1,723,128 research outputs found
A three accelerometer method for the measurement of flow rate in pipe
No full textA method for the measurement of flow rate in a pipe is proposed. The method utilizes the vibration signals that are generated using an external exciter. Three accelerometers on the surface of a pipe are used to measure these signals. Applying wave decomposition theory to the measured vibration signal, change of wave number, which is one of the results caused by flow rate change, is estimated. The change of wave number is converted into flow rate using the simple mathematical model bf fluid conveying pipe. The main advantage of this method is that it does not require any sensory system inside the pipe, so that the characteristics of flow are not disturbed and the measurement position can be easily moved. All possible error's associated with the proposed measurement system are investigated. Those are due to sensor spacing, relative position of sensor with respect to boundaries, phase mismatch as well as magnitude mismatch between sensors, and measurement noise. To verify the potential of this method, experiments using water conveying steel pipe are accomplished. Finally, the estimated flow rates are within 12% error bounds. (C) 1996 Acoustical Society of America
TRANSPORT OF A CONDENSABLE SPECIES IN NONISOTHERMAL TUBE FLOW
No full textWe present the equations for condensation in cooled upward laminar flow in tubes and consider their solution for low vapour concentrations and variable vapour-gas thermodynamic properties. We treated the full problem, including coupling with the aerosol size distribution, by using the PSI-CELL (Particle Source in Cell) method. The particle trajectories start from the point where the particles are generated by homogeneous nucleation. Particle size distribution and vapour scavenging by particles are obtained in forced convection and mixed convection regions. Calculations were also conducted with respect to tube diameters
Holographic reconstruction of active sources and surface admittance in an enclosure
No full textNear-field acoustic holography (NAH) is applied to reconstruct an exterior sound field, as well as an interior sound field. A numerical method is employed to reconstruct the interior sound field of an arbitrary shaped enclosure. Reconstructed sound fields are usually used in identifying noise sources. However, until now, it has not been thoroughly verified whether the reconstructed sound field of an interior also shows source distributions. Interior sound fields have been reconstructed without any thought given to this question. In contrast to an exterior sound field, reflections are added to an interior sound field and therefore, the reconstructed sound field may misrepresent the source distribution. This paper addresses a way to solve this problem. A measurement method is proposed in order to distinguish between reflections and direct radiation from noise sources. (C) 1999 Acoustical Society of American. [S0001-4966(99)05703-3]
Modified embedded-atom method interatomic potentials for the Ni-Co binary and the Ni-Al-Co ternary systems
No full textInteratomic potentials for the Ni-Co binary and Ni-Al-Co ternary systems have been developed on the basis of the second nearest-neighbor modified embedded-atom method (2NN MEAM) formalism. The potentials describe structural, thermodynamic, deformation and defect properties of solid solution phases or compound phases in reasonable agreements with experiments or first-principles calculations. The results demonstrate the transferability of the potentials and their applicability to large-scale atomistic simulations to investigate the effect of an alloying element, cobalt, on various microstructural factors related to mechanical properties of Ni-based superalloys on an atomic scale.11sciescopu
Immunopathogenesis of Allergic Asthma: More Than the Th2 Hypothesis
No full textAsthma is a chronic obstructive airway disease that involves inflammation of the respiratory tract. Biological contaminants in indoor air can induce innate and adaptive immune responses and inflammation, resulting in asthma pathology. Epidemiologic surveys indicate that the prevalence of asthma is higher in developed countries than in developing countries. The prevalence of asthma in Korea has increased during the last several decades. This increase may be related to changes in housing styles, which result in increased levels of indoor biological contaminants, such as house dust mite-derived allergens and bacterial products such as endotoxin. Different types of inflammation are observed in those suffering from mild-to-moderate asthma compared to those experiencing severe asthma, involving markedly different patterns of inflammatory cells and mediators. As described in this review, these inflammatory profiles are largely determined by the involvement of different T helper cell subsets, which orchestrate the recruitment and activation of inflammatory cells. It is becoming clear that T helper cells other than Th2 cells are involved in the pathogenesis of asthma; specifically, both Th1 and Th17 cells are crucial for the development of neutrophilic inflammation in the airways, which is related to corticosteroid resistance. Development of therapeutics that suppress these immune and inflammatory cells may provide useful asthma treatments in the future.112723sciescopuskciothe
Growth and electronic properties of Ag overlayers on stepped Pt(211) surface
No full textThe growth and electronic properties of ultrathin silver films deposited onto Pt(211) surface were studied using Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and x-ray photoelectron spectroscopy. The AES and LEED results indicate that the silver grows by a layer by layer growth followed by three dimensional islands growth. The XPS results show that the AR 3d core-level binding energy of Ag overlayers on Pt(211) shifts toward lower binding energy relative to the bulk value at lower Ag coverage. This negative binding energy shift of the Ag 3d core level is explained by the reduced coordination number oi the overlayer atoms and the resulting initial state band narrowing effect suggested by Wertheim and Citrin [Phys. Rev. Lett. 1978, 41, 1425]
Segregation induced reconstructions of Li-Al(110) alloy surface
No full textThe surface segregation of Li in Al(110)-12.7at%Li alloy and simultaneous reconstructions are investigated using Auger electron spectroscopy and low energy electron diffraction. The measured diffusion coefficient and barrier energy of Li segregation to the alloy surface was close to that of a bulk one. The saturation coverage of Li was close to 1 monolayer, that is, the ratio of the atomic number of Li to Al is 1:1 after heat treatment. Based on the measurement of the surface Li coverages for the c(2 x 2) and (2 x 1) surface reconstructions, we suggest possible model structures. (C) 1997 Elsevier Science B.V.Financial supports have been partially provided by the center for molecular science and KOSEF. We thank professor J.K. Park for providing the sampl
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