bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of monopolar vortices in a strain flow
Authors: TRIELING R. R. , BECKERS M. , VAN HEIJST G. J. F.
Published: July 2002

The strain-induced evolution of shielded monopolar vortices has
been

investigated

in a stratified fluid. A steady strain flow was generated by an arrangement
of four

rotating horizontal discs, whereas the monopolar vortex was created by
a small

spinning sphere. Quantitative information about the flow field was obtained
by

tracking passive tracer particles. The vortex was observed to deform into
a

tripolar-like structure, followed by the shedding of the accompanying satellites.

During this stage,

the remaining vortex core evolved quasi-steadily, which was evident from
the

functional relationship between the vorticity and the stream function.

Furthermore, it

was shown that the removal of the surrounding ring of oppositely signed
vorticity

induces an accelerated horizontal growth of the vortex core. Owing to the
diffusive

decay of vorticity, the vortex was finally torn apart along the horizontal

strain axis.

The dynamics of the vortex core appeared to be very similar to that of
an elliptic

patch of uniform vorticity. The instantaneous vorticity contours at high
vorticity

levels were close to ellipses with nearly the same aspect ratios and orientations.

Moreover, the observed vortex evolution was in qualitative agreement with
the

calculated motion of an elliptic patch of uniform vorticity.

As a second approach, the

full two-dimensional vorticity equation was solved numerically by a finite-difference

method in order to account for both the non-uniform spatial vorticity distribution
of

the laboratory vortex and the diffusion of vorticity in

the horizontal directions. The

numerically obtained vortex evolution was in good agreement with that observed
in

the laboratory.
Shocks and energy dissipation in inviscid fluids:

a question posed by Lord Rayleigh
Authors: BROADWELL JAMES E.
Published: July 2002

Lord Rayleigh argued that after a discontinuity develops in a

one-dimensional compression wave in an ideal inviscid fluid some

sort of motion must continue. Arguments

are given in support of this view and a suggestion is made as to what that
motion

might be. The relationship of this motion to that proposed by Onsager for

incompressible inviscid turbulent flows is discussed.
On the application of the Kelvin–Arnol'd

energy principle to the stability of forced

two-dimensional inviscid flows
Authors: DAVIDSON P. A.
Published: July 2002

Arnol'd developed two distinct yet closely

related approaches to the linear stability of

Euler flows. One is widely used for two-dimensional flows

and involves constructing

a conserved functional whose first variation vanishes and

whose second variation

determines the linear (and nonlinear) stability of the motion.

The second method

is a refinement of Kelvin's energy principle which states

that stable steady Euler

flows represent extremums in energy under a virtual

displacement of the vorticity

field. The conserved-functional (or energy-Casimir) method has

been extended by

several authors to more complex flows, such as planar MHD

flow. In this paper

we generalize the Kelvin–Arnol'd energy

method to two-dimensional inviscid flows

subject to a body force of the form −ϕ∇f.

Here ϕ is a materially conserved quantity

and f an arbitrary function of position and of ϕ.

This encompasses a broad class of

conservative flows, such as natural-convection planar and

poloidal MHD flow with the

magnetic field trapped in the plane of the motion, flows

driven by electrostatic forces,

swirling recirculating flow, self-gravitating flows and

poloidal MHD flow subject to

an azimuthal magnetic field. We show that stable steady

motions represent extremums

in energy under a virtual displacement of ϕ and of

the vorticity field. That is, d1E=0

at equilibrium and whenever d2E is

positive or negative definite the flow is (linearly)

stable. We also show that unstable normal modes must have

a spatial structure which

satisfies d2E=0. This provides a single

stability test for a broad class of flows, and

we describe a simple universal procedure for implementing

this test. In passing, a new

test for linear stability is developed. That is, we

demonstrate that stability is ensured

(for flows of the type considered here) whenever the

Lagrangian of the flow is a

maximum under a virtual displacement of the particle

trajectories, the displacement

being of the type normally associated with Hamilton's

principle. A simple universal

procedure for applying this test is also given. We apply our

general stability criteria

to a range of flows and recover some familiar results. We

also extend these ideas to

flows which are subject to more than one type of body force.

For example, a new

stability criterion is obtained (without the use of Casimirs)

for natural convection in

the presence of a magnetic field. Nonlinear stability is

also considered. Specifically,

we develop a nonlinear stability criterion for planar MHD

flows which are subject

to isomagnetic perturbations. This differs from previous

criteria in that we are able

to extend the linear criterion into the nonlinear regime.

We also show how to extend

the Kelvin–Arnol'd method to finite-amplitude

perturbations.
Low-dimensional control of the circular cylinder wake
Authors: GILLIES E. A.
Published: July 2002

Many wake flows exhibit self-excited flow oscillations which are
sustained by the flow
itself and are not caused by amplification of external noise. The archetypal
example
of a self-excited wake flow is the low Reynolds number flow past a circular
cylinder.
This flow exhibits self-sustained periodic vortex shedding above a critical
Reynolds
number. In general, control of such flows requires stabilization of many
globally
unstable modes; the present work describes a multiple-sensor control strategy
for the
cylinder wake which succeeds in controlling a simplified wake model at
a Reynolds
number above that at which single-sensor schemes fail.

