Analysis of flip-chip packaging challenges on copper/low-k interconnects

An interfacial-fracture-mechanics-based simulation methodology has been developed to study the flip-chip packaging effect on the copper/low-k structures. Multilevel submodeling techniques have been used to bridge the scale difference between the flip-chip packages and the metal/dielectric stacks. To achieve a smaller feature size and higher speed in future chips, SiO/sub 2/ can be replaced with low-k dielectric material in all via and trench layers or the number of metal layers can be increased. The effect of both packaging options has been evaluated. With either option, the future flip-chip copper/low-k packages are facing higher possibilities of adhesive or cohesive failure near the low-k interface. This paper provides a quantitative evaluation of the increased risk, thus providing guidelines to the next level of low-k flip-chip packages.     

An implementation of the coupled perturbed Kohn-Sham equations: perturbation due to nuclear displacements

The Coupled Perturbed Kohn-Sham equations have been implemented in the Amsterdam Density Functional program package. Our implementation differs from previous ones in many ways. This program uses density fitting to calculate the Coulomb and exchange integrals. Further, all matrix elements of the Fock type matrix and its derivatives are calculated by numerical integration. The frozen core approximation is also implemented. Our implementation is approximately 10 times faster than a finite difference algorithm, and the absolute CPU times also compare favorably with other reported implementations.     

Recalling Spatial Information as a Component of Recently and Remotely Acquired Episodic or Semantic Memories: An fMRI Study.

Activations produced by the recall of episodic and semantic memories differing in spatial content and age were examined. Recall of recent episodic memories with differing spatial content activated the medial temporal lobes and the retrosplenial-posterior cingulate cortex-precuneus complex more than recall of recent semantic memories with similarly differing spatial content. Some of these differences related to the amount of spatial information recalled because spatially richer recent memories, regardless of whether they were episodic or semantic, activated the right posterior parahippocampal cortex, precuneus, and posterior parietal cortex more. This spatial effect was found to be independent of memory age for semantic memories, although some episodic-semantic memory differences, including one in the left hippocampus, were not age independent. Episodic-semantic memory recall activation differences are therefore probably a function of the amount recalled, memory age, and what is recalled, particularly with respect to spatial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Seismic Retrofit of State Street Bridge on Interstate 80

The State Street Bridge, in Salt Lake City, was designed and built in 1965 according to the 1961 AASHO specifications; the design did not include earthquake-induced forces or displacements since only wind loads were considered. The bridge consists of four reinforced concrete (RC) bents supporting composite welded steel girders; the bents are supported on cast-in-place concrete piles and pile caps. A vulnerability analysis of the bridge was conducted that determined deficiencies in (1) confinement of column lap splice regions, (2) anchorage of longitudinal column bars in the bent cap, (3) confinement of column plastic hinge zones, and (4) shear capacity of columns and bent cap–column joints. Seismic retrofit designs using carbon-fiber-reinforced-polymer (CFRP) composites and steel jackets were performed and compared for three design spectra, including the 10% probability of exceedance in 250 years earthquake. The CFRP composite design was selected for implementation and application of the composite was carried out in the summer of 2000 and 2001, while the bridge was in service. The paper describes the CFRP composite design, which, in addition to column jackets, implemented an “ankle wrap” for improving joint shear strength and a “U-strap” for improving anchorage of column bars in the bent cap; other retrofit measures were implemented, such as bumper brackets and a deck slab retrofit. A capacity versus demand evaluation of the as-built and retrofitted bents is presented.     

Facebook User Research Using a Probability‐Based Sample and Behavioral Data

Research on Facebook users is often based on small convenience samples and on usage data collected through survey self‐reports. The current research contributes to Facebook user research, as it is based on a large, nationally representative, probability‐based, U.S. sample with Internet usage data collected from meters. Results revealed that 50% of sample members are recent Facebook users. However, within this group, there is wide variation in amount of usage between heavy, medium, and light users. Finally, based on a multivariate analysis, Facebook users are significantly more likely to be women, teens, whites, and adults with at least a high school diploma. These demographic patterns apply to heavy, medium, and light Facebook users.     

A transformation-based approach to context-aware modelling

Context-aware computing is a paradigm for governing the numerous mobile devices surrounding us. In this computing paradigm, software applications continuously and dynamically adapt to different “contexts” implying different software configurations of such devices. Unfortunately, modelling a context-aware application (CAA) for all possible contexts is only feasible in the simplest of cases. Hence, tool support verifying certain properties is required. In this article, we introduce the CAA model, in which context adaptations are specified explicitly as model transformations. By mapping this model to graphs and graph transformations, we can exploit graph transformation techniques such as critical pair analysis to find contexts for which the resulting application model is ambiguous. We validate our approach by means of an example of a mobile city guide, demonstrating that we can identify subtle context interactions that might go unnoticed otherwise.     

Group Study of Simulated Driving fMRI Data by Multiset Canonical Correlation Analysis

In this work, we apply a novel statistical method, multiset canonical correlation analysis (M-CCA), to study a group of functional magnetic resonance imaging (fMRI) datasets acquired during simulated driving task. The M-CCA method jointly decomposes fMRI datasets from different subjects/sessions into brain activation maps and their associated time courses, such that the correlation in each group of estimated activation maps across datasets is maximized. Therefore, the functional activations across all datasets are extracted in the order of consistency across different dataset. On the other hand, M-CCA preserves the uniqueness of the functional maps estimated from each dataset by avoiding concatenation of different datasets in the analysis. Hence, the cross-dataset variation of the functional activations can be used to test the hypothesis of functional-behavioral association. In this work, we study 120 simulated driving fMRI datasets and identify parietal-occipital regions and frontal lobe as the most consistently engaged areas across all the subjects and sessions during simulated driving. The functional-behavioral association study indicates that all the estimated brain activations are significantly correlated with the steering operation during the driving task. M-CCA thus provides a new approach to investigate the complex relationship between the brain functions and multiple behavioral variables, especially in naturalistic tasks as demonstrated by the simulated driving study.     

Use of Repetitive Sequences for Molecular and Cytogenetic Characterization of Avena Species from Portugal

Genomic diversity of Portuguese accessions of Avena species—diploid A. strigosa and hexaploids A. sativa and A. sterilis—was evaluated through molecular and cytological analysis of 45S rDNA, and other repetitive sequences previously studied in cereal species—rye subtelomeric sequence (pSc200) and cereal centromeric sequence (CCS1). Additionally, retrotransposons and microsatellites targeting methodologies—IRAP (inter-retrotransposon amplified polymorphism) and REMAP (retrotransposon-microsatellite amplified polymorphism)—were performed. A very high homology was detected for ribosomal internal transcribed sequences (ITS1 and ITS2) between the species analyzed, although nucleolar organizing regions (NOR) fluorescent in situ hybridization (FISH) analysis revealed distinct number of Nor loci between diploid and hexaploid species. Moreover, morphological diversity, evidenced by FISH signals with different sizes, was observed between distinct accessions within each species. pSc200 sequences were for the first time isolated from Avena species but proven to be highly similar in all genotypes analyzed. The use of primers designed for CCS1 unraveled a sequence homologous to the Ty3/gypsy retrotransposon Cereba, that was mapped to centromeric regions of diploid and hexaploid species, being however restricted to the more related A and D haplomes. Retrotransposon-based methodologies disclosed species- and accessions-specific bands essential for the accurate discrimination of all genotypes studied. Centromeric, IRAP and REMAP profiles therefore allowed accurate assessment of inter and intraspecific variability, demonstrating the potential of these molecular markers on future oat breeding programs.