三层串联EFP成型与分离行为

针对三层串联EFP成型及分离问题,采用数值模拟方法,描述了三层串联EFP成型过程,揭示了三层药型罩材料匹配对串联EFP分离行为的影响规律.结果表明：三层串联EFP成型过程包括冲击、闭合和自由飞行三个阶段.冲击阶段：三层罩主要在轴向发生相互碰撞,实现动能交换,形成速度差,是导致三层串联EFP分离的主要原因;闭合阶段：三层罩逐渐拉伸闭合,并同时在径向和轴向发生碰撞,影响三层罩的成型和分离特性;自由飞行阶段：三层串联EFP形貌和速度趋于稳定,彼此间不再发生碰撞,三层串联EFP之间的距离随时间逐步增大.与此同时,三层药型罩材料匹配显著影响串联EFP分离行为,45#钢罩能够实现与前铜罩的快速分离,同时阻滞后铜罩的有效分离.进一步与脉冲X光实验结果相比,数值模拟与实验结果基本吻合,验证了数值模拟的有效性.     

三层串联EFP成型与分离行为

针对三层串联EFP成型及分离问题,采用数值模拟方法,描述了三层串联EFP成型过程,揭示了三层药型罩材料匹配对串联EFP分离行为的影响规律.结果表明:三层串联EFP成型过程包括冲击、闭合和自由飞行三个阶段.冲击阶段:三层罩主要在轴向发生相互碰撞,实现动能交换,形成速度差,是导致三层串联EFP分离的主要原因;闭合阶段:三层罩逐渐拉伸闭合,并同时在径向和轴向发生碰撞,影响三层罩的成型和分离特性;自由飞行阶段:三层串联EFP形貌和速度趋于稳定,彼此间不再发生碰撞,三层串联EFP之间的距离随时间逐步增大.与此同时,三层药型罩材料匹配显著影响串联EFP分离行为,45#钢罩能够实现与前铜罩的快速分离,同时阻滞后铜罩的有效分离.进一步与脉冲X光实验结果相比,数值模拟与实验结果基本吻合,验证了数值模拟的有效性.      

Ordering and self-organization in nanocrystalline silicon

The spontaneous formation of organized nanocrystals in semiconductors has been observed during heteroepitaxial growth and chemical synthesis. The ability to fabricate size-controlled silicon nanocrystals encapsulated by insulating SiO2 would be of significant interest to the microelectronics industry. But reproducible manufacture of such crystals is hampered by the amorphous nature of SiO2 and the differing thermal expansion coefficients of the two materials. Previous attempts to fabricate Si nanocrystals failed to achieve control over their shape and crystallographic orientation, the latter property being important in systems such as Si quantum dots. Here we report the self-organization of Si nanocrystals larger than 80 A into brick-shaped crystallites oriented along the (111) crystallographic direction. The nanocrystals are formed by the solid-phase crystallization of nanometre-thick layers of amorphous Si confined between SiO2 layers. The shape and orientation of the crystallites results in relatively narrow photoluminescence, whereas isotropic particles produce qualitatively different, broad light emission. Our results should aid the development of maskless, reproducible Si nanofabrication techniques.     

三层网架的优化设计研究

通过对不同屋面组成、不同跨度和不同支承位置的4种形式的三层网架进行优化分析、求得了在给定条件下的最优网格尺寸和网架高度。通过二层与三层网架的对比计算分析、提出了三层网架的适用范围。     

三层网架的静力分析和结构选型

通过对不同支承条件不同边长比的七种形式的六十二种三层网架进行静力特性研究,得出了三层网架内力、反力及位移的分布规律。讨论了三层网架的边桁架及中层弦杆的作用。提出了不同条件下三层网架的选型问题。     