Representation of the flow field by a finite set of coherent structures
or modes,
which are extracted by proper orthogonal decomposition and correspond to
the
large-scale wake components, allows the efficient design of a closed-loop
control
algorithm. A neural network is used to furnish an empirical prediction
of the modal
response of the wake to external control forcing. This model avoids the
need for
explicit representation of the control actuator–wake interaction.
Additionally, the
neural network structure of the model allows the design of a robust nonlinear

control algorithm. Furthermore the controller does not necessarily require
velocity
field information, but can control the wake using other quantities (for
example flow
visualization pictures) which characterize the structure of the velocity
field. Successful
control of a simplified cylinder wake model is used to demonstrate the
feasibility of
the low-dimensional control strategy.
Finite-amplitude Taylor-vortex flow of viscoelastic fluids
Authors: KHAYAT ROGER E.
Published: July 2002

The influence of inertia and elasticity on the onset and stability of Taylor-vortex flow
(TVF) is examined for an Oldroyd-B fluid. The Galerkin projection method is used
to obtain the departure from Couette flow (CF). Only axisymmetric flow is examined.
The solution is capable of capturing the dynamical behaviour observed experimentally
for viscoelastic fluids in the inertio-elastic and purely elastic ranges. For flow with
dominant inertia, the bifurcation picture is similar to that for a Newtonian fluid.
However, transition from CF to TVF is oscillatory because of fluid elasticity. Steady
TVF sets in, via supercritical bifurcation, as Re reaches a critical
value, Rec. The
critical Reynolds number decreases with fluid elasticity, and is strongly influenced by
fluid retardation. As elasticity exceeds a critical level, a subcritical bifurcation emerges
at Rec, similar to that predicted by the Landau–Ginzburg equation. It is found that
slip along the axial direction tends to be generally destabilizing. The coherence of the
formulation is established under steady and transient conditions through comparison
with exact linear stability analysis, experimental measurements, and flow visualization.
Good agreement is obtained between theory and the measurements of Muller et al.
(1993) in the limit of purely elastic overstable TVF.
Dust resuspension by the flow around an impacting sphere
Authors: EAMES I. , DALZIEL S. B.
Published: July 2002

A rigid body colliding with a layer of dust is capable of resuspending dust through
two distinct mechanisms: a ballistic mechanism, where kinetic energy is transferred
from the impacting body to dust particles through direct contact, and a hydrodynamic
mechanism, where dust particles are resuspended by the flow disturbance generated
by the body. In this paper, we study the hydrodynamic resuspension mechanism by
considering the flow around a sphere moving either towards or away from a wall.
Experiments were performed using a sphere translating at a constant velocity for
Reynolds number, Re, in the range 300 to 3500, and at varying angles of approach
and departure from a wall. A wider range of Re was investigated by releasing
dense rigid spheres above the wall. The high Reynolds number flow past a steadily
translating sphere is characterized by a recirculating wake region behind the sphere.
When the sphere approaches the wall and stops on making contact with it, the wake
vortex which is initially behind the sphere threads over the sphere's surface, generating
a secondary vortex ring. The coherent structure, composed of the wake and secondary
vortices, strikes the wall and pushes fluid or dust, initially adjacent to the wall, to one
side. The resuspension of dust particles of diameter b which are initially at rest on
the wall is governed by a particle Shields' parameter, θp,
based on the sphere's impact velocity, U: θp =
ρfU2/
(ρp−ρf)bg,
where ρp and ρf are respectively the density of
the dust particles and fluid. The resuspension criterion is a function of particle Reynolds
number, Rep, based on the diameter
and fall velocity of the dust particles and occurs
when θp [ges ] θp,c where
θp,c ≈ 3.0 for Rep [gsim ] 1, and
θp,c ≈ 5.0/Re1/2p
for Rep [lsim ] 1. The
geometry of the region of dust resuspended by the sphere was studied as a function
of the impact velocity, angle of impact and the properties of the dust particles. When
the sphere impacts a thick layer of dust, the volume concentration of resuspended
dust is sufficiently high to generate a particle-driven gravity current which transports
the dust far from the point of impact. The dynamics of the gravity current were
determined as a function of dust particle properties and size of the impacting sphere.

A sphere moving impulsively from rest away from a wall is found not to play a
significant role in the resuspension of dust; however trailing vorticity generated on
the surface of the sphere advects a large volume of fluid away from the wall, which
may contain dust already in suspension.
A mathematical model for the analysis of variation in discourse
Authors: ROMERO TRILLO JESÚS
Published: July 2002

The present article discusses the notion of variation in discourse as an essential characteristic of language and the linguistic parameters that can be used for its study. The article describes the different traditions in the study of variation and places special emphasis on the role of prosodic analysis in the study of spoken discourse. The study explores the use of discourse markers in the London-Lund Corpus and describes their linguistic variation by introducing the notion of APPROPRIATENESS. This notion, which combines the quantitative and qualitative presence of elements in discourse, is based on a mathematical index that can describe discourse variation with a sound systematic criterion.
New classes of three-dimensional ideal-MHD equilibria
Authors: KAISER R. , SALAT A.
Published: July 2002

