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排序方式: 共有162条查询结果,搜索用时 31 毫秒
1.
由于器件的快速退化,101.5小时似乎成了Znse基蓝绿色半导体激光器难于逾越的寿命极限。分析退化机制,发现在强电流注入的半导体激光器中,热退化具有重要影响。研究表明,用作载流子限制层的宽带Ⅱ-Ⅵ族四元合金(如ZnMgSSe)只能对ZnSe中的电子有效地限制,无法对空穴很好地限制;而对BeTe,却只能对空穴进行有效的限制,无法对电子很好地限制。这导致ZnSe(或BeTe)活性层空穴(或电子)漏电发热,引起退化。本文提出以ZnSe/BeTe超晶格为蓝绿发光层,并用包络函数理论具体计算了阱宽、垒宽对载流子能级的不同影响,考察了ZnSe、BeTe厚度比和超晶格周期对带隙、载流子限制能力的调节。为研制新型长寿命蓝绿色半导体激光器提供了一条新的途径。 相似文献
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水溶性有机液流电池自2014年出现后发展迅猛,特别是近些年来有机电活性物质的降解和二聚导致的容量衰减问题得到初步解决后,该类液流电池有望作为大规模储能系统的候选者。然而能量密度较低的问题限制了其商业化的进程。对此,主要从增大溶解度、提高电化学窗口和电子的得失数这3个方面详细介绍了5种提高水溶性有机液流电池能量密度的方法——分子结构剪裁、“interaction-mediating”策略的应用、采用聚合物电活性物质、“氧化还原靶向”原理和电极表面的改性,同时对进一步提高水溶性有机液流电池能量密度的策略进行了简要展望。 相似文献
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Shanmugam Kumar Brian L. Wardle Muhamad F. Arif Jabir Ubaid 《Advanced Engineering Materials》2018,20(1)
Multilayered multi‐material interfaces are encountered in an array of fields. Here, enhanced mechanical performance of such multi‐material interfaces is demonstrated, focusing on strength and stiffness, by employing bondlayers with spatially‐tuned elastic properties realized via 3D printing. Compliance of the bondlayer is varied along the bondlength with increased compliance at the ends to relieve stress concentrations. Experimental testing to failure of a tri‐layered assembly in a single‐lap joint configuration, including optical strain mapping, reveals that the stress and strain redistribution of the compliance‐tailored bondlayer increases strength by 100% and toughness by 60%, compared to a constant modulus bondlayer, while maintaining the stiffness of the joint with the homogeneous stiff bondlayer. Analyses show that the stress concentrations for both peel and shear stress in the bondlayer have a global minimum when the compliant bond at the lap end comprises ≈10% of the bondlength, and further that increased multilayer performance also holds for long (relative to critical shear transfer length) bondlengths. Damage and failure resistance of multi‐material interfaces can be improved substantially via the compliance‐tailoring demonstrated here, with immediate relevance in additive manufacturing joining applications, and shows promise for generalized joining applications including adhesive bonding. 相似文献
4.
Uniting Strength and Toughness of Al Matrix Composites with Coordinated Al3Ni and Al3Ti Reinforcements 下载免费PDF全文
Hybrid aluminum composites are fabricated in a novel manner to characteristically induce a layer‐wise aligned distribution of micro‐scale Al3Ni and Al3Ti intermetallic particles that are formed in situ within a ductile Al matrix. The simple and unique Rolling of Randomly Orientated Layer‐wise Materials (RROLM) manufacturing methodology enables microstructural tailoring of the intermetallic reinforcing particles to prescribe enhanced crack tip deflection caused by the complex interaction of local veins of reinforcement particles, in an effort to overshadow the classical loss of toughness in large‐particle reinforced composites. The complimentary reinforcements and their interface with the Al matrix are revealed to have a gradual transition zone that functions to maintain critical cohesion with the particles and the matrix, empowering the superior load transfer capability of the particles, and reducing microvoid penetration into the matrix. In situ three‐point bending observations combined with a local strain field analysis, demonstrate the distinctive crack deflection mechanisms exhibit by the composite. Deviating from the norm, this specialized particle reinforced composite exhibited both strengthening and toughening mechanisms simultaneously, over control samples. The investigated design strategy and model material will assist materials development toward light‐weight, stronger, and tougher particle reinforced Al matrix composites. 相似文献
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David Wilcox 《Costume》2014,48(1):21-45
This paper describes the cut and construction of the doublet and hose worn as underdress to the robes and insignia of the Knights of the Most Noble Order of the Garter at the English Court under Charles II. This example belonged to Charles Stuart, sixth Duke of Lennox and third Duke of Richmond (1639–1672), who was created a knight of the Garter in 1661. It is interesting on several counts: the dominant textile is a very pure cloth of silver; the elaborate hose are constructed with reference to earlier seventeenth-century models; the garments exemplify Charles II’s understanding of the importance of ceremony to successful kingship. The suit was conserved for an exhibition at the National Museum of Scotland in Edinburgh and the essay gives some account of discoveries made through this process. In addition, the garments are placed in the context of late seventeenth- century dress. 相似文献
8.
Cd0.9-xMnxZn0.1S nanoparticles with x=0 to 0.05 were prepared by a simple chemical co-precipitation method at room temperature. Crystal structure and optical properties of the synthesized nanoparticles have been analyzed by X-ray diffraction (XRD) and UV–visible spectrophotometer. XRD confirmed the phase singularity of the synthesized material, which also confirmed the formation of Cd–Mn–Zn–S solid solution rather than secondary phase formation. Energy dispersive X-ray spectra showed the presence of Cd, Zn, Mn and S in the synthesized samples. The observed higher absorbance and lower transmittance of Mn-doped Cd0.9Zn0.1S than Cd0.9Zn0.1S is due to the size effect and also the defect states induced by Mn. The decrease in energy gap at Mn=0.01 is due the ‘sp–d’ exchange interactions between band electrons in CdS and the localized ‘d’ electrons of the Mn2+ ions. The increase in energy gap after Mn=0.01 can be explained by the excessive carriers generated by the impurity atoms. Fourier transform infrared spectroscopy (FTIR) illustrated the vibration modes of Cd–Zn–Mn–S between the wave number 530 cm−1 and 780 cm−1. Mn=0.01 doped sample exhibits a relatively high PL intensity and covers most of the visible region than the other samples; so desirable for LED application. The intensity ratio of the green band (GB) to Mn-related yellow band (YB) is decreased after Mn=0.01 which may be due the size effect or reduction of surface defect at higher doping concentrations. 相似文献
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XP、RUP结合起来开发小型项目 总被引:3,自引:2,他引:3
介绍了XP、RUP两种开发过程,指出两者在开发小型项目时有其各自的优缺点,提出可以将XP、RUP结合起来开发小型项目的观点,并给出了一些在实际开发项目应用中的结合方法。通过一个具体项目的开发经验,介绍了在实际开发小型项目中结合XP、RUP的方法和技巧。 相似文献