Reactive control of overall power consumption in flexible manufacturing systems scheduling: A Potential Fields model

In recent years, designing “energy-aware manufacturing scheduling and control systems” has become more and more complex due to the increasing volatility and unpredictability of energy availability, supply and cost, and thus requires the integration of highly reactive behavior in control laws. The aim of this paper is to propose a Potential Fields-based flexible manufacturing control system that can dynamically allocate and route products to production resources to minimize the total production time. This control system simultaneously optimizes resource energy consumption by limiting energy wastage through the real-time control of resource states, and by dynamically controlling the overall power consumption taking the limited availability of energy into consideration. The Potential Fields-based control model was proposed in two stages. First, a mechanism was proposed to switch resources on/off reactively depending on the situation of the flexible manufacturing system (FMS) to reduce energy wastage. Second, while minimizing wastage, overall power consumption control was introduced in order to remain under a dynamically determined energy threshold. The effectiveness of the control model was studied in simulation with several scenarios for reducing energy wastage and controlling overall consumption. Experiments were then performed in a real FMS to prove the feasibility of the model. The superiority of the proposition is its high reactivity to manage production in real-time despite unexpected restrictions in the amount of energy available. After providing the limitations of the work, the conclusions and prospects are presented.     

Modeling,tracking, vibration and balance control of an underactuated mobile manipulator (UMM)

This paper presents an underactuated mobile manipulator (UMM) and focuses on solving modeling, tracking, and vibration- and balance-control problems. Although the study has been directed at warehousing applications, the developed techniques are general and can be applied to other applications. The derivation of equations of motion of the UMM, disturbance analysis, and model validation are investigated to reveal the actual system dynamics. Additionally, a simple but effective strategy is also developed to solve the equilibrium point and balance problem. Based on the dynamic model, two control architectures are proposed: Model Predictive Control (MPC) and MPC+Proportional-Integral (PI) with integral actions, respectively, and they can also be applied to other robotic systems. Compared to other MPC-based control strategies, the proposed controllers require less effort to implement in practice. Finally, simulations, experiments, and robustness verification are conducted and discussed, and the results are satisfactory.     

About the gauge conditions arising in Finite Element magnetostatic problems

In this paper, we deal with some magnetostatic models considered in vector potential formulations and solved by a Finite Element solver. In order to ensure the uniqueness of the solution, a gauge condition has to be imposed, and several possibilities occur. Moreover, the source term has to be correctly defined to ensure a physically admissible solution. We show the equivalence between some of these choices for several kinds of boundary conditions. Moreover, we highlight their characteristic behaviors on some numerical benchmarks to illustrate our theoretical results.     

Investigation of pitting corrosion monitoring using field signature method

The field signature method (FSM) is a nondestructive testing (NDT) method based on the potential drop (PD) technique and has been applied to online metal pipe corrosion monitoring for nearly three decades. The many advantages and benefits of the method have been reported in a number of studies, but few have reported on its limitations or shortcomings. However, the detection accuracy for pitting corrosion in FSM is very low. In this paper, the reasons for the low pitting corrosion detection accuracy of FSM were analyzed and it was found that different corrosion pits, which have different sizes, depths or positions, generally have differing influences on the potentials of nearby electrode pairs. Therefore, a new method using a subdivided resistor network to assess pitting corrosion is proposed and verified. When compared with the traditional method, the most important parameter, namely the pitting corrosion depth detection accuracy, can be significantly improved.     

In situ electrodeposition of nickel cobalt selenides on FTO as an efficient counter electrode for dye-sensitized solar cells

Construction of transition metal selenides with high electrocatalytic performance is of significant importance, but it is still a challenge to develop the corresponding counter electrodes (CEs) by an electrodeposition technique. In the present work, nickel cobalt selenide (Ni_xCo_ySe) films are prepared in situ on fluorine-doped tin oxide (FTO) glasses through a potential reversal electrodeposition technique. The morphology and electronic structure of Ni_xCo_ySe films can be tuned by controlling the Ni/Co molar ratio in electroplating solution. Specially, Ni_xCo_ySe-6 film (the Ni/Co molar ratio of 1:1) with the optimized interaction between the Ni and Co elements displays numerous particles composed of sheets attached with nanocrystals, resulting in the more electrocatalytic active sites. Benefiting from the unique morphology and optimized synergistic effect, Ni_xCo_ySe-6 CE exhibits superior electrocatalytic activity for the triiodide reduction. Then, the dye-sensitized solar cell (DSC) fabricated by Ni_xCo_ySe-6 CE has demonstrated a power conversion efficiency (PCE) over 7.40%, which is higher than that of platinum (Pt)-based device (6.32%). Furthermore, Ni_xCo_ySe-6 array CE is also prepared by using polystyrene array as template. The PCE of the DSC with Ni_xCo_ySe-6 array CE reaches its maximum value of 7.64% and 20.9% larger than that of Pt-based device.     

