Vortical structures on three-dimensional shock control bumps

The vortical wake structure produced by a three-dimensional shock control bump (SCB) is thought to be useful for controlling transonic buffet on airfoils. However, at present the vorticity produced is relatively weak and the production mechanism is not well understood. Using a combined experimental and computational approach, a preliminary investigation on the wake vorticity for different bump geometries has been carried out. The structure of the wake for on and off-design conditions are considered, and the effects on the downstream boundary layer demonstrated. Three main vortical structures are observed: a primary vortex pair, weak inter-bump vortices and shear flow in the lambda-shock region. The effect of pressure gradients on vortex strength is examined and it is found that spanwise pressure gradients on the front section of the bump are the most significant parameter influencing vortex strength. © 2013 by S.P. Colliss et al.

Development of solar-blind AlGaN 128x128 ultraviolet focal plane arrays

This paper reports the development of solar-blind aluminum gallium nitride (AlGaN) 128x128 UV Focal Plane Arrays (FPAs). The back-illuminated hybrid FPA architecture consists of an 128x128 back-illuminated AlGaN PIN detector array that is bump-mounted to a matching 128x128 silicon CMOS readout integrated circuit (ROIC) chip. The 128x128 p-i-n photodiode arrays with cuton and cutoff wavelengths of 233 and 258 nm, with a sharp reduction in response to UVB (280-320 nm) light. Several examples of solar-blind images are provided. This solar-blind band FPA has much better application prospect.

HIRFL-CSRm电子冷却模拟与实验

本论文从理论、模拟和实验三方面研究了HIRFL-CSRm离子束的电子冷却累积过程。 在没有内靶实验装置的电子冷却储存环中，离子束的冷却过程，是离子在电子冷却效应和以束内散射为主的各种加热效应共同作用下，发射度收缩并趋于平衡的过程。其中磁化冷却力的求解是研究电子冷却效应的理论基础，本论文采用Monte-Carlo技术解决了两体碰撞模型下磁化冷却力复杂积分表达式的求解，探讨了影响磁化冷却力的参数。针对离子束内散射过程，论文在B-M模型下束内散射率表达式的基础上，通过应用Carlson第二类椭圆积分形式实现了束内散射导致的束流发射度和动量分散变化的快速计算，分析了其对HIRFL-CSRm冷却累积过程的影响。 由于冷却力是离子-电子相对速度的复杂函数，而且考虑离子在储存环中的横向振荡和纵向运动特性，以及电子束空间电荷效应等情况下，冷却过程中束流发射度和动量分散的时间变化率无法解析计算。本论文采用模型离子跟踪方法，模拟了离子束特征参数在冷却过程中的变化，明确了电子束参数对冷却过程的影响函数，计算了几种典型离子束冷却累积的最佳参数值，并对测量冷却效应的实验方法进行了模拟研究。 对HIRFL-CSRm五种重离子束流（7.07MeV/u12C4+、8.28MeV/u12C5+、7.07MeV/u12C6+、21.6MeV/u36Ar18+、2.93MeV/u129Xe27+）的电子冷却和累积过程进行了初步的实验研究。采用电子束能量调制的方法，测量了12C6+和36Ar18+离子束受到的纵向冷却力随离子-电子相对速度变化的函数，分析了电子束密度、形状及电子束-离子束夹角对36Ar18+离子受到的纵向冷却力大小的影响。通过改变Bump触发的间隔时间研究了12C6+离子的横向冷却效应。实验研究了电子束密度、形状对几种束流的累积效率及储存束流寿命的影响，以及Bump幅度、Bump时间结构、注入间隔时间、绝热展开因子等参数对束流累积效率的影响。实验测量并理论验证了12C6+和36Ar18+强流束的集体效应，探讨了强流离子束的不稳定性。最后，论文展望了在HIRFL-CSR上进一步开展电子冷却实验的方向

