bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Through‐Flow Calculation to Designand Performance Prediction of Centrifugal Compressor
Authors: Choi Y. S. , Kang S. H. 
Published: March 2007

A computer code predicting the flows through the centrifugal compressor with the radial vaneless diffuser was developed and applied to investigate the detailed flowfields, i.e.,
secondary flows and jet‐wake type flow pattern in design and off‐design conditions. Various
parameters such as slip factors, aerodynamic blockages, entropy generation and two‐zone
modeling which are widely used in design and performance prediction, were discussed.A control volume method based on a general curvilinear coordinate system was used to
solve the time‐averaged Navier–Stokes equations and SIMPLER algorithm was used
to solve the pressure linked continuity equation. The standard k − ε turbulence model was used to obtain the eddy viscosity. Performance of the code was verified using the measured data for the Eckardt impeller.
Theoretical Rotordynamic Coefficients of Labyrinth GasSeals: a Parametric Study on a Bulk Model
Authors: Forte Paola , Latini Fabio 
Published: March 2007

To date, available mathematical bulk models for the determination of linearized
rotordynamic coefficients of labyrinth gas seals yield results which are not always in good
agreement with the experimental ones. The object of this work is to discuss the limits of these models and to point out possible improvements and aspects that need further investigation.After a study of the steady flow characteristics with an FEM code, a parametric computer
program, based on a known two‐volume model, has been developed. A perturbation approach has been applied to the governing equations of the bulk model to calculate the stiffness and damping coefficients. Predicted coefficients are compared to the results of an earlier one‐volume model.The model has also been tested with different expressions of the axial velocities in the two volumes and different laws for leakage and shear stress. The theoretical results are compared to the published experimental ones, pointing out the small effect of the various parameters in improving the correlation and the need of more complex models.
Revisiting Rotor Rigid Body Modes: Parametric Study of Stability
Authors: Littrell Nathan B. , Muszynska Agnes , Goldman Paul 
Published: March 2007

This paper presents an analytical model of a rigid rotor supported in two fluid film bearings with an emphasis on predicting the instability threshold speed. The factors contributing to the stability of the rotor are discussed and presented graphically using root locus plots. The parametric study of the stability starts from the discussion of the rotor/bearing system with “mirror symmetry”. Three basic cases are considered:(i) Rotor with relatively small gyroscopic effect (small polar moment of inertia) and
relatively high transverse moment of inertia. It is found that the pivotal mode
instability exists, but the lateral mode controls stability.
(ii) Highly gyroscopic rotor (relatively large polar moment of inertia) with also relatively
low transverse moment of inertia. It is found that the pivotal mode is infinitely
stable and the lateral mode controls stability.
(iii) Highly gyroscopic rotor with relatively high transverse moment of inertia. It is
found that the pivotal mode exists and controls stability. The lateral mode always
exists.Both asymmetry in rotor geometry (location of center of mass with respect to the
bearings) and fluid bearing parameters (stiffness, damping) are considered. It is shown
that, for a given bearing asymmetry parameter, the maximum stability is achieved when
the geometric asymmetry parameter is of equal value. The recommendations on the
optimal design from the stability standpoint are given.
Mechanical Behavior of an Industrial Gas Turbine underFault Conditions, a Case History
Authors: Florjancic Stefan S. , Lively Noel , Thomas Richard 
Published: March 2007

