4,352 research outputs found
Study of design parameters for squeeze film air journal bearing â excitation frequency and amplitude
The paper presents a design of squeeze film air journal bearing based on the design rules derived from CFX and FEA simulation study of an air film in between two flat plates, one of which was driven in a sinusoidal manner. The rules are that the oscillation frequency should be at least 15 kHz and that the oscillation amplitude be as large as possible to ensure a greater film thickness and to allow the bearing to reach its stable equilibrium quickly. The proposed journal bearing is made from AL2024-T3, of 20.02 mm outer diameter, 600 mm length and 2 mm thickness. Three 20-mm long fins are on the outer surface of the bearing tube and are spaced 120° apart; three longitudinal flats are milled equi-spaced between the fins and two piezoelectric actuators are mounted lengthwise on each flat. Such a design produces a modal shape on the bearing tube which resembles a triangle. When excited in this mode at the frequency of 16.37 kHz, and a voltage of 75 V AC with 75 V DC offset acting on the piezoelectric actuators, the air gap underneath of the bearing tube behaves as a squeeze air film with a response amplitude of 3.22 μm. The three design rules were validated by experiments
On the duality relation for correlation functions of the Potts model
We prove a recent conjecture on the duality relation for correlation
functions of the Potts model for boundary spins of a planar lattice.
Specifically, we deduce the explicit expression for the duality of the n-site
correlation functions, and establish sum rule identities in the form of the
M\"obius inversion of a partially ordered set. The strategy of the proof is by
first formulating the problem for the more general chiral Potts model. The
extension of our consideration to the many-component Potts models is also
given.Comment: 17 pages in RevTex, 5 figures, submitted to J. Phys.
Entangling two superconducting LC coherent modes via a superconducting flux qubit
Based on a pure solid-state device consisting of two superconducting LC
circuits coupled to a superconducting flux qubit, we propose in this paper that
the maximally entangled coherent states of the two LC modes can be generated
for arbitrary coherent states through flux qubit controls.Comment: 5 pages, 2 figure
New Results for the Correlation Functions of the Ising Model and the Transverse Ising Chain
In this paper we show how an infinite system of coupled Toda-type nonlinear
differential equations derived by one of us can be used efficiently to
calculate the time-dependent pair-correlations in the Ising chain in a
transverse field. The results are seen to match extremely well long large-time
asymptotic expansions newly derived here. For our initial conditions we use new
long asymptotic expansions for the equal-time pair correlation functions of the
transverse Ising chain, extending an old result of T.T. Wu for the 2d Ising
model. Using this one can also study the equal-time wavevector-dependent
correlation function of the quantum chain, a.k.a. the q-dependent diagonal
susceptibility in the 2d Ising model, in great detail with very little
computational effort.Comment: LaTeX 2e, 31 pages, 8 figures (16 eps files). vs2: Two references
added and minor changes of style. vs3: Corrections made and reference adde
Integrability as a consequence of discrete holomorphicity: the Z_N model
It has recently been established that imposing the condition of discrete
holomorphicity on a lattice parafermionic observable leads to the critical
Boltzmann weights in a number of lattice models. Remarkably, the solutions of
these linear equations also solve the Yang-Baxter equations. We extend this
analysis for the Z_N model by explicitly considering the condition of discrete
holomorphicity on two and three adjacent rhombi. For two rhombi this leads to a
quadratic equation in the Boltzmann weights and for three rhombi a cubic
equation. The two-rhombus equation implies the inversion relations. The
star-triangle relation follows from the three-rhombus equation. We also show
that these weights are self-dual as a consequence of discrete holomorphicity.Comment: 11 pages, 7 figures, some clarifications and a reference adde
Design of equipment safety & reliability for an aseptic liquid food packaging line through maintenance engineering
The organisation of maintenance, in the Aseptic Liquid Food (ALF) industry, represents an important management task that enables a company to pursue higher manufacturing effectiveness and improved market share. This research is concerned with the process to design and implement maintenance tasks. These two complementary processes (design and implementation) have been thought and designed to answer the particular needs of food industry regarding product safety and equipment reliability. Numerous maintenance engineering researchers have focused on maintenance engineering and reliability techniques highlighting the contribution of maintenance in achieving world class manufacturing and competitive advantage. Their outcome emphasizes that maintenance is not a ânecessary evilâ because of costs associated, but it can be considered an âinvestmentâ that produces an added value which generates a real company profit. The existing maintenance engineering techniques pursue equipment reliability at minimum cost; but in food industry, food safety represents the most critical issue to address and solve. The research methodology chosen is based on case studies coming from ALF industries. These show that low maintenance effectiveness could have dramatic effects on final consumers and on the companyâs image and underline the need of a maintenance design and implementation process that takes into consideration all critical factors relevant to liquid food industry. The analysis of measurable indicators available, represents a tool necessary to show the status of critical performance indicators and reveals the urgency of a research necessary to address and solve the maintenance problems in food industry. The literature review underlines the increasing regulations in place in food industry and that no literature is available to define a maintenance design and implementation process for ALF and in general for food industry. The literature review enabled also the gap existing between theory and real maintenance status, in the ALF, to be identified and the aim of the research was to explore this gap. The analysis of case studies and Key Performance Indicators (KPIâs) available highlights the problem and the literature review provides the knowledge necessary to identify the process to design and implement maintenance procedures for ALF industry. The research findings provide a useful guide to identify the process to design maintenance tasks able to put under control food safety and equipment reliability issues. Companyâs restraining forces and cultural inertia, that work against new maintenance procedures, have been analysed and a maintenance implementation process have been designed to avoid losing the benefits produced by the design phase. The analysis of condition monitoring systems shows devices and techniques useful to improve product safety, equipment reliability, and then maintenance effectiveness. This research aimed to fill the gap in the existing literature showing the solution to manage both food safety and production effectiveness issues in food industry. It identifies a maintenance design process able to capture all conceivable critical factors in food industry and to provide the solution to design reliable task lists. Furthermore, the maintenance implementation process shows the way to maximize the maintenance design outcome through the empowerment of equipment operators and close cooperation with maintenance and quality specialists. The new maintenance design and implementation process represents the answer to the research problem and a reliable solution that allows the food industry to improve food safety and production effectiveness.