Sample records for overcome software brittleness

  1. Overcoming the brittleness of glass through bio-inspiration and micro-architecture.

    PubMed

    Mirkhalaf, M; Dastjerdi, A Khayer; Barthelat, F

    2014-01-01

    Highly mineralized natural materials such as teeth or mollusk shells boast unusual combinations of stiffness, strength and toughness currently unmatched by engineering materials. While high mineral contents provide stiffness and hardness, these materials also contain weaker interfaces with intricate architectures, which can channel propagating cracks into toughening configurations. Here we report the implementation of these features into glass, using a laser engraving technique. Three-dimensional arrays of laser-generated microcracks can deflect and guide larger incoming cracks, following the concept of 'stamp holes'. Jigsaw-like interfaces, infiltrated with polyurethane, furthermore channel cracks into interlocking configurations and pullout mechanisms, significantly enhancing energy dissipation and toughness. Compared with standard glass, which has no microstructure and is brittle, our bio-inspired glass displays built-in mechanisms that make it more deformable and 200 times tougher. This bio-inspired approach, based on carefully architectured interfaces, provides a new pathway to toughening glasses, ceramics or other hard and brittle materials.

  2. Overcoming the brittleness of glass through bio-inspiration and micro-architecture

    NASA Astrophysics Data System (ADS)

    Mirkhalaf, M.; Dastjerdi, A. Khayer; Barthelat, F.

    2014-01-01

    Highly mineralized natural materials such as teeth or mollusk shells boast unusual combinations of stiffness, strength and toughness currently unmatched by engineering materials. While high mineral contents provide stiffness and hardness, these materials also contain weaker interfaces with intricate architectures, which can channel propagating cracks into toughening configurations. Here we report the implementation of these features into glass, using a laser engraving technique. Three-dimensional arrays of laser-generated microcracks can deflect and guide larger incoming cracks, following the concept of ‘stamp holes’. Jigsaw-like interfaces, infiltrated with polyurethane, furthermore channel cracks into interlocking configurations and pullout mechanisms, significantly enhancing energy dissipation and toughness. Compared with standard glass, which has no microstructure and is brittle, our bio-inspired glass displays built-in mechanisms that make it more deformable and 200 times tougher. This bio-inspired approach, based on carefully architectured interfaces, provides a new pathway to toughening glasses, ceramics or other hard and brittle materials.

  3. The anti-proliferative and anti-angiogenic effect of the methanol extract from brittle star.

    PubMed

    Baharara, Javad; Amini, Elaheh; Mousavi, Marzieh

    2015-04-01

    Anti-angiogenic therapy is a crucial step in cancer treatment. The discovery of new anti-angiogenic compounds from marine organisms has become an attractive concept in anti-cancer therapy. Because little data correlated to the pro- and anti-angiogenic efficacies of Ophiuroidea, which include brittle star, the current study was designed to explore the anti-angiogenic potential of brittle star methanol extract in vitro and in vivo. The anti-proliferative effect of brittle star extract on A2780cp cells was examined by MTT assays, and transcriptional expression of VEGF and b-FGF was evaluated by RT-PCR. In an in vivo model, 40 fertilized Ross eggs were divided into control and three experimental groups. The experimental groups were incubated with brittle star extract at concentrations of 25, 50 and 100 µg/ml, and photographed by photo-stereomicroscopy. Ultimately, numbers and lengths of vessels were measured by Image J software. Data were analyzed with SPSS software (p<0.05). Results illustrated that the brittle star extract exerted a dose- and time-dependent anti-proliferative effect on A2780cp cancer cells. In addition, VEGF and b-FGF expression decreased with brittle star methanol extract treatment. Macroscopic evaluations revealed significant changes in the second and third experimental group compared to controls (p<0.05). These finding revealed the anti-angiogenic effects of brittle star methanol extract in vitro and in vivo confer novel insight into the application of natural marine products in angiogenesis-related pathologies.

  4. A brittle star-like robot capable of immediately adapting to unexpected physical damage.

    PubMed

    Kano, Takeshi; Sato, Eiki; Ono, Tatsuya; Aonuma, Hitoshi; Matsuzaka, Yoshiya; Ishiguro, Akio

    2017-12-01

    A major challenge in robotic design is enabling robots to immediately adapt to unexpected physical damage. However, conventional robots require considerable time (more than several tens of seconds) for adaptation because the process entails high computational costs. To overcome this problem, we focus on a brittle star-a primitive creature with expendable body parts. Brittle stars, most of which have five flexible arms, occasionally lose some of them and promptly coordinate the remaining arms to escape from predators. We adopted a synthetic approach to elucidate the essential mechanism underlying this resilient locomotion. Specifically, based on behavioural experiments involving brittle stars whose arms were amputated in various ways, we inferred the decentralized control mechanism that self-coordinates the arm motions by constructing a simple mathematical model. We implemented this mechanism in a brittle star-like robot and demonstrated that it adapts to unexpected physical damage within a few seconds by automatically coordinating its undamaged arms similar to brittle stars. Through the above-mentioned process, we found that physical interaction between arms plays an essential role for the resilient inter-arm coordination of brittle stars. This finding will help develop resilient robots that can work in inhospitable environments. Further, it provides insights into the essential mechanism of resilient coordinated motions characteristic of animal locomotion.

  5. A brittle star-like robot capable of immediately adapting to unexpected physical damage

    PubMed Central

    Sato, Eiki; Ono, Tatsuya; Aonuma, Hitoshi; Matsuzaka, Yoshiya; Ishiguro, Akio

    2017-01-01

    A major challenge in robotic design is enabling robots to immediately adapt to unexpected physical damage. However, conventional robots require considerable time (more than several tens of seconds) for adaptation because the process entails high computational costs. To overcome this problem, we focus on a brittle star—a primitive creature with expendable body parts. Brittle stars, most of which have five flexible arms, occasionally lose some of them and promptly coordinate the remaining arms to escape from predators. We adopted a synthetic approach to elucidate the essential mechanism underlying this resilient locomotion. Specifically, based on behavioural experiments involving brittle stars whose arms were amputated in various ways, we inferred the decentralized control mechanism that self-coordinates the arm motions by constructing a simple mathematical model. We implemented this mechanism in a brittle star-like robot and demonstrated that it adapts to unexpected physical damage within a few seconds by automatically coordinating its undamaged arms similar to brittle stars. Through the above-mentioned process, we found that physical interaction between arms plays an essential role for the resilient inter-arm coordination of brittle stars. This finding will help develop resilient robots that can work in inhospitable environments. Further, it provides insights into the essential mechanism of resilient coordinated motions characteristic of animal locomotion. PMID:29308250

  6. Shortcomings of existing systems for registration and legal protection of software products and possible ways to overcome them

    NASA Astrophysics Data System (ADS)

    Liapidevskiy, A. V.; Petrov, A. S.; Zhmud, V. A.; Sherubneva, I. G.

    2018-05-01

    The paper reveals the shortcomings of the existing system of registration and legal protection of software products. The system has too many disadvantages and shortcomings. Explanatory examples are given. Possible ways of overcoming these shortcomings are discussed. The paper also gives possible prospects for the use of new digital technologies. Also in the paper, the information is provided about the modern software components for protecting intellectual property rights of State corporations

  7. Brittle diabetes: Psychopathology and personality.

    PubMed

    Pelizza, Lorenzo; Pupo, Simona

    The term "brittle" is used to describe an uncommon subgroup of patients with type I diabetes whose lives are disrupted by severe glycaemic instability with repeated and prolonged hospitalization. Psychosocial problems are the major perceived underlying causes of brittle diabetes. Aim of this study is a systematic psychopathological and personological assessment of patients with brittle diabetes in comparison with subjects without brittle diabetes, using specific parameters of general psychopathology and personality disorders following the multi-axial format of the current DSM-IV-TR (Diagnostic and Statistical manual of Mental Disorders - IV Edition - Text Revised) diagnostic criteria for mental disorders. Patients comprised 42 subjects with brittle diabetes and a case-control group of 42 subjects with stable diabetes, matched for age, gender, years of education, and diabetes duration. General psychopathology and the DSM-IV-TR personality disorders were assessed using the Symptom Checklist-90-Revised (SCL-90-R) and the Structured Clinical Interview for axis II personality Disorders (SCID-II). The comparison for SCL-90-R parameters revealed no differences in all primary symptom dimensions and in the three global distress indices between the two groups. However, patients with brittle diabetes showed higher percentages in borderline, histrionic, and narcissistic personality disorder. In this study, patients with brittle diabetes show no differences in terms of global severity of psychopathological distress and specific symptoms of axis I DSM-IV-TR psychiatric diagnoses in comparison with subjects without brittle diabetes. Differently, individuals with brittle diabetes are more frequently affected by specific DSM-IV-TR cluster B personality disorders. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Effects of Temperature and Humidity History on Brittleness of α-Sulfonated Fatty Acid Methyl Ester Salt Crystals.

    PubMed

    Watanabe, Hideaki; Morigaki, Atsunori; Kaneko, Yukihiro; Tobori, Norio; Aramaki, Kenji

    2016-01-01

    α-Sulfonated fatty acid methyl ester salts (MES), which were made from vegetable sources, are attractive candidates for eco-friendly washing detergents because they have various special features like excellent detergency, favorable biodegradability, and high stability against enzymes. To overcome some disadvantages of powder-type detergents like caking, sorting, and dusting, we studied how temperature and humidity history, as a model for long-term storage conditions, can affect crystalline structures and reduce the brittleness of MES powder. We characterized the crystalline structure of MES grains using small-angle X-ray scattering, wide-angle X-ray scattering, differential scanning calorimetry, and Fourier transform infrared spectroscopy measurements and determined the yield values, which measure the brittleness of MES grains, in shear stress using dynamic viscoelasticity measurements. This study confirmed that MES crystals form three pseudo-polymorphs via thermal or humidity conditioning: metastable crystals (αsubcell), anhydrous crystals (β subcell), and dihydrate crystals (β' subcell). Further, we found that the yield value increases upon phase transition from the β subcell to the β' subcell and from the β' subcell to the αsubcell. Therefore, controlling the thermal and humidity conditioning of MES grains is an effective way to decrease the brittleness of MES powders and can be used to overcome the above mentioned disadvantages of powder-type detergents in the absence of co-surfactants.

  9. Brittle Splitting Nails (Onychoschizia)

    MedlinePlus

    ... be divided into dry and brittle (too little moisture) and soft and brittle (often too much moisture). The usual cause is repeated wetting and drying ... that the nails may be getting too much moisture or being damaged by chemicals such as detergents, ...

  10. Assessment of Mudrock Brittleness with Micro-scratch Testing

    NASA Astrophysics Data System (ADS)

    Hernandez-Uribe, Luis Alberto; Aman, Michael; Espinoza, D. Nicolas

    2017-11-01

    Mechanical properties are essential for understanding natural and induced deformational behavior of geological formations. Brittleness characterizes energy dissipation rate and strain localization at failure. Brittleness has been investigated in hydrocarbon-bearing mudrocks in order to quantify the impact of hydraulic fracturing on the creation of complex fracture networks and surface area for reservoir drainage. Typical well logging correlations associate brittleness with carbonate content or dynamic elastic properties. However, an index of rock brittleness should involve actual rock failure and have a consistent method to quantify it. Here, we present a systematic method to quantify mudrock brittleness based on micro-mechanical measurements from the scratch test. Brittleness is formulated as the ratio of energy associated with brittle failure to the total energy required to perform a scratch. Soda lime glass and polycarbonate are used for comparison to identify failure in brittle and ductile mode and validate the developed method. Scratch testing results on mudrocks indicate that it is possible to use the recorded transverse force to estimate brittleness. Results show that tested samples rank as follows in increasing degree of brittleness: Woodford, Eagle Ford, Marcellus, Mancos, and Vaca Muerta. Eagle Ford samples show mixed ductile/brittle failure characteristics. There appears to be no definite correlation between micro-scratch brittleness and quartz or total carbonate content. Dolomite content shows a stronger correlation with brittleness than any other major mineral group. The scratch brittleness index correlates positively with increasing Young's modulus and decreasing Poisson's ratio, but shows deviations in rocks with distinct porosity and with stress-sensitive brittle/ductile behavior (Eagle Ford). The results of our study demonstrate that the micro-scratch test method can be used to investigate mudrock brittleness. The method is particularly useful for

  11. A new tablet brittleness index.

    PubMed

    Gong, Xingchu; Sun, Changquan Calvin

    2015-06-01

    Brittleness is one of the important material properties that influences the success or failure of powder compaction. We have discovered that the reciprocal of diametrical elastic strain at fracture is the most suitable tablet brittleness indices (TBIs) for quantifying brittleness of pharmaceutical tablets. The new strain based TBI is supported by both theoretical considerations and a systematic statistical analysis of friability data. It is sufficiently sensitive to changes in both tablet compositions and compaction parameters. For all tested materials, it correctly shows that tablet brittleness increases with increasing tablet porosity for the same powder. In addition, TBI increases with increasing content of a brittle excipient, lactose monohydrate, in the mixtures with a plastic excipient, microcrystalline cellulose. A probability map for achieving less than 1% tablet friability at various combinations of tablet tensile strength and TBI was constructed. Data from marketed tablets validate this probability map and a TBI value of 150 is recommended as the upper limit for pharmaceutical tablets. This TBI can be calculated from the data routinely obtained during tablet diametrical breaking test, which is commonly performed for assessing tablet mechanical strength. Therefore, it is ready for adoption for quantifying tablet brittleness to guide tablet formulation development since it does not require additional experimental work. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Fracturing and brittleness index analyses of shales

    NASA Astrophysics Data System (ADS)

    Barnhoorn, Auke; Primarini, Mutia; Houben, Maartje

    2016-04-01

    The formation of a fracture network in rocks has a crucial control on the flow behaviour of fluids. In addition, an existing network of fractures , influences the propagation of new fractures during e.g. hydraulic fracturing or during a seismic event. Understanding of the type and characteristics of the fracture network that will be formed during e.g. hydraulic fracturing is thus crucial to better predict the outcome of a hydraulic fracturing job. For this, knowledge of the rock properties is crucial. The brittleness index is often used as a rock property that can be used to predict the fracturing behaviour of a rock for e.g. hydraulic fracturing of shales. Various terminologies of the brittleness index (BI1, BI2 and BI3) exist based on mineralogy, elastic constants and stress-strain behaviour (Jin et al., 2014, Jarvie et al., 2007 and Holt et al., 2011). A maximum brittleness index of 1 predicts very good and efficient fracturing behaviour while a minimum brittleness index of 0 predicts a much more ductile shale behaviour. Here, we have performed systematic petrophysical, acoustic and geomechanical analyses on a set of shale samples from Whitby (UK) and we have determined the three different brittleness indices on each sample by performing all the analyses on each of the samples. We show that each of the three brittleness indices are very different for the same sample and as such it can be concluded that the brittleness index is not a good predictor of the fracturing behaviour of shales. The brittleness index based on the acoustic data (BI1) all lie around values of 0.5, while the brittleness index based on the stress strain data (BI2) give an average brittleness index around 0.75, whereas the mineralogy brittleness index (BI3) predict values below 0.2. This shows that by using different estimates of the brittleness index different decisions can be made for hydraulic fracturing. If we would rely on the mineralogy (BI3), the Whitby mudstone is not a suitable

  13. A review on ductile mode cutting of brittle materials

    NASA Astrophysics Data System (ADS)

    Antwi, Elijah Kwabena; Liu, Kui; Wang, Hao

    2018-06-01

    Brittle materials have been widely employed for industrial applications due to their excellent mechanical, optical, physical and chemical properties. But obtaining smooth and damage-free surface on brittle materials by traditional machining methods like grinding, lapping and polishing is very costly and extremely time consuming. Ductile mode cutting is a very promising way to achieve high quality and crack-free surfaces of brittle materials. Thus the study of ductile mode cutting of brittle materials has been attracting more and more efforts. This paper provides an overview of ductile mode cutting of brittle materials including ductile nature and plasticity of brittle materials, cutting mechanism, cutting characteristics, molecular dynamic simulation, critical undeformed chip thickness, brittle-ductile transition, subsurface damage, as well as a detailed discussion of ductile mode cutting enhancement. It is believed that ductile mode cutting of brittle materials could be achieved when both crack-free and no subsurface damage are obtained simultaneously.

  14. Brittleness Effect on Rock Fatigue Damage Evolution

    NASA Astrophysics Data System (ADS)

    Nejati, Hamid Reza; Ghazvinian, Abdolhadi

    2014-09-01

    The damage evolution mechanism of rocks is one of the most important aspects in studying of rock fatigue behavior. Fatigue damage evolution of three rock types (onyx marble, sandstone and soft limestone) with different brittleness were considered in the present study. Intensive experimental tests were conducted on the chosen rock samples and acoustic emission (AE) sensors were used in some of them to monitor the fracturing process. Experimental tests indicated that brittleness strongly influences damage evolution of rocks in the course of static and dynamic loading. AE monitoring revealed that micro-crack density induced by the applied loads during different stages of the failure processes increases as rock brittleness increases. Also, results of fatigue tests on the three rock types indicated that the rock with the most induced micro-cracks during loading cycles has the least fatigue life. Furthermore, the condition of failure surfaces of the studied rocks samples, subjected to dynamic and static loading, were evaluated and it was concluded that the roughness of failure surfaces is influenced by loading types and rock brittleness. Dynamic failure surfaces were rougher than static ones and low brittle rock demonstrate a smoother failure surface compared to high brittle rock.

  15. Fracture Energy-Based Brittleness Index Development and Brittleness Quantification by Pre-peak Strength Parameters in Rock Uniaxial Compression

    NASA Astrophysics Data System (ADS)

    Munoz, H.; Taheri, A.; Chanda, E. K.

    2016-12-01

    Brittleness is a fundamental mechanical rock property critical to many civil engineering works, mining development projects and mineral exploration operations. However, rock brittleness is a concept yet to be investigated as there is not any unique criterion available, widely accepted by rock engineering community able to describe rock brittleness quantitatively. In this study, new brittleness indices were developed based on fracture strain energy quantities obtained from the complete stress-strain characteristics of rocks. In doing so, different rocks having unconfined compressive strength values ranging from 7 to 215 MPa were examined in a series of quasi-static uniaxial compression tests after properly implementing lateral-strain control in a closed-loop system to apply axial load to rock specimen. This testing method was essential to capture post-peak regime of the rocks since a combination of class I-II or class II behaviour featured post-peak stress-strain behaviour. Further analysis on the post-peak strain localisation, stress-strain characteristics and the fracture pattern causing class I-II and class II behaviour were undertaken by analysing the development of field of strains in the rocks via three-dimensional digital image correlation. Analysis of the results demonstrated that pre-peak stress-strain brittleness indices proposed solely based on pre-peak stress-strain behaviour do not show any correlation with any of pre-peak rock mechanical parameters. On the other hand, the proposed brittleness indices based on pre-peak and post-peak stress-strain relations were found to competently describe an unambiguous brittleness scale against rock deformation and strength parameters such as the elastic modulus, the crack damage stress and the peak stress relevant to represent failure process.

  16. On the brittleness of enamel and selected dental materials.

    PubMed

    Park, S; Quinn, J B; Romberg, E; Arola, D

    2008-11-01

    Although brittle material behavior is often considered undesirable, a quantitative measure of "brittleness" is currently not used in assessing the clinical merits of dental materials. To quantify and compare the brittleness of human enamel and common dental restorative materials used for crown replacement. Specimens of human enamel were prepared from the third molars of "young" (18< or =age< or =25) and "old" (50< or =age) patients. The hardness, elastic modulus and apparent fracture toughness were characterized as a function of distance from the DEJ using indentation approaches. These properties were then used in estimating the brittleness according to a model that accounts for the competing dissipative processes of deformation and fracture. The brittleness of selected porcelain, ceramic and micaceous glass ceramic (MGC) dental materials was estimated and compared with that of the enamel. The average brittleness of the young and old enamel increased with distance from the DEJ. For the old enamel the average brittleness increased from approximately 300 microm(-1) at the DEJ to nearly 900 microm(-1) at the occlusal surface. While there was no significant difference between the two age groups at the DEJ, the brittleness of the old enamel was significantly greater (and up to four times higher) than that of the young enamel near the occlusal surface. The brittleness numbers for the restorative materials were up to 90% lower than that of young occlusal enamel. The brittleness index could serve as a useful scale in the design of materials used for crown replacement, as well as a quantitative tool for characterizing degradation in the mechanical behavior of enamel.

  17. Testing Bonds Between Brittle And Ductile Films

    NASA Technical Reports Server (NTRS)

    Wheeler, Donald R.; Ohsaki, Hiroyuki

    1989-01-01

    Simple uniaxial strain test devised to measure intrinsic shear strength. Brittle film deposited on ductile stubstrate film, and combination stretched until brittle film cracks, then separates from substrate. Dimensions of cracked segments related in known way to tensile strength of brittle film and shear strength of bond between two films. Despite approximations and limitations of technique, tests show it yields semiquantitative measures of bond strengths, independent of mechanical properties of substrates, with results reproducible with plus or minus 6 percent.

  18. ON THE BRITTLENESS OF ENAMEL AND SELECTED DENTAL MATERIALS

    PubMed Central

    Park, S.; Quinn, J. B; Romberg, E.; Arola, D.

    2008-01-01

    Although brittle material behavior is often considered undesirable, a quantitative measure of “brittleness” is currently not used in assessing the clinical merits of dental materials. Objective To quantify and compare the brittleness of human enamel and common dental restorative materials used for crown replacement. Methods Specimens of human enamel were prepared from the 3rd molars of “young” (18≤age≤25) and “old” (50≤age) patients. The hardness, elastic modulus and apparent fracture toughness were characterized as a function of distance from the DEJ using indentation approaches. These properties were then used in estimating the brittleness according to a model that accounts for the competing dissipative processes of deformation and fracture. The brittleness of selected porcelain, ceramic and Micaceous Glass Ceramic (MGC) dental materials was estimated and compared with that of the enamel. Results The average brittleness of the young and old enamel increased with distance from the DEJ. For the old enamel the average brittleness increased from approximately 300 µm−1 at the DEJ to nearly 900 µm−1 at the occlusal surface. While there was no significant difference between the two age groups at the DEJ, the brittleness of the old enamel was significantly greater (and up to 4 times higher) than that of the young enamel near the occlusal surface. The brittleness numbers for the restorative materials were up to 90% lower than that of young occlusal enamel. Significance The brittleness index could serve as a useful scale in the design of materials used for crown replacement, as well as a quantitative tool for characterizing degradation in the mechanical behavior of enamel. PMID:18436299

  19. High Speed Dynamics in Brittle Materials

    NASA Astrophysics Data System (ADS)

    Hiermaier, Stefan

    2015-06-01

    Brittle Materials under High Speed and Shock loading provide a continuous challenge in experimental physics, analysis and numerical modelling, and consequently for engineering design. The dependence of damage and fracture processes on material-inherent length and time scales, the influence of defects, rate-dependent material properties and inertia effects on different scales make their understanding a true multi-scale problem. In addition, it is not uncommon that materials show a transition from ductile to brittle behavior when the loading rate is increased. A particular case is spallation, a brittle tensile failure induced by the interaction of stress waves leading to a sudden change from compressive to tensile loading states that can be invoked in various materials. This contribution highlights typical phenomena occurring when brittle materials are exposed to high loading rates in applications such as blast and impact on protective structures, or meteorite impact on geological materials. A short review on experimental methods that are used for dynamic characterization of brittle materials will be given. A close interaction of experimental analysis and numerical simulation has turned out to be very helpful in analyzing experimental results. For this purpose, adequate numerical methods are required. Cohesive zone models are one possible method for the analysis of brittle failure as long as some degree of tension is present. Their recent successful application for meso-mechanical simulations of concrete in Hopkinson-type spallation tests provides new insight into the dynamic failure process. Failure under compressive loading is a particular challenge for numerical simulations as it involves crushing of material which in turn influences stress states in other parts of a structure. On a continuum scale, it can be modeled using more or less complex plasticity models combined with failure surfaces, as will be demonstrated for ceramics. Models which take microstructural

  20. From brittle to ductile fracture in disordered materials.

    PubMed

    Picallo, Clara B; López, Juan M; Zapperi, Stefano; Alava, Mikko J

    2010-10-08

    We introduce a lattice model able to describe damage and yielding in heterogeneous materials ranging from brittle to ductile ones. Ductile fracture surfaces, obtained when the system breaks once the strain is completely localized, are shown to correspond to minimum energy surfaces. The similarity of the resulting fracture paths to the limits of brittle fracture or minimum energy surfaces is quantified. The model exhibits a smooth transition from brittleness to ductility. The dynamics of yielding exhibits avalanches with a power-law distribution.

  1. Identification of a Suitable 3D Printing Material for Mimicking Brittle and Hard Rocks and Its Brittleness Enhancements

    NASA Astrophysics Data System (ADS)

    Zhou, T.; Zhu, J. B.

    2018-03-01

    Three-dimensional printing (3DP) is a computer-controlled additive manufacturing technique which is able to repeatedly and accurately fabricate objects with complicated geometry and internal structures. After 30 years of fast development, 3DP has become a mainstream manufacturing process in various fields. This study focuses on identifying the most suitable 3DP material from five targeted available 3DP materials, i.e. ceramics, gypsum, PMMA (poly(methyl methacrylate)), SR20 (acrylic copolymer) and resin (Accura® 60), to simulate brittle and hard rocks. Firstly, uniaxial compression tests were performed to determine the mechanical properties and failure patterns of the 3DP samples fabricated by those five materials. Experimental results indicate that among current 3DP techniques, the resin produced via stereolithography (SLA) is the most suitable 3DP material for mimicking brittle and hard rocks, although its brittleness needs to be improved. Subsequently, three methods including freezing, incorporation of internal macro-crack and addition of micro-defects were adopted to enhance the brittleness of the 3DP resin, followed by uniaxial compression tests on the treated samples. Experimental results reveal that 3DP resin samples with the suggested treatments exhibited brittle properties and behaved similarly to natural rocks. Finally, some prospective improvements which can be used to facilitate the application of 3DP techniques to rock mechanics were also discussed. The findings of this paper could contribute to promoting the application of 3DP technique in rock mechanics.

  2. Phase-Transformation Ductilization of Brittle High-Entropy Alloys via Metastability Engineering

    DOE PAGES

    Huang, Hailong; Wu, Yuan; He, Junyang; ...

    2017-06-07

    High-entropy alloys (HEAs) in which interesting physical, chemical, and structural properties are being continuously revealed have recently attracted extensive attention. Body-centered cubic (bcc) HEAs, particularly those based on refractory elements are promising for high-temperature application but generally fail by early cracking with limited plasticity at room temperature, which limits their malleability and widespread uses. In this paper, the “metastability-engineering” strategy is exploited in brittle bcc HEAs via tailoring the stability of the constituent phases, and transformation-induced ductility and work-hardening capability are successfully achieved. Finally, this not only sheds new insights on the development of HEAs with excellent combination of strengthmore » and ductility, but also has great implications on overcoming the long-standing strength–ductility tradeoff of metallic materials in general.« less

  3. Phase-Transformation Ductilization of Brittle High-Entropy Alloys via Metastability Engineering

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huang, Hailong; Wu, Yuan; He, Junyang

    High-entropy alloys (HEAs) in which interesting physical, chemical, and structural properties are being continuously revealed have recently attracted extensive attention. Body-centered cubic (bcc) HEAs, particularly those based on refractory elements are promising for high-temperature application but generally fail by early cracking with limited plasticity at room temperature, which limits their malleability and widespread uses. In this paper, the “metastability-engineering” strategy is exploited in brittle bcc HEAs via tailoring the stability of the constituent phases, and transformation-induced ductility and work-hardening capability are successfully achieved. Finally, this not only sheds new insights on the development of HEAs with excellent combination of strengthmore » and ductility, but also has great implications on overcoming the long-standing strength–ductility tradeoff of metallic materials in general.« less

  4. Athermal brittle-to-ductile transition in amorphous solids.

    PubMed

    Dauchot, Olivier; Karmakar, Smarajit; Procaccia, Itamar; Zylberg, Jacques

    2011-10-01

    Brittle materials exhibit sharp dynamical fractures when meeting Griffith's criterion, whereas ductile materials blunt a sharp crack by plastic responses. Upon continuous pulling, ductile materials exhibit a necking instability that is dominated by a plastic flow. Usually one discusses the brittle to ductile transition as a function of increasing temperature. We introduce an athermal brittle to ductile transition as a function of the cutoff length of the interparticle potential. On the basis of extensive numerical simulations of the response to pulling the material boundaries at a constant speed we offer an explanation of the onset of ductility via the increase in the density of plastic modes as a function of the potential cutoff length. Finally we can resolve an old riddle: In experiments brittle materials can be strained under grip boundary conditions and exhibit a dynamic crack when cut with a sufficiently long initial slot. Mysteriously, in molecular dynamics simulations it appeared that cracks refused to propagate dynamically under grip boundary conditions, and continuous pulling was necessary to achieve fracture. We argue that this mystery is removed when one understands the distinction between brittle and ductile athermal amorphous materials.

  5. Deconvoluting complex structural histories archived in brittle fault zones

    NASA Astrophysics Data System (ADS)

    Viola, G.; Scheiber, T.; Fredin, O.; Zwingmann, H.; Margreth, A.; Knies, J.

    2016-11-01

    Brittle deformation can saturate the Earth's crust with faults and fractures in an apparently chaotic fashion. The details of brittle deformational histories and implications on, for example, seismotectonics and landscape, can thus be difficult to untangle. Fortunately, brittle faults archive subtle details of the stress and physical/chemical conditions at the time of initial strain localization and eventual subsequent slip(s). Hence, reading those archives offers the possibility to deconvolute protracted brittle deformation. Here we report K-Ar isotopic dating of synkinematic/authigenic illite coupled with structural analysis to illustrate an innovative approach to the high-resolution deconvolution of brittle faulting and fluid-driven alteration of a reactivated fault in western Norway. Permian extension preceded coaxial reactivation in the Jurassic and Early Cretaceous fluid-related alteration with pervasive clay authigenesis. This approach represents important progress towards time-constrained structural models, where illite characterization and K-Ar analysis are a fundamental tool to date faulting and alteration in crystalline rocks.

  6. Children with Brittle Bones.

    ERIC Educational Resources Information Center

    Alston, Jean

    1982-01-01

    Special help given to children with Osteogenesis Imperfecta (brittle bone disease) is described, including adapted equipment to allow for writing and use of a classroom assistant to aid participation in a regular classroom. (CL)

  7. Johanna and Tommy: Two Preschoolers in Sweden with Brittle Bones.

    ERIC Educational Resources Information Center

    Millde, Kristina; Brodin, Jane

    Information is presented for caregivers of Swedish children with osteogenesis imperfecta (brittle bones) and their families. Approximately five children with brittle bones are born in Sweden annually. Two main types of brittle bone disease have been identified: congenita and tarda. Typical symptoms include numerous and unexpected fractures, bluish…

  8. Brittle-to-Ductile Transition in Metallic Glass Nanowires.

    PubMed

    Şopu, D; Foroughi, A; Stoica, M; Eckert, J

    2016-07-13

    When reducing the size of metallic glass samples down to the nanoscale regime, experimental studies on the plasticity under uniaxial tension show a wide range of failure modes ranging from brittle to ductile ones. Simulations on the deformation behavior of nanoscaled metallic glasses report an unusual extended strain softening and are not able to reproduce the brittle-like fracture deformation as found in experiments. Using large-scale molecular dynamics simulations we provide an atomistic understanding of the deformation mechanisms of metallic glass nanowires and differentiate the extrinsic size effects and aspect ratio contribution to plasticity. A model for predicting the critical nanowire aspect ratio for the ductile-to-brittle transition is developed. Furthermore, the structure of brittle nanowires can be tuned to a softer phase characterized by a defective short-range order and an excess free volume upon systematic structural rejuvenation, leading to enhanced tensile ductility. The presented results shed light on the fundamental deformation mechanisms of nanoscaled metallic glasses and demarcate ductile and catastrophic failure.

  9. Estimation Criteria for Rock Brittleness Based on Energy Analysis During the Rupturing Process

    NASA Astrophysics Data System (ADS)

    Ai, Chi; Zhang, Jun; Li, Yu-wei; Zeng, Jia; Yang, Xin-liang; Wang, Ji-gang

    2016-12-01

    Brittleness is one of the most important mechanical properties of rock: it plays a significant role in evaluating the risk of rock bursts and in analysis of borehole-wall stability during shale gas development. Brittleness is also a critical parameter in the design of hydraulic fracturing. However, there is still no widely accepted definition of the concept of brittleness in rock mechanics. Although many criteria have been proposed to characterize rock brittleness, their applicability and reliability have yet to be verified. In this paper, the brittleness of rock under compression is defined as the ability of a rock to accumulate elastic energy during the pre-peak stage and to self-sustain fracture propagation in the post-peak stage. This ability is related to three types of energy: fracture energy, post-peak released energy and pre-peak dissipation energy. New brittleness evaluation indices B 1 and B 2 are proposed based on the stress-strain curve from the viewpoint of energy. The new indices can describe the entire transition of rock from absolute plasticity to absolute brittleness. In addition, the brittle characteristics reflected by other brittleness indices can be described, and the calculation results of B 1 and B 2 are continuous and monotonic. Triaxial compression tests on different types of rock were carried out under different confining pressures. Based on B 1 and B 2, the brittleness of different rocks shows different trends with rising confining pressure. The brittleness of red sandstone decreases with increasing confining pressure, whereas for black shale it initially increases and then decreases in a certain range of confining pressure. Granite displays a constant increasing trend. The brittleness anisotropy of black shale is discussed. The smaller the angle between the loading direction and the bedding plane, the greater the brittleness. The calculation B 1 and B 2 requires experimental data, and the values of these two indices represent only

  10. Dislocation dynamics modelling of the ductile-brittle-transition

    NASA Astrophysics Data System (ADS)

    Hennecke, Thomas; Hähner, Peter

    2009-07-01

    Many materials like silicon, tungsten or ferritic steels show a transition between high temperature ductile fracture with stable crack grow and high deformation energy absorption and low temperature brittle fracture in an unstable and low deformation mode, the ductile-brittle-transition. Especially in steels, the temperature transition is accompanied by a strong increase of the measured fracture toughness over a certain temperature range and strong scatter in the toughness data in this transition regime. The change in fracture modes is affected by dynamic interactions between dislocations and the inhomogeneous stress fields of notches and small cracks. In the present work a dislocation dynamics model for the ductile-brittle-transition is proposed, which takes those interactions into account. The model can explain an increase with temperature of apparent toughness in the quasi-brittle regime and different levels of scatter in the different temperature regimes. Furthermore it can predict changing failure sites in materials with heterogeneous microstructure. Based on the model, the effects of crack tip blunting, stress state, external strain rate and irradiation-induced changes in the plastic flow properties can be discussed.

  11. Temporary brittle bone disease: fractures in medical care.

    PubMed

    Paterson, Colin R

    2009-12-01

    Temporary brittle bone disease is the name given to a syndrome first reported in 1990, in which fractures occur in infants in the first year of life. The fractures include rib fractures and metaphyseal fractures which are mostly asymptomatic. The radiological features of this disorder mimic those often ascribed to typical non-accidental injury. The subject has been controversial, some authors suggesting that the disorder does not exist. This study reports five infants with typical features of temporary brittle bone disease in whom all or most of the fractures took place while in hospital. A non-accidental cause can be eliminated with some confidence, and these cases provide evidence in support of the existence of temporary brittle bone disease.

  12. The Brittle-Ductile Transition in Crystal and Bubble-bearing Magmas

    NASA Astrophysics Data System (ADS)

    Caricchi, L.; Pistone, M.; Cordonnier, B.; Tripoli, B.; Ulmer, P.; Reusser, E.; Marone, F.; Burlini, L.

    2011-12-01

    The strain response of magma is critically dependent upon its viscosity, the magnitude of the applied stress and the experimental time-scale. The brittle-ductile transition in pure silicate melts is expected for an applied stress approaching 108±0.5 Pa (Dingwell, 1997). However, magmas are mostly mixture of crystal and bubble-bearing silicate melts. To date, there are no data to constrain the ductile-brittle transition for three-phase magmas. Thus, we conducted consistent torsion experiments at high temperature (673-973 K) and high pressure (200 MPa), in the strain rate range 1*10-5-4*10-3 s-1, using a HT-HP internally-heated Paterson-type rock deformation apparatus. The samples are composed of hydrous haplogranitic glass, quartz crystals (24-65 vol%) and CO2-rich gas-pressurized bubbles (9-12 vol%). The applied strain rate was increased until brittle failure occurred; micro-fracturing and healing processes commonly occurred before sample macroscopic fracturing. The experimental results highlight a clear relationship between the effective viscosity of the three-phase magmas, strain rate, temperature and the onset of brittle-ductile behavior. Crystal- and bubble-free melts at high viscosity (1011-1011.6 Pa*s at 673 K) show brittle behavior in the strain rate range between 1*10-4 and 5*10-4 s-1. For comparable viscosities crystal and bubble-bearing magmas show a transition to brittle behavior at lower strain rates. Synchrotron-based 3D imaging of fractured samples, show the presence of fractures with an antithetic trend with respect to shear strain directions. The law found in this study expresses the transition from ductile to brittle behavior for real magmas and could significantly improve our understanding of the control of brittle processes on extrusion of high-viscosity magmas and degassing at silicic volcanoes.

  13. Mapping the ductile-brittle transition of magma

    NASA Astrophysics Data System (ADS)

    Kendrick, J. E.; Lavallee, Y.; Dingwell, D. B.

    2010-12-01

    During volcanic unrest, eruptive activity can switch rapidly from effusive to explosive. Explosive eruptions require the fragmentation of magma, in which, if deformation rate is too fast to be relaxed, magma undergoes a transition in deformation mechanism from viscous and/or ductile to brittle. Our knowledge of the deformation mechanisms of magma ascent and eruption remains, to date, poor. Many studies have constrained the glass transition (Tg) of the interstitial melt phase; yet the effect of crystals and bubbles are unresolved. During ascent, magma undergoes P-T changes which induce crystallization, thereby inducing a transition from viscous to ductile and, in some cases, to brittle deformation. Here, we explore the deformation mechanisms of magma involved in the dome-building eruptions and explosions that occurred at Volcán de Colima (Mexico) since 1998. For this purpose, we investigated the rheology of dome lavas, containing 10-45 vol.% rhyolitic interstitial melt, 55-90 vol.% crystals and 5-20 vol.% bubbles. The interstitial glass is characterized by electron microprobe and Tg is characterized using a differential scanning calorimeter and a dilatometer. The population of crystals (fraction, shape and size distribution) is described optically and quantified using ImageJ and AMOCADO. The rheological effects of crystals on the deformation of magmas are constrained via acoustic emission (AE) and uniaxial deformation experiments at temperature above Tg (900-980 °C) and at varied applied stresses (and strain rates: 10-6 to 10-2 s-1). The ratio of ductile to brittle deformation across the ductile-brittle transition is quantified using the output AE energy and optical and SEM analysis. We find that individual dome lava sample types have different mechanical responses, yielding a significant range of measured strain rates under a given temperature and applied stress. Optical analysis suggests that at low strain rates, ductile deformation is mainly controlled by the

  14. Brittle Splitting Nails (Onychoschizia)

    MedlinePlus

    ... more common in women. Only very rarely are internal disease or vitamin deficiencies the reason (iron deficiency is the most common). One tip is that if the fingernails split, but the toenails are strong, then an external factor is the cause. Basically brittle nails can be ...

  15. Hypervelocity impact and dynamic fragmentation of brittle materials

    NASA Astrophysics Data System (ADS)

    Agrawal, Vinamra; Ortega, Alejandro; Meiron, Daniel

    2017-06-01

    The process of hypervelocity impact and dynamic fragmentation finds application in planetary formation, satellite design for micrometeorite impact damage mitigation, armor design and crater formations. In this work, we study high velocity impact induced dynamic fragmentation processes of brittle materials. We implement ideas of Continuum Damage Mechanics (CDM) to perform fragmentation simulations on brittle materials in various geometries. The damage formulation was implemented on an existing computational framework capable of adaptive mesh refinement that operates on an Eulerian grid, thereby avoiding problems associated with grid entanglement in large deformation processes. A damage sensitive equation of state is developed for hyperelastic materials that depends on a damage variable D, the volume fraction of micro-cracks in the brittle material. The evolution of D is governed by a modified, thermodynamically consistent Grady-Kipp model that evolves damage at points of tensile eigenvalue stresses. We simulate sphere-on-sphere and sphere-on-plate impact events with ductile and brittle materials and study the resulting damage propagation. We validate our calculations with existing literature and comment on energy dissipation and optimal design. Caltech - JPL President's and Director's Fund.

  16. Evaluation of the Cytotoxic Effect of the Brittle Star (Ophiocoma Erinaceus) Dichloromethane Extract and Doxorubicin on EL4 Cell Line.

    PubMed

    Afzali, Mahbubeh; Baharara, Javad; Nezhad Shahrokhabadi, Khadijeh; Amini, Elaheh

    2017-01-01

    Leukemia is a blood disease that creates from inhibition of differentiation and increased proliferation rate. The nature has been known as a rich source of medically useful substances. High diversity of bioactive molecules, extracted from marine invertebrates, makes them as ideal candidates for cancer research. The study has been done to investigate cytotoxic effects of dichloromethane brittle star extract and doxorubicin on EL4 cancer cells. Blood cancer EL4 cells were cultured and treated at different concentrations of brittle star ( Ophiocoma erinaceus ) dichloromethane extract at 24, 48 and 72 h. Cell toxicity was studied using MTT assay. Cell morphology was examined using an invert microscope. Further, apoptosis was examined using Annexin V-FITC, propodium iodide, DAPI, and Acridine orange/propodium iodide staining. Eventually, the apoptosis pathways were analyzed using measurement of Caspase-3 and -9 activity. The statistical analysis was performed using SPSS, ANOVA software, and Tukey's test. P <0.05 was considered to be significant. MTT assay and morphological observations showed that dichloromethane extract can inhibit cell growth in a dose dependent. The results considered 32 µg/mL of the extract as IC 50 . Also, doxorubicin suppressed EL4 proliferation as IC 50 =32 µg/mL. All experiments related to apoptosis analysis confirmed that dichloromethane brittle star extract and doxorubicin have a cytotoxic effect on EL4 cells inIC 50 concentration. The study showed that dichloromethane brittle star extract is as an adjunct to doxorubicin in treatment of leukemia cells.

  17. Experimental demonstration of a semi-brittle origin for crustal strain transients

    NASA Astrophysics Data System (ADS)

    Reber, J. E.; Lavier, L. L.; Hayman, N. W.

    2015-12-01

    Tectonic motions that give rise to destructive earthquakes and enigmatic transient slip events are commonly explained by friction laws that describe slip on fault surfaces and gouge-filled zones. Friction laws with the added effects of pore fluid pressure, shear heating, and chemical reactions as currently applied do not take into account that over a wide range of pressure and temperature conditions rocks deform following a complex mixed brittle-ductile rheology. In semi-brittle materials, such as polymineralic rocks, elasto-plastic and visco-elastic defamation can be observed simultaneously in different phases of the material. Field observations of such semi-brittle rocks at the mesoscale have shown that for a given range of composition, temperature, and pressure, the formation of fluid-filled brittle fractures and veins can precede and accompany the development of localized ductile flow. We propose that the coexistence of brittle and viscous behavior controls some of the physical characteristics of strain transients and slow slip events. Here we present results from shear experiments on semi-brittle rock analogues investigating the effect of yield stress on fracture propagation and connection, and how this can lead to reoccurring strain transients. During the experiments we monitor the evolution of fractures and flow as well as the force development in the system. We show that the nature of localized slip and flow in semi-brittle materials depends on the initiation and formation of mode I and II fractures and does not involve frictional behavior, supporting an alternative mechanism for the development of tectonic strain transients.

  18. Award-Winning CARES/Life Ceramics Durability Evaluation Software Is Making Advanced Technology Accessible

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Products made from advanced ceramics show great promise for revolutionizing aerospace and terrestrial propulsion and power generation. However, ceramic components are difficult to design because brittle materials in general have widely varying strength values. The CARES/Life software developed at the NASA Lewis Research Center eases this by providing a tool that uses probabilistic reliability analysis techniques to optimize the design and manufacture of brittle material components. CARES/Life is an integrated package that predicts the probability of a monolithic ceramic component's failure as a function of its time in service. It couples commercial finite element programs--which resolve a component's temperature and stress distribution - with reliability evaluation and fracture mechanics routines for modeling strength - limiting defects. These routines are based on calculations of the probabilistic nature of the brittle material's strength.

  19. Forced tearing of ductile and brittle thin sheets.

    PubMed

    Tallinen, T; Mahadevan, L

    2011-12-09

    Tearing a thin sheet by forcing a rigid object through it leads to complex crack morphologies; a single oscillatory crack arises when a tool is driven laterally through a brittle sheet, while two diverging cracks and a series of concertinalike folds forms when a tool is forced laterally through a ductile sheet. On the other hand, forcing an object perpendicularly through the sheet leads to radial petallike tears in both ductile and brittle materials. To understand these different regimes we use a combination of experiments, simulations, and simple theories. In particular, we describe the transition from brittle oscillatory tearing via a single crack to ductile concertina tearing with two tears by deriving laws that describe the crack paths and wavelength of the concertina folds and provide a simple phase diagram for the morphologies in terms of the material properties of the sheet and the relative size of the tool.

  20. Meshless modelling of dynamic behaviour of glasses under intense shock loadings: Application to matter ejection during high velocity impacts on thin brittle targets

    NASA Astrophysics Data System (ADS)

    Michel, Y.; Chevalier, J.-M.; Durin, C.; Espinosa, C.; Malaise, F.; Barrau, J.-J.

    2006-08-01

    The purpose of this study is to present a new material model adapted to SPH modelling of dynamic behaviour of glasses under shock loadings. This model has the ability to reproduce fragmentation and densification of glasses under compression as well as brittle tensile failure. It has been implemented in Ls-Dyna software and coupled with a SPH code. By comparison with CEA-CESTA experimental data the model has been validated for fused silica and Pyrex glass for stress level up to 35GPa. For Laser MegaJoule applications, the present material model was applied to 3D high velocity impacts on thin brittle targets with good agreement with experimental data obtained using CESTA's double stage light gas gun in term of damages and matter ejection.

  1. Fabrication of brittle materials -- current status

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Scattergood, R.O.

    The research initiatives in the area of precision fabrication will be continued in the upcoming year. Three students, T. Bifano (PhD), P. Blake (PhD) and E. Smith (MS), finished their research programs in the last year. Sections 13 and 14 will summarize the essential results from the work of the Materials Engineering students Blake and Smith. Further details will be presented in forthcoming publications that are now in preparation. The results from Bifano`s thesis have been published in adequate detail and need not be summarized further. Three new students, S. Blackley (MS), H. Paul (PhD), and S. Smith (PhD) havemore » joined the program and will continue the research efforts in precision fabrication. The programs for these students will be outlined in Sections 15 and 16. Because of the success of the earlier work in establishing new process models and experimental techniques for the study of diamond turning and diamond grinding, the new programs will, in part, build upon the earlier work. This is especially true for investigations concerned with brittle materials. The basic understanding of material response of nominally brittle materials during machining or grinding operations remains as a challenge. The precision fabrication of brittle materials will continue as an area of emphasis for the Precision Engineering Center.« less

  2. Experimental analysis and application of the effect of stress on continental shale reservoir brittleness

    NASA Astrophysics Data System (ADS)

    Yin, Shuai; Lv, Dawei; Jin, Lin; Ding, Wenlong

    2018-04-01

    Hydraulic fracturing is an effective measure of reservoir modification for the development of shale gas. The evaluation of rock brittleness can provide a basis for the optimization of fracturing. In this paper, the effect of stress on the brittleness of shale is systematically analyzed by designing triaxial mechanics tests. The strain analysis method was used to evaluate the shale brittleness. The research indicates that, with the increase of effective confining pressure, the value of the brittleness index (B 1) decreases. There is a linear and positive correlation between the average reduction ratio of B 1 and the buried depth. The stress has a significant effect on the shale brittleness. Therefore, the rock brittleness can be overestimated without considering the influence of the buried depth or the stress of formation when using the mineral composition method. Being affected by the stress, when the brittle mineral content of the shale reservoir is 70%, 65%, 60%, and 55%, the lower limit depth of the shale gas development is 5000 m, 4400 m, 3000 m, and 1800 m, respectively. However, when the brittle mineral content of the shale is less than 50%, the brittleness index is less than 50% in all of the buried depths. In this case, the shale will not have any commercial development potential. The logging interpretation results of the brittleness index conducted with stress correction are more consistent with the real situation, and thus, this method can be better used to help the optimization of the fracturing intervals of shale gas.

  3. Cuttability Assessment of Selected Rocks Through Different Brittleness Values

    NASA Astrophysics Data System (ADS)

    Dursun, Arif Emre; Gokay, M. Kemal

    2016-04-01

    Prediction of cuttability is a critical issue for successful execution of tunnel or mining excavation projects. Rock cuttability is also used to determine specific energy, which is defined as the work done by the cutting force to excavate a unit volume of yield. Specific energy is a meaningful inverse measure of cutting efficiency, since it simply states how much energy must be expended to excavate a unit volume of rock. Brittleness is a fundamental rock property and applied in drilling and rock excavation. Brittleness is one of the most crucial rock features for rock excavation. For this reason, determination of relations between cuttability and brittleness will help rock engineers. This study aims to estimate the specific energy from different brittleness values of rocks by means of simple and multiple regression analyses. In this study, rock cutting, rock property, and brittleness index tests were carried out on 24 different rock samples with different strength values, including marble, travertine, and tuff, collected from sites around Konya Province, Turkey. Four previously used brittleness concepts were evaluated in this study, denoted as B 1 (ratio of compressive to tensile strength), B 2 (ratio of the difference between compressive and tensile strength to the sum of compressive and tensile strength), B 3 (area under the stress-strain line in relation to compressive and tensile strength), and B 9 = S 20, the percentage of fines (<11.2 mm) formed in an impact test for the Norwegian University of Science and Technology (NTNU) model as well as B 9p (B 9 as predicted from uniaxial compressive, Brazilian tensile, and point load strengths of rocks using multiple regression analysis). The results suggest that the proposed simple regression-based prediction models including B 3, B 9, and B 9p outperform the other models including B 1 and B 2 and can be used for more accurate and reliable estimation of specific energy.