CSR特殊磁铁研制

特殊磁铁主要指用于同步加速器束流的注入和引出系统中的各类磁铁，如切割磁铁、BUMP磁铁、KICKER磁铁等。从结构和用途上来看，特殊磁铁基本属于二极偏转磁铁范畴；与常规的二极磁铁相比，只是在运行模式、磁场分布和好场区位置、杂散场分布、磁铁功能以及磁铁结构和材料等方面具有突出的特殊性。如切割磁铁的好场区要紧贴切割边，而切割边外侧的杂散场要降到主场的千分之一以下；BUMP磁铁和KICKER磁铁的磁场值不高，但要以很快的脉冲方式工作，所以就具有大电流、线圈匝数少的特点。各种特殊的性能要求使得特殊磁铁的设计和制造相当复杂。 HIRFL-CSR工程共有四台切割磁铁、四套BUMP磁铁以及两套KICKER磁铁用于加速器束流的注入和引出系统中。论文介绍了特殊磁铁的选型、材料选取、电磁设计、二维及三维磁场计算、电磁参数计算、冷却计算、结构设计以及工艺设计等磁铁设计的全部过程；另外，对磁铁研制的具体细节以及技术要求、加工制造以及测试结果也作了比较全面的介绍。论文将磁铁的二维及三维磁场计算作为设计和论述的重点；因为就目前的技术水平来说，二维及三维磁场的计算是磁铁设计的主要环节，是磁场优化的主要手段，也是其他主要电磁参数计算的基础。特别是三维磁场的计算结果，是磁铁设计的主要技术依据，是一种仿真度极高且经济实用的模拟过程。一些比较成熟的磁场计算软件，如TOSCA、ANSYS、MAFIA等更是具有人机界面简单、建模方便、计算结果直观可靠等优点。特殊磁铁的磁场计算所用的程序是TOSCA；从文中提供的测试结果看，计算结果与实测值的误差只有 1 %，可见其结果是极其可信的。从测试和运行结果来看，各种特殊磁铁的研制是成功的。特殊磁铁的成功研制为HIRFL-CSR的束流注入和引出提供了硬件基础

Widzieć siebie — z czasu minionego ("Tamten" Bolesława Leśmiana i "Kilkunastoletnia" Wisławy Szymborskiej)

The article presents a juxtaposition of the following two brilliant poems "Tamten" (from the collection of poems entitled "Napój cienisty", 1936) and "Kilkunastoletnia" (from the collection of poems entitled "Tutaj", 2009) that employ the same idea of an encounter with oneself – an adolescent person (in the former poem) and a teenage girl (in the latter). The poems exceed the literary convention of just a lyrical reminiscence of the past, they rather form a particular dialogue with the narrator as he/she was years ago, or even propose a kind of a confrontation. Both poems indirectly feature reflections on the passing time and on the author's identity. The poem written by Leśmian fits perfectly into his poetical system, both in terms of the introduction of metaphysical threads and the application of the elements of a love poem and in terms of the plot outline, somewhat reminiscent of his ballads. Szymborska's poem also concurs with her own poetics mostly due to the characteristic subtle auto-irony.

A tale of three functions: The self-reported uses of autobiographical memory

Theories hold that autobiographical memory serves several broad functions (directive, self, and social). In the current study, items were derived from the theoretical literature to create the Thinking About Life Experiences (TALE) questionnaire to empirically assess these three functions. Participants (N = 167) completed the TALE. To examine convergent validity, they also rated their overall tendency to think about and to talk about the past and completed the Reminiscence Functions Scale (Webster, 1997). The results lend support to the existence of these theoretical functions, but also offer room for refinements in future thinking about both the breadth and specificity of the functions that autobiographical memory serves.

Distribution of important and word-cued autobiographical memories in 20-, 35-, and 70-year-old adults.

For word-cued autobiographical memories, older adults had an increase, or bump, from the ages 10 to 30. All age groups had fewer memories from childhood than from other years and a power-function retention for memories from the most recent 10 years. There were no consistent differences in reaction times and rating scale responses across decades. Concrete words cued older memories, but no property of the cues predicted which memories would come from the bump. The 5 most important memories given by 20- and 35-year-old participants were distributed similarly to their word-cued memories, but those given by 70-year-old participants came mostly from the single 20-to-30 decade. No theory fully accounts for the bump.

