Temperature dependence of giant magneto-resistance in PtMn- and Fe2O3-based specular spin valves

Temperature dependence of the giant magneto-resistance (MR) was measured for spin valves with and without nano-oxide layer (NOL). In spin valves with NOL, the MR ratio increased more remarkably on lowering the temperature than in those without NOL. The temperature dependence of MR ratio and that of the resistivity were explained by using two-current model. The MR ratio enhanced with NOL is attributed to the increase of the mean free path of up-spin electrons.     

一种新的“L”型脉管结构在四阀型脉管制冷机中的试验研究

基于简化冷端结构的目的考虑,该文提出了一种“L”型脉管结构取代了通常的“I”型直脉管结构;并在脉管热端采用两个小孔阀分别进行控制脉管热端的进排气量,并对此结构使用有阀氦压缩机驱动,进行初步的试验研究,样机在频率为2.5Hz时,获得72K的冷头最低温度,针对此试验结果进行分析,给出了目前试验样机所存在的问题,提出了进一步改善的方法。     

Spin valve effect and negative tunnel magnetoresistance in a quantum dot transistor

We study the spin polarized transport through a quantum dot transistor. It is shown that the interplay of large Coulomb interaction and optically induced spin accumulation gives rise to the spin valve effect over a range of bias. We also find negative tunnel magnetoresistance for system with ferromagnetic electrodes.     

The Immersed Structural Potential Method for haemodynamic applications

In this paper, a new fluid–structure interaction immersed computational methodology, based upon the original Immersed Boundary Method (IBM) [1] is outlined with the final aim of modelling cardiovascular phenomena, specifically, heart valve related problems. The principal characteristic of such immersed techniques is the representation of any deformable or rigid body immersed within an incompressible viscous flow field as a momentum forcing source in the Navier–Stokes equations. A number of shortcomings within the immersed formulation still require further investigation and improvement, including the excessive numerical diffusion caused by the interpolation/spreading process, the need to include realistic viscoelastic composite constitutive models describing more accurately the nature of cardiovascular tissues and also the need to capture more effectively stresses developed at the fluid–structure interface. By following the same philosophy as the original IBM, a more sophisticated formulation is derived in this paper, the “Immersed Structural Potential Method (ISPM)”. The method introduced presents an alternative approach to compute the equivalent fluid–structure interaction forces at the fluid mesh, accounts for a sophisticated viscoelastic fibre-reinforced constitutive model to better describe the mechanics of cardiovascular tissues and utilises a novel time-integration methodology for the computation of the deformation gradient tensor which ensures compliance with the incompressibility constraint. A series of numerical examples will be presented in order to demonstrate the robustness and applicability of this new methodology.     

TaN underlayers for spin valves deposited directly on top of Si substrates

TaN underlayers for spin valves were studied, which were deposited directly on top of Si substrates. The experimental results obtained with the TaN underlayer were compared with those obtained with other (Ta, Mo, and MoN) underlayers. The spin valve structure was Si/Underlayer(tÅ)/NiFe(21 Å)/CoFe(28 Å)/Cu(22 Å)/CoFe(18 Å)/IrMn(65 Å)/Ta(25 Å). The TaN underlayer for a spin valve element exhibited good adhesion to the Si substrate. The XRD patterns of the annealed TaN on bare Si substrate at 900 °C showed no Ta silicide phases, which suggests that the TaN layer may also be used as a diffusion barrier between Si substrate and the ensuing spin valve active layers, as well as an underlayer. A spin valve element having TaN underlayer deposited directly on top of a Si substrate showed a high MR ratio of about 8.3% after annealing at 200 °C. It is concluded that it is advantageous to use a TaN underlayer if one wants to fabricate spin valve elements directly on top of Si substrates.     

电子膨胀阀应用于低温陈列柜制冷系统的节能研究

与热力膨胀阀相比,电子膨胀阀应用于陈列柜制冷系统,可以更为精确地控制其柜温及过热度。为进一步减小低温陈列柜制冷系统能耗,文中提出通过改变电子膨胀阀脉冲信号的控制策略以达到节能的目的。通过试验证明:与热力膨胀阀相比,可节能25%;同时可减小系统过热度,提高低温陈列柜制冷系统温度特性。为电子膨胀阀在低温制冷陈列柜中的应用提供参考依据。     

基于直线电机的电炉电极控制系统的研究

电炉电极调节器是电炉的核心控制系统。目前吉林铁合金八分厂的10T电炉电极升降系统采用手动控制。针对此问题提出了一种采用直线步进电机控制数字阀调节液压系统位置的方法,使现有系统可以实现电极升降的自动控制,同时对直线步进电机的控制使用Fuzzy-PID的控制方法,达到精密定位控制的目的。阐述和分析了数字阀控制液压系统升降可行性和稳定性。并通过实验验证了该系统调节具有精度高,响应快等优点。     

A valve‐based microfluidic device for on‐chip single cell treatments

Assays toward single‐cell analysis have attracted the attention in biological and biomedical researches to reveal cellular mechanisms as well as heterogeneity. Yet nowadays microfluidic devices for single‐cell analysis have several drawbacks: some would cause cell damage due to the hydraulic forces directly acting on cells, while others could not implement biological assays since they could not immobilize cells while manipulating the reagents at the same time. In this work, we presented a two‐layer pneumatic valve‐based platform to implement cell immobilization and treatment on‐chip simultaneously, and cells after treatment could be collected non‐destructively for further analysis. Target cells could be encapsulated in sodium alginate droplets which solidified into hydrogel when reacted with Ca²⁺. The size of hydrogel beads could be precisely controlled by modulating flow rates of continuous/disperse phases. While regulating fluid resistance between the main channel and passages by the integrated pneumatic valves, on‐chip capture and release of hydrogel beads was implemented. As a proof of concept for on‐chip single‐cell treatments, we showed cellular live/dead staining based on our devices. This method would have potential in single cell manipulation for biochemical cellular assays.     

Effects of the particle Stokes number on wind turbine airfoil erosion

Under natural conditions, wind turbines are inevitably eroded by the action of sand-wind flow. To further investigate the effects of dust drift on the erosion of the wind turbine blades in sand-wind environments, the effects of the wind velocity, particle diameter, and particle density on the erosion of wind turbine airfoils are studied, and the effects of the particle Stokes number on the airfoil erosion are discussed. The results show that, when the angle of attack(AOA) is 6.1°, there will be no erosion on the airfoil surface if the particle Stokes number is lower than 0.013 5, whereas erosion will occur if the particle Stokes number is higher than 0.015 1. Therefore, there exists a critical range for the particle Stokes number. When the particle Stokes number is higher than the maximum value in the critical range, airfoil erosion will occur. The result is further confirmed by changing the particle diameter, particle density, and inflow speed. It is shown that the erosion area on the airfoil and the maximum erosion rate are almost equal under the same particle Stokes number and AOA. The extent of airfoil erosion increases when the particle Stokes number increases, and the critical particle Stokes number increases when the AOA increases. Moreover, the geometric shape of the airfoil pressure surface greatly affects the airfoil erosion, especially at the curvature near the leading edge.