新型曲面换能器阵指向性研究

利用抛物面几何结构的自聚焦性能优化设计了一种新型的抛物面换能器阵。基于声场理论,推导出换能器阵的三维指向性函数表达式。数值仿真了阵元数目、抛物面焦距和工作频率等参数对阵列指向性因数的影响。仿真实验结果表明,相对于传统平面圆环阵列而言,在换能器目数相同的情况下,抛物面相控阵列指向性因数增加了1倍,具有较高的指向性和抑制旁瓣能力,是较理想的组合声源。通过优化参数,抛物面换能器阵可获得最佳指向性,进而为声频定向扬声器的设计及研究提供了理论基础。     

一种Love波器件三维建模及特性研究

为了准确表征Love波器件的质点位移和色散关系,提出了一种Love波器件三维建模方案。在Love波器件的三维建模中,该方案用有限数量单元去逼近实际Love波器件的真实物理结构和叉指换能器、波导层等实际载荷工况。通过一个压电基片材料为128°YX-LiNbO3,金属叉指换能器为Al电极,波导层材料为ZnO薄膜的Love波器件三维模型实验,验证了该Love波器件建模方案的可行性。实验结果表明,在49~51 MHz的频率范围内,Love波模态声波的频率为49.072 MHz、49.295 MHz、49.607 MHz和50.062 MHz。在这4个频率处Love波仅存在X方向质点位移的变化,Y和Z方向的质点位移都为0。器件的色散关系为随着角频率增大,Love波的速度逐渐减小。     

面向三维集成电路版图设计的EDA插件研究

三维集成是未来微电子系统的发展方向。但是,现阶段的EDA软件如Cadence等却没有覆盖整个三维集成电路版图设计流程。为了更好的满足工程师在三维集成电路设计中的需要,本文基于SKILL语言,对业界主流版图设计工具Cadence Virtuoso进行二次开发,开发出能辅助三维集成电路设计的EDA插件。该EDA插件主要包括三种功能：自动对齐,自动打孔和三维可视化技术。最终,本文在三维集成电路的背景下设计两个并联的反相器。实验表明,该EDA插件能够满足三维集成电路设计的需求,简化了三维集成电路版图设计的过程,具有很好的易用性。     

集成成像三维新媒体的数字版权保护新方法

提出了一种新的基于集成成像的数字水印方法,利用集成成像机理和光学彩色图像的数字水印算法,实现了对集成成像三维新媒体的版权保护与内容鉴别认证,所提算法能满足稳健性和安全性的要求。通过实验,证明了所提方法的可行性和正确性,研究工作为集成成像三维新媒体的版权保护提供了新的思路与解决方法。     

铜锡合金纳米粒子的制备和性能研究

通过化学还原方法制备了铜锡合金纳米粒子,并研究分析了其的尺寸和热学性能。铜锡纳米粒子的X射线衍射分析结果显示,合成产物主要是锡纳米颗粒和铜锡合金(Cu6Sn5)纳米颗粒组成,且这些纳米粒子并未被氧化。其示差扫描量热法测得结果表明,本次合成的纳米颗粒的熔点为202.98 ℃,适合现代电子封装技术对低熔点封装材料的要求。     

A novel mechanical diced trench structure for warpage reduction in wafer level packaging process

The wafer warpage problem, mainly originated from coefficient of thermal expansion mismatch between the materials, becomes serious in wafer level packaging as large diameter wafer is adopted currently. The warpage poses threats to wafer handling, process qualities, and can also lead to serious reliability problems. In this paper, a novel mechanical diced trench structure was proposed to reduce the final wafer warpage. Deep patterned trenches with a depth about 100 μm were fabricated in the Si substrate by mechanical dicing method. Both experiment and simulation approaches were used to investigate the effect of the trenches on the wafer warpage and the influence of the geometry of the trenches was also studied. The results indicate that, by forming deep trenches, the stress on the individual die is decoupled and the total wafer warpage could be reduced. The final wafer warpage is closely related to the trench depth and die width. Trenched sample with a depth of 100 μm can decrease the wafer warpage by 51.4%.     

Recovery performance and characteristics in shape memory effects of aliphatic polyether urethane

The analysis on the recovery performance and characteristics in shape memory effects is helpful for the optimal design and engineering applications of shape memory polymers and their composites. To investigate the relationships among recovery performance, material parameters, and loading conditions, by taking aliphatic polyether urethane as an example, the researchers simulate the shape memory behaviors numerically using a three‐dimensional viscoelastic model. The material parameters for this model are taken from stress relaxation tests, rather than dynamic mechanical analysis tests. Both the unconstrained and the constrained recovery behaviors during strain‐controlled shape memory processes are analyzed. The results reveal that the unconstrained recovery occurs at the same temperature regardless of the applied strain values. Another interesting result is that the shape recovery temperature in unconstrained recovery situations increases and the maximum recovery stress under constrained recovery conditions decreases with the increase of heating rates. Copyright © 2013 John Wiley & Sons, Ltd.     

Stabilization of Large Adsorbates by Rotational Entropy: A Time‐Resolved Variable‐Temperature STM Study

Investigating the dynamics in an adlayer of the oligopyridine derivative 2‐phenyl‐4,6‐bis(6‐(pyridine‐2‐yl)‐4‐(pyridine‐4‐yl)pyridine‐2‐yl)pyrimidine (2,4′‐BTP) on Ag(111) by fast scanning tunneling microscopy (video‐STM), we found that rotating 2,4′‐BTP adsorbates coexist in a two‐dimensional (2D) liquid phase (β‐phase) in a dynamic equilibrium with static adsorbate molecules. Furthermore, exchange between an ordered phase (α‐phase) and β‐phase leads to fluctuations of the domain boundary on a time scale of seconds. Quantitative evaluation of the temperature‐dependent equilibrium between rotating and static adsorbates, evaluated from a large number of STM images, gains insight into energetic and entropic stabilization and underlines that the rotating adsorbate molecules are stabilized by an entropy contribution, which is compatible with that derived by using statistical mechanics. The general validity of the concept of entropic stabilization of rotating admolecules, favoring rotation already at room temperature, is tested for other typical small, mid‐size and large adsorbates.     

CuI‐Catalyzed Multicomponent Synthesis of Aminoindolizines from Aldehydes,Amines, and Alkynes under Solvent‐Free Conditions

A direct and efficient approach to 1‐aminoindolizines through three‐component one‐pot reaction of heteroaryl aldehydes, secondary amines and terminal alkynes catalyzed by CuI under solvent‐free conditions has been developed. This methodology provides a rapid access to substituted aminoindolizines with good yields (up to 97%).     

聚苯乙烯提取物的检测与评价

随着材料科学的迅速发展,聚合物材料以不同的形态越来越广泛地应用于食品包装中。但是由于聚合物材料自身的特性及其改性加工,导致了很多低分子量化合物的形成,因而给食品安全性带来很大隐患,也危害着人们的身体健康。为了解决这一问题,在选用材料前,必须分析聚合物材料中低分子化合物的迁移情况,考虑迁移过程对包材使用的影响。实验中选用正庚烷、8%乙醇、50%乙醇和蒸馏水作为食品模拟液,用气相色谱测定聚苯乙烯提取物的迁移量,进而将实验数据分析比较。结果显示,迁移量随着温度的升高和时间的延长而不断增加,溶剂种类的影响为:正庚烷>50%乙醇>8%乙醇>蒸馏水。