43,561 research outputs found
Heat transfer characteristics within an array of impinging jets. Effects of crossflow temperature relative to jet temperature
Spanwise average heat fluxes, resolved in the streamwise direction to one stream-wise hole spacing were measured for two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate. The jet flow, after impingement, was constrained to exit in a single direction along the channel formed by the jet orifice plate and heat transfer surface. The crossflow originated from the jets following impingement and an initial crossflow was present that approached the array through an upstream extension of the channel. The regional average heat fluxes are considered as a function of parameters associated with corresponding individual spanwise rows within the array. A linear superposition model was employed to formulate appropriate governing parameters for the individual row domain. The effects of flow history upstream of an individual row domain are also considered. The results are formulated in terms of individual spanwise row parameters. A corresponding set of streamwise resolved heat transfer characteristics formulated in terms of flow and geometric parameters characterizing the overall arrays is described
Renormalization of the Sigma-Omega model within the framework of U(1) gauge symmetry
It is shown that the Sigma-Omega model which is widely used in the study of
nuclear relativistic many-body problem can exactly be treated as an Abelian
massive gauge field theory. The quantization of this theory can perfectly be
performed by means of the general methods described in the quantum gauge field
theory. Especially, the local U(1) gauge symmetry of the theory leads to a
series of Ward-Takahashi identities satisfied by Green's functions and proper
vertices. These identities form an uniquely correct basis for the
renormalization of the theory. The renormalization is carried out in the
mass-dependent momentum space subtraction scheme and by the renormalization
group approach. With the aid of the renormalization boundary conditions, the
solutions to the renormalization group equations are given in definite
expressions without any ambiguity and renormalized S-matrix elememts are
exactly formulated in forms as given in a series of tree diagrams provided that
the physical parameters are replaced by the running ones. As an illustration of
the renormalization procedure, the one-loop renormalization is concretely
carried out and the results are given in rigorous forms which are suitable in
the whole energy region. The effect of the one-loop renormalization is examined
by the two-nucleon elastic scattering.Comment: 32 pages, 17 figure
On indecomposable modules over the Virasoro algebra
It is proved that an indecomposable Harish-Chandra module over the Virasoro
algebra must be (i) a uniformly bounded module, or (ii) a module in Category
, or (iii) a module in Category , or (iv) a module which
contains the trivial module as one of its composition factors.Comment: 5 pages, Latex, to appear in Science in China
Fermi gas in harmonic oscillator potentials
Assuming the validity of grand canonical statistics, we study the properties
of a spin-polarized Fermi gas in harmonic traps. Universal forms of Fermi
temperature , internal energy and the specific heat per particle of
the trapped Fermi gas are calculated as a {\it function} of particle number,
and the results compared with those of infinite number particles.Comment: 8 pages, 1 figure, LATE
Effect of substrate misorientation on ordering in Ga0.5In0.5P
Journal ArticleOrdering produced in Gao.5Ino.5P epitaxial layers grown by OMVPE can be controlled by variations in the substrate misorientation as well as the growth temperature and the growth rate. The ordering produced at a growth temperature of 620°C and a relatively low growth rate of 0.5 /μm/hr is found to depend strongly on both the direction and angle of substrate misorientation
Jet array impingement flow distributions and heat transfer characteristics. Effects of initial crossflow and nonuniform array geometry
Two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate are considered. The jet flow, after impingement, is constrained to exit in a single direction along the channel formed by the jet orifice plate and the heat transfer surface. The configurations considered are intended to model those of interest in current and contemplated gas turbine airfoil midchord cooling applications. The effects of an initial crossflow which approaches the array through an upstream extension of the channel are considered. Flow distributions as well as heat transfer coefficients and adiabatic wall temperatures resolved to one streamwise hole spacing were measured as a function of the initial crossflow rate and temperature relative to the jet flow rate and temperature. Both Nusselt number profiles and dimensionless adiabatic wall temperature (effectiveness) profiles are presented and discussed. Special test results which show a significant reduction of jet orifice discharge coefficients owing to the effect of a confined crossflow are also presented, along with a flow distribution model which incorporates those effects. A nonuniform array flow distribution model is developed and validated
BRDFs acquired by directional radiative measurements during EAGLE and AGRISAR
Radiation is the driving force for all processes and interactions between earth surface and atmosphere. The amount of
measured radiation reflected by vegetation depends on its structure, the viewing angle and the solar angle. This angular
dependence is usually expressed in the Bi-directional Reflectance Distribution Function (BRDF). This BRDF is not
only different for different types of vegetation, but also different for different stages of the growth. The BRDF therefore
has to be measured at ground level before any satellite imagery can be used the calculate surface-atmosphere
interaction. The objective of this research is to acquire the BRDFs for agricultural crop types.
A goniometric system is used to acquire the BRDFs. This is a mechanical device capable of a complete hemispherical
rotation. The radiative directional measurements are performed with different sensors that can be attached to this
system. The BRDFs are calculated from the measured radiation.
In the periods 10 June - 18 June 2006 and 2 July - 10 July 2006 directional radiative measurements were performed at
three sites: Speulderbos site, in the Netherlands, the Cabauw site, in the Netherlands, and an agricultural test site in
Goermin, Germany. The measurements were performed over eight different crops: forest, grass, pine tree, corn, wheat,
sugar beat and barley. The sensors covered the spectrum from the optical to the thermal domain. The measured radiance
is used to calculate the BRDFs or directional thermal signature.
This contribution describes the measurements and calculation of the BRDFs of forest, grassland, young corn, mature
corn, wheat, sugar beat and barley during the EAGLE2006 and AGRISAR 2006 fieldcampaigns. Optical BRDF have
been acquired for all crops except barley. Thermal angular signatures are acquired for all the crop
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Studies on Temperature and Strain Sensitivities of a Few-mode Critical Wavelength Fiber Optic Sensor
This paper studied the relationship between the temperature/strain wavelength sensitivity of a fiber optic in-line Mach-Zehnder Interferometer (MZI) sensor and the wavelength separation of the measured wavelength to the critical wavelength (CWL) in a CWL-existed interference spectrum formed by interference between LP01 and LP02 modes. The in-line MZI fiber optic sensor has been constructed by splicing a section of specially designed few-mode fiber (FMF), which support LP01 and LP02 modes propagating in the fiber, between two pieces of single mode fiber. The propagation constant difference, Δβ, between the LP01 and LP02 modes, changes non-monotonously with wavelength and reaches a maximum at the CWL. As a result, in sensor operation, peaks on the different sides of the CWL then shift in opposite directions, and the associated temperature/strain sensitivities increase significantly when the measured wavelength points become close to the CWL, from both sides of the CWL. A theoretical analysis carried out has predicted that with this specified FMF sensor approach, the temperature/strain wavelength sensitivities are governed by the wavelength difference between the measured wavelength and the CWL. This conclusion was seen to agree well with the experimental results obtained. Combining the wavelength shifts of the peaks and the CWL in the transmission spectrum of the SFS structure, this study has shown that this approach forms the basis of effective designs of high sensitivity sensors for multi-parameter detection and offering a large measurement range to satisfy the requirements needed for better industrial measurements
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