control beam and spliced beams with and without internal collars tested by others. The modeling was complex due to the need to capture the nonlinear constitutive response of the confined concrete, simulate concrete-FRP interaction, and explicitly incorporate the splice components. Therefore, the numerical analysis utilized the Abaqus/CAE software package with a modified damage concrete plasticity model to idealize the concretefill. The second topic of this research is the development of a computationally efficient structural FE analysis technique for the second-order inelastic behavior of these CFFT arches that includes initial arch curvature. A curved, planar, corotational, flexibility-based (FB), layered frame element is employed to handle geometric and material nonlinearities. An FRP-confined concrete stress-strain model that explicitly considers the effect of dilation of the concrete core and confinement provide by the FRP tube is implemented. Verification of the FB formulation was carried out for elastic-plastic analysis of a beam and elastic post-buckling analysis of a circular arch. The measured flexural responses of different isolated CFFT arches available in the literature were used to verify the proposed model. The model was shown to accurately predict the load-carrying capacity and ductility of the tested CFFT arches. The model captured arch collapse mechanisms arising from FRP rupture and concrete crushing at the apex of the arches. The third topic is an extension of the planar FB model to three-dimensions and incorporation of a soil-spring model to simulate soil-structure interaction using a recently developed horizontal earth pressure model. The model rigorously incorporates the interaction between axial load and bending effects in the arches and permits the examination of out-of-plane stability and arch deformations due to bridge skew. Parametric studies were conducted to assess the effect of abutment skew angle on the behavior of CFFT arch bridge components, an important practical design consideration

Differential Effects of Race and Poverty on Ambulatory Care Sensitive Conditions

This study is a continuation of an earlier study that examined hospitalization rates for ambulatory care sensitive (ACS) conditions, as a proxy for quality of care, and found evidence of a racial disparity among African American and White Medicare beneficiaries. The current study sought to determine whether neighborhood socioeconomic status (SES) explained this disparity. Differences in rates of ACS hospitalizations by race were assessed using Cochran-Mantel Haenszel tests and Poisson regression. Unadjusted rate ratios for ACS hospitalization for African Americans vs. Whites were found to be higher in low poverty areas (rate ratio (RR)=1.13; 95% CI (1.08, 1.17)) than in high poverty areas (RR=0.97; 95% CI (0.89, 1.05)). After controlling for various indicators of area SES in multivariate analyses race differences in ACS hospitalization rates persisted. Rural neighborhoods and those with higher percent of non-high school graduates were associated with greater risk of ACS hospitalizations

Preparing and Studying Structural and Optical Properties of Pb1-xCdxS Nanoparticles of Solar Cells Applications

تم تحضير الجسيمات النانوية لـ Pb1-xCdxS ضمن تركيبة x≤1≤0 من تفاعل المحلول المائي لأسيتات الكادميوم ، أسيتات الرصاص ، ثيوريا ، و NaOH بواسطة الترسيب الكيميائي المشترك. تميزت العينات التي تم تحضيرها بواسطة التحليل الطيفي للأشعة فوق البنفسجية (في نطاق 300-1100 نانومتر) لدراسة الخواص الضوئية و AFM و SEM للتحقق من و Pb0.75 Cd0.25 و Pb0.5Cd0.5S و Pb0.25Cd0 75S ، و CdS على التوالي ، ونقاء المرحلة. تشير النتائج إلى أن البنية البلورية لجميع العينات المحضرة هي مكعبة باستثناء CdS التي تظهر بنية سداسية شكل السطح (متوسط الخشونة والشكل) وحجم الجسيمات. تم استخدام تقنية XRD لتحديد البنية البلورية ، ومتوسط الحجم البلوري للجسيمات النانوية والتي هي 20.7 و 15.48 و 11.9 و 11.8 و 13.65 نانومتر لـ PbS ومكعبة ، وكان حجم الجسيمات (النطاق بين 64.81 إلى 91.14 نانومتر) في المدى النانوي ، ولها درجة نقاء عالية.Nanoparticles of Pb1-xCdxS within the composition of 0≤x≤1 were prepared from the reaction of aqueous solution of cadmium acetate, lead acetate, thiourea, and NaOH by chemical co-precipitation. The prepared samples were characterized by UV-Vis spectroscopy(in the range 300-1100nm) to study the optical properties, AFM and SEM to check the surface morphology(Roughness average and shape) and the particle size. XRD technique was used to determine the crystalline structure, XRD technique was used to determine the purity of the phase and the crystalline structure, The crystalline size average of the nanoparticles have been found to be 20.7, 15.48, 11.9, 11.8, and 13.65 nm for PbS, Pb0.75Cd0.25S, Pb0.5Cd0.5S, Pb0.25Cd0.75S, and CdS respectively. The results indicate that crystalline structure of all prepared samples is cubic except CdS which shows hexagonal and cubic structure. The particle size was found within the range of (64.81 to 91.14) nm, with a high purity

1-Hydroxy Ethylidene 1,1-Diphosphonic Acid (HEDP) as a Corrosion Inhibitor for Aluminium