  4. Impact fragmentation of a brittle metal compact

    NASA Astrophysics Data System (ADS)

    Tang, Megan; Hooper, Joseph P.

    2018-05-01

    The fragmentation behavior of a metal powder compact which is ductile in compression but brittle in tension is studied via impact experiments and analytical models. Consolidated metal compacts were prepared via cold-isostatic pressing of <10 μm zinc powder at 380 MPa followed by moderate annealing at 365 °C. The resulting zinc material is ductile and strain-hardening in high-rate uniaxial compression like a traditional metal, but is elastic-brittle in tension with a fracture toughness comparable to a ceramic. Cylindrical samples were launched up to 800 m/s in a gas gun into thin aluminum perforation targets, subjecting the projectile to a complex multiaxial and time-dependent stress state that leads to catastrophic fracture. A soft-catch mechanism using low-density artificial snow was developed to recover the impact debris, and collected fragments were analyzed to determine their size distribution down to 30 μm. Though brittle fracture occurs along original particle boundaries, no power-law fragmentation behavior was observed as is seen in other low-toughness materials. An analytical theory is developed to predict the characteristic fragment size accounting for both the sharp onset of fragmentation and the effect of increasing impact velocity.

  5. The nature of temper brittleness of high-chromium ferrite

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sarrak, V.I.; Suvorova, S.O.; Golovin, I.S.

    The reasons for development of {open_quotes}475{degrees}C brittleness{close_quotes} of high-chromium ferritic steels are considered from the standpoint of fracture mechanics. It is shown that the general rise in the curve of temperature-dependent local flow stress has the decisive influence on the position of the ductile-to-brittle transformation temperature and the increase in it as the result of a hold at temperatures of development of brittleness. The established effect is related to the change in the parameters determining dislocation mobility, that is, the activation energy of dislocation movement in high-chromium ferrite and the resistance to microplastic deformation, both caused by processes of separationmore » into layers of high-chromium ferrite and decomposition of the interstitial solid solution.« less

  6. Evaluation of the Cytotoxic Effect of the Brittle Star (Ophiocoma Erinaceus) Dichloromethane Extract and Doxorubicin on EL4 Cell Line

    PubMed Central

    Afzali, Mahbubeh; Baharara, Javad; Nezhad Shahrokhabadi, Khadijeh; Amini, Elaheh

    2017-01-01

    Leukemia is a blood disease that creates from inhibition of differentiation and increased proliferation rate. The nature has been known as a rich source of medically useful substances. High diversity of bioactive molecules, extracted from marine invertebrates, makes them as ideal candidates for cancer research. The study has been done to investigate cytotoxic effects of dichloromethane brittle star extract and doxorubicin on EL4 cancer cells. Blood cancer EL4 cells were cultured and treated at different concentrations of brittle star (Ophiocoma erinaceus) dichloromethane extract at 24, 48 and 72 h. Cell toxicity was studied using MTT assay. Cell morphology was examined using an invert microscope. Further, apoptosis was examined using Annexin V-FITC, propodium iodide, DAPI, and Acridine orange/propodium iodide staining. Eventually, the apoptosis pathways were analyzed using measurement of Caspase-3 and -9 activity. The statistical analysis was performed using SPSS, ANOVA software, and Tukey’s test. P<0.05 was considered to be significant. MTT assay and morphological observations showed that dichloromethane extract can inhibit cell growth in a dose dependent. The results considered 32 µg/mL of the extract as IC50. Also, doxorubicin suppressed EL4 proliferation as IC50=32 µg/mL. All experiments related to apoptosis analysis confirmed that dichloromethane brittle star extract and doxorubicin have a cytotoxic effect on EL4 cells inIC50 concentration. The study showed that dichloromethane brittle star extract is as an adjunct to doxorubicin in treatment of leukemia cells. PMID:29844793

  7. Brittle materials at high-loading rates: an open area of research

    NASA Astrophysics Data System (ADS)

    Forquin, Pascal

    2017-01-01

    Brittle materials are extensively used in many civil and military applications involving high-strain-rate loadings such as: blasting or percussive drilling of rocks, ballistic impact against ceramic armour or transparent windshields, plastic explosives used to damage or destroy concrete structures, soft or hard impacts against concrete structures and so on. With all of these applications, brittle materials are subjected to intense loadings characterized by medium to extremely high strain rates (few tens to several tens of thousands per second) leading to extreme and/or specific damage modes such as multiple fragmentation, dynamic cracking, pore collapse, shearing, mode II fracturing and/or microplasticity mechanisms in the material. Additionally, brittle materials exhibit complex features such as a strong strain-rate sensitivity and confining pressure sensitivity that justify expending greater research efforts to understand these complex features. Currently, the most popular dynamic testing techniques used for this are based on the use of split Hopkinson pressure bar methodologies and/or plate-impact testing methods. However, these methods do have some critical limitations and drawbacks when used to investigate the behaviour of brittle materials at high loading rates. The present theme issue of Philosophical Transactions A provides an overview of the latest experimental methods and numerical tools that are currently being developed to investigate the behaviour of brittle materials at high loading rates. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

  8. Brittle materials at high-loading rates: an open area of research

    PubMed Central

    2017-01-01

    Brittle materials are extensively used in many civil and military applications involving high-strain-rate loadings such as: blasting or percussive drilling of rocks, ballistic impact against ceramic armour or transparent windshields, plastic explosives used to damage or destroy concrete structures, soft or hard impacts against concrete structures and so on. With all of these applications, brittle materials are subjected to intense loadings characterized by medium to extremely high strain rates (few tens to several tens of thousands per second) leading to extreme and/or specific damage modes such as multiple fragmentation, dynamic cracking, pore collapse, shearing, mode II fracturing and/or microplasticity mechanisms in the material. Additionally, brittle materials exhibit complex features such as a strong strain-rate sensitivity and confining pressure sensitivity that justify expending greater research efforts to understand these complex features. Currently, the most popular dynamic testing techniques used for this are based on the use of split Hopkinson pressure bar methodologies and/or plate-impact testing methods. However, these methods do have some critical limitations and drawbacks when used to investigate the behaviour of brittle materials at high loading rates. The present theme issue of Philosophical Transactions A provides an overview of the latest experimental methods and numerical tools that are currently being developed to investigate the behaviour of brittle materials at high loading rates. This article is part of the themed issue ‘Experimental testing and modelling of brittle materials at high strain rates’. PMID:27956517

  9. Brittle materials at high-loading rates: an open area of research.

    PubMed

    Forquin, Pascal

    2017-01-28

    Brittle materials are extensively used in many civil and military applications involving high-strain-rate loadings such as: blasting or percussive drilling of rocks, ballistic impact against ceramic armour or transparent windshields, plastic explosives used to damage or destroy concrete structures, soft or hard impacts against concrete structures and so on. With all of these applications, brittle materials are subjected to intense loadings characterized by medium to extremely high strain rates (few tens to several tens of thousands per second) leading to extreme and/or specific damage modes such as multiple fragmentation, dynamic cracking, pore collapse, shearing, mode II fracturing and/or microplasticity mechanisms in the material. Additionally, brittle materials exhibit complex features such as a strong strain-rate sensitivity and confining pressure sensitivity that justify expending greater research efforts to understand these complex features. Currently, the most popular dynamic testing techniques used for this are based on the use of split Hopkinson pressure bar methodologies and/or plate-impact testing methods. However, these methods do have some critical limitations and drawbacks when used to investigate the behaviour of brittle materials at high loading rates. The present theme issue of Philosophical Transactions A provides an overview of the latest experimental methods and numerical tools that are currently being developed to investigate the behaviour of brittle materials at high loading rates.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'. © 2016 The Author(s).

  10. Computer-aided analysis of cutting processes for brittle materials

    NASA Astrophysics Data System (ADS)

    Ogorodnikov, A. I.; Tikhonov, I. N.

    2017-12-01

    This paper is focused on 3D computer simulation of cutting processes for brittle materials and silicon wafers. Computer-aided analysis of wafer scribing and dicing is carried out with the use of the ANSYS CAE (computer-aided engineering) software, and a parametric model of the processes is created by means of the internal ANSYS APDL programming language. Different types of tool tip geometry are analyzed to obtain internal stresses, such as a four-sided pyramid with an included angle of 120° and a tool inclination angle to the normal axis of 15°. The quality of the workpieces after cutting is studied by optical microscopy to verify the FE (finite-element) model. The disruption of the material structure during scribing occurs near the scratch and propagates into the wafer or over its surface at a short range. The deformation area along the scratch looks like a ragged band, but the stress width is rather low. The theory of cutting brittle semiconductor and optical materials is developed on the basis of the advanced theory of metal turning. The fall of stress intensity along the normal on the way from the tip point to the scribe line can be predicted using the developed theory and with the verified FE model. The crystal quality and dimensions of defects are determined by the mechanics of scratching, which depends on the shape of the diamond tip, the scratching direction, the velocity of the cutting tool and applied force loads. The disunity is a rate-sensitive process, and it depends on the cutting thickness. The application of numerical techniques, such as FE analysis, to cutting problems enhances understanding and promotes the further development of existing machining technologies.

  11. Challenges in the Japan Beyond-Brittle Project (JBBP) for EGS development beyond the brittle-ductile transition

    NASA Astrophysics Data System (ADS)

    Asanuma, H.; Muraoka, H.; Tsuchiya, N.; Ito, H.

    2013-12-01

    Development using Engineered Geothermal System (EGS) technologies is considered to be the best solution to the problems of the localized distribution of geothermal resources. However, it is considered that a number of problems, including low water recovery rate, difficulty in design of the reservoir, and induced earthquake, would appear in Japanese EGS. These problems in the development of EGS reservoirs cannot be readily solved in Japan because they are intrinsically related to the physical characteristics and tectonic setting of the brittle rock mass. Therefore, we have initiated the Japan Beyond-Brittle Project (JBBP), which will take a multidisciplinary scientific approach, including geology, geochemistry, geophysics, water-rock interactions, rock mechanics, seismology, drilling technology, well-logging technology, and reservoir engineering. The science and technology required for the creation and control of geothermal reservoirs in superheated rocks in the ductile zone is at the frontier of modern research in most of the related disciplines. Solutions to the associated problems will not easily be found without international collaboration among researchers and engineers. For this reason, in March, 2013 we held a five-day ICDP-supported workshop in Japan to review and discuss various scientific and technological issues related to the JBBP. Throughout the discussions at the workshop on characteristics of the beyond-brittle rock mass and creation and control of EGS reservoirs in the ductile zone, it has concluded that there are two end-member reservoir models that should be considered (Fig. 1). The JBBP reservoir type-1 would be created near the top of the brittle-ductile transition (BDT) and connected to pre-existing hydrothermal systems, which would increase productivity and provide sustainability. The JBBP reservoir type-2 would be hydraulically or thermally created beyond the BDT, where pre-existing fractures are less permeable, and would be hydraulically

  12. Advances in molecular dynamics simulation of ultra-precision machining of hard and brittle materials

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoguang; Li, Qiang; Liu, Tao; Kang, Renke; Jin, Zhuji; Guo, Dongming

    2017-03-01

    Hard and brittle materials, such as silicon, SiC, and optical glasses, are widely used in aerospace, military, integrated circuit, and other fields because of their excellent physical and chemical properties. However, these materials display poor machinability because of their hard and brittle properties. Damages such as surface micro-crack and subsurface damage often occur during machining of hard and brittle materials. Ultra-precision machining is widely used in processing hard and brittle materials to obtain nanoscale machining quality. However, the theoretical mechanism underlying this method remains unclear. This paper provides a review of present research on the molecular dynamics simulation of ultra-precision machining of hard and brittle materials. The future trends in this field are also discussed.

  13. Finite element model for brittle fracture and fragmentation

    DOE PAGES

    Li, Wei; Delaney, Tristan J.; Jiao, Xiangmin; ...

    2016-06-01

    A new computational model for brittle fracture and fragmentation has been developed based on finite element analysis of non-linear elasticity equations. The proposed model propagates the cracks by splitting the mesh nodes alongside the most over-strained edges based on the principal direction of strain tensor. To prevent elements from overlapping and folding under large deformations, robust geometrical constraints using the method of Lagrange multipliers have been incorporated. In conclusion, the model has been applied to 2D simulations of the formation and propagation of cracks in brittle materials, and the fracture and fragmentation of stretched and compressed materials.

  14. Finite element model for brittle fracture and fragmentation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Wei; Delaney, Tristan J.; Jiao, Xiangmin

    A new computational model for brittle fracture and fragmentation has been developed based on finite element analysis of non-linear elasticity equations. The proposed model propagates the cracks by splitting the mesh nodes alongside the most over-strained edges based on the principal direction of strain tensor. To prevent elements from overlapping and folding under large deformations, robust geometrical constraints using the method of Lagrange multipliers have been incorporated. In conclusion, the model has been applied to 2D simulations of the formation and propagation of cracks in brittle materials, and the fracture and fragmentation of stretched and compressed materials.

  15. Polarization Raman spectroscopy to explain rodent models of brittle bone

    NASA Astrophysics Data System (ADS)

    Makowski, Alexander J.; Nyman, Jeffry S.; Mahadevan-Jansen, Anita

    2013-03-01

    Activation Transcription Factor 4 (Atf-4) is essential for osteoblast maturation and proper collagen synthesis. We recently found that these bones demonstrate a rare brittleness phenotype, which is independent of bone strength. We utilized a confocal Renishaw Raman microscope (50x objective; NA=.75) to evaluate embedded, polished cross-sections of mouse tibia from both wild-type and knockout mice at 8 weeks of age (24 mice, n<=8 per group). Analysis of peak ratios indicated statistically significant changes in both mineral and collagen; however, compositional changes did not fully encompass biomechanical differences. To investigate the impact of material organization, we acquired colocalized spectra aligning the polarization angle parallel and perpendicular to the long bone axis from wet intact femurs. To validate our results, we used MMP9-/- mice, which have a brittleness phenotype that is not explained by compositional Raman measures. Polarization angle difference spectra show marked significant changes in orientation of these compositional differences when comparing wild type to knockout bones. Relative to wild-type, Atf4 -/- and MMP9 -/- bones show significant differences (t-test; p<0.05) in prominent collagen peaks. Further investigation of known peak ratios illustrates that this physical anisotropy of molecular organization is tightly clustered in brittle knockout bones. Such findings could have alternate interpretations about net collagen orientation or the angular distribution of collagen molecules. Use of polarization specific Raman measurements has implicated a structural profile that furthers our understanding of models of bone brittleness. Polarization content of Raman spectra may prove significant in future studies of brittle fracture and human fracture risk.

  16. Long Esophageal Stricture in a Brittle Diabetic

    PubMed Central

    Darr, Umar; Alastal, Yaseen; Yoon, Youngsook

    2017-01-01

    Aim: We report a case of atypical esophageal stricture in a young diabetic woman. Background: Diabetes mellitus and gastroesophageal reflux disease (GERD) are two common disorders in modern society. Case report: A young diabetic woman developed a 6-cm-long esophageal stricture. This stricture was refractory to multiple esophageal dilation procedures. She underwent subtotal esophagectomy and had excellent treatment outcome. Conclusion: Gastroesophageal reflux disease can cause severe long esophageal stricture in a brittle diabetic. Clinical significance: Improving the awareness of their association between diabetes and GERD would greatly benefit the day-to-day practice of medicine. How to cite this article: Pak SC, Darr U, Alastal Y, Yoon Y. Long Esophageal Stricture in a Brittle Diabetic. Euroasian J Hepato-Gastroenterol 2017;7(2):191-192. PMID:29201809

  17. Method for preparing surfaces of metal composites having a brittle phase for plating

    DOEpatents

    Coates, Cameron W.; Wilson, Thomas J.

    1984-01-01

    The present invention is directed to a method for preparing surfaces of two-phase metal composites having relatively brittle and malleable components for plating with corrosion-resistant material. In practice of the present invention, the surfaces of the composites are etched to remove a major portion or fraction of the brittle component. The etched surface is then peened with particulates for breaking the brittle component from the surfaces and for spreading or smearing the malleable component over the surfaces. The peened surface is then chemically cleaned of residual traces of the brittle component so as to provide a surface of essentially the malleable component to which the corrosion-resistant material may be plated thereon in an adherent manner.

  18. Micromechanical constitutive model for low-temperature constant strain rate deformation of limestones in the brittle and semi-brittle regime

    NASA Astrophysics Data System (ADS)

    Nicolas, A.; Fortin, J.; Guéguen, Y.

    2017-10-01

    Deformation and failure of rocks are important for a better understanding of many crustal geological phenomena such as faulting and compaction. In carbonate rocks among others, low-temperature deformation can either occur with dilatancy or compaction, having implications for porosity changes, failure and petrophysical properties. Hence, a thorough understanding of all the micromechanisms responsible for deformation is of great interest. In this study, a constitutive model for the low-temperature deformation of low-porosity (<20 per cent) carbonate rocks is derived from the micromechanisms identified in previous studies. The micromechanical model is based on (1) brittle crack propagation, (2) a plasticity law (interpreted in terms of dislocation glide without possibility to climb) for porous media with hardening and (3) crack nucleation due to dislocation pile-ups. The model predicts stress-strain relations and the evolution of damage during deformation. The model adequately predicts brittle behaviour at low confining pressures, which switches to a semi-brittle behaviour characterized by inelastic compaction followed by dilatancy at higher confining pressures. Model predictions are compared to experimental results from previous studies and are found to be in close agreement with experimental results. This suggests that microphysical phenomena responsible for the deformation are sufficiently well captured by the model although twinning, recovery and cataclasis are not considered. The porosity range of applicability and limits of the model are discussed.

  19. Testing Scientific Software: A Systematic Literature Review

    PubMed Central

    Kanewala, Upulee; Bieman, James M.

    2014-01-01

    Context Scientific software plays an important role in critical decision making, for example making weather predictions based on climate models, and computation of evidence for research publications. Recently, scientists have had to retract publications due to errors caused by software faults. Systematic testing can identify such faults in code. Objective This study aims to identify specific challenges, proposed solutions, and unsolved problems faced when testing scientific software. Method We conducted a systematic literature survey to identify and analyze relevant literature. We identified 62 studies that provided relevant information about testing scientific software. Results We found that challenges faced when testing scientific software fall into two main categories: (1) testing challenges that occur due to characteristics of scientific software such as oracle problems and (2) testing challenges that occur due to cultural differences between scientists and the software engineering community such as viewing the code and the model that it implements as inseparable entities. In addition, we identified methods to potentially overcome these challenges and their limitations. Finally we describe unsolved challenges and how software engineering researchers and practitioners can help to overcome them. Conclusions Scientific software presents special challenges for testing. Specifically, cultural differences between scientist developers and software engineers, along with the characteristics of the scientific software make testing more difficult. Existing techniques such as code clone detection can help to improve the testing process. Software engineers should consider special challenges posed by scientific software such as oracle problems when developing testing techniques. PMID:25125798

  20. Testing Scientific Software: A Systematic Literature Review.

    PubMed

    Kanewala, Upulee; Bieman, James M

    2014-10-01

    Scientific software plays an important role in critical decision making, for example making weather predictions based on climate models, and computation of evidence for research publications. Recently, scientists have had to retract publications due to errors caused by software faults. Systematic testing can identify such faults in code. This study aims to identify specific challenges, proposed solutions, and unsolved problems faced when testing scientific software. We conducted a systematic literature survey to identify and analyze relevant literature. We identified 62 studies that provided relevant information about testing scientific software. We found that challenges faced when testing scientific software fall into two main categories: (1) testing challenges that occur due to characteristics of scientific software such as oracle problems and (2) testing challenges that occur due to cultural differences between scientists and the software engineering community such as viewing the code and the model that it implements as inseparable entities. In addition, we identified methods to potentially overcome these challenges and their limitations. Finally we describe unsolved challenges and how software engineering researchers and practitioners can help to overcome them. Scientific software presents special challenges for testing. Specifically, cultural differences between scientist developers and software engineers, along with the characteristics of the scientific software make testing more difficult. Existing techniques such as code clone detection can help to improve the testing process. Software engineers should consider special challenges posed by scientific software such as oracle problems when developing testing techniques.

  1. Brittleness of twig bases in the genus Salix: fracture mechanics and ecological relevance.

    PubMed

    Beismann, H; Wilhelmi, H; Baillères, H; Spatz, H C; Bogenrieder, A; Speck, T

    2000-03-01

    The twig bases within the genus Salix were investigated. Brittleness of twig bases as defined in the literature neither correlates with Young's modulus nor with growth strains, which were measured for S. alba, S. fragilis and S. x rubens. For the species S. alba, S. appendiculata, S. eleagnos, S. fragilis, S. purpurea, S. triandra, S. viminalis, and S. x rubens, fracture surfaces of broken twigs were investigated and semiquantitatively described in terms of 'relative roughness' (ratio of rough area of fracture surface over whole area of fracture surface). The relative roughness clearly corresponds with the classification into brittle and nonbrittle species given in the literature. An attempt was made to quantify brittleness with mechanical tests. The absolute values of stress and strain do not correlate with the brittleness of the twig bases as defined by the relative roughness. However, the 'index stress' (ratio of stress at yield over stress at fracture) or the 'index strain' (ratio of strain at yield over strain at fracture), correlate well with the relative roughness. The graphic analysis of index stress against index strain reveals a straight line on which the eight species are ordered according to their brittleness. Depending on growth form and habitat, brittle twig bases of willows may function ecologically as mechanical safety mechanisms and, additionally, as a propagation mechanism.

  2. Ductile and brittle transition behavior of titanium alloys in ultra-precision machining.

    PubMed

    Yip, W S; To, S

    2018-03-02

    Titanium alloys are extensively applied in biomedical industries due to their excellent material properties. However, they are recognized as difficult to cut materials due to their low thermal conductivity, which induces a complexity to their deformation mechanisms and restricts precise productions. This paper presents a new observation about the removal regime of titanium alloys. The experimental results, including the chip formation, thrust force signal and surface profile, showed that there was a critical cutting distance to achieve better surface integrity of machined surface. The machined areas with better surface roughness were located before the clear transition point, defining as the ductile to brittle transition. The machined area at the brittle region displayed the fracture deformation which showed cracks on the surface edge. The relationship between depth of cut and the ductile to brittle transaction behavior of titanium alloys in ultra-precision machining(UPM) was also revealed in this study, it showed that the ductile to brittle transaction behavior of titanium alloys occurred mainly at relatively small depth of cut. The study firstly defines the ductile to brittle transition behavior of titanium alloys in UPM, contributing the information of ductile machining as an optimal machining condition for precise productions of titanium alloys.

  3. Portal for Families Overcoming Neurodevelopmental Disorders (PFOND): Implementation of a Software Framework for Facilitated Community Website Creation by Nontechnical Volunteers.

    PubMed

    Ye, Xin Cynthia; Ng, Isaiah; Seid-Karbasi, Puya; Imam, Tuhina; Lee, Cheryl E; Chen, Shirley Yu; Herman, Adam; Sharma, Balraj; Johal, Gurinder; Gu, Bobby; Wasserman, Wyeth W

    2013-08-06

    The Portal for Families Overcoming Neurodevelopmental Disorders (PFOND) provides a structured Internet interface for the sharing of information with individuals struggling with the consequences of rare developmental disorders. Large disease-impacted communities can support fundraising organizations that disseminate Web-based information through elegant websites run by professional staff. Such quality resources for families challenged by rare disorders are infrequently produced and, when available, are often dependent upon the continued efforts of a single individual. The project endeavors to create an intuitive Web-based software system that allows a volunteer with limited technical computer skills to produce a useful rare disease website in a short time period. Such a system should provide access to emerging news and research findings, facilitate community participation, present summary information about the disorder, and allow for transient management by volunteers who are likely to change periodically. The prototype portal was implemented using the WordPress software system with both existing and customized supplementary plug-in software modules. Gamification scoring features were implemented in a module, allowing editors to measure progress. The system was installed on a Linux-based computer server, accessible across the Internet through standard Web browsers. A prototype PFOND system was implemented and tested. The prototype system features a structured organization with distinct partitions for background information, recent publications, and community discussions. The software design allows volunteer editors to create a themed website, implement a limited set of topic pages, and connect the software to dynamic RSS feeds providing information about recent news or advances. The prototype was assessed by a fraction of the disease sites developed (8 out of 27), including Aarskog-Scott syndrome, Aniridia, Adams-Oliver syndrome, Cat Eye syndrome, Kabuki syndrome

  4. Portal for Families Overcoming Neurodevelopmental Disorders (PFOND): Implementation of a Software Framework for Facilitated Community Website Creation by Nontechnical Volunteers

    PubMed Central

    Imam, Tuhina; Lee, Cheryl E; Chen, Shirley Yu; Herman, Adam; Sharma, Balraj; Johal, Gurinder; Gu, Bobby

    2013-01-01

    Background The Portal for Families Overcoming Neurodevelopmental Disorders (PFOND) provides a structured Internet interface for the sharing of information with individuals struggling with the consequences of rare developmental disorders. Large disease-impacted communities can support fundraising organizations that disseminate Web-based information through elegant websites run by professional staff. Such quality resources for families challenged by rare disorders are infrequently produced and, when available, are often dependent upon the continued efforts of a single individual. Objective The project endeavors to create an intuitive Web-based software system that allows a volunteer with limited technical computer skills to produce a useful rare disease website in a short time period. Such a system should provide access to emerging news and research findings, facilitate community participation, present summary information about the disorder, and allow for transient management by volunteers who are likely to change periodically. Methods The prototype portal was implemented using the WordPress software system with both existing and customized supplementary plug-in software modules. Gamification scoring features were implemented in a module, allowing editors to measure progress. The system was installed on a Linux-based computer server, accessible across the Internet through standard Web browsers. Results A prototype PFOND system was implemented and tested. The prototype system features a structured organization with distinct partitions for background information, recent publications, and community discussions. The software design allows volunteer editors to create a themed website, implement a limited set of topic pages, and connect the software to dynamic RSS feeds providing information about recent news or advances. The prototype was assessed by a fraction of the disease sites developed (8 out of 27), including Aarskog-Scott syndrome, Aniridia, Adams-Oliver syndrome

  5. Analytical model of brittle destruction based on hypothesis of scale similarity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Arakcheev, A. S., E-mail: asarakcheev@gmail.com; Lotov, K. V.

    2012-08-15

    The size distribution of dust particles in thermonuclear (fusion) devices is closely described by a power law, which may be related to the brittle destruction of materials. The hypothesis of scale similarity leads to the conclusion that the size distribution of particles formed as a result of a brittle destruction is described by a power law with the exponent -{alpha} that can range from -4 to -1. The model of brittle destruction is described in terms of the fractal geometry, and the distribution exponent is expressed via the fractal dimension of packing. Under additional assumptions, it is possible to refinemore » the {alpha} value and, vice versa, to determine the type of destruction using the measured size distribution of particles.« less

  6. Brittle and ductile friction and the physics of tectonic tremor

    USGS Publications Warehouse

    Daub, Eric G.; Shelly, David R.; Guyer, Robert A.; Johnson, P.A.

    2011-01-01

    Observations of nonvolcanic tremor provide a unique window into the mechanisms of deformation and failure in the lower crust. At increasing depths, rock deformation gradually transitions from brittle, where earthquakes occur, to ductile, with tremor occurring in the transitional region. The physics of deformation in the transition region remain poorly constrained, limiting our basic understanding of tremor and its relation to earthquakes. We combine field and laboratory observations with a physical friction model comprised of brittle and ductile components, and use the model to provide constraints on the friction and stress state in the lower crust. A phase diagram is constructed that characterizes under what conditions all faulting behaviors occur, including earthquakes, tremor, silent transient slip, and steady sliding. Our results show that tremor occurs over a range of ductile and brittle frictional strengths, and advances our understanding of the physical conditions at which tremor and earthquakes take place.

  7. Towards a software profession

    NASA Technical Reports Server (NTRS)

    Berard, Edward V.

    1986-01-01

    An increasing number of programmers have attempted to change their image. They have made it plain that they wish not only to be taken seriously, but they also wish to be regarded as professionals. Many programmers now wish to referred to as software engineers. If programmers wish to be considered professionals in every sense of the word, two obstacles must be overcome: the inability to think of software as a product, and the idea that little or no skill is required to create and handle software throughout its life cycle. The steps to be taken toward professionalization are outlined along with recommendations.

  8. Enhanced CARES Software Enables Improved Ceramic Life Prediction

    NASA Technical Reports Server (NTRS)

    Janosik, Lesley A.

    1997-01-01

    The NASA Lewis Research Center has developed award-winning software that enables American industry to establish the reliability and life of brittle material (e.g., ceramic, intermetallic, graphite) structures in a wide variety of 21st century applications. The CARES (Ceramics Analysis and Reliability Evaluation of Structures) series of software is successfully used by numerous engineers in industrial, academic, and government organizations as an essential element of the structural design and material selection processes. The latest version of this software, CARES/Life, provides a general- purpose design tool that predicts the probability of failure of a ceramic component as a function of its time in service. CARES/Life was recently enhanced by adding new modules designed to improve functionality and user-friendliness. In addition, a beta version of the newly-developed CARES/Creep program (for determining the creep life of monolithic ceramic components) has just been released to selected organizations.

  9. Modeling of brittle-viscous flow using discrete particles

    NASA Astrophysics Data System (ADS)

    Thordén Haug, Øystein; Barabasch, Jessica; Virgo, Simon; Souche, Alban; Galland, Olivier; Mair, Karen; Abe, Steffen; Urai, Janos L.

    2017-04-01

    Many geological processes involve both viscous flow and brittle fractures, e.g. boudinage, folding and magmatic intrusions. Numerical modeling of such viscous-brittle materials poses challenges: one has to account for the discrete fracturing, the continuous viscous flow, the coupling between them, and potential pressure dependence of the flow. The Discrete Element Method (DEM) is a numerical technique, widely used for studying fracture of geomaterials. However, the implementation of viscous fluid flow in discrete element models is not trivial. In this study, we model quasi-viscous fluid flow behavior using Esys-Particle software (Abe et al., 2004). We build on the methodology of Abe and Urai (2012) where a combination of elastic repulsion and dashpot interactions between the discrete particles is implemented. Several benchmarks are presented to illustrate the material properties. Here, we present extensive, systematic material tests to characterize the rheology of quasi-viscous DEM particle packing. We present two tests: a simple shear test and a channel flow test, both in 2D and 3D. In the simple shear tests, simulations were performed in a box, where the upper wall is moved with a constant velocity in the x-direction, causing shear deformation of the particle assemblage. Here, the boundary conditions are periodic on the sides, with constant forces on the upper and lower walls. In the channel flow tests, a piston pushes a sample through a channel by Poisseuille flow. For both setups, we present the resulting stress-strain relationships over a range of material parameters, confining stress and strain rate. Results show power-law dependence between stress and strain rate, with a non-linear dependence on confining force. The material is strain softening under some conditions (which). Additionally, volumetric strain can be dilatant or compactant, depending on porosity, confining pressure and strain rate. Constitutive relations are implemented in a way that limits the

  10. Method for preparing surfaces of metal composites having a brittle phase for plating. [Patent application

    DOEpatents

    Coates, C.W.; Wilson, T.J.

    1982-05-19

    The present invention is directed to a method for preparing surfaces of two-phase metal composites having relatively brittle and malleable components for plating with corrosion-resistant material. In practice of the present invention, the surfaces of the composite are etched to remove a major portion or fraction of the brittle component. The etched surface is then peened with particulates for breaking the brittle component from the surfaces and for spreading or smearing the malleable component over the surfaces. The peened surface is then chemically cleaned of residual traces of the brittle component to which the corrosion-resistant material may be plated thereon in an adherent manner.

  11. Patterns of brittle deformation under extension on Venus

    NASA Technical Reports Server (NTRS)

    Neumann, G. A.; Zuber, M. T.

    1994-01-01

    The development of fractures at regular length scales is a widespread feature of Venusian tectonics. Models of lithospheric deformation under extension based on non-Newtonian viscous flow and brittle-plastic flow develop localized failure at preferred wavelengths that depend on lithospheric thickness and stratification. The characteristic wavelengths seen in rift zones and tessera can therefore provide constraints on crustal and thermal structure. Analytic solutions were obtained for growth rates in infinitesimal perturbations imposed on a one-dimensional, layered rheology. Brittle layers were approximated by perfectly-plastic, uniform strength, overlying ductile layers exhibiting thermally-activated power-law creep. This study investigates the formation of faults under finite amounts of extension, employing a finite-element approach. Our model incorporates non-linear viscous rheology and a Coulomb failure envelope. An initial perturbation in crustal thickness gives rise to necking instabilities. A small amount of velocity weakening serves to localize deformation into planar regions of high strain rate. Such planes are analogous to normal faults seen in terrestrial rift zones. These 'faults' evolve to low angle under finite extension. Fault spacing, orientation and location, and the depth to the brittle-ductile transition, depend in a complex way on lateral variations in crustal thickness. In general, we find that multiple wavelengths of deformation can arise from the interaction of crustal and mantle lithosphere.

  12. An improved method for predicting brittleness of rocks via well logs in tight oil reservoirs

    NASA Astrophysics Data System (ADS)

    Wang, Zhenlin; Sun, Ting; Feng, Cheng; Wang, Wei; Han, Chuang

    2018-06-01

    There can be no industrial oil production in tight oil reservoirs until fracturing is undertaken. Under such conditions, the brittleness of the rocks is a very important factor. However, it has so far been difficult to predict. In this paper, the selected study area is the tight oil reservoirs in Lucaogou formation, Permian, Jimusaer sag, Junggar basin. According to the transformation of dynamic and static rock mechanics parameters and the correction of confining pressure, an improved method is proposed for quantitatively predicting the brittleness of rocks via well logs in tight oil reservoirs. First, 19 typical tight oil core samples are selected in the study area. Their static Young’s modulus, static Poisson’s ratio and petrophysical parameters are measured. In addition, the static brittleness indices of four other tight oil cores are measured under different confining pressure conditions. Second, the dynamic Young’s modulus, Poisson’s ratio and brittleness index are calculated using the compressional and shear wave velocity. With combination of the measured and calculated results, the transformation model of dynamic and static brittleness index is built based on the influence of porosity and clay content. The comparison of the predicted brittleness indices and measured results shows that the model has high accuracy. Third, on the basis of the experimental data under different confining pressure conditions, the amplifying factor of brittleness index is proposed to correct for the influence of confining pressure on the brittleness index. Finally, the above improved models are applied to formation evaluation via well logs. Compared with the results before correction, the results of the improved models agree better with the experimental data, which indicates that the improved models have better application effects. The brittleness index prediction method of tight oil reservoirs is improved in this research. It is of great importance in the optimization of

  13. Insensitivity of compaction properties of brittle granules to size enlargement by roller compaction.

    PubMed

    Wu, Sy-Juen; Sun, Changquan 'Calvin'

    2007-05-01

    Pharmaceutical granules prepared by roller compaction often exhibit significant loss of tabletability, that is, reduction in tensile strength, when compared to virgin powder. This may be attributed to granule size enlargement for highly plastic materials, for example, microcrystalline cellulose. The sensitivity of powder compaction properties on granule size variations impacts the robustness of the dry granulation process. We hypothesize that such sensitivity of compaction properties on granule size is minimum for brittle materials because extensive fracture of brittle granules during compaction minimizes differences in initial granule size. We tested the hypothesis using three common brittle excipients. Results show that the fine (44-106 microm), medium (106-250 microm), and coarse (250-500 microm) granules exhibit essentially identical tabletability below a certain critical compaction pressure, 100, 140, and 100 MPa for spray-dried lactose monohydrate, anhydrous dibasic calcium phosphate, and mannitol, respectively. Above respective critical pressure, tabletability lines diverge with smaller granules exhibiting slightly higher tablet tensile strength at identical compaction conditions. Overall, tabletability of brittle granules is insensitive to granule size enlargement. The results provide a scientific basis to the common practice of incorporating brittle filler to a typical tablet formulation processed by roller compaction granulation. (c) 2007 Wiley-Liss, Inc. and the American Pharmacists Association.

  14. Elastic Rock Heterogeneity Controls Brittle Rock Failure during Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Langenbruch, C.; Shapiro, S. A.

    2014-12-01

    For interpretation and inversion of microseismic data it is important to understand, which properties of the reservoir rock control the occurrence probability of brittle rock failure and associated seismicity during hydraulic stimulation. This is especially important, when inverting for key properties like permeability and fracture conductivity. Although it became accepted that seismic events are triggered by fluid flow and the resulting perturbation of the stress field in the reservoir rock, the magnitude of stress perturbations, capable of triggering failure in rocks, can be highly variable. The controlling physical mechanism of this variability is still under discussion. We compare the occurrence of microseismic events at the Cotton Valley gas field to elastic rock heterogeneity, obtained from measurements along the treatment wells. The heterogeneity is characterized by scale invariant fluctuations of elastic properties. We observe that the elastic heterogeneity of the rock formation controls the occurrence of brittle failure. In particular, we find that the density of events is increasing with the Brittleness Index (BI) of the rock, which is defined as a combination of Young's modulus and Poisson's ratio. We evaluate the physical meaning of the BI. By applying geomechanical investigations we characterize the influence of fluctuating elastic properties in rocks on the probability of brittle rock failure. Our analysis is based on the computation of stress fluctuations caused by elastic heterogeneity of rocks. We find that elastic rock heterogeneity causes stress fluctuations of significant magnitude. Moreover, the stress changes necessary to open and reactivate fractures in rocks are strongly related to fluctuations of elastic moduli. Our analysis gives a physical explanation to the observed relation between elastic heterogeneity of the rock formation and the occurrence of brittle failure during hydraulic reservoir stimulations. A crucial factor for understanding

  15. CARES/Life Software for Designing More Reliable Ceramic Parts

    NASA Technical Reports Server (NTRS)

    Nemeth, Noel N.; Powers, Lynn M.; Baker, Eric H.

    1997-01-01

    Products made from advanced ceramics show great promise for revolutionizing aerospace and terrestrial propulsion, and power generation. However, ceramic components are difficult to design because brittle materials in general have widely varying strength values. The CAPES/Life software eases this task by providing a tool to optimize the design and manufacture of brittle material components using probabilistic reliability analysis techniques. Probabilistic component design involves predicting the probability of failure for a thermomechanically loaded component from specimen rupture data. Typically, these experiments are performed using many simple geometry flexural or tensile test specimens. A static, dynamic, or cyclic load is applied to each specimen until fracture. Statistical strength and SCG (fatigue) parameters are then determined from these data. Using these parameters and the results obtained from a finite element analysis, the time-dependent reliability for a complex component geometry and loading is then predicted. Appropriate design changes are made until an acceptable probability of failure has been reached.

  16. Specification Improvement Through Analysis of Proof Structure (SITAPS): High Assurance Software Development

    DTIC Science & Technology

    2016-02-01

    proof in mathematics. For example, consider the proof of the Pythagorean Theorem illustrated at: http://www.cut-the-knot.org/ pythagoras / where 112...methods and tools have made significant progress in their ability to model software designs and prove correctness theorems about the systems modeled...assumption criticality” or “ theorem root set size” SITAPS detects potentially brittle verification cases. SITAPS provides tools and techniques that

  17. Sample Size Induced Brittle-to-Ductile Transition of Single-Crystal Aluminum Nitride

    DTIC Science & Technology

    2015-08-01

    exhibit many distinctive physical and mechanical properties, compared to metallic and polymeric materials, but the propensity toward brittle fracture ...micromechanism for the plastic deformation of ductile metals while the mechanical performance of high-strength ceramics is often dominated by brittle fracture at...SUPPLEMENTARY NOTES A reprint from Acta Materialia 88 (2015) 252–259 14. ABSTRACT Ceramics are known to be mechanically hard, chemically inert and

  18. Displacement-length scaling of brittle faults in ductile shear.

    PubMed

    Grasemann, Bernhard; Exner, Ulrike; Tschegg, Cornelius

    2011-11-01

    Within a low-grade ductile shear zone, we investigated exceptionally well exposed brittle faults, which accumulated antithetic slip and rotated into the shearing direction. The foliation planes of the mylonitic host rock intersect the faults approximately at their centre and exhibit ductile reverse drag. Three types of brittle faults can be distinguished: (i) Faults developing on pre-existing K-feldspar/mica veins that are oblique to the shear direction. These faults have triclinic flanking structures. (ii) Wing cracks opening as mode I fractures at the tips of the triclinic flanking structures, perpendicular to the shear direction. These cracks are reactivated as faults with antithetic shear, extend from the parent K-feldspar/mica veins and form a complex linked flanking structure system. (iii) Joints forming perpendicular to the shearing direction are deformed to form monoclinic flanking structures. Triclinic and monoclinic flanking structures record elliptical displacement-distance profiles with steep displacement gradients at the fault tips by ductile flow in the host rocks, resulting in reverse drag of the foliation planes. These structures record one of the greatest maximum displacement/length ratios reported from natural fault structures. These exceptionally high ratios can be explained by localized antithetic displacement along brittle slip surfaces, which did not propagate during their rotation during surrounding ductile flow.

  19. Displacement–length scaling of brittle faults in ductile shear

    PubMed Central

    Grasemann, Bernhard; Exner, Ulrike; Tschegg, Cornelius

    2011-01-01

    Within a low-grade ductile shear zone, we investigated exceptionally well exposed brittle faults, which accumulated antithetic slip and rotated into the shearing direction. The foliation planes of the mylonitic host rock intersect the faults approximately at their centre and exhibit ductile reverse drag. Three types of brittle faults can be distinguished: (i) Faults developing on pre-existing K-feldspar/mica veins that are oblique to the shear direction. These faults have triclinic flanking structures. (ii) Wing cracks opening as mode I fractures at the tips of the triclinic flanking structures, perpendicular to the shear direction. These cracks are reactivated as faults with antithetic shear, extend from the parent K-feldspar/mica veins and form a complex linked flanking structure system. (iii) Joints forming perpendicular to the shearing direction are deformed to form monoclinic flanking structures. Triclinic and monoclinic flanking structures record elliptical displacement–distance profiles with steep displacement gradients at the fault tips by ductile flow in the host rocks, resulting in reverse drag of the foliation planes. These structures record one of the greatest maximum displacement/length ratios reported from natural fault structures. These exceptionally high ratios can be explained by localized antithetic displacement along brittle slip surfaces, which did not propagate during their rotation during surrounding ductile flow. PMID:26806996

  20. Brittle to Semibrittle Transition in Quartz Sandstone: Energetics

    NASA Astrophysics Data System (ADS)

    Kanaya, Taka; Hirth, Greg

    2018-01-01

    Triaxial compression experiments were conducted on a quartz sandstone at effective pressures up to 175 MPa and temperatures up to 900°C. Our experiments show a transition from brittle faulting to semibrittle faulting with an increase in both pressure and temperature. The yield behavior of samples deformed in the semibrittle regime follows a compactant elliptical cap at low strain, but evolves to a dilatant Mohr-Coulomb relationship with continued compaction. Optical microscopy indicates that semibrittle deformation involves cataclastic flow through shear-enhanced compaction and grain crushing; however, transmission electron microscopy shows evidence for dislocation glide in limited portions of samples. To constrain the relative contribution of brittle and crystal plastic mechanisms, we estimate the partitioning of the inelastic work into the dissipation energy for microcracking, intergranular frictional slip, and dislocation glide. We conclude that semibrittle deformation is accommodated primarily by cataclastic mechanisms, with only a limited contribution from crystal plasticity. Mechanical data, acoustic emission records, and analysis of surface energy all indicate the activation of subcritical cracking at elevated temperature. Hence, we infer that the enhancement of subcritical cracking is responsible for the transition to semibrittle flow through promoting distributed grain-scale fractures and millimeter-scale shear bands. Subcritical cracking promotes the nucleation of microfractures at lower stresses, and the resulting decrease in flow stress retards the propagation of transgranular microfractures. Our study illuminates the important role of temperature on the micromechanics of the transition from brittle faulting to cataclastic flow in the Earth.

  1. A natural example of fluid-mediated brittle-ductile cyclicity in quartz veins from Olkiluoto Island, SW Finland

    NASA Astrophysics Data System (ADS)

    Marchesini, Barbara; Garofalo, Paolo S.; Viola, Giulio; Mattila, Jussi; Menegon, Luca

    2017-04-01

    Brittle faults are well known as preferential conduits for localised fluid flow in crystalline rocks. Their study can thus reveal fundamental details of the physical-chemical properties of the flowing fluid phase and of the mutual feedbacks between mechanical properties of faults and fluids. Crustal deformation at the brittle-ductile transition may occur by a combination of competing brittle fracturing and viscous flow processes, with short-lived variations in fluid pressure as a viable mechanism to produce this cyclicity switch. Therefore, a detailed study of the fluid phases potentially present in faults can help to better constrain the dynamic evolution of crustal strength within the seismogenic zone, as a function of varying fluid phase characteristics. With the aim to 1) better understand the complexity of brittle-ductile cyclicity under upper to mid-crustal conditions and 2) define the physical and chemical features of the involved fluid phase, we present the preliminary results of a recently launched (micro)structural and geochemical project. We study deformed quartz veins associated with brittle-ductile deformation zones on Olkiluoto Island, chosen as the site for the Finnish deep repository for spent nuclear fuel excavated in the Paleoproterozoic crust of southwestern Finland. The presented results stem from the study of brittle fault zone BFZ300, which is a mixed brittle and ductile deformation zone characterized by complex kinematics and associated with multiple generations of quartz veins, and which serves as a pertinent example of the mechanisms of fluid flow-deformation feedbacks during brittle-ductile cyclicity in nature. A kinematic and dynamic mesostructural study is being integrated with the detailed analysis of petrographic thin sections from the fault core and its immediate surroundings with the aim to reconstruct the mechanical deformation history along the entire deformation zone. Based on the observed microstructures, it was possible to

  2. The Potential of Brittle Star Extracted Polysaccharide in Promoting Apoptosis via Intrinsic Signaling Pathway.

    PubMed

    Baharara, Javad; Amini, Elaheh

    2015-01-01

    Anti-cancer potential of marine natural products such as polysaccharides represented therapeutic potential in oncological researches. In this study, total polysaccharide from brittle star [Ophiocoma erinaceus (O. erinaceus)] was extracted and chemopreventive efficacy of Persian Gulf brittle star polysaccharide was investigated in HeLa human cervical cancer cells. To extract polysaccharide, dried brittle stars were ground and extracted mechanically. Then, detection of polysaccharide was performed by phenol sulfuric acid, Ultra Violet (UV)-sulfuric acid method and FTIR. The anti proliferative activity of isolated polysaccharide was examined by MTT assay and evaluation of cell death was done through morphological cell changes; Propodium Iodide staining, fluorescence microscopy and caspase-3, -9 enzymatic measurements. To assess its underlying mechanism, expression of Bax, Bcl-2 was evaluated. The polysaccharide detection methods demonstrated isolation of crude polysaccharide from Persian Gulf brittle star. The results revealed that O. erinaceus polysaccharide suppressed the proliferation of HeLa cells in a dose and time dependent manner. Morphological observation of DAPI and Acridine Orange/Propodium Iodide staining was documented by typical characteristics of apoptotic cell death. Flow cytometry analyses exhibited the accumulation of treated cells in sub-G1 region. Additionally, polysaccharide extracted induced intrinsic apoptosis via up-regulation of caspase-3, caspase-9 and Bax along with down-regulation of Bcl-2 in HeLa cells. Taken together, the apoptosis inducing effect of brittle star polysaccharide via intrinsic pathway confirmed the anti tumor potential of marine polysaccharide. Therefore, these findings proposed new insight into anti cancer properties of brittle star polysaccharide as a promising agent in cervical cancer treatment.

  3. Determination of the ductile-brittle transition temperature from the microplastic-strain rate

    NASA Astrophysics Data System (ADS)

    Andreev, A. K.; Solntsev, Yu. P.

    2008-04-01

    The possibility of the determination of the tendency of cast and deformed steels to brittle fracture using the temperature dependence of the small-plastic-strain rate is studied. The temperature corresponding to the maximum in this curve is found to indicate an abrupt decrease in the steel plasticity, which makes it possible to interpret it as the ductile-brittle transition temperature depending only on the structure of a material.

  4. EPA's Benchmark Dose Modeling Software

    EPA Science Inventory

    The EPA developed the Benchmark Dose Software (BMDS) as a tool to help Agency risk assessors facilitate applying benchmark dose (BMD) method’s to EPA’s human health risk assessment (HHRA) documents. The application of BMD methods overcomes many well know limitations ...

