3,529 research outputs found
Performance of a low-pressure-ratio centrifugal compressor with four diffuser designs
A low-pressure-ratio centrifugal compressor was tested with four different diffuser configurations. One diffuser had airfoil vanes. Two were pipe diffusers. One pipe diffuser had 7.5 deg cone diffusing passages. The other had trumpet-shaped passages designed for linear static-pressure rise from throat to exit. The fourth configuration had flat vanes with elliptical leading edges similar to those of pipe diffusers. The side walls were contoured to produce a linear pressure rise. Peak compressor efficiencies were 0.82 with the airfoil vane and conical pipe diffusers, 0.80 with the trumpet, and 0.74 with the flat-vane design. Surge margin and useful range were greater for the airfoil-vane diffuser than for the other three
Effect of inducer inlet and diffuser throat areas on performance of a low pressure ratio sweptback centrifugal compressor
A low-pressure-ratio centrifugal compressor was tested with nine combinations of three diffuser throat areas and three impeller inducer inlet areas which were 75, 100, and 125 percent of design values. For a given inducer inlet area, increases in diffuser area within the range investigated resulted in increased mass flow and higher peak efficiency. Changes in both diffuser and inducer areas indicated that efficiencies within one point of the maximum efficiency were obtained over a compressor specific speed range of 27 percent. The performance was analyzed of an assumed two-spool open-cycle engine using the 75 percent area inducer with a variable area diffuser
Electronic visualization of gas bearing behavior
Visualization technique produces a visual simulation of gas bearing operation by electronically combining the outputs from the clearance probes used to monitor bearing component motion. Computerized recordings of the probes output are processed, displayed on an oscilloscope screen and recorded with a high-speed motion picture camera
Experimental performance of a 16.10-centimeter-tip-diameter sweptback centrifugal compressor designed for a 6:1 pressure ratio
A backswept impeller with design mass flow rate of 1.033 kg/sec was tested with both a vaned diffuser and a vaneless diffuser to establish stage and impeller characteristics. Design stage pressure ratio of 5.9:1 was attained at a flow slightly lower than the design value. Flow range at design speed was 6 percent of choking flow. Impeller axial tip clearance at design speed was varied to determine effect on stage and impeller performance
Experimental performance of a 13.65-centimeter-tip-diameter tandem-bladed sweptback centrifugal compressor designed for a pressure ratio of 6
A 13.65 cm tip diameter backswept centrifugal impeller having a tandem inducer and a design mass flow rate of 0.907 kg/sec was experimentally investigated to establish stage and impeller characteristics. Tests were conducted with both a cascade diffuser and a vaneless diffuser. A pressure ratio of 5.9 was obtained near surge for the smallest clearance tested. Flow range at design speed was 6.3 percent for the smallest clearance test. Impeller exit to shroud axial clearance at design speed was varied to determine the effect on stage and impeller performance
Capturing teacher priorities: Using real-world eye-tracking to investigate expert teacher priorities across two cultures
Classroom teaching is complex. In the classroom, teachers must readily attend to disruptions and successfully convey new tasks and information. Outside the classroom, teachers must organise their priorities that are important for successful student learning. In fact, differing gaze patterns can reveal the varying priorities that teachers have. Teacher priorities are likely to vary with classroom expertise and can conceivably change with culture too. Therefore, the present study investigated expertise related and cultural teacher priorities by analysing their gaze proportions. To obtain this data, 40 secondary school teachers wore eye-tracking glasses during class time, with 20 teachers (10 expert; 10 novice) from the UK and 20 teachers (10 expert; 10 novice) from Hong Kong. We analysed gaze proportions during teachers' attentional (i.e., information-seeking, e.g., teacher questioning students) and communicative (i.e., information-giving, e.g., teacher lecturing students) gaze. Regardless of culture, expert teachers' gaze proportions revealed prioritisation of students, whereas novice teachers gave priority to non-instructional (i.e., not students, teacher materials, or student materials) classroom regions. Hong Kong teachers prioritised teacher materials (e.g., whiteboard) during communicative gaze whereas UK teachers prioritised non-instructional regions. Regarding culture-specific expertise, with Hong Kong experts prioritised teacher materials more than UK experts who, in turn, did so more than UK novices. We thus demonstrate the role of implicit teacher gaze measures as micro-level indicators of macro-level and explicit aspects of instruction, namely teacher priority
Heavy quark action on the anisotropic lattice
We investigate the improved quark action on anisotropic lattice as a
potential framework for the heavy quark, which may enable precision computation
of hadronic matrix elements of heavy-light mesons. The relativity relations of
heavy-light mesons as well as of heavy quarkonium are examined on a quenched
lattice with spatial lattice cutoff 1.6 GeV and the
anisotropy . We find that the bare anisotropy parameter tuned for the
massless quark describes both the heavy-heavy and heavy-light mesons within 2%
accuracy for the quark mass , which covers the charm quark
mass. This bare anisotropy parameter also successfully describes the
heavy-light mesons in the quark mass region within the
same accuracy. Beyond this region, the discretization effects seem to grow
gradually. The anisotropic lattice is expected to extend by a factor the
quark mass region in which the parameters in the action tuned for the massless
limit are applicable for heavy-light systems with well controlled systematic
errors.Comment: 11 pages, REVTeX4, 11 eps figure
Charmed hadron physics in quenched anisotropic lattice QCD
We investigate the anisotropic lattice with improved quark action as a
candidate of framework in which we can treat both the heavy and light quark
region in the same manner and systematically reduce the systematic
uncertainties. To examine applicability of anisotropic lattice, we calculate
the charmed meson spectrum and decay constants in quenched approximation. We
find consistent result with most advanced results on isotropic lattices.Comment: 3 pages, 1 figure, contribution to Fifth KEK Topical Conference -
Frontiers in Flavor Physics -, Tsukuba, Japan, November 20-22, 200
Heavy-light meson in anisotropic lattice QCD
We examine whether the improved quark action on anisotropic lattices
can be used as a framework for the heavy quark, which enables precision
computation of matrix elements of heavy-light mesons. To this end, it is
crucial to verify that a mass independent and nonperturbative tuning of the
parameters is possible. As a first step, we observe the dispersion relation of
heavy-light mesons on a quenched lattice using the action which is
nonperturbatively tuned only for the leading terms. On a lattice with the
spatial cutoff 1.6 GeV and the anisotropy , the
relativity relation holds within 2% accuracy in the quark mass region with the bare anisotropy parameter tuned for the massless quark.
We also apply the action to a calculation of heavy-light decay constants in the
charm quark mass region.Comment: Lattice2002(heavyquark), 3 pages, 2 figure
Interacting Bose and Fermi gases in low dimensions and the Riemann hypothesis
We apply the S-matrix based finite temperature formalism to non-relativistic
Bose and Fermi gases in 1+1 and 2+1 dimensions. In the 2+1 dimensional case,
the free energy is given in terms of Roger's dilogarithm in a way analagous to
the relativistic 1+1 dimensional case. The 1d fermionic case with a
quasi-periodic 2-body potential provides a physical framework for understanding
the Riemann hypothesis.Comment: version 3: additional appendix explains how the to
duality of Riemann's follows from a special modular
transformation in a massless relativistic theor
- …