Flash joining of alumina ceramics under a small current density

The ceramic joining using electric field (E-field) has garnered significant research attention due to the decreased joining barrier and enhanced reliability. However, the underlying mechanism of E-field assisted joining remains unclear. Herein, we report the rapid joining of alumina ceramics using a small current. Moreover, the E-field is applied in both perpendicular and parallel directions to the faying surfaces, demonstrating a significant difference in terms of joint strength. These results indicate that the E-field generates defects and promotes the joining process by facilitating ionic diffusion.     

Exponential Set-Point Stabilization of Underactuated Vehicles Moving in Three-Dimensional Space

This paper investigates the stabilization of underactuated vehicles moving in a three-dimensional vector space. The vehicle’s model is established on the matrix Lie group SE(3), which describes the configuration of rigid bodies globally and uniquely. We focus on the kinematic model of the underactuated vehicle, which features an underactuation form that has no sway and heave velocity. To compensate for the lack of these two velocities, we construct additional rotation matrices to generate a motion of rotation coupled with translation. Then, the state feedback is designed with the help of the logarithmic map, and we prove that the proposed control law can exponentially stabilize the underactuated vehicle to the identity group element with an almost global domain of attraction. Later, the presented control strategy is extended to set-point stabilization in the sense that the underactuated vehicle can be stabilized to an arbitrary desired configuration specified in advance. Finally, simulation examples are provided to verify the effectiveness of the stabilization controller.      

Assessing green energy growth in Nepal with a hydropower-hydrogen integrated power grid model

The involvement of green hydrogen in energy transformation is getting global attention. This assessment examines the hydrogen production and its utilization potential in one of the hydropower-rich regions, Nepal under various demand growth and technology intervention scenarios by developing a power grid model of 52 nodes and 68 transmission lines operating at an hourly time-step. The model incorporates a grid-connected hydrogen storage system as well as charging stations for electric and hydrogen vehicles. The least-costly pathways for power grid expansion at the nodal and provincial levels are identified through optimization. The results show that 32 GW of installed capacity is required to meet domestic electricity demand and 14 GW more hydropower should be exploited to completely decarbonize the transport sector by 2050. For maintaining 50% shares of hydrogen vehicle in the transport sector and meet government electricity export targets, Nepal requires 5.7 GW, 12 GW and 23 GW of the additional electrolyzer, hydrogen storage tanks and storage-based hydropower capacities respectively. For a given electricity demand, introducing hydrogen systems can reduce the capacity requirements of hydro storage by storing surplus power generated from pondage run-of-the-river and run-of-the-river hydropower during the rainy season and using it in the dry season.     

Selection of features from power theories to compose NILM datasets

The load disaggregation concept is gaining attention due to the increasing need for optimized energy utilization and detailed characterization of electricity consumption profiles, especially through Nonintrusive Load Monitoring (NILM) approaches. This occurs since knowledge about individualized consumption per appliance allows to create strategies striving for energy savings, improvement of energy efficiency, and creating energy awareness to consumers. Moreover, by using feature extraction to devise energy disaggregation, one can achieve accurate identification of electric appliances. However, even though several literature works propose distinct features to be utilized, no consensus exists in the literature about the most appropriate set of features that ensure high accuracy on load disaggregation. Thus, beyond presenting a critical analysis of some significant features often selected in the literature, this paper proposes identifying the most relevant ones considering collinearity and machine learning algorithms. The results show that high-performance metrics can be achieved with fewer features than usually adopted in the literature. Moreover, it is demonstrated that the Conservative Power Theory can offer the most representative features for appliance identification, leading to efficient power consumption disaggregation.     

润滑油基础油与添加剂对电动汽车传动液导电性能的影响

针对电动汽车电机、减速器、控制器“三合一”集成驱动系统对传动液电气性能提出的新要求，依据液态烃类电导率测定法（ASTM D4308），系统研究了润滑油基础油和添加剂对不同温度下电动汽车传动液电导率的影响。结果表明：随着温度的升高，受油品黏度降低以及载荷迁移速率增大的影响，所有测试油品的电导率均增大；润滑油基础油和抗磨、抗氧、防腐添加剂对传动系统用油的电导率影响较小；清净剂是决定油品电导率的关键组分，高碱值清净剂对电导率的影响大于中、低碱值清净剂；分散剂对油品电导率的影响仅次于清净剂，经硼磷化处理的分散剂电导率高于未经处理的分散剂。     

Suppressed atomic diffusion in flash sintering of bismuth telluride

Bi₂Te₃ materials were synthesised by the recently developed flash sintering (FS) method, and the rapid densification effect was studied. Whereas a fully densified sample can be obtained with a feeding current of 1.2 kA for 1 s, the limited heating effect reduces grain growth and atomic diffusion. Interestingly, the significant chemical reaction suppression with oxygen contaminants, which induces electron doping, has a meaningful electronic properties impact. The large negative Seebeck coefficient of ? 138.9 μV/K in the sample prepared by conventional current sintering of 773 K for 3 min, in which the oxygen diffuses into the Bi₂Te₃ phase, is significantly reduced to ? 8.5 μV/K in the FS sample, much closer to the intrinsic p-type conduction in Bi₂Te₃ raw powder. These results suggest that the limited FS heating effect may contribute to preserving the intrinsic raw powder properties in the sintered material by avoiding excess atomic diffusion and undesirable reactions.     

混砂设备中液位控制系统算法研究

在对国、内外混砂设备的控制特性进行调研和深入研究的基础上,对混砂设备的液位控制系统对象特性进行了分析,建立了相应的数学模型,并提出相应的控制方案,以模糊PID的复合控制方法来改进控制效果。根据室内和工业测试,该算法取得了预期效果。     

Effect of the Inside Placement of Electrically Conductive Beads on Electric Field Uniformity in a Microwave Applicator

Non-uniform heating is a major issue in microwave applications, mainly due to inherently uneven distribution of electromagnetic energy in the microwave applicator. In this work, our aim is to improve electric field distribution uniformity by utilizing microwave reflection from electrically conductive beads placed in the microwave oven. The effects of position, size, and number of electrically conductive beads on the electric field distribution were numerically investigated, and validated through water-load experiments in the cavity. It is found that uniform electric field distribution was realized to some extent by appropriate placement of electrically conductive beads; meanwhile, average electric field intensity in the microwave oven was increased.     

浅谈矿热炉炉盖内衬结构的施工对比

通过对矿热炉炉盖内衬结构的3种施工模式进行对比,提出了炉盖内衬采用轻质浇注料与重质浇注料分层浇注模式的优点,力求达到改善和延长炉盖使用寿命,提高矿热炉冶炼水平,降低热损失,提高经济效益。     

Effect of nanoparticle surface functionality on microdomain orientation in block copolymer thin films under electric field

The electric field induced microdomain orientations has been an interesting research topic. In this article, the effect of nanoparticle surface functionality on microdomain alignments in block copolymer/nanoparticle hybrid thin films was investigated with transmission electron microscopy experiments. The presence of gold nanoparticles influenced the microdomain orientation behaviors of block copolymer/nanoparticle thin films. The possibility for complete alignment normal to the substrate was illustrated by controlling electric field strength, concentration, and surface ligands of nanoparticles. This work provides basic and essential data to understand the properties and behaviors of emerging block copolymer/nanoparticle hybrid thin films.