  5. Communication Management Guidelines for Software Organizations in Pakistan with clients from Afghanistan

    NASA Astrophysics Data System (ADS)

    Arif Shah, Muhammad; Hashim, Rathiah; Shah, Adil Ali; Farooq Khattak, Umar

    2016-11-01

    Developing software through Global Software Development (GSD) became very common now days in the software industry. Pakistan is one of the countries where projects are taken and designed from different countries including Afghanistan. The purpose of this paper is to identify and provide an analysis on several communication barriers that can have a negative impact on the project and to provide management guidelines for medium size software organizations working in Pakistan with clients from Afghanistan and to overcome these communication barriers and challenges organizations face when coordinating with client. Initially we performed a literature review to identify different communication barriers and to check if there are any standardized communications management guidelines for medium size software houses provided in the past. The second stage of the research paper involves guidelines with vendor's perspective that include interviews and focus group discussions with different stakeholders and employees of software houses with clients from Afghanistan. Based on those interviews and discussions we established communication management guidelines in order to overcome the communication problems and barriers working with clients from Afghanistan. As a result of the literature review, we have identified that barriers such as cultural barriers and language barrier were one of the main reasons behind the project failure and suggested that software organizations working in Pakistan should follow certain defined communication guidelines in order to overcome communication barriers that affect the project directly.

  6. The NASA Software Research Infusion Initiative: Successful Technology Transfer for Software Assurance

    NASA Technical Reports Server (NTRS)

    Hinchey, Michael G.; Pressburger, Thomas; Markosian, Lawrence; Feather, Martin S.

    2006-01-01

    New processes, methods and tools are constantly appearing in the field of software engineering. Many of these augur great potential in improving software development processes, resulting in higher quality software with greater levels of assurance. However, there are a number of obstacles that impede their infusion into software development practices. These are the recurring obstacles common to many forms of research. Practitioners cannot readily identify the emerging techniques that may most benefit them, and cannot afford to risk time and effort in evaluating and experimenting with them while there is still uncertainty about whether they will have payoff in this particular context. Similarly, researchers cannot readily identify those practitioners whose problems would be amenable to their techniques and lack the feedback from practical applications necessary to help them to evolve their techniques to make them more likely to be successful. This paper describes an ongoing effort conducted by a software engineering research infusion team, and the NASA Research Infusion Initiative, established by NASA s Software Engineering Initiative, to overcome these obstacles.

  7. Universal Viscous-Brittle Transition in Magmatic Liquids

    NASA Astrophysics Data System (ADS)

    Witcher, T.; Wadsworth, F. B.; Hess, K. U.; Vossen, C.; Unwin, H.; Dingwell, D. B.

    2017-12-01

    Physical processes occurring in a volcanic conduit are thought to dictate the eruptivebehavior of volcanoes. One of these processes is the rheological response of the liquidmagma to the enormous stresses applied to it during ascent. In this study we investigatedthe behavior of both synthetic and natural silicate glass at high temperature. We chosetemperatures at which the glass viscosity was high in the range of 109 - 1012 Pa s. Afterthermal equilibration, we deformed the samples by uniaxial compression. We measured theforce and displacement applied to 20 x 40 mm glass cylinders at controlled strain rates. Toparameterize the deformation behavior we defined a dimensionless quantity, the Deborahnumber (De), which is a ratio between viscoelastic relaxation time of the liquid (λr) and thedeformation time (λ) both in units of seconds. Each deformed sample had a De assignedto it and was plotted on a 'Deformation Map.' After performing over 60 experiments,three deformational regimes were defined: viscous, transitional, and brittle. We found thatall samples with De < 0.01 behaved purely viscously with no stress drops. Between De =0.01 and De = 0.04 the behavior was unrelaxed, in which small stress drops were observedbetween otherwise viscous flow, indicating the onset of elastic behavior. Furthermore,samples with De > 0.04 were categorized as brittle and behaved purely elastically withlittle to no fracturing before one large stress drop. The implications of this study showthat when a silicate melt is not given enough time to dissipate the stress applied to itthrough viscous flow, it will behave like an elastic solid and support fracture propagation.It is through this capability of brittle failure that magma can rapidly ascend through theshallow crust-the fractures would provide pathways for fluid along the conduit margin.These fluids would lubricate the magma body as it ascends.

  8. Modeling multiscale evolution of numerous voids in shocked brittle material.

    PubMed

    Yu, Yin; Wang, Wenqiang; He, Hongliang; Lu, Tiecheng

    2014-04-01

    The influence of the evolution of numerous voids on macroscopic properties of materials is a multiscale problem that challenges computational research. A shock-wave compression model for brittle material, which can obtain both microscopic evolution and macroscopic shock properties, was developed using discrete element methods (lattice model). Using a model interaction-parameter-mapping procedure, qualitative features, as well as trends in the calculated shock-wave profiles, are shown to agree with experimental results. The shock wave splits into an elastic wave and a deformation wave in porous brittle materials, indicating significant shock plasticity. Void collapses in the deformation wave were the natural reason for volume shrinkage and deformation. However, media slippage and rotation deformations indicated by complex vortex patterns composed of relative velocity vectors were also confirmed as an important source of shock plasticity. With increasing pressure, the contribution from slippage deformation to the final plastic strain increased. Porosity was found to determine the amplitude of the elastic wave; porosity and shock stress together determine propagation speed of the deformation wave, as well as stress and strain on the final equilibrium state. Thus, shock behaviors of porous brittle material can be systematically designed for specific applications.

  9. Seismic Rheological Model and Reflection Coefficients of the Brittle-Ductile Transition

    NASA Astrophysics Data System (ADS)

    Carcione, José M.; Poletto, Flavio

    2013-12-01

    It is well established that the upper—cooler—part of the crust is brittle, while deeper zones present ductile behaviour. In some cases, this brittle-ductile transition is a single seismic reflector with an associated reflection coefficient. We first develop a stress-strain relation including the effects of crust anisotropy, seismic attenuation and ductility in which deformation takes place by shear plastic flow. Viscoelastic anisotropy is based on the eigenstrain model and the Zener and Burgers mechanical models are used to model the effects of seismic attenuation, velocity dispersion, and steady-state creep flow, respectively. The stiffness components of the brittle and ductile media depend on stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P- and S-wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the reflection and transmission coefficients of a single brittle-ductile interface and of a ductile thin layer. The PP scattering coefficient has a Brewster angle (a sign change) in both cases, and there is substantial PS conversion at intermediate angles. The PP coefficient is sensitive to the layer thickness, unlike the SS coefficient. Thick layers have a well-defined Brewster angle and show higher reflection amplitudes. Finally, we compute synthetic seismograms in a homogeneous medium as a function of temperature.

  10. Ductile-to-Brittle transition in <111> hadfield steel single crystals

    NASA Astrophysics Data System (ADS)

    Astafurova, E. G.; Chumlyakov, Yu. I.

    2010-10-01

    The deformation mechanism and the character of fracture of <111> austenitic Hadfield steel single crystals are studied during tension in the temperature range 77-673 K by scanning and transmission electron microscopy. It is found that a change in the fracture mechanism from ductile to brittle fracture according to the fractography criterion takes place at a higher temperature than that determined from a change in the elongation to failure of the single crystals. The ductile-to-brittle transition in the Hadfield steel single crystals is shown to be related to a high level of deforming stresses induced by solid-solution hardening and to mechanical twinning.

  11. Influence of Composition and Deformation Conditions on the Strength and Brittleness of Shale Rock

    NASA Astrophysics Data System (ADS)

    Rybacki, E.; Reinicke, A.; Meier, T.; Makasi, M.; Dresen, G. H.

    2015-12-01

    Stimulation of shale gas reservoirs by hydraulic fracturing operations aims to increase the production rate by increasing the rock surface connected to the borehole. Prospective shales are often believed to display high strength and brittleness to decrease the breakdown pressure required to (re-) initiate a fracture as well as slow healing of natural and hydraulically induced fractures to increase the lifetime of the fracture network. Laboratory deformation tests were performed on several, mainly European black shales with different mineralogical composition, porosity and maturity at ambient and elevated pressures and temperatures. Mechanical properties such as compressive strength and elastic moduli strongly depend on shale composition, porosity, water content, structural anisotropy, and on pressure (P) and temperature (T) conditions, but less on strain rate. We observed a transition from brittle to semibrittle deformation at high P-T conditions, in particular for high porosity shales. At given P-T conditions, the variation of compressive strength and Young's modulus with composition can be roughly estimated from the volumetric proportion of all components including organic matter and pores. We determined also brittleness index values based on pre-failure deformation behavior, Young's modulus and bulk composition. At low P-T conditions, where samples showed pronounced post-failure weakening, brittleness may be empirically estimated from bulk composition or Young's modulus. Similar to strength, at given P-T conditions, brittleness depends on the fraction of all components and not the amount of a specific component, e.g. clays, alone. Beside strength and brittleness, knowledge of the long term creep properties of shales is required to estimate in-situ stress anisotropy and the healing of (propped) hydraulic fractures.

  12. Effect of High-Temperature Thermomechanical Treatment on the Brittle Fracture of Low-Carbon Steel

    NASA Astrophysics Data System (ADS)

    Smirnov, M. A.; Pyshmintsev, I. Yu.; Varnak, O. V.; Mal'tseva, A. N.

    2018-02-01

    The effect of high-temperature thermomechanical treatment (HTMT) on the brittleness connected with deformation-induced aging and on the reversible temper brittleness of a low-carbon tube steel with a ferrite-bainite structure has been studied. When conducting an HTMT of a low-alloy steel, changes should be taken into account in the amount of ferrite in its structure and relationships between the volume fractions of the lath and the acicular bainite. It has been established that steel subjected to HTMT undergoes transcrystalline embrittlement upon deformation aging. At the same time, HTMT, which suppresses intercrystalline fracture, leads to a weakening of the development of reversible temper brittleness.

  13. Strength/Brittleness Classification of Igneous Intact Rocks Based on Basic Physical and Dynamic Properties

    NASA Astrophysics Data System (ADS)

    Aligholi, Saeed; Lashkaripour, Gholam Reza; Ghafoori, Mohammad

    2017-01-01

    This paper sheds further light on the fundamental relationships between simple methods, rock strength, and brittleness of igneous rocks. In particular, the relationship between mechanical (point load strength index I s(50) and brittleness value S 20), basic physical (dry density and porosity), and dynamic properties (P-wave velocity and Schmidt rebound values) for a wide range of Iranian igneous rocks is investigated. First, 30 statistical models (including simple and multiple linear regression analyses) were built to identify the relationships between mechanical properties and simple methods. The results imply that rocks with different Schmidt hardness (SH) rebound values have different physicomechanical properties or relations. Second, using these results, it was proved that dry density, P-wave velocity, and SH rebound value provide a fine complement to mechanical properties classification of rock materials. Further, a detailed investigation was conducted on the relationships between mechanical and simple tests, which are established with limited ranges of P-wave velocity and dry density. The results show that strength values decrease with the SH rebound value. In addition, there is a systematic trend between dry density, P-wave velocity, rebound hardness, and brittleness value of the studied rocks, and rocks with medium hardness have a higher brittleness value. Finally, a strength classification chart and a brittleness classification table are presented, providing reliable and low-cost methods for the classification of igneous rocks.

  14. Shock-induced Plasticity and Brittle Cracks in Aluminum Nitride

    NASA Astrophysics Data System (ADS)

    Branicio, Paulo; Kalia, Rajiv

    2005-03-01

    Two hundred and nine million atom molecular-dynamics simulation of hypervelocity projectile impact in aluminum nitride reveals strong interplay between shock-induced structural phase transformation, plastic deformation and brittle cracks. The shock wave splits into an elastic precursor and a wurtzite-to-rocksalt structural transformation wave. When the elastic wave reflected from the boundary of the sample interacts with the transformation wave front, nanocavities are generated along the penetration path of the projectile and dislocations in adjacent regions. The nanocavities coalesce to form mode I brittle cracks while dislocations generate kink bands that give rise to mode II cracks. These simulations provide a microscopic view of defects associated with simultaneous tensile and shear cracking at the structural phase transformation boundary due to shock impact in high-strength ceramics.

  15. Software management tools: Lessons learned from use

    NASA Technical Reports Server (NTRS)

    Reifer, D. J.; Valett, J.; Knight, J.; Wenneson, G.

    1985-01-01

    Experience in inserting software project planning tools into more than 100 projects producing mission critical software are discussed. The problems the software project manager faces are listed along with methods and tools available to handle them. Experience is reported with the Project Manager's Workstation (PMW) and the SoftCost-R cost estimating package. Finally, the results of a survey, which looked at what could be done in the future to overcome the problems experienced and build a set of truly useful tools, are presented.

  16. Brittle crack arrestability of thick steel plate welds in large structure

    NASA Astrophysics Data System (ADS)

    An, Gyu Baek; Park, Joon Sik

    2011-10-01

    Recently, there has been such a critical issue in shipbuilding industry that much larger and stronger ships are required to develop oil and gas in the Arctic region. Attention has been paid to obtaining high strength, good toughness at low temperature, and good weldability. An experimental study was performed to evaluate the brittle crack arrest toughness value (Kca) and brittle crack arrest method of welded joints using EH40 grade steel with a thickness of 80 mm. The test specimens were made by both flux cored arc welding (FCAW) and combined welding (EGW+FCAW) processes. Temperature gradient ESSO test was performed to measure the Kca of the base metal. Also, a constant temperature (-10 °C) ESSO test was performed to establish a brittle crack arrest method using high toughness welding consumable with real structural specimens. The research aims in this study were to investigate the effect of joint design and welding consumable for the crack arrestability of thick steel plates using EH40 grade shipbuilding steel of straight block joint weld line with two kinds of welding processes.

  17. Brittle to ductile transition in densified silica glass.

    PubMed

    Yuan, Fenglin; Huang, Liping

    2014-05-22

    Current understanding of the brittleness of glass is limited by our poor understanding and control over the microscopic structure. In this study, we used a pressure quenching route to tune the structure of silica glass in a controllable manner, and observed a systematic increase in ductility in samples quenched under increasingly higher pressure. The brittle to ductile transition in densified silica glass can be attributed to the critical role of 5-fold Si coordination defects (bonded to 5 O neighbors) in facilitating shear deformation and in dissipating energy by converting back to the 4-fold coordination state during deformation. As an archetypal glass former and one of the most abundant minerals in the Earth's crest, a fundamental understanding of the microscopic structure underpinning the ductility of silica glass will not only pave the way toward rational design of strong glasses, but also advance our knowledge of the geological processes in the Earth's interior.

  18. Brittle to Ductile Transition in Densified Silica Glass

    PubMed Central

    Yuan, Fenglin; Huang, Liping

    2014-01-01

    Current understanding of the brittleness of glass is limited by our poor understanding and control over the microscopic structure. In this study, we used a pressure quenching route to tune the structure of silica glass in a controllable manner, and observed a systematic increase in ductility in samples quenched under increasingly higher pressure. The brittle to ductile transition in densified silica glass can be attributed to the critical role of 5-fold Si coordination defects (bonded to 5 O neighbors) in facilitating shear deformation and in dissipating energy by converting back to the 4-fold coordination state during deformation. As an archetypal glass former and one of the most abundant minerals in the Earth's crest, a fundamental understanding of the microscopic structure underpinning the ductility of silica glass will not only pave the way toward rational design of strong glasses, but also advance our knowledge of the geological processes in the Earth's interior. PMID:24849328

  19. The brittle-ductile transition in porous sedimentary rocks: geological implications for accretionary wedge aseismicity

    NASA Astrophysics Data System (ADS)

    Zhang, Jiaxiang; Davis, Dan M.; Wong, Teng-Fong

    1993-07-01

    Thrusting earthquakes in subduction zones generally occur along only part of the plate boundary, with motion along the shallowest part of the plate boundary occurring ascismically. The maximum size of subduction boundary thrust earthquakes depends strongly upon the down-dip width of the seismogenic zone. The single most uncertain factor in determining that width is the location of the up-dip limit of the zone (the seismic front), which depends upon the mechanical state of the sedimentary rocks in the plate boundary zone. In order to come to a better understanding of the seismic potential of sediments in a subduction zone, we carried out a series of triaxial experiments on Berea and Kayenta sandstones. Based on our experimental data, a brittle-ductile transition map was constructed showing that both porosity and effective pressure are important factors controlling the transition from brittle to macroscopically ductile behavior in porous rocks. In the brittle field, a sample fails by shear localization on one slip plane accompanied by strain softening and dilatancy, whereas in the ductile field, a sample deforms homogeneously with a constant yield stress or slight hardening. By comparing such a map with the estimated porosity profile of an accretionary wedge, the likely nature and rough location of the boundary between brittle and ductile behavior can be inferred. If the sediments along a plate boundary are too young and undercompacted to be capable of brittle shear localization, then their deformation is likely to be aseismic. In this way, it may be possible for even a very broad fore-arcs to produce no great earthquakes. However, great earthquakes are to be expected at margins that have large zones of plate contact along which many sediments are compacted and well lithified. Such rocks are expected to be capable of shear localization and brittle failure with the potential for stick-slip behavior.

  20. Fracture in compression of brittle solids

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The fracture of brittle solids in monotonic compression is reviewed from both the mechanistic and phenomenological points of view. The fundamental theoretical developments based on the extension of pre-existing cracks in general multiaxial stress fields are recognized as explaining extrinsic behavior where a single crack is responsible for the final failure. In contrast, shear faulting in compression is recognized to be the result of an evolutionary localization process involving en echelon action of cracks and is termed intrinsic.

  1. Meso-scopic Densification in Brittle Granular Materials

    NASA Astrophysics Data System (ADS)

    Neal, William; Appleby-Thomas, Gareth; Collins, Gareth

    2013-06-01

    Particulate materials are ideally suited to shock absorbing applications due to the large amounts of energy required to deform their inherently complex meso-structure. Significant effort is being made to improve macro-scale material models to represent these atypical materials. On the long road towards achieving this capability, an important milestone would be to understand how particle densification mechanisms are affected by loading rate. In brittle particulate materials, the majority of densification is caused by particle fracture. Macro-scale quasi-static and dynamic compaction curves have been measured that show good qualitative agreement. There are, however, some differences that appear to be dependent on the loading rate that require further investigation. This study aims to investigate the difference in grain-fracture behavior between the quasi-static and shock loading response of brittle glass microsphere beds using a combination of quasi-static and dynamic loading techniques. Results from pressure-density measurements, sample recovery, and meso-scale hydrocode models (iSALE, an in-house simulation package) are discussed to explain the differences in particle densification mechanisms between the two loading rate regimes. Gratefully funded by AWE.plc.

  2. Triangular Plots and Spreadsheet Software.

    ERIC Educational Resources Information Center

    Holm, Paul Eric

    1988-01-01

    Describes how the limitations of the built-in graphics capabilities of spreadsheet software can be overcome by making full use of the flexibility of the grahics options. Uses triangular plots with labeled field boundaries produced using Lotus 1-2-3 to demonstrate these techniques and their use in teaching geology. (CW)

  3. Calving Geometry of Thwaites Glacier Linked to Semi-brittle Ice Dynamics

    NASA Astrophysics Data System (ADS)

    Logan, L. C.; Lavier, L.; Choi, E.; Tan, E.; Catania, G. A.; Holt, J.

    2016-12-01

    In the coming decades the linkage between ice dynamics, basal melt, and calving will play a central role in the flow of Thwaites Glacier, which has undergone vast and recent retreat. We explore this connection using a 3D, transient, thermomechanical ice flow model under different basal melt scenarios. Our use of a semi-brittle ice rheology enables the time-dependent development and tracking of surface and basal crevasses that determine the calving rate at this location. With the use of adaptive re-meshing, we are able to simulate the glacier's retreat response to different boundary forcings. We show that the resulting characteristic pinch-and-swell model geometries in the floating tongue compare well with airborne radar data acquired across the grounding line and floating tongue of Thwaites Glacier. These geometric features may be reproduced using this semi-brittle rheology, and further, are linked directly to the calving rate of Thwaites Glacier (and others). The use of semi-brittle rheology on decadal time scales may help provide constraints on the near-term future behavior of glaciers vulnerable to ocean-induced retreat, as this rheology targets the complex interaction of ice failure, basal melt, and flow.

  4. Brittleness estimation from seismic measurements in unconventional reservoirs: Application to the Barnett shale

    NASA Astrophysics Data System (ADS)

    Perez Altimar, Roderick

    Brittleness is a key characteristic for effective reservoir stimulation and is mainly controlled by mineralogy in unconventional reservoirs. Unfortunately, there is no universally accepted means of predicting brittleness from measures made in wells or from surface seismic data. Brittleness indices (BI) are based on mineralogy, while brittleness average estimations are based on Young's modulus and Poisson's ratio. I evaluate two of the more popular brittleness estimation techniques and apply them to a Barnett Shale seismic survey in order to estimate its geomechanical properties. Using specialized logging tools such as elemental capture tool, density, and P- and S wave sonic logs calibrated to previous core descriptions and laboratory measurements, I create a survey-specific BI template in Young's modulus versus Poisson's ratio or alternatively lambdarho versus murho space. I use this template to predict BI from elastic parameters computed from surface seismic data, providing a continuous estimate of BI estimate in the Barnett Shale survey. Extracting lambdarho-murho values from microseismic event locations, I compute brittleness index from the template and find that most microsemic events occur in the more brittle part of the reservoir. My template is validated through a suite of microseismic experiments that shows most events occurring in brittle zones, fewer events in the ductile shale, and fewer events still in the limestone fracture barriers. Estimated ultimate recovery (EUR) is an estimate of the expected total production of oil and/or gas for the economic life of a well and is widely used in the evaluation of resource play reserves. In the literature it is possible to find several approaches for forecasting purposes and economic analyses. However, the extension to newer infill wells is somewhat challenging because production forecasts in unconventional reservoirs are a function of both completion effectiveness and reservoir quality. For shale gas reservoirs

  5. Brittle behavior of ceramic matrix composites made of 2 different phases

    NASA Astrophysics Data System (ADS)

    Sadowski, Tomasz; Craciun, Eduard; Marsavina, Liviu

    2018-02-01

    Brittle behavior of Ceramic matrix Composites (CMCs) results from overall response to applied loads due to complex of their internal microstructure. The CMCs materials are composed of mixtures of phases, some amount of porosity and technological defects. The phases can exhibit purely elastic behavior or elastic-plastic one under high level of loading. The crucial point in description of their behavior is correlation of microcracking processes with the type of loading, i.e. tensile or compressive. This distinction in the material behavior is typical for so called brittle materials. In this paper we compared both microcracking processes for the above 2 characteristic loading paths.

  6. Permeability and seismic velocity anisotropy across a ductile-brittle fault zone in crystalline rock

    NASA Astrophysics Data System (ADS)

    Wenning, Quinn C.; Madonna, Claudio; de Haller, Antoine; Burg, Jean-Pierre

    2018-05-01

    This study characterizes the elastic and fluid flow properties systematically across a ductile-brittle fault zone in crystalline rock at the Grimsel Test Site underground research laboratory. Anisotropic seismic velocities and permeability measured every 0.1 m in the 0.7 m across the transition zone from the host Grimsel granodiorite to the mylonitic core show that foliation-parallel P- and S-wave velocities systematically increase from the host rock towards the mylonitic core, while permeability is reduced nearest to the mylonitic core. The results suggest that although brittle deformation has persisted in the recent evolution, antecedent ductile fabric continues to control the matrix elastic and fluid flow properties outside the mylonitic core. The juxtaposition of the ductile strain zone next to the brittle zone, which is bounded inside the two mylonitic cores, causes a significant elastic, mechanical, and fluid flow heterogeneity, which has important implications for crustal deformation and fluid flow and for the exploitation and use of geothermal energy and geologic waste storage. The results illustrate how physical characteristics of faults in crystalline rocks change in fault zones during the ductile to brittle transitions.

  7. Time-dependent brittle deformation at Mt. Etna volcano

    NASA Astrophysics Data System (ADS)

    Baud, Patrick; Heap, Michael; Meredith, Philip; Vinciguerra, Sergio; Bell, Andrew; Main, Ian

    2010-05-01

    Time-dependent weakening mechanisms, leading to slow fracturing, are likely to act during the build up to flank eruptions at Mt. Etna volcano and are potentially a primary control on pre-eruptive patterns of seismicity and deformation. Due to the high permeability of its volcanic rocks, the volcanic edifice hosts a large water reservoir (Ogniben, 1966). The presence of a fluid phase in cracks within rock has been shown to dramatically affect both mechanical and chemical interactions. Chemically, it promotes time-dependent brittle deformation through such mechanisms as stress corrosion cracking that allows rocks to deform at stresses far below their short-term failure strength. Such crack growth is highly non-linear and accelerates towards dynamic failure over extended periods of time, even under constant applied stress; a phenomenon known as ‘brittle creep'. Here we report results from a study of time-dependent brittle creep in water-saturated samples of Etna basalt (EB) under triaxial stress conditions (confining pressure of 50 MPa and pore fluid pressure of 20 MPa). Samples of EB were loaded at a constant strain rate of 10-5 s-1 to a pre-determined percentage of the short-term strength and left to deform under constant stress until failure. Crack damage evolution was monitored throughout each experiment by measuring the independent damage proxies of axial strain, pore volume change and output of acoustic emission (AE) energy, during brittle creep of creep strain rates ranging over four orders of magnitude. Our data not only demonstrates that basalt creeps in the brittle regime but also that the applied differential stress exerts a crucial influence on both time-to-failure and creep strain rate in EB. Furthermore, stress corrosion is considered to be responsible for the acceleratory cracking and seismicity prior to volcanic eruptions and is invoked as an important mechanism in forecasting models. Stress-stepping creep experiments were then performed to allow the

  8. Micromechanisms of intergranular brittle ftacture in intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Vitek, V.

    1991-06-01

    Grain boundaries in intermetallic compounds such as Ni3A1 are inherently brittle. The reason is usually sought in grain boundary cohesion but in metals even brittle fracture is accompanied by some local plasticity and thus not only cohesion but also dislocation mobility in the boundary region need to be studied. We first discuss here the role of an irreversible shear deformation at the crack tip during microcrack propagation assuming that these two processes are concomitant. It is shown that a pre-existing crack cannot propagate in a brittle manner once the dislocation emission occurs. However, if a microcrack nucleates during loading it can propagate concurrently with the development of the irreversible shear deformation at the crack tip. The latter is then the major energy dissipating process. In the second part of this paper we present results of atomistic studies of grain boundaries in Ni3A1 and CU3Au which suggest that substantial structural differences exist between strongly and weakly ordered L12 alloys. We discuss then the consequence of these differences for intergranular brittleness in the framework of the above model for microcrack propagation. On this basis we propose an explanation for the intrinsic intergranular brittleness in some L12 alloys and relate it directly to the strength of ordering. Les joints de grains dans les composés intermétalliques de type Ni3AI sont de nature fragile. L'origine de cette fragilité est habituellement dans la cohésion des joints de grains. Dans les métaux, cependant, même la rupture fragile est accompagnée d'une certaine déformation plastique locale, de telle sorte que non seulement la cohésion mais aussi la mobilité des dislocations près des joints doit être étudiée. Nous discutons d'abord le rôle d'une déformation en cisaillement irréversible en tête de fissure pendant la propagation de cette fissure, en supposant que les deux processus sont concomitants. Nous montrons qu'une fissure préexistante ne

  9. Extra-electron induced covalent strengthening and generalization of intrinsic ductile-to-brittle criterion

    PubMed Central

    Niu, Haiyang; Chen, Xing-Qiu; Liu, Peitao; Xing, Weiwei; Cheng, Xiyue; Li, Dianzhong; Li, Yiyi

    2012-01-01

    Traditional strengthening ways, such as strain, precipitation, and solid-solution, come into effect by pinning the motion of dislocation. Here, through first-principles calculations we report on an extra-electron induced covalent strengthening mechanism, which alters chemical bonding upon the introduction of extra-valence electrons in the matrix of parent materials. It is responsible for the brittle and high-strength properties of Al12W-type compounds featured by the typical fivefold icosahedral cages, which are common for quasicrystals and bulk metallic glasses (BMGs). In combination with this mechanism, we generalize ductile-to-brittle criterion in a universal hyperbolic form by integrating the classical Pettifor's Cauchy pressure with Pugh's modulus ratio for a wide variety of materials with cubic lattices. This study provides compelling evidence to correlate Pugh's modulus ratio with hardness of materials and may have implication for understanding the intrinsic brittleness of quasicrystals and BMGs. PMID:23056910

  10. Extra-electron induced covalent strengthening and generalization of intrinsic ductile-to-brittle criterion.

    PubMed

    Niu, Haiyang; Chen, Xing-Qiu; Liu, Peitao; Xing, Weiwei; Cheng, Xiyue; Li, Dianzhong; Li, Yiyi

    2012-01-01

    Traditional strengthening ways, such as strain, precipitation, and solid-solution, come into effect by pinning the motion of dislocation. Here, through first-principles calculations we report on an extra-electron induced covalent strengthening mechanism, which alters chemical bonding upon the introduction of extra-valence electrons in the matrix of parent materials. It is responsible for the brittle and high-strength properties of Al(12)W-type compounds featured by the typical fivefold icosahedral cages, which are common for quasicrystals and bulk metallic glasses (BMGs). In combination with this mechanism, we generalize ductile-to-brittle criterion in a universal hyperbolic form by integrating the classical Pettifor's Cauchy pressure with Pugh's modulus ratio for a wide variety of materials with cubic lattices. This study provides compelling evidence to correlate Pugh's modulus ratio with hardness of materials and may have implication for understanding the intrinsic brittleness of quasicrystals and BMGs.

  11. A unified phase-field theory for the mechanics of damage and quasi-brittle failure

    NASA Astrophysics Data System (ADS)

    Wu, Jian-Ying

    2017-06-01

    Being one of the most promising candidates for the modeling of localized failure in solids, so far the phase-field method has been applied only to brittle fracture with very few exceptions. In this work, a unified phase-field theory for the mechanics of damage and quasi-brittle failure is proposed within the framework of thermodynamics. Specifically, the crack phase-field and its gradient are introduced to regularize the sharp crack topology in a purely geometric context. The energy dissipation functional due to crack evolution and the stored energy functional of the bulk are characterized by a crack geometric function of polynomial type and an energetic degradation function of rational type, respectively. Standard arguments of thermodynamics then yield the macroscopic balance equation coupled with an extra evolution law of gradient type for the crack phase-field, governed by the aforesaid constitutive functions. The classical phase-field models for brittle fracture are recovered as particular examples. More importantly, the constitutive functions optimal for quasi-brittle failure are determined such that the proposed phase-field theory converges to a cohesive zone model for a vanishing length scale. Those general softening laws frequently adopted for quasi-brittle failure, e.g., linear, exponential, hyperbolic and Cornelissen et al. (1986) ones, etc., can be reproduced or fit with high precision. Except for the internal length scale, all the other model parameters can be determined from standard material properties (i.e., Young's modulus, failure strength, fracture energy and the target softening law). Some representative numerical examples are presented for the validation. It is found that both the internal length scale and the mesh size have little influences on the overall global responses, so long as the former can be well resolved by sufficiently fine mesh. In particular, for the benchmark tests of concrete the numerical results of load versus displacement

  12. Prediction of Brittle Failure for TBM Tunnels in Anisotropic Rock: A Case Study from Northern Norway

    NASA Astrophysics Data System (ADS)

    Dammyr, Øyvind

    2016-06-01

    Prediction of spalling and rock burst is especially important for hard rock TBM tunneling, because failure can have larger impact than in a drill and blast tunnel and ultimately threaten excavation feasibility. The majority of research on brittle failure has focused on rock types with isotropic behavior. This paper gives a review of existing theory and its application before a 3.5-m-diameter TBM tunnel in foliated granitic gneiss is used as a case to study brittle failure characteristics of anisotropic rock. Important aspects that should be considered in order to predict brittle failure in anisotropic rock are highlighted. Foliation is responsible for considerable strength anisotropy and is believed to influence the preferred side of v-shaped notch development in the investigated tunnel. Prediction methods such as the semi- empirical criterion, the Hoek- Brown brittle parameters, and the non-linear damage initiation and spalling limit method give reliable results; but only as long as the angle between compression axis and foliation in uniaxial compressive tests is relevant, dependent on the relation between tunnel trend/plunge, strike/dip of foliation, and tunnel boundary stresses. It is further demonstrated that local in situ stress variations, for example, due to the presence of discontinuities, can have profound impact on failure predictions. Other carefully documented case studies into the brittle failure nature of rock, in particular anisotropic rock, are encouraged in order to expand the existing and relatively small database. This will be valuable for future TBM planning and construction stages in highly stressed brittle anisotropic rock.

  13. Organizational management practices for achieving software process improvement

    NASA Technical Reports Server (NTRS)

    Kandt, Ronald Kirk

    2004-01-01

    The crisis in developing software has been known for over thirty years. Problems that existed in developing software in the early days of computing still exist today. These problems include the delivery of low-quality products, actual development costs that exceed expected development costs, and actual development time that exceeds expected development time. Several solutions have been offered to overcome out inability to deliver high-quality software, on-time and within budget. One of these solutions involves software process improvement. However, such efforts often fail because of organizational management issues. This paper discusses business practices that organizations should follow to improve their chances of initiating and sustaining successful software process improvement efforts.

  14. Size-Dependent Brittle-to-Ductile Transition in Silica Glass Nanofibers.

    PubMed

    Luo, Junhang; Wang, Jiangwei; Bitzek, Erik; Huang, Jian Yu; Zheng, He; Tong, Limin; Yang, Qing; Li, Ju; Mao, Scott X

    2016-01-13

    Silica (SiO2) glass, an essential material in human civilization, possesses excellent formability near its glass-transition temperature (Tg > 1100 °C). However, bulk SiO2 glass is very brittle at room temperature. Here we show a surprising brittle-to-ductile transition of SiO2 glass nanofibers at room temperature as its diameter reduces below 18 nm, accompanied by ultrahigh fracture strength. Large tensile plastic elongation up to 18% can be achieved at low strain rate. The unexpected ductility is due to a free surface affected zone in the nanofibers, with enhanced ionic mobility compared to the bulk that improves ductility by producing more bond-switching events per irreversible bond loss under tensile stress. Our discovery is fundamentally important for understanding the damage tolerance of small-scale amorphous structures.

  15. Microstructural Modeling of Brittle Materials for Enhanced Performance and Reliability.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Teague, Melissa Christine; Teague, Melissa Christine; Rodgers, Theron

    Brittle failure is often influenced by difficult to measure and variable microstructure-scale stresses. Recent advances in photoluminescence spectroscopy (PLS), including improved confocal laser measurement and rapid spectroscopic data collection have established the potential to map stresses with microscale spatial resolution (%3C2 microns). Advanced PLS was successfully used to investigate both residual and externally applied stresses in polycrystalline alumina at the microstructure scale. The measured average stresses matched those estimated from beam theory to within one standard deviation, validating the technique. Modeling the residual stresses within the microstructure produced general agreement in comparison with the experimentally measured results. Microstructure scale modelingmore » is primed to take advantage of advanced PLS to enable its refinement and validation, eventually enabling microstructure modeling to become a predictive tool for brittle materials.« less

  16. Software project management tools in global software development: a systematic mapping study.

    PubMed

    Chadli, Saad Yasser; Idri, Ali; Ros, Joaquín Nicolás; Fernández-Alemán, José Luis; de Gea, Juan M Carrillo; Toval, Ambrosio

    2016-01-01

    Global software development (GSD) which is a growing trend in the software industry is characterized by a highly distributed environment. Performing software project management (SPM) in such conditions implies the need to overcome new limitations resulting from cultural, temporal and geographic separation. The aim of this research is to discover and classify the various tools mentioned in literature that provide GSD project managers with support and to identify in what way they support group interaction. A systematic mapping study has been performed by means of automatic searches in five sources. We have then synthesized the data extracted and presented the results of this study. A total of 102 tools were identified as being used in SPM activities in GSD. We have classified these tools, according to the software life cycle process on which they focus and how they support the 3C collaboration model (communication, coordination and cooperation). The majority of the tools found are standalone tools (77%). A small number of platforms (8%) also offer a set of interacting tools that cover the software development lifecycle. Results also indicate that SPM areas in GSD are not adequately supported by corresponding tools and deserve more attention from tool builders.

  17. Study on electroplating technology of diamond tools for machining hard and brittle materials

    NASA Astrophysics Data System (ADS)

    Cui, Ying; Chen, Jian Hua; Sun, Li Peng; Wang, Yue

    2016-10-01

    With the development of the high speed cutting, the ultra-precision machining and ultrasonic vibration technique in processing hard and brittle material , the requirement of cutting tools is becoming higher and higher. As electroplated diamond tools have distinct advantages, such as high adaptability, high durability, long service life and good dimensional stability, the cutting tools are effective and extensive used in grinding hard and brittle materials. In this paper, the coating structure of electroplating diamond tool is described. The electroplating process flow is presented, and the influence of pretreatment on the machining quality is analyzed. Through the experimental research and summary, the reasonable formula of the electrolyte, the electroplating technologic parameters and the suitable sanding method were determined. Meanwhile, the drilling experiment on glass-ceramic shows that the electroplating process can effectively improve the cutting performance of diamond tools. It has laid a good foundation for further improving the quality and efficiency of the machining of hard and brittle materials.

  18. Experimental investigation of the brittle-viscous transition in mafic rocks - Interplay between fracturing, reaction, and viscous deformation

    NASA Astrophysics Data System (ADS)

    Marti, Sina; Stünitz, Holger; Heilbronner, Renée; Plümper, Oliver; Drury, Martyn

    2017-12-01

    Rock deformation experiments are performed on fault gouge fabricated from 'Maryland Diabase' rock powder to investigate the transition from dominant brittle to dominant viscous behaviour. At the imposed strain rates of γ˙ = 3 ·10-5 - 3 ·10-6 s-1, the transition is observed in the temperature range of (600 °C < T < 800 °C) at confining pressures of (0.5 GPa ≤ Pc ≤ 1.5 GPa). The transition thereby takes place by a switch from brittle fracturing and cataclastic flow to viscous dissolution-precipitation creep and grain boundary sliding. Mineral reactions and resulting grain size refinement by nucleation are observed to be critical processes for the switch to viscous deformation, i.e., grain size sensitive creep. In the transitional regime, the mechanical response of the sample is a mixed-mode between brittle and viscous rheology and microstructures associated with both brittle and viscous deformation are observed. As grain size reduction by reaction and nucleation is a time dependent process, the brittle-viscous transition is not only a function of T but to a large extent also of microstructural evolution.

  19. Brittle and ductile friction modeling of triggered tremor in Guerrero, Mexico

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Daub, E. G.; Wu, C.

    2017-12-01

    Low frequency earthquakes (LFEs), which make up the highest amplitude portions of non-volcanic tremor, are mostly found along subduction zones at a depth of 30-40km which is typically within the brittle-ductile transition zone. Previous studies in Guerrero, Mexico demonstrated a relationship between the bursts of LFEs and the contact states of fault interfaces, and LFEs that triggered by different mechanisms were observed along different parts of the subduction zone. To better understand the physics of fault interfaces at depth, especially the influence of contact states of these asperities, we use a brittle-ductile friction model to simulate the occurrence of LFE families from a model of frictional failure and slip. This model takes the stress state, slip rate, perturbation force, fault area, and brittle-ductile frictional contact characteristics and simulates the times and amplitudes of LFE occurrence for a single family. We examine both spontaneous and triggered tremor occurrence by including stresses due to external seismic waves, such as the 2010 Maule Earthquake, which triggered tremor and slow slip on the Guerrero section of the subduction zone. By comparing our model output with detailed observations of LFE occurrence, we can determine valuable constraints on the frictional properties of subduction zones at depth.

  20. Sometimes two arms are enough--an unusual life-stage in brittle stars (Echinodermata: Ophiuroidea).

    PubMed

    Stöhr, Sabine; Alme, Øydis

    2015-08-03

    Off West Africa (Angola-Morocco), benthos samples were collected in the years 2005-2012. These contained 124 specimens of brittle stars with two long arms and three extremely short or absent arms and an elongated, narrow disc. These unusual brittle stars, as well as 33 specimens with five fully developed arms, were identified as Amphiura ungulata. The specimens with unequal arms were juvenile stages, whereas adults had five equal arms. The large number of specimens with unequal arms suggests that this condition is not the result of damage and regeneration, but a normal growth pattern in this species. This study documents the morphology by SEM, amends the species description, and discusses possible explanations for the evolution of this condition. Although brittle star species with unequal arm growth have been reported, this is an extreme case that was unknown before this study.

  1. A theoretical derivation of the dilatancy equation for brittle rocks based on Maxwell model

    NASA Astrophysics Data System (ADS)

    Li, Jie; Huang, Houxu; Wang, Mingyang

    2017-03-01

    In this paper, the micro-cracks in the brittle rocks are assumed to be penny shaped and evenly distributed; the damage and dilatancy of the brittle rocks is attributed to the growth and expansion of numerous micro-cracks under the local tensile stress. A single crack's behaviour under the local tensile stress is generalized to all cracks based on the distributed damage mechanics. The relationship between the local tensile stress and the external loading is derived based on the Maxwell model. The damage factor corresponding to the external loading is represented using the p-alpha ( p- α) model. A dilatancy equation that can build up a link between the external loading and the rock dilatancy is established. A test of dilatancy of a brittle rock under triaxial compression is conducted; the comparison between experimental results and our theoretical results shows good consistency.

  2. Guidelines for Design and Analysis of Large, Brittle Spacecraft Components

    NASA Technical Reports Server (NTRS)

    Robinson, E. Y.

    1993-01-01

    There were two related parts to this work. The first, conducted at The Aerospace Corporation was to develop and define methods for integrating the statistical theory of brittle strength with conventional finite element stress analysis, and to carry out a limited laboratory test program to illustrate the methods. The second part, separately funded at Aerojet Electronic Systems Division, was to create the finite element postprocessing program for integrating the statistical strength analysis with the structural analysis. The second part was monitored by Capt. Jeff McCann of USAF/SMC, as Special Study No.11, which authorized Aerojet to support Aerospace on this work requested by NASA. This second part is documented in Appendix A. The activity at Aerojet was guided by the Aerospace methods developed in the first part of this work. This joint work of Aerospace and Aerojet stemmed from prior related work for the Defense Support Program (DSP) Program Office, to qualify the DSP sensor main mirror and corrector lens for flight as part of a shuttle payload. These large brittle components of the DSP sensor are provided by Aerojet. This document defines rational methods for addressing the structural integrity and safety of large, brittle, payload components, which have low and variable tensile strength and can suddenly break or shatter. The methods are applicable to the evaluation and validation of such components, which, because of size and configuration restrictions, cannot be validated by direct proof test.

  3. Software Testing and Verification in Climate Model Development

    NASA Technical Reports Server (NTRS)

    Clune, Thomas L.; Rood, RIchard B.

    2011-01-01

    Over the past 30 years most climate models have grown from relatively simple representations of a few atmospheric processes to a complex multi-disciplinary system. Computer infrastructure over that period has gone from punch card mainframes to modem parallel clusters. Model implementations have become complex, brittle, and increasingly difficult to extend and maintain. Existing verification processes for model implementations rely almost exclusively upon some combination of detailed analysis of output from full climate simulations and system-level regression tests. In additional to being quite costly in terms of developer time and computing resources, these testing methodologies are limited in terms of the types of defects that can be detected, isolated and diagnosed. Mitigating these weaknesses of coarse-grained testing with finer-grained "unit" tests has been perceived as cumbersome and counter-productive. In the commercial software sector, recent advances in tools and methodology have led to a renaissance for systematic fine-grained testing. We discuss the availability of analogous tools for scientific software and examine benefits that similar testing methodologies could bring to climate modeling software. We describe the unique challenges faced when testing complex numerical algorithms and suggest techniques to minimize and/or eliminate the difficulties.

  4. Software Innovation in a Mission Critical Environment

    NASA Technical Reports Server (NTRS)

    Fredrickson, Steven

    2015-01-01

    Operating in mission-critical environments requires trusted solutions, and the preference for "tried and true" approaches presents a potential barrier to infusing innovation into mission-critical systems. This presentation explores opportunities to overcome this barrier in the software domain. It outlines specific areas of innovation in software development achieved by the Johnson Space Center (JSC) Engineering Directorate in support of NASA's major human spaceflight programs, including International Space Station, Multi-Purpose Crew Vehicle (Orion), and Commercial Crew Programs. Software engineering teams at JSC work with hardware developers, mission planners, and system operators to integrate flight vehicles, habitats, robotics, and other spacecraft elements for genuinely mission critical applications. The innovations described, including the use of NASA Core Flight Software and its associated software tool chain, can lead to software that is more affordable, more reliable, better modelled, more flexible, more easily maintained, better tested, and enabling of automation.

  5. From Bridges and Rockets, Lessons for Software Systems

    NASA Technical Reports Server (NTRS)

    Holloway, C. Michael

    2004-01-01

    Although differences exist between building software systems and building physical structures such as bridges and rockets, enough similarities exist that software engineers can learn lessons from failures in traditional engineering disciplines. This paper draws lessons from two well-known failures the collapse of the Tacoma Narrows Bridge in 1940 and the destruction of the space shuttle Challenger in 1986 and applies these lessons to software system development. The following specific applications are made: (1) the verification and validation of a software system should not be based on a single method, or a single style of methods; (2) the tendency to embrace the latest fad should be overcome; and (3) the introduction of software control into safety-critical systems should be done cautiously.

  6. The challenges of numerically simulating analogue brittle thrust wedges

    NASA Astrophysics Data System (ADS)

    Buiter, Susanne; Ellis, Susan

    2017-04-01

    Fold-and-thrust belts and accretionary wedges form when sedimentary and crustal rocks are compressed into thrusts and folds in the foreland of an orogen or at a subduction trench. For over a century, analogue models have been used to investigate the deformation characteristics of such brittle wedges. These models predict wedge shapes that agree with analytical critical taper theory and internal deformation structures that well resemble natural observations. In a series of comparison experiments for thrust wedges, called the GeoMod2004 (1,2) and GeoMod2008 (3,4) experiments, it was shown that different numerical solution methods successfully reproduce sandbox thrust wedges. However, the GeoMod2008 benchmark also pointed to the difficulties of representing frictional boundary conditions and sharp velocity discontinuities with continuum numerical methods, in addition to the well-known challenges of numerical plasticity. Here we show how details in the numerical implementation of boundary conditions can substantially impact numerical wedge deformation. We consider experiment 1 of the GeoMod2008 brittle thrust wedge benchmarks. This experiment examines a triangular thrust wedge in the stable field of critical taper theory that should remain stable, that is, without internal deformation, when sliding over a basal frictional surface. The thrust wedge is translated by lateral displacement of a rigid mobile wall. The corner between the mobile wall and the subsurface is a velocity discontinuity. Using our finite-element code SULEC, we show how different approaches to implementing boundary friction (boundary layer or contact elements) and the velocity discontinuity (various smoothing schemes) can cause the wedge to indeed translate in a stable manner or to undergo internal deformation (which is a fail). We recommend that numerical studies of sandbox setups not only report the details of their implementation of boundary conditions, but also document the modelling attempts that

  7. Micromechanisms of brittle fracture: STM, TEM and electron channeling analysis. Final report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gerberich, W.W.

    1997-01-01

    The original thrust of this grant was to apply newly developed techniques in scanning tunneling and transmission electron microscopy to elucidate the mechanism of brittle fracture. This grant spun-off several new directions in that some of the findings on bulk structural materials could be utilized on thin films or intermetallic single crystals. Modeling and material evaluation efforts in this grant are represented in a figure. Out of this grant evolved the field the author has designated as Contact Fracture Mechanics. By appropriate modeling of stress and strain distribution fields around normal indentations or scratch tracks, various measures of thin filmmore » fracture or decohesion and brittle fracture of low ductility intermetallics is possible. These measures of fracture resistance in small volumes are still evolving and as such no standard technique or analysis has been uniformly accepted. For brittle ceramics and ceramic films, there are a number of acceptable analyses such as those published by Lawn, Evans and Hutchinson. For more dissipative systems involving metallic or polymeric films and/or substrates, there is still much to be accomplished as can be surmised from some of the findings in the present grant. In Section 2 the author reviews the funding history and accomplishments associated mostly with bulk brittle fracture. This is followed by Section 3 which covers more recent work on using novel techniques to evaluate fracture in low ductility single crystals or thin films using micromechanical probes. Basically Section 3 outlines how the recent work fits in with the goals of defining contact fracture mechanics and gives an overview of how the several examples in Section 4 (the Appendices) fit into this framework.« less

  8. Rock Drilling Performance Evaluation by an Energy Dissipation Based Rock Brittleness Index

    NASA Astrophysics Data System (ADS)

    Munoz, H.; Taheri, A.; Chanda, E. K.

    2016-08-01

    To reliably estimate drilling performance both tool-rock interaction laws along with a proper rock brittleness index are required to be implemented. In this study, the performance of a single polycrystalline diamond compact (PDC) cutter cutting and different drilling methods including PDC rotary drilling, roller-cone rotary drilling and percussive drilling were investigated. To investigate drilling performance by rock strength properties, laboratory PDC cutting tests were performed on different rocks to obtain cutting parameters. In addition, results of laboratory and field drilling on different rocks found elsewhere in literature were used. Laboratory and field cutting and drilling test results were coupled with values of a new rock brittleness index proposed herein and developed based on energy dissipation withdrawn from the complete stress-strain curve in uniaxial compression. To quantify cutting and drilling performance, the intrinsic specific energy in rotary-cutting action, i.e. the energy consumed in pure cutting action, and drilling penetration rate values in percussive action were used. The results show that the new energy-based brittleness index successfully describes the performance of different cutting and drilling methods and therefore is relevant to assess drilling performance for engineering applications.

