Generation of uniform-size droplets by multistep hydrodynamic droplet division in microfluidic circuits

A microfluidic system is presented to generate multiple daughter droplets from a mother droplet, by the multistep hydrodynamic division of the mother droplet at multiple branch points in a microchannel. A microchannel network designed based on the resistive circuit model enables us to control the distribution ratio of the flow rate, which dominates the division ratios of the mother droplets. We successfully generated up to 15 daughter droplets from a mother droplet with a variation in diameter of less than 2%. In addition, we examined factors affecting the division ratio, including the average fluid velocity, interfacial tension, fluid viscosity, and the distribution ratio of volumetric flow rates at a branch point. Additionally, we actively controlled the volume of the mother droplets and examined its influence on the size of the daughter droplets, demonstrating that the size of the daughter droplets was not significantly influenced by the volume of the mother droplet when the distribution ratio was properly controlled. The presented system for controlling droplet division would be available as an innovative means for preparing monodisperse emulsions from polydisperse emulsions, as well as a technique for making a microfluidic dispenser for digital microfluidics to analyze the droplet compositions.     

动力学在线更新的人和机器人握手智能控制器

为实现人和机器人握手运动的同步, 本文提出了一种基于动力学在线更新的智能控制器. 首先, 建立了人和机器人握手的仿真模型; 然后对智能控制器中有任意吸引子的动力学系统进行多项式近似设计和在线更新设计,使其具备自振动特性和输入输出同步特性; 同时通过忘却系数和负荷系数, 输入输出同步程度能实现参数可调; 最后, 将该智能控制器用于人和机器人握手的控制中, 仿真结果表明了该智能控制器设计的有效性.     

Torsional Oscillator Experiments with High Stability and Reproducibility

We report experiments of the torsional oscillator to observe the superfluid transition in ⁴ He films in porous glass (the pore diameter is 1m). Stability and reproducibility of the oscillator, which quite often is problematic in previous experiments, is essential for a quantitative analysis of observations in different conditions. It follows that the friction of the superfluid films and the energy dissipation of the solid films are derived from comparisons of measurements for different film thickness.     

Magnetic order in thet-J andt-t′-J models

The magnetic structure of thet-J andt-t-J models are investigated. Assuming that the ground state has magnetic long-range order, we calculated the energy of some magnetically ordered states using a simple transformation of the models and theS approximation. The result shows that the Néel state is destroyed by doped holes unless the next-nearest neighbor hoppingt is finite, and that the ferromagnetic phase appears at moderate doping. Mean field analysis shows that the intermediate phase between the Néel and ferromagnetic phase has spiral spin order, although the spiral phase is shown to be unstable against density fluctuations.On leave from the Department of Materials Science, Faculty of Science, Hiroshima University, Higashi-Hiroshima 724, Japan.     

A polydimethylsiloxane diaphragm integrated with a sputtered thin film NdFeB magnet

Microsystem Technologies - In this paper we propose a MEMS fabrication process that enables a polydimethylsiloxane (PDMS) diaphragm to be integrated with a sputtered thin film permanent magnet...     

Static thrust analysis of a cylindrical moving-core linear oscillatory actuator

This paper considers materials for the movers, the volume ratio of the stator and of the mover, and the structure of the mover in a cylindrical moving iron-type linear oscillatory actuator (LOA) having a permanent magnet. As a result, we obtain the following:

• (1) the static thrust characteristics are evaluated on two movers: movers P and S are made of a permendur and a stainless steel, respectively. It is clarified that the static thrust of the mover P is 30 percent larger than that of the mover S;
• (2) it is suggested that the structure of the mover P should be improved to eliminate a “lump” in the static thrust-displacement curve due to the step on the mover, and which disturbs the smooth motion of the LOA.

     

Dielectric properties of hydrothermally grown gallium orthophosphate single crystals

GaPO₄ single crystals of the low-temperature form were hydrothermally grown in 4M H₃PO₄ solution at 180 ° C. Single crystals 5.0×5.2×3.7mm³ in size could be grown in a silica glass vessel of 10 mm inner diameter. The dielectric properties of grown crystals were measured with the electric field parallel (E c) and perpendicular (E c) to thec-axis. The values of dielectric constant (ie2800-01) ofE c andE c are about 10.3 and 7.8, respectively, at frequencies from 10 kHz to 1 MHz, and these are nearly independent of frequency at room temperature. However, these values increase with temperature in the temperature range about 310 to 500 K and in the frequency region below 1 MHz. Dielectric loss (ie2800-02) increases with increasing temperature at around 300 K (E c) and 310 K (E c). From the log (conductivity) against 1/T plot in the intrinsic region at higher temperatures, the values of activation energy (E) for conduction are calculated to be about 0.17 and 0.33eV, forE c andE c, respectively.     

Martensitic stabilization and defects induced by deformation in TiNi shape memory alloys

Martensitic stabilization caused by deformation in a TiNi shape memory alloy was studied.Special attention was paid to the deformed microstructures to identify the cause of martensitic stabilization.Martensitic stabilization was demonstrated by differential scanning calorimetry for the tensioned TiNi shape memory alloy.Transmission electron microscopy revealed that antiphase boundaries were formed because of the fourfold dissociation of [110]B19' super lattice dislocations and were preserved after reverse t...     

Friction and wear of carbon nanohorn-containing polyimide composites

Polyimide (PI)-based composites containing single-wall carbon nanohorn aggregate (NH) were fabricated using the spark plasma sintering (SPS) process. For comparison, composites with carbon nanotube (NT) and traditional graphite (Gr) were also fabricated. The NH was produced using CO₂ laser vaporization and a graphite target and the NT was produced by a chemical synthesis method. We evaluated the friction and wear properties of the PI-based composites with a reciprocating friction tester in air using an AISI 304 mating ball. NH drastically decreased the wear of PI-based composites; the specific wear rate of composite with NH of only 5 wt% was of the order of 10⁻⁸ mm³/Nm, which was two orders of magnitude less than that of PI alone. The wear reduction ability of NT seemed to be slightly inferior to that of NH, although it was considerably better than that of Gr. NH and NT lowered the friction of composites. The friction coefficient of composite with 10 wt% NH was less than 0.25, although it was slightly higher than that of composite with 10 wt% Gr. There was no clear difference in the friction reduction effect of NH and NT. The further addition of Gr to composites with NH or NT rather deteriorated the antiwear property of composites, although the friction coefficient was slightly reduced. The transferred materials existed on the friction surface of the mating ball, sliding against composites with three types of carbon filler. These transferred materials seemed to correlate with the low friction and wear properties of composites.