Six ansatzes are investigated for their potential to allow
three-dimensional (3D)
ideal magnetohydrodynamic (MHD) equilibria. The ansatzes are based on a
Clebsch representation for the magnetic field,
B=∇H × ∇k,
and a ‘generalized Clebsch representation’,
B=∇×(∇K × ∇k), with
∇k being one of the coordinate directions
of a cylindrical coordinate system. Three classes of equilibria, all with
a straight
magnetic axis, are obtained. Equilibria of the first class have a purely
poloidal
magnetic field of the Clebsch type with k=z and include
the 3D equilibria already
known. Equilibria of the other two classes have a purely toroidal (i.e.
here
longitudinal) magnetic field and pressure surfaces that can be chosen
such that poloidal
sections are closed. The second class is based on a Clebsch representation
with
k=θ. Solutions contain a free function of θ that
determines the poloidal sections
of the pressure surfaces at, say, z=0. The behaviour in the
toroidal direction is
then fixed but not periodic. For the third class, the generalized Clebsch
representation with k=z is used. The equilibria are
similar to those of the second class,
with two important differences. They contain no free function and field
lines are
not planar. Finally, 3D vacuum fields, which exhibit 3D magnetic surfaces,
are
presented. They have the same geometry as the equilibria of the third class,
and in
fact can be obtained as a certain limit from these equilibria. Possible
applications
of the equilibria found are mentioned.
Magnetohydrodynamic equations under anisotropic conditions
Authors: KINNEY R. , McWILLIAMS J. C.
Published: July 2002

Scaling analysis is used to derive approximations of magnetohydrodynamics
with self-consistent leading-order dynamics under general conditions of
anisotropy. Both incompressible and weakly compressible limits are considered.
The horizontal magnetic and velocity fields obey dynamics given by a reduced
closed set of equations, but the vertical components have different decoupled
dynamics in the different regimes. Conservation laws are also discussed.
It is
shown that the reduced equations are not self-consistent unless either
the ratio
of vertical to horizontal length scales is large or the fluid is gravitationally
stratified and the ratio of length scales is small. New equations are derived
for
a rotating stratified plasma, which are an extension of the quasigeostrophic
equations of neutral fluids.
Remarks on statistical mechanics of discrete and
continuous media with application to the magnetohydrodynamic dynamo
Authors: TURNER LEAF
Published: July 2002

In this paper commemorating the 60th birthday of David Montgomery,
issues
tantalizing to me that evolved from my collaborations with him are highlighted:
sustainment of the magnetohydrodynamic dynamo, relationships between
discrete and continuous models of media, and closures for nonlinear theories
of
discrete and continuous media. In particular, it is speculated that a tractable
statistical model of a magnetohydrodynamic dynamo may arise from a proper
formulation of a solenoidal expansion basis for the magnetic and velocity
fields
in the context of an appropriate closure, such as the eddy-damped quasinormal
Markovian model.
Dispersion of dipolar electromagnetic waves

in a radially inhomogeneous axially magnetized plasma column
Authors: GHANASHEV I. , ARESTOVA I. , TATAROVA E. , ZHELYAZKOV I. , STOYKOV Sv.
Published: July 2002

The wavelengths and attenuation coefficients of dipolar left and

right-hand circularly polarized waves in a radially inhomogeneous axially

magnetized plasma

column are computed by means of step approximation of the radial plasma
density

profile. A comparison with theoretical results assuming radial plasma homogeneity

shows that the radial plasma inhomogeneity is significant for wave propagation.
In

particular, it facilitates the occurrence of backward waves and increases
by up to

one order of magnitude the wave attenuation coefficient compared with a

homogeneous plasma column having the same average plasma density.
Theory of stimulated scattering of large-amplitude waves
Authors: STENFLO L.
Published: July 2002

A nonlinear dispersion relation that governs the interaction between
a high-frequency pump wave and the low-frequency modes in a plasma is derived.

Previous results are generalized and discussed.
Wave interactions in magnetohydrodynamics,
and cosmic-ray-modified shocks
Authors: WEBB G. M. , ZAKHARIAN A. , BRIO M. , ZANK G. P.
Published: July 2002

Multiple-scales perturbation methods are used to study wave interactions in magnetohydrodynamics
(MHD), in one Cartesian space dimension, with application to
cosmic-ray-modified shocks. In particular, the problem of the propagation and interaction
of short wavelength MHD waves, in a large-scale background flow, modified by cosmic rays
is studied. The wave interaction equations consist of seven
coupled evolution equations for the backward and forward Alfvén waves, the backward
and forward fast and slow magnetoacoustic waves and the entropy wave. In
the linear wave regime, the waves are coupled by wave mixing due to gradients in
the background flow, cosmic-ray squeezing instability effects, and damping due to
the diffusing cosmic rays. In the most general case, the evolution equations also
contain nonlinear wave interaction terms due to Burgers self wave steepening for
the magnetoacoustic modes, resonant three wave interactions, and mean wave field
interaction terms. The form of the wave interaction equations in the ideal MHD
case is also discussed. Numerical simulations of the fully nonlinear cosmic ray MHD
model equations are compared with spectral code solutions of the linear wave interaction
equations for the case of perpendicular, cosmic-ray-modified shocks. The
solutions are used to illustrate how the different wave modes can be generated by
wave mixing, and the modification of the cosmic ray squeezing instability due to
wave interactions. It is shown that the Alfvén waves are coupled to the magnetoacoustic
and entropy waves due to linear wave mixing, only in background flows
with non-zero field aligned electric current and/or vorticity
(i.e. if B·∇×B≠0
and/or B·∇×u≠0,
where B and u are the magnetic field induction and fluid
velocity respectively).
Temporal changes of feeding and absorption of biochemical components in Cerastoderma edule fed an algal diet
Authors: Ibarrola I. , Navarro E. , Iglesias J.I.P. , Urrutia M.B.
Published: July 2002