  9. A comprehensive method for the fracability evaluation of shale combined with brittleness and stress sensitivity

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoqiong; Ge, Hongkui; Wang, Daobing; Wang, Jianbo; Chen, Hao

    2017-12-01

    An effective fracability evaluation on the fracture network is key to the whole process of shale gas exploitation. At present, neither a standard criteria nor a generally accepted evaluation method exist. Well log and laboratory results have shown that the commonly used brittleness index calculated from the mineralogy composition is not entirely consistent with that obtained from the elastic modulus of the rock, and is sometimes even contradictory. The brittle mineral reflects the brittleness of the rock matrix, and the stress sensitivity of the wave velocity reflects the development degree of the natural fracture system. They are both key factors in controlling the propagating fracture morphology. Thus, in this study, a novel fracability evaluation method of shale was developed combining brittleness and stress sensitivity. Based on this method, the fracability of three shale gas plays were evaluated. The cored cylindrical samples were loaded under uniaxial stress up to 30 MPa and the compressional wave velocities were obtained along the axis stress direction at each MPa stress. From the stress velocity evolution, the stress sensitivity coefficients could be obtained. Our results showed that the fracability of Niutitang shale is better than that of Lujiaping shale, and the fracability of Lujiaping shale is better than Longmaxi shale. This result is in good agreement with acoustic emission activity measurements. The new fracability evaluation method enables a comprehensive reflection of the characteristics of rock matrix brittleness and the natural fracture system. This work is valuable for the evaluation of hydraulic fracturing effects in unconventional oil and gas reservoirs in the future.

  10. Pathways to lean software development: An analysis of effective methods of change

    NASA Astrophysics Data System (ADS)

    Hanson, Richard D.

    This qualitative Delphi study explored the challenges that exist in delivering software on time, within budget, and with the original scope identified. The literature review identified many attempts over the past several decades to reform the methods used to develop software. These attempts found that the classical waterfall method, which is firmly entrenched in American business today was to blame for this difficulty (Chatterjee, 2010). Each of these proponents of new methods sought to remove waste, lighten out the process, and implement lean principles in software development. Through this study, the experts evaluated the barriers to effective development principles and defined leadership qualities necessary to overcome these barriers. The barriers identified were issues of resistance to change, risk and reward issues, and management buy-in. Thirty experts in software development from several Fortune 500 companies across the United States explored each of these issues in detail. The conclusion reached by these experts was that visionary leadership is necessary to overcome these challenges.

  11. Prediction of brittleness based on anisotropic rock physics model for kerogen-rich shale

    NASA Astrophysics Data System (ADS)

    Qian, Ke-Ran; He, Zhi-Liang; Chen, Ye-Quan; Liu, Xi-Wu; Li, Xiang-Yang

    2017-12-01

    The construction of a shale rock physics model and the selection of an appropriate brittleness index ( BI) are two significant steps that can influence the accuracy of brittleness prediction. On one hand, the existing models of kerogen-rich shale are controversial, so a reasonable rock physics model needs to be built. On the other hand, several types of equations already exist for predicting the BI whose feasibility needs to be carefully considered. This study constructed a kerogen-rich rock physics model by performing the selfconsistent approximation and the differential effective medium theory to model intercoupled clay and kerogen mixtures. The feasibility of our model was confirmed by comparison with classical models, showing better accuracy. Templates were constructed based on our model to link physical properties and the BI. Different equations for the BI had different sensitivities, making them suitable for different types of formations. Equations based on Young's Modulus were sensitive to variations in lithology, while those using Lame's Coefficients were sensitive to porosity and pore fluids. Physical information must be considered to improve brittleness prediction.

  12. Time-dependent brittle deformation (creep) at Mt. Etna volcano

    NASA Astrophysics Data System (ADS)

    Heap, M. J.; Baud, P.; Meredith, P. G.; Vinciguerra, S.; Bell, A. F.; Main, I. G.

    2009-04-01

    Mt. Etna is the largest and most active volcano in Europe. Time-dependent weakening mechanisms, leading to slow fracturing, have been shown to act during pre-eruptive patterns of flank eruptions at Mt. Etna volcano. Due to the high permeability of its volcanic rocks, the volcanic edifice hosts one of the biggest hydrogeologic reservoirs of Sicily (Ogniben, 1966). The presence of a fluid phase in cracks within rock has been shown to dramatically affect both mechanical and chemical interactions. Chemically, it promotes time-dependent brittle deformation through such mechanisms as stress corrosion cracking that allows rocks to deform at stresses far below their short-term failure strength. Such crack growth is highly non-linear and accelerates towards dynamic failure over extended periods of time, even under constant applied stress; a phenomenon known as ‘brittle creep'. Here we report results from a study of time-dependent brittle creep in water-saturated samples of Etna basalt (EB) under triaxial stress conditions (confining pressure of 50 MPa and pore fluid pressure of 20 MPa). Samples of EB were loaded at a constant strain rate of 10-5 s-1 to a pre-determined percentage of the short-term strength and left to deform under constant stress until failure. Crack damage evolution was monitored throughout each experiment by measuring the independent damage proxies of axial strain, pore volume change and output of acoustic emission (AE) energy, during brittle creep of creep strain rates ranging over four orders of magnitude. Our data not only demonstrates that basalt creeps in the brittle regime but also that the applied differential stress exerts a crucial influence on both time-to-failure and creep strain rate in EB. Furthermore, stress corrosion is considered to be responsible for the acceleratory cracking and seismicity prior to volcanic eruptions and is invoked as an important mechanism in forecasting models. Stress-stepping creep experiments were then performed to

  13. Time-dependent Brittle Deformation in Etna Basalt

    NASA Astrophysics Data System (ADS)

    Heap, M. J.; Baud, P.; Meredith, P. G.; Vinciguerra, S.; Bell, A. F.; Main, I. G.

    2008-12-01

    Mt Etna is the largest and most active volcano in Europe. Due to the high permeability of its volcanic rocks, the volcanic edifice hosts one of the biggest hydrogeologic reservoirs of Sicily (Ogniben, 1966). Pre-eruptive patterns of flank eruptions, closely monitored by means of ground deformation and seismicity, revealed the slow development of fracture systems at different altitudes, marked by repeated bursts of seismicity and accelerating/decelerating deformation patterns acting over the scale of months to days. The presence of a fluid phase in cracks within rock has been shown to dramatically affect both mechanical and chemical interactions. Chemically, it promotes time-dependent brittle deformation through such mechanisms as stress corrosion cracking that allows rocks to deform at stresses far below their short-term failure strength. Such crack growth is highly non-linear and accelerates towards dynamic failure over extended periods of time, even under constant applied stress; a phenomenon known as 'brittle creep'. Stress corrosion is considered to be responsible for the acceleratory cracking and seismicity prior to volcanic eruptions and is invoked as an important mechanism in forecasting models. Here we report results from a study of time-dependent brittle creep in water-saturated samples of Etna basalt (EB) under triaxial stress conditions (confining pressure of 50 MPa and pore fluid pressure of 20 MPa). Samples of EB were loaded at a constant strain rate of 10-5 s-1 to a pre-determined percentage of the short- term strength and left to deform under constant stress until failure. Crack damage evolution was monitored throughout each experiment by measuring the independent damage proxies of axial strain, pore volume change and output of acoustic emission (AE) energy, during brittle creep of creep strain rates ranging over four orders of magnitude. Our data demonstrate that the applied differential stress exerts a crucial influence on both time-to-failure and

  14. Numerical model of thermo-mechanical coupling for the tensile failure process of brittle materials

    NASA Astrophysics Data System (ADS)

    Fu, Yu; Wang, Zhe; Ren, Fengyu; Wang, Daguo

    2017-10-01

    A numerical model of thermal cracking with a thermo-mechanical coupling effect was established. The theory of tensile failure and heat conduction is used to study the tensile failure process of brittle materials, such as rock and concrete under high temperature environment. The validity of the model is verified by thick-wall cylinders with analytical solutions. The failure modes of brittle materials under thermal stresses caused by temperature gradient and different thermal expansion coefficient were studied by using a thick-wall cylinder model and an embedded particle model, respectively. In the thick-wall cylinder model, different forms of cracks induced by temperature gradient were obtained under different temperature boundary conditions. In the embedded particle model, radial cracks were produced in the medium part with lower tensile strength when temperature increased because of the different thermal expansion coefficient. Model results are in good agreement with the experimental results, thereby providing a new finite element method for analyzing the thermal damage process and mechanism of brittle materials.

  15. Culture shock: Improving software quality

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    de Jong, K.; Trauth, S.L.

    1988-01-01

    The concept of software quality can represent a significant shock to an individual who has been developing software for many years and who believes he or she has been doing a high quality job. The very idea that software includes lines of code and associated documentation is foreign and difficult to grasp, at best. Implementation of a software quality program hinges on the concept that software is a product whose quality needs improving. When this idea is introduced into a technical community that is largely ''self-taught'' and has been producing ''good'' software for some time, a fundamental understanding of themore » concepts associated with software is often weak. Software developers can react as if to say, ''What are you talking about. What do you mean I'm not doing a good job. I haven't gotten any complaints about my code yetexclamation'' Coupling such surprise and resentment with the shock that software really is a product and software quality concepts do exist, can fuel the volatility of these emotions. In this paper, we demonstrate that the concept of software quality can indeed pose a culture shock to developers. We also show that a ''typical'' quality assurance approach, that of imposing a standard and providing inspectors and auditors to assure its adherence, contributes to this shock and detracts from the very goal the approach should achieve. We offer an alternative, adopted through experience, to implement a software quality program: cooperative assistance. We show how cooperation, education, consultation and friendly assistance can overcome this culture shock. 3 refs.« less

  16. Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation.

    PubMed

    Violay, M; Heap, M J; Acosta, M; Madonna, C

    2017-08-09

    Recently, projects have been proposed to engineer deep geothermal reservoirs in the ductile crust. To examine their feasibility, we performed high-temperature (up to 1000 °C), high-pressure (130 MPa) triaxial experiments on granite (initially-intact and shock-cooled samples) in which we measured the evolution of porosity during deformation. Mechanical data and post-mortem microstuctural characterisation (X-ray computed tomography and scanning electron microscopy) indicate that (1) the failure mode was brittle up to 900 °C (shear fracture formation) but ductile at 1000 °C (no strain localisation); (2) only deformation up to 800 °C was dilatant; (3) deformation at 900 °C was brittle but associated with net compaction due to an increase in the efficiency of crystal plastic processes; (4) ductile deformation at 1000 °C was compactant; (5) thermally-shocking the granite did not influence strength or failure mode. Our data show that, while brittle behaviour increases porosity, porosity loss is associated with both ductile behaviour and transitional behaviour as the failure mode evolves from brittle to ductile. Extrapolating our data to geological strain rates suggests that the brittle-ductile transition occurs at a temperature of 400 ± 100 °C, and is associated with the limit of fluid circulation in the deep continental crust.

  17. Description of new dry granular materials of variable cohesion and friction coefficient: Implications for laboratory modeling of the brittle crust

    NASA Astrophysics Data System (ADS)

    Abdelmalak, M. M.; Bulois, C.; Mourgues, R.; Galland, O.; Legland, J.-B.; Gruber, C.

    2016-08-01

    Cohesion and friction coefficient are fundamental parameters for scaling brittle deformation in laboratory models of geological processes. However, they are commonly not experimental variable, whereas (1) rocks range from cohesion-less to strongly cohesive and from low friction to high friction and (2) strata exhibit substantial cohesion and friction contrasts. This brittle paradox implies that the effects of brittle properties on processes involving brittle deformation cannot be tested in laboratory models. Solving this paradox requires the use of dry granular materials of tunable and controllable brittle properties. In this paper, we describe dry mixtures of fine-grained cohesive, high friction silica powder (SP) and low-cohesion, low friction glass microspheres (GM) that fulfill this requirement. We systematically estimated the cohesions and friction coefficients of mixtures of variable proportions using two independent methods: (1) a classic Hubbert-type shear box to determine the extrapolated cohesion (C) and friction coefficient (μ), and (2) direct measurements of the tensile strength (T0) and the height (H) of open fractures to calculate the true cohesion (C0). The measured values of cohesion increase from 100 Pa for pure GM to 600 Pa for pure SP, with a sub-linear trend of the cohesion with the mixture GM content. The two independent cohesion measurement methods, from shear tests and tension/extensional tests, yield very similar results of extrapolated cohesion (C) and show that both are robust and can be used independently. The measured values of friction coefficients increase from 0.5 for pure GM to 1.05 for pure SP. The use of these granular material mixtures now allows testing (1) the effects of cohesion and friction coefficient in homogeneous laboratory models and (2) testing the effect of brittle layering on brittle deformation, as demonstrated by preliminary experiments. Therefore, the brittle properties become, at last, experimental variables.

  18. Brittle Creep of Tournemire Shale: Orientation, Temperature and Pressure Dependences

    NASA Astrophysics Data System (ADS)

    Geng, Zhi; Bonnelye, Audrey; Dick, Pierre; David, Christian; Chen, Mian; Schubnel, Alexandre

    2017-04-01

    Time and temperature dependent rock deformation has both scientific and socio-economic implications for natural hazards, the oil and gas industry and nuclear waste disposal. During the past decades, most studies on brittle creep have focused on igneous rocks and porous sedimentary rocks. To our knowledge, only few studies have been carried out on the brittle creep behavior of shale. Here, we conducted a series of creep experiments on shale specimens coming from the French Institute for Nuclear Safety (IRSN) underground research laboratory located in Tournemire, France. Conventional tri-axial experiments were carried under two different temperatures (26˚ C, 75˚ C) and confining pressures (10 MPa, 80 MPa), for three orientations (σ1 along, perpendicular and 45˚ to bedding). Following the methodology developed by Heap et al. [2008], differential stress was first increased to ˜ 60% of the short term peak strength (10-7/s, Bonnelye et al. 2016), and then in steps of 5 to 10 MPa every 24 hours until brittle failure was achieved. In these long-term experiments (approximately 10 days), stress and strains were recorded continuously, while ultrasonic acoustic velocities were recorded every 1˜15 minutes, enabling us to monitor the evolution of elastic wave speed anisotropy. Temporal evolution of anisotropy was illustrated by inverting acoustic velocities to Thomsen parameters. Finally, samples were investigated post-mortem using scanning electron microscopy. Our results seem to contradict our traditional understanding of loading rate dependent brittle failure. Indeed, the brittle creep failure stress of our Tournemire shale samples was systematically observed ˜50% higher than its short-term peak strength, with larger final axial strain accumulated. At higher temperatures, the creep failure strength of our samples was slightly reduced and deformation was characterized with faster 'steady-state' creep axial strain rates at each steps, and larger final axial strain

  19. Probing the Statistical Validity of the Ductile-to-Brittle Transition in Metallic Nanowires Using GPU Computing.

    PubMed

    French, William R; Pervaje, Amulya K; Santos, Andrew P; Iacovella, Christopher R; Cummings, Peter T

    2013-12-10

    We perform a large-scale statistical analysis (>2000 independent simulations) of the elongation and rupture of gold nanowires, probing the validity and scope of the recently proposed ductile-to-brittle transition that occurs with increasing nanowire length [Wu et al. Nano Lett. 2012, 12, 910-914]. To facilitate a high-throughput simulation approach, we implement the second-moment approximation to the tight-binding (TB-SMA) potential within HOOMD-Blue, a molecular dynamics package which runs on massively parallel graphics processing units (GPUs). In a statistical sense, we find that the nanowires obey the ductile-to-brittle model quite well; however, we observe several unexpected features from the simulations that build on our understanding of the ductile-to-brittle transition. First, occasional failure behavior is observed that qualitatively differs from that predicted by the model prediction; this is attributed to stochastic thermal motion of the Au atoms and occurs at temperatures as low as 10 K. In addition, we also find that the ductile-to-brittle model, which was developed using classical dislocation theory, holds for nanowires as small as 3 nm in diameter. Finally, we demonstrate that the nanowire critical length is higher at 298 K relative to 10 K, a result that is not predicted by the ductile-to-brittle model. These results offer practical design strategies for adjusting nanowire failure and structure and also demonstrate that GPU computing is an excellent tool for studies requiring a large number of independent trajectories in order to fully characterize a system's behavior.

  20. Variation of depth to the brittle-ductile transition due to cooling of a midcrustal intrusion.

    USGS Publications Warehouse

    Gettings, M.E.

    1988-01-01

    The depth to the brittle-ductile transition in the crust is often defined by the intersection of a shear resistance relation in the brittle upper crust that increases linearly with depth and a power law relation for ductile flow in the lower crust that depends strongly on T. Transient variation of this depth caused by a magmatic intrusion at a depth near the regional transition can be modelled by a heat conduction model for a rectangular parallelepiped superimposed on a linear geothermal gradient. When parameters appropriate for the southeastern US are used, a moderate-sized intrusion is found to decrease the transition depth by as much as 7 km; significant variations last approx 10 m.y. Since the base of the seismogenic zone is identified with the brittle-ductile transition, these results imply that intrusions of late Tertiary age or younger could be important sources of clustered seismicity. -A.W.H.

  1. Controlled crack growth specimen for brittle systems

    NASA Technical Reports Server (NTRS)

    Calomino, Anthony M.; Brewer, David N.

    1990-01-01

    A pure Mode 1 fracture specimen and test procedure has been developed which provides extended, stable, through-thickness crack growth in ceramics and other brittle, nonmetallic materials. Fixed displacement loading, applied at the crack mouth, promotes stable crack extension by reducing the stored elastic strain energy. Extremely fine control of applied displacements is achieved by utilizing the Poisson's expansion of a compressively loaded cylindrical pin. Stable cracks were successfully grown in soda-lime glass and monolithic Al2O3 for lengths in excess of 20 mm without uncontrollable catastrophic failure.

  2. Controlled crack growth specimen for brittle systems

    NASA Technical Reports Server (NTRS)

    Calomino, Anthony M.; Brewer, David N.

    1992-01-01

    A pure Mode 1 fracture specimen and test procedure has been developed which provides extended, stable, through-thickness crack growth in ceramics and other brittle, nonmetallic materials. Fixed displacement loading, applied at the crack mouth, promotes stable crack extension by reducing the stored elastic strain energy. Extremely fine control of applied displacements is achieved by utilizing the Poisson's expansion of a compressively loaded cylindrical pin. Stable cracks were successfully grown in soda-lime glass and monolithic Al2O3 for lengths in excess of 2O mm without uncontrollable catastrophic failure.

  3. Aerogel: Tile Composites Toughen a Brittle Superinsulation

    NASA Technical Reports Server (NTRS)

    White, Susan; Rasky, Daniel; Arnold, James O. (Technical Monitor)

    1998-01-01

    Pure aerogels, though familiar in the laboratory for decades as exotic lightweight insulators with unusual physical properties, have had limited industrial applications due to their low strength and high brittleness. Composites formed of aerogels and the ceramic fiber matrices like those used as space shuttle tiles bypass the fragility of pure aerogels and can enhance the performance of space shuttle tiles in their harsh operating environment. Using a layer of aerogel embedded in a tile may open up a wide range of applications where thermal insulation, gas convection control and mechanical strength matter.

  4. Aerogel: Tile Composites Toughen a Brittle Superinsulation

    NASA Technical Reports Server (NTRS)

    White, Susan; Rasky, Daniel; Arnold, James O. (Technical Monitor)

    1998-01-01

    Pure aerogels, though familiar in the laboratory for decades as exotic lightweight insulators with unusual physical properties, have had limited industrial applications due to their low strength and high brittleness. Composites formed of aerogels and the ceramic fiber matrices used as space shuttle tiles bypass the fragility of pure aerogels and can enhance the performance of space shuttle tiles in their harsh operating environment. Using a layer of aerogel embedded in a tile may open up a wide range of applications where thermal insulation, gas convection control and mechanical strength matter.

  5. Brittle-to-ductile transition of lithiated silicon electrodes: Crazing to stable nanopore growth.

    PubMed

    Wang, Haoran; Wang, Xueju; Xia, Shuman; Chew, Huck Beng

    2015-09-14

    Using first principle calculations, we uncover the underlying mechanisms explaining the brittle-to-ductile transition of LixSi electrodes in lithium ion batteries with increasing Li content. We show that plasticity initiates at x = ∼ 0.5 with the formation of a craze-like network of nanopores separated by Si-Si bonds, while subsequent failure is still brittle-like with the breaking of Si-Si bonds. Transition to ductile behavior occurs at x ⩾ 1 due to the increased density of highly stretchable Li-Li bonds, which delays nanopore formation and stabilizes nanopore growth. Collapse of the nanopores during unloading of the LixSi alloys leads to significant strain recovery.

  6. Brittle fracture phase-field modeling of a short-rod specimen

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Escobar, Ivana; Tupek, Michael R.; Bishop, Joseph E.

    2015-09-01

    Predictive simulation capabilities for modeling fracture evolution provide further insight into quantities of interest in comparison to experimental testing. Based on the variational approach to fracture, the advent of phase-field modeling achieves the goal to robustly model fracture for brittle materials and captures complex crack topologies in three dimensions.

  7. A generalized law for brittle deformation of Westerly granite

    USGS Publications Warehouse

    Lockner, D.A.

    1998-01-01

    A semiempirical constitutive law is presented for the brittle deformation of intact Westerly granite. The law can be extended to larger displacements, dominated by localized deformation, by including a displacement-weakening break-down region terminating in a frictional sliding regime often described by a rate- and state-dependent constitutive law. The intact deformation law, based on an Arrhenius type rate equation, relates inelastic strain rate to confining pressure Pc, differential stress ????, inelastic strain ??i, and temperature T. The basic form of the law for deformation prior to fault nucleation is In ????i = c - (E*/RT) + (????/a??o)sin-??(???? i/2??o) where ??o and ??o are normalization constants (dependent on confining pressure), a is rate sensitivity of stress, and ?? is a shape parameter. At room temperature, eight experimentally determined coefficients are needed to fully describe the stress-strain-strain rate response for Westerly granite from initial loading to failure. Temperature dependence requires apparent activation energy (E* ??? 90 kJ/mol) and one additional experimentally determined coefficient. The similarity between the prefailure constitutive law for intact rock and the rate- and state-dependent friction laws for frictional sliding on fracture surfaces suggests a close connection between these brittle phenomena.

  8. Rate dependent deformation of porous sandstone across the brittle-ductile transition

    NASA Astrophysics Data System (ADS)

    Jefferd, M.; Brantut, N.; Mitchell, T. M.; Meredith, P. G.

    2017-12-01

    Porous sandstones transition from dilatant, brittle deformation at low pressure, to compactant, ductile deformation at high pressure. Both deformation modes are driven by microcracking, and are expected to exhibit a time dependency due to chemical interactions between the pore fluid and the rock matrix. In the brittle regime, time-dependent failure and brittle creep are well documented. However, much less is understood in the ductile regime. We present results from a series of triaxial deformation experiments, performed in the brittle-ductile transition zone of fluid saturated Bleurswiller sandstone (initial porosity = 23%). Samples were deformed at 40 MPa effective pressure, to 4% axial strain, under either constant strain rate (10-5 s-1) or constant stress (creep) conditions. In addition to stress, axial strain and pore volume change, P wave velocities and acoustic emission were monitored throughout. During constant stress tests, the strain rate initially decreased with increasing strain, before reaching a minimum and accelerating to a constant level beyond 2% axial strain. When plotted against axial strain, the strain rate evolution under constant stress conditions, mirrors the stress evolution during the constant strain rate tests; where strain hardening occurs prior to peak stress, which is followed by strain softening and an eventual plateau. In all our tests, the minimum strain rate during creep occurs at the same inelastic strain as the peak stress during constant strain tests, and strongly decreases with decreasing applied stress. The microstructural state of the rock, as interpreted from similar volumetric strain curves, as well as the P-wave velocity evolution and AE production rate, appears to be solely a function of the total inelastic strain, and is independent of the length of time required to reach said strain. We tested the sensitivity of fluid chemistry on the time dependency, through a series of experiments performed under similar stress

  9. On the brittle-ductile behavior of iron meteorites - New experimental constraints

    NASA Technical Reports Server (NTRS)

    Matsui, T.; Schultz, P. H.

    1984-01-01

    Impact trials were performed at the NASA vertical gun range to study low-temperature brittle-ductile transitions in meteoritic, steel and iron targets. The trials were performed to enhance the data base underlying the concept of formation of planetesimals in collisional coagulation. Impact velocities of 1.6-5.5 km/sec were used, as were temperatures from 100-300 K. Spallation was observed in the tests with meteorite samples, even at room temperature, and brittleness was enhanced at temperature below 200 C. Net mass losses were induced at the higher impact velocities. It is suggested that iron meteorite agglomerations could form in the inner solar region during nebular condensation, but would not form in farther-out regions such as the asteroid belt. The protoplanets could have an iron core, with metallicity decreasing with radius from the core, which may have happened with the earth.

  10. Preventing and Treating Brittle Bones and Osteoporosis | NIH MedlinePlus the Magazine

    MedlinePlus

    ... Javascript on. Feature: Osteoporosis Preventing and Treating Brittle Bones and Osteoporosis Past Issues / Winter 2011 Table of ... at high risk due to low bone mass. Bone and Bone Loss Bone is living, growing tissue. ...

  11. Novel Methods in Terminal Ballistics and Mechanochemistry of Damage 2. Phenomenological Mechanochemistry of Damage in Solid Brittle Dielectrics

    DTIC Science & Technology

    2015-09-01

    Phenomenological Mechanochemistry of Damage in Solid Brittle Dielectrics by MA Grinfeld Approved for public release...Army Research Laboratory Novel Methods in Terminal Ballistics and Mechanochemistry of Damage 2. Phenomenological Mechanochemistry of Damage...2. Phenomenological Mechanochemistry of Damage in Solid Brittle Dielectrics 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER

  12. Role of Brittle Behaviour of Soft Calcarenites Under Low Confinement: Laboratory Observations and Numerical Investigation

    NASA Astrophysics Data System (ADS)

    Lollino, Piernicola; Andriani, Gioacchino Francesco

    2017-07-01

    The strength decay that occurs in the post-peak stage, under low confinement stress, represents a key factor of the stress-strain behaviour of rocks. However, for soft rocks this issue is generally underestimated or even neglected in the solution of boundary value problems, as for example those concerning the stability of underground cavities or rocky cliffs. In these cases, the constitutive models frequently used in limit equilibrium analyses or more sophisticated numerical calculations are, respectively, rigid-plastic or elastic-perfectly plastic. In particular, most of commercial continuum-based numerical codes propose a variety of constitutive models, including elasticity, elasto-plasticity, strain-softening and elasto-viscoplasticity, which are not exhaustive in simulating the progressive failure mechanisms affecting brittle rock materials, these being characterized by material detachment and crack opening and propagation. As a consequence, a numerical coupling with mechanical joint propagation is needed to cope with fracture mechanics. Therefore, continuum-based applications that treat the simulation of the failure processes of intact rock masses at low stress levels may need the adoption of numerical techniques capable of implementing fracture mechanics and rock brittleness concepts, as it is shown in this paper. This work is aimed at highlighting, for some applications of rock mechanics, the essential role of post-peak brittleness of soft rocks by means of the application of a hybrid finite-discrete element method. This method allows for a proper simulation of the brittle rock behaviour and the related mechanism of fracture propagation. In particular, the paper presents two ideal problems, represented by a shallow underground cave and a vertical cliff, for which the evolution of the stability conditions is investigated by comparing the solutions obtained implementing different brittle material responses with those resulting from the assumption of perfectly

  13. Infusing Software Assurance Research Techniques into Use

    NASA Technical Reports Server (NTRS)

    Pressburger, Thomas; DiVito, Ben; Feather, Martin S.; Hinchey, Michael; Markosian, Lawrence; Trevino, Luis C.

    2006-01-01

    Research in the software engineering community continues to lead to new development techniques that encompass processes, methods and tools. However, a number of obstacles impede their infusion into software development practices. These are the recurring obstacles common to many forms of research. Practitioners cannot readily identify the emerging techniques that may benefit them, and cannot afford to risk time and effort evaluating and trying one out while there remains uncertainty about whether it will work for them. Researchers cannot readily identify the practitioners whose problems would be amenable to their techniques, and, lacking feedback from practical applications, are hard-pressed to gauge the where and in what ways to evolve their techniques to make them more likely to be successful. This paper describes an ongoing effort conducted by a software engineering research infusion team established by NASA s Software Engineering Initiative to overcome these obstacles. .

  14. The ASSIST: Bringing Information and Software Together for Scientists

    NASA Technical Reports Server (NTRS)

    Mandel, Eric

    1997-01-01

    The ASSIST was developed as a step toward overcoming the problems faced by researchers when trying to utilize complex and often conflicting astronomical data analysis systems. It implements a uniform graphical interface to analysis systems, documentation, data, and organizational memory. It is layered on top of the Answer Garden Substrate (AGS), a system specially designed to facilitate the collection and dissemination of organizational memory. Under the AISRP program, we further developed the ASSIST to make it even easier for researchers to overcome the difficulties of accessing software and information in a complex computer environment.

  15. Study on the cutting mechanism and the brittle ductile transition model of isotropic pyrolyric graphite

    NASA Astrophysics Data System (ADS)

    Wang, Minghai; Wang, Hujun; Liu, Zhonghai

    2011-05-01

    Isotropic pyrolyric graphite (IPG) is a new kind of brittle material, it can be used for sealing the aero-engine turbine shaft and the ethylene high-temperature equipment. It not only has the general advantages of ordinal carbonaceous materials such as high temperature resistance, lubrication and abrasion resistance, but also has the advantages of impermeability and machinability that carbon/carbon composite doesn't have. Therefore, it has broad prospects for development. Mechanism of brittle-ductile transition of IPG is the foundation of precision cutting while the plastic deformation of IPG is the essential and the most important mechanical behavior of precision cutting. Using the theory of strain gradient, the mechanism of this material removal during the precision cutting is analyzed. The critical cutting thickness of IPG is calculated for the first time. Furthermore, the cutting process parameters such as cutting depth, feed rate which corresponding to the scale of brittle-ductile transition deformation of IPG are calculated. In the end, based on the theory of micromechanics, the deformation behaviors of IPG such as brittle fracture, plastic deformation and mutual transformation process are all simulated under the Sih.G.C fracture criterion. The condition of the simulation is that the material under the pressure-shear loading conditions .The result shows that the best angle during the IPG precision cutting is -30°. The theoretical analysis and the simulation result are validated by precision cutting experiments.

  16. A Micromechanics-Based Elastoplastic Damage Model for Rocks with a Brittle-Ductile Transition in Mechanical Response

    NASA Astrophysics Data System (ADS)

    Hu, Kun; Zhu, Qi-zhi; Chen, Liang; Shao, Jian-fu; Liu, Jian

    2018-06-01

    As confining pressure increases, crystalline rocks of moderate porosity usually undergo a transition in failure mode from localized brittle fracture to diffused damage and ductile failure. This transition has been widely reported experimentally for several decades; however, satisfactory modeling is still lacking. The present paper aims at modeling the brittle-ductile transition process of rocks under conventional triaxial compression. Based on quantitative analyses of experimental results, it is found that there is a quite satisfactory linearity between the axial inelastic strain at failure and the confining pressure prescribed. A micromechanics-based frictional damage model is then formulated using an associated plastic flow rule and a strain energy release rate-based damage criterion. The analytical solution to the strong plasticity-damage coupling problem is provided and applied to simulate the nonlinear mechanical behaviors of Tennessee marble, Indiana limestone and Jinping marble, each presenting a brittle-ductile transition in stress-strain curves.

  17. Overcoming the Problem of Brittleness with the Metacognitive Loop

    DTIC Science & Technology

    2008-11-30

    and the IFR ontologies. As a consequence, the investigators are now positioned (starting in 2009, with a new award) to begin to build a general...purpose MCL module that, when "attached* to a given host program H and an initial set of IFR ontologies, can adapt to the domain that H lives in (and...entry records pcop- erties of the word including multiple forms, (multiple) spelling. pan of speech, argument structure (for verbs), ( (b) ALFRED

  18. Superior room-temperature ductility of typically brittle quasicrystals at small sizes

    PubMed Central

    Zou, Yu; Kuczera, Pawel; Sologubenko, Alla; Sumigawa, Takashi; Kitamura, Takayuki; Steurer, Walter; Spolenak, Ralph

    2016-01-01

    The discovery of quasicrystals three decades ago unveiled a class of matter that exhibits long-range order but lacks translational periodicity. Owing to their unique structures, quasicrystals possess many unusual properties. However, a well-known bottleneck that impedes their widespread application is their intrinsic brittleness: plastic deformation has been found to only be possible at high temperatures or under hydrostatic pressures, and their deformation mechanism at low temperatures is still unclear. Here, we report that typically brittle quasicrystals can exhibit remarkable ductility of over 50% strains and high strengths of ∼4.5 GPa at room temperature and sub-micrometer scales. In contrast to the generally accepted dominant deformation mechanism in quasicrystals—dislocation climb, our observation suggests that dislocation glide may govern plasticity under high-stress and low-temperature conditions. The ability to plastically deform quasicrystals at room temperature should lead to an improved understanding of their deformation mechanism and application in small-scale devices. PMID:27515779

  19. Earthquake rupture below the brittle-ductile transition in continental lithospheric mantle.

    PubMed

    Prieto, Germán A; Froment, Bérénice; Yu, Chunquan; Poli, Piero; Abercrombie, Rachel

    2017-03-01

    Earthquakes deep in the continental lithosphere are rare and hard to interpret in our current understanding of temperature control on brittle failure. The recent lithospheric mantle earthquake with a moment magnitude of 4.8 at a depth of ~75 km in the Wyoming Craton was exceptionally well recorded and thus enabled us to probe the cause of these unusual earthquakes. On the basis of complete earthquake energy balance estimates using broadband waveforms and temperature estimates using surface heat flow and shear wave velocities, we argue that this earthquake occurred in response to ductile deformation at temperatures above 750°C. The high stress drop, low rupture velocity, and low radiation efficiency are all consistent with a dissipative mechanism. Our results imply that earthquake nucleation in the lithospheric mantle is not exclusively limited to the brittle regime; weakening mechanisms in the ductile regime can allow earthquakes to initiate and propagate. This finding has significant implications for understanding deep earthquake rupture mechanics and rheology of the continental lithosphere.

  20. Apparatus for measuring internal friction Q factors in brittle materials. [applied to lunar samples

    NASA Technical Reports Server (NTRS)

    Tittmann, B. R.; Curnow, J. M.

    1976-01-01

    A flexural analog of the torsion pendulum for measuring the Young's modulus and the internal friction Q factor of brittle materials has been developed for Q greater than 10 to the 3rd measurements at a zero static stress and at 10 to the -7th strains of brittle materials in the Hz frequency range. The present design was motivated by the desire to measure Q in fragile lunar return samples at zero static stress to shed light on the anomalously low attenuation of seismic waves on the moon. The use of the apparatus is demonstrated with data on fused silica and on a terrestrial analog of lunar basalt.

  1. Energy approach to brittle fracture in strain-gradient modelling.

    PubMed

    Placidi, Luca; Barchiesi, Emilio

    2018-02-01

    In this paper, we exploit some results in the theory of irreversible phenomena to address the study of quasi-static brittle fracture propagation in a two-dimensional isotropic continuum. The elastic strain energy density of the body has been assumed to be geometrically nonlinear and to depend on the strain gradient. Such generalized continua often arise in the description of microstructured media. These materials possess an intrinsic length scale, which determines the size of internal boundary layers. In particular, the non-locality conferred by this internal length scale avoids the concentration of deformations, which is usually observed when dealing with local models and which leads to mesh dependency. A scalar Lagrangian damage field, ranging from zero to one, is introduced to describe the internal state of structural degradation of the material. Standard Lamé and second-gradient elastic coefficients are all assumed to decrease as damage increases and to be locally zero if the value attained by damage is one. This last situation is associated with crack formation and/or propagation. Numerical solutions of the model are provided in the case of an obliquely notched rectangular specimen subjected to monotonous tensile and shear loading tests, and brittle fracture propagation is discussed.

  2. Development and application of new quality model for software projects.

    PubMed

    Karnavel, K; Dillibabu, R

    2014-01-01

    The IT industry tries to employ a number of models to identify the defects in the construction of software projects. In this paper, we present COQUALMO and its limitations and aim to increase the quality without increasing the cost and time. The computation time, cost, and effort to predict the residual defects are very high; this was overcome by developing an appropriate new quality model named the software testing defect corrective model (STDCM). The STDCM was used to estimate the number of remaining residual defects in the software product; a few assumptions and the detailed steps of the STDCM are highlighted. The application of the STDCM is explored in software projects. The implementation of the model is validated using statistical inference, which shows there is a significant improvement in the quality of the software projects.

  3. Breaking new ground in the mind: an initial study of mental brittle transformation and mental rigid rotation in science experts.

    PubMed

    Resnick, Ilyse; Shipley, Thomas F

    2013-05-01

    The current study examines the spatial skills employed in different spatial reasoning tasks, by asking how science experts who are practiced in different types of visualizations perform on different spatial tasks. Specifically, the current study examines the varieties of mental transformations. We hypothesize that there may be two broad classes of mental transformations: rigid body mental transformations and non-rigid mental transformations. We focus on the disciplines of geology and organic chemistry because different types of transformations are central to the two disciplines: While geologists and organic chemists may both confront rotation in the practice of their profession, only geologists confront brittle transformations. A new instrument was developed to measure mental brittle transformation (visualizing breaking). Geologists and organic chemists performed similarly on a measure of mental rotation, while geologists outperformed organic chemists on the mental brittle transformation test. The differential pattern of skill on the two tests for the two groups of experts suggests that mental brittle transformation and mental rotation are different spatial skills. The roles of domain general cognitive resources (attentional control, spatial working memory, and perceptual filling in) and strategy in completing mental brittle transformation are discussed. The current study illustrates how ecological and interdisciplinary approaches complement traditional cognitive science to offer a comprehensive approach to understanding the nature of spatial thinking.

  4. The Infeasibility of Quantifying the Reliability of Life-Critical Real-Time Software

    NASA Technical Reports Server (NTRS)

    Butler, Ricky W.; Finelli, George B.

    1991-01-01

    This paper affirms that the quantification of life-critical software reliability is infeasible using statistical methods whether applied to standard software or fault-tolerant software. The classical methods of estimating reliability are shown to lead to exhorbitant amounts of testing when applied to life-critical software. Reliability growth models are examined and also shown to be incapable of overcoming the need for excessive amounts of testing. The key assumption of software fault tolerance separately programmed versions fail independently is shown to be problematic. This assumption cannot be justified by experimentation in the ultrareliability region and subjective arguments in its favor are not sufficiently strong to justify it as an axiom. Also, the implications of the recent multiversion software experiments support this affirmation.

  5. Brittle and ductile adjustable cement derived from calcium phosphate cement/polyacrylic acid composites.

    PubMed

    Chen, Wen-Cheng; Ju, Chien-Ping; Wang, Jen-Chyan; Hung, Chun-Cheng; Chern Lin, Jiin-Huey

    2008-12-01

    Bone filler has been used over the years in dental and biomedical applications. The present work is to characterize a non-dispersive, fast setting, modulus adjustable, high bioresorbable composite bone cement derived from calcium phosphate-based cement combined with polymer and binding agents. This cement, we hope, will not swell in simulated body fluid and keep the osteogenetic properties of the dry bone and avoid its disadvantages of being brittle. We developed a calcium phosphate cement (CPC) of tetracalcium phosphate/dicalcium phosphate anhydrous (TTCP/DCPA)-polyacrylic acid with tartaric acid, calcium fluoride additives and phosphate hardening solution. The results show that while composite, the hard-brittle properties of 25wt% polyacrylic acid are proportional to CPC and mixing with additives is the same as those of the CPC without polyacrylic acid added. With an increase of polyacrylic acid/CPC ratio, the 67wt% samples revealed ductile-tough properties and 100wt% samples kept ductile or elastic properties after 24h of immersion. The modulus range of this development was from 200 to 2600MPa after getting immersed in simulated body fluid for 24h. The TTCP/DCPA-polyacrylic acid based CPC demonstrates adjustable brittle/ductile strength during setting and after immersion, and the final reaction products consist of high bioresorbable monetite/brushite/calcium fluoride composite with polyacrylic acid.

  6. DOCLIB: a software library for document processing

    NASA Astrophysics Data System (ADS)

    Jaeger, Stefan; Zhu, Guangyu; Doermann, David; Chen, Kevin; Sampat, Summit

    2006-01-01

    Most researchers would agree that research in the field of document processing can benefit tremendously from a common software library through which institutions are able to develop and share research-related software and applications across academic, business, and government domains. However, despite several attempts in the past, the research community still lacks a widely-accepted standard software library for document processing. This paper describes a new library called DOCLIB, which tries to overcome the drawbacks of earlier approaches. Many of DOCLIB's features are unique either in themselves or in their combination with others, e.g. the factory concept for support of different image types, the juxtaposition of image data and metadata, or the add-on mechanism. We cherish the hope that DOCLIB serves the needs of researchers better than previous approaches and will readily be accepted by a larger group of scientists.

  7. Evaluation of strength and failure of brittle rock containing initial cracks under lithospheric conditions

    NASA Astrophysics Data System (ADS)

    Li, Xiaozhao; Qi, Chengzhi; Shao, Zhushan; Ma, Chao

    2018-02-01

    Natural brittle rock contains numerous randomly distributed microcracks. Crack initiation, growth, and coalescence play a predominant role in evaluation for the strength and failure of brittle rocks. A new analytical method is proposed to predict the strength and failure of brittle rocks containing initial microcracks. The formulation of this method is based on an improved wing crack model and a suggested micro-macro relation. In this improved wing crack model, the parameter of crack angle is especially introduced as a variable, and the analytical stress-crack relation considering crack angle effect is obtained. Coupling the proposed stress-crack relation and the suggested micro-macro relation describing the relation between crack growth and axial strain, the stress-strain constitutive relation is obtained to predict the rock strength and failure. Considering different initial microcrack sizes, friction coefficients and confining pressures, effects of crack angle on tensile wedge force acting on initial crack interface are studied, and effects of crack angle on stress-strain constitutive relation of rocks are also analyzed. The strength and crack initiation stress under different crack angles are discussed, and the value of most disadvantaged angle triggering crack initiation and rock failure is founded. The analytical results are similar to the published study results. Rationality of this proposed analytical method is verified.

  8. Impact Damage Thresholds in Brittle Materials Impacted by Water Drops.

    DTIC Science & Technology

    1979-03-01

    hardness AS$TNAC T (C 5M.. cc roc .. aId. It ,. m.p .id td ..tIl~- S~. block cad ..) The damage threshold for brittle materials impacted by water drops...center, vls-a-vls their(continued) ~~~ DO I JA N71 1Q3 EDITION OP 1 NOV IS iS OHOLETE UNCLASSIFIED SECURITY CLASSIFICATION OP ThiS RAGS (a. ONs

  9. Development and Application of New Quality Model for Software Projects

    PubMed Central

    Karnavel, K.; Dillibabu, R.

    2014-01-01

    The IT industry tries to employ a number of models to identify the defects in the construction of software projects. In this paper, we present COQUALMO and its limitations and aim to increase the quality without increasing the cost and time. The computation time, cost, and effort to predict the residual defects are very high; this was overcome by developing an appropriate new quality model named the software testing defect corrective model (STDCM). The STDCM was used to estimate the number of remaining residual defects in the software product; a few assumptions and the detailed steps of the STDCM are highlighted. The application of the STDCM is explored in software projects. The implementation of the model is validated using statistical inference, which shows there is a significant improvement in the quality of the software projects. PMID:25478594

  10. The semi-brittle to ductile transition in peridotite on oceanic faults: mechanisms and P-T condition

    NASA Astrophysics Data System (ADS)

    Prigent, C.; Warren, J. M.; Kohli, A. H.; Teyssier, C. P.

    2017-12-01

    Experimental and geological-petrological studies suggest that the transition from brittle faulting to ductile flow of olivine, i.e. from seismic to aseismic behavior of mantle rocks (peridotites), occurs close to 600°C. However, recent seismological studies on oceanic transform faults (TFs) and ridges have documented earthquakes to temperatures (T) up to 700-800°C. In this study, we carried out a petrological, microstructural and geochemical analysis of natural samples of peridotites dredged at 3 different oceanic TFs of the Southwest Indian Ridge: Shaka, Prince Edward and Atlantis II. We selected samples displaying variable amounts of ductile deformation (from porphyroclastic tectonites to ultramylonites) prior to serpentinization in order to characterize their relatively high-T mechanical behavior. We find that the most deformed samples record cycles of ductile and brittle deformation. Peridotite ductile flow is characterized by drastic grain size reduction and the development of (ultra)mylonitic shear zones. In these zones, a switch in olivine deformation mechanism from dislocation creep to grain-size sensitive creep is associated with dissolution/precipitation processes. Brittle deformation of these samples is evidenced by the presence of (at least centimetric) transgranular and intragranular fractures that fragment coarser grained minerals. Both kinds of fractures are filled with the same phase assemblage as in the ultramylonitic bands: olivine + amphibole ± orthopyroxene ± Al-phase (plagioclase and/or spinel) ± sulfides. The presence of amphibole indicates that this semi-brittle deformation was assisted by hydrous fluids and its composition (e.g. high concentration of chlorine) suggests that the fluids have most likely a hydrothermal origin. We interpret these fractures to have formed under fluid-assisted conditions, recording paleo-seismic activity that alternated with periods of relatively slow interseismic ductile flow. The presence of Mg

  11. Cohesive stress heterogeneities and the transition from intrinsic ductility to brittleness

    NASA Astrophysics Data System (ADS)

    Tanguy, D.

    2017-11-01

    The influence of nanoscale cavities on the fracture of the Σ 33 {554 }[110 ] symmetrical tilt grain boundary is studied by atomistic simulations. The crack crystallography is chosen such that dislocation emission is easy. A transition from a ductile behavior of the tip to a brittle one is obtained for a dense (coverage beyond 15% and intercavity spacing smaller than 4 nm) distribution of small cavities (sizes in-between 1 and 2 nm). The results are in good agreement with recent experiments from the literature. Even at the highest coverage, the character of the crack is highly sensitive to the initial position of the tip and a mixture of ductile and brittle responses is found. This complexity is beyond the usual criterion based on the drop of the work of separation with the amount of damage in the structure. It is shown that a heterogeneous cohesive zone model, with parameters extracted from the simulations and enriched with a criterion for plasticity, can explain the simulations and reproduce the transition. Additional simulations show that outside this range of small sizes and dense packing, which gives essentially a two-dimensional response (either crack opening or infinite straight dislocation emission), dislocation half-loops appear for intercavity spacing starting at about 4 nm. They constitute, together with regions of low coverage/small cavities, efficient obstacles to brittle cracking. These results could be guidelines to designing interfaces more resistant to solute embrittlement, in general. The cohesive zone model is generic. Furthermore, the {554} single crystal was used to determine to which extent the results depend on the details of the core structure versus the cavity distribution. These elements show that the conclusions reached have a generic character.

  12. Brittle deformation and slope failure at the North Menan Butte tuff cone, Eastern Snake River Plain, Idaho

    USGS Publications Warehouse

    Okubo, Chris H.

    2014-01-01

    The manifestation of brittle deformation within inactive slumps along the North Menan Butte, a basaltic tuff cone in the Eastern Snake River Plain, is investigated through field and laboratory studies. Microstructural observations indicate that brittle strain is localized along deformation bands, a class of structural discontinuity that is predominant within moderate to high-porosity, clastic sedimentary rocks. Various subtypes of deformation bands are recognized in the study area based on the sense of strain they accommodate. These include dilation bands (no shear displacement), dilational shear bands, compactional shear bands and simple shear bands (no volume change). Measurements of the host rock permeability between the deformation bands indicate that the amount of brittle strain distributed throughout this part of the rock is negligible, and thus deformation bands are the primary means by which brittle strain is manifest within this tuff. Structural discontinuities that are similar in appearance to deformation bands are observed in other basaltic tuffs. Therefore deformation bands may represent a common structural feature of basaltic tuffs that have been widely misclassified as fractures. Slumping and collapse along the flanks of active volcanoes strongly influence their eruptive behavior and structural evolution. Therefore characterizing the process of deformation band and fault growth within basaltic tuff is key to achieving a more complete understanding of the evolution of basaltic volcanoes and their associated hazards.

  13. Earthquake rupture below the brittle-ductile transition in continental lithospheric mantle

    PubMed Central

    Prieto, Germán A.; Froment, Bérénice; Yu, Chunquan; Poli, Piero; Abercrombie, Rachel

    2017-01-01

    Earthquakes deep in the continental lithosphere are rare and hard to interpret in our current understanding of temperature control on brittle failure. The recent lithospheric mantle earthquake with a moment magnitude of 4.8 at a depth of ~75 km in the Wyoming Craton was exceptionally well recorded and thus enabled us to probe the cause of these unusual earthquakes. On the basis of complete earthquake energy balance estimates using broadband waveforms and temperature estimates using surface heat flow and shear wave velocities, we argue that this earthquake occurred in response to ductile deformation at temperatures above 750°C. The high stress drop, low rupture velocity, and low radiation efficiency are all consistent with a dissipative mechanism. Our results imply that earthquake nucleation in the lithospheric mantle is not exclusively limited to the brittle regime; weakening mechanisms in the ductile regime can allow earthquakes to initiate and propagate. This finding has significant implications for understanding deep earthquake rupture mechanics and rheology of the continental lithosphere. PMID:28345055

  14. Studies in Software Cost Model Behavior: Do We Really Understand Cost Model Performance?

    NASA Technical Reports Server (NTRS)

    Lum, Karen; Hihn, Jairus; Menzies, Tim

    2006-01-01

    While there exists extensive literature on software cost estimation techniques, industry practice continues to rely upon standard regression-based algorithms. These software effort models are typically calibrated or tuned to local conditions using local data. This paper cautions that current approaches to model calibration often produce sub-optimal models because of the large variance problem inherent in cost data and by including far more effort multipliers than the data supports. Building optimal models requires that a wider range of models be considered while correctly calibrating these models requires rejection rules that prune variables and records and use multiple criteria for evaluating model performance. The main contribution of this paper is to document a standard method that integrates formal model identification, estimation, and validation. It also documents what we call the large variance problem that is a leading cause of cost model brittleness or instability.

