107 research outputs found
Probabilistic Generative Transformer Language models for Generative Design of Molecules
Self-supervised neural language models have recently found wide applications
in generative design of organic molecules and protein sequences as well as
representation learning for downstream structure classification and functional
prediction. However, most of the existing deep learning models for molecule
design usually require a big dataset and have a black-box architecture, which
makes it difficult to interpret their design logic. Here we propose Generative
Molecular Transformer (GMTransformer), a probabilistic neural network model for
generative design of molecules. Our model is built on the blank filling
language model originally developed for text processing, which has demonstrated
unique advantages in learning the "molecules grammars" with high-quality
generation, interpretability, and data efficiency. Benchmarked on the MOSES
datasets, our models achieve high novelty and Scaf compared to other baselines.
The probabilistic generation steps have the potential in tinkering molecule
design due to their capability of recommending how to modify existing molecules
with explanation, guided by the learned implicit molecule chemistry. The source
code and datasets can be accessed freely at
https://github.com/usccolumbia/GMTransformerComment: 13 page
A New Switched State Jump Observer for Traffic Density Estimation in Expressways Based on Hybrid-Dynamic-Traffic-Network-Model
When faced with problems such as traffic state estimation, state prediction, and congestion identification for the expressway network, a novel switched observer design strategy with jump states is required to reconstruct the traffic scene more realistically. In this study, the expressway network is firstly modeled as the special discrete switched system, which is called the piecewise affine system model, a partition of state subspace is introduced, and the convex polytopes are utilized to describe the combination modes of cells. Secondly, based on the hybrid dynamic traffic network model, the corresponding switched observer (including state jumps) is designed. Furthermore, by applying multiple Lyapunov functions and S-procedure theory, the observer design problem can be converted into the existence issue of the solutions to the linear matrix inequality. As a result, a set of gain matrices can be obtained. The estimated states start to jump when the mode changes occur, and the updated value of the estimated state mainly depends on the estimated and the measured values at the previous time. Lastly, the designed state jump observer is applied to the Beijing Jingkai expressway, and the superiority and the feasibility are demonstrated in the application results
Electron dynamics in topological insulator based semiconductor-metal interfaces (topological p-n interface based on Bi2Se3 class)
Single-Dirac-cone topological insulators (TI) are the first experimentally
discovered class of three dimensional topologically ordered electronic systems,
and feature robust, massless spin-helical conducting surface states that appear
at any interface between a topological insulator and normal matter that lacks
the topological insulator ordering. This topologically defined surface
environment has been theoretically identified as a promising platform for
observing a wide range of new physical phenomena, and possesses ideal
properties for advanced electronics such as spin-polarized conductivity and
suppressed scattering. A key missing step in enabling these applications is to
understand how topologically ordered electrons respond to the interfaces and
surface structures that constitute a device. Here we explore this question by
using the surface deposition of cathode (Cu/In/Fe) and anode materials (NO)
and control of bulk doping in BiSe from P-type to N-type charge
transport regimes to generate a range of topological insulator interface
scenarios that are fundamental to device development. The interplay of
conventional semiconductor junction physics and three dimensional topological
electronic order is observed to generate novel junction behaviors that go
beyond the doped-insulator paradigm of conventional semiconductor devices and
greatly alter the known spin-orbit interface phenomenon of Rashba splitting.
