190 research outputs found
Van der Waals density-functional theory study for bulk solids with BCC, FCC, and diamond structures
Proper inclusion of van der Waals (vdW) interactions in theoretical
simulations based on standard density functional theory (DFT) is crucial to
describe the physics and chemistry of systems such as organic and layered
materials. Many encouraging approaches have been proposed to combine vdW
interactions with standard approximate DFT calculations. Despite many vdW
studies, there is no consensus on the reliability of vdW methods. To help
further development of vdW methods, we have assessed various vdW functionals
through the calculation of structural prop- erties at equilibrium, such as
lattice constants, bulk moduli, and cohesive energies, for bulk solids,
including alkali, alkali-earth, and transition metals, with BCC, FCC, and
diamond structures as the ground state structure. These results provide
important information for the vdW-related materials research, which is
essential for designing and optimizing materials systems for desired physical
and chemical properties.Comment: 10 pages, 6 Figures, 3 Table
Exploring Customer Preferences on Mobile Services
Designing mobile services is fundamentally different than designing online services. Not only are there differences in underlying technologies, but also in the way people use services. If these differences are not taken into account, mobile services are likely to fail. If mobile services do not deliver what people want, these services will fail no matter how excellent the underlying technology is. The user interface design that is commonly used in mobile services is based on multi-layered approach, which is not very user friendly. So a well designed single layered user interface will be more user friendly than the conventional one and it will be having edge over others. However, it is quite difficult to provide a single layered user interface in a small screen. This study aims at examining how user interface design attributes of mobile services affect customer preferences. In order to explore customer preferences to each design attribute, we measure customer’s WTP (Willingness To Pay) toward different interface designs
Self-calibrating random access logarithmic pixel for on chip camera
CMOS active pixel sensors (APS) have shown competitive performance with charge-coupled device (CCD) and offer many advantages in cost, system power reduction and on-chip integration of VLSI electronics. Among CMOS image sensors, sensors with logarithmic pixels are particularly applicable for outdoor environment where the light intensity varies over a wide range. They are also randomly accessible in both time and space. A major drawback comes from process variations during fabrication. This gives rise to a considerable fixed pattern noise (FPN) which deteriorates the image quality. In this thesis, a technique that greatly reduces FPN using on-chip calibration is introduced. An image sensor that consists of 64x64 active pixels has been designed, fabricated and tested. Pixel pitch is 18um x 19.2um? and is fabricated in a 0.5-um? CMOS process. The proposed pixel circuit considerably reduces the FPN as predicted in theoretical analysis. The measured FPN value is 2.29% of output voltage swing and column-wise FPN is 1.49% of mean output voltage over each column
Learning Symmetrization for Equivariance with Orbit Distance Minimization
We present a general framework for symmetrizing an arbitrary neural-network
architecture and making it equivariant with respect to a given group. We build
upon the proposals of Kim et al. (2023); Kaba et al. (2023) for symmetrization,
and improve them by replacing their conversion of neural features into group
representations, with an optimization whose loss intuitively measures the
distance between group orbits. This change makes our approach applicable to a
broader range of matrix groups, such as the Lorentz group O(1, 3), than these
two proposals. We experimentally show our method's competitiveness on the SO(2)
image classification task, and also its increased generality on the task with
O(1, 3). Our implementation will be made accessible at
https://github.com/tiendatnguyen-vision/Orbit-symmetrize.Comment: 16 pages, 1 figur
GTA: Guided Transfer of Spatial Attention from Object-Centric Representations
Utilizing well-trained representations in transfer learning often results in
superior performance and faster convergence compared to training from scratch.
However, even if such good representations are transferred, a model can easily
overfit the limited training dataset and lose the valuable properties of the
transferred representations. This phenomenon is more severe in ViT due to its
low inductive bias. Through experimental analysis using attention maps in ViT,
we observe that the rich representations deteriorate when trained on a small
dataset. Motivated by this finding, we propose a novel and simple
regularization method for ViT called Guided Transfer of spatial Attention
(GTA). Our proposed method regularizes the self-attention maps between the
source and target models. A target model can fully exploit the knowledge
related to object localization properties through this explicit regularization.
Our experimental results show that the proposed GTA consistently improves the
accuracy across five benchmark datasets especially when the number of training
data is small
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