  15. Self-repair of cracks in brittle material systems

    NASA Astrophysics Data System (ADS)

    Dry, Carolyn M.

    2016-04-01

    One of the most effective uses for self repair is in material systems that crack because the cracks can allow the repair chemical to flow into the crack damage sites in all three dimensions. In order for the repair chemical to stay in the damage site and flow along to all the crack and repair there must be enough chemical to fill the entire crack. The repair chemical must be designed appropriately for the particular crack size and total volume of cracks. In each of the three examples of self repair in crackable brittle systems, the viscosity and chemical makeup and volume of the repair chemicals used is different for each system. Further the chemical delivery system has to be designed for each application also. Test results from self repair of three brittle systems are discussed. In "Self Repair of Concrete Bridges and Infrastructure" two chemicals were used due to different placements in bridges to repair different types of cracks- surface shrinkage and shear cracks, In "Airplane Wings and Fuselage, in Graphite" the composite has very different properties than the concrete bridges. In the graphite for airplane components the chemical also had to survive the high processing temperatures. In this composite the cracks were so definite and deep and thin that the repair chemical could flow easily and repair in all layers of the composite. In "Ceramic/Composite Demonstrating Self Repair" the self repair system not only repaired the broken ceramic but also rebounded the composite to the ceramic layer

  16. Combined structural analysis and dating of authigenic/synkinematic illite: A step towards unravelling brittle faulting processes in time and space

    NASA Astrophysics Data System (ADS)

    Viola, Giulio

    2017-04-01

    Faulting accommodates momentous deformation and its style reflects the complex interplay of often transient processes such as friction, fluid flow and rheological changes within generally dilatant systems. Brittle faults are thus unique archives of the stress state and the physical and chemical conditions at the time of both initial strain localization and subsequent slip(s) during structural reactivation. Opening those archives, however, may be challenging due to the commonly convoluted (if not even chaotic) nature of brittle fault architectures and fault rocks. This is because, once formed, faults are extremely sensitive to variations in stress field and environmental conditions and are prone to readily slip in a variety of conditions, also in regions affected by only weak, far-field stresses. The detailed, multi-scalar structural analysis of faults and of fault rocks has to be the starting point for any study aiming at reconstructing the complex framework of brittle deformation. However, considering that present-day exposures of faults only represent the end result of the faults' often protracted and heterogeneous histories, the obtained structural and mechanical results have to be integrated over the life span of the studied fault system. Dating of synkinematic illite/muscovite to constrain the time-integrated evolution of faults is therefore the natural addition to detailed structural studies. By means of selected examples it will be demonstrated how careful structural analysis integrated with illite characterization and K-Ar dating allows the high-resolution reconstruction of brittle deformation histories and, in turn, multiple constraints to be placed on strain localization, deformation mechanisms, fluid flow, mineral alteration and authigenesis within actively deforming brittle fault rocks. Complex and long brittle histories can thus be reconstructed and untangled in any tectonic setting.

  17. A model for multiple-drop-impact erosion of brittle solids

    NASA Technical Reports Server (NTRS)

    Engel, O. G.

    1971-01-01

    A statistical model for the multiple-drop-impact erosion of brittle solids was developed. An equation for calculating the rate of erosion is given. The development is not complete since two quantities that are needed to calculate the rate of erosion with use of the equation must be assessed from experimental data. A partial test of the equation shows that it gives results that are in good agreement with experimental observation.

  18. A Weibull characterization for tensile fracture of multicomponent brittle fibers

    NASA Technical Reports Server (NTRS)

    Barrows, R. G.

    1977-01-01

    A statistical characterization for multicomponent brittle fibers in presented. The method, which is an extension of usual Weibull distribution procedures, statistically considers the components making up a fiber (e.g., substrate, sheath, and surface) as separate entities and taken together as in a fiber. Tensile data for silicon carbide fiber and for an experimental carbon-boron alloy fiber are evaluated in terms of the proposed multicomponent Weibull characterization.

  19. On the brittle nature of rare earth pnictides

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shriya, S.; Sapkale, R.; Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com, E-mail: sapkale.raju@rediffmail.com

    The high-pressure structural phase transition and pressure as well temperature induced elastic properties in ReY; (Re = La, Sc, Pr; Y = N, P, As, Sb, Bi) pnictides have been performed using effective interionic interaction potential with emphasis on charge transfer interactions and covalent contribution. Estimated values of phase transition pressure and the volume discontinuity in pressure-volume phase diagram indicate the structural phase transition from NaCl to CsCl structure. From the investigations of elastic constants the pressure (temperature) dependent volume collapse/expansion, second order Cauchy discrepancy, anisotropy, hardness and brittle/ductile nature of rare earth pnictides are computed.

  20. Professional Ethics of Software Engineers: An Ethical Framework.

    PubMed

    Lurie, Yotam; Mark, Shlomo

    2016-04-01

    The purpose of this article is to propose an ethical framework for software engineers that connects software developers' ethical responsibilities directly to their professional standards. The implementation of such an ethical framework can overcome the traditional dichotomy between professional skills and ethical skills, which plagues the engineering professions, by proposing an approach to the fundamental tasks of the practitioner, i.e., software development, in which the professional standards are intrinsically connected to the ethical responsibilities. In so doing, the ethical framework improves the practitioner's professionalism and ethics. We call this approach Ethical-Driven Software Development (EDSD), as an approach to software development. EDSD manifests the advantages of an ethical framework as an alternative to the all too familiar approach in professional ethics that advocates "stand-alone codes of ethics". We believe that one outcome of this synergy between professional and ethical skills is simply better engineers. Moreover, since there are often different software solutions, which the engineer can provide to an issue at stake, the ethical framework provides a guiding principle, within the process of software development, that helps the engineer evaluate the advantages and disadvantages of different software solutions. It does not and cannot affect the end-product in and of-itself. However, it can and should, make the software engineer more conscious and aware of the ethical ramifications of certain engineering decisions within the process.

  1. Children with Brittle Bones: An Examination of Their Educational Needs and Progress.

    ERIC Educational Resources Information Center

    Alston, Jean

    1983-01-01

    A study of the educational achievements of 40 children (5-16 years old) with osteogenesis imperfecta, brittle bone disease, revealed no differences between Ss and control Ss without the condition in terms of nonverbal intelligence. Differences were found, however, in writing speed. Inteviews with children, teachers, and parents revealed…

  2. Cyclic Ductile-Brittle Deformation during Temperature Decrease in Quartz-Rich Mylonites: Insights from the Calamita Schists (Elba Island, Italy)

    NASA Astrophysics Data System (ADS)

    Papeschi, S.; Menegon, L. M.; Musumeci, G.

    2017-12-01

    The Calamita Schists are a metamorphic complex that experienced transient (< 1 Ma) upper Miocene HT/LP metamorphism related to the emplacement of the Porto Azzurro pluton at P<0.2 GPa. HT/LP metamorphism was coeval with regional scale contractional tectonics leading to the development of meter to decameter ductile east-verging high-strain domains marked by mylonitic fabric overprinted by non-Andersonian brittle faults. In order to investigate the switch in deformation mechanism during temperature decrease at constant pressure (P<0.2 GPa), a sample of mylonitic quartzite with S-C' fabric was examined by Electron Backscatter Diffraction (EBSD), optical microscopy and Scanning Electron Microscope (SEM). Mylonitic fabric is marked by synkinematic biotite + cordierite + andalusite + K-feldspar assemblage, which is progressively replaced by retrograde white mica + chlorite. Quartz microfabric is defined by coarse-grained (100-900 µm) quartz porphyroclasts wrapped by ribbons of dynamically recrystallized finer grains ( 50 µm) showing a strong CPO. This fabric is cross cut by conjugate and synthetic C'-shear bands localized in porphyroclasts and marked by recrystallized fine grains (5-50 µm). EBSD data indicate that prism was the dominant slip system during crystal plastic deformation and dynamic recrystallization in the polycrystalline ribbons. Subsequently, brittle deformation localized along intracrystalline bands (both in conjugate sets and parallel to C' shear bands) within quartz porphyroclasts. The bands evolved in localized cataclastic micro-shear zones and in shear fractures, which localized fluid infiltration and healing by solution precipitation. The quartz new grains filling the bands are preferentially oriented with their c-axis parallel to the shear band boundary. This work highlights that deformation in the Calamita Schists switched over time from high-temperature dynamic recrystallization, accommodated by prism slip to low grade brittle-ductile processes

  3. A brittle-ductile high- and low-angle fault related to the Kea extensional detachment (W Cyclades., Greece)

    NASA Astrophysics Data System (ADS)

    Rockenschaub, M.; Grasemann, B.; Iglseder, C.; Rice, A. H. N.; Schneider, D.; Zamolyi, A.

    2010-05-01

    Roll-back of the African Plate within the Eurasian-African collision zone since the Oligocene/Miocene led to extension in the Cyclades along low-angle normal fault zones and exhumation of rocks from near the brittle-ductile transition zone. On the island of Kea (W Cyclades), which represents such a crustal scale low-angle fault zone with top-to-SSW kinematics, remote sensing analysis of brittle fault lineaments in the Pissis area (W Kea) demonstrates two dominant strike directions: ca. NE-SW and NW-SE. From the north of Pisses southwards, the angle between the two main fault directions changes gradually from a rhombohedral geometry (ca. 50°/130° angle between faults, with the acute angle facing westwards) to an orthogonal geometry. The aim of this study is the development of this fault system. We investigate, if this fault system is related to the Miocene extension or if it is related to a later overprinting event (e.g. the opening of the Corinth) Field observations revealed that the investigated lineaments are high-angle (50-90° dip) brittle/ductile conjugate, faults. Due to the lack of marker layers offsets could only rarely be estimated. Locally centimetre thick marble layers in the greenschists suggest a displacement gradient along the faults with a maximum offset of less than 60 cm. Large displacement gradients are associated with a pronounced ductile fault drag in the host rocks. In some instances, high-angle normal faults were observed to link kinematically with low-angle, top-to-SSW brittle/ductile shear bands. Both the high- and the low-angle faults have a component of ductile shear, which is overprinted by brittle deformation mechanisms. In thin-section, polyphase mode-2 cracks are filled mainly with calcite and quartz (ultra)cataclasites, sometimes followed by further opening with fluid-related iron-rich carbonate (ankeritic) precipitation. CL analysis reveals several generations of cements, indicating multiple phases of cataclastic deformation and

  4. Maize Brittle stalk2 encodes a COBRA-like protein expressed in early organ development but required for tissue flexibility at maturity.

    PubMed

    Sindhu, Anoop; Langewisch, Tiffany; Olek, Anna; Multani, Dilbag S; McCann, Maureen C; Vermerris, Wilfred; Carpita, Nicholas C; Johal, Gurmukh

    2007-12-01

    The maize (Zea mays) brittle stalk2 (bk2) is a recessive mutant, the aerial parts of which are easily broken. The bk2 phenotype is developmentally regulated and appears 4 weeks after planting, at about the fifth-leaf stage. Before this time, mutants are indistinguishable from wild-type siblings. Afterward, all organs of the bk2 mutants turn brittle, even the preexisting ones, and they remain brittle throughout the life of the plant. Leaf tension assays and bend tests of the internodes show that the brittle phenotype does not result from loss of tensile strength but from loss in flexibility that causes the tissues to snap instead of bend. The Bk2 gene was cloned by a combination of transposon tagging and a candidate gene approach and found to encode a COBRA-like protein similar to rice (Oryza sativa) BC1 and Arabidopsis (Arabidopsis thaliana) COBRA-LIKE4. The outer periphery of the stalk has fewer vascular bundles, and the sclerids underlying the epidermis possess thinner secondary walls. Relative cellulose content is not strictly correlated with the brittle phenotype. Cellulose content in mature zones of bk2 mature stems is lowered by 40% but is about the same as wild type in developing stems. Although relative cellulose content is lowered in leaves after the onset of the brittle phenotype, total wall mass as a proportion of dry mass is either unchanged or slightly increased, indicating a compensatory increase in noncellulosic carbohydrate mass. Fourier transform infrared spectra indicated an increase in phenolic ester content in the walls of bk2 leaves and stems. Total content of lignin is unaffected in bk2 juvenile leaves before or after appearance of the brittle phenotype, but bk2 mature and developing stems are markedly enriched in lignin compared to wild-type stems. Despite increased lignin in bk2 stems, loss of staining with phloroglucinol and ultraviolet autofluorescence is observed in vascular bundles and sclerid layers. Consistent with the infrared

  5. Enhancing User Customization through Novel Software Architecture for Utility Scale Solar Siting Software

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brant Peery; Sam Alessi; Randy Lee

    2014-06-01

    There is a need for a spatial decision support application that allows users to create customized metrics for comparing proposed locations of a new solar installation. This document discusses how PVMapper was designed to overcome the customization problem through the development of loosely coupled spatial and decision components in a JavaScript plugin architecture. This allows the user to easily add functionality and data to the system. The paper also explains how PVMapper provides the user with a dynamic and customizable decision tool that enables them to visually modify the formulas that are used in the decision algorithms that convert datamore » to comparable metrics. The technologies that make up the presentation and calculation software stack are outlined. This document also explains the architecture that allows the tool to grow through custom plugins created by the software users. Some discussion is given on the difficulties encountered while designing the system.« less

  6. Open-source meteor detection software for low-cost single-board computers

    NASA Astrophysics Data System (ADS)

    Vida, D.; Zubović, D.; Šegon, D.; Gural, P.; Cupec, R.

    2016-01-01

    This work aims to overcome the current price threshold of meteor stations which can sometimes deter meteor enthusiasts from owning one. In recent years small card-sized computers became widely available and are used for numerous applications. To utilize such computers for meteor work, software which can run on them is needed. In this paper we present a detailed description of newly-developed open-source software for fireball and meteor detection optimized for running on low-cost single board computers. Furthermore, an update on the development of automated open-source software which will handle video capture, fireball and meteor detection, astrometry and photometry is given.

  7. Mechanical Behavior of Low Porosity Carbonate Rock: From Brittle Creep to Ductile Creep.

    NASA Astrophysics Data System (ADS)

    Nicolas, A.; Fortin, J.; Gueguen, Y.

    2014-12-01

    Mechanical compaction and associated porosity reduction play an important role in the diagenesis of porous rocks. They may also affect reservoir rocks during hydrocarbon production, as the pore pressure field is modified. This inelastic compaction can lead to subsidence, cause casing failure, trigger earthquake, or change the fluid transport properties. In addition, inelastic deformation can be time - dependent. In particular, brittle creep phenomena have been deeply investigated since the 90s, especially in sandstones. However knowledge of carbonates behavior is still insufficient. In this study, we focus on the mechanical behavior of a 14.7% porosity white Tavel (France) carbonate rock (>98% calcite). The samples were deformed in a triaxial cell at effective confining pressures ranging from 0 MPa to 85 MPa at room temperature and 70°C. Experiments were carried under dry and water saturated conditions in order to explore the role played by the pore fluids. Two types of experiments have been carried out: (1) a first series in order to investigate the rupture envelopes, and (2) a second series with creep experiments. During the experiments, elastic wave velocities (P and S) were measured to infer crack density evolution. Permeability was also measured during creep experiments. Our results show two different mechanical behaviors: (1) brittle behavior is observed at low confining pressures, whereas (2) ductile behavior is observed at higher confining pressures. During creep experiments, these two behaviors have a different signature in term of elastic wave velocities and permeability changes, due to two different mechanisms: development of micro-cracks at low confining pressures and competition between cracks and microplasticity at high confining pressure. The attached figure is a summary of 20 triaxial experiments performed on Tavel limestone under different conditions. Stress states C',C* and C*' and brittle strength are shown in the P-Q space: (a) 20°C and dry

  8. Characterization and analysis of Porous, Brittle solid structures by X-ray micro computed tomography

    NASA Astrophysics Data System (ADS)

    Lin, C. L.; Videla, A. R.; Yu, Q.; Miller, J. D.

    2010-12-01

    The internal structure of porous, brittle solid structures, such as porous rock, foam metal and wallboard, is extremely complex. For example, in the case of wallboard, the air bubble size and the thickness/composition of the wall structure are spatial parameters that vary significantly and influence mechanical, thermal, and acoustical properties. In this regard, the complex geometry and the internal texture of material, such as wallboard, is characterized and analyzed in 3-D using cone beam x-ray micro computed tomography. Geometrical features of the porous brittle structure are quantitatively analyzed based on calibration of the x-ray linear attenuation coefficient, use of a 3-D watershed algorithm, and use of a 3-D skeletonization procedure. Several examples of the 3-D analysis for porous, wallboard structures are presented and the results discussed.

  9. Evidence for brittle deformation events at eclogite-facies P-T conditions (example of the Mt. Emilius klippe, Western Alps)

    NASA Astrophysics Data System (ADS)

    Hertgen, Solenn; Yamato, Philippe; Morales, Luiz F. G.; Angiboust, Samuel

    2017-06-01

    Eclogitic rocks are crucial for the understanding of tectonic processes as they provide key constraints on both the P-T-t evolutions and the deformation modes sustained by rocks in subduction zones. Here we focus on eclogitised and deformed mafic bodies that are exposed within granulites from the continental basement slice of the Mt. Emilius klippe (Western Alps, Italy). These eclogites exhibit highly deformed garnetite and clinopyroxenite layers. In some places, these deformed rocks (up to mylonitic grade) can be found as clasts within meter-thick brecciated fault rocks that formed close to the lawsonite-eclogite facies peak P-T conditions. Garnet-rich layers are dominated by brittle features, whereas deformation within clinopyroxene-rich layers is accommodated by both creep and fracturing. We present a petro-structural study of these eclogites, that allows to track the brittle deformation history associated with chemical evolution. Based on these data, we propose a new tectono-metamorphic model for these rocks, related to the alpine eclogitic stage. This model is consistent with the coexistence of both ductile and brittle features that developed at similar P-T conditions (i.e., at P 2.15-2.40 GPa and T 500-550 °C), and closely associated with fluid circulations. Our study demonstrates that crustal material, buried along the subduction interface at HP-LT conditions, can record several successive brittle events in places where deformation is classically envisioned as ductile. We suggest, based on our observations, that strain-rate increase along plate interface shear zones may trigger fracturing and fluid infiltration which in turn enables brittle-ductile instabilities along these deformation networks.

  10. An elasto-plastic solution for channel cracking of brittle coating on polymer substrate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Chao; Chen, Fangliang; Gray, Matthew H.

    In this study, an elasto-plastic channel-cracking model is presented to study the open-mode fracture of a thin layer brittle coating grown on a polymer substrate. A linear elastic shear interlayer is introduced to describe the stress transfer from the elasto-plastic substrate to the brittle coating, on basis of the shear-lag principle. The channel cracking behavior involves three stages: elastic, elasto-plastic and plastic stages, which are solved in a continuous manner based on the deformation status of the substrate. Explicit solutions are derived for the mutli-stage cracking process. Corresponding experimental tests for a titanium oxide (TiO 2) coating on a polymore » (ethylene terephthalate) substrate are conducted. The fracture toughness of the coating layer is estimated based on the crack spacing versus layer thickness relationship at certain strain levels. This method is found to be more reliable than the traditional methods using crack onset strain. Parametric studies of the fracture energy release rate for the coating and interfacial compliance of the thin film system are conducted, through which the effect of plastic deformation on the channel cracking behavior is studied extensively. The results indicate that the tangent modulus of the substrate controls the evolution curvature of crack spacing where a smaller tangent modulus corresponds to a slower saturation of crack spacing. The energy release rate also varies significantly with the properties of the interlayer. The study highlights the necessity of an elasto-plastic model for the thin film systems of brittle coating on a plastic substrate.« less

  11. An elasto-plastic solution for channel cracking of brittle coating on polymer substrate

    DOE PAGES

    Zhang, Chao; Chen, Fangliang; Gray, Matthew H.; ...

    2017-04-25

    In this study, an elasto-plastic channel-cracking model is presented to study the open-mode fracture of a thin layer brittle coating grown on a polymer substrate. A linear elastic shear interlayer is introduced to describe the stress transfer from the elasto-plastic substrate to the brittle coating, on basis of the shear-lag principle. The channel cracking behavior involves three stages: elastic, elasto-plastic and plastic stages, which are solved in a continuous manner based on the deformation status of the substrate. Explicit solutions are derived for the mutli-stage cracking process. Corresponding experimental tests for a titanium oxide (TiO 2) coating on a polymore » (ethylene terephthalate) substrate are conducted. The fracture toughness of the coating layer is estimated based on the crack spacing versus layer thickness relationship at certain strain levels. This method is found to be more reliable than the traditional methods using crack onset strain. Parametric studies of the fracture energy release rate for the coating and interfacial compliance of the thin film system are conducted, through which the effect of plastic deformation on the channel cracking behavior is studied extensively. The results indicate that the tangent modulus of the substrate controls the evolution curvature of crack spacing where a smaller tangent modulus corresponds to a slower saturation of crack spacing. The energy release rate also varies significantly with the properties of the interlayer. The study highlights the necessity of an elasto-plastic model for the thin film systems of brittle coating on a plastic substrate.« less

  12. Ductile-brittle transition of thoriated chromium.

    NASA Technical Reports Server (NTRS)

    Wilcox, B. A.; Veigel, N. D.; Clauer, A. H.

    1972-01-01

    Unalloyed chromium and chromium containing approximately 3 wt % ThO2 were prepared from powder produced by a chemical vapor deposition process. When rolled to sheet and tested in tension, it was found that the thoriated material had a lower ductile-to-brittle transition temperature (DBTT) than unalloyed chromium. This ductilizing was evident both in the as-rolled condition and after the materials had been annealed for 1 hour at 1200 C. The improved ductility in thoriated chromium may be associated with several possible mechanisms: (1) particles may disperse slip, such that critical stress or strain concentrations for crack nucleation are more difficult to achieve; (2) particles may act as dislocation sources, thus providing mobile dislocations in this normally source-poor material, in a manner similar to prestraining; and (3) particles in grain boundaries may help to transmit slip across the boundaries, thus relieving stress concentrations and inhibiting crack nucleation.

  13. Geometric consequences of ductile fabric development from brittle shear faults in mafic melt sheets: Evidence from the Sudbury Igneous Complex, Canada

    NASA Astrophysics Data System (ADS)

    Lenauer, Iris; Riller, Ulrich

    2012-02-01

    Compared to felsic igneous rocks the genetic relationship between brittle and ductile fabric development and its influence on the geometry of deformed mafic melt sheets has received little attention in structural analyses. We explore these relationships using the Sudbury Igneous Complex (SIC) as an example. The SIC is the relic of a layered impact melt sheet that was transformed into a fold basin, the Sudbury Basin, during Paleoproterozoic deformation at the southern margin of the Archean Superior Province. We studied brittle and ductile strain fabrics on the outcrop and map scales in the southern Sudbury Basin, notably in the Norite and Quartz Gabbro layers of the SIC. Here, deformation is heterogeneous and occurred under variable rheological conditions, evident by the development of brittle shear fractures, brittle-ductile shear zones and pervasive ductile strain. The mineral fabrics formed under low- to middle greenschist-facies metamorphism, whereby brittle deformation caused hydrolytic weakening and ductile fabric development. Principal strain axes inferred from all structural elements are collinear and point to a single deformation regime that led to thinning of SIC layers during progressive deformation. Ductile fabric development profoundly influenced the orientation of SIC material planes, such as lithological contacts and magmatic mineral fabrics. More specifically, these planar structural elements are steep where the SIC underwent large magnitudes of thinning, i.e., in the south limb of the Sudbury Basin. Here, the actual tilt component of material planes is likely smaller than its maximum total rotation (60°) inferred from inclined igneous layering in the Norite. Our field-based study shows that ductile fabric development from brittle faults can have a profound influence on the rotational components of primary material planes in deformed igneous melt sheets.

  14. Multi-scale modeling of microstructure dependent intergranular brittle fracture using a quantitative phase-field based method

    DOE PAGES

    Chakraborty, Pritam; Zhang, Yongfeng; Tonks, Michael R.

    2015-12-07

    In this study, the fracture behavior of brittle materials is strongly influenced by their underlying microstructure that needs explicit consideration for accurate prediction of fracture properties and the associated scatter. In this work, a hierarchical multi-scale approach is pursued to model microstructure sensitive brittle fracture. A quantitative phase-field based fracture model is utilized to capture the complex crack growth behavior in the microstructure and the related parameters are calibrated from lower length scale atomistic simulations instead of engineering scale experimental data. The workability of this approach is demonstrated by performing porosity dependent intergranular fracture simulations in UO 2 and comparingmore » the predictions with experiments.« less

  15. Multi-scale modeling of microstructure dependent intergranular brittle fracture using a quantitative phase-field based method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chakraborty, Pritam; Zhang, Yongfeng; Tonks, Michael R.

    In this study, the fracture behavior of brittle materials is strongly influenced by their underlying microstructure that needs explicit consideration for accurate prediction of fracture properties and the associated scatter. In this work, a hierarchical multi-scale approach is pursued to model microstructure sensitive brittle fracture. A quantitative phase-field based fracture model is utilized to capture the complex crack growth behavior in the microstructure and the related parameters are calibrated from lower length scale atomistic simulations instead of engineering scale experimental data. The workability of this approach is demonstrated by performing porosity dependent intergranular fracture simulations in UO 2 and comparingmore » the predictions with experiments.« less

  16. The failure of brittle materials under overall compression: Effects of loading rate and defect distribution

    NASA Astrophysics Data System (ADS)

    Paliwal, Bhasker

    The constitutive behaviors and failure processes of brittle materials under far-field compressive loading are studied in this work. Several approaches are used: experiments to study the compressive failure behavior of ceramics, design of experimental techniques by means of finite element simulations, and the development of micro-mechanical damage models to analyze and predict mechanical response of brittle materials under far-field compression. Experiments have been conducted on various ceramics, (primarily on a transparent polycrystalline ceramic, aluminum oxynitride or AlON) under loading rates ranging from quasi-static (˜ 5X10-6) to dynamic (˜ 200 MPa/mus), using a servo-controlled hydraulic test machine and a modified compression Kolsky bar (MKB) technique respectively. High-speed photography has also been used with exposure times as low as 20 ns to observe the dynamic activation, growth and coalescence of cracks and resulting damage zones in the specimen. The photographs were correlated in time with measurements of the stresses in the specimen. Further, by means of 3D finite element simulations, an experimental technique has been developed to impose a controlled, homogeneous, planar confinement in the specimen. The technique can be used in conjunction with a high-speed camera to study the in situ dynamic failure behavior of materials under confinement. AlON specimens are used for the study. The statically pre-compressed specimen is subjected to axial dynamic compressive loading using the MKB. Results suggest that confinement not only increases the load carrying capacity, it also results in a non-linear stress evolution in the material. High-speed photographs also suggest an inelastic deformation mechanism in AlON under confinement which evolves more slowly than the typical brittle-cracking type of damage in the unconfined case. Next, an interacting micro-crack damage model is developed that explicitly accounts for the interaction among the micro-cracks in

  17. An investigation of the mineral in ductile and brittle cortical mouse bone.

    PubMed

    Rodriguez-Florez, Naiara; Garcia-Tunon, Esther; Mukadam, Quresh; Saiz, Eduardo; Oldknow, Karla J; Farquharson, Colin; Millán, José Luis; Boyde, Alan; Shefelbine, Sandra J

    2015-05-01

    Bone is a strong and tough material composed of apatite mineral, organic matter, and water. Changes in composition and organization of these building blocks affect bone's mechanical integrity. Skeletal disorders often affect bone's mineral phase, either by variations in the collagen or directly altering mineralization. The aim of the current study was to explore the differences in the mineral of brittle and ductile cortical bone at the mineral (nm) and tissue (µm) levels using two mouse phenotypes. Osteogenesis imperfecta model, oim(-/-) , mice have a defect in the collagen, which leads to brittle bone; PHOSPHO1 mutants, Phospho1(-/-) , have ductile bone resulting from altered mineralization. Oim(-/-) and Phospho1(-/-) were compared with their respective wild-type controls. Femora were defatted and ground to powder to measure average mineral crystal size using X-ray diffraction (XRD) and to monitor the bulk mineral to matrix ratio via thermogravimetric analysis (TGA). XRD scans were run after TGA for phase identification to assess the fractions of hydroxyapatite and β-tricalcium phosphate. Tibiae were embedded to measure elastic properties with nanoindentation and the extent of mineralization with backscattered electron microscopy (BSE SEM). Results revealed that although both pathology models had extremely different whole-bone mechanics, they both had smaller apatite crystals, lower bulk mineral to matrix ratio, and showed more thermal conversion to β-tricalcium phosphate than their wild types, indicating deviations from stoichiometric hydroxyapatite in the original mineral. In contrast, the degree of mineralization of bone matrix was different for each strain: brittle oim(-/-) were hypermineralized, whereas ductile Phospho1(-/-) were hypomineralized. Despite differences in the mineralization, nanoscale alterations in the mineral were associated with reduced tissue elastic moduli in both pathologies. Results indicated that alterations from normal crystal size

  18. Learning Embedded Software Design in an Open 3A Multiuser Laboratory

    ERIC Educational Resources Information Center

    Shih, Chien-Chou; Hwang, Lain-Jinn

    2011-01-01

    The need for professional programmers in embedded applications has become critical for industry growth. This need has increased the popularity of embedded software design courses, which are resource-intensive and space-limited in traditional real lab-based instruction. To overcome geographic and time barriers in enhancing practical skills that…

  19. Software Project Management and Measurement on the World-Wide-Web (WWW)

    NASA Technical Reports Server (NTRS)

    Callahan, John; Ramakrishnan, Sudhaka

    1996-01-01

    We briefly describe a system for forms-based, work-flow management that helps members of a software development team overcome geographical barriers to collaboration. Our system, called the Web Integrated Software Environment (WISE), is implemented as a World-Wide-Web service that allows for management and measurement of software development projects based on dynamic analysis of change activity in the workflow. WISE tracks issues in a software development process, provides informal communication between the users with different roles, supports to-do lists, and helps in software process improvement. WISE minimizes the time devoted to metrics collection and analysis by providing implicit delivery of messages between users based on the content of project documents. The use of a database in WISE is hidden from the users who view WISE as maintaining a personal 'to-do list' of tasks related to the many projects on which they may play different roles.

  20. Life Predicted in a Probabilistic Design Space for Brittle Materials With Transient Loads

    NASA Technical Reports Server (NTRS)

    Nemeth, Noel N.; Palfi, Tamas; Reh, Stefan

    2005-01-01

    Analytical techniques have progressively become more sophisticated, and now we can consider the probabilistic nature of the entire space of random input variables on the lifetime reliability of brittle structures. This was demonstrated with NASA s CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code combined with the commercially available ANSYS/Probabilistic Design System (ANSYS/PDS), a probabilistic analysis tool that is an integral part of the ANSYS finite-element analysis program. ANSYS/PDS allows probabilistic loads, component geometry, and material properties to be considered in the finite-element analysis. CARES/Life predicts the time dependent probability of failure of brittle material structures under generalized thermomechanical loading--such as that found in a turbine engine hot-section. Glenn researchers coupled ANSYS/PDS with CARES/Life to assess the effects of the stochastic variables of component geometry, loading, and material properties on the predicted life of the component for fully transient thermomechanical loading and cyclic loading.

  1. The transition from brittle faulting to cataclastic flow: Permeability evolution

    NASA Astrophysics Data System (ADS)

    Zhu, Wenlu; Wong, Teng-Fong

    1997-02-01

    Triaxial compression experiments were conducted to investigate influences of stress and failure mode on axial permeability of five sandstones with porosities ranging from 15% to 35%. In the cataclastic flow regime, permeability and porosity changes closely track one another. A drastic decrease in permeability was triggered by the onset of shear-enhanced compaction caused by grain crushing and pore collapse. The compactive yield stress C* maps out a boundary in stress space separating two different types of permeability evolution. Before C* is attained, permeability and porosity both decrease with increasing effective mean stress, but they are independent of deviatoric stresses. However, with loading beyond C*, both permeability and porosity changes are strongly dependent on the deviatoric and effective mean stresses. In the brittle faulting regime, permeability and porosity changes are more complex. Before the onset of shear-induced dilation C', both permeability and porosity decrease with increasing effective mean stress. Beyond C', permeability may actually decrease in a dilating rock prior to brittle failure. After the peak stress has been attained, the development of a relatively impermeable shear band causes an accelerated decrease of permeability. Permeability evolution in porous sandstones is compared with that in low-porosity crystalline rocks. A conceptual model for the coupling of deformation and fluid transport is proposed in the form of a deformation-permeability map.

  2. Brittle fracture in viscoelastic materials as a pattern-formation process

    NASA Astrophysics Data System (ADS)

    Fleck, M.; Pilipenko, D.; Spatschek, R.; Brener, E. A.

    2011-04-01

    A continuum model of crack propagation in brittle viscoelastic materials is presented and discussed. Thereby, the phenomenon of fracture is understood as an elastically induced nonequilibrium interfacial pattern formation process. In this spirit, a full description of a propagating crack provides the determination of the entire time dependent shape of the crack surface, which is assumed to be extended over a finite and self-consistently selected length scale. The mechanism of crack propagation, that is, the motion of the crack surface, is then determined through linear nonequilibrium transport equations. Here we consider two different mechanisms, a first-order phase transformation and surface diffusion. We give scaling arguments showing that steady-state solutions with a self-consistently selected propagation velocity and crack shape can exist provided that elastodynamic or viscoelastic effects are taken into account, whereas static elasticity alone is not sufficient. In this respect, inertial effects as well as viscous damping are identified to be sufficient crack tip selection mechanisms. Exploring the arising description of brittle fracture numerically, we study steady-state crack propagation in the viscoelastic and inertia limit as well as in an intermediate regime, where both effects are important. The arising free boundary problems are solved by phase field methods and a sharp interface approach using a multipole expansion technique. Different types of loading, mode I, mode III fracture, as well as mixtures of them, are discussed.

  3. Differential growth forms of the sponge Biemna fortis govern the abundance of its associated brittle star Ophiactis modesta

    NASA Astrophysics Data System (ADS)

    Dahihande, Azraj S.; Thakur, Narsinh L.

    2017-08-01

    Marine intertidal regions are physically stressful habitats. In such an environment, facilitator species and positive interactions mitigate unfavorable conditions to the benefit of less tolerant organisms. In sponge-brittle star association, sponges effectively shelter brittle stars from biotic and abiotic stresses. The sponge, Biemna fortis (Topsent, 1897) was examined from two intertidal regions Anjuna and Mhapan along the Central West Coast of India for associated brittle star Ophiactis modesta (Brock, 1888) during 2013-2014. The study sites varied in suspended particulate matter (SPM). B. fortis at the high SPM habitat (Anjuna) had partially buried growth form and at the low SPM habitat (Mhapan) had massive growth form. O. modesta was abundantly associated with the massive growth form (50-259 individuals per 500 ml sponge) but rarely occurred in association with partially buried growth form (6-16 individuals per 500 ml sponge). In laboratory choice assay O. modesta showed equal preference to the chemical cues from both the growth forms of B. fortis. In addition, O. modesta showed significant preference to B. fortis compared to other sympatric sponges. These observations highlight the involvement of chemical cues in host recognition by O. modesta. Massive growth forms transplanted to the high SPM habitat were unable to survive but partially buried growth forms transplanted to the low SPM habitat were able to survive. Differential growth forms of the host sponge B. fortis at different abiotic stresses affect the abundance of the associated brittle star O. modesta.

  4. Failure processes in soft and quasi-brittle materials with nonhomogeneous microstructures

    NASA Astrophysics Data System (ADS)

    Spring, Daniel W.

    , coupled cohesive-friction relation and detail its formulation and implementation. In the process of this investigation, we developed a small library of cohesive elements for use with a commercially available finite element analysis software package. Additionally, in this thesis, we present a series of methods for reducing mesh dependency in two-dimensional dynamic cohesive fracture simulations of quasi-brittle materials. In this setting, cracks are only permitted to propagate along element facets, thus a poorly designed discretization of the problem domain can introduce artifacts into the fracture behavior. To reduce mesh induced artifacts, we consider unstructured polygonal finite elements. A randomly-seeded polygonal mesh leads to an isotropic discretization of the problem domain, which does not bias the direction of crack propagation. However, polygonal meshes tend to limit the possible directions a crack may travel at each node, making this discretization a poor candidate for dynamic cohesive fracture simulations. To alleviate this problem, we propose two new topological operators. The first operator we propose is adaptive element-splitting, and the second is adaptive mesh refinement. Both operators are designed to improve the ability of unstructured polygonal meshes to capture crack patterns in dynamic cohesive fracture simulations. However, we demonstrate that element-splitting is more suited to pervasive fracture problems, whereas, adaptive refinement is more suited to problems exhibiting a dominant crack. Finally, we investigate the use of geometric and constitutive design features to regularize pervasive fragmentation behavior in three-dimensions. Throughout pervasive fracture simulations, many cracks initiate, propagate, branch and coalesce simultaneously. Because of the cohesive element method's unique framework, this behavior can be captured in a regularized manner. In this investigation, unstructuring techniques are used to introduce randomness into a

  5. Three-dimensional high-entropy alloy-polymer composite nanolattices that overcome the strength-recoverability trade-off.

    PubMed

    Zhang, Xuan; Yao, Jiahao; Liu, Bin; Yan, Jun; Lu, Lei; Li, Yi; Gao, Huajian; Li, Xiaoyan

    2018-06-14

    Mechanical metamaterials with three-dimensional micro- and nano-architectures exhibit unique mechanical properties, such as high specific modulus, specific strength and energy absorption. However, a conflict exists between strength and recoverability in nearly all the mechanical metamaterials reported recently, in particular the architected micro-/nanolattices, which restricts the applications of these materials in energy storage/absorption and mechanical actuation. Here, we demonstrated the fabrication of three-dimensional architected composite nanolattices that overcome the strength-recoverability trade-off. The nanolattices under study are made up of a high entropy alloy coated (14.2-126.1 nm in thickness) polymer strut (approximately 260 nm in the characteristic size) fabricated via two-photon lithography and magnetron sputtering deposition. In situ uniaxial compression inside a scanning electron microscope showed that these composite nanolattices exhibit a high specific strength of 0.027 MPa/kg m3, an ultra-high energy absorption per unit volume of 4.0 MJ/m3, and nearly complete recovery after compression under strains exceeding 50%, thus overcoming the traditional strength-recoverability trade-off. During multiple compression cycles, the composite nanolattices exhibit a high energy loss coefficient (converged value after multiple cycles) of 0.5-0.6 at a compressive strain beyond 50%, surpassing the coefficients of all the micro-/nanolattices fabricated recently. Our experiments also revealed that for a given unit cell size, the composite nanolattices coated with a high entropy alloy with thickness in the range of 14-50 nm have the optimal specific modulus, specific strength and energy absorption per unit volume, which is related to a transition of the dominant deformation mechanism from local buckling to brittle fracture of the struts.

  6. Dilatancy induced ductile-brittle transition of shear band in metallic glasses.

    PubMed

    Zeng, F; Jiang, M Q; Dai, L H

    2018-04-01

    Dilatancy-generated structural disordering, an inherent feature of metallic glasses (MGs), has been widely accepted as the physical mechanism for the primary origin and structural evolution of shear banding, as well as the resultant shear failure. However, it remains a great challenge to determine, to what degree of dilatation, a shear banding will evolve into a runaway shear failure. In this work, using in situ acoustic emission monitoring, we probe the dilatancy evolution at the different stages of individual shear band in MGs that underwent severely plastic deformation by the controlled cutting technology. A scaling law is revealed that the dilatancy in a shear band is linearly related to its evolution degree. A transition from ductile-to-brittle shear bands is observed, where the formers dominate stable serrated flow, and the latter lead to a runaway instability (catastrophe failure) of serrated flow. To uncover the underlying mechanics, we develop a theoretical model of shear-band evolution dynamics taking into account an atomic-scale deformation process. Our theoretical results agree with the experimental observations, and demonstrate that the atomic-scale volume expansion arises from an intrinsic shear-band evolution dynamics. Importantly, the onset of the ductile-brittle transition of shear banding is controlled by a critical dilatation.

  7. Dilatancy induced ductile-brittle transition of shear band in metallic glasses

    NASA Astrophysics Data System (ADS)

    Zeng, F.; Jiang, M. Q.; Dai, L. H.

    2018-04-01

    Dilatancy-generated structural disordering, an inherent feature of metallic glasses (MGs), has been widely accepted as the physical mechanism for the primary origin and structural evolution of shear banding, as well as the resultant shear failure. However, it remains a great challenge to determine, to what degree of dilatation, a shear banding will evolve into a runaway shear failure. In this work, using in situ acoustic emission monitoring, we probe the dilatancy evolution at the different stages of individual shear band in MGs that underwent severely plastic deformation by the controlled cutting technology. A scaling law is revealed that the dilatancy in a shear band is linearly related to its evolution degree. A transition from ductile-to-brittle shear bands is observed, where the formers dominate stable serrated flow, and the latter lead to a runaway instability (catastrophe failure) of serrated flow. To uncover the underlying mechanics, we develop a theoretical model of shear-band evolution dynamics taking into account an atomic-scale deformation process. Our theoretical results agree with the experimental observations, and demonstrate that the atomic-scale volume expansion arises from an intrinsic shear-band evolution dynamics. Importantly, the onset of the ductile-brittle transition of shear banding is controlled by a critical dilatation.

  8. Direct observation of fault zone structure at the brittle-ductile transition along the Salzach-Ennstal-Mariazell-Puchberg fault system, Austrian Alps

    NASA Astrophysics Data System (ADS)

    Frost, Erik; Dolan, James; Ratschbacher, Lothar; Hacker, Bradley; Seward, Gareth

    2011-02-01

    Structural analysis of two key exposures reveals the architecture of the brittle-ductile transition (BDT) of the subvertical, strike-slip Salzachtal fault. At Lichtensteinklamm, the fault zone is dominantly brittle, with a ˜70 m wide, high-strain fault core highlighted by a 50 m thick, highly foliated gouge zone. In contrast, at Kitzlochklamm, deformation is dominantly ductile, albeit with relatively low strain indicated by weak lattice-preferred orientations (LPOs). The marked contrast in structural style indicates that these sites span the BDT. The close proximity of the outcrops, coupled with Raman spectroscopy indicating similar maximum temperatures of ˜400°C, suggests that the difference in exhumation depth is small, with a commensurately small difference in total downdip width of the BDT. The small strains indicated by weak LPOs at Kitzlochklamm, coupled with evidence for brittle slip at the main fault contact and along the sides of a 5 m wide fault-bounded sliver of Klammkalk exposed 30 m into the Grauwacken zone rocks, suggest the possibility that this exposure may record hybrid behavior at different times during the earthquake cycle, with ductile deformation occurring during slow interseismic slip and brittle deformation occurring during earthquakes, as dynamic coseismic stresses induced a strain rate-dependent shift to brittle fault behavior within the nominally ductile regime in the lower part of the BDT. A key aspect of both outcrops is evidence of a high degree of strain localization through the BDT, with high-strain fault cores no wider than a few tens of meters.

  9. Software Systems for High-performance Quantum Computing

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Humble, Travis S; Britt, Keith A

    Quantum computing promises new opportunities for solving hard computational problems, but harnessing this novelty requires breakthrough concepts in the design, operation, and application of computing systems. We define some of the challenges facing the development of quantum computing systems as well as software-based approaches that can be used to overcome these challenges. Following a brief overview of the state of the art, we present models for the quantum programming and execution models, the development of architectures for hybrid high-performance computing systems, and the realization of software stacks for quantum networking. This leads to a discussion of the role that conventionalmore » computing plays in the quantum paradigm and how some of the current challenges for exascale computing overlap with those facing quantum computing.« less

  10. Real-Time Extended Interface Automata for Software Testing Cases Generation

    PubMed Central

    Yang, Shunkun; Xu, Jiaqi; Man, Tianlong; Liu, Bin

    2014-01-01

    Testing and verification of the interface between software components are particularly important due to the large number of complex interactions, which requires the traditional modeling languages to overcome the existing shortcomings in the aspects of temporal information description and software testing input controlling. This paper presents the real-time extended interface automata (RTEIA) which adds clearer and more detailed temporal information description by the application of time words. We also establish the input interface automaton for every input in order to solve the problems of input controlling and interface covering nimbly when applied in the software testing field. Detailed definitions of the RTEIA and the testing cases generation algorithm are provided in this paper. The feasibility and efficiency of this method have been verified in the testing of one real aircraft braking system. PMID:24892080

  11. AN INVESTIGATION OF THE MINERAL IN DUCTILE AND BRITTLE CORTICAL MOUSE BONE

    PubMed Central

    Rodriguez-Florez, Naiara; Garcia-Tunon, Esther; Mukadam, Quresh; Saiz, Eduardo; Oldknow, Karla J.; Farquharson, Colin; Millán, José Luis; Boyde, Alan; Shefelbine, Sandra J.

    2015-01-01

    Bone is a strong and tough material composed of apatite mineral, organic matter and water. Changes in composition and organization of these building blocks affect bone’s mechanical integrity. Skeletal disorders often affect bone’s mineral phase, either by variations in the collagen or directly altering mineralization. The aim of the current study was to explore the differences in the mineral of brittle and ductile cortical bone at the mineral (nm) and tissue (µm) levels using two mouse phenotypes. Osteogenesis imperfecta murine (oim−/−) mice were used to model brittle bone; PHOSPHO1 mutants (Phospho1−/−) had ductile bone. They were compared to their respective wild-type controls. Femora were defatted and ground to powder to measure average mineral crystal size using X-ray diffraction (XRD), and to monitor the bulk mineral to matrix ratio via thermogravimetric analysis (TGA). XRD scans were run after TGA for phase identification, to assess the fractions of hydroxyapatite and β-tricalcium phosphate. Tibiae were embedded to measure elastic properties with nanoindentation and the extent of mineralization with backscattered electron microscopy (qbSEM). Interestingly, the mineral of brittle oim−/− and ductile Phospho1−/− bones had many similar characteristics. Both pathology models had smaller apatite crystals, lower mineral to matrix ratio, and showed more thermal conversion to β-tricalcium phosphate than their wild-types, indicating deviations from stoichiometric hydroxyapatite in the original mineral. The degree of mineralization of the bone matrix was different for each strain: oim−/− were hypermineralized, while Phospho1−/− were hypomineralized. However, alterations in the mineral were associated with reduced tissue elastic moduli in both pathologies. Results revealed that despite having extremely different whole bone mechanics, the mineral of oim−/− and Phospho1−/− has several similar trends at smaller length scales. This

  12. Design with brittle materials - An interdisciplinary educational program

    NASA Technical Reports Server (NTRS)

    Mueller, J. I.; Bollard, R. J. H.; Hartz, B. J.; Kobayashi, A. S.; Love, W. J.; Scott, W. D.; Taggart, R.; Whittemore, O. J.

    1980-01-01

    A series of interdisciplinary design courses being offered to senior and graduate engineering students at the University of Washington is described. Attention is given to the concepts and some of the details on group design projects that have been undertaken during the past two years. It is noted that ceramic materials normally demonstrate a large scatter in strength properties. As a consequence, when designing with these materials, the conventional 'mil standards' design stresses with acceptable margins of safety cannot by employed and the designer is forced to accept a probable number of failures in structures of a given brittle material. It is this prediction of the probability of failure for structures of given, well-characterized materials that forms the basis for this series of courses.

  13. A New Species of Sexually Dimorphic Brittle Star of the Genus Ophiodaphne (Echinodermata: Ophiuroidea).

    PubMed

    Tominaga, Hideyuki; Hirose, Mamiko; Igarashi, Hikaru; Kiyomoto, Masato; Komatsu, Miéko

    2017-08-01

    We describe a new species of sexually dimorphic brittle star, Ophiodaphne spinosa, from Japan associated with the irregular sea urchin, Clypeaster japonicus based on its external morphology, and phylogenetic analyses of mitochondrial COI (cytochrome c oxidase subunit I). Females of this new species of Ophiodaphne are characterized mainly by the presence of wavy grooves on the surface of the radial shields, needle-like thorns on the oral skeletal jaw structures, and a low length-to-width ratio of the jaw angle in comparison with those of type specimens of its Ophiodaphne congeners: O. scripta, O. materna, and O. formata. A tabular key to the species characteristics of Ophiodaphne is provided. Phylogenetic analyses indicate that the new species of Ophiodaphne, O. scripta, and O. formata are monophyletic. Our results indicate that the Japanese Ophiodaphne include both the new species and O. scripta, and that there are four Ophiodaphne species of sexually dimorphic brittle stars with androphorous habit.

  14. The Brittleness and Chemical Stability of Optimized Geopolymer Composites

    PubMed Central

    Steinerova, Michaela; Matulova, Lenka; Vermach, Pavel; Kotas, Jindrich

    2017-01-01

    Geopolymers are known as high strength and durable construction materials but have a brittle fracture. In practice, this results in a sudden collapse at ultimate load, without any chance of preventing the breakdown of parts or of withstanding the stress for some time. Glass fiber usage as a total anisotropic shape acting as a compact structure component should hinder the fracture mechanism. The optimized compositions in this study led to a significant reinforcement, especially in the case of flexural strength, but also in terms of the compressive strength and notch toughness. The positive and negative influence of the fibers on the complex composite properties provided chemical stability. PMID:28772756

  15. The Brittleness and Chemical Stability of Optimized Geopolymer Composites.

    PubMed

    Steinerova, Michaela; Matulova, Lenka; Vermach, Pavel; Kotas, Jindrich

    2017-04-09

    Geopolymers are known as high strength and durable construction materials but have a brittle fracture. In practice, this results in a sudden collapse at ultimate load, without any chance of preventing the breakdown of parts or of withstanding the stress for some time. Glass fiber usage as a total anisotropic shape acting as a compact structure component should hinder the fracture mechanism. The optimized compositions in this study led to a significant reinforcement, especially in the case of flexural strength, but also in terms of the compressive strength and notch toughness. The positive and negative influence of the fibers on the complex composite properties provided chemical stability.