The resolve of journal bearing field problems and the full vibrational assessment of an industrial gas turbine, simple cycle rotor train, ABB’s GTllN2 is presented. Three units
experienced several times damage of the journal bearings on the compressor end. The
analysis of the damage, including tests, indicated that insufficient jacking oil flow was the
cause. The jacking concept was corrected and starting history has proven reliable operation,
resulting in not one additional failure.During the same period, two last stage blades failed in one of the units damaging
neighboring blades additionally. The machine tripped under the unbalance. Some auxiliary
piping and the babbitt of the journal bearing was damaged. However, the rotor came to a safe stop with only some rubbing, and the turbine casing fulfilled its containment function
perfectly.In order to better understand the dynamic behavior of the train, an extensive vibration
measurement program was decided between Kentucky Utilities and ABB, and executed
by Bently Nevada. The results proved excellent rotor balance, verified original design
parameters, and no fluid induced instabilities were found. This joint effort allowed to fully
assess and prove the rotor dynamic integrity of the gas turbine.
Numerical and Experimental Investigations of CouplingEffects in Anisotropic Elastic Rotors
Authors: Irretier Horst , Jacquet-Richardet Georges , Reuter Frank 
Published: March 2007

It is known that in elastic disc‐shaft systems in particular, the one‐nodal‐diameter mode of the discs can be highly coupled with the bending modes of the shaft. Consequently, when the system rotates, the elastic modes of the flexible discs are coupled with the gyroscopic modes of the flexible shaft equipped with rigid discs. In the paper this coupling effect is investigated numerically and experimentally.A numerical model, based on a finite element cyclic symmetry approach, is presented. This model has been developed for studying the wheel‐shaft coupling effects on the global behavior of turbomachinery rotors. In order to better illustrate the phenomenon involved and to validate the model, the method is applied here to a thin tuned and detuned circular disc mounted on an elastic shaft. Related frequency and mode shapes of the rotating assembly are discussed. Additional experimental results, based on an experimental modal analysis technique for rotating structures, are presented. Both numerical and experimental results are compared.
On a counterexample of Garofalo ‐ Lin for a unique continuation of Schrödinger equation
Authors: Lee Will Y. 
Published: March 2007

Garofalo and Lin have given a counterexample for which
unique continuation fails for the Schrödinger equation

urn:x-wiley:20903332:media:ista503207:ista503207-math-0001

.Their counterexample consists of a Bessel function of the third
kind Kv(|x|) with the restriction that v cannot be an integer. In this
note we have removed the restriction.
A bulk queueing system under N‐policy with bilevel service delay discipline and start‐up time
Authors: Muh David C. R. 
Published: March 2007

The author studies the queueing process in a single‐server, bulk
arrival and batch service queueing system with a compound Poisson
input, bilevel service delay discipline, start‐up time, and a fixed
accumulation level with control operating policy. It is assumed that when
the queue length falls below a predefined level r(≥1), the system, with
server capacity R, immediately stops service until the queue length
reaches or exceeds the second predefined accumulation level N(≥r).
Two cases, with N ≤ R and N ≥ R, are studied.The author finds explicitly the probability generating function of
the stationary distribution of the queueing process and gives numerical
examples.
The method of lower and upper solutions for nth‐order periodic boundary value problems
Authors: Cabada Alberto 
Published: March 2007

In this paper we develop the monotone method in the presence of
lower and upper solutions for the problem

urn:x-wiley:20903332:media:ista737583:ista737583-math-0001

where f is a Carathéodory function. We obtain sufficient conditions for
f to guarantee the existence and approximation of solutions between a
lower solution α and an upper solution β for n ≥ 3 with either α ≤ β or
α ≥ β.For this, we study some maximum principles for the operator
Lu ≡ u(n) + Mu. Furthermore, we obtain a generalization of the method of mixed monotonicity considering f and u as vectorial functions.
Some performance measures for vacation models with a batch Markovian arrival process
Authors: Matendo Sadrac K. 
Published: March 2007