旋涂辅助连续离子反应法制备CdS纳米晶及其光电性能

为了解决CdS传统制备工艺中连续离子吸附反应(SILAR)法存在的产物颗粒小、敏化层厚度不易提高的问题,将传统SILAR法中的浸泡吸附工艺改为旋涂工艺,采用全新的旋涂辅助连续离子反应法(S-SILR)制备CdS纳米晶颗粒,同时将新旧两种方法制备的CdS纳米晶分别沉积到ZnO纳米棒有序阵列中进行对比研究,利用扫描电子显微镜(SEM)、X射线衍射(XRD)、紫外-可见吸收光谱(UV-vis)、瞬态光电流等分析手段对产品形貌、结构、光吸收性能和光电转换性能进行了表征和测试。结果表明,利用S-SILR法制备CdS纳米晶光敏层更容易形成对ZnO纳米有序阵列的完全包覆;与传统的浸泡吸附法相比,改进后的旋涂法所得ZnO/CdS复合薄膜在可见光区的光吸收和光电转换性能更加优异。CdS沉积方法的改进对提高太阳电池制备工艺的可操作性及其光电转换性能有一定的指导意义。     

[111]-/{101}晶面共暴露的锐钛矿型TiO2纳米晶的制备及可提高的光催化性能

本文以层状钛酸H1.07Ti1.73O4为前驱体，以不同含量的HF溶液为形貌控制剂，在温和的水热条件下(120~180 ℃)采用一锅法合成了共暴露[111]-/{101}晶面的方块状为主的锐钛矿型TiO2纳米晶；对制备的xHF-T180 (x = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mL)锐钛矿型TiO2纳米晶的晶体结构、形貌、微观结构、比表面积、元素电子态、光学性能和电荷迁移行为进行了表征；并对其光催化降解MB性能进行了评价. 研究结果表明，与CM-TiO2和其他xHF-T180锐钛矿型TiO2纳米晶相比，2.5HF-T180显示了最高的k值(0.0165 min-1)，分别是Blank (0.0009 min-1)、CM-TiO2 (0.0083 min-1)、0.5HF-T180 (0.0126 min-1)、1.0HF-T180 (0.0113 min-1)、1.5HF-T180 (0.0142 min-1)、2.0HF-T180 (0.0130 min-1)和3.0HF-T180 (0.0123 min-1)样品的18.33、1.99、1.31、1.46、1.16、1.27和1.34倍. 2.5HF-T180显示了最高的光催化活性可以归因于其最小的颗粒尺寸、最大的比表面积、最弱的荧光光谱强度和最小的电阻的协同效应. 本研究为合成具有较高光催化性能的锐钛矿型TiO2纳米晶以处理有机染料废水提供了新思路.     

高炉炉料结构成本模型的改进及其算法研究

对基于普通线性规划的高炉炉料结构最小成本控制模型难以适应现有炉料结构、价格变化和现场元素约束模糊化问题，建立了模糊线性规划的改进模型，并对其求解算法进行了研究。通过实例，对模型应用的有效性进行验证，对炉料价格和结构的综合考虑进行了仿真。结果表明，采用模糊线性规划方法，在保证铁水品质的同时，能最大限度地利用本企业的生产设备和工艺，合理地选择炉料，从而降低炉料成本。     

立方相Lu2O3:Eu3+纳米晶的可控合成和发光性质

采用水热方法, 通过调节前驱体的pH值, 得到不同形貌的立方相Lu₂O₃:Eu³⁺纳米棒、纳米片和纳米颗粒。利用粉末X射线衍射(XRD)、扫描电镜(SEM)、傅里叶变换红外(FTIR)光谱、光致发光(PL)谱和荧光寿命(FL)等技术对所制备的纳米晶进行了系列表征。随着纳米晶尺寸的减少, 样品的荧光强度明显减弱, 这是由于吸附在纳米晶表面的OH^-含量逐渐增加, 加速了非辐射弛豫从而降低了发光效率。此外, 也观测到源于纳米晶表面Eu³⁺离子的逐渐加强的624 nm发射以及在长波侧不断延伸的电荷迁移带长激发尾。     

三层及多层网架的应用和研究

本文论述了什么是三层,多层网架,该种网架的用途,国内外应用的实例,以及国外的研究概况。三层网架的性能,不仅取决于其形式和用钢量,而且受到支承的布置、边支撑与中层的影响。本文着重论述了常用的三层网架的形式,边支撑和中层的作用,支承的布置方法等,以及它们对杆件內力和挠度的影响。     

