206 research outputs found
Learning transferrable parameters for long-tailed sequential user behavior modeling
National Research Foundation (NRF) Singapore under its AI Singapore Programm
String Method for the Study of Rare Events
We present a new and efficient method for computing the transition pathways,
free energy barriers, and transition rates in complex systems with relatively
smooth energy landscapes. The method proceeds by evolving strings, i.e. smooth
curves with intrinsic parametrization whose dynamics takes them to the most
probable transition path between two metastable regions in the configuration
space. Free energy barriers and transition rates can then be determined by
standard umbrella sampling technique around the string. Applications to
Lennard-Jones cluster rearrangement and thermally induced switching of a
magnetic film are presented.Comment: 4 pages, 4 figure
A Particle-based Multiscale Solver for Compressible Liquid-Vapor Flow
To describe complex flow systems accurately, it is in many cases important to
account for the properties of fluid flows on a microscopic scale. In this work,
we focus on the description of liquid-vapor flow with a sharp interface between
the phases. The local phase dynamics at the interface can be interpreted as a
Riemann problem for which we develop a multiscale solver in the spirit of the
heterogeneous multiscale method, using a particle-based microscale model to
augment the macroscopic two-phase flow system. The application of a microscale
model makes it possible to use the intrinsic properties of the fluid at the
microscale, instead of formulating (ad-hoc) constitutive relations
Efficient Behavior-consistent Calibration for Multi-agent Market Simulation
Order-driven market simulation mimics the trader behaviors to generate order
streams to support interactive studies of financial strategies. In market
simulator, the multi-agent approach is commonly adopted due to its
explainability. Existing multi-agent systems employ heuristic search to
generate order streams, which is inefficient for large-scale simulation.
Furthermore, the search-based behavior calibration often leads to inconsistent
trader actions under the same general market condition, making the simulation
results unstable and difficult to interpret.
We propose CaliSim, the first search-free calibration approach multi-agent
market simulator which achieves large-scale efficiency and behavior
consistency. CaliSim uses meta-learning and devises a surrogate trading system
with a consistency loss function for the reproducibility of order stream and
trader behaviors. Extensive experiments in the market replay and case studies
show that CaliSim achieves state-of-the-art in terms of order stream
reproduction with consistent trader behavior and can capture patterns of real
markets
Regrowth-free AlGaInAs MQW polarization controller integrated with sidewall grating DFB laser
We report an AlGaInAs multiple quantum well integrated source of polarization
controlled light consisting of a polarization mode converter PMC, differential
phase shifter(DPS), and a side wall grating distributed-feedback DFB laser. We
demonstrate an asymmetrical stepped-height ridge waveguide PMC to realize TE to
TM polarization conversion and a symmetrical straight waveguide DPS to enable
polarization rotation from approximately counterclockwise circular polarization
to linear polarization. Based on the identical epitaxial layer scheme, all of
the PMC, DPS, and DFB laser can be integrated monolithically using only a
single step of metalorganic vapor phase epitaxy and two steps of III V material
dry etching. For the DFB-PMC device, a high TE to TM polarization conversion
efficiency 98% over a wide range of DFB injection currents is reported at 1555
nm wavelength. For the DFB-PMC-DPS device, a 60 degree rotation of the Stokes
vector was obtained on the Poincar\'e sphere with a range of bias voltage from
0 V to -4.0 V at IDFB is 170 mA.Comment: arXiv admin note: text overlap with arXiv:2210.1051
Stepped-height ridge waveguide MQW polarization mode converter monolithically integrated with sidewall grating DFB laser
We report the first demonstration of a 1555 nm stepped-height ridge waveguide
polarization mode converter monolithically integrated with a side wall grating
distributed-feedback (DFB) laser using the identical epitaxial layer scheme.
