Multifunctional cementitious composites with integrated self-sensing and self-healing capacities using carbon black and slaked lime

This study aims to develop multifunctionality of cementitious composites with the integrated self-sensing and self-healing capacities by incorporating conductive carbon black (CB) with CB-encapsulated slaked lime (SL). The microsized SL particles were premixed with a half of designed content of nanosized CB particles. When CB agglomerations coat around the SL surfaces, SL does not hydrate until the CB coating is removed. Another half of designed weight of CB is uniformly dispersed using ultrasonication with superplasticizer and added to obtain piezoresistivity. The results show that the stress sensing capacity of CB-SL-cementitious composite performs well with the compressive stress. Autogenous healing performances presented significantly can improve the self-healing capacity with the increase of SL. Furthermore, the healing efficiency is affected by the crack width and dispersion of SL, and the smaller cracks with SL are more easily healed. The size of CB agglomerations decreases with the added SL, and the main product of self-healing is calcium carbonate.     

A precise sensor fault detection technique using statistical techniques for wireless body area networks

One of the major challenges in wireless body area networks (WBANs) is sensor fault detection. This paper reports a method for the precise identification of faulty sensors, which should help users identify true medical conditions and reduce the rate of false alarms, thereby improving the quality of services offered by WBANs. The proposed sensor fault detection (SFD) algorithm is based on Pearson correlation coefficients and simple statistical methods. The proposed method identifies strongly correlated parameters using Pearson correlation coefficients, and the proposed SFD algorithm detects faulty sensors. We validated the proposed SFD algorithm using two datasets from the Multiparameter Intelligent Monitoring in Intensive Care database and compared the results to those of existing methods. The time complexity of the proposed algorithm was also compared to that of existing methods. The proposed algorithm achieved high detection rates and low false alarm rates with accuracies of 97.23% and 93.99% for Dataset 1 and Dataset 2, respectively.     

Touch sensor and photovoltaic characteristics of CuSbS2 thin films

Spin-coated chalcostibite CuSbS₂ thin films (≈500 nm thick) were fabricated and the influence of the drying temperature on the structural, morphological, optical and thermoelectric properties of the films was investigated. Crystalline phase-pure chalcostibite has been obtained for the films dried at 180 °C and 210 °C, while below 180 °C these films are partially amorphous. Surprisingly, at drying temperature of 240 °C, a Cu_xS secondary phase appeared. The increase of the drying temperature leads to the increase of the particle size and the decrease of the optical band gap, which is interesting for optoelectronic applications. The highest power factor value was achieved for the film dried at 210 °C, due to the inexistence of secondary phases, which allowed realizing a stable thermoelectric touch sensor with a V_signal/_noise of 5. In addition, this film was tested as a photovoltaic (PV) device and a power conversion efficiency (PCE) of 0.030% with an open-circuit voltage (V_OC) of 0.36 V, a short-circuit current density (J_SC) of 0.278 mAcm^?2 and a fill factor (FF) of 0.27 were obtained. Therefore, this work evidences a pathway toward developing bi-functional devices with simultaneously thermoelectric touch sensor and photovoltaic functions.     

Towards artificial intelligence at scale in the chemical industry

In the Industry 4.0 era, the chemical industry is embracing broad adoption of artificial intelligence (AI) and machine learning (ML) methods. This article provides a holistic view of how the industry is transforming digitally towards AI at scale. First, a historical perspective on how the industry used AI to aid humans in better decision-making is shown. Then state-of-the-art AI research addressing industrial needs on reliability and safety, process optimization, supply chain, material discovery, and reaction engineering is highlighted. Finally, a vision of the plant of the future is illustrated with critical components of AI-ready culture, model life cycle management, and renewed role of humans in chemical manufacturing.     

Influence of substrate temperature on the microstructure of YSZ films and their application as the insulating layer of thin film sensors for harsh temperature environments

Thin film sensors are employed to monitor the health of hot-section components of aeroengine intelligence (for instance, blades), and electrical insulating layers are needed between the metal components and thin film sensors. For this purpose, the electrical insulation characteristics of an yttria-stabilized zirconia (YSZ)/Al₂O₃ multilayer insulating structure were investigated. First, YSZ thin films were deposited by DC reactive sputtering at various substrate temperatures, and the microstructural features were investigated by scanning electron microscopy and X-ray diffraction. The results indicate that the micromorphology of the YSZ thin film gradually became denser with increasing substrate temperature, and no new phases appeared. The compact and uniform topography of the YSZ thin film improved the insulation properties of the multilayer insulating structure and enhanced the adhesion of the thin film sensors. In addition, the electrical insulation properties of the YSZ/Al₂O₃ multilayer insulating structure were evaluated via insulation resistance tests from 25 to 800 °C, in which the YSZ thin film was deposited at 550 °C. The results show that the insulation resistance of the multilayer structure increased by an order of magnitude compared with that of the conventional Al₂O₃ insulating layer, reaching 135 kΩ (5.1 × 10^?6 S/m) at 800 °C. Notably, the insulation resistance was still greater than 75 kΩ after annealing at 800 °C for 5 h. Finally, the shunt effect of the YSZ/Al₂O₃ multilayer insulating structure was estimated using a PdCr thin film strain gauge. The relative resistance error was 0.24%, which demonstrates that the YSZ/Al₂O₃ multilayer insulating structure is suitable for thin film sensors.     

