1,013 research outputs found
Use of pressure spectral maps for analysis of influence of the plenum volume on the surge in centrifugal blower
No full textThe influence of plenum volume on surge phenomenon in a centrifugal blower was studied by means of quasidynamic analysis. In this procedure, signals were gathered at 5 pressure tappings at 146 different positions of the throttling valve controlling the mass flow rate. Frequency spectra obtained by means of Fourier analysis are combined together in the form of colour maps with frequency as the abscissa and valve position as the ordinate. Such a map provides high-resolution information about spectral structures of pressure signals attained at different mass flow rates. Analysis was conducted at two system configurations characterized by different volumes between the blower and the valve i.e. plenum volume. Research confirmed that in both cases the first disturbances appear in the vicinity of the impeller leading edge in the same position of a throttling valve before the surge. Arising flow structure is characterized by strong and random pressure jumps and does not have any dominating frequency. At further valve closure pressure disturbances propagate towards the volute and at deep surge the strongest peaks are observed at the outlet. The moment of deep surge onset is also independent of the plenum volume, however, a difference is observed in the frequency and amplitude of the main modes. With the higher outlet volume the observed oscillations fit well to the frequency of a Helmholtz resonator while, in the case of the smaller volume, the frequency is higher than the frequency of a corresponding Helmholtz resonator
Maximal functions for groups of operators.
No full textLet Δ be the Laplace operator on d and 1 < δ < 2. Using transference methods we show that, for max {q, q/(q – 1)} < 4d/(2d + 1 – δ), the maximal function for the Schrödinger group is in Lq, for f Lq with Δδ/2 f Lq. We obtain a similar result for the Airy group exp it Δ3/2. An abstract version of these results is obtained for bounded C0-groups eitL on subspaces of Lp spaces. Certain results extend to maximal functions defined for functions with values in U M D Banach spaces
A maximal theorem for holomorphic semigroups on vector-valued spaces.
No full textSuppose that 1<p\leq \infty (\Omega ,\mu) is a \sigma finite measure space and E is a closed subspace of Labesgue Bochner space L^p(\Omega; E) consisting of function oon \Omega that take their values in some complex Banach space X. Suppose that -A is invertible and generates a bounded hlomorphic semigroup T_z on E. If 0<\alpha <1, and f belongs to the domain of A^\alpha, then the maximal function \sup_z|T_zf|, where the supremum is taken over any sector contained in the sector of holomorphy, belongs to L^p. This extends an earlier result of Blower and Doust
Suction Fan or Blower.
No full textPatent for a suction fan or blower to partially clean material that passes through, including illustration
Maximal functions and subordination for operator groups.
No full textLet E be a UMD Banach space and L a positive and self-adjoint operator in L^2 of Laplace type such that the imaginary powers L^{-it} form a C_0 group of exponential growth on L^p(E). Suppose that G is holomorphis inside and on the boundary os a suitable sector. Then G(tL) defines a bounded family of linear operators on L^p(E); the maximal operator f->sup | G(tL)f| os bounded on the domain of log L. These hypotheses hold for the maximal solution operators for the heat, wave and Schroedinger operators, and for Cesaro sums
Blower and Suction Device.
No full textPatent for a blower for a threshing machine that regulates the amount of air put out of the machine, and is both affordable and durable
Regenerative Blower for EVA Suit Ventilation Fan
No full textPortable life support systems in future space suits will include a ventilation subsystem driven by a dedicated fan. This ventilation fan must meet challenging requirements for pressure rise, flow rate, efficiency, size, safety, and reliability. This paper describes research and development that showed the feasibility of a regenerative blower that is uniquely suited to meet these requirements. We proved feasibility through component tests, blower tests, and design analysis. Based on the requirements for the Constellation Space Suit Element (CSSE) Portable Life Support System (PLSS) ventilation fan, we designed the critical elements of the blower. We measured the effects of key design parameters on blower performance using separate effects tests, and used the results of these tests to design a regenerative blower that will meet the ventilation fan requirements. We assembled a proof-of-concept blower and measured its performance at sub-atmospheric pressures that simulate a PLSS ventilation loop environment. Head/flow performance and maximum efficiency point data were used to specify the design and operating conditions for the ventilation fan. We identified materials for the blower that will enhance safety for operation in a lunar environment, and produced a solid model that illustrates the final design. The proof-of-concept blower produced the flow rate and pressure rise needed for the CSSE ventilation subsystem while running at 5400 rpm, consuming only 9 W of electric power using a non-optimized, commercial motor and controller and inefficient bearings. Scaling the test results to a complete design shows that a lightweight, compact, reliable, and low power regenerative blower can meet the performance requirements for future space suit life support systems
Integrable operators and squares of Hankel operators.
No full textIntegrable operators arise in random matrix teory, where they describe the asymptotic distributions of large self-adjoint random matrices from the generalized unitary ensembles. This paper gives sufficient conditions for an integrable operator to be the square of a hankel operator, and applies the condition to the Airy. associated Laguerre, modified Bessel and Whittaker functions
Discrete Tracy--Widom operators.
No full textIntegrable operators arise in random matrix theory, where they describe the asymptotic eigenvalue distribution of large self-adjoint random matrices from the generalized unitary ensembles. This paper considers discrete Tracy--Widom operators, and gives sufficient conditions for a discrete integrable operator to be the square of a Hankel matrix. Examples include the discrete Bessel kernel and kernels arising from the almost Mathieu equatio and the Fourier transform of Mathieu's equation
Hankel operators that commute with second order differential operators.
No full textSuppose that is a continuous and self-adjoint Hankel operator on with kernel and that a(0)=0ab\phi\Gamma L=L\Gamma$. There are also results proving rapid decay of the singular numbers of Hankel integral operators with kernels that are analytic and of exponential decay in the right half-plane
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