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Bosonic Super Liouville System: Lax Pair and Solution
We study the bosonic super Liouville system which is a statistical
transmutation of super Liouville system. Lax pair for the bosonic super
Liouville system is constructed using prolongation method, ensuring the Lax
integrability, and the solution to the equations of motion is also considered
via Leznov-Saveliev analysis.Comment: LaTeX, no figures, 11 page
Surface Critical Phenomena and Scaling in the Eight-Vertex Model
We give a physical interpretation of the entries of the reflection
-matrices of Baxter's eight-vertex model in terms of an Ising interaction at
an open boundary. Although the model still defies an exact solution we
nevertheless obtain the exact surface free energy from a crossing-unitarity
relation. The singular part of the surface energy is described by the critical
exponents and , where controls the strength of the four-spin
interaction. These values reduce to the known Ising exponents at the decoupling
point and confirm the scaling relations
and .Comment: 12 pages, LaTeX with REVTEX macros needed. To appear in Physical
Review Letter
The Chiral Potts Models Revisited
In honor of Onsager's ninetieth birthday, we like to review some exact
results obtained so far in the chiral Potts models and to translate these
results into language more transparent to physicists, so that experts in Monte
Carlo calculations, high and low temperature expansions, and various other
methods, can use them. We shall pay special attention to the interfacial
tension between the state and the state. By examining
the ground states, it is seen that the integrable line ends at a superwetting
point, on which the relation is satisfied, so that it
is energetically neutral to have one interface or more. We present also some
partial results on the meaning of the integrable line for low temperatures
where it lives in the non-wet regime. We make Baxter's exact results more
explicit for the symmetric case. By performing a Bethe Ansatz calculation with
open boundary conditions we confirm a dilogarithm identity for the
low-temperature expansion which may be new. We propose a new model for
numerical studies. This model has only two variables and exhibits commensurate
and incommensurate phase transitions and wetting transitions near zero
temperature. It appears to be not integrable, except at one point, and at each
temperature there is a point, where it is almost identical with the integrable
chiral Potts model.Comment: J. Stat. Phys., LaTeX using psbox.tex and AMS fonts, 69 pages, 30
figure
Quantitative impurities effects on temperatures of tin and aluminium fixed-point cells
The International Temperature Scale of 1990 (ITS-90) defines the present S.I.(âSystem Internationalâ) means of measuring temperature. The ITS-90 uses the freezing points of metals to define temperature fixed points. It also uses long-stemplatinum resistance thermometers to interpolate between the fixed points from 660 °Cdown to 84 K (if one includes the Argon triple point). Impurities are a major source of uncertainty in the fixed point temperature (of the order of 1 mK). And a better understanding of the impurity effect is required to improve top-level metrologicalthermometry. Most historical experiments with impurities have worked at a muchhigher levels of impurities â say of the order of 100ppm - and in arrangements that are not used on a day-to-day basis in a metrology laboratory. This thesis describes the deliberate doping of tin and aluminium, each with three different impurities and the effects of these on the temperature of the tin and aluminium liquid-solid phase transitions. The impurities, of the order of 1-30 ppm,were Co, Pb and Sb in the tin and Cu, Si and Ti in the aluminium. The tin and aluminium samples were in the form of ~0.3 kg ingots that would normally be used to realise an ITS-90 fixed point. Measurements were made using equipment normally available in a metrological thermometry laboratory, rather than using specially prepared samples. The samples were chemically analysed (by Glow Discharge Mass Spectrometry(GD-MS)) before and after the doping. Using the amount of dopants introduced,and/or the chemical analysis data, the measured temperature changes were compared with those interpolated from the standard text. The experimental undoped liquid-solid transition curves were also compared against theoretical curves (calculated from atheoretical model MTDATA). The results obtained did not disagree with the Hansen interpolated values (though there was considerable uncertainty in some of the measurements (e.g. a factor of 2 ormore) due to the measurement of small changes. Within these uncertainties it indicatesthat the Sum of Individual Estimates (SIE) method of correcting for, at least, metal impurities in otherwise high purity metals remain valid. However the results also showed considerable discrepancies between the initial measured and calculated temperature shifts (based on the pre-existing impurities prior to doping) suggesting that there may be impurities that are not (separately) detected by the GD-MS method. There was evidence that the thermal history of the metal phase transitions can cause considerable segregation of some impurities, particularly those likely to increase the phase transition temperature through a peritectic (âpositiveâ impurities), and that the effects of this segregation can be clearly seen on the shape of the melting curves of thetin doped with Sb. Some of the aluminium doped with Ti freezing curves may also show evidence of aâconcave upâ shape at the start of the freezing curve, as previously calculated by MTDATA, though the effect is not as pronounced. All individual phase transition measurements - made over tens of hours â were repeated at least three times and found to be reproducible, hence providing a real dataset that can be used for comparison with theoretical models still under development.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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