An explanation for a universality of transition temperatures in families of copper oxide superconductors

A remarkable mystery of the copper oxide high-transition-temperature (T(c)) superconductors is the dependence of T(c) on the number of CuO2 layers, n, in the unit cell of a crystal. In a given family of these superconductors, T(c) rises with the number of layers, reaching a peak at n = 3, and then declines: the result is a bell-shaped curve. Despite the ubiquity of this phenomenon, it is still poorly understood and attention has instead been mainly focused on the properties of a single CuO2 plane. Here we show that the quantum tunnelling of Cooper pairs between the layers simply and naturally explains the experimental results, when combined with the recently quantified charge imbalance of the layers and the latest notion of a competing order nucleated by this charge imbalance that suppresses superconductivity. We calculate the bell-shaped curve and show that, if materials can be engineered so as to minimize the charge imbalance as n increases, T(c) can be raised further.     

插电式并联混合动力汽车模型预测控制

将动态规划应用于模型预测控制构架中,建立了基于空间域的插电式并联混合动力汽车燃油经济性预测控制数学模型。基于动态规划的插电式混合动力汽车全局优化控制的仿真表明,蓄电池荷电状态(SOC)基本上都是从行驶起点时的最大值逐渐减少到终点时的最小允许值,提出理论SOC参考斜率作为模型预测控制SOC的参考斜率,并以未来行驶工况中出现的特殊工况为依据对理论SOC参考轨迹进行修正。结果表明采用此方法能使模型预测控制策略的控制效果接近全局优化控制策略的计算结果,汽车油耗显著降低。     

燃油连续加热炉数学模型

本文包括:(1)炉膛内钢坯加热数学模型;(2)最佳炉温及最低燃耗在线模型。 采用一维模型,应用Hottel多层无限大气层间的辐射热交换计算方法,把各火焰射流的作用,当量地看作是夹在上下炉气层之间的一个火焰层。它的平均温度t_f可以根据Ricou-Spalding射流吸入经验公式,计算火焰和周围炉气间的质量交换,再按热平衡方程把t_f计算出来。钢坯内部传热按一维导热问题,用差分求解。 还建立了一个较简单的炉膛传热仿真模型,据此求出各炉段单位炉温对出钢平均温度及中心温度的变化率θ_m/Ti及θ_s/Ti。还可确定最小燃耗函数P的各炉段加权系数W_i。 令各段在线炉温调节量ΔTi=(T_(i,max)—T_(i,o))—ΔT_i′,这就能在线性规划中用ΔT_i′代替ΔTi作为未知量以满足非负条件。这时目标函数P_(min)=-sum (W_iT_i′)。文中还附有一个说明各段炉温按上述线性规划进行最佳控制的例题。     

空心CdS纳米晶的合成及发光性能研究

以氯化镉和硫化钠为原料,在水相体系中合成CdS纳米晶,通过透射电子显微镜观察发现,在100℃下合成的CdS纳米晶具有空心结构,粒径为20～30nm,且壁厚均匀,约为3～5nm;在70℃下合成的CdS纳米晶为实心结构,粒径约为20nm,存在较严重的团聚现象.紫外-可见吸收光谱表明：空心CdS纳米晶的吸收波长与实心CdS纳米晶相比蓝移136.74nm,这表明其禁带宽度增大0.11eV.光致发光光谱表明：空心CdS纳米晶的表面缺陷态发射较实心CdS纳米晶有所增强,这是其存在内表面的结果.     

“程序设计方法学”双层次并行教学模式探讨

"程序设计方法学"的课程内容分为结构化程序设计和面向对象程序设计两大部分,两者处于不同的知识层面,前者具有严谨的数学模型和数学演绎形式,后者更多的建立在经验化的基础之上;根据课程内容的特点以及研究生阶段的学习状况,设计了一种双层次并行的教学模式,并且,在两个层次的教学过程中运用了整合思维的手段;对于扩充课程的知识容量,推动学生的自主学习具有积极的意义.     

