Influence of Additive Gas on Electrical and Optical Characteristics of Non-equilibrium Atmospheric Pressure Argon Plasma Jet

Electrical and optical properties of an argon plasma jet were characterized. In particular, effects of an additive gas, namely nitrogen or oxygen, on these prop...     

Terahertz Active Metamaterials Based on Stacked Closed‐Ring Resonator Arrays

Metamaterials, which can show novel optical functionalities beyond conventional optics, have been actively studied in recent years. As one of approaches to add tunability on resonant characteristics of metamaterials, slightly shifting relative position of stacked metamaterials or metasurfaces has been reported. In this study, based on numerical simulation we have designed stacked closed‐ring resonator (CRR) arrays that show relatively large spectral shift with a small lateral shift of the stacked layers in terahertz (THz) range. We also show that changing dielectric constant of the dielectric media between CRR arrays is also effective to obtain large spectral shift of the resonant responses. Our findings may be utilized to develop novel type of THz active devices and also sensing devices.     

High-Density Polyethylene(HDPE) Surface Treatment Using an RF Capacitive Atmospheric Pressure Cold Ar Plasma Jet

In this study,a high-density polyethylene（HDPE,5-mm-thick,0.95 g/cm3） surface was treated using an RF capacitive atmospheric pressure cold Ar plasma jet.By using this Ar plasma jet,a hydrophilic HDPE surface was formed during the plasma treatment.In particular, the effects of an additive gas（N₂ or O2） on the HDPE surface treatment were investigated in detail.It was shown that the addition of N2 or O2 gas had an important influence on the HDPE surface treatment.Compared to pure Ar plasma treatment,a lower value of water contact angle （WCA） was obtained when a trace of N2 or O2 gas was added.It was also found that besides the quantities of active species in the plasma jet,the treatment temperature played an important role in the HDPE surface treatment.This is because surface molecular motion is not negligible when the treatment temperature is close to the melting point of the polymer.     

Estimates for a measure of stability robustness via a Lyapunov matrix equation

The upper and lower bounds of an existing measure for stability robustness are obtained in terms of the solution to a Lyapunov matrix equation for nominal systems. This measure is exact, in the sense that it gives a necessary and sufficient condition for the stability of perturbed systems for a certain class of perturbations. The results enable us to assess the measure using the solution to a Lyapunov equation.     

Spline function approach to digital signal processing

Models of digital signal processing are built on the signal spaces composed of spline functions. It is revealed that the models include and generalize the ideal model on the band-limited signal space, and the conventional model used in practice, with a zero-order or a first-order hold circuit. The models can be implemented accurately using real circuits so far as they are not identical with the ideal model because a spline function can be generated as a piecewise polynomial. Thus the models make it possible to treat signal processing systems which exist between the conventional ideal model and the conventional model used in practice, in design through implementation.     

Further comments on ‘A simple criterion for stability of linear discrete systems’

Some additional comments are offered on the stability condition for linear discrete systems in Dabke (1983). It is pointed out that the condition can be naturally extended to cover time-varying systems.     

高温加压气流床内生物质气化特性的实验研究

在15～20 kg/h规模的沉降式加压气化实验装置上,实验研究了高温条件下,不同O/C摩尔比对生物质气化特性的影响,并根据实验气化炉的边界条件,建立了相应的气化模型.模型计算结果与实验结果吻合较好,模型能够很好的预测气化参数对生物质气流床气化特性的影响.研究结果袁明:在气化还原反应区,高温有利于气化反应向吸热方向进行;O/C比在1.0～2.0范围内,随O/C比的增加,CO、H2均呈现先增加后减小的趋势,可燃气体成分(CH4 H2 CO)占总合成气的50%左右;部分燃烧反应区温度在1600 K以上时,碳转化率大于90%,冷煤气效率达到50%左右.     

Properties of hydrogels synthesized by freezing and thawing aqueous polyvinyl alcohol solutions and their applications

The hydrogel synthesized by freezing a polyvinyl alcohol (PVA) aqueous solution and thawing it slowly has high water content, excellent mechanical properties of high tensile strength, elongation and good shape recovery by elasticity. The PVA used had a degree of polymerization of 2500 and a degree of saponification of 99.5 mol%. The solution was obtained by dissolving 7.5 g of PVA in 80 g of water, this was frozen at –50°C for 3 h and then warmed up to room temperature over 10h. This freezing–thawing process was repeated once again and a hydrogel was synthesized. The hydrogel had a water content of about 90 wt%. Its tensile strength was 0.6 MPa and the elongation at break was 130%. The shape of the hydrogel which was deformed by an external force recovered in a short time when it was released from the force. This recovery had good persistence and repeatability. Applying these properties a strain sensor and a gas pressure sensor were tested. Furthermore, a PVA hydrogel rod containing polyacrylic acid was used as a bending actuator. This hydrogel had the ability to deform when direct current was applied.     

AZ31镁合金板冷拉深变形特点

在室温条件下,对最常用的镁合金AZ31板材在经过不同的退火热处理后进行冷拉深试验研究中,借助有限元数值模拟技术对其拉深变形过程进行分析,探索其冷拉深变形特点及规律,并合理解释在拉深过程中的载荷特点、破裂形态、极限拉深比、各向异性现象、厚度分布规律以及退火工艺条件、模具结构及尺寸对它们的影响规律.