  16. Maize Brittle stalk2 Encodes a COBRA-Like Protein Expressed in Early Organ Development But Required for Tissue Flexibility at Maturity1[C][OA

    PubMed Central

    Sindhu, Anoop; Langewisch, Tiffany; Olek, Anna; Multani, Dilbag S.; McCann, Maureen C.; Vermerris, Wilfred; Carpita, Nicholas C.; Johal, Gurmukh

    2007-01-01

    The maize (Zea mays) brittle stalk2 (bk2) is a recessive mutant, the aerial parts of which are easily broken. The bk2 phenotype is developmentally regulated and appears 4 weeks after planting, at about the fifth-leaf stage. Before this time, mutants are indistinguishable from wild-type siblings. Afterward, all organs of the bk2 mutants turn brittle, even the preexisting ones, and they remain brittle throughout the life of the plant. Leaf tension assays and bend tests of the internodes show that the brittle phenotype does not result from loss of tensile strength but from loss in flexibility that causes the tissues to snap instead of bend. The Bk2 gene was cloned by a combination of transposon tagging and a candidate gene approach and found to encode a COBRA-like protein similar to rice (Oryza sativa) BC1 and Arabidopsis (Arabidopsis thaliana) COBRA-LIKE4. The outer periphery of the stalk has fewer vascular bundles, and the sclerids underlying the epidermis possess thinner secondary walls. Relative cellulose content is not strictly correlated with the brittle phenotype. Cellulose content in mature zones of bk2 mature stems is lowered by 40% but is about the same as wild type in developing stems. Although relative cellulose content is lowered in leaves after the onset of the brittle phenotype, total wall mass as a proportion of dry mass is either unchanged or slightly increased, indicating a compensatory increase in noncellulosic carbohydrate mass. Fourier transform infrared spectra indicated an increase in phenolic ester content in the walls of bk2 leaves and stems. Total content of lignin is unaffected in bk2 juvenile leaves before or after appearance of the brittle phenotype, but bk2 mature and developing stems are markedly enriched in lignin compared to wild-type stems. Despite increased lignin in bk2 stems, loss of staining with phloroglucinol and ultraviolet autofluorescence is observed in vascular bundles and sclerid layers. Consistent with the infrared

  17. Estimation of brittleness indices for pay zone determination in a shale-gas reservoir by using elastic properties obtained from micromechanics

    NASA Astrophysics Data System (ADS)

    Lizcano-Hernández, Edgar G.; Nicolás-López, Rubén; Valdiviezo-Mijangos, Oscar C.; Meléndez-Martínez, Jaime

    2018-04-01

    The brittleness indices (BI) of gas-shales are computed by using their effective mechanical properties obtained from micromechanical self-consistent modeling with the purpose of assisting in the identification of the more-brittle regions in shale-gas reservoirs, i.e., the so-called ‘pay zone’. The obtained BI are plotted in lambda-rho versus mu-rho λ ρ -μ ρ and Young’s modulus versus Poisson’s ratio E-ν ternary diagrams along with the estimated elastic properties from log data of three productive shale-gas wells where the pay zone is already known. A quantitative comparison between the obtained BI and the well log data allows for the delimitation of regions where BI values could indicate the best reservoir target in regions with the highest shale-gas exploitation potential. Therefore, a range of values for elastic properties and brittleness indexes that can be used as a data source to support the well placement procedure is obtained.

  18. Analytical and numerical analysis of frictional damage in quasi brittle materials

    NASA Astrophysics Data System (ADS)

    Zhu, Q. Z.; Zhao, L. Y.; Shao, J. F.

    2016-07-01

    Frictional sliding and crack growth are two main dissipation processes in quasi brittle materials. The frictional sliding along closed cracks is the origin of macroscopic plastic deformation while the crack growth induces a material damage. The main difficulty of modeling is to consider the inherent coupling between these two processes. Various models and associated numerical algorithms have been proposed. But there are so far no analytical solutions even for simple loading paths for the validation of such algorithms. In this paper, we first present a micro-mechanical model taking into account the damage-friction coupling for a large class of quasi brittle materials. The model is formulated by combining a linear homogenization procedure with the Mori-Tanaka scheme and the irreversible thermodynamics framework. As an original contribution, a series of analytical solutions of stress-strain relations are developed for various loading paths. Based on the micro-mechanical model, two numerical integration algorithms are exploited. The first one involves a coupled friction/damage correction scheme, which is consistent with the coupling nature of the constitutive model. The second one contains a friction/damage decoupling scheme with two consecutive steps: the friction correction followed by the damage correction. With the analytical solutions as reference results, the two algorithms are assessed through a series of numerical tests. It is found that the decoupling correction scheme is efficient to guarantee a systematic numerical convergence.

  19. Brittle-to-ductile transition in a fiber bundle with strong heterogeneity.

    PubMed

    Kovács, Kornél; Hidalgo, Raul Cruz; Pagonabarraga, Ignacio; Kun, Ferenc

    2013-04-01

    We analyze the failure process of a two-component system with widely different fracture strength in the framework of a fiber bundle model with localized load sharing. A fraction 0≤α≤1 of the bundle is strong and it is represented by unbreakable fibers, while fibers of the weak component have randomly distributed failure strength. Computer simulations revealed that there exists a critical composition α(c) which separates two qualitatively different behaviors: Below the critical point, the failure of the bundle is brittle, characterized by an abrupt damage growth within the breakable part of the system. Above α(c), however, the macroscopic response becomes ductile, providing stability during the entire breaking process. The transition occurs at an astonishingly low fraction of strong fibers which can have importance for applications. We show that in the ductile phase, the size distribution of breaking bursts has a power law functional form with an exponent μ=2 followed by an exponential cutoff. In the brittle phase, the power law also prevails but with a higher exponent μ=9/2. The transition between the two phases shows analogies to continuous phase transitions. Analyzing the microstructure of the damage, it was found that at the beginning of the fracture process cracks nucleate randomly, while later on growth and coalescence of cracks dominate, which give rise to power law distributed crack sizes.

  20. Nanowire failure: long = brittle and short = ductile.

    PubMed

    Wu, Zhaoxuan; Zhang, Yong-Wei; Jhon, Mark H; Gao, Huajian; Srolovitz, David J

    2012-02-08

    Experimental studies of the tensile behavior of metallic nanowires show a wide range of failure modes, ranging from ductile necking to brittle/localized shear failure-often in the same diameter wires. We performed large-scale molecular dynamics simulations of copper nanowires with a range of nanowire lengths and provide unequivocal evidence for a transition in nanowire failure mode with change in nanowire length. Short nanowires fail via a ductile mode with serrated stress-strain curves, while long wires exhibit extreme shear localization and abrupt failure. We developed a simple model for predicting the critical nanowire length for this failure mode transition and showed that it is in excellent agreement with both the simulation results and the extant experimental data. The present results provide a new paradigm for the design of nanoscale mechanical systems that demarcates graceful and catastrophic failure. © 2012 American Chemical Society

  1. Elastic-Brittle-Plastic Behaviour of Shale Reservoirs and Its Implications on Fracture Permeability Variation: An Analytical Approach

    NASA Astrophysics Data System (ADS)

    Masoudian, Mohsen S.; Hashemi, Mir Amid; Tasalloti, Ali; Marshall, Alec M.

    2018-05-01

    Shale gas has recently gained significant attention as one of the most important unconventional gas resources. Shales are fine-grained rocks formed from the compaction of silt- and clay-sized particles and are characterised by their fissured texture and very low permeability. Gas exists in an adsorbed state on the surface of the organic content of the rock and is freely available within the primary and secondary porosity. Geomechanical studies have indicated that, depending on the clay content of the rock, shales can exhibit a brittle failure mechanism. Brittle failure leads to the reduced strength of the plastic zone around a wellbore, which can potentially result in wellbore instability problems. Desorption of gas during production can cause shrinkage of the organic content of the rock. This becomes more important when considering the use of shales for CO2 sequestration purposes, where CO2 adsorption-induced swelling can play an important role. These phenomena lead to changes in the stress state within the rock mass, which then influence the permeability of the reservoir. Thus, rigorous simulation of material failure within coupled hydro-mechanical analyses is needed to achieve a more systematic and accurate representation of the wellbore. Despite numerous modelling efforts related to permeability, an adequate representation of the geomechanical behaviour of shale and its impact on permeability and gas production has not been achieved. In order to achieve this aim, novel coupled poro-elastoplastic analytical solutions are developed in this paper which take into account the sorption-induced swelling and the brittle failure mechanism. These models employ linear elasticity and a Mohr-Coulomb failure criterion in a plane-strain condition with boundary conditions corresponding to both open-hole and cased-hole completions. The post-failure brittle behaviour of the rock is defined using residual strength parameters and a non-associated flow rule. Swelling and shrinkage

  2. Rheology of Pure Glasses and Crystal Bearing Melts: from the Newtonian Field to the Brittle Onset

    NASA Astrophysics Data System (ADS)

    Cordonnier, B.; Caricchi, L.; Pistone, M.; Castro, J. M.; Hess, K.; Dingwell, D. B.

    2010-12-01

    The brittle-ductile transition remains a central question of modern geology. If rocks can be perceived as a granular flow on geological time-scale, their behavior is brittle in dynamic areas. Understanding rock failure conditions is the main parameter in mitigating geological risks, more specifically the eruptive style transitions from effusive to explosive. If numerical simulations are the only way to fully understanding the physical processes involved, we are in a strong need of an experimental validation of the proposed models. here we present results obtained under torsion and uni-axial compression on both pure glasses and crystal bearing melts. We characterized the brittle onset of two phases magmas from 0 to 65% crystals. The strain-rates span a 5 orders magnitude range, from the Newtonian flow to the Brittle field (10-5 - 100 s-1). We particularly emphasize the time dependency of the measured rheology. The materials tested are a borosilicate glass from the National Bureau of Standards, a natural sample from Mt Unzen volcano and a synthetic sample. The lattest is an HPG8 melt with 7% sodium mole excess. The particles are quasi-isometric corundum crystalschosen for their shape and integrity under the stress range investigated. The crystal fraction ranges from 0 to 0.65. Concerning pure magmas, we recently demonstrated that the material passes from a Newtonian to a non-Nemtonian behavior with increasing strain-rate. This onset can mostly be explained by viscous-heating effects. However, for even greater strain-rates, the material cracks and finally fail. The brittle onset is here explained with the visco-elastic theory and corresponds to a Deborah number greater than 10-2. Concerning crystal bearing melts the departure from the Newtonian state is characterized by two effects: a shear-thinning and a time weakening effect. The first one is instantaneous and loading-unloading cyclic tests suggest an elastic contribution of the crystal network. The second one

  3. Helping Students Make Sense of Graphs: An Experimental Trial of SmartGraphs Software

    ERIC Educational Resources Information Center

    Zucker, Andrew; Kay, Rachel; Staudt, Carolyn

    2014-01-01

    Graphs are commonly used in science, mathematics, and social sciences to convey important concepts; yet students at all ages demonstrate difficulties interpreting graphs. This paper reports on an experimental study of free, Web-based software called SmartGraphs that is specifically designed to help students overcome their misconceptions regarding…

  4. Architecture independent environment for developing engineering software on MIMD computers

    NASA Technical Reports Server (NTRS)

    Valimohamed, Karim A.; Lopez, L. A.

    1990-01-01

    Engineers are constantly faced with solving problems of increasing complexity and detail. Multiple Instruction stream Multiple Data stream (MIMD) computers have been developed to overcome the performance limitations of serial computers. The hardware architectures of MIMD computers vary considerably and are much more sophisticated than serial computers. Developing large scale software for a variety of MIMD computers is difficult and expensive. There is a need to provide tools that facilitate programming these machines. First, the issues that must be considered to develop those tools are examined. The two main areas of concern were architecture independence and data management. Architecture independent software facilitates software portability and improves the longevity and utility of the software product. It provides some form of insurance for the investment of time and effort that goes into developing the software. The management of data is a crucial aspect of solving large engineering problems. It must be considered in light of the new hardware organizations that are available. Second, the functional design and implementation of a software environment that facilitates developing architecture independent software for large engineering applications are described. The topics of discussion include: a description of the model that supports the development of architecture independent software; identifying and exploiting concurrency within the application program; data coherence; engineering data base and memory management.

  5. The role of chemical processes and brittle deformation during shear zone formation and its potential geophysical implications

    NASA Astrophysics Data System (ADS)

    Goncalves, Philippe; Leydier, Thomas; Mahan, Kevin; Albaric, Julie; Trap, Pierre; Marquer, Didier

    2017-04-01

    Ductile shear zones in the middle and lower continental crust are the locus of interactions between mechanical and chemical processes. Chemical processes encompass metamorphic reactions, fluid-rock interactions, fluid flow and chemical mass-transfer. Studying these processes at the grain scale, and even the atom scale, on exposed inactive shear zones can give insights into large-scale geodynamics phenomena (e.g. crustal growth and mountain building through the reconstruction of P-T-t-D-Ɛ evolutionary paths. However, other major issues in earth sciences can be tackled through these studies as well. For instance, the mechanism of fluid flow and mass transfer in the deep crust where permeability should be small and transient is still largely debated. Studying exhumed inactive shear zones can also help to interpret several new geophysical observations like (1) the origin of tremor and very low frequency earthquakes observed in the ductile middle and lower crust, (2) mechanisms for generating slow slip events and (3) the physical origin of puzzling crustal anisotropy observed in major active crustal shear zones. In this contribution, we present a collection of data (deformation, petrology, geochemistry, microtexture) obtained on various shear zones from the Alps that were active within the viscous regime (T > 450°C). Our observations show that the development of a shear zone, from its nucleation to its growth and propagation, is not only governed by ductile deformation coeval with reactions but also involves brittle deformation. Although brittle deformation is a very short-lived phenomenon, our petrological and textural observations show that brittle failure is also associated with fluid flow, mass transfer, metasomatic reactions and recrystallization. We speculate that the fluids and the associated mineralogical changes involved during this brittle failure in the ductile crust might play a role in earthquake / tremor triggering below the brittle - ductile transition

  6. High-definition micropatterning method for hard, stiff and brittle polymers.

    PubMed

    Zhao, Yiping; Truckenmuller, Roman; Levers, Marloes; Hua, Wei-Shu; de Boer, Jan; Papenburg, Bernke

    2017-02-01

    Polystyrene (PS) is the most commonly used material in cell culture devices, such as Petri dishes, culture flasks and well plates. Micropatterning of cell culture substrates can significantly affect cell-material interactions leading to an increasing interest in the fabrication of topographically micro-structured PS surfaces. However, the high stiffness combined with brittleness of PS (elastic modulus 3-3.5GPa) makes high-quality patterning into PS difficult when standard hard molds, e.g. silicon and nickel, are used as templates. A new and robust scheme for easy processing of large-area high-density micro-patterning into PS film is established using nanoimprinting lithography and standard hot embossing techniques. Including an extra step through an intermediate PDMS mold alone does not result in faithful replication of the large area, high-density micropattern into PS. Here, we developed an approach using an additional intermediate mold out of OrmoStamp, which allows for high-quality and large-area micro-patterning into PS. OrmoStamp was originally developed for UV nanoimprint applications; this work demonstrates for the first time that OrmoStamp is a highly adequate material for micro-patterning of PS through hot embossing. Our proposed processing method achieves high-quality replication of micropatterns in PS, incorporating features with high aspect ratio (4:1, height:width), high density, and over a large pattern area. The proposed scheme can easily be adapted for other large-area and high-density micropatterns of PS, as well as other stiff and brittle polymers. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. On Failure in Polycrystalline and Amorphous Brittle Materials

    NASA Astrophysics Data System (ADS)

    Bourne, N. K.

    2009-12-01

    The performance of behaviour of brittle materials depends upon discrete deformation mechanisms operating during the loading process. The critical mechanisms determining the behaviour of armour ceramics have not been isolated using traditional ballistics. It has recently become possible to measure strength histories in materials under shock. The data gained for the failed strength of the armour are shown to relate directly to the penetration measured into tiles. Further the material can be loaded and recovered for post-mortem examination. Failure is by micro-fracture that is a function of the defects and then cracking activated by plasticity mechanisms within the grains and failure at grain boundaries in the amorphous intergranular phase. Thus it is the shock-induced plastic yielding of grains at the impact face that determines the later time penetration through the tile.

  8. The complex simplicity of the brittle star nervous system.

    PubMed

    Zueva, Olga; Khoury, Maleana; Heinzeller, Thomas; Mashanova, Daria; Mashanov, Vladimir

    2018-01-01

    Brittle stars (Ophiuroidea, Echinodermata) have been increasingly used in studies of animal behavior, locomotion, regeneration, physiology, and bioluminescence. The success of these studies directly depends on good working knowledge of the ophiuroid nervous system. Here, we describe the arm nervous system at different levels of organization, including the microanatomy of the radial nerve cord and peripheral nerves, ultrastructure of the neural tissue, and localization of different cell types using specific antibody markers. We standardize the nomenclature of nerves and ganglia, and provide an anatomically accurate digital 3D model of the arm nervous system as a reference for future studies. Our results helped identify several general features characteristic to the adult echinoderm nervous system, including the extensive anatomical interconnections between the ectoneural and hyponeural components, neuroepithelial organization of the central nervous system, and the supporting scaffold of the neuroepithelium formed by radial glial cells. In addition, we provide further support to the notion that the echinoderm radial glia is a complex and diverse cell population. We also tested the suitability of a range of specific cell-type markers for studies of the brittle star nervous system and established that the radial glial cells are reliably labeled with the ERG1 antibodies, whereas the best neuronal markers are acetylated tubulin, ELAV, and synaptotagmin B. The transcription factor Brn1/2/4 - a marker of neuronal progenitors - is expressed not only in neurons, but also in a subpopulation of radial glia. For the first time, we describe putative ophiuroid proprioceptors associated with the hyponeural part of the central nervous system. Together, our data help establish both the general principles of neural architecture common to the phylum Echinodermata and the specific ophiuroid features.

  9. The influence of temperature on brittle creep in sandstones

    NASA Astrophysics Data System (ADS)

    Heap, M. J.; Baud, P.; Meredith, P. G.; Vinciguerra, S.

    2009-04-01

    The characterization of time-dependent brittle rock deformation is fundamental to understanding the long-term evolution and dynamics of the Earth's upper crust. The presence of water promotes time-dependent deformation through environment-dependent stress corrosion cracking that allows rocks to deform at stresses far below their short-term failure stress. Here we report results from an experimental study of the influence of an elevated temperature on time-dependent brittle creep in water-saturated samples of Darley Dale (initial porosity of 13%), Bentheim (23%) and Crab Orchard (4%) sandstones. We present results from both conventional creep experiments (or ‘static fatigue' tests) and stress-stepping creep experiments performed under 20°C and 75°C and an effective confining pressure of 30 MPa (50 MPa confining pressure and a 20 MPa pore fluid pressure). The evolution of crack damage was monitored throughout each experiment by measuring the three proxies for damage (1) axial strain (2) pore volume change and (3) the output of AE energy. Conventional creep experiments have demonstrated that, for any given applied differential stress, the time-to-failure is dramatically reduced and the creep strain rate is significantly increased by application of an elevated temperature. Stress-stepping creep experiments have allowed us to investigate the influence of temperature in detail. Results from these experiments show that the creep strain rate for Darley Dale and Bentheim sandstones increases by approximately 3 orders of magnitude, and for Crab Orchard sandstone increases by approximately 2 orders of magnitude, as temperature is increased from 20°C to 75°C at a fixed effective differential stress. We discuss these results in the context of the different mineralogical and microstructural properties of the three rock types and the micro-mechanical and chemical processes operating on them.

  10. Brittle fracture damage around the Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Williams, J. N.; Toy, V.; Smith, S. A. F.; Boulton, C. J.; Massiot, C.; Mcnamara, D. D.

    2017-12-01

    We use field and drill-core samples to characterize macro- to micro-scale brittle fracture networks within the hanging-wall of New Zealand's Alpine Fault, an active plate-boundary fault that is approaching the end of its seismic cycle. Fracture density in the hanging-wall is roughly constant for distances of up to 500 m from the principal slip zone gouges (PSZs). Fractures >160 m from the PSZs are typically open and parallel to the regional mylonitic foliation or host rock schistosity, and likely formed as unloading joints during rapid exhumation of the hanging-wall at shallow depths. Fractures within c. 160 m of the PSZs are broadly oriented shear-fractures filled with gouge or cataclasite, and are interpreted to constitute the hanging-wall damage zone of the Alpine Fault. This is comparable to the 60-200 m wide "geophysical damage zone" estimated from low seismic wave velocities surrounding the Alpine Fault. Veins are pervasive within the c. 20 m-thick hanging-wall cataclasites and are most commonly filled by calcite, chlorite, muscovite and K-feldspar. Notably, there is a set of intragranular clast-hosted veins, as well as a younger set of veins that cross-cut both clasts and cataclasite matrix. The intragranular veins formed prior to cataclasis or during synchronous cataclasis and calcite-silicate mineralisation. Broad estimates for the depth of vein formation indicate that the cataclasites formed a c. 20 m wide actively deforming zone at depths of c. 4-8 km. Conversely, the cross-cutting veins are interpreted to represent off-fault damage within relatively indurated cataclasites following slip localization onto the <10 cm wide smectite-bearing PSZ gouges at depths of <4 km. Our observations therefore highlight a strong depth-dependence of the width of the actively deforming zone within the brittle seismogenic crust around the Alpine Fault.

  11. WISE: Automated support for software project management and measurement. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Ramakrishnan, Sudhakar

    1995-01-01

    One important aspect of software development and IV&V is measurement. Unless a software development effort is measured in some way, it is difficult to judge the effectiveness of current efforts and predict future performances. Collection of metrics and adherence to a process are difficult tasks in a software project. Change activity is a powerful indicator of project status. Automated systems that can handle change requests, issues, and other process documents provide an excellent platform for tracking the status of the project. A World Wide Web based architecture is developed for (a) making metrics collection an implicit part of the software process, (b) providing metric analysis dynamically, (c) supporting automated tools that can complement current practices of in-process improvement, and (d) overcoming geographical barrier. An operational system (WISE) instantiates this architecture allowing for the improvement of software process in a realistic environment. The tool tracks issues in software development process, provides informal communication between the users with different roles, supports to-do lists (TDL), and helps in software process improvement. WISE minimizes the time devoted to metrics collection, analysis, and captures software change data. Automated tools like WISE focus on understanding and managing the software process. The goal is improvement through measurement.

  12. Brittle strength of basaltic rock masses with applications to Venus

    NASA Astrophysics Data System (ADS)

    Schultz, R. A.

    1993-06-01

    Spacecraft images of surfaces with known or suspected basaltic composition on Venus (as well as on moon and Mars) indicate that these rocks have been deformed in the brittle regime to form faults and perhaps joints, in addition to folding and more distributed types of deformation. This paper presents results of detailed examinations and interpretations of Venus surface materials which show that the strengths of basaltic rocks on planetary surfaces and in the shallow subsurface are significantly different from strength values commonly used in tectonic modeling studies which assume properties of either intact rock samples or single planar shear surface.

  13. Effects of deformation-induced martensite and grain size on ductile-to-brittle transition behavior of austenitic 18Cr-10Mn-N stainless steels

    NASA Astrophysics Data System (ADS)

    Hwang, Byoungchul; Lee, Tae-Ho; Kim, Sung-Joon

    2010-12-01

    Effects of deformation-induced martensite and grain size on ductile-to-brittle transition behavior of austenitic 18Cr-10Mn-(0.3˜0.6)N stainless steels with different alloying elements were investigated by means of Charpy impact tests and microstructural analyses. The steels all exhibited ductile-to-brittle transition behavior due to unusual brittle fracture at low temperatures despite having a face-centered cubic structure. The ductileto-brittle transition temperature (DBTT) obtained from Chapry impact tests did not coincide with that predicted by an empirical equation depending on N content in austenitic Cr-Mn-N stainless steels. Furthermore, a decrease of grain size was not effective in terms of lowering DBTT. Electron back-scattered diffraction and transmission electron microscopy analyses of the cross-sectional area of the fracture surface showed that some austenites with lower stability could be transformed to α'-martensite by localized plastic deformation near the fracture surface. Based on these results, it was suggested that when austenitic 18Cr-10Mn-N stainless steels have limited Ni, Mo, and N content, the deterioration of austenite stability promotes the formation of deformation-induced martensite and thus increases DBTT by substantially decreasing low-temperature toughness.

  14. Software for computerised analysis of cardiotocographic traces.

    PubMed

    Romano, M; Bifulco, P; Ruffo, M; Improta, G; Clemente, F; Cesarelli, M

    2016-02-01

    Despite the widespread use of cardiotocography in foetal monitoring, the evaluation of foetal status suffers from a considerable inter and intra-observer variability. In order to overcome the main limitations of visual cardiotocographic assessment, computerised methods to analyse cardiotocographic recordings have been recently developed. In this study, a new software for automated analysis of foetal heart rate is presented. It allows an automatic procedure for measuring the most relevant parameters derivable from cardiotocographic traces. Simulated and real cardiotocographic traces were analysed to test software reliability. In artificial traces, we simulated a set number of events (accelerations, decelerations and contractions) to be recognised. In the case of real signals, instead, results of the computerised analysis were compared with the visual assessment performed by 18 expert clinicians and three performance indexes were computed to gain information about performances of the proposed software. The software showed preliminary performance we judged satisfactory in that the results matched completely the requirements, as proved by tests on artificial signals in which all simulated events were detected from the software. Performance indexes computed in comparison with obstetricians' evaluations are, on the contrary, not so satisfactory; in fact they led to obtain the following values of the statistical parameters: sensitivity equal to 93%, positive predictive value equal to 82% and accuracy equal to 77%. Very probably this arises from the high variability of trace annotation carried out by clinicians. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  15. A statistical model of brittle fracture by transgranular cleavage

    NASA Astrophysics Data System (ADS)

    Lin, Tsann; Evans, A. G.; Ritchie, R. O.

    A MODEL for brittle fracture by transgranular cleavage cracking is presented based on the application of weakest link statistics to the critical microstructural fracture mechanisms. The model permits prediction of the macroscopic fracture toughness, KI c, in single phase microstructures containing a known distribution of particles, and defines the critical distance from the crack tip at which the initial cracking event is most probable. The model is developed for unstable fracture ahead of a sharp crack considering both linear elastic and nonlinear elastic ("elastic/plastic") crack tip stress fields. Predictions are evaluated by comparison with experimental results on the low temperature flow and fracture behavior of a low carbon mild steel with a simple ferrite/grain boundary carbide microstructure.

  16. Instabilities of Damage and Surface Degradation Mechanisms in Brittle Material Structural Systems

    DTIC Science & Technology

    1992-03-15

    I INTRODUCTION AND SCOPE 1.1 General Brittle materials such as rock and concrete contain a multitude of defects in the form of micro-voids and/or...micro-cracks even before any external load is applied. The term "structure" is associated with such defects . During a loading- unloading process, these...voids/cracks may undergo irreversible growth and new ones may nucleate. The ultimate coalescence of such defects may result in macro- crack initiation

  17. Overcoming breastfeeding problems

    MedlinePlus

    Plugged milk ducts; Nipple soreness when breastfeeding; Breastfeeding - overcoming problems; Let-down reflex ... Breastfeeding (nursing) your baby can be a good experience for both the mother and the baby. It ...

  18. Assessment of brittleness and empirical correlations between physical and mechanical parameters of the Asmari limestone in Khersan 2 dam site, in southwest of Iran

    NASA Astrophysics Data System (ADS)

    Lashkaripour, Gholam Reza; Rastegarnia, Ahmad; Ghafoori, Mohammad

    2018-02-01

    The determination of brittleness and geomechanical parameters, especially uniaxial compressive strength (UCS) and Young's modulus (ES) of rocks are needed for the design of different rock engineering applications. Evaluation of these parameters are time-consuming processes, tedious, expensive and require well-prepared rock cores. Therefore, compressional wave velocity (Vp) and index parameters such as point load index and porosity are often used to predict the properties of rocks. In this paper, brittleness and other properties, physical and mechanical in type, of 56 Asmari limestones in dry and saturated conditions were analyzed. The rock samples were collected from Khersan 2 dam site. This dam with the height of 240 m is being constructed and located in the Zagros Mountain, in the southwest of Iran. The bedrock and abutments of the dam site consist of Asemari and Gachsaran Formations. In this paper, a practical relation for predicting brittleness and some relations between mechanical and index parameters of the Asmari limestone were established. The presented equation for predicting brittleness based on UCS, Brazilian tensile strength and Vp had high accuracy. Moreover, results showed that the brittleness estimation based on B3 concept (the ratio of multiply compressive strength in tensile strength divided 2) had more accuracy as compared to the B2 (the ratio of compressive strength minus tensile strength to compressive strength plus tensile strength) and B1 (the ratio of compressive strength to tensile strength) concepts.

  19. Experimental and Modelling Investigations of the Coupled Elastoplastic Damage of a Quasi-brittle Rock

    NASA Astrophysics Data System (ADS)

    Zhang, Jiu-Chang

    2018-02-01

    Triaxial compression tests are conducted on a quasi-brittle rock, limestone. The analyses show that elastoplastic deformation is coupled with damage. Based on the experimental investigation, a coupled elastoplastic damage model is developed within the framework of irreversible thermodynamics. The coupling effects between the plastic and damage dissipations are described by introducing an isotropic damage variable into the elastic stiffness and yield criterion. The novelty of the model is in the description of the thermodynamic force associated with damage, which is formulated as a state function of both elastic and plastic strain energies. The latter gives a full consideration on the comprehensive effects of plastic strain and stress changing processes in rock material on the development of damage. The damage criterion and potential are constructed to determine the onset and evolution of damage variable. The return mapping algorithms of the coupled model are deduced for three different inelastic corrections. Comparisons between test data and numerical simulations show that the coupled elastoplastic damage model is capable of describing the main mechanical behaviours of the quasi-brittle rock.

  20. Earthquakes Below the Brittle-Ductile Transition: The Role of Grain Size Assisted Thermal Runaway

    NASA Astrophysics Data System (ADS)

    Thielmann, M.; Duretz, T.

    2017-12-01

    Great earthquakes with magnitudes larger than 8.0 commonly occur in the vicinity of plate boundaries. Most of those earthquakes occur in subduction zones in compressive settings, but others have also been observed to occur on strike slip faults. Fault slip in those earthquakes is on the order of tens of meters, while fault length ranges from 100-1000 km. This implies that a significant slip may have occurred at temperatures and pressures where brittle failure is unlikely and alternative failure mechanisms may have to operate to allow for localized slip. Previous studies have shown that grain size assisted runaway (GSATR) is a viable mechanism to create localized shear zones and possibly also earthquake-like rupture. Here we investigate the potential of this mechanism to extend earthquake rupture to depth below the brittle-ductile transition. To this end, we employ 2D numerical models that couple the evolution of stress, temperature and grain size evolution and systematically explore the parameter space to determine the efficiency of the GSATR mechanism.

  1. Transition from a strong-yet-brittle to a stronger-and-ductile state by size reduction of metallic glasses.

    PubMed

    Jang, Dongchan; Greer, Julia R

    2010-03-01

    Amorphous metallic alloys, or metallic glasses, are lucrative engineering materials owing to their superior mechanical properties such as high strength and large elastic strain. However, their main drawback is their propensity for highly catastrophic failure through rapid shear banding, significantly undercutting their structural applications. Here, we show that when reduced to 100 nm, Zr-based metallic glass nanopillars attain ceramic-like strengths (2.25 GPa) and metal-like ductility (25%) simultaneously. We report separate and distinct critical sizes for maximum strength and for the brittle-to-ductile transition, thereby demonstrating that strength and ability to carry plasticity are decoupled at the nanoscale. A phenomenological model for size dependence and brittle-to-homogeneous deformation is provided.

  2. DbMap: improving database interoperability issues in medical software using a simple, Java-Xml based solution.

    PubMed Central

    Karadimas, H.; Hemery, F.; Roland, P.; Lepage, E.

    2000-01-01

    In medical software development, the use of databases plays a central role. However, most of the databases have heterogeneous encoding and data models. To deal with these variations in the application code directly is error-prone and reduces the potential reuse of the produced software. Several approaches to overcome these limitations have been proposed in the medical database literature, which will be presented. We present a simple solution, based on a Java library, and a central Metadata description file in XML. This development approach presents several benefits in software design and development cycles, the main one being the simplicity in maintenance. PMID:11079915

  3. Structural hierarchies define toughness and defect-tolerance despite simple and mechanically inferior brittle building blocks

    NASA Astrophysics Data System (ADS)

    Sen, Dipanjan; Buehler, Markus J.

    2011-07-01

    Mineralized biological materials such as bone, sea sponges or diatoms provide load-bearing and armor functions and universally feature structural hierarchies from nano to macro. Here we report a systematic investigation of the effect of hierarchical structures on toughness and defect-tolerance based on a single and mechanically inferior brittle base material, silica, using a bottom-up approach rooted in atomistic modeling. Our analysis reveals drastic changes in the material crack-propagation resistance (R-curve) solely due to the introduction of hierarchical structures that also result in a vastly increased toughness and defect-tolerance, enabling stable crack propagation over an extensive range of crack sizes. Over a range of up to four hierarchy levels, we find an exponential increase in the defect-tolerance approaching hundred micrometers without introducing additional mechanisms or materials. This presents a significant departure from the defect-tolerance of the base material, silica, which is brittle and highly sensitive even to extremely small nanometer-scale defects.

  4. Brittle intermetallic compound makes ultrastrong low-density steel with large ductility.

    PubMed

    Kim, Sang-Heon; Kim, Hansoo; Kim, Nack J

    2015-02-05

    Although steel has been the workhorse of the automotive industry since the 1920s, the share by weight of steel and iron in an average light vehicle is now gradually decreasing, from 68.1 per cent in 1995 to 60.1 per cent in 2011 (refs 1, 2). This has been driven by the low strength-to-weight ratio (specific strength) of iron and steel, and the desire to improve such mechanical properties with other materials. Recently, high-aluminium low-density steels have been actively studied as a means of increasing the specific strength of an alloy by reducing its density. But with increasing aluminium content a problem is encountered: brittle intermetallic compounds can form in the resulting alloys, leading to poor ductility. Here we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion. The specific tensile strength and ductility of the developed steel improve on those of the lightest and strongest metallic materials known, titanium alloys. We found that alloying of nickel catalyses the precipitation of nanometre-sized B2 particles in the face-centred cubic matrix of high-aluminium low-density steel during heat treatment of cold-rolled sheet steel. Our results demonstrate how intermetallic compounds can be harnessed in the alloy design of lightweight steels for structural applications and others.

  5. A low-temperature ductile shear zone: The gypsum-dominated western extension of the brittle Fella-Sava Fault, Southern Alps.

    PubMed

    Bartel, Esther Maria; Neubauer, Franz; Heberer, Bianca; Genser, Johann

    2014-12-01

    Based on structural and fabric analyses at variable scales we investigate the evaporitic gypsum-dominated Comeglians-Paularo shear zone in the Southern Alps (Friuli). It represents the lateral western termination of the brittle Fella-Sava Fault. Missing dehydration products of gypsum and the lack of annealing indicate temperatures below 100 °C during development of the shear zone. Despite of such low temperatures the shear zone clearly exhibits mylonitic flow, thus evidencing laterally coeval activity of brittle and viscous deformation. The dominant structures within the gypsum rocks of the Lower Bellerophon Formation are a steeply to gently S-dipping foliation, a subhorizontal stretching lineation and pure shear-dominated porphyroclast systems. A subordinate simple shear component with dextral displacement is indicated by scattered σ-clasts. Both meso- and microscale structures are characteristic of a subsimple shear type of deformation with components of both coaxial and non-coaxial strain. Shortening in a transpressive regime was accommodated by right-lateral displacement and internal pure shear deformation within the Comeglians-Paularo shear zone. The shear zone shows evidence for a combination of two stretching faults, where stretching occurred in the rheologically weaker gypsum member and brittle behavior in enveloping lithologies.

  6. Analytical and Experimental Nanomechanical Approaches to Understanding the Ductile-to-Brittle Transition

    NASA Astrophysics Data System (ADS)

    Hintsala, Eric Daniel

    This dissertation presents progress towards understanding the ductile-to-brittle transition (DBT) using a mixture of nanomechanical experiments and an analytical model. The key concept is dislocation shielding of crack tips, which is occurs due to a dislocation back stress. In order to properly evaluate the role of these interactions, in-situ experiments are ideal by reducing the number of interacting dislocations and allowing direct observation of cracking behavior and the dislocations themselves. First, in-situ transmission electron microscope (TEM) compression experiments of plasma-synthesized silicon nanocubes (NCs) are presented which shows plastic strains greater than 50% in a semi-brittle material. The mechanical properties are discussed and plasticity mechanisms are identified using post-mortem imaging with a combination of dark field and high-resolution imaging. This observations help to develop a back stress model which is used to fit the hardening regime. This represents the first study of its kind where back stresses are used in a discrete manner to match hardening rates. However, the important measurable quantities for evaluating the DBT include fracture toughness values and energetic activation parameters for cracking and plasticity. In order to do this, a new method for doing in-situ fracture experiments is explored. This method is pre-notched three point bending experiments, which were fabricated by focused ion beam (FIB) milling. Two different materials are evaluated: a model ductile material, Nitronic 50, an austenitic steel alloy, and a model brittle material, silicon. These experiments are performed in-situ scanning electron microscope (SEM) and TEM and explore different aspects including electron backscatter diffraction (EBSD) to track deformation in SEM scale experiments, pre-notching using a converged TEM beam to produce sharper notches better replicating natural cracks, etching procedures to reduce residual FIB damage and elevated

  7. Video Image Stabilization and Registration (VISAR) Software

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Two scientists at NASA's Marshall Space Flight Center,atmospheric scientist Paul Meyer and solar physicist Dr. David Hathaway, developed promising new software, called Video Image Stabilization and Registration (VISAR). VISAR may help law enforcement agencies catch criminals by improving the quality of video recorded at crime scenes. In this photograph, the single frame at left, taken at night, was brightened in order to enhance details and reduce noise or snow. To further overcome the video defects in one frame, Law enforcement officials can use VISAR software to add information from multiple frames to reveal a person. Images from less than a second of videotape were added together to create the clarified image at right. VISAR stabilizes camera motion in the horizontal and vertical as well as rotation and zoom effects producing clearer images of moving objects, smoothes jagged edges, enhances still images, and reduces video noise or snow. VISAR could also have applications in medical and meteorological imaging. It could steady images of ultrasounds, which are infamous for their grainy, blurred quality. The software can be used for defense application by improving recornaissance video imagery made by military vehicles, aircraft, and ships traveling in harsh, rugged environments.

  8. Overcoming job stress

    MedlinePlus

    ... medlineplus.gov/ency/patientinstructions/000884.htm Overcoming job stress To use the sharing features on this page, ... stay healthy and feel better. Causes of Job Stress Although the cause of job stress is different ...

  9. Shallow-water brittle stars (Echinodermata: Ophiuroidea) from Araçá Bay (Southeastern Brazil), with spatial distribution considerations.

    PubMed

    Alitto, Renata A S; Bueno, Maristela L; Guilherme, Pablo D B; Di Domenico, Maikon; Christensen, Ana Beardsley; Borges, Michela

    2018-04-05

    The detailed study of arm ossicles, particularly the lateral arm plates, is providing valuable information in the elucidation of ophiuroid taxonomy. The present study describes in detail 16 species of brittle stars from Araçá Bay, Brazil. This information is used to construct the first interactive electronic key, providing a valuable resource for a broad range of researchers. Brittle stars families were divided into three groups based on their spatial distribution: i) infaunal species of intertidal and shallow subtidal belonging to Amphiuridae and Ophiactidae, ii) epizoic species belonging to Amphiuridae, Ophiactidae, and Ophiotrichidae and, iii) epifaunal species of the subtidal belonging to Ophiodermatidae and Hemieuryalidae. In the global context of recent revisions of ophiuroid taxonomy, the present work provides additional characters for use in future phylogenetic studies.

  10. Bridging micro to macroscale fracture properties in highly heterogeneous brittle solids: weak pinning versus fingering

    NASA Astrophysics Data System (ADS)

    Vasoya, Manish; Lazarus, Véronique; Ponson, Laurent

    2016-10-01

    The effect of strong toughness heterogeneities on the macroscopic failure properties of brittle solids is investigated in the context of planar crack propagation. The basic mechanism at play is that the crack is locally slowed down or even trapped when encountering tougher material. The induced front deformation results in a selection of local toughness values that reflect at larger scale on the material resistance. To unravel this complexity and bridge micro to macroscale in failure of strongly heterogeneous media, we propose a homogenization procedure based on the introduction of two complementary macroscopic properties: An apparent toughness defined from the loading required to make the crack propagate and an effective fracture energy defined from the rate of energy released by unit area of crack advance. The relationship between these homogenized properties and the features of the local toughness map is computed using an iterative perturbation method. This approach is applied to a circular crack pinned by a periodic array of obstacles invariant in the radial direction, which gives rise to two distinct propagation regimes: A weak pinning regime where the crack maintains a stationary shape after reaching an equilibrium position and a fingering regime characterized by the continuous growth of localized regions of the fronts while the other parts remain trapped. Our approach successfully bridges micro to macroscopic failure properties in both cases and illustrates how small scale heterogeneities can drastically affect the overall failure response of brittle solids. On a broader perspective, we believe that our approach can be used as a powerful tool for the rational design of heterogeneous brittle solids and interfaces with tailored failure properties.

  11. Theoretical effects of fully ductile versus fully brittle behaviors of bone tissue on the strength of the human proximal femur and vertebral body.

    PubMed

    Nawathe, Shashank; Yang, Haisheng; Fields, Aaron J; Bouxsein, Mary L; Keaveny, Tony M

    2015-05-01

    The influence of the ductility of bone tissue on whole-bone strength represents a fundamental issue of multi-scale biomechanics. To gain insight, we performed a computational study of 16 human proximal femurs and 12 T9 vertebral bodies, comparing the whole-bone strength for the two hypothetical bounding cases of fully brittle versus fully ductile tissue-level failure behaviors, all other factors, including tissue-level elastic modulus and yield stress, held fixed. For each bone, a finite element model was generated (60-82 μm element size; up to 120 million elements) and was virtually loaded in habitual (stance for femur, compression for vertebra) and non-habitual (sideways fall, only for femur) loading modes. Using a geometrically and materially non-linear model, the tissue was assumed to be either fully brittle or fully ductile. We found that, under habitual loading, changing the tissue behavior from fully ductile to fully brittle reduced whole-bone strength by 38.3±2.4% (mean±SD) and 39.4±1.9% for the femur and vertebra, respectively (p=0.39 for site difference). These reductions were remarkably uniform across bones, but (for the femur) were greater for non-habitual (57.1±4.7%) than habitual loading (p<0.001). At overall structural failure, there was 5-10-fold less failed tissue for the fully brittle than fully ductile cases. These theoretical results suggest that the whole-bone strength of the proximal femur and vertebra can vary substantially between fully brittle and fully ductile tissue-level behaviors, an effect that is relatively insensitive to bone morphology but greater for non-habitual loading. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. The Utility of Free Software for Gravity and Magnetic Advanced Data Processing

    NASA Astrophysics Data System (ADS)

    Grandis, Hendra; Dahrin, Darharta

    2017-04-01

    The lack of computational tools, i.e. software, often hinders the proper teaching and application of geophysical data processing in academic institutions in Indonesia. Although there are academic licensing options for commercial software, such options are still way beyond the financial capability of some academic institutions. Academic community members (both lecturers and students) are supposed to be creative and resourceful to overcome such situation. Therefore, capability for writing computer programs or codes is a necessity. However, there are also many computer programs and even software that are freely available on the internet. Generally, the utility of the freely distributed software is limited for demonstration only or for visualizing and exchanging data. The paper discusses the utility of Geosoft’s Oasis Montaj Viewer along with USGS GX programs that are available for free. Useful gravity and magnetic advanced data processing (i.e. gradient calculation, spectral analysis etc.) can be performed “correctly” without any approximation that sometimes leads to dubious results and interpretation.

  13. Brittle deformation and exhumation mechanisms in the core of the Eastern Alps, The Tauern Window

    NASA Astrophysics Data System (ADS)

    Bertrand, Audrey; Garcia, Sebastian; Rosenberg, Claudio

    2010-05-01

    The Tauern Window (TW) is a Tertiary structural and thermal dome located in the core of the Eastern Alpine orogen and in front of the Dolomite indenter. The Penninic basement and cover units within the TW attained their thermal peak about 30 Myr ago (e.g., Selverstone et al., 1992) followed by cooling and exhumation from Early Oligocene to late Miocene time (e.g., Grundmann and Morteani, 1985). Most exhumation was partly accommodated by two normal faults at the western and eastern ends of the TW (Brenner and Katschberg faults, respectively). Although these normal faults are well described in the literature, their roles in the exhumation of the TW are still under debate: Exhumation accommodated primarily by folding and erosion (e.g., Rosenberg et al., 2004) versus exhumation mainly accommodated by Brenner and Katschberg normal faulting (e.g., Selverstone, 1988; Ratschbacher et al., 1989). New fault-slip data from the TW allow us to reconstruct paleostress axes by inversion and to constrain the relative roles of the folding and orogen-parallel extension during the late deformation history of the TW, in the brittle-field. Our results show little evidence of compression and a clear zoning of the paleostress field in the TW. In the central part of the TW, the σ1 direction is sub-horizontal N-S to NE-SW (strike-slip), whereas it is steep in the footwall of the Brenner and the Katschberg normal faults. Local variability of the σ3 direction are observed; indeed, the σ3 direction varies from E-W to WNW-ESE along the Brenner fault, to NW-SE along the Jaufen fault, the inferred southern continuation of the Brenner fault (Schneider et al., this session). Along the Katschberg fault, the σ3 direction is mainly NNW-SSE oriented, which is consistent with extension in front of a triangular dead zone shape induced by the WSW-striking Dolomites indenter. Nearly no evidence of a stress field compatible with upright folding (D2 phase of deformation) was found in the brittle domain

  14. An interactive dynamic analysis and decision support software for MR mammography.

    PubMed

    Ertaş, Gökhan; Gülçür, H Ozcan; Tunaci, Mehtap

    2008-06-01

    A fully automated software is introduced to facilitate MR mammography (MRM) examinations and overcome subjectiveness in diagnosis using normalized maximum intensity-time ratio (nMITR) maps. These maps inherently suppress enhancements due to normal parenchyma and blood vessels that surround lesions and have natural tolerance to small field inhomogeneities and motion artifacts. The classifier embedded within the software is trained with normalized complexity and maximum nMITR of 22 lesions and tested with the features of remaining 22 lesions. Achieved diagnostic performances are 92% sensitivity, 90% specificity, 91% accuracy, 92% positive predictive value and 90% negative predictive value. DynaMammoAnalyst shortens evaluation time considerably and reduces inter and intra-observer variability by providing decision support.

  15. The role of post-failure brittleness of soft rocks in the assessment of stability of intact masses: FDEM technique applications to ideal problems

    NASA Astrophysics Data System (ADS)

    Lollino, Piernicola; Andriani, Gioacchino Francesco; Fazio, Nunzio Luciano; Perrotti, Michele

    2016-04-01

    Strain-softening under low confinement stress, i.e. the drop of strength that occurs in the post-failure stage, represents a key factor of the stress-strain behavior of rocks. However, this feature of the rock behavior is generally underestimated or even neglected in the assessment of boundary value problems of intact soft rock masses. This is typically the case when the stability of intact rock masses is treated by means of limit equilibrium or finite element analyses, for which rigid-plastic or elastic perfectly-plastic constitutive models, generally implementing peak strength conditions of the rock, are respectively used. In fact, the aforementioned numerical techniques are characterized by intrinsic limitations that do not allow to account for material brittleness, either for the method assumptions or due to numerical stability problems, as for the case of the finite element method, unless sophisticated regularization techniques are implemented. However, for those problems that concern the stability of intact soft rock masses at low stress levels, as for example the stability of shallow underground caves or that of rock slopes, the brittle stress-strain response of rock in the post-failure stage cannot be disregarded due to the risk of overestimation of the stability factor. This work is aimed at highlighting the role of post-peak brittleness of soft rocks in the analysis of specific ideal problems by means of the use of a hybrid finite-discrete element technique (FDEM) that allows for the simulation of the rock stress-strain brittle behavior in a proper way. In particular, the stability of two ideal cases, represented by a shallow underground rectangular cave and a vertical cliff, has been analyzed by implementing a post-peak brittle behavior of the rock and the comparison with a non-brittle response of the rock mass is also explored. To this purpose, the mechanical behavior of a soft calcarenite belonging to the Calcarenite di Gravina formation, extensively

  16. Tube pumices as strain markers of the ductile-brittle transition during magma fragmentation

    NASA Astrophysics Data System (ADS)

    Martí, J.; Soriano, C.; Dingwell, D. B.

