Interfacial ionic transport in natural palygorskite-Na0.60CoO2 nanocomposite mineral materials

Natural clay minerals have been applied to various energy fields due to their low cost, good stability, and abundance of resources, but few of them have been investigated for fuel cell application. Proton ceramic fuel cell, one of the most promising sustainable-energy-conversion technologies, has attracted a lot of attentions because it possesses high ionic conductivity at relatively low temperatures (<600 °C). However, the characteristics of expensive construction cost and high temperature operation hinder the development and industrialization of fuel cell. In this paper, natural clay minerals palygorskite (PAL) and Na_0.60CoO₂ (NCO) nanosheets composite were synthesized via an electrostatic adsorption method, and used as the electrolyte of fuel cell. NCO/PAL demonstrated a high conductivity of 0.27 S?cm^?1 at 550 °C and the maximum power output of 641 mW cm^?2 was achieved for NCO/PAL cell. The mechanism of proton transport at the interface of NCO/PAL semiconductor-insulator composite was discussed.     

Reinforcement Learning for feedback-enabled cyber resilience

The rapid growth in the number of devices and their connectivity has enlarged the attack surface and made cyber systems more vulnerable. As attackers become increasingly sophisticated and resourceful, mere reliance on traditional cyber protection, such as intrusion detection, firewalls, and encryption, is insufficient to secure the cyber systems. Cyber resilience provides a new security paradigm that complements inadequate protection with resilience mechanisms. A Cyber-Resilient Mechanism (CRM) adapts to the known or zero-day threats and uncertainties in real-time and strategically responds to them to maintain the critical functions of the cyber systems in the event of successful attacks. Feedback architectures play a pivotal role in enabling the online sensing, reasoning, and actuation process of the CRM. Reinforcement Learning (RL) is an important gathering of algorithms that epitomize the feedback architectures for cyber resilience. It allows the CRM to provide dynamic and sequential responses to attacks with limited or without prior knowledge of the environment and the attacker. In this work, we review the literature on RL for cyber resilience and discuss the cyber-resilient defenses against three major types of vulnerabilities, i.e., posture-related, information-related, and human-related vulnerabilities. We introduce moving target defense, defensive cyber deception, and assistive human security technologies as three application domains of CRMs to elaborate on their designs. The RL algorithms also have vulnerabilities themselves. We explain the major vulnerabilities of RL and present develop several attack models where the attacker target the information exchanged between the environment and the agent: the rewards, the state observations, and the action commands. We show that the attacker can trick the RL agent into learning a nefarious policy with minimum attacking effort. The paper introduces several defense methods to secure the RL-enabled systems from these attacks. However, there is still a lack of works that focuses on the defensive mechanisms for RL-enabled systems. Last but not least, we discuss the future challenges of RL for cyber security and resilience and emerging applications of RL-based CRMs.     

Recent progress in synthesis of lanthanide-based persistent luminescence nanoparticles

Persistent luminescence nanoparticles (PLNPs) are a kind of phosphors that can remain luminescent for seconds to several days after the stoppage of excitation. Lanthanides show the special capability to largely broaden the emission range and enhance the luminescence intensity of PLNPs due to their dense energy structure and unique electronic configurations. In the past decades, various methods have been developed for the synthesis of lanthanide-based PLNPs with excellent persistent luminescence properties, and the lanthanide-based PLNPs are widely studied in areas including biomedicine, energy, and information storage. In this review, we summarized the research progress in the synthesis of lanthanide-based PLNPs and outlined several typical synthesis methods. We discussed the fundamental concepts of preparation methods as well as the advantages and drawbacks of the typical synthetic approaches. Moreover, the current challenges and the potential solutions for the development of lanthanide-based PLNPs are also discussed in an attempt to provide strategies to further improve the optical properties of lanthanide-based PLNPs. We hope this review can contribute to the design of lanthanide-based PLNPs with desired properties and further promote their applications in biomedicine, energy, and information science.     

Advanced extraction techniques for Berberis species phytochemicals: A review

Berberis species are known for their functional and nutraceutical properties. For example, different Berberis species have shown a wide range of pharmacological activities and they have been used in food industries as additives, preservatives and antioxidants. The functional property of any herb is influenced by many factors including the extraction process of its active components. Consequently, new extraction methodologies have been investigated to increase the efficiency of extracting bioactive compounds. In this review, we examine all the recent extraction techniques and advanced technologies that have been applied for the extraction of phytochemicals from different Berberis species. The five following techniques have been included for this purpose: ultrasound-, microwave-, pulsed electric field-assisted, supercritical carbon dioxide and subcritical water extraction. These techniques have been used to extract phenolics, flavonoids, anthocyanins and berberine from different parts of various Berberis species which include B. vulgaris, B. jaeschkeana, B. aristata, B. integerrima, B. dasystachya and B. koreana. Microwave-assisted extraction (MAE) has been well studied, optimised and evaluated. Yet, the present research considering other techniques are limited, and require further investigation and optimisation. In addition, the application of green solvents such as natural deep eutectic solvents could be considered in further developing MAE.     