Temporal evolution of the ingestion and absorption rates of organic matter and biochemical components in the filter-feeding bivalve Cerastoderma edule (Mollusca: Bivalvia) fed for 12 d on the same ration (1.5 mm3 l−1) of the microalgae Tetraselmis suecica (Chlorophyta: Prasinophiceae) having different biochemical composition, were measured. Cockles in group E were fed algal cells harvested at the exponential growth phase (55.5% of protein, 16.8% of carbohydrate and 27.6% of lipids) whereas cockles in group S were fed cells harvested at the stationary growth phase (45.3% of protein, 35.2% of carbohydrate and 20.0% of lipids). After the feeding period cockles were submitted to starvation and biochemical analysis of faeces produced during final steps of gut evacuation (after 24–96 h of starvation) was performed to estimate biochemical composition of metabolic faecal losses (endogenous matter lost during the process of digestion).

Ingestion rate of organic matter was found to gradually increase during the feeding period in both groups. Absorption efficiency of organic matter decreased but reached an asymptotic minimum with rising ingestion rate. This relationship resulted in a gradual enhancement of absorption rate of organic matter over the time. Lipid fraction of food was found to be absorbed with significantly lower efficiency (even negative values were recorded in group S) than proteins and carbohydrates irrespective of the diet. Endogenous faecal losses presented high proportion of lipids (up to 66%) and lower proportions of proteins (∼25%) and carbohydrates (∼9%). On the other hand, increasing carbohydrate abundance in the diet brought about no apparent enhancement of carbohydrates absorption efficiency. Results are discussed in relation to the time-course of digestive enzyme activities.
The Scope of Perceptual Knowledge
Authors: Millar Alan
Published: July 2002

Plausibly perceptual knowledge satisfies the following: (1) It is knowledge about things from the way they appear. (2) It can embrace more than the way things appear. (3) It is phenomenologically immediate and thus, in one sense, non-inferential. (2) and (3) place a significant constraint on adequate elucidations of (1). Knowledge about an object, from the way it looks, which embraces more than the way it looks, should not turn out to be inferential in the relevant sense. The paper shows how this constraint can be met, drawing upon a conception of a discriminative capacity. The discussion touches on literature dealing with observation in science, knowledge of other minds, and the possibility of moral knowledge.
The Evolution of Language: Truth and Lies
Authors: Clark Stephen R. L.
Published: July 2002

There is both theoretical and experimental reason to suppose that no-one could ever have learned to speak without an environment of language-users. How then did the first language-users learn? Animal communication systems provide no help, since human languages aren't constituted as a natural system of signs, and are essentially recursive and syntactic. Such languages aren't demanded by evolution, since most creatures, even intelligent creatures, manage very well without them. I propose that representations, and even public representations like sculptures, precede full languages, which were devised by the first human children as secret tongues to create fantasy realms inaccessible to their proto-human parents. Language, in brief, is not required for truth-telling or for the convenience of hunters. It is a peculiar modification of public representation, which permits us to construct new public worlds.
Missing the entire point: Wittgenstein and religion
Authors: RICHTER DUNCAN
Published: July 2002

In this paper I contrast some widespread ideas about what Wittgenstein
said about religious belief with statements Wittgenstein made about his purposes
and method in doing philosophy, in order to argue that he did not hold the views
commonly attributed to him. These allegedly Wittgensteinian doctrines in fact
essentialize religion in a very un-Wittgensteinian way. A truly Wittgensteinian
philosophy of religion can only be a personal process, and there can be no part in it
for generalized hypotheses or conclusions about religion in general.

Why is it that in this case I seem to be missing the entire point?1
Swinburne's explanation of the universe
Authors: SMITH QUENTIN
Published: July 2002

Richard Swinburne, Is There a God?

Oxford: Oxford University Press, 1996, pp. vii+144.

Swinburne's Is There A God? presents a brief,

updated version of his book,

The Existence of God, in which Swinburne argued that

criteria used in scientific

reasoning could be used to argue that God probably exists.

This new book

is designed for a wider audience than professional philosophers.

