Development of pressure containment and damage tolerance technology for composite fuselage structures in large transport aircraft

NASA sponsored composites research and development programs were set in place to develop the critical engineering technologies in large transport aircraft structures. This NASA-Boeing program focused on the critical issues of damage tolerance and pressure containment generic to the fuselage structure of large pressurized aircraft. Skin-stringer and honeycomb sandwich composite fuselage shell designs were evaluated to resolve these issues. Analyses were developed to model the structural response of the fuselage shell designs, and a development test program evaluated the selected design configurations to appropriate load conditions

RIFT process analysis for the production of green composites in flax fibers and bio-based epoxy resin

In this work, a dual objective is carried out on composite materials in flax fiber and bio-based epoxy resin: to determine the process parameters and to develop a numerical model for highlighting the potential of and the limits in the production of “green” laminates through a RIFT process (Resin Infusion under Flexible Tool). For these reasons, compressibility tests were performed in order to evaluate the behavior of commercial flax woven under the vacuum bag. Subsequently, permeability tests were performed in order to evaluate the permeability curves necessary for the numerical study of the infusion process. For the numerical analyses, the commercial software PAM-RTM was adopted and validated. In this work, vaseline oil was used as the injected resin for the validation, and a bio-based epoxy commercial system was used for the study of the infusion process in a simple case study. The results were compared with a petroleum-based epoxy system typically used for infusion processes, showing the potentiality and the critical use of bio-based resins for infusion processes

Investigation of localized deformation in partially saturated sand under triaxial compression using microfocus X-ray CT with digital image correlation

AbstractIn this paper, localized deformation in partially saturated sand was investigated quantitatively using microfocus X-ray computed tomography (CT) and an image analysis of the CT images. Triaxial compression tests on a partially saturated dense Toyoura sand specimen were carried out under a low confining pressure and under drained conditions for both air and water. The development of localized deformation was observed macroscopically using microfocus X-ray CT, and the displacement field over the entire specimen was quantified by an image analysis of the CT images with the digital image correlation (DIC) technique. The progressive development of shear bands is discussed with reference to these images. In addition, the region of localization was observed microscopically by partial CT scanning on a micron scale with high spatial resolution. Changes in the particulate structures are also discussed herein. The DIC image analysis of the partial CT images provided a microscopic displacement field and indicated that very fine localized shear deformation developed before the shear bands had become visible in the macroscopic investigation

Behaviour of sandy soil subjected to dynamic loading

This thesis presents the kinematics occurring during lab-based dynamic compaction tests using high speed photography and image correlation techniques. High speed photography and X-ray microtomography have been used to analyse the behaviour of sandy soil subjected to dynamic impact. In particular, the densification mechanism of granular soils due to dynamic compaction is the main theme of the thesis. High speed photography and digital image correlation (DIC) techniques have enabled the deformation patterns, soil strains and strain localisations to be observed. Image correlation and X-ray scans revealed the formation, rate and growth of narrow tabular bands of intense deformation and significant volumetric change and provided answers towards a better understanding of the densification mechanism in dry granular soils due to dynamic compaction. As a quantitative tool, high speed photography has allowed the propagation of localised deformation and strain fields to be identified and has suggested that compaction shock bands control the kinematics of dynamic compaction. The displacement and strain results from high speed photography showed that soil deformation in the dynamic tests was dominated by a general bearing capacity mechanism similar to that widely stated in classic soil mechanics texts. Comparative static loading tests have been conducted to enable the dynamic effects to be clearly distinguished. This has enabled the densification process taking place below the soil surface to be investigated and identified. Simulations of the physical models were carried out using LS-DYNA finite element formulations for comparison and verification purposes. The FE simulations verified the general characteristics from the photography findings. However, simulation results were unable to predict the exact details of the strain localisation due to surface impacts during physical model tests

Behaviour of sandy soil subjected to dynamic loading

This thesis presents the kinematics occurring during lab-based dynamic compaction tests using high speed photography and image correlation techniques. High speed photography and X-ray microtomography have been used to analyse the behaviour of sandy soil subjected to dynamic impact. In particular, the densification mechanism of granular soils due to dynamic compaction is the main theme of the thesis. High speed photography and digital image correlation (DIC) techniques have enabled the deformation patterns, soil strains and strain localisations to be observed. Image correlation and X-ray scans revealed the formation, rate and growth of narrow tabular bands of intense deformation and significant volumetric change and provided answers towards a better understanding of the densification mechanism in dry granular soils due to dynamic compaction. As a quantitative tool, high speed photography has allowed the propagation of localised deformation and strain fields to be identified and has suggested that compaction shock bands control the kinematics of dynamic compaction. The displacement and strain results from high speed photography showed that soil deformation in the dynamic tests was dominated by a general bearing capacity mechanism similar to that widely stated in classic soil mechanics texts. Comparative static loading tests have been conducted to enable the dynamic effects to be clearly distinguished. This has enabled the densification process taking place below the soil surface to be investigated and identified. Simulations of the physical models were carried out using LS-DYNA finite element formulations for comparison and verification purposes. The FE simulations verified the general characteristics from the photography findings. However, simulation results were unable to predict the exact details of the strain localisation due to surface impacts during physical model tests