Selected Piano Works by Schumann, Liszt, and Brahms Incorporating or Based on Pre-existing Music

This dissertation shows how Schumann, Liszt and Brahms composed piano works based in a variety of ways on other music that already existed. My idea to do this project came through my fascination with Brahms’s Variations on a Theme by Paganini, which was the first piece selected. Brahms composed six sets of variations for solo piano, and I also chose Variations and Fugue on a Theme by Handel. Besides the variations, I included Brahms’s Ballade in D minor, Op. 10 No. 1, based on the Scottish ballad “Edward”. This piece demonstrates that Brahms applied pre-existing music not only in the form of variations, but also in other genres. Among Romantic composers, Schumann and Liszt are two others besides Brahms whose music frequently quotes pre-existing materials. In Schumann’s output, the inspiration from Clara Wieck is significant. The best examples may be the Impromptus Op. 5 and the third movement of the Grand Sonata No. 3, Op. 14, in which Schumann quotes the music by Clara Wieck as the theme of the variations and in the other movements as well to unify the entire piece. In addition, Schumann quotes the old German folk song “Grossvater Tanz” (Grandfather Dance) in the finale of Papillons. The same tune also appears in Carnaval for a programmatic purpose. These two pieces are a clear illustration that Schumann applies pre-existing music, and in addition they represent the spirit of literary reference. Liszt is well known for his superb transformations of other composers’ works into glorious piano compositions. Liszt drew his inspirations from different genres, including both vocal and instrumental music. His ability to turn earlier musical materials into virtuosic solo piano pieces that demonstrate his brilliance in creating imaginative keyboard sounds is remarkable. Among those pieces composed by Liszt, terms such paraphrase, reminiscence, or fantasy frequently appear as titles. I selected two such pieces: Rigoletto: Paraphrase de concert, S. 434 and Rondeau fantastique sur un thème espagnol, S. 252. In addition, Liszt also uses variation form to explore the possibilities of pre-existing themes. The piece I chose to represent this is Variations on the Theme “Weinen, Klagen, Sorgen, Zagen” and Crucifixus from the Mass in B minor by J.S Bach, S.180. This dissertation comprises three piano recitals that were performed in 2010 and 2011 in Ulrich Recital Hall and Gildenhorn Recital Hall of the Clarice Smith Performing Arts Center of the University of Maryland. The recordings are documented on compact discs that are housed within the University of Maryland Library System.

The effect of reflow process on the contact resistance and reliability of anisotropic conductive film interconnection for flip chip on flex applications

The work presented in this paper focuses on the effect of reflow process on the contact resistance and reliability of anisotropic conductive film (ACF) interconnection. The contact resistance of ACF interconnection increases after reflow process due to the decrease in contact area of the conducting particles between the mating I/O pads. However, the relationship between the contact resistance and bonding parameters of the ACF interconnection with reflow treatment follows the similar trend to that of the as-bonded (i.e. without reflow) ACF interconnection. The contact resistance increases as the peak temperature of reflow profile increases. Nearly 40% of the joints were found to be open after reflow with 260 °C peak temperature. During the reflow process, the entrapped (between the chip and substrate) adhesive matrix tries to expand much more than the tiny conductive particles because of the higher coefficient of thermal expansion, the induced thermal stress will try to lift the bump from the pad and decrease the contact area of the conductive path and eventually, leading to a complete loss of electrical contact. In addition, the environmental effect on contact resistance such as high temperature/humidity aging test was also investigated. Compared with the ACF interconnections with Ni/Au bump, higher thermal stress in the Z-direction is accumulated in the ACF interconnections with Au bump during the reflow process owing to the higher bump height, thus greater loss of contact area between the particles and I/O pads leads to an increase of contact resistance and poorer reliability after reflow.