Nonetheless, there much that is new and of interest to

philosophers in Is There a God? For

example, there is a discussion of Stephen Hawking's

cosmology, some new

ideas in the philosophy of mind, and a new way of formulating

the argument that theism is a simpler explanation of the

universe than is materialism.
The origin of man'yōgana
Authors: BENTLEY John R.
Published: July 2002

Most scholars in Japanese studies (history, linguistics, literature) tend to accept in one form or another the ancient legend that the phonetic writing system of ancient Japan, known as man'yōgana, came from Paekche. This legend about the ancient Korean kingdom—Paekche—appears in the Kojiki and Nihon shoki, Japan's two oldest chronicles. To date there have been few attempts to use concrete data from the peninsula either to prove or reject this legend. This article supplies information from all epigraphic data on the Korean peninsula to show that Paekche spread the use of Chinese (sinographs) to be used phonogrammatically and that Koguryo educated the rest of the peninsula in the use of this script.
Peter Trudgill, The dialects of England.
2nd ed. Oxford: Blackwell, 1999. Pp. x,154. Pb $26.95. Paul
Foulkes & Gerard Docherty (eds.), Urban voices:
Accent studies in the British Isles. London: Arnold,
1999. Pp. xiii, 313. Pb $24.95.
Authors: Gordon Matthew J.
Published: July 2002

Reports of the death of heterogeneity in British
speech have been greatly exaggerated. Most Language
in Society readers are certainly already aware of
this, and two recent books will help communicate this point
to people outside the field.
Are emotions so simple?
Authors: Ben-Ze'ev Aaron
Published: July 2002

Rolls's book, The brain and emotion is an important and valuable contribution to our understanding of the brain mechanisms that underlie emotional processes. Its explanatory value is less obvious when it comes to psychological and philosophical issues concerning the nature of emotions.
Keeping it simple, socially
Authors: Barrett Louise , Henzi Peter
Published: July 2002

Fast and frugal heuristics function accurately and swiftly over a wide range of decision making processes. The performance of these algorithms in the social domain would be an object for research. The use of simple algorithms to investigate social decision-making could prove fruitful in studies of nonhuman primates as well as humans
Emotion theory?
Authors: Frijda Nico H.
Published: July 2002

The book contains a masterly review of Rolls's single-neuron research reflecting rewards. It places that research in the context of the neo-behaviorist theory of emotions. That theory provides a useful first approximation to emotion-eliciting conditions but has little to tell about emotions as motivational states or response dispositions: nor does it give a rationale for what are considered to be primary rewarding stimuli.
Decision rules in behavioural ecology
Authors: Houston Alasdair I.
Published: July 2002

Gigerenzer, Todd, and the ABC Research Group give an interesting account of simple decision rules in a variety of contexts. I agree with their basic idea that animals use simple rules. In my commentary I concentrate on some aspects of their treatment of decision rules in behavioural ecology.
REM sleep: Desperately seeking isomorphism
Authors: Feinberg Irwin
Published: July 2002

If reports given on experimental awakenings validly represent mental activity that was underway before the awakening, REM sleep is neither necessary nor sufficient for dreaming. Another intuitively attractive hypothesis for its function – that REM consolidates or otherwise modifies memory traces acquired while awake – is not supported by the preponderant evidence. There is growing acceptance of the possibility that REM functions to support sleep rather than waking brain processes.

[Hobson et al.; Nielsen; Solms; Vertes & Eastman]
The importance of reporting the distributional criteria of FA
Authors: Walters Sally
Published: July 2002

Not all of the studies cited in the target article as evidence that fluctuating asymmetry (FA) predicts male mating success demonstrate that the observed asymmetry is, in fact, FA. FA is a population-level pattern of differences between sides. Unless the population-level distributional criteria of bilateral traits are reported, the meaning of asymmetry in individuals is unknown.
How to build a brain: Multiple memory systems have evolved and only some of them are constructivist
Authors: Black James E. , Greenough William T.
Published: July 2002

Much of our work with enriched experience and training in
animals supports the Quartz & Sejnowski (Q&S) thesis that
environmental information can interact with pre-existing neural
structures to produce new synapses and neural structure. However,
substantial data as well as an evolutionary perspective indicate that
multiple information-capture systems exist: some are constructivist,
some are selectionist, and some may be tightly constrained.
Universal Grammar: Hypothesis space or grammar selection procedures? Is UG affected by Critical Periods?
Authors: Martohardjono Gita , Epstein Samuel David , Flynn Suzanne
Published: July 2002

Universal Grammar (UG) can be interpreted as a constraint on
the form of possible grammars (hypothesis space) or as a constraint
on acquisition strategies (selection procedures). In this response to
Herschensohn we reiterate the position outlined in Epstein et al.
(1996a, r), that in the evaluation of L2 acquisition as a UG-
constrained process the former (possible grammars/ knowledge
states) is critical, not the latter. Selection procedures, on the
other hand, are important in that they may have a bearing on
development in language acquisition. We raise the possibility that
differences in first and second language acquisition pertaining to
both attainment of the end-state and course of development may
derive from differences in selection procedures. We further suggest
that for these reasons age effects in the attainment of nativelike
proficiency must necessarily be separated from UG effects.
Linear correlates in the speech signal: Consequences of the specific use of an acoustic tube?
Authors: Carré René
Published: July 2002

The debate on the origin of the locus equation is circular. In
this commentary the locus equation is obtained by way of a theoretical
model based on acoustics without recourse to articulatory knowledge or
perceptual constraints. The proposed model is driven by criteria of
minimum energy and maximum simplicity.
Flexible features, connectionism, and computational learning theory
Authors: Dorffner Georg
Published: July 2002

