50 research outputs found
3D Model-free Visual Localization System from Essential Matrix under Local Planar Motion
Visual localization plays a critical role in the functionality of low-cost
autonomous mobile robots. Current state-of-the-art approaches for achieving
accurate visual localization are 3D scene-specific, requiring additional
computational and storage resources to construct a 3D scene model when facing a
new environment. An alternative approach of directly using a database of 2D
images for visual localization offers more flexibility. However, such methods
currently suffer from limited localization accuracy. In this paper, we propose
an accurate and robust multiple checking-based 3D model-free visual
localization system to address the aforementioned issues. To ensure high
accuracy, our focus is on estimating the pose of a query image relative to the
retrieved database images using 2D-2D feature matches. Theoretically, by
incorporating the local planar motion constraint into both the estimation of
the essential matrix and the triangulation stages, we reduce the minimum
required feature matches for absolute pose estimation, thereby enhancing the
robustness of outlier rejection. Additionally, we introduce a multiple-checking
mechanism to ensure the correctness of the solution throughout the solving
process. For validation, qualitative and quantitative experiments are performed
on both simulation and two real-world datasets and the experimental results
demonstrate a significant enhancement in both accuracy and robustness afforded
by the proposed 3D model-free visual localization system
Experimental Investigation on Motions of Immersing Tunnel Element under Irregular Wave Actions
Learning to Identify Top Elo Ratings: A Dueling Bandits Approach
The Elo rating system is widely adopted to evaluate the skills of (chess) game and sports players. Recently it has been also integrated into machine learning algorithms in evaluating the performance of computerised AI agents. However, an accurate estimation of the Elo rating (for the top players) often requires many rounds of competitions, which can be expensive to carry out. In this paper, to improve the sample efficiency of the Elo evaluation (for top players), we propose an efficient online match scheduling algorithm. Specifically, we identify and match the top players through a dueling bandits framework and tailor the bandit algorithm to the gradient-based update of Elo. We show that it reduces the per-step memory and time complexity to constant, compared to the traditional likelihood maximization approaches requiring O(t) time. Our algorithm has a regret guarantee of Õ(√T), sublinear in the number of competition rounds and has been extended to the multidimensional Elo ratings for handling intransitive games. We empirically demonstrate that our method achieves superior convergence speed and time efficiency on a variety of gaming tasks
On the Robustness of ChatGPT: An Adversarial and Out-of-distribution Perspective
ChatGPT is a recent chatbot service released by OpenAI and is receiving
increasing attention over the past few months. While evaluations of various
aspects of ChatGPT have been done, its robustness, i.e., the performance to
unexpected inputs, is still unclear to the public. Robustness is of particular
concern in responsible AI, especially for safety-critical applications. In this
paper, we conduct a thorough evaluation of the robustness of ChatGPT from the
adversarial and out-of-distribution (OOD) perspective. To do so, we employ the
AdvGLUE and ANLI benchmarks to assess adversarial robustness and the Flipkart
review and DDXPlus medical diagnosis datasets for OOD evaluation. We select
several popular foundation models as baselines. Results show that ChatGPT shows
consistent advantages on most adversarial and OOD classification and
translation tasks. However, the absolute performance is far from perfection,
which suggests that adversarial and OOD robustness remains a significant threat
to foundation models. Moreover, ChatGPT shows astounding performance in
understanding dialogue-related texts and we find that it tends to provide
informal suggestions for medical tasks instead of definitive answers. Finally,
we present in-depth discussions of possible research directions.Comment: Technical report; code is at:
https://github.com/microsoft/robustlear
Improved Polymer Crystal Phase Field Model and Numerical Simulation
The existing phase field model of polymer crystallization contains many parameters that lack actual physical meaning. Although the value of these parameters can be adjusted to obtain results consistent with the experiment, it cannot correspond to the experimental conditions. In this paper, a new phase field model is established. By adjusting the latent heat, various forms of isotactic polystyrene crystals, such as dendrites, spherulites, lamellas, etc., can be simulated. Latent heat refers to the heat absorbed or released by a substance from one phase to another and has important physical meaning during the solidification process. The finite difference method was used to solve the model, and then the data were used to visualize. The simulation results were consistent with the experiment. Numerical simulation results under pure diffusion conditions show that the newly established phase field model can qualitatively predict the polymer growth process and provide a theoretical basis for the preparation and optimization of high-performance polymers. In order to make the simulation result closer to the actual growth of the crystal, the flow velocity is added in the simulation to make the melt convection. Under forced convection, the simulated polymer crystal image is no longer symmetrical
Simulation of Stress Distribution near Weld Line in the Viscoelastic Melt Mold Filling Process
Simulations of interface evolution and stress distribution near weld line in the viscoelastic melt mold filling process are achieved according to the viscoelastic-Newtonian two-phase model. The finite volume methods on nonstaggered grids are used to solve the model. The level set method is used to capture the melt interface. The interface evolution of the viscoelastic melt in the mold filling process with an insert in is captured accurately and compared with the result obtained in the experiment. Numerical results show that the stress distribution is anisotropic near the weld line district and the stress distribution varies greatly at different positions of the weld line district due to the complicated flow behavior after the two streams of melt meet. The stress increases quickly near the weld line district and then decreases gradually until reaching the tail of the mold cavity. The maximum value of the stress appears at some point after the insert
Single-switch high step-up boost converter based on a novel voltage multiplier
A single-switch high step-up boost converter based on a novel voltage multiplier (VM) has been proposed in this study. Compared to traditional boost converter, not only the voltage conversion ratio has been increased, but also voltage stress across semiconductor devices has been decreased. Moreover, the voltage conversion ratio and voltage stress of switch of the proposed converter can be adjusted by the number of the VM cells. The control and drive circuits for the proposed converter is as simple as boost converter as there are no additional switches. Working principles and performance characteristics of the proposed converter have been analysed in detail. A 200 W experimental prototype with three VMs has been built to validate the theoretical analysis
Trading methods : consistency of performance in the U.S. & Singapore stock markets?
To compare the consistency of Performance in the U.S. & Singapore Stock Markets
High power high step-up DC/DC converter based on multiple input-terminal voltage multiplier
Voltage multipliers (VMs) are widely used to combine with traditional DC/DC converter to achieve high voltage conversion gain. However, the input-terminals of existing VM circuits are unchangeable to two which make these converters are not suitable for high power/current applications. In this paper, a high power high step-up DC/DC converter based on multiple input-terminal voltage multiplier (MIVM) is presented. Analysis of the operation principles and the performance characteristics of the proposed converter are presented in detail. And an experimental prototype with a rated power of 800W was built to verify the correctness of the theory.</p
A Multi-Input-Port Bidirectional DC/DC Converter for DC Microgrid Energy Storage System Applications
A multi-input-port bidirectional DC/DC converter is proposed in this paper for the energy storage systems in DC microgrid. The converter can connect various energy storage batteries to the DC bus at the same time. The proposed converter also has the advantages of low switch voltage stress and high voltage conversion gain. The working principle and performance characteristics of the converter were analyzed in detail, and a 200 W, two-input-port experimental prototype was built. The experimental results are consistent with the theoretical analysis