We consider a single server infinite capacity queueing system, where
the arrival process is a batch Markovian arrival process (BMAP).
Particular BMAPs are the batch Poisson arrival process, the Markovian
arrival process (MAP), many batch arrival processes with correlated
interarrival times and batch sizes, and superpositions of these processes.
We note that the MAP includes phase‐type (PH) renewal processes and
non‐renewal processes such as the Markov modulated Poisson process
(MMPP).The server applies Kella′s vacation scheme, i.e., a vacation policy
where the decision of whether to take a new vacation or not, when the
system is empty, depends on the number of vacations already taken in
the current inactive phase. This exhaustive service discipline includes the
single vacation T‐policy, T(SV), and the multiple vacation T‐policy,
T(MV). The service times are i.i.d. random variables, independent of
the interarrival times and the vacation durations. Some important
performance measures such as the distribution functions and means of
the virtual and the actual waiting times are given. Finally, a numerical
example is presented.
Comments on a single server queue
Authors: Syski Ryszard 
Published: March 2007

A review of the work of V.E. Benĕs and P. Brémaud on a single‐server queue
G/G/1 is interpreted in terms of point processes and associated martingales.A concept of a discounted workload is introduced, and its connection with
random Dirichlet series and associated semigroups is investigated.
Sojourn times
Authors: Takács Lajos 
Published: March 2007

Let {ζ(u), u ≥ 0} be a stochastic process with state space A ∪ B where A and
B are disjoint sets. Denote by β(t) the total time spent in state B in the interval
(0, t). This paper deals with the problem of finding the distribution of β(t) and
the asymptotic distribution of β(t) as t → ∞ for various types of stochastic processes. The main result is a combinatorial theorem which makes it possible to find
in an elementary way, the distribution of β(t) for homogeneous stochastic processes with independent increments.This article is dedicated to the memory of Roland L. Dobrushin.
On the regularity of many‐particle dynamical systems perturbed by white noise
Authors: Skorokhod Anatoli V. 
Published: March 2007

We consider a system of finite number of particles that are moving in Rd under mutual interaction. It is assumed that the particles are subjected to some
additional random forces which cause diffusion motion of the particles. The latter is described by a system of stochastic differential equations of the first order
for noninertia particles and the second order for inertial particles. The coefficient of the system are unbounded because the interaction force tends to infinity
if the distance between two particles tends to zero. The system is called regular
if no particle can hit the other. We investigate conditions of regularity.This article is dedicated to the memory of Roland L. Dobrushin.
Population‐size‐dependent branching processes
Authors: Jagers Peter 
Published: March 2007

In a recent paper [7] a coupling method was used to show that if population
size, or more generally population history, influence upon individual reproduction
in growing, branching‐style populations disappears after some random time, then
the classical Malthusian properties of exponential growth and stabilization of composition persist. While this seems self‐evident, as stated, it is interesting that it
leads to neat criteria via a direct Borel‐Cantelli argument: If m(n) is the expected number of children of an individual in an n‐size population and m(n) ≥ m > 1,
then essentially

urn:x-wiley:20903332:media:ista678052:ista678052-math-0001

suffices to guarantee Malthusian behavior with the same parameter as a limiting
independent‐individual process with expected offspring number m. (For simplicity the criterion is stated for the single‐type case here.)However, this is not as strong as the results known for the special cases of
Galton‐Watson processes [10], Markov branching [13], and a binary splitting
tumor model [2], which all require only something like

urn:x-wiley:20903332:media:ista678052:ista678052-math-0002

.This note studies such latter criteria more generally. It is dedicated to the
memory of Roland L. Dobrushin.
Descriptors for point processes based on runs: the Markovian arrival process
Authors: Neuts Marcel F. 
Published: March 2007

This paper is part of a broader investigation of properties of a point process
that can be identified by imagining that the process is involved in a competition
for the generation of runs of events. The general purpose of that methodology is
to quantify the prevalence of gaps and bursts in realizations of the process. The
Markovian arrival process (MAP) is highly versatile in qualitative behavior and
its analysis is numerically tractable by matrix‐analytic methods. It can therefore
serve well as a benchmark process in that investigation. In this paper, we consider the MAP and a regular grid competing for runs of lengths at least r1 and
r2, respectively. A run of length r in one of the processes is defined as a string of
r successive events occurring without an intervening event in the other process.This article is dedicated to the memory of Roland L. Dobrushin.
The structure distribution in a mixed Poisson process
Authors: Teugels Jozef L. , Vynckier Petra 
Published: March 2007

