1,500 research outputs found

    Elliptic jets, part 2. Dynamics of coherent structures: Pairing

    Get PDF
    The dynamics of the jet column mode of vortex pairing in the near field of an elliptic jet was investigated. Hot-wire measurements and flow visualization were used to examine the details of the pairing mechanism of nonplanar vortical elliptic structures and its effect on such turbulence measures as coherent velocities, incoherent turbulence intensities, incoherent and coherent Reynolds, stresses, turbulence production, and mass entrainment. It was found that pairing of elliptic vortices in the jet column does not occur uniformly around the entire perimeter, unlike in a circular jet. Merger occurs only in the initial major-axis plane. In the initial minor-axis plane, the trailing vortex rushes through the leading vortex without pairing and then breaks down violently, producing considerably greater entrainment and mixing than in circular or plane jets

    Viscometric Studies of α-Amino Acid in Aqueous NaCl and MgCl2 at 303 K

    Get PDF

    Selecting the number and values of the CPWI steering angles and the effect of that on imaging quality

    Get PDF
    Compounded Plane-Wave Imaging (CPWI) has the ability to provide ultrafast imaging for many applications like colour flow imaging, microbubble imaging and elastography. The compounding operation improves the imaging quality at the expense of reducing the frame rate. Due to the importance of frame rate in ultrafast imaging, selecting the number and value of the compounded angles is a critical step to achieve the best possible imaging quality using the minimum number of angles whilst preserving the frame rate. This paper produces a new method for selecting the angular range and the number of angles in CPWI depending on the characteristics of the transducer and medium using Field II program. Experiments were performed on a wire phantom to show the efficiency of the produced method. The results show a comparative imaging quality of CPWI at the selected parameters when compared with linear imaging

    Two-way Quality Assessment Approach for Tumour Detection using Free-hand Strain Imaging

    Get PDF
    A novel two-way image quality assessment method is proposed for free-hand strain imaging. In elasticity imaging, tissue with different stiffness exhibit varying contrast in the strain images and detectability of a lesion is measured using elastographic contrast-to-noise ratio (CNRe). Representing quality of strain images quantitatively is vital for improving imaging techniques and also for clinical diagnosis. It avoids the subjective approach of interpreting strain images. Conventionally, contrast between stiff lesion and surrounding soft tissue is measured using contrast-to-noise ratio and strain image with the highest CNRe amplitude is considered an optimal strain image. However experimental results have suggested that merely CNRe metric is often misleading and does not always represent the true elastic modulus contrast as the correlation coefficient falls below an acceptable levels and accuracy is compromised. Therefore in this study, the objective is to propose a comprehensive strain image quality assessment method which is reliable for clinical examinations and research

    Vocal cord paralysis following endotracheal intubation

    Get PDF

    Parental [correction of Perinatal] consanguinity: a risk factor for developmental delay in Pakistani children

    Get PDF
    Objective: To investigate the association of parental consanguinity and delayed development in terms of gross motor, fine motor, speech and social aspects in their children.Methods: One hundred and seventy seven children (age 15 days--72 months) were evaluated for their developmental status utilizing the Denver Developmental Screening Test (DDST). An unmatched case-control study design was used. Case group consisted of 94 children and control group 83 children. Odds ratios were calculated for parental consanguinity and delay in gross and fine motor, speech and social development in their children, for cases and controls, utilizing Binary Multiple Logistic Regression Analysis. Acquired delay was excluded through detailed birth history in both cases and control group respectively.Results: Univariate analysis showed high significant Odds ratios for all areas of developmental delay (viz. gross and fine motor, speech and social development), between cases and controls (p \u3c .001). At the multivariate analysis level however, our results showed no increased risk of parental consanguinity on delayed gross and fine motor, speech and social development in their children.Conclusion: Our results show no increased risk of parental consanguinity on delayed gross and fine motor, speech or social development (as measured by the DDST), in their children
    corecore