Geologic Structure and Mine Roof Falls in Selected Coal Beds Within Appalachia

This study investigated stratigraphic and structural causes of roof falls in room-and-pillar drift coal mines in nine mines in eastern Kentucky and the Dunkard Basin of West Virginia and Pennsylvania

Submarine mass wasting processes along the continental slope of the Middle American Trench

This Thesis work presents a regional-scale study of submarine mass-wasting phenomena of the continental slope of a subduction zone. The nature of the study makes it a new, outstanding contribution for two main reasons: 1) The large-scale and interdisciplinary characters of the study conform a comprehensive investigation - unmatched by any other previous study- of land sliding processes along the slope of a tectonically-active convergent margin. 2) The investigation is also unique because it looks into the processes at a subduction zone dominated by tectonic erosion. This type of geological setting represents about 50% of the world subduction zone systems, but it has been overlooked in previous studies of mass wasting processes. The study region is located along a segment of the Middle America Trench (MAT) that extends about 1500 km from the Costa Rica - Panama border to the Guatemala - Mexico boundary. The study investigates the structures of the continental slope of the Pacific-Ocean-side of Central America and the trench-region of the incoming oceanic Cocos plate. We have investigated the distribution of submarine slope failures and their deposits, the type of failures, and their seafloor morphology. We have also investigated possible preconditioning and triggering mechanisms, and the relationship of those mechanisms and the variability in failure type to the tectonic processes of this particular geological setting. Finally, we have made some inferences of the significance of mass wasting processes in the long-term evolution of the slope, compared to other geological settings. The Central America subduction zone has been the locus of intense, continued geoscientific investigation since the late 1970s that culminated with the selection of the region as the focus site for the US-Margins program and the German SFB574 during the first decade of the 21st century. Those two programs included research in a broad range of topics that attempted to advance our understanding of the entire subduction zone system. As a result numerous projects from both communities have benefited from close collaborations. This PhD work is integrated within the research project SFB 574, financed by the DFG, that has as main research goal investigations on “Volatiles and fluids in subduction zones and their impact on climate feedback and trigger mechanisms for natural disasters”. We have analyzed a database containing a compilation of multibeam bathymetry of 7 research cruises, 3 cruises of side-scan sonar imagery and core samples of a dedicated cruise. The database has been assembled in a collaborative effort between both USMargins and SFB 574 communities. Based on seafloor morphology and backscatter imagery, and seismic images we have mapped and classified 147 submarine slope failures in the region. Slope failures vary in their type, abundance and distribution along and across the slope to define six distinct segments along the MAT. The lateral extent of the six segments correlates well with similar along-trench segmentation in the character of the incoming ocean plate, expressed as changes in its relief, age and crustal thickness. We have also found that the six along-margin segments display changes in the across-slope structuring of the different geological elements, including changes in the morphological expression of upper, middle and lower slope, total slope width, and slope dip angle. This structuring of the elements of the slope appears to be related to a longterm evolution caused by the tectonic processes associated to subduction erosion. One segment covers the area of under-thrusting of Cocos Ridge under the shelf-slope offshore Osa Peninsula (southern Costa Rica). Here, 1-km-high narrow, sharp ridges and small conical seamounts festooning Cocos Ridge cause slumps often with rock and debris avalanches from a short, steep continental slope. A second segment occurs offshore central Costa Rica, where large conical seamounts and ridges of 1-3 km high and 40 km wide under-thrust the continental slope causing large re-entries of the slope toe, and furrows across the slope formed by collapse, of previously uplifted upper plate, along steep headwalls behind the under-thrusting seamounts. Failures have generated large slumps, debris flows and rock avalanches containing blocks up to 500 m in diameter. In contrast at a third segment in northern Costa Rica, offshore the North Nicoya Peninsula, a smooth incoming plate is parallel opposite by a continental slope lacking relevant mass wasting structures. The contiguous fourth segment offshore Nicaragua displays a steep middle slope with large translational slides opposite an ocean plate with numerous 1-km-tall seamounts and 100s-meter-high horst and graben relief. Under the fifth segment, offshore El Salvador, subducts a well developed horst and graben relief, but somewhat surprising the segment displays a generally failure-free slope, and only the uppermost slope displays a series of small translation slides The plate under-thrusting the sixth segment offshore Guatemala is similarly characterized by a horst and graben terrain. However, here a steeper slope exhibits frequent, small-scale failures, a few km wide, across the entire segment