This commentary is an elaboration on Schyns, Goldstone &
Thibaut's proposal for flexible features in categorization in the
light of three areas not explicitly discussed by the authors:
connectionist models of categorization, computational learning theory,
and constructivist theories of the mind. In general, the authors'
proposal is strongly supported, paving the way for model extensions
and for interesting novel cognitive research. Nor is the authors'
proposal incompatible with theories positing some fixed set of
features.
Integrating cues in speech perception
Authors: Massaro Dominic W.
Published: July 2002

Sussman et al. describe an ecological property of the speech
signal that is putatively functional in perception. An important
issue, however, is whether their putative cue is an emerging feature
or whether the second formant (F2) onset and the F2 vowel actually
provide independent cues to perceptual categorization. Regardless of
the outcome of this issue, an important goal of speech research is to
understand how multiple cues are evaluated and integrated to achieve
categorization.
Articulatory evidence for syllabic structure
Authors: Munhall K. G. , Jones J. A.
Published: July 2002

Because the evolution of speech production is beyond our
expertise (and perhaps beyond everyone's expertise) we
restrict our comments to areas in which data actually exist. We
provide articulatory evidence consistent with the claims made
about syllable structure in adult speech and infant babbling, but
we also voice some disagreement about speech errors and the
typing data.
Locus equations and pattern recognition
Authors: Nearey Terrance M.
Published: July 2002

Although the relations between second formant (F2) onset and
F2 vowel are extremely regular and contain important information about
place of articulation of the voiced stops, they are not sufficient for
its identification. Using quadratic discriminant analysis of a new
data set, it is shown that F3 onset and F3 vowel can also contribute
substantial additional information to help identify the
consonants.
Significance tests: Necessary but not sufficient
Authors: Tassinary Louis G.
Published: July 2002

Chow (1996) offers a reconceptualization of statistical
significance that is reasoned and comprehensive. Despite a somewhat
rough presentation, his arguments are compelling and deserve to be
taken seriously by the scientific community. It is argued that his
characterization of literal replication, types of research, effect
size, and experimental control are in need of revision.
Colour word usage within languages follows the Berlin and Kay ordering
Authors: McManus I. C.
Published: July 2002

Colour word usage within languages follows the same ordering as that proposed by Berlin and Kay between languages. This provides additional validation and support for Berlin and Kay's schema.
And what about the Chinese?
Authors: Behrens Heike , Tomasello Michael
Published: July 2002

We discuss other recent studies on the acquisition of the German plural that do not support the dual-mechanism model. The attested overgeneralizations are not by default only, nor completely random, but predictable from subregularities based on the grammatical gender and the phonology of the noun. In addition, the dual-mechanism model creates a number of problems for acquisition (theory) rather than solving existing ones.
Volitional control in the learning of artificial grammars
Authors: Bibby Peter A. , Underwood Geoffrey
Published: July 2002

Dienes & Perner argue that volitional control in artificial
grammar learning is best understood in terms of the distinction between
implicit and explicit knowledge representations. We maintain that
direct, explicit access to knowledge organised in a hierarchy of
implicitness/explicitness is neither necessary nor sufficient to explain
volitional control. People can invoke volitional control when their
knowledge is implicit, as in the case of artificial grammar learning,
and they can invoke volitional control when any part of their knowledge
representation is implicit, as can be seen by examining “feeling
of knowing” phenomena.
Implicit and explicit representations of visual space
Authors: Bridgeman Bruce
Published: July 2002

The visual system captures a unique contrast between implicit
and explicit representation where the same event (location of a visible
object) is coded in both ways in parallel. A method of differentiating
the two representations is described using an illusion that affects only
the explicit representation. Consistent with predictions, implicit
information is available only from targets presently visible, but,
surprisingly, a two-alternative decision does not disturb the
implicit representation.
How women compete
Authors: Cashdan Elizabeth
Published: July 2002

Men are more physically aggressive and more risk-prone than
women, but are not necessarily more competitive. New data show the
gender difference in competitiveness to be one of kind rather than
degree, with women and men competing in different ways and, to
some extent, over different objectives, but not differing in overall
strength of competitive feeling.
Consideration of the drive properties of the mammillary bodies solves the “fornix problem”
Authors: Krieckhaus E. E.
Published: July 2002

Fornix problem: Why do lesions of the fornix, which connects
the hippocampus (HF) to the medial mammillary nucleus (MMN), often
cause no deficits in tasks severely affected by lesions of HF or MMN?
Solution: The direct HF feedback to antero ventral (AV) thalamus (MMN
⇒ AV [hArr ] HF), which is blocked by MMN lesions but not fornix
lesions, is sufficient for nonscene-relevant consolidation.
Individuals are abstractions
Authors: Hurford James R.
Published: July 2002

Barsalou's move to a perceptual basis for cognition is
welcome. His scheme contrasts with classical logical schemes in many
ways, including its implications for the status of individuals. Barsalou
deals mainly with perceived individuals, omitting discussion of cognized
individuals. It is argued that the individuality of cognized individuals
is an abstraction, which conforms in its manner of formation to other
cognitive abstractions which Barsalou discusses, such as truth and
disjunction.
How does implicit and explicit knowledge fit in the consciousness of action?
Authors: Georgieff Nicolas , Rossetti Yves
Published: July 2002

