Recycling and Recharging of Supreme Garnet in Abrasive Waterjet Machining

Abrasive waterjet (AWJ) technology is widely used for cutting technical materials, cleaning contaminated surfaces, polishing hard-to-machine materials, etc. However, its main disadvantage is high cutting cost. Therefore, recycling and recharging abrasives used in the AWJ cutting process have been subject to many studies. This chapter presents a study on the recycling and recharging of Supreme garnet (or IMC garnet) in abrasive waterjet machining. In this study, the reusability of the recycled and recharged garnet was explored. Also, the cutting performance and the cutting quality of the recycled and recharged abrasive were investigated. Finally, the optimum particle size for recycling and recharging was found

QoS-Aware Utility-Based Resource Allocation in Mixed-Traffic Multi-User OFDM Systems

This paper deals with the joint subcarrier and power allocation problem in a downlink multi-user orthogonal frequency division multiplexing system subject to user delay and minimum rate quality-of-service (QoS) requirements over a frequency-selective multi-carrier fading channel. We aim to maximize the utility-pricing function, formulated as the difference between the achieved spectral efficiency and the associated linear cost function of transmit power scaled by a system-dependent parameter. For a homogeneous system, we show that the joint resource allocation can be broken down into sequential problems while retaining the optimality. Specifically, the optimal solution is obtained by first assigning each subcarrier to the user with the best channel gain. Subsequently, the transmit power for each subcarrier is adapted according to water-filling policy if the global optimum is feasible, else it is given by a nonwater-filling power adaptation. For a heterogeneous system, an optimal solution needs exhaustive search and hence, we resort to two reduced-complexity sub-optimal algorithms. Algorithm-I is a simple extension of the aforementioned optimal algorithm developed for a homogeneous system, while Algorithm-II further takes into consideration the heterogeneity in user QoS requirements for performance enhancement. Simulation results reveal the impacts of user QoS requirements, number of subcarriers and number of users on the system transmit power

Influence of Adhesion Layers on the Surface Morphology of Platinum-based Bottom Electrodes for Pb(Zr,Ti)O3 Thin Films

A thin adhesion layer is required to glue Pt bottom electrodes of ferroelectric Pb(Zr,Ti)O3 thin films to a SiO2/Si wafer. Here we report the effect of adhesion layers, Ti and TiO2, on the crystalline structure and surface properties of Pt electrode. The results show the hillock formation is observed for the case of Ti glue layer, while the surface of Pt layer is flat and uniform with TiO2 layer used instead. The crystallization in PZT thin films on Pt/TiO2/SiO3/Si substrate is investigated during post-deposition annealing. The perovskite phase is completely formed in the film annealed at 650oC for one hour

Informações contábeis e retornos de ações no mercado de ações do Vietnã: abordagem de aprendizado de máquina

This paper studies the relationship between accounting information reflected in financial statements and stock return in Vietnam Stock Market. The authors propose a research model to define the relationship. Besides, machine learning algorithms are used in researching and forecasting, with data obtained from observed firms during the period from 2009 to 2020. Research results show that gradient boosting algorithm has the best self-reporting performance and finan-cial ratios also have great impact on stock returns, including operating income growth, stock earnings volatility, dividend yield, earnings before tax-to-equity ratio, cash holding ratio, and accrual quality. Based on the research results, the authors make some recommendations for investors, firms, and policy makers.Este artículo estudia la relación entre la información contable reflejada en los estados financieros y el rendimiento de las acciones en el mercado de valores de Vietnam. Se propone un modelo de investigación para definir la relación. Además, los algoritmos de aprendizaje automático se utilizan en la investigación y la previsión, con datos obtenidos de empresas observadas durante el período de 2009 a 2020. Los resultados de la investigación muestran que el algoritmo gradient boosting tiene el mejor rendimiento de autoinforme y los índices financieros también tienen un gran impacto en la rentabilidad de las acciones, al incluir el crecimiento de los ingresos operativos, la volatilidad de las ganancias de las acciones, el rendimiento de los dividendos, la relación entre las ganancias antes de impuestos y el capital, la relación de tenencia de efectivo, y la calidad de la acumulación. Sobre la base de los resultados de la investigación, se hacen algunas recomendaciones para inversionistas, empresas y formuladores de políticas.Este artigo estuda a relação entre as informações contábeis refletidas nas demonstrações financeiras e o retorno das ações no mercado de ações do Vietnã. Os autores propõem um modelo de pesquisa para definir a relação. Além disso, algoritmos de aprendizado de máquina são usados em pesquisas e previsões, com dados obtidos de empresas observadas durante o período de 2009 a 2020. Os resultados da pesquisa mostram que o algoritmo gradient boosting tem o melhor desempenho de autorrelato e os índices financeiros também têm grande impacto nos retornos das ações, incluindo crescimento da receita operacional, volatilidade do lucro das ações, rendimento de dividendos, lucro antes do índice de impostos sobre o patrimônio líquido, índice de retenção de caixa e qualidade de acumulação. Com base nos resultados da pesquisa, os autores fazem algumas recomendações para investidores, empresas e formuladores de políticas

