716 research outputs found
Dynamics of the inlet system of a four-stroke engine
Tests were run on a single-cylinder and a multicylinder four-stroke engine in order to determine the effect of the dynamics of the inlet system upon indicated mean effective pressure. Tests on the single-cylinder engine were made at various speeds, inlet valve timings, and inlet pipe lengths. These tests indicated that the indicated mean effective pressure could be raised considerably at any one speed by the use of a suitably long inlet pipe. Tests at other speeds with this length of pipe showed higher indicated mean effective pressure than with a very short pipe, although not so high as could be obtained with the pipe length adjusted for each speed. A general relation was discovered between optimum time of inlet valve closing and pipe length; namely, that longer pipes require later inlet valve closing in order to be fully effective. Tests were also made on three cylinders connected to a single pipe. With this arrangement, increased volumetric efficiency at low speed was obtainable by using a long pipe, but only with a sacrifice of volumetric efficiency at high speed. Volumetric efficiency at high speed was progressively lower as the pipe length was increased
Computer mapping of LANDSAT data for environmental applications
The author has identified the following significant results. Land cover overlays and maps produced from LANDSAT are providing information on existing land use and resources throughout the 208 study area. The overlays are being used to delineate drainage areas of a predominant land cover type. Information on cover type is also being combined with other pertinent data to develop estimates of sediment and nutrients flows from the drainage area. The LANDSAT inventory of present land cover together with population projects is providing a basis for developing maps of anticipated land use patterns required to evaluate impact on water quality which may result from these patterns. Overlays of forest types were useful for defining wildlife habitat and vegetational resources in the region. LANDSAT data and computer assisted interpretation was found to be a rapid cost effective procedure for inventorying land cover on a regional basis. The entire 208 inventory which include acquisition of ground truth, LANDSAT tapes, computer processing, and production of overlays and coded tapes was completed within a period of 2 months at a cost of about 0.6 cents per acre, a significant improvement in time and cost over conventional photointerpretation and mapping techniques
On the Vortex-Point Charge Composite: Classical Orbits and Quantum Bound States
The possibility of composite systems arising out of a point charge
interacting with a Nielsen-Olesen vortex in 2+1-dimensions is investigated. It
is shown that classical bounded orbits are possible for certain ranges of
parameters. Long lived metastable states are shown to exist, in a
semi-classical approach, from the study of the effective potential. Loss of
self-adjointness of the Hamiltonian and its subsequent self-adjoint extension
in some cases leads to bound states.Comment: 13 pages, Latex file, For figures e-mail to
"[email protected]
Numerical Simulation of Vortex Crystals and Merging in N-Point Vortex Systems with Circular Boundary
In two-dimensional (2D) inviscid incompressible flow, low background
vorticity distribution accelerates intense vortices (clumps) to merge each
other and to array in the symmetric pattern which is called ``vortex
crystals''; they are observed in the experiments on pure electron plasma and
the simulations of Euler fluid. Vortex merger is thought to be a result of
negative ``temperature'' introduced by L. Onsager. Slight difference in the
initial distribution from this leads to ``vortex crystals''. We study these
phenomena by examining N-point vortex systems governed by the Hamilton
equations of motion. First, we study a three-point vortex system without
background distribution. It is known that a N-point vortex system with boundary
exhibits chaotic behavior for N\geq 3. In order to investigate the properties
of the phase space structure of this three-point vortex system with circular
boundary, we examine the Poincar\'e plot of this system. Then we show that
topology of the Poincar\'e plot of this system drastically changes when the
parameters, which are concerned with the sign of ``temperature'', are varied.
Next, we introduce a formula for energy spectrum of a N-point vortex system
with circular boundary. Further, carrying out numerical computation, we
reproduce a vortex crystal and a vortex merger in a few hundred point vortices
system. We confirm that the energy of vortices is transferred from the clumps
to the background in the course of vortex crystallization. In the vortex
merging process, we numerically calculate the energy spectrum introduced above
and confirm that it behaves as k^{-\alpha},(\alpha\approx 2.2-2.8) at the
region 10^0<k<10^1 after the merging.Comment: 30 pages, 11 figures. to be published in Journal of Physical Society
of Japan Vol.74 No.
A Single Scale Theory for Cold and Hot Dark Matter
We show that a recently proposed extension of the MSSM can provide a scenario
where both the cold and hot dark matter of the universe owe their origin to a
single scale connected with the breakdown of the global B-L symmetry. The susy
partner of the majoron and the light Majorana neutrinos are the cold and hot
dark matter candidates respectively in this model and their desired relative
abundances emerge when the scale of B-L symmetry breaking is in the TeV range.Comment: UMD-PP-94-102 (latex file; 15 pages
Three-dimensional coherent X-ray diffraction imaging of a ceramic nanofoam: determination of structural deformation mechanisms
Ultra-low density polymers, metals, and ceramic nanofoams are valued for
their high strength-to-weight ratio, high surface area and insulating
properties ascribed to their structural geometry. We obtain the labrynthine
internal structure of a tantalum oxide nanofoam by X-ray diffractive imaging.
Finite element analysis from the structure reveals mechanical properties
consistent with bulk samples and with a diffusion limited cluster aggregation
model, while excess mass on the nodes discounts the dangling fragments
hypothesis of percolation theory.Comment: 8 pages, 5 figures, 30 reference
Quasi-stationary States of Two-Dimensional Electron Plasma Trapped in Magnetic Field
We have performed numerical simulations on a pure electron plasma system
under a strong magnetic field, in order to examine quasi-stationary states that
the system eventually evolves into. We use ring states as the initial states,
changing the width, and find that the system evolves into a vortex crystal
state from a thinner-ring state while a state with a single-peaked density
distribution is obtained from a thicker-ring initial state. For those
quasi-stationary states, density distribution and macroscopic observables are
defined on the basis of a coarse-grained density field. We compare our results
with experiments and some statistical theories, which include the
Gibbs-Boltzmann statistics, Tsallis statistics, the fluid entropy theory, and
the minimum enstrophy state. From some of those initial states, we obtain the
quasi-stationary states which are close to the minimum enstrophy state, but we
also find that the quasi-stationary states depend upon initial states, even if
the initial states have the same energy and angular momentum, which means the
ergodicity does not hold.Comment: 9 pages, 7 figure
âIt's my language, my culture and it's personal!â Migrant mothers' experience of language use and identity change in their relationship with their children: an interpretative phenomenological analysis
The question of how migrantsâ language use impacts their ethnic identity has received considerable attention in the literature. There is, however, little understanding of how this relationship manifests or is negotiated in interethnic families. This paper presents an in-depth exploration of Spanish mothersâ experiences of Spanish- and English-language interactions with their English-born children. Semi-structured interviews were conducted with Spanish mothers living in Britain in interethnic partnerships and transcripts were subjected to interpretative phenomenological analysis. Analysis reveals a process of identity change where participantsâ shifting ethnic identifications with host and heritage culture is intimately related to their language use with their children. Pivotal to this process is the participantsâ need to maintain their âSpanish motherâ identity, a desire that can only be fulfilled by transferring their heritage language to their children and speaking it with them. Findings reveal how this dynamic impacts perception of family roles, relationship quality and psychological well-being
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