Constructing metamaterials from subwavelength pixels with constant indices product

International audienceWe investigate a two-dimensional metamaterial template constructed from different pixels through a conservation law of effective indices: If the product of refractive indices along the principal axes is invariant for different anisotropic materials in a two-dimensional space, the product of indices of the effective medium remains constant after mixing these materials. Such effective media of constant indices product can be implemented using metamaterial structures. The orientation of the metamaterial structure in a single pixel controls the direction of the principal axis of the effective medium. Different pixels are assembled into an array to obtain reconfigurable anisotropy of the effective medium. These considerations would be useful for constructing reconfigurable metamaterials and transformation media with area-preserving map

A Review of Fibre Reinforced Polymer (FRP) Reinforced Concrete Composite Column Members Modelling and Analysis Techniques

The use of fibre-reinforced polymer (FRP) to confine concrete columns improves the strength and ductility of the columns by reducing passive lateral confinement pressure. Many numerical and analytical formulations have been proposed in the literature to describe the compressive behaviour of FRP confined concrete under both monotonic and cyclic loads. However, the effect of a stress/strain level in the columns has not been well defined because of the lack of well-defined strategies of modelling and oversimplification of the model. This paper reviews the existing FRP combinations and the available numerical and analytical methods to determine the effectiveness of the adopted method. An effort has been made to examine the usage of FRP materials in column applications in existing building regimes and highlights the possible future scopes to improve the use of FRP confined concrete in civil applications

Through the Lens of Core Competency: Survey on Evaluation of Large Language Models

From pre-trained language model (PLM) to large language model (LLM), the field of natural language processing (NLP) has witnessed steep performance gains and wide practical uses. The evaluation of a research field guides its direction of improvement. However, LLMs are extremely hard to thoroughly evaluate for two reasons. First of all, traditional NLP tasks become inadequate due to the excellent performance of LLM. Secondly, existing evaluation tasks are difficult to keep up with the wide range of applications in real-world scenarios. To tackle these problems, existing works proposed various benchmarks to better evaluate LLMs. To clarify the numerous evaluation tasks in both academia and industry, we investigate multiple papers concerning LLM evaluations. We summarize 4 core competencies of LLM, including reasoning, knowledge, reliability, and safety. For every competency, we introduce its definition, corresponding benchmarks, and metrics. Under this competency architecture, similar tasks are combined to reflect corresponding ability, while new tasks can also be easily added into the system. Finally, we give our suggestions on the future direction of LLM's evaluation

Lightweight bamboo structures - Report on 2021 International Collaboration on Bamboo Construction

2021 International Collaboration on Bamboo Construction was held from September 1 to December 1, 2021. The practice was held by the College of Civil Engineering of Nanjing Forestry University, University College London, International Bamboo and Rattan Organisation (INBAR) and co-organized by 6 international institutions and national companies of China. Two main bamboo structures were setup by the teachers and students in the campus of Nanjing Forestry University. More than 50 students attended the practice, including international students from different countries. The practice was held to deliver the feasibility and applicability of bamboo in various geometries and different spans, and different areas. Innovative technologies like BIM Revit Architecture and Sketchup were used for the design of bamboo structures. The main principle of the practice was that the raising of bamboo structures should be simple using a minimum of materials aside from bamboo. The results of the project contributed to the popularization of the use of bamboo in the architecture, engineering and construction sectors

Quasi-Consensus of Time-Varying Multi-Agent Systems with External Inputs under Deception Attacks

The quasi-consensus of a class of nonlinear time-varying multi-agent systems suffering from both external inputs and deception attacks is studied in this paper. This is different from a time-varying matrix, which is assumed to be bounded; further reasonable assumptions are supposed. In addition, impulsive deception attacks modeled with Bernoulli variables are considered. Sufficient conditions to achieve quasi-consensus are given, and the upper bounds of the error state related to the deception attacks is derived. Finally, a numerical simulation example is provided to show the validity of the obtained results

Quasi-Consensus of Time-Varying Multi-Agent Systems with External Inputs under Deception Attacks

The quasi-consensus of a class of nonlinear time-varying multi-agent systems suffering from both external inputs and deception attacks is studied in this paper. This is different from a time-varying matrix, which is assumed to be bounded; further reasonable assumptions are supposed. In addition, impulsive deception attacks modeled with Bernoulli variables are considered. Sufficient conditions to achieve quasi-consensus are given, and the upper bounds of the error state related to the deception attacks is derived. Finally, a numerical simulation example is provided to show the validity of the obtained results

Design of a class of fractional-order analog wavelet filters

In this article, a methodology is proposed to implement fractional-order analog wavelet filters in the frequency domain. Under the proposed scheme, the fractional-order transfer function of the linear time-invariant system is used to approximate the Gaussian-like wavelet functions. Firstly, we construct a causal, stable, and physically achievable fractional-order mathematical approximation model. Then, the fractional-order mathematical approximation model is transformed into an optimization problem, and a hybrid particle swarm optimization algorithm is exploited to find its global optimal solution. At the same time, constraint terms are introduced to ensure the desired stability. The simulation results show that the fractional-order analog wavelet filters have higher approximation accuracy than the traditional integer-order analog wavelet filters. Furthermore, fractional-order analog wavelet filters can provide more precise control of the stopband attenuation rate, which is a key issue for many engineering applications