Our measurements for the first time reveal new classes of diode-like
configurations that can create a gap in the interface electron density near a
topological Dirac point and systematically modify the topological surface state
Dirac velocity, allowing far reaching control of spin-textured helical Dirac
electrons inside the interface and creating advantages for TI superconductors
as a Majorana fermion platform over spin-orbit semiconductors.Comment: 14 pages, 4 Figure
Vertical Stress and Deformation Characteristics of Roadside Backfilling Body in Gob-Side Entry for Thick Coal Seams with Different Pre-Split Angles
Retained gob-side entry (RGE) is a significant improvement for fully-mechanized longwall mining. The environment of surrounding rock directly affects its stability. Roadside backfilling body (RBB), a man-made structure in RGE plays the most important role in successful application of the technology. In the field, however, the vertical deformation of RBB is large during the panel extraction, which leads to malfunction of the RGE. In order to solve the problem, roof pre-split is employed. According to geological conditions as well as the physical modeling of roof behavior and deformation of surrounding rock, the support resistance of RBB is calculated. The environment of surrounding rock, vertical stress and vertical deformation of the RBB in the RGE with different roof pre-split angles are analyzed using FLAC3D software. With the increase of roof pre-split angle, the vertical stresses both in the coal wall and RBB are minimum, and the vertical deformation of RBB also decreases from 110.51 mm to 6.1 mm. Therefore, based on the results of numerical modeling and field observation, roof pre-split angle of 90° is more beneficial to the maintenance of the RGE
Effect of Heat Treatment on the Microstructure and Mechanical Properties of Additive Manufactured Ti-6.5Al-2Zr-1Mo-1V Alloy
Ti-6.5Al-2Zr-1Mo-1V (TA15), widely used in the aerospace industry, is a medium- to high-strength, near-α titanium alloy with high aluminium equivalent value. The TA15 fabricated via laser powder bed fusion (L-PBF) normally presents a typical brittle appearance in as-built status, with high strength and low ductility. In this study, the microstructure and properties of L-PBF TA15 were engineered by various heat treatments below the β-transus temperature (1022 °C). After heat treatment, the original acicular martensite gradually transforms into a typical lamellar α + β dual-phase structure. Withannealing temperature increases, the lamellar α phase thickened with a decreased aspect ratio. Globularisation of the α grain can be noticed when annealing above 800 °C, which leads to a balance between strength and ductility. After heat treatment between 800–900 °C, the desired combination of strength and ductility can be achieved, with elongation of about 12.5% and ultimate tensile strength of about 1100 Mpa
Dynamic Budget Throttling in Repeated Second-Price Auctions
Throttling is one of the most popular budget control methods in today's
online advertising markets. When a budget-constrained advertiser employs
throttling, she can choose whether or not to participate in an auction after
the advertising platform recommends a bid. This paper focuses on the dynamic
budget throttling process in repeated second-price auctions from a theoretical
view. An essential feature of the underlying problem is that the advertiser
does not know the distribution of the highest competing bid upon entering the
market. To model the difficulty of eliminating such uncertainty, we consider
two different information structures. The advertiser could obtain the highest
competing bid in each round with full-information feedback. Meanwhile, with
partial information feedback, the advertiser could only have access to the
highest competing bid in the auctions she participates in. We propose the
OGD-CB algorithm, which involves simultaneous distribution learning and revenue
optimization. In both settings, we demonstrate that this algorithm guarantees
an regret with probability relative to the
fluid adaptive throttling benchmark. By proving a lower bound of
on the minimal regret for even the hindsight optimum, we
establish the near optimality of our algorithm. Finally, we compare the fluid
optimum of throttling to that of pacing, another widely adopted budget control
method. The numerical relationship of these benchmarks sheds new light on the
understanding of different online algorithms for revenue maximization under
budget constraints.Comment: 29 pages, 1 tabl
Simulation study of Ferricyanide/Ferrocyanide concentric annulus thermocell with different electrode spacing and cell direction
Thermogalvanic cell also named as thermocell is a new type of technology converting low-grade thermal energy to electricity. In this study, we establish an one-dimensional model of a Fe(CN)63-/4- concentric annulus thermocell and evaluate the influence of electrode spacing and cell direction on the cell performance. Results indicate the ratio of electrolyte thermal resistance to total thermal resistance plays a crucial role in cell performance while electric resistance has relatively less influence. The power of thermocell rises significantly as the electrode spacing increases, from about 0.75mW in both directions to 1.75 mW in horizontal direction and 2.75 mW in vertical direction. Convection of electrolyte is unfavorable to cell performance and the critical electrode spacing where convection begins to affect heat transfer is predicted to be the optimized spacing. At all values of electrode spacing in this study, thermocell in vertical direction performs better than that of horizontal direction
- …