Experimental and modeling analysis of the reliability of the anisotropic conductive films

Experiments as well as computer modeling methods have been used to investigate the effect of the solder reflow process on the electrical characteristics and reliability of anisotropic conductive film (ACF) interconnections. In the experiments, the contact resistance of the ACF interconnections was found to increase after a subsequent reflow and the magnitude of this increase was strongly correlated to the peak temperature of the reflow profile. In fact, nearly 40 percent of the joints were opened (i.e. lifted away from the pad) after the reflow with a peak temperature of 260 OC while no openings was observed when the peak temperature was 210 "C. It is believed that the CTE mismatch between the polymer particle and the adhesive matrix is the main cause of this contact degradation. To understand this phenomenon better, a 3-D model of an ACF joint structure was built and Finite Element Analysis was used to predict the stress distrihution in the conductive particles, adhesive matrix and metal pads during the reflow process. The effects of the peak temperature, the CTE of the adhesive matrix and the bump height on the reliability of the ACF interconnections were discussed.

Modelling the performance of lead-Free solder interconnects for copper bumped flip-chip devices

Traditionally, before flip chips can be assembled the dies have to be attached with solder bumps. This process involves the deposition of metal layers on the Al pads on the dies and this is called the under bump metallurgy (UBM). In an alternative process, however, Copper (Cu) columns can be used to replace solder bumps and the UBM process may be omitted altogether. After the bumping process, the bumped dies can be assembled on to the printed circuit board (PCB) by using either solder or conductive adhesives. In this work, the reliability issues of flip chips with Cu column bumped dies have been studied. The flip chip lifetime associated with the solder fatigue failure has been modeled for a range of geometric parameters. The relative importance of these parameters is given and solder volume has been identified as the most important design parameter for long-term reliability. Another important problem that has been studied in this work is the dissolution of protection metals on the pad and Cu column in the reflow process. For small solder joints the amount of Cu which dissolves into the molten solder after the protection layers have worn out may significantly affect solder joint properties.

Modelling the metal arc weldpool

Traditionally, before flip chips can be assembled the dies have to be attached with solder bumps. This process involves the deposition of metal layers on the Al pads on the dies and this is called the under bump metallurgy (UBM). In an alternative process, however, Copper (Cu) columns can be used to replace solder bumps and the UBM process may be omitted altogether. After the bumping process, the bumped dies can be assembled on to the printed circuit board (PCB) by using either solder or conductive adhesives. In this work, the reliability issues of flip chips with Cu column bumped dies have been studied. The flip chip lifetime associated with the solder fatigue failure has been modeled for a range of geometric parameters. The relative importance of these parameters is given and solder volume has been identified as the most important design parameter for long-term reliability. Another important problem that has been studied in this work is the dissolution of protection metals on the pad and Cu column in the reflow process. For small solder joints the amount of Cu which dissolves into the molten solder after the protection layers have worn out may significantly affect solder joint properties.

Predicting optimal process conditions for flip-chip aassembly using copper column bumped dies

Recently, research has been carried out to test a novel bumping method which omits the under bump metallurgy (UBM) forming process by bonding copper columns directly onto the Al pads of the silicon dies. This bumping method could be adopted to simplify the flip chip assembly process, increase the productivity and achieve a higher I/O count. Computer modelling methods are used to predict the shape of solder joints and response of the flip chip to thermal cyclic loading. The accumulated plastic strain energy at the comer solder joints is used as the damage indicator. Models with a range of design parameters have been compared for their reliability. The ranking of the relative importance of these parameters is given. Results from these analyses are being used by our industrial and academic partners to identify optimal design conditions.

Computer modelling of the reliability of flip chips with metal column bumping

Recently, research has been carried out to test a novel bumping method which omits the under bump metallurgy forming process by bonding copper columns directly onto the Al pads of the silicon dies. This bumping method could be adopted to simplify the flip chip manufacturing process, increase the productivity and achieve a higher I/O count. This paper describes an investigation of the solder joint reliability of flip-chips based on this new bumping process. Computer modelling methods are used to predict the shape of solder joints and response of flip chips to thermal cyclic loading. The accumulated plastic strain energy at the comer solder joints is used as the damage indicator. Models with a range of design parameters have been compared for their reliability. The parameters that have been investigated are the copper column height, radius and solder volume. The ranking of the relative importance of these parameters is given. For most of the results presented in the paper, the solder material has been assumed to be the lead-free 96.5Sn3.5Ag alloy but some results for 60Sn40Pb solder joints have also been presented.