Search results for "Mechanical engineering"
showing 10 items of 4245 documents
Boundary elements analysis of adhesively bonded piezoelectric active repair
2009
Abstract This paper presents the analysis of active piezoelectric patches for cracked structures by the boundary element method. A two-dimensional boundary integral formulation based on the multidomain technique is used to model cracks and to assemble the multi-layered piezoelectric patches to the host damaged structures. The fracture mechanics behavior of the repaired structures is analyzed for both perfect and imperfect interface between patches and host beams. The imperfect interface, representing the adhesive between two different layers, is modeled by using a “spring model” that involves linear relationships between the interface tractions, in normal and tangential directions, and the …
Measurement of Mechanical Properties of Cantilever Shaped Materials
2008
Microcantilevers were first introduced as imaging probes in Atomic Force Microscopy (AFM) due to their extremely high sensitivity in measuring surface forces. The versatility of these probes, however, allows the sensing and measurement of a host of mechanical properties of various materials. Sensor parameters such as resonance frequency, quality factor, amplitude of vibration and bending due to a differential stress can all be simultaneously determined for a cantilever. When measuring the mechanical properties of materials, identifying and discerning the most influential parameters responsible for the observed changes in the cantilever response are important. We will, therefore, discuss the…
Numerical and experimental verification of a technique for locating a fatigue crack on beams vibrating under Gaussian excitation
2007
The stationary vibrations of a beam excited by Gaussian noise are strongly affected by the presence of a fatigue crack. Indeed, as soon as the crack arises the system response becomes non-linear due to crack breathing and a non-Gaussian behaviour is encountered. The paper presents both numerical and experimental investigations in order to assess the capability of the non-Gaussianity measures to detect crack presence and position. Monte Carlo method is applied to evaluate in time domain the higher order statistics of a cantilever beam modelled by finite elements. The skewness coefficient of the rotational degrees of freedom appears the most suitable quantity for identification purpose being …
A novel thermoeconomic analysis under dynamic operating conditions for space heating and cooling systems
2019
Abstract Thermoeconomic analysis allows for a deep understanding of the cost formation process within an energy system, providing insights into the possible routes for improvement. Several thermoeconomic approaches are well-established for application in systems with steady operating conditions, such as power plants, while a limited number of applications to air-conditioning systems in buildings have been proposed, due to the difficulties in dealing with very irregular load profiles and unsteady plant operating conditions. This study investigates the potential of Thermoeconomics as a support for decision making in building energy systems, proving its capability to identify trade-offs betwee…
Measuring the CO2 shadow price for wastewater treatment: A directional distance function approach
2015
Abstract The estimation of the value of carbon emissions has become a major research and policy topic since the establishment of the Kyoto Protocol. The shadow price of CO2 provides information about the marginal abatement cost of this pollutant. It is an essential element in guiding environmental policy issues, since the CO2 shadow price can be used when fixing carbon tax rates, in environmental cost-benefit analysis and in ascertaining an initial market price for a trading system. The water industry could play an important role in the reduction of greenhouse gas (GHG) emissions. This paper estimates the shadow price of CO2 for a sample of wastewater treatment plants (WWTPs), using a param…
Properties of amphiphilic terminally substituted conjugated nonaene- and 2-docosylnonaene carboxylic acids in monolayers at the air-water interface
1991
was a lo-' M Co(NO,), + lo-' M CH,COONa solution, with pH 7.5; the counter electrode was a Pt sheet, conveniently located in the electrochemical cell. After deposition, the electrochemical/electrochromic properties of the films were analyzed in degassed lo-' M KOH electrolyte, in a three electrode cell (Pt wire counter electrode, saturated calomel reference electrode) with optical windows. A PAR 173 potentiostat-galvanostat associated with a PAR 175 function generator was used in the electrochemical experiments. Data were recorded in a analogical X-Y (X-T) recorder. Monochromatic transmission (He-Ne laser, A = 632.8 nm) was recorded in situ, by means of a versatile optical bench; spectral t…
Evaluation of ventricular wall stress and cardiac function in patients with dilated cardiomyopathy
2015
Dilated cardiomyopathy is a heart disease characterized by both left ventricular dilatation and left ventricular systolic dysfunction, leading to cardiac remodeling and ultimately heart failure. We aimed to investigate the effect of dilated cardiomyopathy on the pump performance and myocardial wall mechanics using patient-specific finite element analysis. Results evinced pronounced end-systolic wall stress on left ventricular wall of patients with dilated cardiomyopathy as compared to that of normal hearts. In dilated cardiomyopathy, both end-diastolic and end-systolic pressure–volume relationships of left ventricle and right ventricle were shifted to the right compared to controls, sugges…
Modeling in cardiovascular biomechanics
2010
In this review, we briefly summarize some of Professor K.R. Rajagopal's contributions to the field of cardiovascular mechanics and highlight some applications that have employed his theories and have expanded the ability to model the complex behaviors that characterize biological tissues. His contributions, spawning directly from the classical nonlinear theories of mechanics, have had general impact in diverse fields of engineering. Within biomechanics per se, Rajagopal's efforts have provided state-of-the-art modeling tools not only to characterize tissues, such as blood vessels, cerebral aneurysms, or blood, but also to characterize their evolution, i.e. vessel growth and remodeling or bl…
On the spectral moments of non-WSSUS mobile-to mobile double-Rayleigh fading channels
2017
This paper deals with the mathematical analysis of the spectral moments of non-wide-sensestationary uncorrelated-scattering (non-WSSUS) mobile-to-mobile (M2M) double-Rayleigh fading channels. The point of departure is a recently proposed geometry-based statistical model (GBSM) for M2M double-Rayleigh fading channels from which general analytical expressions are derived for the average Doppler shift, Doppler spread, average delay, and delay spread. Closed-form solutions of such expressions are presented for the particular case of the geometrical two-rings scattering model. The obtained results indicate that the average Doppler shift and Doppler spread are directly influenced by not only the …
PLLA scaffolds produced by thermally induced phase separation (TIPS) allow human chondrocyte growth and extracellular matrix formation dependent on p…
2016
Damage of hyaline cartilage species such as nasoseptal or joint cartilage requires proper reconstruction, which remains challenging due to the low intrinsic repair capacity of this tissue. Implantation of autologous chondrocytes in combination with a biomimetic biomaterial represents a promising strategy to support cartilage repair. The aim of this work was to assess the viability, attachment, morphology, extracellular matrix (ECM) production of human articular and nasoseptal chondrocytes cultured in vitro in porous poly(L-lactic) (PLLA) scaffolds of two selected pore sizes (100 and 200 μm). The PLLA scaffolds with 100 and 200 μm pore sizes were prepared via ternary thermally induced ph…