Experimental Study of Breakage of Particles under Compression

Granular materials are used widely and can be seen in natural and industrial applications such as sand bags or pharmaceutical pills. During their manufacturing, processing, transport and use, granular materials are subjected to various kinds of loadings. If the amplitude of the loading is above the strength threshold, particles constituting granular materials may fracture. It is very important to understand the failure of particles under these loading conditions to prevent or control their failure during all stages of their manufacturing and use. Better characterization of the fracture behavior of particles composed of different materials and sizes will allow more precise application and better maintenance of granular materials in commercial usage. The effects of size and material properties on the deformation and fracture behavior of granular particles are studied by investigating particles from three different size ranges for three different materials. The mechanical behavior is characterized by force-displacement and stress-strain plots under quasi-static compression (strain rate = 10-2s-1). Along with the deformation behavior, the strengths of particles are also recorded and Weibull distribution is fitted to the fracture stresses. It was observed that the smaller particles break at lower forces but actually withstand higher stress at fracture. The calculated Weibull moduli for different size range and materials show that the flaw population from the manufacturing process is different for different sizes and materials. This study shows that size and material properties alter the fracture stresses. Future experiment can be performed for the same particles under dynamic compression to better understand effects of strain rate on the fracture of particles

Mechanical Properties of Recycled Aggregate Concrete Modified by Nano-particles

In this study, different nano-particles were used to modify recycled aggregates concrete (RAC) containing recycled clay brick aggregates (RCBAs) to improve the RAC properties. Two stages of experimental works were performed. In the first stage, various nano-particle mixtures produced by different mixing methods, i.e. the use of surfactant and ultrasonication, were examined by optical microscope to evaluate the dispersion of the nano-particles in water liquid. The nano-particles modified cement mortar specimens were further evaluated by flexural tensile test to check how these mixing methods affect the properties of the nano-particle modified cement mortar. In the second experimental stage, the effects of four replacement ratios of recycled aggregates, three type of nano-particles, two mixing methods of RAC, additional surfactant and ultrasonication process used in the mix of nano-particle liquid, and the dosages of the nano-particles on the workability, compressive and split tensile properties of the nano-particle modified RAC were investigated

Thermal Behavior of Adhesively Bonded Timber-Concrete Composite Slabs Subjected to Standard Fire Exposure

peer reviewedFire tests were performed for the first time on adhesively bonded timber-concrete composite slabs. The two medium-scale (1.8 x 1.25 m) slabs were produced by gluing an 80-mm thick three-layer cross-laminated timber (CLT) board to a 50 mm thick prefabricated reinforced concrete (RC) slab with epoxy and polyurethane (PUR) adhesives, respectively. The behavior of the composite slabs under elevated temperature was monitored by (1) observing the burning behavior of the used CLT, for example, charring and delamination and (2) measuring the temperature development at different locations of the CLT slabs, in the adhesive bond between concrete and timber boards, and in RC slabs. It was found that employing a one-dimensional charring model for pure softwood, as prescribed by Eurocode 5-1-2, underestimated the charring depth of CLT due to the delamination effects. Measurements revealed that the average charring rates in the middle layer of CLT panels were approximately 0.65 mm/min, suggesting that the presence of concrete does not significantly affect the thermal behavior of the CLT panel. Delamination within the CLT was observed when its adhesive temperature was around 230°C. It was followed by the free-fall of delaminated wood plies, which progressed slowly and lasted until the end of the test. At 90 min into the test, the temperatures of epoxy at the nine locations ranged between 55°C and 130°C, while that of PUR between 60°C and 100°C. The adhesive between concrete and CLT could lose stiffness significantly along the rising of temperature after surpassing of glass transition temperature (58°C for epoxy and 23°C for PUR in this study). The results indicated a high risk of weakening the composite action between the concrete slab and timber board. The measured temperatures of steel rebar were lower than 50°C. However, the concrete temperature reached about 120°C and the concrete cracked due to the distinct thermal expansions between concrete and timber and the rigid constraint of adhesive bond.11. Sustainable cities and communitie

Baichuan 2: Open Large-scale Language Models

Large language models (LLMs) have demonstrated remarkable performance on a variety of natural language tasks based on just a few examples of natural language instructions, reducing the need for extensive feature engineering. However, most powerful LLMs are closed-source or limited in their capability for languages other than English. In this technical report, we present Baichuan 2, a series of large-scale multilingual language models containing 7 billion and 13 billion parameters, trained from scratch, on 2.6 trillion tokens. Baichuan 2 matches or outperforms other open-source models of similar size on public benchmarks like MMLU, CMMLU, GSM8K, and HumanEval. Furthermore, Baichuan 2 excels in vertical domains such as medicine and law. We will release all pre-training model checkpoints to benefit the research community in better understanding the training dynamics of Baichuan 2.Comment: Baichuan 2 technical report. Github: https://github.com/baichuan-inc/Baichuan

Inequality and Political Trust in Contemporary China

Inequality has been a longstanding issue in China. Unresolved debates persist as to whether it poses a substantial threat to the country’s political stability through the undermining of political trust. This thesis proposes that the literature is inconclusive because previous research has relied on oversimplified, unidimensional approaches to study inequality and political trust. Therefore, this thesis advances the debate through employing a conceptually variegated typology of both inequality and political trust. The thesis examines multiple facets of inequality—outcome, opportunity, and procedure—as perceived by the people, as well as their distinct effects on two dimensions of political trust—performance satisfaction and institutional confidence, in the context of contemporary China. Drawing on data from the Chinese General Social Survey 2015 and the Asian Barometer Survey Waves 4 and 5, this research finds that all forms of perceived inequality negatively correlate with political trust, with procedural inequality having the most significant effect. This underscores the importance of addressing inequality, particularly that in procedure, to maintain political stability. The paper also demonstrates a comprehensive framework that illustrates the complex relationship between the three facets of perceived inequality and two dimensions of political trust. As such, the multi-faceted analytical framework used in this study offers new insights, both theoretically and practically, into the complex dynamics between inequality and political trust

Editorial for the Special Issue on Safety and Reliability of Power Electronics Components and Systems

Efficiency and power density have been widely concerned with the development of power electronics, while the safety and reliability issues are attracting more and more attention in a few years due to the increasingly stringent safety requirements, e.g., in electric vehicle, consumer electronics, and aerospace industries. To understand the failure mechanisms and the safe operation area of components/systems in practical applications, comprehensive testing methods considering the operating conditions are becoming essential. Besides accelerated aging tests, multi-physics modeling, physics-of-failure analyses, degradation modeling, electro-thermal simulation, and lifetime assessment contribute to a better understanding of the failure roots in components and systems and the design of a safer system. Moreover, designing condition monitoring and health status estimation tools, fault diagnosis, fault tolerance, and active thermal management techniques help to realize the predictive maintenance of power electronic components and systems. Finally, emerging artificial intelligence (AI) and machine learning (ML) techniques are getting a lot of attention in aging data processing, remaining useful life estimation, etc. Correspondingly, we organized this Special Issue on Safety and Reliability of Power Electronics Components and Systems to collect emerging research achievements within the scope of safety and reliability of power electronics components and systems and circuits