Dienes & Perner's (D&P's) target articles
proposes an analysis of explicit knowledge based on a progressive
transformation of implicit into explicit products, applying this
gradient to different aspects of knowledge that can be represented.
The goal is to integrate a philosophical concept of knowledge with
relevant psychophysical and neuropsychological data. D&P seem to
fill an impressive portion of the gap between these two areas. We focus
on two examples where a full synthesis of theoretical and empirical data
seems difficult to establish and would require further refinement of the
model: action representation and the closely related consciousness of
action, which is in turn related to self-consciousness.
Normal, pseudonormal, and color-blind vision: Cases of justified phenomenal belief
Authors: Nida-Rümelin Martine
Published: July 2002

Palmer's “isomorphism constraint” may be interpreted as a claim about (1) what can be known with certainty, or (2) what can be detected, or (3) what beliefs can be justified on the basis of a certain kind of scientific knowledge. I argue that his claim is valid if interpreted in one of the first two ways, but invalid if interpreted in the third way.
External symbols are a better bet than perceptual symbols
Authors: Wells A. J.
Published: July 2002

Barsalou's theory rightly emphasizes the perceptual basis
of cognition. However, the perceptual symbols that he proposes seem ill
suited to carry the representational burden entailed by the architecture
in which they function, given that Barsalou accepts the requirement for
productivity. A more radical proposal is needed in which symbols are
largely external to the cognizer and linked to internal states via
perception.
Attentive selection penetrates (almost) the entire visual system
Authors: Tsotsos John K.
Published: July 2002

Pylyshyn claims that if a system is cognitively penetrable,
its function depends in a semantically coherent way to the
organism's goals and beliefs. He rejects evidence of attentional
modulation observed in neurons within the visual system, claiming
that any modulation seen is not logically related to goals and
behavior. I present some of this evidence and claim that it is
connected in exactly the way Pylyshyn requires and thus it refutes
his main thesis.
Discovering traces of the past: Studies of bilingualism among school pupils in Finland
and in Sweden. Olli Kuure. Oulu: Oulu University Press, 1997. Pp. 182.
Authors: Cromdal Jakob
Published: July 2002

This is a courageous book. Published as the author's doctoral thesis, this work strives
retrospectively to “determine the significance of age in the acquisition of a second
language” (p. 26). It has explicit interdisciplinary ambitions to integrate concepts and
practices from various disciplines in which bilingual development is studied: notably,
sociocultural theory, developmental psychology, psycholinguistics, text linguistics, and
pragmatics. These multifaceted theoretical aims are anchored in an equally broad empirical
ground, drawing on various types of data. Not surprisingly, the result is a theoretically intriguing,
yet methodologically puzzling, approach to the study of bilingualism and second language
acquisition.
Coefficient rings for beta function classes of Markov chains
Authors: TUNCEL SELIM
Published: July 2002

To each function we associate a period, a polytope, a group $\Gamma$, a subgroup $\Delta \subset\Gamma$ and a coset of $\Gamma/\Delta$, and show these objects to be universal for the class of Markov chains with that beta function. One consequence is that polynomial matrices employed in coding problems of Markov chains can be chosen canonically.
The strong sweeping out property for convolution powers
Authors: LOSERT V.
Published: July 2002

Pointwise convergence a.e. of \mu^k f has been studied by Bellow, Jones and Rosenblatt. We answer two of their questions: the strong sweeping out property holds (in this case) iff the measure \mu has unbounded angular ratio and the stability is equivalent to the bounded angular ratio.
Discontinuities of the pressure for piecewise monotonic interval maps
Authors: RAITH PETER
Published: July 2002

For a piecewise monotonic map T:X\to{\Bbb R}, where X is a finite union of closed intervals, define R(T)= \bigcap_{n=0}^{\infty}\overline{T^{-n}X}. The influence of small perturbations of T on the dynamical system (R(T),T) is investigated. If P is a finite and T-invariant subset of R(T), and if f_0:P\to{\Bbb R} is a non-negative continuous function, then it is proved that the infimum of the topological pressure p(R(T),T,f) over all non-negative continuous functions f:X\to{\Bbb R} with f|_P=f_0 equals the maximum of h_{\text{\rm top}}(R(T),T) and p(P,T,f_0). This result is used to obtain stability conditions, which are equivalent to the upper semi-continuity of the topological pressure for every continuous function f:X\to{\Bbb R}. In the case of a continuous piecewise monotonic map T:X\to{\Bbb R} one of these stability conditions is: there exists no endpoint of an interval of monotonicity of T which is periodic and contained in the interior of X. Furthermore, these results are applied to monotonic mod one transformations, another special case of piecewise monotonic maps.
Periodic orbits and dynamical spectra (Survey)
Authors: BALADI VIVIANE
Published: July 2002

Basic results in the rigorous theory of weighted dynamical zeta functions or dynamically defined generalized Fredholm determinants are presented. Analytic properties of the zeta functions or determinants are related to statistical properties of the dynamics via spectral properties of dynamical transfer operators, acting on Banach spaces of observables.
Zero-dimensional singular continuous spectrum for smooth differential equations on the torus
Authors: HOF A. , KNILL O.
Published: July 2002

