104,157 research outputs found
Simulating emergent urban form: desakota in China
We propose that the emergent phenomenon know as ?desakota?, the rapidurbanization of densely populated rural populations in the newlydeveloped world, particularly China, can be simulated using agent-basedmodels which combine both local and global features. We argue thatdeskota represents a surprising and unusual form of urbanization wellmatchedto processes of land development that are driven from the bottomup but moderated by the higher-level macro economy. We develop asimple logic which links local household reform to global urban reform,translating these ideas into a model structure which reflects these twoscales. Our model first determines the rate of growth of different spatialaggregates using linear statistical analysis. It then allocates this growth tothe local level using developer agents who determine the transformation ormutation of rural households to urban pursuits based on local land costs,accessibilities, and growth management practices. The model is applied todesakota development in the Suzhou region between 1990 and 2000. Weshow how the global rates of change predicted at the township level in theWuxian City region surrounding Suzhou are tempered by localtransformations of rural to urban land uses which we predict using cellularautomata rules. The model, which is implemented in the RePast 3software, is validated using a blend of data taken from remote sensing andgovernment statistical sources. It represents an example of generativesocial science that fuses plausible behavior with formalized logics matchedagainst empirical evidence, essential in showing how novel patterns ofurbanization such as desakota emerge
Enhanced spin-orbit torques in MnAl/Ta films with improving chemical ordering
We report the enhancement of spin-orbit torques in MnAl/Ta films with
improving chemical ordering through annealing. The switching current density is
increased due to enhanced saturation magnetization MS and effective anisotropy
field HK after annealing. Both damplinglike effective field HD and fieldlike
effective field HF have been increased in the temperature range of 50 to 300 K.
HD varies inversely with MS in both of the films, while the HF becomes liner
dependent on 1/MS in the annealed film. We infer that the improved chemical
ordering has enhanced the interfacial spin transparency and the transmitting of
the spin current in MnAl layer
Synthetic vision and emotion calculation in intelligent virtual human modeling
The virtual human technique already can provide vivid and believable human behaviour in more and more scenarios. Virtual humans are expected to replace real humans in hazardous situations to undertake tests and feed back valuable information. This paper will introduce a virtual human with a novel collision-based synthetic vision, short-term memory model and a capability to implement the emotion calculation and decision making. The virtual character based on this model can ‘see’ what is in his field of view (FOV) and remember those objects. After that, a group of affective computing equations have been introduced. These equations have been implemented into a proposed emotion calculation process to enlighten emotion for virtual intelligent huma
Energy Centroids of Spin States by Random Two-body Interactions
In this paper we study the behavior of energy centroids (denoted as
) of spin states in the presence of random two-body
interactions, for systems ranging from very simple systems (e.g. single-
shell for very small ) to very complicated systems (e.g., many- shells
with different parities and with isospin degree of freedom). Regularities of
's discussed in terms of the so-called geometric chaoticity (or
quasi-randomness of two-body coefficients of fractional parentage) in earlier
works are found to hold even for very simple systems in which one cannot assume
the geometric chaoticity. It is shown that the inclusion of isospin and parity
does not "break" the regularities of 's.Comment: four figures. to appear in Physical Review
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Emotion-affected decision making in human simulation
Human modelling is an interdisciplinary research field. The topic, emotion-affected decision making, was originally a cognitive psychology issue, but is now recognized as an important research direction for both computer science and biomedical modelling. The main aim of this paper is to attempt to bridge the gap between psychology and bioengineering in emotion-affected decision making. The work is based on Ortony's theory of emotions and bounded rationality theory, and attempts to connect the emotion process with decision making. A computational emotion model is proposed, and the initial framework of this model in virtual human simulation within the platform of VirtoolsTm is presented
Distributed Flow Scheduling in an Unknown Environment
Flow scheduling tends to be one of the oldest and most stubborn problems in
networking. It becomes more crucial in the next generation network, due to fast
changing link states and tremendous cost to explore the global structure. In
such situation, distributed algorithms often dominate. In this paper, we design
a distributed virtual game to solve the flow scheduling problem and then
generalize it to situations of unknown environment, where online learning
schemes are utilized. In the virtual game, we use incentives to stimulate
selfish users to reach a Nash Equilibrium Point which is valid based on the
analysis of the `Price of Anarchy'. In the unknown-environment generalization,
our ultimate goal is the minimization of cost in the long run. In order to
achieve balance between exploration of routing cost and exploitation based on
limited information, we model this problem based on Multi-armed Bandit Scenario
and combined newly proposed DSEE with the virtual game design. Armed with these
powerful tools, we find a totally distributed algorithm to ensure the
logarithmic growing of regret with time, which is optimum in classic
Multi-armed Bandit Problem. Theoretical proof and simulation results both
affirm this claim. To our knowledge, this is the first research to combine
multi-armed bandit with distributed flow scheduling.Comment: 10 pages, 3 figures, conferenc
Correction function in the Lidar equation and the solution techniques for CO2 Lidar date reduction
For lidar systems with long laser pulses the unusual behavior of the near-range signals causes serious difficulties and large errors in reduction. The commonly used lidar equation is no longer applicable since the convolution of the laser pulse with the atmospheric parameter distributions should be taken into account. It is important to give more insight into this problem and find the solution techniques. Starting from the original equation, a general form is suggested for the single scattering lidar equation where a correction function Cr is introduced. The correction Function Cr(R) derived from the original equation indicates the departure from the normal lidar equation. Examples of Cr(R) for a coaxial CO2 lidar system are presented. The Differential Absorption Lidar (DIAL) errors caused by the differences of Cr(R) for H2O measurements are plotted against height
High-quality positrons from a multi-proton bunch driven hollow plasma wakefield accelerator
By means of hollow plasma, multiple proton bunches work well in driving
nonlinear plasma wakefields and accelerate electrons to energy frontier with
preserved beam quality. However, the acceleration of positrons is different
because the accelerating structure is strongly charge dependent. There is a
discrepancy between keeping a small normalized emittance and a small energy
spread. This results from the conflict that the plasma electrons used to
provide focusing to the multiple proton bunches dilute the positron bunch. By
loading an extra electron bunch to repel the plasma electrons and meanwhile
reducing the plasma density slightly to shift the accelerating phase with a
conducive slope to the positron bunch, the positron bunch can be accelerate to
400 GeV (40% of the driver energy) with an energy spread as low as 1% and well
preserved normalized emittance. The successful generation of high quality and
high energy positrons paves the way to the future energy frontier lepton
colliders.Comment: 14 pages, 5 figure
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