The present study is to use 1-hydroxy ethylidene 1, 1-diphosphonic acid (HEDP) as corrosion inhibitor for aluminium in aqueous solution containing 60 ppm Cl- ion was chosen as the inhibitor. Zn2+ is selected as the synergist, as Zn2+ ions in association with HEDP inhibitor is considered environmental friendly inhibitor for aluminium corrosion in alkaline (pH=11) media. The environment chosen is aqueous solution containing 60 ppm Cl- ions. To investigate the nature of the protective film, surface analytical techniques such as, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) have been put to use in the present study. The formation of protective film has been confirmed using the electrochemical techniques such as polarization study and AC impedance spectral study. The above studies support the weight loss study

ANALYSIS OF CURRENT HARMONICS IN A DECOUPLED SVPWM CONTROLLED DUAL TWO LEVEL INVERTER FED OPEN END WINDING INDUCTION MOTOR DRIVE

Pulse width modulation has been one of the most intensively investigated areas of power electronics for many years now, and the number of combinations seems to be endless. However, according to a hierarchal consensus, Space Vector Modulation techniques are ranked higher in order of merit, based on harmonic performance. In this paper, Space Vector PWM Switching scheme is employed for a dual two level inverter feeding an Induction motor from both ends (open end winding). The decoupled SVPWM is employed for the dual-inverter scheme in order to realize the reference voltage vector. The Gating pulses are correspondingly generated for the dual inverters in order to realize the reference voltage, and the respective voltages are fed to 1kW open end windings of an induction motor drive. The harmonic content of the three phase currents in the motor are analyzed with an appropriate variation in its modulation index. Thus the performance in terms of harmonic analysis is carried out using Matlab/SIMULINK for an open end winding induction motor drive

Study on the design and operation of a traditional winch in fishery technology

Majority of the non-mechanized craft in Karnataka are wooden and they are operated mainly in beach landing centers which hardly have any berthing facility. These boats are operating on daily basis and are hauled on to the beach after the operatio to protect it from fouling organisms. The fishermen of Karnataka came up with the idea of wooden winch/ capstan named “Dhowr” for hauling the boat on shore. The following paper documents and report for the first time, the use of such unique, eco-friendly wooden capstan, “Dhowr” which is in operation in traditional beach landing fishing village of Karnataka

Peristaltic Transport of a Physiological Fluid in an Asymmetric Porous Channel in the Presence of an External Magnetic Field

The paper deals with a theoretical investigation of the peristaltic transport of a physiological fluid in a porous asymmetric channel under the action of a magnetic field. The stream function, pressure gradient and axial velocity are studied by using appropriate analytical and numerical techniques. Effects of different physical parameters such as permeability, phase difference, wave amplitude and magnetic parameter on the velocity, pumping characteristics, streamline pattern and trapping are investigated with particular emphasis. The computational results are presented in graphical form. The results are found to be in perfect agreement with those of a previous study carried out for a non-porous channel in the absence of a magnetic field

Portal vein embolization versus dual vein embolization for management of the future liver remnant in patients undergoing major hepatectomy: meta-analysis

BACKGROUND: This meta-analysis aimed to compare progression to surgery, extent of liver hypertrophy, and postoperative outcomes in patients planned for major hepatectomy following either portal vein embolization (PVE) or dual vein embolization (DVE) for management of an inadequate future liver remnant (FLR). METHODS: An electronic search was performed of MEDLINE, Embase, and PubMed databases using both medical subject headings (MeSH) and truncated word searches. Articles comparing PVE with DVE up to January 2022 were included. Articles comparing sequential DVE were excluded. ORs, risk ratios, and mean difference (MD) were calculated using fixed and random-effects models for meta-analysis. RESULTS: Eight retrospective studies including 523 patients were included in the study. Baseline characteristics between the groups, specifically, age, sex, BMI, indication for resection, and baseline FLR (ml and per cent) were comparable. The percentage increase in hypertrophy was larger in the DVE group, 66 per cent in the DVE group versus 27 per cent in the PVE group, MD 39.07 (9.09, 69.05) (P = 0.010). Significantly fewer patients failed to progress to surgery in the DVE group than the PVE group, 13 per cent versus 25 per cent respectively OR 0.53 (0.31, 0.90) (P = 0.020). Rates of post-hepatectomy liver failure 13 per cent versus 22 per cent (P = 0.130) and major complications 20 per cent versus 28 per cent (Clavien–Dindo more than IIIa) (P = 0.280) were lower. Perioperative mortality was lower with DVE, 1 per cent versus 10 per cent (P = 0.010). CONCLUSION: DVE seems to produce a greater degree of hypertrophy of the FLR than PVE alone which translates into more patients progressing to surgery. Higher quality studies are needed to confirm these results

'Dhowr'- A Revisit to the design and operation of indigenous machinery in fishery technology

Traditionally, the fishing crafts are hauled on to the beach with manpower after the fishing cruise. Many of the beach-landing centers use manpower for hauling the boats. But the change in beach profile due to changing weather condition makes it extremely cumbersome for hauling the boat using manpower alone. Moreover, the labour force has also been getting scarce in many fishing villages. A wooden winch was developed by the fishermen of Dakshina Kannada, several decades back. The fishermen in Keni Village of Uttar Kannada District worked on this insight and came out with a modified manually working wooden winch/ capstan and named “Dhowr”. This device was widely accepted and number of units came up in most of the beach landing fishing villages of Uttar Kannada. With this background, it was felt necessary that a detailed study be conducted to document and report the construction and operation of unique and eco-friendly wooden capstan, “Dhowr” along with the benefits to the fishermen