Estimating Disturbance Torque Effects on the Stability and Control Performance of Two-Axis Gimbal Systems

Introduction. Two-axis gimbal systems are applied for stabilizing and controlling the line of sight (LOS) of an optical or imaging system mounted on a moving vehicle. Gimbal systems are intended to isolate various disturbance torques and control the LOS toward the direction of a target. Two-axis gimbals can be of two main types, namely Yaw-Pitch and Swing-Roll type. In this article, we focus on investigating mathematical models of two-axis gimbals, which describe the impact of cross-disturbance torques on their stability and control performance. Simulations were conducted to compare advantages and disadvantages of the two types of two-axis gimbals.Aim. To study mathematical models describing the impact of cross-disturbance torques on the stability and control performance of two-axis gimbals.Materials and methods. Mathematical models of two-axis gimbal systems were synthesized by the Lagrange method. The operation of two-axis gimbal systems was simulated in the Matlab-Simulink environment. Results. Mathematical models and structural diagrams of the synthesized Yaw-Pitch and Swing-Roll gimbals were obtained. The conducted simulations of typical cases revealed different cross-disturbance effects.Conclusion. Motion equations for Swing-Roll and Yaw-Pitch gimbals were derived using similar methodology. The impact of cross-disturbance torques on gimbal systems was evaluated. The obtained results form a basis for selecting an optimal structure of tracking systems meeting the desired characteristics.Introduction. Two-axis gimbal systems are applied for stabilizing and controlling the line of sight (LOS) of an optical or imaging system mounted on a moving vehicle. Gimbal systems are intended to isolate various disturbance torques and control the LOS toward the direction of a target. Two-axis gimbals can be of two main types, namely Yaw-Pitch and Swing-Roll type. In this article, we focus on investigating mathematical models of two-axis gimbals, which describe the impact of cross-disturbance torques on their stability and control performance. Simulations were conducted to compare advantages and disadvantages of the two types of two-axis gimbals.Aim. To study mathematical models describing the impact of cross-disturbance torques on the stability and control performance of two-axis gimbals.Materials and methods. Mathematical models of two-axis gimbal systems were synthesized by the Lagrange method. The operation of two-axis gimbal systems was simulated in the Matlab-Simulink environment. Results. Mathematical models and structural diagrams of the synthesized Yaw-Pitch and Swing-Roll gimbals were obtained. The conducted simulations of typical cases revealed different cross-disturbance effects.Conclusion. Motion equations for Swing-Roll and Yaw-Pitch gimbals were derived using similar methodology. The impact of cross-disturbance torques on gimbal systems was evaluated. The obtained results form a basis for selecting an optimal structure of tracking systems meeting the desired characteristics

Hierarchical Motion Planning and Offline Robust Model Predictive Control for Autonomous Vehicles

Driving vehicles in complex scenarios under harsh conditions is the biggest challenge for autonomous vehicles (AVs). To address this issue, we propose hierarchical motion planning and robust control strategy using the front-active steering system in complex scenarios with various slippery road adhesion coefficients while considering vehicle uncertain parameters. Behaviors of human vehicles (HVs) are considered and modeled in the form of a car-following model via the Intelligent Driver Model (IDM). Then, in the upper layer, the motion planner first generates an optimal trajectory by using the artificial potential field (APF) algorithm to formulate any surrounding objects, e.g., road marks, boundaries, and static/dynamic obstacles. To track the generated optimal trajectory, in the lower layer, an offline-constrained output feedback robust model predictive control (RMPC) is employed for the linear parameter varying (LPV) system by applying linear matrix inequality (LMI) optimization method that ensures the robustness against the model parameter uncertainties. Furthermore, by augmenting the system model, our proposed approach, called offline RMPC, achieves outstanding efficiency compared to three existing RMPC approaches, e.g., offset-offline RMPC, online RMPC, and offline RMPC without an augmented model (offline RMPC w/o AM), in both improving computing time and reducing input vibrations.Comment: 6 pages, 9 illustrations, Accepted for publication in American Control Conference (ACC) 202

Improvement of Tuning Fork Gyroscope Drive-mode Oscillation Matched using a Differential Driving Suspension Frame

This paper presents a novel design of a vibration tuning fork gyroscope (TFG) based on a differential driving suspension coupling spring between two gyroscopes. The proposed TFG is equivalent to a transistor differential amplifier circuit. The mechanical vibrations of driving frames are, therefore, well matched. The matching level depends on stiffness of spring. When three various TFG structures respond to differential stiffness of spring, their the driving frame mechanical vibration is well matched in case the input excitation driving differential phase is less than 3.5°, 2.5°, and 4°, respectively. The fabricated tuning fork gyroscope linearly operates in the range from -200 to +200 degree/s with the resolution of about 0.45 mV/degree/s