yaser ali - Academia.edu (original) (raw)
Papers by yaser ali
Pakistan Journal of Biological Sciences, 2010
This study aimed to measure serum levels of the proinflammatory protein S100A12, investigate clin... more This study aimed to measure serum levels of the proinflammatory protein S100A12, investigate clinical as well as contrast enhanced magnetic resonance imaging findings of temporomandibular joint inflammation among juvenile idiopathic arthritis patients and to find out the correlation between each of them, moreover with different disease parameters as temporomandibular joint inflammation may occur without clinical manifestations; it is in need for thorough evaluation and S100A12 may be a future anti-inflammatory treatment in JIA. Twenty patients with Juvenile Idiopathic Arthritis (JIA) and 10 healthy control subjects underwent measurement of S100A12 serum concentrations by sandwich ELISA. Temporomandibular Joints (TMJs); clinical and post contrast Magnetic Resonance Imaging (MRI) examinations were performed. MRI findings were scored. Results showed that TMJ arthritis was detected in 80% of JIA patients using MRI. Serum S100A12 levels were significantly increased in patients compared to controls. Serum concentrations of S100A12 and total MRI scores were significantly higher in JIA patients with active disease compared to those without activity. Systemic and polyarticular JIA patients showed significant increase in S100A12 levels and total MRI scores compared to those with oligoarticular JIA. The MRI TMJ abnormalities revealed significant association with clinical signs of TMJ inflammation but not with symptoms. A significant correlation was found between serum S100A12 concentrations and MRI score as well as between each of them and different clinical, laboratory disease parameters. Serum S100A12 levels showed significant positive correlation with synovial enhancement score. To conclude TMJ arthritis could be detected in most cases of JIA patients using contrast enhanced MRI. Increased S100A12 levels may point to synovial inflammation. Clinical signs of TMJ arthritis may be used as filter for MRI examination. Further studies on larger scale of JIA patients are needed for monitoring TMJ inflammation and S100A12 may be a potential target of future anti-inflammatory therapy.
Aiaa Journal, 2010
We present a computational aeroacoustics method to evaluate sound generated by low Mach number fl... more We present a computational aeroacoustics method to evaluate sound generated by low Mach number flows in complex configurations in which turbulence interacts with arbitrarily shaped solid objects. This hybrid approach is based on Lighthill's acoustic analogy in conjunction with sound source information from an incompressible calculation. In this method, Lighthill's equation is solved using a boundary element method that allows the effect of scattered sound from arbitrarily shaped solid objects to be incorporated. We present validation studies for sound generated by laminar and turbulent flows over a circular cylinder at Re 100 and 10,000, respectively. Our hybrid approach is validated against directly computed sound using a high-order compressible flow solver as well as the solution of the Ffowcs Williams and Hawkings equation in conjunction with compressible sound sources. We demonstrate that the sound predicted by a second-order hybrid approach is as accurate as sound directly computed by a sixth-order compressible flow solver in the frequency range in which low-order numerics can accurately resolve the flow structures. As an example of an engineering problem, we calculated the sound generated by flow over an automobile side-view mirror and compared it to experimental measurements. Nomenclature C D , C L = drag and lift coefficients, respectively c = speed of sound d = dimension of the problem e ij = viscous stress tensor f = frequency G = Green's function of the Helmholtz operator k = wave number L, L c = width of the mirror, recirculation length M, M i = freestream Mach number, freestream vector Mach number n i = unit outward to the boundary @ p, p a = pressure, acoustic pressure defined as c 2 0 0 Re = Reynolds number r = distance from the sound source region St = Strouhal number T ij = Lighthill's stress tensor t = time u, v = compressible and incompressible velocities, respectively u = streamwise velocity x, y = locations of the observer and the source, respectively x i = Cartesian coordinate = domain-dependent geometrical factor ij = Kronecker delta = fluid density = power spectral density , @ = acoustic medium, boundary of the acoustic medium, that is, solid boundary nfxg = domain excluding the point x ! = angular frequency k = modulus of a complex quantity x = quantity evaluated at observer location x Subscript 0 = reference quantity Superscripts 0 = difference from the reference quantity = quantity in the frequency domain = time mean of the quantity rms = rms. of the quantity
In many practical applications, sound is generated by interaction of turbulent flow with solid ob... more In many practical applications, sound is generated by interaction of turbulent flow with solid objects. In such cases, sound waves experience multiple reflections from solid objects before they propagate to a far-field point. In these situations the sound spectrum exhibits a rich frequency content consisting of broadband and tonal components. To predict the acoustic field in these situations, a general aero-acoustics framework is required to operate in complex environments. More importantly, the employed method must avoid many simplifying assumptions often made about the geometry, compactness or frequency content of sound sources. The objective of the present work is to develop, validate and demonstrate the functionality of such a computational framework.
We present a computational aero-acoustics method to evaluate noise generated by low Mach number f... more We present a computational aero-acoustics method to evaluate noise generated by low Mach number flow over complex configurations. This method is a hybrid approach which uses Lighthill's acoustic analogy in conjunction with source-data from an incompressible calculation. Scattering of sound waves are computed using a Boundary Element Method. This approach can be applied to flow configurations with practical complexities where turbulence interacts with arbitrary shaped solid objects. We present a validation study for sound generated by flow over a circular cylinder at Re=100 and Re=10000. The hybrid method is validated against directly computed noise using a high order compressible flow solver as well as solution of the Ffowcs Williams-Hawkings equation in conjunction with compressible noise sources. We concluded that the noise predicted by a 2^nd order hybrid approach is as accurate as directly computed noise by a 6^th order compressible flow solver in the low frequency range where the low order numerics can accurately resolve the flow structures.
