Performance of spiral-shaped steel fibre reinforced concrete structure under static and dynamic loads

Concrete is the most widely used construction material due to its impressive resistance to compressive load. The major weaknesses of concrete are its brittleness and poor resistance to tensile forces. Intensive number of studies has been conducted to add various types of short discrete fibres into concrete mix to enhance its ductility and post-peak load-bearing capacity. A spiral-shaped steel fibre was recently proposed for reinforcing concrete material with 3D bond components. A series of laboratory tests have been conducted for a comprehensive investigation of the performances of spiral-shaped steel fibre reinforced concrete materials and structures. A fundamental understanding of the bond-slip behaviour of spiral fibres and its mechanism of reinforcing the matrix was achieved by conducting pull-out tests. Compressive and direct tensile tests on Ø100-200 mm concrete specimens with spiral fibres of different geometries were conducted for properly determining fibre geometries to reinforce concrete materials. Split Hopkinson pressure bar (SHPB) tests were carried out to study the dynamic behaviour of spiral steel fibre reinforced concrete (SFRC) with various volume fractions under compression and splitting tension. The corresponding relations of dynamic increase factor (DIF) vs. strain rate were proposed based on test data. Repeated drop-weight impact tests on SFRC beams reinforced with the commonly-used hook-end fibres and spiral fibres were performed. Test results demonstrated the superiority of spiral fibres in bonding and enhancing concrete structural elements in resisting impact loads. The even distributions of spiral fibres in comparison with crimped fibres in concrete matrix were justified by physical examinations. Mesoscale simulations with distinctive consideration of mortar matrix, coarse aggregates and spiral fibres were conducted for statistical derivation of dynamic properties of spiral SFRC. While having demonstrated the promising performances of concrete reinforced with spiral fibres, further studies are also suggested based on the observations and results obtained

An analysis of the translation of vocabulary lists in textbooks for teaching Chinese as a foreign language (TCFL)

Recent research in the Teaching Chinese as a Foreign Language (TCFL) field has focused on the pedagogical perspectives underlying TCFL textbooks and their compilation. With the increasing interaction between China and other countries in global contexts such as culture, economics and commerce, there is a great need to expand research regarding all areas and issues within TCFL, especially in the important area of vocabulary and its translation in TCFL textbooks (Tsung and Cruickshank, 2011). This research investigates a range of translation problems related to the accuracy of the vocabulary lists featured in 12 selected representative TCFL textbooks for teaching Chinese as a foreign language. This thesis presents findings from three triangulation cases (questionnaire survey, corpus research, and assessment test) involving two different groups of participants (e.g. Chinese teachers who completed the questionnaire survey and Chinese undergraduates majoring in English who underwent the assessment test). The contribution of this study is as follows: 1) I conduct a series of empirical evidence based on the viewpoints of practitioners regarding the identified translation problems to fill the gap that there are more descriptive and pedagogical works in the vocabulary translation of TCFL textbooks; 2) I adopt functional equivalence theory of translation and linguistics–based approaches (semantic, pragmatic and grammatical perspectives) to establish a theoretical framework which provides a flexible way of analysing translation and enables the original meanings of Chinese words to be analysed through various perspectives, especially for Chinese and English vocabulary analysis and translation; 3) I draw on translation quality evaluation theory to generate a translation quality evaluation framework which can serve as a reference point for other translation evaluation work regarding vocabulary conducted during other relevant studies; 4) I demonstrate that the majority of translation problems gathered from the selected TCFL textbooks were found at the preliminary level and in the content word class which have much practical relevance and research value for the pedagogical purpose of vocabulary teaching and translation; and 5) I build up a specific parallel corpus with passages and vocabulary lists of the selected TCFL textbooks

Study on Queuing System Optimization of Bank Based on BPR

AbstractThis paper focuses on improving the queuing system of bank based on BPR. Firstly, the bottleneck problems of bank queuing is analyzed as well as the concept, classification and methodologies of BPR (business process reengineering). Secondly, the bank businesses are investigated and analyzed. Thirdly, the queuing system of certain bank is optimized based on BPR by enterprise dynamic simulation. Finally, the simulated results are discussed and the optimized result is concluded

A Systematic Security Evaluation of Android's Multi-User Framework

Like many desktop operating systems in the 1990s, Android is now in the process of including support for multi-user scenarios. Because these scenarios introduce new threats to the system, we should have an understanding of how well the system design addresses them. Since the security implications of multi-user support are truly pervasive, we developed a systematic approach to studying the system and identifying problems. Unlike other approaches that focus on specific attacks or threat models, ours systematically identifies critical places where access controls are not present or do not properly identify the subject and object of a decision. Finding these places gives us insight into hypothetical attacks that could result, and allows us to design specific experiments to test our hypothesis. Following an overview of the new features and their implementation, we describe our methodology, present a partial list of our most interesting hypotheses, and describe the experiments we used to test them. Our findings indicate that the current system only partially addresses the new threats, leaving the door open to a number of significant vulnerabilities and privacy issues. Our findings span a spectrum of root causes, from simple oversights, all the way to major system design problems. We conclude that there is still a long way to go before the system can be used in anything more than the most casual of sharing environments.Comment: In Proceedings of the Third Workshop on Mobile Security Technologies (MoST) 2014 (http://arxiv.org/abs/1410.6674