We use a variety of real inversion formulas to derive the structure distribution in a mixed Poisson process. These approaches should prove to be useful in
applications, e.g., in insurance where such processes are very popular.This article is dedicated to the memory of Roland L. Dobrushin.
On applications of excess level processes to (N,D)‐policy bulk queueing systems
Authors: Dshalalow Jewgeni H. 
Published: March 2007

The paper deals with queueing systems in which N‐ and D‐policies are
combined into one. This means that an idle or vacationing server will resume his
service if the queueing or workload process crosses some specified fixed level N or
D, respectively. For the proposed (N, D)‐policy we study the queueing processes in
models with and without server vacations, with compound Poisson input, and
with generally distributed service and vacation periods. The analysis of the
models is essentially based on fluctuation techniques for two‐dimensional marked
counting processes newly developed by the author. The results enable us to arrive
at stationary distributions for the embedded and continuous time parameter
queueing processes in closed analytic forms, enhancing the well‐known Kendall
formulas and their modifications.This article is dedicated to the memory of Roland L. Dobrushin.
The empirical TES methodology: modeling empirical time series
Authors: Melamed Benjamin 
Published: March 2007

TES (Transform‐Expand‐Sample) is a versatile class of stochastic sequences defined via an autoregressive scheme with modulo‐1 reduction and
additional transformations. The scope of TES encompasses a wide variety
of sample path behaviors, which in turn give rise to autocorrelation functions with diverse functional forms ‐ monotone, oscillatory, alternating,
and others. TES sequences are readily generated on a computer, and their
autocorrelation functions can be numerically computed from accurate
analytical formulas at a modest computational cost.This paper presents the empirical TES modeling methodology which
uses TES process theory to model empirical records. The novel feature of
the TES methodology is that it expressly aims to simultaneously capture
the empirical marginal distribution (histogram) and autocorrelation function. We draw attention to the non‐parametric nature of TES modeling in
that it always guarantees an exact match to the empirical marginal distribution. However, fitting the corresponding autocorrelation function calls
for a heuristic search for a TES model over a large parametric space. Consequently, practical TES modeling of empirical records must currently rely
on software assistance. A visual interactive software environment, called
TEStool, has been designed and implemented to support TES modeling.
The paper describes the empirical TES modeling methodology as implemented in TEStool and provides numerically‐computable formulas for
TES autocorrelations. Two examples illustrate the efficacy of the TES
modeling approach. These examples serve to highlight the ability of TES
models to capture first‐order and second‐order properties of empirical
sample paths and to mimic their qualitative appearance.
The theory of networks of single server queues and the tandem queue model
Authors: Le Gall Pierre 
Published: March 2007

We consider the stochastic behavior of networks of single server queues
when successive service times of a given customer are highly correlated.
The study is conducted in two particular cases: 1) networks in heavy
traffic, and 2) networks in which all successive service times have the same
value (for a given customer), in order to avoid the possibility of breaking
up the busy periods. We then show how the local queueing delay (for an
arbitrary customer) can be derived through an equivalent tandem queue on
the condition that one other local queueing delay is added: the jitter delay
due to the independence of partial traffic streams.We consider a practical application of the results by investigating the
influence of long packets on the queueing delay of short packets in modern
packet switched telecommunication networks. We compare these results
with the results given by traffic simulation methods to conclude that there
is good agreement between results of calculation and of traffic simulation.
pH dependence of the protein orientation in self‐assembled bacteriorhodopsin/polycation multilayer films
Authors: Jussila Tapio , Li Meiling , Tkachenko Nikolai V. , Parkkinen Sinikka , Li Baofang , Jiang Long , Lemmetyinen Helge 
Published: March 2007