准大采高综放工作面矿压特征的研究

本文以同煤集团云冈矿8212工作面地质条件为背景,对工作面矿压规律进行实测分析研究,结果表明:1)工作面支架平均工作阻力为2 016.1 k N,占其额定工作阻力(7 000 k N)的28.8%,该工作面支架的额定工作阻力可以满足顶板的管理要求。支架前后柱工作阻力分布较平均,能正常工作。2)工作面支架平均循环末阻力为3 147.0 k N,占其额定工作阻力(7 000 k N)的45.0%,该工作面平均循环末阻力主要分布区间为2 800~3 800 k N,即工作面支架的额定工作阻力完全可以支撑顶板。3)工作面超前支承压力作用范围在35~38 m处,随工作面的逐步推进,其增幅也逐步增加。该结论可为类似条件下其他工作面开采过程中矿压显现规律的研究提供参考。     

First principles insights into improved catalytic performance of BaTiO3- graphene nanocomposites in conjugation with experimental investigations

The present work aims to provide first principles insights into the catalytic performance of composites based on BaTiO₃ particles decorated over reduced graphene oxide (rGO). Examination regarding the orbital contributions of valence states, conduction states, interaction surface and anchoring of perovskite over rGO have been carried out. Theoretical results thus obtained have been validated using experimental investigation. Further experiments have also been conducted to analyze the catalytic performance of composites with respect to multiple advanced oxidation processes. Charge separation has been improved due to rGO acting as macromolecular photosensitizer. Degradation of xanthene dye (Rhodamine B) and methyl orange (MO) assisted in evaluation of the catalytic performance. Acoustic irradiation provides an additional route to improve degradation by ameliorating catalytic activity (from 0.036 min to 0.099 min in RhB especially). Synergistic effect obtained through conjugated benefits of oxidation processes with proposed composite, played a crucial role in improving the overall efficiency. The cumulative outcome of the results indicates superior performance of BaTiO₃-rGO composites for green and sustainable water treatment applications.     

Environmental and Dynamic Conditions for the Occurrence of Persistent Haze Events in North China

This paper presents a concise summary of recent studies on the long-term variations of haze in North China and on the environmental and dynamic conditions for severe persistent haze events. Results indicate that haze days have an obviously rising trend over the past 50 years in North China. The occurrence frequency of persistent haze events has a similar rising trend due to the continuous rise of winter temperatures, decrease of surface wind speeds, and aggravation of atmospheric stability. In North China, when severe persistent haze events occur, anomalous southwesterly winds prevail in the lower troposphere, providing sufficient moisture for the formation of haze. Moreover, North China is mainly controlled by a deep downdraft in the mid-lower troposphere, which contributes to reducing the thickness of the planetary boundary layer, obviously reducing the atmospheric capacity for pollutants. This atmospheric circulation and sinking motion provide favorable conditions for the formation and maintenance of haze in North China.     

Plutonium and Minor Actinides incineration options using innovative Na-cooled fast reactors: Impacting on phasing-out and on-going fuel cycles

The flexibility of innovative Na-cooled fast reactors for burning Pu and/or Minor Actinides (MA) is investigated with respect to different fuel cycle strategies. Under phasing-out conditions, the burner systems are used for reducing to a minimum level the accumulated TRansUranic (TRU) inventory, whereas when continuous use of nuclear energy is envisaged (on-going case), burner systems may be dedicated to MA management only.As an example of a phasing-out case, the accumulated German TRU inventory (at 2022) is assumed to be transmuted in a chosen time period of 150 years. For this purpose, two different burner fast reactors concepts, developed at KIT, are deployed in a Partitioning and Transmutation based fuel cycle. The effects are analyzed in order to confirm the behavior expected by the neutronics studies and to provide a basis for further optimization of the scenarios with respect to a number of reactors, deployment paces and fuel compositions.Additionally the performance of the MA burner is assessed to provide an effective MA mass stabilization in case of a continuous use of nuclear energy. Preliminary results are compared with those of past studies based on the European Sodium-cooled Fast Reactor.     

Porosity and pore size distribution influence on thermal conductivity of yttria-stabilized zirconia: Experimental findings and model predictions

Porous yittria-stabilized zirconia is an important advanced ceramic material for technological applications. One of the most important characteristics of this material is low thermal conductivity, which is greatly influenced by the presence of pores into the microstructure. In fact, air trapped in the pores represents a better thermal insulator. The role of the pore volume fraction on porous material characteristics has been extensively studied. On the other hand, the influence of the structure disorder, the pore size range and pore size distribution have been studied much less. In this study, an intermingled fractal model capable of relating thermal properties of ceramic materials and their pore microstructure has been proposed. Model predictions are found confirming the experimental data fairly well, even better than the others models available in the literature.     

GRINDING OF NICKEL-BASED SUPER-ALLOYS AND ADVANCED CERAMICS

This paper studies grinding of Inconel 718, Hastelloy, and some advanced ceramics. A newly developed ultra-high-speed grinding machine and a conventional grinding machine were used for the experiments. The ultra-high-speed grinding machine is equipped with a specially designed and built spindle unit that can run up to 200 m sec^-1 and deliver a maximum output of 12 kW. The surface roughness and residual stress values of the ground super-alloys and advanced ceramics were measured using a profilometer and a residual stress analyzer, respectively. The ground surfaces were also assessed using a scanning electron microscope. The effect of h_m (undeformed chip thickness) on surface topography of the difficult-to-machine materials was also investigated. A higher grinding wheel speed produces a smaller cutting depth and undeformed chip thickness, and thus smaller grinding force, decreased residual surface stress, and better surface finish. High productivity and good surfaces with ductile streaks could be obtained by employing ultra-high-speed grinding, even at very large wheel depths of cut such as 400 μm, without cross feed.