    1999-12-01

    Magma fragmentation-the process by which relatively slow-moving magma transforms into a violent gas flow carrying fragments of magma-is the defining feature of explosive volcanism. Yet of all the processes involved in explosively erupting systems, fragmentation is possibly the least understood. Several theoretical and laboratory studies on magma degassing and fragmentation have produced a general picture of the sequence of events leading to the fragmentation of silicic magma. But there remains a debate over whether magma fragmentation is a consequence of the textural evolution of magma to a foamed state where disintegration of walls separating bubbles becomes inevitable due to a foam-collapse criterion, or whether magma is fragmented purely by stresses that exceed its tensile strength. Here we show that tube pumice-where extreme bubble elongation is observed-is a well-preserved magmatic `strain marker' of the stress state immediately before and during fragmentation. Structural elements in the pumice record the evolution of the magma's mechanical response from viscous behaviour (foaming and foam elongation) through the plastic or viscoelastic stage, and finally to brittle behaviour. These observations directly support the hypothesis that fragmentation occurs when magma undergoes a ductile-brittle transition and stresses exceed the magma's tensile strength.

  17. A META-COMPOSITE SOFTWARE DEVELOPMENT APPROACH FOR TRANSLATIONAL RESEARCH

    PubMed Central

    Sadasivam, Rajani S.; Tanik, Murat M.

    2013-01-01

    Translational researchers conduct research in a highly data-intensive and continuously changing environment and need to use multiple, disparate tools to achieve their goals. These researchers would greatly benefit from meta-composite software development or the ability to continuously compose and recompose tools together in response to their ever-changing needs. However, the available tools are largely disconnected, and current software approaches are inefficient and ineffective in their support for meta-composite software development. Building on the composite services development approach, the de facto standard for developing integrated software systems, we propose a concept-map and agent-based meta-composite software development approach. A crucial step in composite services development is the modeling of users’ needs as processes, which can then be specified in an executable format for system composition. We have two key innovations. First, our approach allows researchers (who understand their needs best) instead of technicians to take a leadership role in the development of process models, reducing inefficiencies and errors. A second innovation is that our approach also allows for modeling of complex user interactions as part of the process, overcoming the technical limitations of current tools. We demonstrate the feasibility of our approach using a real-world translational research use case. We also present results of usability studies evaluating our approach for future refinements. PMID:23504436

  18. A meta-composite software development approach for translational research.

    PubMed

    Sadasivam, Rajani S; Tanik, Murat M

    2013-06-01

    Translational researchers conduct research in a highly data-intensive and continuously changing environment and need to use multiple, disparate tools to achieve their goals. These researchers would greatly benefit from meta-composite software development or the ability to continuously compose and recompose tools together in response to their ever-changing needs. However, the available tools are largely disconnected, and current software approaches are inefficient and ineffective in their support for meta-composite software development. Building on the composite services development approach, the de facto standard for developing integrated software systems, we propose a concept-map and agent-based meta-composite software development approach. A crucial step in composite services development is the modeling of users' needs as processes, which can then be specified in an executable format for system composition. We have two key innovations. First, our approach allows researchers (who understand their needs best) instead of technicians to take a leadership role in the development of process models, reducing inefficiencies and errors. A second innovation is that our approach also allows for modeling of complex user interactions as part of the process, overcoming the technical limitations of current tools. We demonstrate the feasibility of our approach using a real-world translational research use case. We also present results of usability studies evaluating our approach for future refinements.

  19. Migrating swarms of brittle-failure earthquakes in the lower crust beneath Mammoth Mountain, California

    USGS Publications Warehouse

    Shelly, D.R.; Hill, D.P.

    2011-01-01

    Brittle-failure earthquakes in the lower crust, where high pressures and temperatures would typically promote ductile deformation, are relatively rare but occasionally observed beneath active volcanic centers. Where they occur, these earthquakes provide a rare opportunity to observe volcanic processes in the lower crust, such as fluid injection and migration, which may induce brittle faulting under these conditions. Here, we examine recent short-duration earthquake swarms deep beneath the southwestern margin of Long Valley Caldera, near Mammoth Mountain. We focus in particular on a swarm that occurred September 29-30, 2009. To maximally illuminate the spatial-temporal progression, we supplement catalog events by detecting additional small events with similar waveforms in the continuous data, achieving up to a 10-fold increase in the number of locatable events. We then relocate all events, using cross-correlation and a double-difference algorithm. We find that the 2009 swarm exhibits systematically decelerating upward migration, with hypocenters shallowing from 21 to 19 km depth over approximately 12 hours. This relatively high migration rate, combined with a modest maximum magnitude of 1.4 in this swarm, suggests the trigger might be ascending CO2 released from underlying magma.

  20. Bottom-up modeling of damage in heterogeneous quasi-brittle solids

    NASA Astrophysics Data System (ADS)

    Rinaldi, Antonio

    2013-03-01

    The theoretical modeling of multisite cracking in quasi-brittle materials is a complex damage problem, hard to model with traditional methods of fracture mechanics due to its multiscale nature and to strain localization induced by microcracks interaction. Macroscale "effective" elastic models can be conveniently applied if a suitable Helmholtz free energy function is identified for a given material scenario. Del Piero and Truskinovsky (Continuum Mech Thermodyn 21:141-171, 2009), among other authors, investigated macroscale continuum solutions capable of matching—in a top-down view—the phenomenology of the damage process for quasi-brittle materials regardless of the microstructure. On the contrary, this paper features a physically based solution method that starts from the direct consideration of the microscale properties and, in a bottom-up view, recovers a continuum elastic description. This procedure is illustrated for a simple one-dimensional problem of this type, a bar modeled stretched by an axial displacement, where the bar is modeled as a 2D random lattice of decohesive spring elements of finite strength. The (microscale) data from simulations are used to identify the "exact" (macro-) damage parameter and to build up the (macro-) Helmholtz function for the equivalent elastic model, bridging the macroscale approach by Del Piero and Truskinovsky. The elastic approach, coupled with microstructural knowledge, becomes a more powerful tool to reproduce a broad class of macroscopic material responses by changing the convexity-concavity of the Helmholtz energy. The analysis points out that mean-field statistics are appropriate prior to damage localization but max-field statistics are better suited in the softening regime up to failure, where microstrain fluctuation needs to be incorporated in the continuum model. This observation is of consequence to revise mean-field damage models from literature and to calibrate Nth gradient continuum models.

  1. Fracture mechanisms in multilayer phosphorene assemblies: from brittle to ductile.

    PubMed

    Liu, Ning; Hong, Jiawang; Zeng, Xiaowei; Pidaparti, Ramana; Wang, Xianqiao

    2017-05-24

    The outstanding mechanical performance of nacre has stimulated numerous studies on the design of artificial nacres. Phosphorene, a new two-dimensional (2D) material, has a crystalline in-plane structure and non-bonded interaction between adjacent flakes. Therefore, multi-layer phosphorene assemblies (MLPs), in which phosphorene flakes are piled up in a staggered manner, may exhibit outstanding mechanical performance, especially exceptional toughness. Therefore, molecular dynamics simulations are performed to study the dependence of the mechanical properties on the overlap distance between adjacent phosphorene layers and the number of phosphorene flakes per layer. The results indicate that when the flake number is equal to 1, a transition of fracture patterns is observed by increasing the overlap distance, from a ductile failure controlled by interfacial friction to a brittle failure dominated by the breakage of covalent bonds inside phosphorene flakes. Moreover, the failure pattern can be tuned by changing the number of flakes in each phosphorene layer. The results imply that the ultimate strength follows a power law with the exponent -0.5 in terms of the flake number, which is in good agreement with our analytical model. Furthermore, the flake number in each phosphorene layer is optimized as 2 when the temperature is 1 K in order to potentially achieve both high toughness and strength. Moreover, our results regarding the relations between mechanical performance and overlap distance can be explained well using a shear-lag model. However, it should be pointed out that increasing the temperature of MLPs could cause the transition of fracture patterns from ductile to brittle. Therefore, the optimal flake number depends heavily on temperature to achieve both its outstanding strength and toughness. Overall, our findings unveil the fundamental mechanism at the nanoscale for MLPs as well as provide a method to design phosphorene-based structures with targeted properties

  2. Temper Brittleness and Its Relation to the Heat Treatment of Ordnance Materiel

    DTIC Science & Technology

    1945-06-20

    obtained in such bainitic steels only when they are tempered A to relatively lor hardnesees (approximately 200 VM or 85,000 psi yield stren-X.th). g...iiuzn, and! nickel inCtease the tVenC-ency f or temp er brittle- ness to occur as well as its severity w-hen it does occuir. Steels of equal...these. elements also lower the impact pro-perties of the uneirnbrittleO. ste’el. in low and. medlwa alloy steels molybd~entiu is so effective in

  3. De Novo Adult Transcriptomes of Two European Brittle Stars: Spotlight on Opsin-Based Photoreception

    PubMed Central

    Mallefet, Jérôme; Flammang, Patrick

    2016-01-01

    Next generation sequencing (NGS) technology allows to obtain a deeper and more complete view of transcriptomes. For non-model or emerging model marine organisms, NGS technologies offer a great opportunity for rapid access to genetic information. In this study, paired-end Illumina HiSeqTM technology has been employed to analyse transcriptomes from the arm tissues of two European brittle star species, Amphiura filiformis and Ophiopsila aranea. About 48 million Illumina reads were generated and 136,387 total unigenes were predicted from A. filiformis arm tissues. For O. aranea arm tissues, about 47 million reads were generated and 123,324 total unigenes were obtained. Twenty-four percent of the total unigenes from A. filiformis show significant matches with sequences present in reference online databases, whereas, for O. aranea, this percentage amounts to 23%. In both species, around 50% of the predicted annotated unigenes were significantly similar to transcripts from the purple sea urchin, the closest species to date that has undergone complete genome sequencing and annotation. GO, COG and KEGG analyses were performed on predicted brittle star unigenes. We focused our analyses on the phototransduction actors involved in light perception. Firstly, two new echinoderm opsins were identified in O. aranea: one rhabdomeric opsin (homologous to vertebrate melanopsin) and one RGR opsin. The RGR-opsin is supposed to be involved in retinal regeneration while the r-opsin is suspected to play a role in visual-like behaviour. Secondly, potential phototransduction actors were identified in both transcriptomes using the fly (rhabdomeric) and mammal (ciliary) classical phototransduction pathways as references. Finally, the sensitivity of O.aranea to monochromatic light was investigated to complement data available for A. filiformis. The presence of microlens-like structures at the surface of dorsal arm plate of O. aranea could potentially explain phototactic behaviour differences

  4. Initiation of a Low-Angle Normal Fault Active Across the Upper Brittle-Plastic Transition, Chemehuevi Mountains, CA

    NASA Astrophysics Data System (ADS)

    LaForge, J.; John, B. E.; Grimes, C. B.; Stunitz, H.; Heilbronner, R.

    2016-12-01

    The Chemehuevi detachment fault system, part of the regionally developed Colorado River extensional corridor, hosts exceptional exposures of a denuded fault system related to Miocene extension. Here, we characterize the early history of extension associated with a small slip (1-2 km) low-angle normal fault, the Mohave Wash fault (MWF), initially active across the brittle-plastic transition. Strain localized in three principal ways across the 23-km down-dip exposure (T <150° to >400°C): a brittle fault zone, localized, disseminated quartz mylonites, and syntectonic dikes hosting mylonitic fabrics. Brittle deformation in these crystalline rocks was concentrated into a 10-62-m thick brittle fault zone hosting localized, unmineralized to chlorite-epidote-quartz mineralized zones of cataclasite series fault rocks ≤3 m thick and rare pseudotachylite. Mylonitic deformation played an increased role in deformation down dip (NE), with mylonites increasing in quantity and average thickness. At shallow structural levels, footwall mylonites are absent; at 9-18 km down dip, cm-scale quartz mylonites are common; ≥18 km down dip, meter-scale syntectonic intermediate-felsic dikes are mylonitic, are attenuated into parallelism with the MWF, and host well-developed L-S fabric; 23 km down dip, the footwall hosts meter-thick zones of disseminated mylonitic quartz of varying intensities. These mylonites host microstructures that record progressively higher deformation temperature down dip, with dislocation-creep in quartz indicative of T of 280-400°C to ≥500°C, and diffusion creep with grain boundary sliding in dikes suggestive of even higher T deformation. Dike emplacement in the system is syntectonic with MWF slip; mafic-intermediate composition dikes intruded damage zone fractures and cataclasites, and were in turn fractured; Pb/U zircon ages of intermediate-felsic dikes range from ca. 1.5 ± 1 Ma to 3.8 ± 1 Ma after the onset of regional extension, but predate rapid slip

  5. Slow Crack Growth Analysis of Brittle Materials with Finite Thickness Subjected to Constant Stress-Rate Flexural Loading

    NASA Technical Reports Server (NTRS)

    Chio, S. R.; Gyekenyesi, J. P.

    1999-01-01

    A two-dimensional, numerical analysis of slow crack growth (SCG) was performed for brittle materials with finite thickness subjected to constant stress-rate ("dynamic fatigue") loading in flexure. The numerical solution showed that the conventional, simple, one-dimensional analytical solution can be used with a maximum error of about 5% in determining the SCG parameters of a brittle material with the conditions of a normalized thickness (a ratio of specimen thickness to initial crack size) T > 3.3 and of a SCG parameter n > 10. The change in crack shape from semicircular to elliptical configurations was significant particularly at both low stress rate and low T, attributed to predominant difference in stress intensity factor along the crack front. The numerical solution of SCG parameters was supported within the experimental range by the data obtained from constant stress-rate flexural testing for soda-lime glass microslides at ambient temperature.

  6. Contact mechanics at nanometric scale using nanoindentation technique for brittle and ductile materials.

    PubMed

    Roa, J J; Rayon, E; Morales, M; Segarra, M

    2012-06-01

    In the last years, Nanoindentation or Instrumented Indentation Technique has become a powerful tool to study the mechanical properties at micro/nanometric scale (commonly known as hardness, elastic modulus and the stress-strain curve). In this review, the different contact mechanisms (elastic and elasto-plastic) are discussed, the recent patents for each mechanism (elastic and elasto-plastic) are summarized in detail, and the basic equations employed to know the mechanical behaviour for brittle and ductile materials are described.

  7. Brittle Fracture In Disordered Media: A Unified Theory

    NASA Astrophysics Data System (ADS)

    Shekhawat, Ashivni; Zapperi, Stefano; Sethna, James

    2013-03-01

    We present a unified theory of fracture in disordered brittle media that reconciles apparently conflicting results reported in the literature, as well as several experiments on materials ranging from granite to bones. Our renormalization group based approach yields a phase diagram in which the percolation fixed point, expected for infinite disorder, is unstable for finite disorder and flows to a zero-disorder nucleation-type fixed point, thus showing that fracture has mixed first order and continuous character. In a region of intermediate disorder and finite system sizes, we predict a crossover with mean-field avalanche scaling. We discuss intriguing connections to other phenomena where critical scaling is only observed in finite size systems and disappears in the thermodynamic limit. We present a numerical validation of our theoretical results. We acknowledge support from DOE- BES DE-FG02-07ER46393, ERC-AdG-2011 SIZEFFECT, and the NSF through TeraGrid by LONI under grant TG-DMR100025.

  8. CATS, continuous automated testing of seismological, hydroacoustic, and infrasound (SHI) processing software.

    NASA Astrophysics Data System (ADS)

    Brouwer, Albert; Brown, David; Tomuta, Elena

    2017-04-01

    To detect nuclear explosions, waveform data from over 240 SHI stations world-wide flows into the International Data Centre (IDC) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), located in Vienna, Austria. A complex pipeline of software applications processes this data in numerous ways to form event hypotheses. The software codebase comprises over 2 million lines of code, reflects decades of development, and is subject to frequent enhancement and revision. Since processing must run continuously and reliably, software changes are subjected to thorough testing before being put into production. To overcome the limitations and cost of manual testing, the Continuous Automated Testing System (CATS) has been created. CATS provides an isolated replica of the IDC processing environment, and is able to build and test different versions of the pipeline software directly from code repositories that are placed under strict configuration control. Test jobs are scheduled automatically when code repository commits are made. Regressions are reported. We present the CATS design choices and test methods. Particular attention is paid to how the system accommodates the individual testing of strongly interacting software components that lack test instrumentation.

  9. Fabric controls on the brittle failure of folded gneiss and schist

    NASA Astrophysics Data System (ADS)

    Agliardi, Federico; Zanchetta, Stefano; Crosta, Giovanni B.

    2014-12-01

    We experimentally studied the brittle failure behaviour of folded gneiss and schist. Rock fabric and petrography were characterised by meso-structural analyses, optical microscopy, X-ray diffraction, and SEM imaging. Uniaxial compression, triaxial compression and indirect tension laboratory tests were performed to characterise their strength and stress-strain behaviour. Fracture patterns generated in compression were resolved in 3D through X-ray computed tomography at different resolutions (30 to 625 μm). Uniaxial compression tests revealed relatively low and scattered values of unconfined compressive strength (UCS) and Young's modulus, with no obvious relationships with the orientation of foliation. Samples systematically failed in four brittle modes, involving different combinations of shear fractures along foliation or parallel to fold axial planes, or the development of cm-scale shear zones. Fracture quantification and microstructural analysis show that different failure modes occur depending on the mutual geometrical arrangement and degree of involvement of two distinct physical anisotropies, i.e. the foliation and the fold axial planes. The Axial Plane Anisotropy (APA) is related to micro-scale grain size reduction and shape preferred orientation within quartz-rich domains, and to mechanical rotation or initial crenulation cleavage within phyllosilicate-rich domains at fold hinge zones. In quartz-rich rocks (gneiss), fracture propagation through quartz aggregates forming the APA corresponds to higher fracture energy and strength than found for fracture through phyllosilicate-rich domains. This results in a strong dependence of strength on the failure mode. Conversely, in phyllosilicate-rich rocks (schist), all the failure modes are dominated by the strength of phyllosilicates, resulting in a sharp reduction of strength anisotropy.

  10. Late Pan-African and early Mesozoic brittle compressions in East and Central Africa: lithospheric deformation within the Congo-Tanzania Cratonic area

    NASA Astrophysics Data System (ADS)

    Delvaux, D.; Kipata, M. L.; Macheyeki, A. S.

    2012-04-01

    Tectonic reconstructions leading to the formation of the Central-African part of Gondwana have so far not much taken into account constraints provided by the evolution of brittle structures and related stress field. This is largely because little is known on continental brittle deformation in Equatorial Africa before the onset of the Mesozoic Central-African and Late Cenozoic East-African rifts. We present a synthesis of fault-kinematic data and paleostress inversion results from field surveys covering parts of Tanzania, Zambia and the Democratic Republic of Congo. It is based on investigations along the eastern margin of the Tanzanian craton, in the Ubendian belt between the Tanzanian craton and Bangweulu block, in the Lufilian Arc between the Kalahari and Congo cratons and along the Congo intracratonic basin. Paleostress tensors were computed for a substantial database by interactive stress tensor inversion and data subset separation, and the relative succession of major brittle events established. Two of them appear to be of regional importance and could be traced from one region to the other. The oldest one is the first brittle event recorded after the paroxysm of the Terminal Pan-African event that led to the amalgamation Gondwana at the Precambrian-Cambrian transition. It is related to compressional deformation with horizontal stress trajectories fluctuating from an E-W compression in Central Tanzania to NE-SW in the Ubende belt and Lufilian Arc. The second event is a transpressional inversion with a consistent NW-SE compression that we relate to the far-field effects of the active margin south of Gondwana during the late Triassic - early Jurassic.

  11. Getting around when you're round: quantitative analysis of the locomotion of the blunt-spined brittle star, Ophiocoma echinata.

    PubMed

    Astley, Henry C

    2012-06-01

    Brittle stars (Ophiuroidea, Echinodermata) are pentaradially symmetrical echinoderms that use five multi-jointed limbs to locomote along the seafloor. Prior qualitative descriptions have claimed coordinated movements of the limbs in a manner similar to tetrapod vertebrates, but this has not been evaluated quantitatively. It is uncertain whether the ring-shaped nervous system, which lacks an anatomically defined anterior, is capable of generating rhythmic coordinated movements of multiple limbs. This study tested whether brittle stars possess distinct locomotor modes with strong inter-limb coordination as seen in limbed animals in other phyla (e.g. tetrapods and arthropods), or instead move each limb independently according to local sensory feedback. Limb tips and the body disk were digitized for 56 cycles from 13 individuals moving across sand. Despite their pentaradial anatomy, all individuals were functionally bilateral, moving along the axis of a central limb via synchronous motions of contralateral limbs (±~13% phase lag). Two locomotor modes were observed, distinguishable mainly by whether the central limb was directed forwards or backwards. Turning was accomplished without rotation of the body disk by defining a different limb as the center limb and shifting other limb identities correspondingly, and then continuing locomotion in the direction of the newly defined anterior. These observations support the hypothesis that, in spite of their radial body plan, brittle stars employ coordinated, bilaterally symmetrical locomotion.

  12. The study on network security based on software engineering

    NASA Astrophysics Data System (ADS)

    Jia, Shande; Ao, Qian

    2012-04-01

    Developing a SP is a sensitive task because the SP itself can lead to security weaknesses if it is not conform to the security properties. Hence, appropriate techniques are necessary to overcome such problems. These techniques must accompany the policy throughout its deployment phases. The main contribution of this paper is then, the proposition of three of these activities: validation, test and multi-SP conflict management. Our techniques are inspired by the well established techniques of the software engineering for which we have found some similarities with the security domain.

  13. A pulse-shaping technique to investigate the behaviour of brittle materials subjected to plate-impact tests.

    PubMed

    Forquin, Pascal; Zinszner, Jean-Luc

    2017-01-28

    Owing to their significant hardness and compressive strengths, ceramic materials are widely employed for use with protective systems subjected to high-velocity impact loadings. Therefore, their mechanical behaviour along with damage mechanisms need to be significantly investigated as a function of loading rates. However, the classical plate-impact testing procedures produce shock loadings in the brittle sample material which cause unrealistic levels of loading rates. Additionally, high-pulsed power techniques and/or functionally graded materials used as flyer plates to smooth the loading pulse remain costly, and are generally difficult to implement. In this study, a shockless plate-impact technique based on the use of either a wavy-machined flyer plate or buffer plate that can be produced by chip-forming is proposed. A series of numerical simulations using an explicit transient dynamic finite-element code have been performed to design and validate the experimental testing configuration. The calculations, conducted in two-dimensional (2D) plane-strain or in 2D axisymmetric modes, prove that the 'wavy' contact surface will produce a pulse-shaping effect, whereas the buffer plate will produce a homogenizing effect of the stress field along the transverse direction of the sample. In addition, 'wavy-shape' geometries of different sizes provide an easy way to change the level of loading rate and rise time in an experimentally tested ceramic specimen. Finally, when a shockless compression loading method is applied to the sample, a Lagrangian analysis of data is made possible by considering an assemblage of ceramic plates of different thicknesses in the target, so the axial stress-strain response of the brittle sample material can be provided.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'. © 2016 The Author(s).

  14. A pulse-shaping technique to investigate the behaviour of brittle materials subjected to plate-impact tests

    NASA Astrophysics Data System (ADS)

    Forquin, Pascal; Zinszner, Jean-Luc

    2017-01-01

    Owing to their significant hardness and compressive strengths, ceramic materials are widely employed for use with protective systems subjected to high-velocity impact loadings. Therefore, their mechanical behaviour along with damage mechanisms need to be significantly investigated as a function of loading rates. However, the classical plate-impact testing procedures produce shock loadings in the brittle sample material which cause unrealistic levels of loading rates. Additionally, high-pulsed power techniques and/or functionally graded materials used as flyer plates to smooth the loading pulse remain costly, and are generally difficult to implement. In this study, a shockless plate-impact technique based on the use of either a wavy-machined flyer plate or buffer plate that can be produced by chip-forming is proposed. A series of numerical simulations using an explicit transient dynamic finite-element code have been performed to design and validate the experimental testing configuration. The calculations, conducted in two-dimensional (2D) plane-strain or in 2D axisymmetric modes, prove that the `wavy' contact surface will produce a pulse-shaping effect, whereas the buffer plate will produce a homogenizing effect of the stress field along the transverse direction of the sample. In addition, `wavy-shape' geometries of different sizes provide an easy way to change the level of loading rate and rise time in an experimentally tested ceramic specimen. Finally, when a shockless compression loading method is applied to the sample, a Lagrangian analysis of data is made possible by considering an assemblage of ceramic plates of different thicknesses in the target, so the axial stress-strain response of the brittle sample material can be provided. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

  15. New perspectives on the transition between discrete fracture, fragmentation, and pulverization during brittle failure of rocks

    NASA Astrophysics Data System (ADS)

    Griffith, W. A.; Ghaffari, H.; Barber, T. J.; Borjas, C.

    2015-12-01

    The motions of Earth's tectonic plates are typically measured in millimeters to tens of centimeters per year, seemingly confirming the generally-held view that tectonic processes are slow, and have been throughout Earth's history. In line with this perspective, the vast majority of laboratory rock mechanics research focused on failure in the brittle regime has been limited to experiments utilizing slow loading rates. On the other hand, many natural processes that pose significant risk for humans (e.g., earthquakes and extraterrestrial impacts), as well as risks associated with human activities (blow-outs, explosions, mining and mine failures, projectile penetration), occur at rates that are hundreds to thousands of times faster than those typically simulated in the laboratory. Little experimental data exists to confirm or calibrate theoretical models explaining the connection between these dramatic events and the pulverized rocks found in fault zones, impacts, or explosions; however the experimental data that does exist is thought-provoking: At the earth's surface, the process of brittle fracture passes through a critical transition in rocks at high strain rates (101-103s-1) between regimes of discrete fracture and distributed fragmentation, accompanied by a dramatic increase in strength. Previous experimental works on this topic have focused on key thresholds (e.g., peak stress, peak strain, average strain rate) that define this transition, but more recent work suggests that this transition is more fundamentally dependent on characteristics (e.g., shape) of the loading pulse and related microcrack dynamics, perhaps explaining why for different lithologies different thresholds more effectively define the pulverization transition. In this presentation we summarize some of our work focused on this transition, including the evolution of individual defects at the microscopic, microsecond scale and the energy budget associated with the brittle fragmentation process as a

  16. Theory of friction based on brittle fracture

    USGS Publications Warehouse

    Byerlee, J.D.

    1967-01-01

    A theory of friction is presented that may be more applicable to geologic materials than the classic Bowden and Tabor theory. In the model, surfaces touch at the peaks of asperities and sliding occurs when the asperities fail by brittle fracture. The coefficient of friction, ??, was calculated from the strength of asperities of certain ideal shapes; for cone-shaped asperities, ?? is about 0.1 and for wedge-shaped asperities, ?? is about 0.15. For actual situations which seem close to the ideal model, observed ?? was found to be very close to 0.1, even for materials such as quartz and calcite with widely differing strengths. If surface forces are present, the theory predicts that ?? should decrease with load and that it should be higher in a vacuum than in air. In the presence of a fluid film between sliding surfaces, ?? should depend on the area of the surfaces in contact. Both effects are observed. The character of wear particles produced during sliding and the way in which ?? depends on normal load, roughness, and environment lend further support to the model of friction presented here. ?? 1967 The American Institute of Physics.

  17. An Experimental Study of the Fracture Coalescence Behaviour of Brittle Sandstone Specimens Containing Three Fissures

    NASA Astrophysics Data System (ADS)

    Yang, S. Q.; Yang, D. S.; Jing, H. W.; Li, Y. H.; Wang, S. Y.

    2012-07-01

    To analyse the fracture coalescence behaviour of rock, rectangular prismatic sandstone specimens (80 × 160 × 30 mm in size) containing three fissures were tested under uniaxial compression. The strength and deformation behaviours of the specimens are first analysed by investigating the effects of the ligament angle β2 on the peak strength, peak strain and crack initiation stress of the specimens. To confirm the sequence of crack coalescence, a photographic monitoring technique is used throughout the entire period of deformation. Based on the results, the relationship between the real-time crack coalescence process and the axial stress-strain curve of brittle sandstone specimens is also developed, and this relationship can be used to evaluate the macroscopic deformation characteristics of pre-cracked rock. The equivalent strain evolution fields of the specimen, with α = β1 = 45° and β2 = 90°, are obtained using the digital image correlation technique and show good agreement with the experimental results of pre-cracked brittle sandstone. These experimental results are expected to improve the understanding of fracture mechanisms and be used in rock engineering with intermittent structures, such as deep underground excavated tunnels.

  18. Modeling failure in brittle porous ceramics

    NASA Astrophysics Data System (ADS)

    Keles, Ozgur

    Brittle porous materials (BPMs) are used for battery, fuel cell, catalyst, membrane, filter, bone graft, and pharmacy applications due to the multi-functionality of their underlying porosity. However, in spite of its technological benefits the effects of porosity on BPM fracture strength and Weibull statistics are not fully understood--limiting a wider use. In this context, classical fracture mechanics was combined with two-dimensional finite element simulations not only to account for pore-pore stress interactions, but also to numerically quantify the relationship between the local pore volume fraction and fracture statistics. Simulations show that even the microstructures with the same porosity level and size of pores differ substantially in fracture strength. The maximum reliability of BPMs was shown to be limited by the underlying pore--pore interactions. Fracture strength of BMPs decreases at a faster rate under biaxial loading than under uniaxial loading. Three different types of deviation from classic Weibull behavior are identified: P-type corresponding to a positive lower tail deviation, N-type corresponding to a negative lower tail deviation, and S-type corresponding to both positive upper and lower tail deviations. Pore-pore interactions result in either P-type or N-type deviation in the limit of low porosity, whereas S-type behavior occurs when clusters of low and high fracture strengths coexist in a fracture data.

  19. Elastic geobarometry and the role of brittle failure on pressure release

    NASA Astrophysics Data System (ADS)

    Mazzucchelli, Mattia Luca; Angel, Ross John; Rustioni, Greta; Milani, Sula; Nimis, Paolo; Chiara Domeneghetti, Maria; Marone, Federica; Harris, Jeff W.; Nestola, Fabrizio; Alvaro, Matteo

    2016-04-01

    Mineral inclusions trapped in their hosts can provide fundamental information about geological processes. Recent developments in elastic geobarometry, for example, allow the retrieval of encapsulation pressures for host-inclusion pairs. In principle this method can be applied to any mineral-mineral pair so long as both the residual pressure on an inclusion (Pinc), and the equations of state for both host and inclusion are either known or determined (Angel et al., 2015). However, Angel et al. (2014) outlined some boundary conditions, one of which was that deformation in the host-inclusion pair has to be purely elastic. Thus this caveat would exclude from analysis all the inclusions that are surrounded by cracks, indicative of brittle deformation, which may result in partial or complete release of the Pinc. If however the effects of cracks surrounding trapped mineral inclusions could be quantitatively modelled, then the applicability of "elastic" geobarometry might be extended to a much larger number of inclusion-host pairs. We report the results of a pilot experiment in which the stress states (i.e. the residual pressure) have been determined for 10 olivine inclusions still entrapped in 5 diamonds. Inclusion pressures were determined from the unit-cell volumes of the olivines measured in-situ in the diamonds by X-ray diffraction. The olivine equations of state were determined from the olivine compositions by in-situ X-ray structure refinement. Values of Pinc range from 0.19 to 0.53 GPa. In order to quantify the degree of brittle failure surrounding the inclusions, the same set of samples were also investigated by synchrotron X-ray micro-tomography (SRXTM at TOMCAT, Swiss LightSource). Preliminary results showed that at the spatial resolution of our experiments (pixel size of 0.34μm), 90% of the inclusions trapped in our set of diamonds were surrounded by cracks. The volume of the cracks has been determined from 3D reconstruction with an accuracy of about 4%. Our

  20. Brittle/Ductile deformation at depth during continental crust eclogitization (Mont-Emilius klippe, Western Internal Alps).

    NASA Astrophysics Data System (ADS)

    Hertgen, Solenn; Yamato, Philippe; Morales, Luiz; Angiboust, Samuel

    2016-04-01

    Eclogitic rocks are important for understanding tectonics at large scale as they provide key constraints on both the evolution (P-T-t-ɛ paths) and the deformation modes of the crust along the subduction interface. We herein focus our study on eclogitized mafic dykes remnants exposed within granulites from the continental basement silver of the Mt. Emilius klippe (Western Internal Alps, Italy). These eclogites exhibit highly deformed garnetite and clinopyroxenite levels. In some places, these rocks with a ± mylonitic aspect can be found as clasts within meter-thick brecciated fault rocks formed close to metamorphic peak conditions in eclogite facies. Especially, the garnet-rich levels tend to behave in a brittle fashion while deformation within clinopyroxene-rich levels is mostly accommodated by creep. This is evidenced by the presence of elongated grains, subgrain boundaries and intense grain size reduction close to rigid garnets. Crystallographic preferred orientation (CPO) measurements in garnets indicate a quasi-random distribution. In most of the clinopyroxenes levels nevertheless, the CPO is relatively strong, with multiples of uniform distribution varying from 4 to 5.5 (value of 1 is random texture). This CPO is characterized by a strong alignment of poles (001) parallel to the lineation and (100) and [010] distributed along girdles cross-cutting the foliation plane. Our study thus attests that the materials along the subduction interface at P~2.0-2.5 GPa and T~500-550°C can locally be brittle where deformation is classically envisioned as ductile. In addition to this deformation analysis, we present a petrological study of these eclogites, from the outcrop to the microscopic scale, tracking the chemical evolution associated to the observed deformation. Based on all these data, we finally propose a tectono-metamorphic history for these rocks allowing to explain the co-existence of ductile and brittle features developed in the same metamorphic facies, and

  1. Software-aided automatic laser optoporation and transfection of cells

    PubMed Central

    Georg Breunig, Hans; Uchugonova, Aisada; Batista, Ana; König, Karsten

    2015-01-01

    Optoporation, the permeabilization of a cell membrane by laser pulses, has emerged as a powerful non-invasive and highly efficient technique to induce transfection of cells. However, the usual tedious manual targeting of individual cells significantly limits the addressable cell number. To overcome this limitation, we present an experimental setup with custom-made software control, for computer-automated cell optoporation. The software evaluates the image contrast of cell contours, automatically designates cell locations for laser illumination, centres those locations in the laser focus, and executes the illumination. By software-controlled meandering of the sample stage, in principle all cells in a typical cell culture dish can be targeted without further user interaction. The automation allows for a significant increase in the number of treatable cells compared to a manual approach. For a laser illumination duration of 100 ms, 7-8 positions on different cells can be targeted every second inside the area of the microscope field of view. The experimental capabilities of the setup are illustrated in experiments with Chinese hamster ovary cells. Furthermore, the influence of laser power is discussed, with mention on post-treatment cell survival and optoporation-efficiency rates. PMID:26053047

  2. Semi-brittle flow of granitoid fault rocks in experiments

    NASA Astrophysics Data System (ADS)

    Pec, Matej; Stünitz, Holger; Heilbronner, Renée.; Drury, Martyn

    2016-03-01

    Field studies and seismic data show that semi-brittle flow of fault rocks probably is the dominant deformation mechanism at the base of the seismogenic zone at the so-called frictional-viscous transition. To understand the physical and chemical processes accommodating semi-brittle flow, we have performed an experimental study on synthetic granitoid fault rocks exploring a broad parameter space (temperature, T = 300, 400, 500, and 600°C, confining pressure, Pc ≈ 300, 500, 1000, and 1500 MPa, shear strain rate, γṡ ≈ 10-3, 10-4, 10-5, and 10-6 s-1, to finite shear strains, γ = 0-5). The experiments have been carried out using a granular material with grain size smaller than 200 µm with a little H2O added (0.2 wt %). Only two experiments (performed at the fastest strain rates and lowest temperatures) have failed abruptly right after reaching peak strength (τ ~ 1400 MPa). All other samples reach high shear stresses (τ ~ 570-1600 MPa) then weaken slightly (by Δτ ~ 10-190 MPa) and continue to deform at a more or less steady state stress level. Clear temperature dependence and a weak strain rate dependence of the peak as well as steady state stress levels are observed. In order to express this relationship, the strain rate-stress sensitivity has been fit with a stress exponent, assuming γ˙ ∝ τn and yields high stress exponents (n ≈ 10-140), which decrease with increasing temperature. The microstructures show widespread comminution, strain partitioning, and localization into slip zones. The slip zones contain at first nanocrystalline and partly amorphous material. Later, during continued deformation, fully amorphous material develops in some of the slip zones. Despite the mechanical steady state conditions, the fabrics in the slip zones and outside continue to evolve and do not reach a steady state microstructure below γ = 5. Within the slip zones, the fault rock material progressively transforms from a crystalline solid to an amorphous material. We

  3. Structural signature of a brittle-to-ductile transition in self-assembled networks.

    PubMed

    Ramos, Laurence; Laperrousaz, Arnaud; Dieudonné, Philippe; Ligoure, Christian

    2011-09-30

    We study the nonlinear rheology of a novel class of transient networks, made of surfactant micelles of tunable morphology reversibly linked by block copolymers. We couple rheology and time-resolved structural measurements, using synchrotron radiation, to characterize the highly nonlinear viscoelastic regime. We propose the fluctuations of the degree of alignment of the micelles under shear as a probe to identify a fracture process. We show a clear signature of a brittle-to-ductile transition in transient gels, as the morphology of the micelles varies, and provide a parallel between the fracture of solids and the fracture under shear of viscoelastic fluids.

  4. Multi-stage learning aids applied to hands-on software training.

    PubMed

    Rother, Kristian; Rother, Magdalena; Pleus, Alexandra; Upmeier zu Belzen, Annette

    2010-11-01

    Delivering hands-on tutorials on bioinformatics software and web applications is a challenging didactic scenario. The main reason is that trainees have heterogeneous backgrounds, different previous knowledge and vary in learning speed. In this article, we demonstrate how multi-stage learning aids can be used to allow all trainees to progress at a similar speed. In this technique, the trainees can utilize cards with hints and answers to guide themselves self-dependently through a complex task. We have successfully conducted a tutorial for the molecular viewer PyMOL using two sets of learning aid cards. The trainees responded positively, were able to complete the task, and the trainer had spare time to respond to individual questions. This encourages us to conclude that multi-stage learning aids overcome many disadvantages of established forms of hands-on software training.

  5. STOP-IT: Windows executable software for the stop-signal paradigm.

    PubMed

    Verbruggen, Frederick; Logan, Gordon D; Stevens, Michaël A

    2008-05-01

    The stop-signal paradigm is a useful tool for the investigation of response inhibition. In this paradigm, subjects are instructed to respond as fast as possible to a stimulus unless a stop signal is presented after a variable delay. However, programming the stop-signal task is typically considered to be difficult. To overcome this issue, we present software called STOP-IT, for running the stop-signal task, as well as an additional analyzing program called ANALYZE-IT. The main advantage of both programs is that they are a precompiled executable, and for basic use there is no need for additional programming. STOP-IT and ANALYZE-IT are completely based on free software, are distributed under the GNU General Public License, and are available at the personal Web sites of the first two authors or at expsy.ugent.be/tscope/stop.html.

  6. SAFOD Brittle Microstructure and Mechanics Knowledge Base (BM2KB)

    NASA Astrophysics Data System (ADS)

    Babaie, Hassan A.; Broda Cindi, M.; Hadizadeh, Jafar; Kumar, Anuj

    2013-07-01

    Scientific drilling near Parkfield, California has established the San Andreas Fault Observatory at Depth (SAFOD), which provides the solid earth community with short range geophysical and fault zone material data. The BM2KB ontology was developed in order to formalize the knowledge about brittle microstructures in the fault rocks sampled from the SAFOD cores. A knowledge base, instantiated from this domain ontology, stores and presents the observed microstructural and analytical data with respect to implications for brittle deformation and mechanics of faulting. These data can be searched on the knowledge base‧s Web interface by selecting a set of terms (classes, properties) from different drop-down lists that are dynamically populated from the ontology. In addition to this general search, a query can also be conducted to view data contributed by a specific investigator. A search by sample is done using the EarthScope SAFOD Core Viewer that allows a user to locate samples on high resolution images of core sections belonging to different runs and holes. The class hierarchy of the BM2KB ontology was initially designed using the Unified Modeling Language (UML), which was used as a visual guide to develop the ontology in OWL applying the Protégé ontology editor. Various Semantic Web technologies such as the RDF, RDFS, and OWL ontology languages, SPARQL query language, and Pellet reasoning engine, were used to develop the ontology. An interactive Web application interface was developed through Jena, a java based framework, with AJAX technology, jsp pages, and java servlets, and deployed via an Apache tomcat server. The interface allows the registered user to submit data related to their research on a sample of the SAFOD core. The submitted data, after initial review by the knowledge base administrator, are added to the extensible knowledge base and become available in subsequent queries to all types of users. The interface facilitates inference capabilities in the

  7. Brittle and Ductile Behavior in Deep-Seated Landslides: Learning from the Vajont Experience

    NASA Astrophysics Data System (ADS)

    Paronuzzi, Paolo; Bolla, Alberto; Rigo, Elia

    2016-06-01

    This paper analyzes the mechanical behavior of the unstable Mt. Toc slope before the 1963 catastrophic collapse, considering both the measured data (surface displacements and microseismicity) and the updated geological model of the prehistoric rockslide. From February 1960 up to 9 October 1963, the unstable mass behaved as a brittle-ductile `mechanical system,' characterized by remarkable microseismicity as well as by considerable surface displacements (up to 4-5 m). Recorded microshocks were the result of progressive rock fracturing of distinct resisting stiff parts made up of intact rock (indentations, undulations, and rock bridges). The main resisting stiff part was a large rock indentation located at the NE extremity of the unstable mass that acted as a mechanical constraint during the whole 1960-1963 period, inducing a progressive rototranslation toward the NE. This large constraint failed in autumn 1960, when an overall slope failure took place, as emphasized by the occurrence of the large perimetrical crack in the upper slope. In this circumstance, the collapse was inhibited by a reblocking phenomenon of the unstable mass that had been previously destabilized by the first reservoir filling. Progressive failure of localized intact rock parts progressively propagated westwards as a consequence of the two further filling-drawdown cycles of the reservoir (1962 and 1963). The characteristic brittle-ductile behavior of the Vajont landslide was made possible by the presence of a very thick (40-50 m) and highly deformable shear zone underlying the upper rigid rock mass (100-120 m thick).

  8. An elastic failure model of indentation damage. [of brittle structural ceramics

    NASA Technical Reports Server (NTRS)

    Liaw, B. M.; Kobayashi, A. S.; Emery, A. F.

    1984-01-01

    A mechanistically consistent model for indentation damage based on elastic failure at tensile or shear overloads, is proposed. The model accommodates arbitrary crack orientation, stress relaxation, reduction and recovery of stiffness due to crack opening and closure, and interfacial friction due to backward sliding of closed cracks. This elastic failure model was implemented by an axisymmetric finite element program which was used to simulate progressive damage in a silicon nitride plate indented by a tungsten carbide sphere. The predicted damage patterns and the permanent impression matched those observed experimentally. The validation of this elastic failure model shows that the plastic deformation postulated by others is not necessary to replicate the indentation damage of brittle structural ceramics.

  9. Software Program: Software Management Guidebook

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The purpose of this NASA Software Management Guidebook is twofold. First, this document defines the core products and activities required of NASA software projects. It defines life-cycle models and activity-related methods but acknowledges that no single life-cycle model is appropriate for all NASA software projects. It also acknowledges that the appropriate method for accomplishing a required activity depends on characteristics of the software project. Second, this guidebook provides specific guidance to software project managers and team leaders in selecting appropriate life cycles and methods to develop a tailored plan for a software engineering project.

  10. High Strain Rate Tensile Testing of Silver Nanowires: Rate-Dependent Brittle-to-Ductile Transition.

    PubMed

    Ramachandramoorthy, Rajaprakash; Gao, Wei; Bernal, Rodrigo; Espinosa, Horacio

    2016-01-13

    The characterization of nanomaterials under high strain rates is critical to understand their suitability for dynamic applications such as nanoresonators and nanoswitches. It is also of great theoretical importance to explore nanomechanics with dynamic and rate effects. Here, we report in situ scanning electron microscope (SEM) tensile testing of bicrystalline silver nanowires at strain rates up to 2/s, which is 2 orders of magnitude higher than previously reported in the literature. The experiments are enabled by a microelectromechanical system (MEMS) with fast response time. It was identified that the nanowire plastic deformation has a small activation volume (<10b(3)), suggesting dislocation nucleation as the rate controlling mechanism. Also, a remarkable brittle-to-ductile failure mode transition was observed at a threshold strain rate of 0.2/s. Transmission electron microscopy (TEM) revealed that along the nanowire, dislocation density and spatial distribution of plastic regions increase with increasing strain rate. Furthermore, molecular dynamic (MD) simulations show that deformation mechanisms such as grain boundary migration and dislocation interactions are responsible for such ductility. Finally, the MD and experimental results were interpreted using dislocation nucleation theory. The predicted yield stress values are in agreement with the experimental results for strain rates above 0.2/s when ductility is pronounced. At low strain rates, random imperfections on the nanowire surface trigger localized plasticity, leading to a brittle-like failure.

  11. Crack deflection in brittle media with heterogeneous interfaces and its application in shale fracking

    NASA Astrophysics Data System (ADS)

    Zeng, Xiaguang; Wei, Yujie

    Driven by the rapid progress in exploiting unconventional energy resources such as shale gas, there is growing interest in hydraulic fracture of brittle yet heterogeneous shales. In particular, how hydraulic cracks interact with natural weak zones in sedimentary rocks to form permeable cracking networks is of significance in engineering practice. Such a process is typically influenced by crack deflection, material anisotropy, crack-surface friction, crustal stresses, and so on. In this work, we extend the He-Hutchinson theory (He and Hutchinson, 1989) to give the closed-form formulae of the strain energy release rate of a hydraulic crack with arbitrary angles with respect to the crustal stress. The critical conditions in which the hydraulic crack deflects into weak interfaces and exhibits a dependence on crack-surface friction and crustal stress anisotropy are given in explicit formulae. We reveal analytically that, with increasing pressure, hydraulic fracture in shales may sequentially undergo friction locking, mode II fracture, and mixed mode fracture. Mode II fracture dominates the hydraulic fracturing process and the impinging angle between the hydraulic crack and the weak interface is the determining factor that accounts for crack deflection; the lower friction coefficient between cracked planes and the greater crustal stress difference favor hydraulic fracturing. In addition to shale fracking, the analytical solution of crack deflection could be used in failure analysis of other brittle media.

  12. Making software get along: integrating optical and mechanical design programs

    NASA Astrophysics Data System (ADS)

    Shackelford, Christie J.; Chinnock, Randal B.

    2001-03-01

    As modern optomechanical engineers, we have the good fortune of having very sophisticated software programs available to us. The current optical design, mechanical design, industrial design, and CAM programs are very powerful tools with some very desirable features. However, no one program can do everything necessary to complete an entire optomechanical system design. Each program has a unique set of features and benefits, and typically two or mo re will be used during the product development process. At a minimum, an optical design program and a mechanical CAD package will be employed. As we strive for efficient, cost-effective, and rapid progress in our development projects, we must use these programs to their full advantage, while keeping redundant tasks to a minimum. Together, these programs offer the promise of a `seamless' flow of data from concept all the way to the download of part designs directly to the machine shop for fabrication. In reality, transferring data from one software package to the next is often frustrating. Overcoming these problems takes some know-how, a bit of creativity, and a lot of persistence. This paper describes a complex optomechanical development effort in which a variety of software tools were used from the concept stage to prototyping. It will describe what software was used for each major design task, how we learned to use them together to best advantage, and how we overcame the frustrations of software that didn't get along.

  13. Weighted Ensemble Simulation: Review of Methodology, Applications, and Software.

    PubMed

    Zuckerman, Daniel M; Chong, Lillian T

    2017-05-22

    The weighted ensemble (WE) methodology orchestrates quasi-independent parallel simulations run with intermittent communication that can enhance sampling of rare events such as protein conformational changes, folding, and binding. The WE strategy can achieve superlinear scaling-the unbiased estimation of key observables such as rate constants and equilibrium state populations to greater precision than would be possible with ordinary parallel simulation. WE software can be used to control any dynamics engine, such as standard molecular dynamics and cell-modeling packages. This article reviews the theoretical basis of WE and goes on to describe successful applications to a number of complex biological processes-protein conformational transitions, (un)binding, and assembly processes, as well as cell-scale processes in systems biology. We furthermore discuss the challenges that need to be overcome in the next phase of WE methodological development. Overall, the combined advances in WE methodology and software have enabled the simulation of long-timescale processes that would otherwise not be practical on typical computing resources using standard simulation.

  14. Software analysis handbook: Software complexity analysis and software reliability estimation and prediction

    NASA Technical Reports Server (NTRS)

    Lee, Alice T.; Gunn, Todd; Pham, Tuan; Ricaldi, Ron

    1994-01-01

    This handbook documents the three software analysis processes the Space Station Software Analysis team uses to assess space station software, including their backgrounds, theories, tools, and analysis procedures. Potential applications of these analysis results are also presented. The first section describes how software complexity analysis provides quantitative information on code, such as code structure and risk areas, throughout the software life cycle. Software complexity analysis allows an analyst to understand the software structure, identify critical software components, assess risk areas within a software system, identify testing deficiencies, and recommend program improvements. Performing this type of analysis during the early design phases of software development can positively affect the process, and may prevent later, much larger, difficulties. The second section describes how software reliability estimation and prediction analysis, or software reliability, provides a quantitative means to measure the probability of failure-free operation of a computer program, and describes the two tools used by JSC to determine failure rates and design tradeoffs between reliability, costs, performance, and schedule.