Bacteriorhodopsin (bR) multilayer films were successfully prepared by alternatingdepositions
of cationic poly(diallyldimethylammonium chloride) (PDAC) polyelectrolyte and purple membrane (PM). The
advantage of the method when compared to other thin film techniques is its simplicity to prepare large selfassembled
films. The orientations of the bR molecules in the films were studied by a transient photovoltage
method. The polarity of the photoresponse signals showed that in basic conditions the cytoplasmic side of PM
was adsorbed onto the polyelectrolyte layer, whereas in acidic conditions the extracellular side was adsorbed
onto the polyelectrolyte layer. The photocycle of the bR in the films was studied by usingthe conventional
flash photolysis method. The photochemical behavior of bR in dry polycationic films was similar to that in
other types of dry films and the intermediate lifetimes were almost independent of the protein orientation.The photovoltage signals introduce opposite proton transport directions for the formation of the K intermediate
of the photocycle and for the successive relaxation to M intermediate. The charge displacement
associated to the M intermediate was several times greater than that of the K intermediate. The fittings of the
transient photovoltage signals resulted the values of 2, 15, and 70 microseconds for the time constants of
the 3‐exponential formation of the M intermediate. The kinetic data were compared to the results obtained
with the transient absorption measurements.
Photolysis of dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) in aqueous solution and dispersed on solid supports
Authors: Aguer Jean-Pierre , Blachère Frédéric , Boule Pierre , Garaudee Sandrine , Guillard Chantal 
Published: March 2007

Dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) was exposed to UV light in aqueous solution.
It was also irradiated in the solid phase without support or adsorbed on laponite (a synthetic clay) and
ferric oxide.Two main photoproducts (1) and (2) were identified in irradiated aqueous solutions. Both involve the
substitution of chlorine by OH. The unexpected product (2) is formed through a kinetic reaction of primary
product; it results from an oxidation and it is not formed in the absence of oxygen.A huge number of intermediate products were simultaneously formed when dicamba is irradiated in the
solid phase in presence of laponite. They correspond to methylation, decarboxylation, chlorination, dechlorination,
and hydroxylation reactions. The latter is probably due to the presence of water in clays, whereas
methylation, chlorination and decarboxylation have been attributed to the cage effect and to an energy transfer
process. Without support or with ferric oxide, no decarboxylation occurs. The nature of the inorganic
support also modify the kinetics of dicamba photolysis.
Laser induced desorption and ablation: mechanism of metal removal from an Al‐Cu‐Fe alloy and a quasicrystal of the same composition
Authors: Satta Mauro , Liu Haichen , Mao Xianglei , Moretti Giuliano , Russo Richard E. , Giardini Anna , Mele Aldo 
Published: March 2007

Quasicrystals are a special class of metallic alloys that share some of the properties of crystals.
Their structures reduce to a single repeating unit like that of the unit cell of a crystal. The quasi‐unitcell
is representative of a cluster like structure where electrons cannot move with freedom as in metals.
Quasicrystals are formed of metallicelements but they do not have metallic properties.The diversity of the fractionation behavior induced by laser desorption and ablation of the Al70Cu20Fe10 of the intermetallicalloy and of the Al65Cu23Fe12 quasicrystal has been examined in terms of the structural
properties of the two compounds. Elemental fractionation during laser desorption and ablation sampling
was investigated by using inductively coupled plasma mass spectrometry. The experiments were carried out
in two different irradiance regimes by a Nd‐YAG laser with 266 nm wavelength and single 6 nanosecond laser
pulses. In the high irradiance regime (>0.04, 0.07GW/cm2) the effect of the laser irradiance is not discriminating.
In the low irradiance regime (<0.04, 0.07GW/cm2) large differences have been found between the
alloy and the quasicrystal. The results have been interpreted on the basis of a thermodynamic vaporization
process for the intermetallic alloy. An electronic model of localized excitation is suggested for the physical
process of surface material removal from a quasicrystal.