Effect of operating factors on liquid–liquid mass transfer and dispersion pattern of sedimentary liquid in a mechanically stirred vessel

Liquid–liquid dispersion and mass transfer were investigated in mechanically stirred vessels without baffles by changing operation factors such as an impeller rotation speed, off-bottom clearance, volumetric liquid ratio, etc. The dispersion regime was categorized into five groups: the sedimentary liquid was kept at the vessel bottom (I), partially elevated without any collision (II), partially dispersed by colliding with the impeller bottom (III), both liquids were partially dispersed by collisions with impeller blades (III’), and the sedimentary liquid was completely dispersed (IV). The dispersion switched to I → II → III → IV with the increasing rotation speed and decreasing off-bottom clearance. The liquid–liquid mass transfer rate was significantly enhanced with the collision of the sedimentary liquid with the impeller bottom, and subsequently increased with the increasing rotation speed, volumetric liquid ratio, and vessel diameter and with the decreasing off-bottom clearance. A multiple regression analysis method was applied to determine the mass transfer rates of III and III’.     

Effects of operating and design parameters on PEFC cold start

During startup from subzero temperatures the water produced in a polymer electrolyte fuel cell (PEFC) forms ice/frost in the cathode catalyst layer (CL), blocking the oxygen transport and causing cell shutdown once all CL pores are plugged with ice. This paper describes an experimental study on the effects of operating and design parameters on PEFC cold-start capability. The amount of total product water in mg cm⁻² during startup is used as an index to quantify the cold-start capability. The newly developed isothermal cold-start protocol is used to explore the basic physics of cold start, and the effects of purge methods prior to cold start, startup temperature and current density, and the membrane thickness are shown. The experimental data also confirm the current density effect predicted earlier by a multiphase model of PEFC cold start.     

Control of threshold voltage of organic field-effect transistors by space charge polarization

We demonstrate organic field-effect transistors (OFETs) with an ion-dispersed polymer for the gate dielectrics. By applying external electric field (V_ex), the dispersed ions can migrate by electrophoresis and separated ion pairs form space charge polarization in the gate dielectrics. After V_ex was applied, the drain current is increased over 7 times and threshold voltage is decreased from − 12.9 V to − 2.9 V. The shift direction of V_th is controllable by the polarity of the V_ex. Results of ultraviolet/visible differential absorption study reveal that the active layer of OFETs is charged not only electrostatically but electrochemically with increasing the time after V_ex was applied.     

Thermal MIMO controller for setpoint regulation and load disturbance rejection

The thermal interaction problem of a multi-input multi-output (MIMO) temperature process is caused by the temperature gradient through the plant. Generally, industrial controllers are used for the decentralized control and do not use a process mathematical model. In many cases, trial-and-error tuning is required for solving the problem. The present paper introduces a MIMO thermal model and the decoupling PID control strategy. The decoupling control and its shortcomings are described from the perspective of the user. An improved strategy based on a robust observer is developed. For industrial implementation, this observer is quite simple because only the first-order model given by the decoupling model is implemented. The program code is simple for the microprocessor of a low-cost commercialized controller. In addition, a hunting rejection method based on the observer is presented. The present paper applies the method to the twin screw extruder in order to verify the effectiveness of the proposed strategy. The proposed method has been successfully to solve the interaction problem for MIMO temperature process.     

Sodium-doped carbon nitride nanotubes for efficient visible light-driven hydrogen production

Nano Research - Sodium-doped carbon nitride nanotubes (Na x -CNNTs) were prepared by a green and simple two-step method and applied in photocatalytic water splitting for the first time....     

High-Accuracy and High-Speed Calculation Method for Large-Scale Multi-layer Network Designs by Integrated Decomposition Method

A multi-layer network design, which excuses light-path design and IP routing design at the same time, has attracted great attention for IP over WDM network designs. The multi-layer network design problem can be solved by using a MILP （mixed integer linear programming） problem. However, the MILP problem for a large-scale network cannot be calculated due to the huge amount of variables used in the computation. In order to cope with this problem, a calculation method, which decomposes the original MILP problem into smaller sub-problems and obtains an approximate solution by solving these smaller MILP problems, has been proposed. However, this method has a defect that the calculation accuracy is degraded. In order to cope with this problem, we propose a novel method that solves the original MILP problem using the results of the sub-problems. We evaluate our proposed method by the computational experiments and show the effectiveness of our method.     

Measuring the sizes of nanospheres on a rough surface by using atomic force microscopy and a curvature-reconstruction method

One of the advantages of atomic force microscopy (AFM) is that it can accurately measure the heights of targets on flat substrates. It is difficult, however, to determine the shape of nanoparticles on rough surfaces. We therefore propose a curvature-reconstruction method that estimates the sizes of particles by fitting sphere curvatures acquired from raw AFM data. We evaluated this fitting estimation using 15-, 30-, and 50-nm gold nanoparticles on mica and confirmed that particle sizes could be estimated within 5% from 20% of their curvature measured using a carbon nanotube (CNT) tip. We also estimated the sizes of nanoparticles on the rough surface of dried cells and found we also can estimate the size of those particles within 5%, which is difficult when we only used the height information. The results indicate the size of nanoparticles even on rough surfaces can be measured by using our method and a CNT tip.     

Thermoelectric Property Dependence and Geometry Optimization of Peltier Current Leads Using Highly Electrically Conductive Thermoelectric Materials

Thermoelectric materials are promising candidates for use in energy-saving devices in many fields. They are also useful in superconducting applications such as those using Peltier current leads (PCLs) to reduce system heat loss. In the case of PCLs, consideration must be given to Joule heating. Furthermore, the performance of PCLs is intricately dependent on their thermoelectric properties. In addition to the figure of merit Z, consideration of the electrical conductivity is also important for the design of high-performance PCLs. In this paper, we discuss the resistivity dependence of the performance of PCLs using model parameters obtained from real devices.     

Modeling and resonance suppression control for electro-hydrostatic actuator as a two-mass resonant system

Electro-hydrostatic actuators (EHAs) possess excellent power/weight ratio and space-saving properties. However, uncertainty exists with respect to the presence of non-linear behaviors and dynamic characteristics. Servo pumps, hydraulic motors, and oil-filled pipes can be regarded as motors, loads, and springs, respectively. Hence, EHAs can be modeled as two-mass resonant systems. In this paper, we show a parameter identification method for modeling EHAs as two-mass resonant systems. Then, in order to suppress the effect of resonance, self-resonance cancellation technique is implemented. As a result, phase delay is significantly improved in the position tracking.