456 research outputs found
CORRECTION OF TRANSIENT SOLID-EMBEDDED THERMOCOUPLE DATA WITH APPLICATION TO INVERSE HEAT CONDUCTION
The current research investigates the use of solid-embedded thermocouples for determining accurate transient temperature measurements within a solid medium, with emphasis on measurements intended for use in inverse heat conduction problems. Metal casting experiments have been conducted to collect internal mold temperatures to be used, through inverse conduction methods, to estimate the heat exchange between a casting and mold. Inverse conduction methods require accurate temperature measurements for valid boundary estimates. Therefore, various sources of thermocouple measurement uncertainty are examined and some suggestions for uncertainty reduction are presented. Thermocouple installation induced bias uncertainties in experimental temperature data are dynamically corrected through the development and implementation of an embedded thermocouple correction (ETC) transfer function. Comparisons of experimental data to dynamically adjusted data, as well as the inverse conduction estimates for heat flux from each data set, are presented and discussed
Minority game with arbitrary cutoffs
We study a model of a competing population of N adaptive agents, with similar
capabilities, repeatedly deciding whether to attend a bar with an arbitrary
cutoff L. Decisions are based upon past outcomes. The agents are only told
whether the actual attendance is above or below L. For L-> N/2, the game
reproduces the main features of Challet and Zhang's minority game. As L is
lowered, however, the mean attendances in different runs tend to divide into
two groups. The corresponding standard deviations for these two groups are very
different. This grouping effect results from the dynamical feedback governing
the game's time-evolution, and is not reproduced if the agents are fed a random
history.Comment: 4 pages (Revtex) + 6 separate pdf figure
Generalized strategies in the Minority Game
We show analytically how the fluctuations (i.e. standard deviation) in the
Minority Game (MG) can be made to decrease below the random coin-toss limit if
the agents use more general behavioral strategies. This suppression of the
standard deviation results from a cancellation between the actions of a crowd,
in which agents act collectively and make the same decision, and an anticrowd
in which agents act collectively by making the opposite decision to the crowd.Comment: Revised manuscript: a few minor typos corrected. Results unaffecte
Crowd-anticrowd theory of the Minority Game
The Minority Game is a simple yet highly non-trivial agent-based model for a
complex adaptive system. Despite its importance, a quantitative explanation of
the game's fluctuations which applies over the entire parameter range of
interest has so far been lacking. We provide such a quantitative description
based on the interplay between crowds of like-minded agents and their
anti-correlated partners (anticrowds).Comment: Shortened version of cond-mat/0003486. Submitted for publicatio
Volatility and Agent Adaptability in a Self-Organizing Market
We present results for the so-called `bar-attendance' model of market
behavior: adaptive agents, each possessing prediction rules chosen
randomly from a pool, attempt to attend a bar whose cut-off is . The global
attendance time-series has a mean near, but not equal to, . The variance, or
`volatility', can show a minimum with increasing adaptability of the individual
agents.Comment: 8 pages, 3 figs. [email protected], [email protected]
Anatomy of extreme events in a complex adaptive system
We provide an analytic, microscopic analysis of extreme events in an adaptive
population comprising competing agents (e.g. species, cells, traders,
data-packets). Such large changes tend to dictate the long-term dynamical
behaviour of many real-world systems in both the natural and social sciences.
Our results reveal a taxonomy of extreme events, and provide a microscopic
understanding as to their build-up and likely duration.Comment: 8 pages, 4 figures. Now with Postscript figure
Molecular phylogeny of telenomine egg parasitoids (Hymenoptera: Platygastridae s.l.: Telenominae): evolution of host shifts and implications for classification
Parasitoid wasps of the subfamily Telenominae (Hymenoptera: Platygastroidea, Platygastridae) develop as immatures within the eggs of other insects (Lepidoptera, Hemiptera, Diptera and Neuroptera). Rearing records indicate that individual species are restricted to attack hosts within only one of these four main groups. We conducted a phylogenetic analysis of the group using sequence data from multiple genes (18S, 28S, COI, EF-1α) to assess the pattern of shifts among host groups and to test the monophyly of and relationships among genera and species-groups. Telenominae sensu Masner—that is, including only the nominate tribe Telenomini—is not monophyletic. Representatives of the Psix group of genera (Psix Kozlov & Lê and Paratelenomus Dodd) form a monophyletic group that is sister to Gryon Haliday (Scelioninae: Gryonini) and are excluded from the subfamily. The remaining telenomines are monophyletic. The genus Phanuromyia Dodd and the crassiclava group of Telenomus Haliday, both recorded as parasitoids of planthopper eggs (Hemiptera: Auchenorrhyncha, Fulgoroidea), form a monophyletic group that is sister to all other telenomines exclusive of the Psix group. Twenty-nine species of the crassiclava and aradi groups of Telenomus are transferred to Phanuromyia as new combinations. Basal elements of the remaining species are all in groups reared from the eggs of true bugs (Heteroptera), primarily the stink bugs (Pentatomoidea) and seed bugs (Lygaeoidea). A shift to parasitism of lepidopteran eggs evolved within a single clade, occurring either one or two times. From this clade a small group of species, the Telenomus tabanivorus group, subsequently shifted to parasitism of egg masses of true flies (Tabanidae and Stratiomyiidae). Aholcus Kieffer and Platytelenomus Dodd both belong to the clade of lepidopteran parasitoids and are considered as junior synonyms of Telenomus (new synonymy for Aholcus). The monophyletic status of the two core genera, Telenomus and Trissolcus could not be resolved using these data. The phylogenetic pattern of host shifts suggests comparisons among taxa that may be fruitful in elucidating mechanisms by which parasitoids locate their hosts, the proximate factors that determine the host range, and the changes in these factors that influence host changes.Charuwat Taekul, Alejandro A. Valerio, Andrew D. Austin, Hans Klompen and Norman F. Johnso
Continuous time dynamics of the Thermal Minority Game
We study the continuous time dynamics of the Thermal Minority Game. We find
that the dynamical equations of the model reduce to a set of stochastic
differential equations for an interacting disordered system with non-trivial
random diffusion. This is the simplest microscopic description which accounts
for all the features of the system. Within this framework, we study the phase
structure of the model and find that its macroscopic properties strongly depend
on the initial conditions.Comment: 4 pages, 4 figure
Theory of Phase Transition in the Evolutionary Minority Game
We discover the mechanism for the transition from self-segregation (into
opposing groups) to clustering (towards cautious behaviors) in the evolutionary
minority game (EMG). The mechanism is illustrated with a statistical mechanics
analysis of a simplified EMG involving three groups of agents: two groups of
opposing agents and one group of cautious agents. Two key factors affect the
population distribution of the agents. One is the market impact (the
self-interaction), which has been identified previously. The other is the
market inefficiency due to the short-time imbalance in the number of agents
using opposite strategies. Large market impact favors "extreme" players who
choose fixed strategies, while large market inefficiency favors cautious
players. The phase transition depends on the number of agents (), the
reward-to-fine ratio (), as well as the wealth reduction threshold () for
switching strategy. When the rate for switching strategy is large, there is
strong clustering of cautious agents. On the other hand, when is small, the
market impact becomes large, and the extreme behavior is favored.Comment: 5 pages and 3 figure
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