The device shows stable single longitudinal mode (SLM) operation with the
output light converted from TE to TM polarization with an efficiency of >94%
over a wide range of DFB injection currents (IDFB) from 140 mA to 190 mA. The
highest TM mode purity of 98.2% was obtained at IDFB=180 mA. A particular
advantage of this device is that only a single step of metalorganic vapor-phase
epitaxy and two steps of III-V material dry etching are required for the whole
integrated device fabrication, significantly reducing complexity and cost
Visible emission and energy transfer in Tb<sup>3+</sup>/Dy<sup>3+</sup> co-doped phosphate glasses
In this work, we systematically study the spectroscopic properties of Tb3+/Dy3+ co-doped phosphate glasses in the visible spectral region and explore the sensitization role of Dy3+ in the enhancement of visible fluorescence of Tb3+ ions. Judd-Ofelt parameters Ω2 and Ω4/Ω6 of the phosphate glass as host for Tb3+ are calculated as 21.60 × 10-20 cm2 and 0.73, respectively, based on the measured spectral absorption. Multiple energy transfer (ET) routes from Dy3+ to Tb3+ and their efficiencies are characterized, and the enhanced fluorescence properties of Tb3+ are investigated, including the emission spectral strength and the spontaneous emission lifetime as functions of Dy3+ doping concentration. The efficient nonradiative ET processes between Dy3+ and Tb3+ allow a moderate concentration level of Tb3+ to achieve favorably stronger spectral absorption at blue and ultraviolet wavelengths. Tb3+/Dy3+ co-doped phosphate glass shows promising potential for phosphors and lasing operation at visible wavelengths.</p
FoodFab: creating food perception illusions using food 3D printing
Food 3D printing enables the creation of customized food structures based on a person’s individual needs. In this paper, we explore the use of food 3D printing to create perceptual illusions for controlling the level of perceived satiety given a defined amount of calories. We present FoodFab, a system that allows users to control their food intake through modifying a food’s internal structure via two 3D printing parameters: infill pattern and infill density. In two experiments with a total of 30 participants, we studied the effect of these parameters on users’ chewing time that is known to affect people’s feeling of satiety. Our results show that we can indeed modify the chewing time by varying infill pattern and density, and thus control perceived satiety. Based on the results, we propose two computational models and integrate them into a user interface that simplifies the creation of personalized food structures
Scattering Field Enhanced Biosensing Based on Sub-wavelength Split-ring Plasmonic Cavity With High Q-factor
Plasmonic structures are widely used in modern biosensor design. various plasmonic resonant cavities could efficiently achieve a high Q-factor, improving the local field intensity to enhance photoluminescence or SERS (Surface-Enhanced Raman Scattering) of small molecules. Also, the combination between virus-like particles and plasmonic structures could significantly influence the scattering spectrum and field, which is utilized as a method for biological particle detection. In this paper, we designed one kind of gold plasmonic cavity with the shape of a split-ring. An edge gap and a bonus center bulge are introduced in the split-ring structure. Our simulation is based on Finite Difference Time Domain (FDTD) method. Polarization Indirect Microscopic Imaging (PIMI) technique is used here to detect far-field mode distribution under the resonant wavelength. The simulation results demonstrate resonant peaks in the visible spectrum at about 600 nm with a Q-factor reaches to 74. Localized hot spots are generated by an edge dipole mode and a cavity hexapole mode at resonant wavelength, which is according to dark points in the PIMI sinδ image. Also, the split-ring cavity shows a sensitivity when combined with biological particles. The scattering distribution is evidently changed as a result of energy exchange between particles and split-ring cavity, indicating a promising possibility for biosensing
Stepped-height ridge waveguide MQW polarization mode converter monolithically integrated with sidewall grating DFB laser
We report the first demonstration of a 1555 nm stepped-height ridge waveguide polarization mode converter monolithically integrated with a side wall grating distributed-feedback (DFB) laser using the identical epitaxial layer scheme. The device shows stable single longitudinal mode (SLM) operation with the output light converted from TE to TM polarization with an efficiency of >94% over a wide range of DFB injection currents (IDFB) from 140 mA to 190 mA. The highest TM mode purity of 98.2% was obtained at IDFB=180 mA. A particular advantage of this device is that only a single step of metalorganic vapor-phase epitaxy and two steps of III-V material dry etching are required for the whole integrated device fabrication, significantly reducing complexity and cost
- …