We study spectral properties of the flow $\dot x =1/F(x,y)$, $\dot y = 1/\lambda F(x,y)$ on the 2-torus. We show that, in general, the speed of approximation in cyclic approximation gives an upper bound on the Hausdorff dimension of the supports of spectral measures. We use this to prove that for generic pairs $(F,\lambda)$ the spectrum of the flow on the torus is singular continuous with all spectral measures supported on sets of zero Hausdorff dimension.
Rick Halpern and Jonathan Morris, eds., American Exceptionalism? U.S. Working Class Formation in an International Context. New York: St. Martin's Press, 1997. v + 325 pp. $69.95 cloth.
Authors: Davis Colin J.
Published: July 2002

The concept of American exceptionalism has been with us for a long time.
The abundance of books and articles on the subject represents a vigorous cottage
industry. This collection of essays is a welcome addition to the historiography
but, as with its forbears, the issue remains a tricky if not a treacherous
animal to grasp. As Halpern and Morris point out in their introductory chapter,
“The Persistence of Exceptionalism,” the concept is a “corpse
that continually springs to life” (1). These essays “spring to
life” from the celebrated annual Commonwealth Conference at the University
of London.
The Wilson government and the Davies peace mission to North Vietnam, July 1965
Authors: YOUNG JOHN W.
Published: July 2002

The British Labour government under Harold Wilson was involved in several attempts to negotiate an early end to the Vietnam War. Such efforts helped to satisfy critics of the war on the Labour left and in the Commonwealth, to neutralize US pressure to join in the conflict and to emphasize Britain's importance on the world stage. The Davies mission, in which a left-leaning junior minister was sent to Hanoi, was Wilson's most unusual peace bid which ended as a much-criticized fiasco. This story helps to illuminate Wilson's approach to foreign policy-making, the difficulty of pursuing talks without normal diplomatic relations and the obstacles preventing a Vietnam settlement in 1965. The reluctance of both Washington and Hanoi, as well as flaws in the mission's execution, condemned it to failure.
A Virtual Headstick for People with Spinal Cord Injuries
Authors: Chen Shoupu , Rahman Tariq , Foulds Richard , Heredia Edwin , Harwin William
Published: July 2002

This paper presents a virtual headstick system as an alternative to the conventional passive headstick for persons with limited upper extremity function. The system is composed of a pair of kinematically dissimilar master-slave robots with the master robot being operated by the user's head. At the remote site, the end-effector of the slave robot moves as if it were at the tip of an imaginary headstick attached to the user's head.
A unique feature of this system is that through force-reflection, the virtual headstick provides the user with proprioceptive information as in a conventional headstick, but with an augmentation of workspace volume and additional mechanical power. This paper describes the test-bed development, system identification, bilateral control implementation, and system performance evaluation.
Wall-following by an Autonomously Guided Vehicle (AGV) Using a New
Fuzzy-I (Integration) Controller
Authors: Meng Qing-hao , Liu Da-wei , Zhang Ming-lu , Sun Yi-cai
Published: July 2002

In this paper, the wall-following problem of an AGV is characterized by keeping a constant distance from a wall. Four Polaroid ultrasonic range sensors (sonar) are used to obtain information of the distance between the AGV and the wall. Four sonars are divided into two groups being placed at the front and back end on the right side of the AGV, respectively. A digital filter is used to get rid of disturbance and wrong readings. The former results mainly from the door and the latter from the specular reflection and accidental scattering. To obtain good dynamic and steady performances, a new compound fuzzy-I control algorithm is presented. Our methods have been verified by following a 15-meter-long wall with one door by using our TIT-1 AGV (TIT: Tianjin Institute of Technology). The results show a good performance with an error of ±2 cm from the desired distance to the wall.
A configuration space approach to collision avoidance of a two-robot system
Authors: Lee S.W. , Lee B.H. , Lee K.D.
Published: July 2002

This paper suggests an efficient approach to collision avoidance of a practical
two-robot system. The approach is based on the C-space of one robot, and we consider only two and three dimensional C-space in which nearly all industrial manipulators can be reasonably represented for collision avoidance problems. The C-space of one robot
is discretized with the concentric circles or spheres centered at the goal configuration. We then introduce the concept of free arc which is a set of the candidate configuration points on the concentric circle or sphere at each sampling time to avoid collisions. It is represented simply with respect to the coordinate frame attached to the goal configuration. The free arc is used as a tool for collision avoidance of a two-robot system and sub-optimality can be considered in determining a collision-free path. The main contribution of this paper is that it provides a method to construct C-obstacles in a time-varying environment more efficiently than the existing methods (e.g. slice projection method1) by restricting the search space at the expense of sacrificing completeness. Thus, it enables us to implement a practical collision avoidance algorithm for a two-robot system with decreased computational cost. Simulation results for two 2-d.o.f. manipulators and two PUMA robots are presented to show the efficacy of the proposed method.
Uncertainty configurations of parallel manipulators
Authors: Zhao Xinhua , Peng Shangxian
Published: July 2002

This paper presents a new method of analyzing and calculating the uncertainty configurations of parallel manipulators. The main feature of the method that makes it attractive with respect to the methods available in the literature, is its ability to
obtain simplified uncertainty configuration equations. It's very useful in real-time
control. The application of the proposed method is illustrated in detail by two examples.