Alignment and Outer Shell Isotropy for Hyperbolic Graph Contrastive Learning

Learning good self-supervised graph representations that are beneficial to downstream tasks is challenging. Among a variety of methods, contrastive learning enjoys competitive performance. The embeddings of contrastive learning are arranged on a hypersphere that enables the Cosine distance measurement in the Euclidean space. However, the underlying structure of many domains such as graphs exhibits highly non-Euclidean latent geometry. To this end, we propose a novel contrastive learning framework to learn high-quality graph embedding. Specifically, we design the alignment metric that effectively captures the hierarchical data-invariant information, as well as we propose a substitute of uniformity metric to prevent the so-called dimensional collapse. We show that in the hyperbolic space one has to address the leaf- and height-level uniformity which are related to properties of trees, whereas in the ambient space of the hyperbolic manifold, these notions translate into imposing an isotropic ring density towards boundaries of Poincar\'e ball. This ring density can be easily imposed by promoting the isotropic feature distribution on the tangent space of manifold. In the experiments, we demonstrate the efficacy of our proposed method across different hyperbolic graph embedding techniques in both supervised and self-supervised learning settings

Video Action Recognition with Attentive Semantic Units

Visual-Language Models (VLMs) have significantly advanced action video recognition. Supervised by the semantics of action labels, recent works adapt the visual branch of VLMs to learn video representations. Despite the effectiveness proved by these works, we believe that the potential of VLMs has yet to be fully harnessed. In light of this, we exploit the semantic units (SU) hiding behind the action labels and leverage their correlations with fine-grained items in frames for more accurate action recognition. SUs are entities extracted from the language descriptions of the entire action set, including body parts, objects, scenes, and motions. To further enhance the alignments between visual contents and the SUs, we introduce a multi-region module (MRA) to the visual branch of the VLM. The MRA allows the perception of region-aware visual features beyond the original global feature. Our method adaptively attends to and selects relevant SUs with visual features of frames. With a cross-modal decoder, the selected SUs serve to decode spatiotemporal video representations. In summary, the SUs as the medium can boost discriminative ability and transferability. Specifically, in fully-supervised learning, our method achieved 87.8% top-1 accuracy on Kinetics-400. In K=2 few-shot experiments, our method surpassed the previous state-of-the-art by +7.1% and +15.0% on HMDB-51 and UCF-101, respectively.Comment: Accepted at ICCV 202

Predicting the response of locally resonant concrete structure under blast load

Ternary locally resonant metamaterial (LRM) is a manmade material consisting of rigorously designed heavy inclusions with coated soft layer. Such design enables the LRM to possess good wave-filtering characteristics that differ from the matrix materials. Researches of application of this new material for seismic isolation and sound insulation in civil engineering have been reported. In recent decades, there has been an increasing demand to protect civil engineering structures against the effects of blast loading. When blast wave acts on a concrete structure, complex stress waves are generated and propagate in the structure. The wave-filtering characteristics of LRM have brought inspiration to investigate its potential application to reduce the stress wave propagation and hence the damage to cementitious material and enhance the performance of structures under blast wave. By embedding heavy inclusions with soft coating layer into mortar matrix, the product can be named as ternary locally resonant concrete (ternary LRC). Previous studies of the performances of ternary LRC structures are mainly limited to finite element (FE) modeling of elastic wave propagation. The study of the performance of ternary LRC structure subjected to blast loading and the influence of blast loading-induced damage to LRC structure on stress wave propagation is very limited. This paper carries out analytical derivation and numerical modelling to study the mechanism and performance of ternary LRC structure under blast loading. The strain rate effect and material damage of the mortar matrix are considered in numerical simulation. The influence of different material inclusions (natural aggregates and lead), different elastic modulus and thickness of the soft coating on the response of ternary LRC structure are studied. The results show that the ternary LRC can effectively reduce the damage of ternary LRC structure subjected to blast loading

Effect of correlated oxide electrodes on disorder pinning and thermal roughening of ferroelectric domain walls in epitaxial PbZr\u3csub\u3e0.2\u3c/sub\u3eTi\u3csub\u3e0.8\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e thin films

We report the competing effects of disorder pinning and thermal roughening on ferroelectric domain walls as a function of temperature in epitaxial PbZr0.2Ti0.8O3 thin films deposited on (001) SrTiO3 substrates buffered by three types of correlated oxide electrodes, La0.67Sr0.33MnO3, LaNiO3, and SrIrO3. Piezoresponse force microscopy studies show that the 50-nm PbZr0.2Ti0.8O3 films are uniformly polarized in the as-grown states, with the patterned domain structures persisting above 700 °C. For all three types of films, the domain wall roughness is dominated by two-dimensional (2D) random bond disorder at room temperature, and transitions to 1D thermal roughening upon heating. The roughness exponent ζ increases progressively from 0.3 to 0.5 within a temperature window that depends on the bottom conducting oxide type, from which we extracted the distribution of disorder pinning energy. We discuss the possible origins of the disorder pinning and the effect of the correlated oxide electrodes on the energy landscape of DW motion