High-temperature electrical properties of polymer-derived ceramic SiBCN thin films fabricated by direct writing

The in situ temperature monitoring of hot components in harsh environments remains a challenging task. In this study, SiBCN thin-film resistance grids with thicknesses of 1.8 μm were fabricated on alumina substrates via direct writing. Owing to their dense microscopic morphology and extremely high graphitisation level, the produced SiBCN films exhibited large high-temperature oxidation resistance and electrical conductivity. The resistance–temperature, stability, and repeatability characteristics of these films were examined in an aerobic environment at temperatures up to 800 °C. The obtained results revealed that the thermistor resistance decreased monotonously with increasing temperature from room temperature to 800 °C. The SiBCN film resistance variations observed during repeated temperature cycling in the regions of 505–620 °C and 610–720 °C were 0.09% and 1.7%, respectively. The high cyclability and stability of the SiBCN thin film thermistor suggested its potential applicability for the in situ temperature monitoring of hot components in harsh environments.     

Enhanced upconversion luminescence and optical temperature sensing performance in Er3+ doped BaBi2Nb2O9 ferroelectric ceramic

A series of BaBi_2-xNb₂Er_xO₉ ceramic compositions with different Er³⁺ concentration (x = 0.0–8 mol %) is synthesized by a conventional solid-state reaction method. The upconversion (UC) light emission under 980 nm excitation with different pump powers and luminescence-based temperature sensing ability of BaBi_2-xNb₂Er_xO₉ composition have been examined. The formation of a Bi-layered perovskite phase of BaBi₂Nb₂O₉ is confirmed having an orthorhombic geometry and Fmmm space group. Shifts in the Raman modes indicate reduced interaction of Bi³⁺ ions with NbO₆ octahedron leading to relaxation of structural distortion with increasing Er³⁺ content. The maximum value for remnant polarization and coercive field of doped BaBi_2-xNb₂Er_xO₉ ceramic for (x = 0.08) Erbium concentration comes out to be 2.9524 μC/cm² and 49.8980 kV/cm. For an optimum content of x = 0.04, two strong UC green emission bands were observed at 549 nm via ⁴S_3/2 → ⁴I_15/2 transition and 527 nm via ²H_11/2 → ⁴I_15/2 transitions, and a weak red emission appears at 657 nm attributed to the ⁴F_9/2 → ⁴I_15/2 transition. Pump power dependence suggests that UC emission is a two-photon mechanism for red and green emission bands. Temperature sensing evaluated by the change in the fluorescence intensity ratio (I₅₂₇/I₅₄₉) indicates the highest sensitivity to be 0.00996 K^?1 at 483 K for an optimum concentration of Er³⁺ at x = 0.04 in BaBi_2-xNb₂Er_xO₉ composition and is useful for non-contact optical thermometry.     

Maximum Data Generation Rate Routing Protocol Based on Data Flow Controlling Technology for Rechargeable Wireless Sensor Networks

For rechargeable wireless sensor networks, limited energy storage capacity, dynamic energy supply, low and dynamic duty cycles cause that it is unpractical to maintain a fixed routing path for packets delivery permanently from a source to destination in a distributed scenario. Therefore, before data delivery, a sensor has to update its waking schedule continuously and share them to its neighbors, which lead to high energy expenditure for reestablishing path links frequently and low efficiency of energy utilization for collecting packets. In this work, we propose the maximum data generation rate routing protocol based on data flow controlling technology. For a sensor, it does not share its waking schedule to its neighbors and cache any waking schedules of other sensors. Hence, the energy consumption for time synchronization, location information and waking schedule shared will be reduced significantly. The saving energy can be used for improving data collection rate. Simulation shows our scheme is efficient to improve packets generation rate in rechargeable wireless sensor networks.     

0Cr17Ni4Cu4Nb传感器断裂原因分析

某力学传感器在出厂检验流程中发生断裂失效,为了确定失效原因,防止此类失效事件再次发生,实验对该传感器的力学性能、金相组织和断口形貌进行了分析,确定了断裂原因。结果表明,传感器的失效模式为氢致延迟开裂,材料中氢含量偏高和开裂位置机加工质量较差是导致传感器发生氢致开裂的主要原因。结合失效原因,提出了改进措施。     

基于改进耦合增强随机共振的滚动轴承故障诊断

针对强背景噪声下经典随机共振方法对滚动轴承故障特征提取效果差的问题,提出了一种基于改进耦合增强随机共振的滚动轴承故障诊断方法。首先,利用一个定参双稳系统和一个变参双稳系统构成耦合随机共振系统,外部输入直接作用于定参双稳系统;然后,通过调节变参双稳系统参数和耦合系数实现耦合系统的随机共振控制,并借助遗传算法实现控制参数的自适应选取。实验和工程应用验证了所提方法的有效性和优越性。