Pakistan Journal of Biological Sciences, 2010
This study aimed to measure serum levels of the proinflammatory protein S100A12, investigate clin... more This study aimed to measure serum levels of the proinflammatory protein S100A12, investigate clinical as well as contrast enhanced magnetic resonance imaging findings of temporomandibular joint inflammation among juvenile idiopathic arthritis patients and to find out the correlation between each of them, moreover with different disease parameters as temporomandibular joint inflammation may occur without clinical manifestations; it is in need for thorough evaluation and S100A12 may be a future anti-inflammatory treatment in JIA. Twenty patients with Juvenile Idiopathic Arthritis (JIA) and 10 healthy control subjects underwent measurement of S100A12 serum concentrations by sandwich ELISA. Temporomandibular Joints (TMJs); clinical and post contrast Magnetic Resonance Imaging (MRI) examinations were performed. MRI findings were scored. Results showed that TMJ arthritis was detected in 80% of JIA patients using MRI. Serum S100A12 levels were significantly increased in patients compared to controls. Serum concentrations of S100A12 and total MRI scores were significantly higher in JIA patients with active disease compared to those without activity. Systemic and polyarticular JIA patients showed significant increase in S100A12 levels and total MRI scores compared to those with oligoarticular JIA. The MRI TMJ abnormalities revealed significant association with clinical signs of TMJ inflammation but not with symptoms. A significant correlation was found between serum S100A12 concentrations and MRI score as well as between each of them and different clinical, laboratory disease parameters. Serum S100A12 levels showed significant positive correlation with synovial enhancement score. To conclude TMJ arthritis could be detected in most cases of JIA patients using contrast enhanced MRI. Increased S100A12 levels may point to synovial inflammation. Clinical signs of TMJ arthritis may be used as filter for MRI examination. Further studies on larger scale of JIA patients are needed for monitoring TMJ inflammation and S100A12 may be a potential target of future anti-inflammatory therapy.
Aiaa Journal, 2010
We present a computational aeroacoustics method to evaluate sound generated by low Mach number fl... more We present a computational aeroacoustics method to evaluate sound generated by low Mach number flows in complex configurations in which turbulence interacts with arbitrarily shaped solid objects. This hybrid approach is based on Lighthill's acoustic analogy in conjunction with sound source information from an incompressible calculation. In this method, Lighthill's equation is solved using a boundary element method that allows the effect of scattered sound from arbitrarily shaped solid objects to be incorporated. We present validation studies for sound generated by laminar and turbulent flows over a circular cylinder at Re 100 and 10,000, respectively. Our hybrid approach is validated against directly computed sound using a high-order compressible flow solver as well as the solution of the Ffowcs Williams and Hawkings equation in conjunction with compressible sound sources. We demonstrate that the sound predicted by a second-order hybrid approach is as accurate as sound directly computed by a sixth-order compressible flow solver in the frequency range in which low-order numerics can accurately resolve the flow structures. As an example of an engineering problem, we calculated the sound generated by flow over an automobile side-view mirror and compared it to experimental measurements. Nomenclature C D , C L = drag and lift coefficients, respectively c = speed of sound d = dimension of the problem e ij = viscous stress tensor f = frequency G = Green's function of the Helmholtz operator k = wave number L, L c = width of the mirror, recirculation length M, M i = freestream Mach number, freestream vector Mach number n i = unit outward to the boundary @ p, p a = pressure, acoustic pressure defined as c 2 0 0 Re = Reynolds number r = distance from the sound source region St = Strouhal number T ij = Lighthill's stress tensor t = time u, v = compressible and incompressible velocities, respectively u = streamwise velocity x, y = locations of the observer and the source, respectively x i = Cartesian coordinate = domain-dependent geometrical factor ij = Kronecker delta = fluid density = power spectral density , @ = acoustic medium, boundary of the acoustic medium, that is, solid boundary nfxg = domain excluding the point x ! = angular frequency k = modulus of a complex quantity x = quantity evaluated at observer location x Subscript 0 = reference quantity Superscripts 0 = difference from the reference quantity = quantity in the frequency domain = time mean of the quantity rms = rms. of the quantity
In many practical applications, sound is generated by interaction of turbulent flow with solid ob... more In many practical applications, sound is generated by interaction of turbulent flow with solid objects. In such cases, sound waves experience multiple reflections from solid objects before they propagate to a far-field point. In these situations the sound spectrum exhibits a rich frequency content consisting of broadband and tonal components. To predict the acoustic field in these situations, a general aero-acoustics framework is required to operate in complex environments. More importantly, the employed method must avoid many simplifying assumptions often made about the geometry, compactness or frequency content of sound sources. The objective of the present work is to develop, validate and demonstrate the functionality of such a computational framework.
We present a computational aero-acoustics method to evaluate noise generated by low Mach number f... more We present a computational aero-acoustics method to evaluate noise generated by low Mach number flow over complex configurations. This method is a hybrid approach which uses Lighthill's acoustic analogy in conjunction with source-data from an incompressible calculation. Scattering of sound waves are computed using a Boundary Element Method. This approach can be applied to flow configurations with practical complexities where turbulence interacts with arbitrary shaped solid objects. We present a validation study for sound generated by flow over a circular cylinder at Re=100 and Re=10000. The hybrid method is validated against directly computed noise using a high order compressible flow solver as well as solution of the Ffowcs Williams-Hawkings equation in conjunction with compressible noise sources. We concluded that the noise predicted by a 2^nd order hybrid approach is as accurate as directly computed noise by a 6^th order compressible flow solver in the low frequency range where the low order numerics can accurately resolve the flow structures.