Surface-confined Pt-based catalysts for strengthening oxygen reduction performance

Developing highly efficient catalysts for the oxygen reduction reaction (ORR) is a key to the fabrication of commercially viable fuel cell devices for future energy applications. Considerable progress has been made to reduce Pt usage and improve performance of the Pt catalysts by modulating exposed facets of Pt nanocrystals and combining Pt with other metals to generate bimetallic nanocrystals with structures in the form of alloys, core-shells, branches or anisotropies. Apart from the above methods, confining Pt-based nanoparticles (NPs) surfaces with elaborately selected layers such as polymers, silicon or carbons can also lead to an optimized Pt electronic structure, which is beneficial to ORR process. In this minireview, we summarize the recent advancements in the area of surface-confined Pt-based electrocatalysts for ORR with emphasis on introducing the design strategies and synthesis methodologies. The integration of these catalysts into ORR operations and the resulting performance as well as the strengthening mechanisms is also discussed. Meanwhile, the insights into the research directions are proposed in order to shed light on the future development of surface-confined Pt-based ORR catalysts.     

Trapped Electron and Hole Distribution Mismatch Induced Reliability Degradation of SONOS Type Memory Devices

The reliability of silicon-oxide-nitride-oxide-silicon (SONOS) type memories was analyzed using the charge pumping method and Ⅰ-Ⅴ tests at different temperatures to study its endurance and retention characteristics.A simple model was used to explain the charge loss phenomenon,with a dual-erasure method developed to improve the endurance and retention characteristics.The results indicate that the coexistence of injected holes and electrons after long term cycling,referred to as the mismatch problem,leads to degradation of the device characteristics.With the dual-erasure method,the threshold voltage,VT,window is maintained after 1×104 programming and erasing cycles and the charge loss is reduced by 410 mV after 72 h baking at 120℃.     

Fabrication of well-disper sive yttrium-stabilized cubic zirconia nanoparticles via vapor phase hydrolys is

The well-dispersive yttrium-stabilized cubic zirconia nanoparticles were fabricated via vapor phase hydrolysis process,and the as-synthesized cubic zirconia nanoparticles were characterized by X-ray di...     

Polarons and confinement of electronic motion to two dimensions in a layered manganite

A remarkable feature of layered transition--metal oxides-most famously, the high-temperature superconductors--is that they can display hugely anisotropic electrical and optical properties (for example, seeming to be insulating perpendicular to the layers and metallic within them), even when prepared as bulk three-dimensional single crystals. This is the phenomenon of 'confinement', a concept at odds with the conventional theory of solids, and recognized as due to magnetic and electron-lattice interactions within the layers that must be overcome at a substantial energy cost if electrons are to be transferred between layers. The associated energy gap, or 'pseudogap', is particularly obvious in experiments where charge is moved perpendicular to the planes, most notably scanning tunnelling microscopy and polarized infrared spectroscopy. Here, using the same experimental tools, we show that there is a second family of transition-metal oxides--the layered manganites La(2-2x)Sr(1+2x)Mn2O7--with even more extreme confinement and pseudogap effects. The data demonstrate quantitatively that because the charge carriers are attached to polarons (lattice- and spin-textures within the planes), it is as difficult to remove them from the planes through vacuum-tunnelling into a conventional metallic tip, as it is for them to move between Mn-rich layers within the material itself.     

基于剩余容量估算的快速蓄电池均衡

针对现有蓄电池均衡方法工作时间长、只对电压均衡而不对容量均衡等缺点,采用基于Kalman滤波器与系统参数辨识集成的方法计算蓄电池剩余容量,并提出了一种新型蓄电池容量均衡结构。该容量均衡方法采用将串联蓄电池组单体分层的结构,使得每层的蓄电池单体不但能够在层内进行容量均衡,同时还可以与其他层之间均衡,因此均衡速度得到很大提高,均衡时间比传统方法缩短50%左右,而快速均衡电路的成本并没有增加。仿真和实验结果表明,该结构比传统结构均衡速度显著增加。