Mathematical model of five-level ac/dc converter in abc reference frame

This paper proposes a mathematical model for three-phase multilevel diode clamped ac/dc converter (DCC) in abc-reference frame, in order to study dynamic responses and stability of the system, where multilevel converters are employed. An attempt is made to model the converter adopting 5-level DCC and can be easily extended to DCC with any number of levels. The converter output and dc capacitor voltages are expressed in terms of input source currents and switching functions; which are basic inputs provided to a converter. Connection and capacitor currents of the converter have been analyzed. The effectiveness of the proposed mathematical model is verified by the computer simulations and experimental results. The obtained mathematical model has been validated with the physical converter model in MATLAB/Simulink environment and the prototype model using dSPACE DS under closed loop control system. The developed mathematical model equations are able to represent the physical converter with similar characteristics.     

Induced changes of Pt/C in activity and durability through heat-treatment for oxygen reduction reaction in acidic medium

In this study, the Pt/C catalysts systematically heat-treated from 200 to 800 °C are characterized physically and chemically to investigate the induced properties for the activity and durability. The relative intensity of Pt⁰ increases from approximately 40 to 70% and the mean Pt particle size mildly increases as the temperature increases from 200 to 600 °C. However, the Pt/C heat-treated at 800 °C sharply increases and shows poor Pt particle size distribution resulting in the poor electrochemical performance. Catalysts prepared at between 200 and 600 °C exhibit similar electrocatalytic properties. Durability tests using sweeping potential between 0.6 and 1.0 V show that the durability of catalysts heat-treated at 400–600 °C significantly increases since the Pt oxide can be readily dissolved under potential cycling as compared to the Pt⁰. We strongly believe that the induced changes by heat-treatment play an important role in the challenges for fuel cells.     

水泥电杆模具翘尾问题研究

水泥电杆在离心成型过程中,常遇到模具震动的现象。本文讨论了模具近梢端部分翘起引起模具震动的情况。提出了以限制翘起度来防止模具震动。     

Glycolipids improve lutein bioavailability and accumulation in eyes in mice

Intestinal carotenoid absorption is greatly affected by dietary factors. In this study, it was hypothesized that lipids with varying functional groups may influence differentially lutein bioavailability. Hence, the influence of glyco‐, phospho‐, neutral, crude (mixture of lipids) lipids, or mixed micelles (control) on the percent lutein micellarization in vitro and its postprandial plasma, liver, and eye response in mice were investigated. Results show that the percent micellarization of lutein with crude lipids and glycolipids were higher (91.4 and 45.7%) than control, while no significant difference was found between phospho‐ and neutral lipids. The mean plasma response of lutein was higher for crude‐ (6 times), glyco‐ (3 times), phospho‐ (2.7 times), and neutral (2 times) lipid than control (12.4 ± 1.18 nmol/mL 8 h^?1) group. Lutein levels (pmol/g) in liver were higher in crude (7.4 ± 1) and phospho‐ (3.6 ± 0.8) lipid groups while in eyes it was higher in glyco‐ (54.0) and neutral (21.2) lipid groups than control. The influential effect of glyco‐ and phospholipids may be due to smaller micellar size (glyco‐upto 3.43 µm, phospho‐ upto 5.78 µm) than the neutral lipids (upto 66 µm). Ingestion of lutein with glycolipid or phospholipids may improve lutein bioavailability. Practical applications: The findings of the present study will be useful in nutritional and biomedical applications for feeding lutein with specific lipid combinations to achieve enhanced lutein absorption. Specifically, feeding diet/emulsion with lutein and glyco‐ and phospholipid combination may reduce the risk of macular degeneration, owing to the influential effect of these lipids on intestinal absorption of lutein.     

Modeling of the mixed potential in hydrogen peroxide-based fuel cells

A one-dimensional mathematical model is developed for the study of the mixed potential associated with the hydrogen peroxide oxidation reaction (HPOR) at the cathode of hydrogen peroxide-based fuel cells. The complicated physicochemical processes, including mass transport, charge transport, and three simultaneous electrochemical reactions (the hydrogen peroxide reduction, hydrogen peroxide oxidation, and oxygen reduction reactions) are considered. The model is experimentally validated and shows good agreement with the literature experimental data. The model is then applied to the study of the mixed potential by varying the current density. It is found that the largest potential loss due to the HPOR occurs under the open-circuit condition (OCC), and the potential loss decreases with the superficial current density. In addition, the numerical results suggest that under the OCC, an increase in the concentrations of hydrogen peroxide and H⁺ ions leads to a decrease in the potential loss, but an increase in the hydrogen peroxide decomposition rate and the oxygen evolution rate.