Design for testability of a latch-based design

Abstract. The purpose of this thesis was to decrease the area of digital logic in a power management integrated circuit (PMIC), by replacing selected flip-flops with latches. The thesis consists of a theory part, that provides background theory for the thesis, and a practical part, that presents a latch register design and design for testability (DFT) method for achieving an acceptable level of manufacturing fault coverage for it. The total area was decreased by replacing flip-flops of read-write and one-time programmable registers with latches. One set of negative level active primary latches were shared with all the positive level active latch registers in the same register bank. Clock gating was used to select which latch register the write data was loaded to from the primary latches. The latches were made transparent during the shift operation of partial scan testing. The observability of the latch register clock gating logic was improved by leaving the first bit of each latch register as a flip-flop. The controllability was improved by inserting control points. The latch register design, developed in this thesis, resulted in a total area decrease of 5% and a register bank area decrease of 15% compared to a flip-flop-based reference design. The latch register design manages to maintain the same stuck-at fault coverage as the reference design.Salpaperäisen piirin testattavuuden suunnittelu. Tiivistelmä. Tämän opinnäytetyön tarkoituksena oli pienentää digitaalisen logiikan pinta-alaa integroidussa tehonhallintapiirissä, korvaamalla valitut kiikut salpapiireillä. Opinnäytetyö koostuu teoriaosasta, joka antaa taustatietoa opinnäytetyölle, ja käytännön osuudesta, jossa esitellään salparekisteripiiri ja testattavuussuunnittelun menetelmä, jolla saavutettiin riittävän hyvä virhekattavuus salparekisteripiirille. Kokonaispinta-alaa pienennettiin korvaamalla luku-kirjoitusrekistereiden ja kerran ohjelmoitavien rekistereiden kiikut salpapiireillä. Yhdet negatiivisella tasolla aktiiviset isäntä-salpapiirit jaettiin kaikkien samassa rekisteripankissa olevien positiivisella tasolla aktiivisten salparekistereiden kanssa. Kellon portittamisella valittiin mihin salparekisteriin kirjoitusdata ladattiin yhteisistä isäntä-salpapireistä. Osittaisessa testipolkuihin perustuvassa testauksessa salpapiirit tehtiin läpinäkyviksi siirtooperaation aikana. Salparekisterin kellon portituslogiikan havaittavuutta parannettiin jättämällä jokaisen salparekisterin ensimmäinen bitti kiikuksi. Ohjattavuutta parannettiin lisäämällä ohjauspisteitä. Salparekisteripiiri, joka suunniteltiin tässä diplomityössä, pienensi kokonaispinta-alaa 5 % ja rekisteripankin pinta-alaa 15 % verrattuna kiikkuperäiseen vertailupiiriin. Salparekisteripiiri onnistuu pitämään saman juuttumisvikamallin virhekattavuuden kuin vertailupiiri

Gunrock: GPU Graph Analytics

For large-scale graph analytics on the GPU, the irregularity of data access and control flow, and the complexity of programming GPUs, have presented two significant challenges to developing a programmable high-performance graph library. "Gunrock", our graph-processing system designed specifically for the GPU, uses a high-level, bulk-synchronous, data-centric abstraction focused on operations on a vertex or edge frontier. Gunrock achieves a balance between performance and expressiveness by coupling high performance GPU computing primitives and optimization strategies with a high-level programming model that allows programmers to quickly develop new graph primitives with small code size and minimal GPU programming knowledge. We characterize the performance of various optimization strategies and evaluate Gunrock's overall performance on different GPU architectures on a wide range of graph primitives that span from traversal-based algorithms and ranking algorithms, to triangle counting and bipartite-graph-based algorithms. The results show that on a single GPU, Gunrock has on average at least an order of magnitude speedup over Boost and PowerGraph, comparable performance to the fastest GPU hardwired primitives and CPU shared-memory graph libraries such as Ligra and Galois, and better performance than any other GPU high-level graph library.Comment: 52 pages, invited paper to ACM Transactions on Parallel Computing (TOPC), an extended version of PPoPP'16 paper "Gunrock: A High-Performance Graph Processing Library on the GPU

Proceedings of the First PhD Symposium on Sustainable Ultrascale Computing Systems (NESUS PhD 2016)

Proceedings of the First PhD Symposium on Sustainable Ultrascale Computing Systems (NESUS PhD 2016) Timisoara, Romania. February 8-11, 2016.The PhD Symposium was a very good opportunity for the young researchers to share information and knowledge, to present their current research, and to discuss topics with other students in order to look for synergies and common research topics. The idea was very successful and the assessment made by the PhD Student was very good. It also helped to achieve one of the major goals of the NESUS Action: to establish an open European research network targeting sustainable solutions for ultrascale computing aiming at cross fertilization among HPC, large scale distributed systems, and big data management, training, contributing to glue disparate researchers working across different areas and provide a meeting ground for researchers in these separate areas to exchange ideas, to identify synergies, and to pursue common activities in research topics such as sustainable software solutions (applications and system software stack), data management, energy efficiency, and resilience.European Cooperation in Science and Technology. COS