  15. A micromechanical constitutive model for the dynamic response of brittle materials "Dynamic response of marble"

    NASA Astrophysics Data System (ADS)

    Haberman, Keith

    2001-07-01

    A micromechanically based constitutive model for the dynamic inelastic behavior of brittle materials, specifically "Dionysus-Pentelicon marble" with distributed microcracking is presented. Dionysus-Pentelicon marble was used in the construction of the Parthenon, in Athens, Greece. The constitutive model is a key component in the ability to simulate this historic explosion and the preceding bombardment form cannon fire that occurred at the Parthenon in 1678. Experiments were performed by Rosakis (1999) that characterized the static and dynamic response of this unique material. A micromechanical constitutive model that was previously successfully used to model the dynamic response of granular brittle materials is presented. The constitutive model was fitted to the experimental data for marble and reproduced the experimentally observed basic uniaxial dynamic behavior quite well. This micromechanical constitutive model was then implemented into the three dimensional nonlinear lagrangain finite element code Dyna3d(1998). Implementing this methodology into the three dimensional nonlinear dynamic finite element code allowed the model to be exercised on several preliminary impact experiments. During future simulations, the model is to be used in conjunction with other numerical techniques to simulate projectile impact and blast loading on the Dionysus-Pentelicon marble and on the structure of the Parthenon.

  16. Moving mesh finite element simulation for phase-field modeling of brittle fracture and convergence of Newton's iteration

    NASA Astrophysics Data System (ADS)

    Zhang, Fei; Huang, Weizhang; Li, Xianping; Zhang, Shicheng

    2018-03-01

    A moving mesh finite element method is studied for the numerical solution of a phase-field model for brittle fracture. The moving mesh partial differential equation approach is employed to dynamically track crack propagation. Meanwhile, the decomposition of the strain tensor into tensile and compressive components is essential for the success of the phase-field modeling of brittle fracture but results in a non-smooth elastic energy and stronger nonlinearity in the governing equation. This makes the governing equation much more difficult to solve and, in particular, Newton's iteration often fails to converge. Three regularization methods are proposed to smooth out the decomposition of the strain tensor. Numerical examples of fracture propagation under quasi-static load demonstrate that all of the methods can effectively improve the convergence of Newton's iteration for relatively small values of the regularization parameter but without compromising the accuracy of the numerical solution. They also show that the moving mesh finite element method is able to adaptively concentrate the mesh elements around propagating cracks and handle multiple and complex crack systems.

  17. Defining the Brittle Failure Envelopes of Individual Reaction Zones Observed in CO2-Exposed Wellbore Cement.

    PubMed

    Hangx, Suzanne J T; van der Linden, Arjan; Marcelis, Fons; Liteanu, Emilia

    2016-01-19

    To predict the behavior of the cement sheath after CO2 injection and the potential for leakage pathways, it is key to understand how the mechanical properties of the cement evolves with CO2 exposure time. We performed scratch-hardness tests on hardened samples of class G cement before and after CO2 exposure. The cement was exposed to CO2-rich fluid for one to six months at 65 °C and 8 MPa Ptotal. Detailed SEM-EDX analyses showed reaction zones similar to those previously reported in the literature: (1) an outer-reacted, porous silica-rich zone; (2) a dense, carbonated zone; and (3) a more porous, Ca-depleted inner zone. The quantitative mechanical data (brittle compressive strength and friction coefficient) obtained for each of the zones suggest that the heterogeneity of reacted cement leads to a wide range of brittle strength values in any of the reaction zones, with only a rough dependence on exposure time. However, the data can be used to guide numerical modeling efforts needed to assess the impact of reaction-induced mechanical failure of wellbore cement by coupling sensitivity analysis and mechanical predictions.

  18. Flow and fracture behavior of NiAl in relation to the brittle-to-ductile transition temperature

    NASA Technical Reports Server (NTRS)

    Noebe, R. D.; Bowman, R. R.; Cullers, C. L.; Raj, S. V.

    1991-01-01

    NiAl has only three independent slip systems operating at low and intermediate temperatures whereas five independent deformation mechanisms are required to satisfy the von Mises criterion for general plasticity in polycrystalline materials. Yet, it is generally recognized that polycrystalline NiAl can be deformed extensively in compression at room temperature and that limited tensile ductility can be obtained in extruded materials. In order to determine whether these results are in conflict with the von Mises criterion, tension and compression tests were conducted on powder-extruded, binary NiAl between 300 and 1300 K. The results indicate that below the brittle-to-ductile transition temperature (BDTT) the failure mechanism in NiAl involves the initiation and propagation of cracks at the grain boundaries which is consistent with the von Mises analysis. Furthermore, evaluation of the flow behavior of NiAl indicates that the transition from brittle to ductile behavior with increasing temperature coincides with the onset of recovery mechanisms such as dislocation climb. The increase in ductility above the BDTT is therefore attributed to the climb of the 001 line type dislocations which in combination with dislocation glide enable grain boundary compatibility to be maintained at the higher temperatures.

  19. Planning the Unplanned Experiment: Towards Assessing the Efficacy of Standards for Safety-Critical Software

    NASA Technical Reports Server (NTRS)

    Graydon, Patrick J.; Holloway, C. M.

    2015-01-01

    Safe use of software in safety-critical applications requires well-founded means of determining whether software is fit for such use. While software in industries such as aviation has a good safety record, little is known about whether standards for software in safety-critical applications 'work' (or even what that means). It is often (implicitly) argued that software is fit for safety-critical use because it conforms to an appropriate standard. Without knowing whether a standard works, such reliance is an experiment; without carefully collecting assessment data, that experiment is unplanned. To help plan the experiment, we organized a workshop to develop practical ideas for assessing software safety standards. In this paper, we relate and elaborate on the workshop discussion, which revealed subtle but important study design considerations and practical barriers to collecting appropriate historical data and recruiting appropriate experimental subjects. We discuss assessing standards as written and as applied, several candidate definitions for what it means for a standard to 'work,' and key assessment strategies and study techniques and the pros and cons of each. Finally, we conclude with thoughts about the kinds of research that will be required and how academia, industry, and regulators might collaborate to overcome the noted barriers.

  20. Tensile cracking of a brittle conformal coating on a rough substrate

    DOE PAGES

    Reedy, Jr., E. D.

    2016-04-07

    This note examines the effect of interfacial roughness on the initiation and growth of channel cracks in a brittle film. A conformal film with cusp-like surface flaws that replicate the substrate roughness is investigated. This type of surface flaw is relatively severe in the sense that stress diverges as the cusp-tip is approached (i.e., there is a power-law stress singularity). For the geometry and range of film properties considered, the analysis suggests that smoothing the substrate could substantially increase the film’s resistance to the formation of the through-the-thickness cracks that precede channel cracking. Furthermore, smoothing the substrate’s surface has amore » relatively modest effect on the film stress needed to propagate a channel crack.« less

  1. An Experimental and Numerical Study on Cracking Behavior of Brittle Sandstone Containing Two Non-coplanar Fissures Under Uniaxial Compression

    NASA Astrophysics Data System (ADS)

    Yang, Sheng-Qi; Tian, Wen-Ling; Huang, Yan-Hua; Ranjith, P. G.; Ju, Yang

    2016-04-01

    To understand the fracture mechanism in all kinds of rock engineering, it is important to investigate the fracture evolution behavior of pre-fissured rock. In this research, we conducted uniaxial compression experiments to evaluate the influence of ligament angle on the strength, deformability, and fracture coalescence behavior of rectangular prismatic specimens (80 × 160 × 30 mm) of brittle sandstone containing two non-coplanar fissures. The experimental results show that the peak strength of sandstone containing two non-coplanar fissures depends on the ligament angle, but the elastic modulus is not closely related to the ligament angle. With the increase of ligament angle, the peak strength decreased at a ligament angle of 60°, before increasing up to our maximum ligament angle of 120°. Crack initiation, propagation, and coalescence were all observed and characterized from the inner and outer tips of pre-existing non-coplanar fissures using photographic monitoring. Based on the results, the sequence of crack evolution in sandstone containing two non-coplanar fissures was analyzed in detail. In order to fully understand the crack evolution mechanism of brittle sandstone, numerical simulations using PFC2D were performed for specimens containing two non-coplanar fissures under uniaxial compression. The results are in good agreement with the experimental results. By analyzing the stress field, the crack evolution mechanism in brittle sandstone containing two non-coplanar fissures under uniaxial compression is revealed. These experimental and numerical results are expected to improve the understanding of the unstable fracture mechanism of fissured rock engineering structures.

  2. Risk Based Inspection Methodology and Software Applied to Atmospheric Storage Tanks

    NASA Astrophysics Data System (ADS)

    Topalis, P.; Korneliussen, G.; Hermanrud, J.; Steo, Y.

    2012-05-01

    A new risk-based inspection (RBI) methodology and software is presented in this paper. The objective of this work is to allow management of the inspections of atmospheric storage tanks in the most efficient way, while, at the same time, accident risks are minimized. The software has been built on the new risk framework architecture, a generic platform facilitating efficient and integrated development of software applications using risk models. The framework includes a library of risk models and the user interface is automatically produced on the basis of editable schemas. This risk-framework-based RBI tool has been applied in the context of RBI for above-ground atmospheric storage tanks (AST) but it has been designed with the objective of being generic enough to allow extension to the process plants in general. This RBI methodology is an evolution of an approach and mathematical models developed for Det Norske Veritas (DNV) and the American Petroleum Institute (API). The methodology assesses damage mechanism potential, degradation rates, probability of failure (PoF), consequence of failure (CoF) in terms of environmental damage and financial loss, risk and inspection intervals and techniques. The scope includes assessment of the tank floor for soil-side external corrosion and product-side internal corrosion and the tank shell courses for atmospheric corrosion and internal thinning. It also includes preliminary assessment for brittle fracture and cracking. The data are structured according to an asset hierarchy including Plant, Production Unit, Process Unit, Tag, Part and Inspection levels and the data are inherited / defaulted seamlessly from a higher hierarchy level to a lower level. The user interface includes synchronized hierarchy tree browsing, dynamic editor and grid-view editing and active reports with drill-in capability.

  3. Overcoming the Polyester Image.

    ERIC Educational Resources Information Center

    Regan, Dorothy

    1988-01-01

    Urges community colleges to overcome their image problem by documenting the colleges' impact on their communities. Suggests ways to determine what data should be collected, how to collect the information, and how it can be used to empower faculty, staff, and alumni to change the institution's image. (DMM)

  4. Reactive-brittle dynamics in peridotite alteration

    NASA Astrophysics Data System (ADS)

    Evans, O.; Spiegelman, M. W.; Kelemen, P. B.

    2017-12-01

    The interactions between reactive fluids and brittle solids are critical in Earth dynamics. Implications of such processes are wide-ranging: from earthquake physics to geologic carbon sequestration and the cycling of fluids and volatiles through subduction zones. Peridotite alteration is a common feature in many of these processes, which - despite its obvious importance - is relatively poorly understood from a geodynamical perspective. In particular, alteration reactions are thought to be self-limiting in nature, contradicting observations of rocks that have undergone 100% hydration/carbonation. One potential explanation of this observation is the mechanism of "reaction-driven cracking": that volume changes associated with these reactions are large enough to fracture the surrounding rock, leading to a positive feedback where new reactive surfaces are exposed and fluid pathways are created. The purpose of this study is to investigate the relative roles of reaction, elastic stresses and surface tension in alteration reactions. In this regard we derive a system of equations describing reactive fluid flow in an elastically deformable porous media, and explore them via a combination of analytic and numerical solutions. Using this model we show that the final stress state of a dry peridotite that has undergone reaction depends strongly on the rates of reaction versus fluid transport: significant fluid flow driven by pressure and/or surface tension gradients implies higher fractions of serpentinization, leaving behind a highly stressed residuum of partially reacted material. Using a model set-up that mimics a cylindrical triaxial apparatus we predict that the resulting stresses would lead to tensile failure and the generation of radially oriented cracks.

  5. Why Mondragon? Analyzing What Works in Overcoming Inequalities

    ERIC Educational Resources Information Center

    Redondo, Gisela; Santa Cruz, Ignacio; Rotger, Josep Maria

    2011-01-01

    Research using the critical communicative methodology (CCM) aims to identify the elements that help overcome inequalities. Drawing on research on the Basque Mondragon Corporation (MC), the authors focus on two major elements such as, selecting research cases that have been shown to succeed in overcoming inequalities, and communicative data…

  6. Predicting the Reliability of Brittle Material Structures Subjected to Transient Proof Test and Service Loading

    NASA Astrophysics Data System (ADS)

    Nemeth, Noel N.; Jadaan, Osama M.; Palfi, Tamas; Baker, Eric H.

    Brittle materials today are being used, or considered, for a wide variety of high tech applications that operate in harsh environments, including static and rotating turbine parts, thermal protection systems, dental prosthetics, fuel cells, oxygen transport membranes, radomes, and MEMS. Designing brittle material components to sustain repeated load without fracturing while using the minimum amount of material requires the use of a probabilistic design methodology. The NASA CARES/Life 1 (Ceramic Analysis and Reliability Evaluation of Structure/Life) code provides a general-purpose analysis tool that predicts the probability of failure of a ceramic component as a function of its time in service. This capability includes predicting the time-dependent failure probability of ceramic components against catastrophic rupture when subjected to transient thermomechanical loads (including cyclic loads). The developed methodology allows for changes in material response that can occur with temperature or time (i.e. changing fatigue and Weibull parameters with temperature or time). For this article an overview of the transient reliability methodology and how this methodology is extended to account for proof testing is described. The CARES/Life code has been modified to have the ability to interface with commercially available finite element analysis (FEA) codes executed for transient load histories. Examples are provided to demonstrate the features of the methodology as implemented in the CARES/Life program.

  7. Fracture toughness of brittle materials determined with chevron notch specimens

    NASA Technical Reports Server (NTRS)

    Shannon, J. L., Jr.; Bubsey, R. T.; Pierce, W. S.; Munz, D.

    1981-01-01

    Short bar, short rod, and four-point-bend chevron-notch specimens were used to determine the plane strain fracture toughness of hot-pressed silicon nitride and sintered aluminum oxide brittle ceramics. The unique advantages of this specimen type are: (1) the production of a sharp natural crack during the early stage of test loading, so that no precracking is required, and (2) the load passes through a maximum at a constant, material-independent crack length-to-width ratio for a specific geometry, so that no post-test crack measurement is required. The plane strain fracture toughness is proportional to the maximum test load and functions of the specimen geometry and elastic compliance. Although results obtained for silicon nitride are in good mutual agreement and relatively free of geometry and size effects, aluminum oxide results were affected in both these respects by the rising crack growth resistance curve of the material.

  8. The influence of coarse aggregate size and volume on the fracture behavior and brittleness of self-compacting concrete

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Beygi, Morteza H.A., E-mail: M.beygi@nit.ac.ir; Kazemi, Mohammad Taghi, E-mail: Kazemi@sharif.edu; Nikbin, Iman M., E-mail: nikbin@iaurasht.ac.ir

    2014-12-15

    This paper presents the results of an experimental investigation on fracture characteristics and brittleness of self-compacting concrete (SCC), involving the tests of 185 three point bending beams with different coarse aggregate size and content. Generally, the parameters were analyzed by the work of fracture method (WFM) and the size effect method (SEM). The results showed that with increase of size and content of coarse aggregate, (a) the fracture energy increases which is due to the change in fractal dimensions, (b) behavior of SCC beams approaches strength criterion, (c) characteristic length, which is deemed as an index of brittleness, increases linearly.more » It was found with decrease of w/c ratio that fracture energy increases which may be explained by the improvement in structure of aggregate-paste transition zone. Also, the results showed that there is a correlation between the fracture energy measured by WFM (G{sub F}) and the value measured through SEM (G{sub f}) (G{sub F} = 3.11G{sub f})« less

  9. Structure and software tools of AIDA.

    PubMed

    Duisterhout, J S; Franken, B; Witte, F

    1987-01-01

    AIDA consists of a set of software tools to allow for fast development and easy-to-maintain Medical Information Systems. AIDA supports all aspects of such a system both during development and operation. It contains tools to build and maintain forms for interactive data entry and on-line input validation, a database management system including a data dictionary and a set of run-time routines for database access, and routines for querying the database and output formatting. Unlike an application generator, the user of AIDA may select parts of the tools to fulfill his needs and program other subsystems not developed with AIDA. The AIDA software uses as host language the ANSI-standard programming language MUMPS, an interpreted language embedded in an integrated database and programming environment. This greatly facilitates the portability of AIDA applications. The database facilities supported by AIDA are based on a relational data model. This data model is built on top of the MUMPS database, the so-called global structure. This relational model overcomes the restrictions of the global structure regarding string length. The global structure is especially powerful for sorting purposes. Using MUMPS as a host language allows the user an easy interface between user-defined data validation checks or other user-defined code and the AIDA tools. AIDA has been designed primarily for prototyping and for the construction of Medical Information Systems in a research environment which requires a flexible approach. The prototyping facility of AIDA operates terminal independent and is even to a great extent multi-lingual. Most of these features are table-driven; this allows on-line changes in the use of terminal type and language, but also causes overhead. AIDA has a set of optimizing tools by which it is possible to build a faster, but (of course) less flexible code from these table definitions. By separating the AIDA software in a source and a run-time version, one is able to write

  10. Time-resolved study of femtosecond laser induced micro-modifications inside transparent brittle materials

    NASA Astrophysics Data System (ADS)

    Hendricks, F.; Matylitsky, V. V.; Domke, M.; Huber, Heinz P.

    2016-03-01

    Laser processing of optically transparent or semi-transparent, brittle materials is finding wide use in various manufacturing sectors. For example, in consumer electronic devices such as smartphones or tablets, cover glass needs to be cut precisely in various shapes. The unique advantage of material processing with femtosecond lasers is efficient, fast and localized energy deposition in nearly all types of solid materials. When an ultra-short laser pulse is focused inside glass, only the localized region in the neighborhood of the focal volume absorbs laser energy by nonlinear optical absorption. Therefore, the processing volume is strongly defined, while the rest of the target stays unaffected. Thus ultra-short pulse lasers allow cutting of the chemically strengthened glasses such as Corning Gorilla glass without cracking. Non-ablative cutting of transparent, brittle materials, using the newly developed femtosecond process ClearShapeTM from Spectra-Physics, is based on producing a micron-sized material modification track with well-defined geometry inside. The key point for development of the process is to understand the induced modification by a single femtosecond laser shot. In this paper, pump-probe microscopy techniques have been applied to study the defect formation inside of transparent materials, namely soda-lime glass samples, on a time scale between one nanosecond to several tens of microseconds. The observed effects include acoustic wave propagation as well as mechanical stress formation in the bulk of the glass. Besides better understanding of underlying physical mechanisms, our experimental observations have enabled us to find optimal process parameters for the glass cutting application and lead to better quality and speed for the ClearShapeTM process.

  11. Weighted Ensemble Simulation: Review of Methodology, Applications, and Software

    PubMed Central

    Zuckerman, Daniel M.; Chong, Lillian T.

    2018-01-01

    The weighted ensemble (WE) methodology orchestrates quasi-independent parallel simulations run with intermittent communication that can enhance sampling of rare events such as protein conformational changes, folding, and binding. The WE strategy can achieve superlinear scaling—the unbiased estimation of key observables such as rate constants and equilibrium state populations to greater precision than would be possible with ordinary parallel simulation. WE software can be used to control any dynamics engine, such as standard molecular dynamics and cell-modeling packages. This article reviews the theoretical basis of WE and goes on to describe successful applications to a number of complex biological processes—protein conformational transitions, (un)binding, and assembly processes, as well as cell-scale processes in systems biology. We furthermore discuss the challenges that need to be overcome in the next phase of WE methodological development. Overall, the combined advances in WE methodology and software have enabled the simulation of long-timescale processes that would otherwise not be practical on typical computing resources using standard simulation. PMID:28301772

  12. A brittle to ductile transition in NiAl of a critical grain size

    NASA Technical Reports Server (NTRS)

    Schulson, E. M.; Barker, D. R.

    1983-01-01

    Tensile tests have been carried out on the strongly ordered B2 aluminide NiAl at 400 C to investigate the effect of the grain size on the ductility of the material. It is found that the ductility is very low and essentially independent of the grain size for aggregates of grains larger than about 20 microns; for finer-grained aggregates, the ductility increases sharply with decreasing grain size. Thus, NiAl exhibits a critical grain size below which polycrystalline aggregates are ductile in tension. For all grain sizes, fracture occurs in a brittle manner through a combination of intergranular decohesion and transgranular cleavage.

  13. Office Computer Software: A Comprehensive Review of Software Programs.

    ERIC Educational Resources Information Center

    Secretary, 1992

    1992-01-01

    Describes types of software including system software, application software, spreadsheets, accounting software, graphics packages, desktop publishing software, database, desktop and personal information management software, project and records management software, groupware, and shareware. (JOW)

  14. Software Library: A Reusable Software Issue.

    DTIC Science & Technology

    1984-06-01

    On reverse aide it neceeary aid Identify by block number) Software Library; Program Library; Reusability; Generator 20 ABSTRACT (Cmlnue on revere... Software Library. A particular example of the Software Library, the Program Library, is described as a prototype of a reusable library. A hierarchical... programming libraries are described. Finally, non code products in the Software Library are discussed. Accesson Fo NTIS R~jS DrrC TA Availability Codes 0

  15. The "fault of the Pool" along the Congo River between Kinshasa and Brazzaville, R(D)Congo is no more a myth: Paleostress from small-scale brittle structures

    NASA Astrophysics Data System (ADS)

    Delvaux, Damien; Ganza, Gloire; Kongota, Elvis; Fukiabantu, Guilain; Mbokola, Dim; Boudzoumou, Florent; Miyouna, Timothée; Gampio, Urbain; Nkodia, Hardy

    2017-04-01

    Small-scale brittle structures such as shear fractures and tension joints are well developed in the indurated Paleozoic Inkisi red sandstones of the West-Congo Supergroup in the "pool" region of Kinshasa and Brazzaville, along the Congo River. They appear to be related to the evolution of intraplate stresses during the late Cretaceous-Paleogene period, possibly related to the opening of the South Atlantic. However, inferring paleostresses from such structures is difficult due to the lack of clear kinematic indicators, so we used mainly the geometry, architecture and sequence of the joint systems to infer paleostresses. A limited number of kinematic indicators for slip sense (displaced pebbles, irregularities on striated surfaces, slickensides) or extension (plume joints) confirm the general conclusions of the joint architecture analysis. We found evidence for two major brittle deformation systems, leading to almost orthogonal fracture sets. They both started by the development of plume joints, which progressively evolved into open tension joints, isolated shear fractures and long (up to several hundred meters) brittle shear zones. The first system started to develop under NE-SW extension and evolved into strike-slip with NNW-SSE horizontal compression while the second (and later), started to develop under NW-SE extension and evolved into strike-slip with NNE-SSW horizontal compression. The second brittle deformation episode was associated with fluid flow as shown by the presence of palygorskite-calcite veins in the most prominent fractures of the second fracture system. Along the NE-SW brittle shear zones which run parallel to the Congo River, carbonate-rich fault-gauge lenses are filled by sand derived from the crushed adjacent walls and calcite vein fragments injected at a high fluid pressure, with late precipitation of palygorskite. Our study demonstrates the existence of two fault systems between Kinshasa and Brazzaville, the first one orthogonal to the trend

  16. Computational Software for Fitting Seismic Data to Epidemic-Type Aftershock Sequence Models

    NASA Astrophysics Data System (ADS)

    Chu, A.

    2014-12-01

    Modern earthquake catalogs are often analyzed using spatial-temporal point process models such as the epidemic-type aftershock sequence (ETAS) models of Ogata (1998). My work introduces software to implement two of ETAS models described in Ogata (1998). To find the Maximum-Likelihood Estimates (MLEs), my software provides estimates of the homogeneous background rate parameter and the temporal and spatial parameters that govern triggering effects by applying the Expectation-Maximization (EM) algorithm introduced in Veen and Schoenberg (2008). Despite other computer programs exist for similar data modeling purpose, using EM-algorithm has the benefits of stability and robustness (Veen and Schoenberg, 2008). Spatial shapes that are very long and narrow cause difficulties in optimization convergence and problems with flat or multi-modal log-likelihood functions encounter similar issues. My program uses a robust method to preset a parameter to overcome the non-convergence computational issue. In addition to model fitting, the software is equipped with useful tools for examining modeling fitting results, for example, visualization of estimated conditional intensity, and estimation of expected number of triggered aftershocks. A simulation generator is also given with flexible spatial shapes that may be defined by the user. This open-source software has a very simple user interface. The user may execute it on a local computer, and the program also has potential to be hosted online. Java language is used for the software's core computing part and an optional interface to the statistical package R is provided.

  17. Representation and Management of the Knowledge of Brittle Deformation in Shear Zones Using Microstructural Data From the SAFOD Core Samples

    NASA Astrophysics Data System (ADS)

    Babaie, H. A.; Broda, C. M.; Kumar, A.; Hadizadeh, J.

    2010-12-01

    Web access to data that represent knowledge acquired by investigators studying the microstructures in the core samples of the SAFOD (San Andreas Observatory at Depth) project can help scientists efficiently integrate and share knowledge, query the data, and update the knowledge base on the Web. To achieve this, we have used OWL (Web Ontology Language) to build the brittle deformation ontology for the microstructures observed in the SAFOD core samples, by explicitly formalizing the knowledge about deformational processes, geological objects undergoing deformation, and the underlying mechanical and environmental conditions in brittle shear zones. The developed Web-based ‘SAFOD Brittle Microstructure and Mechanics Knowledge base’ (SAFOD BM2KB), which instantiates this ontology and is available at http://codd.cs.gsu.edu:9999/safod/index.jsp, will host and serve data that pertains to spatial objects, such as microstructure, gouge, fault, and SEM image, acquired by the SAFOD investigators through the studies of the SAFOD core samples. Deformation in shear zones involves complex brittle and ductile processes that alter, create, and/or destroy a wide variety of one- to three-dimensional, multi-scale spatial entities such as rocks and their constituent minerals and structure. These processes occur through a series of sub-processes that happen in different time intervals, and affect the spatial objects at granular to regional scales within shear zones. The processes bring about qualitative change to the spatial entities over time intervals that start and end with events. Processes, such as mylonitization and cataclastic flow, change the spatial location, distribution, dimension, size, shape, and orientation of some objects through translation, rotation and strain. These processes may also result in newly formed entities, such as a new mineral, gouge, vein, or fault, during one or more phases of deformation. Deformation processes may also destroy entities, such as a

  18. Photonic ADC: overcoming the bottleneck of electronic jitter.

    PubMed

    Khilo, Anatol; Spector, Steven J; Grein, Matthew E; Nejadmalayeri, Amir H; Holzwarth, Charles W; Sander, Michelle Y; Dahlem, Marcus S; Peng, Michael Y; Geis, Michael W; DiLello, Nicole A; Yoon, Jung U; Motamedi, Ali; Orcutt, Jason S; Wang, Jade P; Sorace-Agaskar, Cheryl M; Popović, Miloš A; Sun, Jie; Zhou, Gui-Rong; Byun, Hyunil; Chen, Jian; Hoyt, Judy L; Smith, Henry I; Ram, Rajeev J; Perrott, Michael; Lyszczarz, Theodore M; Ippen, Erich P; Kärtner, Franz X

    2012-02-13

    Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical imaging, and communication systems. Aperture jitter has been a major bottleneck on the way towards higher speeds and better accuracy. Photonic ADCs, which perform sampling using ultra-stable optical pulse trains generated by mode-locked lasers, have been investigated for many years as a promising approach to overcome the jitter problem and bring ADC performance to new levels. This work demonstrates that the photonic approach can deliver on its promise by digitizing a 41 GHz signal with 7.0 effective bits using a photonic ADC built from discrete components. This accuracy corresponds to a timing jitter of 15 fs - a 4-5 times improvement over the performance of the best electronic ADCs which exist today. On the way towards an integrated photonic ADC, a silicon photonic chip with core photonic components was fabricated and used to digitize a 10 GHz signal with 3.5 effective bits. In these experiments, two wavelength channels were implemented, providing the overall sampling rate of 2.1 GSa/s. To show that photonic ADCs with larger channel counts are possible, a dual 20-channel silicon filter bank has been demonstrated.

  19. Spatio-Temporal Modelling of the Pre-Eruptive Strain Localization in a Volcanic Edifice Using a Maxwell-Elasto-Brittle Rheology

    NASA Astrophysics Data System (ADS)

    Dansereau, V.; Got, J. L.

    2017-12-01

    Before a volcanic eruption, the pressurization of the volcanic edifice by a magma reservoir induces earthquakes and damage in the edifice; damage lowers the strength of the edifice and decreases its elastic properties. Anelastic deformations cumulate and lead to rupture and eruption. These deformations translate into surface displacements, measurable via GPS or InSAR (e.g., Kilauea, southern flank, or Piton de la Fournaise, eastern flank).Attempts to represent these processes are usually based on a linear-elastic rheology. More recently, linear elastic-perfectly plastic or elastic-brittle damage approaches were used to explain the time evolution of the surface displacements in basaltic volcanoes before an eruption. However these models are non-linear elastic, and can not account for the anelastic deformation that occurs during the pre-eruptive process. Therefore, they can not be used to represent the complete eruptive cycle, comprising loading and unloading phases. Here we present a new rheological approach for modelling the eruptive cycle called Maxwell-Elasto-Brittle, which incorporates a viscous-like relaxation of the stresses in an elastic-brittle damage framework. This mechanism allows accounting for the anelastic deformations that cumulate and lead to rupture and eruption. The inclusion of healing processes in this model is another step towards a complete spatio-temporal representation of the eruptive cycle. Plane-strain Maxwell-EB modelling of the deformation of a magma reservoir and volcanic edifice will be presented. The model represents the propagation of damage towards the surface and the progressive localization of the deformation along faults under the pressurization of the magma reservoir. This model allows a complete spatio-temporal representation of the rupture process. We will also discuss how available seismicity records and time series of surface displacements could be used jointly to constrain the model.

  20. Product-oriented Software Certification Process for Software Synthesis

    NASA Technical Reports Server (NTRS)

    Nelson, Stacy; Fischer, Bernd; Denney, Ewen; Schumann, Johann; Richardson, Julian; Oh, Phil

    2004-01-01

    The purpose of this document is to propose a product-oriented software certification process to facilitate use of software synthesis and formal methods. Why is such a process needed? Currently, software is tested until deemed bug-free rather than proving that certain software properties exist. This approach has worked well in most cases, but unfortunately, deaths still occur due to software failure. Using formal methods (techniques from logic and discrete mathematics like set theory, automata theory and formal logic as opposed to continuous mathematics like calculus) and software synthesis, it is possible to reduce this risk by proving certain software properties. Additionally, software synthesis makes it possible to automate some phases of the traditional software development life cycle resulting in a more streamlined and accurate development process.

  1. Generalized Reliability Methodology Applied to Brittle Anisotropic Single Crystals. Degree awarded by Washington Univ., 1999

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.

    2002-01-01

    A generalized reliability model was developed for use in the design of structural components made from brittle, homogeneous anisotropic materials such as single crystals. The model is based on the Weibull distribution and incorporates a variable strength distribution and any equivalent stress failure criteria. In addition to the reliability model, an energy based failure criterion for elastically anisotropic materials was formulated. The model is different from typical Weibull-based models in that it accounts for strength anisotropy arising from fracture toughness anisotropy and thereby allows for strength and reliability predictions of brittle, anisotropic single crystals subjected to multiaxial stresses. The model is also applicable to elastically isotropic materials exhibiting strength anisotropy due to an anisotropic distribution of flaws. In order to develop and experimentally verify the model, the uniaxial and biaxial strengths of a single crystal nickel aluminide were measured. The uniaxial strengths of the <100> and <110> crystal directions were measured in three and four-point flexure. The biaxial strength was measured by subjecting <100> plates to a uniform pressure in a test apparatus that was developed and experimentally verified. The biaxial strengths of the single crystal plates were estimated by extending and verifying the displacement solution for a circular, anisotropic plate to the case of a variable radius and thickness. The best correlation between the experimental strength data and the model predictions occurred when an anisotropic stress analysis was combined with the normal stress criterion and the strength parameters associated with the <110> crystal direction.

  2. Software design and implementation concepts for an interoperable medical communication framework.

    PubMed

    Besting, Andreas; Bürger, Sebastian; Kasparick, Martin; Strathen, Benjamin; Portheine, Frank

    2018-02-23

    The new IEEE 11073 service-oriented device connectivity (SDC) standard proposals for networked point-of-care and surgical devices constitutes the basis for improved interoperability due to its independence of vendors. To accelerate the distribution of the standard a reference implementation is indispensable. However, the implementation of such a framework has to overcome several non-trivial challenges. First, the high level of complexity of the underlying standard must be reflected in the software design. An efficient implementation has to consider the limited resources of the underlying hardware. Moreover, the frameworks purpose of realizing a distributed system demands a high degree of reliability of the framework itself and its internal mechanisms. Additionally, a framework must provide an easy-to-use and fail-safe application programming interface (API). In this work, we address these challenges by discussing suitable software engineering principles and practical coding guidelines. A descriptive model is developed that identifies key strategies. General feasibility is shown by outlining environments in which our implementation has been utilized.

  3. A dataset describing brooding in three species of South African brittle stars, comprising seven high-resolution, micro X-ray computed tomography scans.

    PubMed

    Landschoff, Jannes; Du Plessis, Anton; Griffiths, Charles L

    2015-01-01

    Brooding brittle stars have a special mode of reproduction whereby they retain their eggs and juveniles inside respiratory body sacs called bursae. In the past, studying this phenomenon required disturbance of the sample by dissecting the adult. This caused irreversible damage and made the sample unsuitable for future studies. Micro X-ray computed tomography (μCT) is a promising technique, not only to visualise juveniles inside the bursae, but also to keep the sample intact and make the dataset of the scan available for future reference. Seven μCT scans of five freshly fixed (70 % ethanol) individuals, representing three differently sized brittle star species, provided adequate image quality to determine the numbers, sizes and postures of internally brooded young, as well as anatomy and morphology of adults. No staining agents were necessary to achieve high-resolution, high-contrast images, which permitted visualisations of both calcified and soft tissue. The raw data (projection and reconstruction images) are publicly available for download from GigaDB. Brittle stars of all sizes are suitable candidates for μCT imaging. This explicitly adds a new technique to the suite of tools available for studying the development of internally brooded young. The purpose of applying the technique was to visualise juveniles inside the adult, but because of the universally good quality of the dataset, the images can also be used for anatomical or comparative morphology-related studies of adult structures.

  4. Teaching land-use planning in a flood prone area with an educational software

    NASA Astrophysics Data System (ADS)

    Metzger, R.; Jaboyedoff, M.

    2009-04-01

    Teaching of flood risk mapping and mitigation is a necessary task in geosciences studies. However, there is often a gap between the theoretical hydraulic notions broached during the courses and the possibility to make use of them in practice by the students during supervised computer lab exercises. This is mainly due because professional models/software have a steep learning curve and the lecturer spend most of his time to explain how to make such or such operation with the software. To overcome this shortcoming, an educational software was developed, which is made of three main modules: 1) A user-friendly graphical interface (GUI), allowing for handling geographical data and creating thematic maps (Geographical Information System (GIS) module); 2) A flood model (hydrological and inundation models) part allowing for freeing student as much as possible from the repetitive and tedious tasks related to modeling issues, while keeping reasonable computational time; 3) A land use planning module, which allow for specifying mitigation measures (dikes and levees building, flood retention, renaturation, …) and for evaluating their effects by re-running the flood model. The main goal of this educational software is to provide a smooth approach to the modeling issue, without loosing the focus on the main task which is flood risk reduction.

  5. Effects of Thermal Damage on Strain Burst Mechanism for Brittle Rocks Under True-Triaxial Loading Conditions

    NASA Astrophysics Data System (ADS)

    Akdag, Selahattin; Karakus, Murat; Taheri, Abbas; Nguyen, Giang; Manchao, He

    2018-06-01

    Strain burst is a common problem encountered in brittle rocks in deep, high-stress mining applications. Limited research focuses on the effects of temperature on the strain burst mechanism and the kinetic energies of rocks. This study aims to investigate the effects of thermal damage on the strain burst characteristics of brittle rocks under true-triaxial loading-unloading conditions using the acoustic emission (AE) and kinetic energy analyses. The time-domain and frequency-domain responses related to strain burst were studied, and the damage evolution was quantified by b-values, cumulative AE energy and events rates. The ejection velocities of the rock fragments from the free face of the granite specimens were used to calculate kinetic energies. The experimental results showed that thermal damage resulted in a delay in bursting but increased the bursting rate at 95% of normalised stress level. This is believed to be due to the micro-cracks induced by temperature exposure, and thus the accumulated AE energy (also supported by cumulative AE counts) at the initial loading stage was reduced, causing a delay in bursting. The strain burst stress, initial rock fragment ejection velocity, and kinetic energy decreased from room temperature (25 °C) to 100 °C, whereas they resulted in a gradual rise from 100 to 150 °C demonstrating more intense strain burst behaviour.

  6. NMR signature of evolution of ductile-to-brittle transition in bulk metallic glasses.

    PubMed

    Yuan, C C; Xiang, J F; Xi, X K; Wang, W H

    2011-12-02

    The mechanical properties of monolithic metallic glasses depend on the structures at atomic or subnanometer scales, while a clear correlation between mechanical behavior and structures has not been well established in such amorphous materials. In this work, we find a clear correlation of (27)Al NMR isotropic shifts with a microalloying induced ductile-to-brittle transition at ambient temperature in bulk metallic glasses, which indicates that the (27)Al NMR isotropic shift can be regarded as a structural signature to characterize plasticity for this metallic glass system. The study provides a compelling approach for investigating and understanding the mechanical properties of metallic glasses from the point of view of electronic structure. © 2011 American Physical Society

  7. Software Defined Radio with Parallelized Software Architecture

    NASA Technical Reports Server (NTRS)

    Heckler, Greg

    2013-01-01

    This software implements software-defined radio procession over multicore, multi-CPU systems in a way that maximizes the use of CPU resources in the system. The software treats each processing step in either a communications or navigation modulator or demodulator system as an independent, threaded block. Each threaded block is defined with a programmable number of input or output buffers; these buffers are implemented using POSIX pipes. In addition, each threaded block is assigned a unique thread upon block installation. A modulator or demodulator system is built by assembly of the threaded blocks into a flow graph, which assembles the processing blocks to accomplish the desired signal processing. This software architecture allows the software to scale effortlessly between single CPU/single-core computers or multi-CPU/multi-core computers without recompilation. NASA spaceflight and ground communications systems currently rely exclusively on ASICs or FPGAs. This software allows low- and medium-bandwidth (100 bps to approx.50 Mbps) software defined radios to be designed and implemented solely in C/C++ software, while lowering development costs and facilitating reuse and extensibility.

  8. Software Defined Radio with Parallelized Software Architecture

    NASA Technical Reports Server (NTRS)

    Heckler, Greg

    2013-01-01

    This software implements software-defined radio procession over multi-core, multi-CPU systems in a way that maximizes the use of CPU resources in the system. The software treats each processing step in either a communications or navigation modulator or demodulator system as an independent, threaded block. Each threaded block is defined with a programmable number of input or output buffers; these buffers are implemented using POSIX pipes. In addition, each threaded block is assigned a unique thread upon block installation. A modulator or demodulator system is built by assembly of the threaded blocks into a flow graph, which assembles the processing blocks to accomplish the desired signal processing. This software architecture allows the software to scale effortlessly between single CPU/single-core computers or multi-CPU/multi-core computers without recompilation. NASA spaceflight and ground communications systems currently rely exclusively on ASICs or FPGAs. This software allows low- and medium-bandwidth (100 bps to .50 Mbps) software defined radios to be designed and implemented solely in C/C++ software, while lowering development costs and facilitating reuse and extensibility.

  9. The pale brittle stem mushroom, Psathyrella candolleana (higher Basidiomycetes): an indigenous medicinal mushroom new to Iraq.

    PubMed

    Al-Habib, Mouthana N; Holliday, John C; Tura, Daniel

    2014-01-01

    The pale brittle stem mushroom, Psathyrella candolleana, a species new to Iraq, is described from the sub-arid region of Aljazira (Iraq). Both classical taxonomy and DNA analyses confirm the identification of the fungus strain (RM-0861) as P. candolleana, a species that belongs to the family Psatherellaceae known to possess medicinal properties. Being a saprophyte, this fungus is cultivatable in laboratory conditions and therefore shows potential for production and use as a medicinal mushroom in human and veterinary health.

  10. Three-Dimensional Dynamic Rupture in Brittle Solids and the Volumetric Strain Criterion

    NASA Astrophysics Data System (ADS)

    Uenishi, K.; Yamachi, H.

    2017-12-01

    As pointed out by Uenishi (2016 AGU Fall Meeting), source dynamics of ordinary earthquakes is often studied in the framework of 3D rupture in brittle solids but our knowledge of mechanics of actual 3D rupture is limited. Typically, criteria derived from 1D frictional observations of sliding materials or post-failure behavior of solids are applied in seismic simulations, and although mode-I cracks are frequently encountered in earthquake-induced ground failures, rupture in tension is in most cases ignored. Even when it is included in analyses, the classical maximum principal tensile stress rupture criterion is repeatedly used. Our recent basic experiments of dynamic rupture of spherical or cylindrical monolithic brittle solids by applying high-voltage electric discharge impulses or impact loads have indicated generation of surprisingly simple and often flat rupture surfaces in 3D specimens even without the initial existence of planes of weakness. However, at the same time, the snapshots taken by a high-speed digital video camera have shown rather complicated histories of rupture development in these 3D solid materials, which seem to be difficult to be explained by, for example, the maximum principal stress criterion. Instead, a (tensile) volumetric strain criterion where the volumetric strain (dilatation or the first invariant of the strain tensor) is a decisive parameter for rupture seems more effective in computationally reproducing the multi-directionally propagating waves and rupture. In this study, we try to show the connection between this volumetric strain criterion and other classical rupture criteria or physical parameters employed in continuum mechanics, and indicate that the criterion has, to some degree, physical meanings. First, we mathematically illustrate that the criterion is equivalent to a criterion based on the mean normal stress, a crucial parameter in plasticity. Then, we mention the relation between the volumetric strain criterion and the

  11. Overcoming Exclusion through Adult Learning.

    ERIC Educational Resources Information Center

    Nash, Ian; Walshe, John

    Strategies for overcoming exclusion through adult learning were identified through case studies of 19 initiatives in the following countries: Belgium; Mexico; the Netherlands; Norway; Portugal; and the United Kingdom. The study programs involved a diverse array of formal, nonformal, and informal public sector, community, and enterprise-based…

  12. OpenSQUID: A Flexible Open-Source Software Framework for the Control of SQUID Electronics

    DOE PAGES

    Jaeckel, Felix T.; Lafler, Randy J.; Boyd, S. T. P.

    2013-02-06

    We report commercially available computer-controlled SQUID electronics are usually delivered with software providing a basic user interface for adjustment of SQUID tuning parameters, such as bias current, flux offset, and feedback loop settings. However, in a research context it would often be useful to be able to modify this code and/or to have full control over all these parameters from researcher-written software. In the case of the STAR Cryoelectronics PCI/PFL family of SQUID control electronics, the supplied software contains modules for automatic tuning and noise characterization, but does not provide an interface for user code. On the other hand, themore » Magnicon SQUIDViewer software package includes a public application programming interface (API), but lacks auto-tuning and noise characterization features. To overcome these and other limitations, we are developing an "open-source" framework for controlling SQUID electronics which should provide maximal interoperability with user software, a unified user interface for electronics from different manufacturers, and a flexible platform for the rapid development of customized SQUID auto-tuning and other advanced features. Finally, we have completed a first implementation for the STAR Cryoelectronics hardware and have made the source code for this ongoing project available to the research community on SourceForge (http://opensquid.sourceforge.net) under the GNU public license.« less

  13. Application of FE software Elmer to the modeling of crustal-scale processes

    NASA Astrophysics Data System (ADS)

    Maierová, Petra; Guy, Alexandra; Lexa, Ondrej; Cadek, Ondrej

    2010-05-01

    We extended Elmer (the open source finite element software for multiphysical problems, http://www.csc.fi/english/pages/elmer) by user-written procedures for the two-dimensional modeling of crustal-scale processes. The standard version of Elmer is an appropriate tool for modeling of thermomechanical convection with non-linear viscous rheology. In geophysics, it might be suitable for some type of mantle convection modeling. Unlike the mantle, the crust is very heterogeneous. It consists of materials with distinct rheological properties that are subject to highly varied conditions: low pressure and temperature near the surface of the Earth and relatively high pressure and temperature at a depth of several tens of kilometers. Moreover, the deformation in the upper crust is mostly brittle and the strain is concentrated into narrow shear zones and thrusts. In order to simulate the brittle behavior of the crust, we implemented pressure-dependent visco-plastic rheology. The material heterogeneity and chemical convection is implemented in terms of active markers. Another special feature of the crust, the moving free surface, is already included in Elmer by means of a moving computational grid. Erosion can easily be added in this scheme. We tested the properties of our formulation of plastic flow on several numerical experiments simulating the deformation of material under compressional and extensional stresses. In the first step, we examined angles of shear zones that form in a plastically deforming material for different material parameters and grid resolutions. A more complex setting of "sandbox-type" experiments containing heterogeneous material, strain-softening and boundary friction was considered as a next testing case. To illustrate the abilities of the extended Elmer software in crustal deformation studies, we present two models of geological processes: diapirism of the lower crust and a channel flow forced by indentation. Both these processes are assumed to take

  14. Overcoming cellular barriers for RNA therapeutics.

    PubMed

    Dowdy, Steven F

    2017-03-01

    RNA-based therapeutics, such as small-interfering (siRNAs), microRNAs (miRNAs), antisense oligonucleotides (ASOs), aptamers, synthetic mRNAs and CRISPR-Cas9, have great potential to target a large part of the currently undruggable genes and gene products and to generate entirely new therapeutic paradigms in disease, ranging from cancer to pandemic influenza to Alzheimer's disease. However, for these RNA modalities to reach their full potential, they first need to overcome a billion years of evolutionary defenses that have kept RNAs on the outside of cells from invading the inside of cells. Overcoming the lipid bilayer to deliver RNA into cells has remained the major problem to solve for widespread development of RNA therapeutics, but recent chemistry advances have begun to penetrate this evolutionary armor.

  15. The relationships between software publications and software systems

    NASA Astrophysics Data System (ADS)

    Hogg, David W.

    2017-01-01

    When we build software systems or software tools for astronomy, we sometimes do and sometimes don't also write and publish standard scientific papers about those software systems. I will discuss the pros and cons of writing such publications. There are impacts of writing such papers immediately (they can affect the design and structure of the software project itself), in the short term (they can promote adoption and legitimize the software), in the medium term (they can provide a platform for all the literature's mechanisms for citation, criticism, and reuse), and in the long term (they can preserve ideas that are embodied in the software, possibly on timescales much longer than the lifetime of any software context). I will argue that as important as pure software contributions are to astronomy—and I am both a preacher and a practitioner—software contributions are even more valuable when they are associated with traditional scientific publications. There are exceptions and complexities of course, which I will discuss.

  16. Software Engineering Program: Software Process Improvement Guidebook

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The purpose of this document is to provide experience-based guidance in implementing a software process improvement program in any NASA software development or maintenance community. This guidebook details how to define, operate, and implement a working software process improvement program. It describes the concept of the software process improvement program and its basic organizational components. It then describes the structure, organization, and operation of the software process improvement program, illustrating all these concepts with specific NASA examples. The information presented in the document is derived from the experiences of several NASA software organizations, including the SEL, the SEAL, and the SORCE. Their experiences reflect many of the elements of software process improvement within NASA. This guidebook presents lessons learned in a form usable by anyone considering establishing a software process improvement program within his or her own environment. This guidebook attempts to balance general and detailed information. It provides material general enough to be usable by NASA organizations whose characteristics do not directly match those of the sources of the information and models presented herein. It also keeps the ideas sufficiently close to the sources of the practical experiences that have generated the models and information.

  17. Spectral Knowledge (SK-UTALCA): Software for Exploratory Analysis of High-Resolution Spectral Reflectance Data on Plant Breeding.

    PubMed

    Lobos, Gustavo A; Poblete-Echeverría, Carlos

    2016-01-01

    This article describes public, free software that provides efficient exploratory analysis of high-resolution spectral reflectance data. Spectral reflectance data can suffer from problems such as poor signal to noise ratios in various wavebands or invalid measurements due to changes in incoming solar radiation or operator fatigue leading to poor orientation of sensors. Thus, exploratory data analysis is essential to identify appropriate data for further analyses. This software overcomes the problem that analysis tools such as Excel are cumbersome to use for the high number of wavelengths and samples typically acquired in these studies. The software, Spectral Knowledge (SK-UTALCA), was initially developed for plant breeding, but it is also suitable for other studies such as precision agriculture, crop protection, ecophysiology plant nutrition, and soil fertility. Various spectral reflectance indices (SRIs) are often used to relate crop characteristics to spectral data and the software is loaded with 255 SRIs which can be applied quickly to the data. This article describes the architecture and functions of SK-UTALCA and the features of the data that led to the development of each of its modules.

  18. Software development for the analysis of heartbeat sounds with LabVIEW in diagnosis of cardiovascular disease.

    PubMed

    Topal, Taner; Polat, Hüseyin; Güler, Inan

    2008-10-01

    In this paper, a time-frequency spectral analysis software (Heart Sound Analyzer) for the computer-aided analysis of cardiac sounds has been developed with LabVIEW. Software modules reveal important information for cardiovascular disorders, it can also assist to general physicians to come up with more accurate and reliable diagnosis at early stages. Heart sound analyzer (HSA) software can overcome the deficiency of expert doctors and help them in rural as well as urban clinics and hospitals. HSA has two main blocks: data acquisition and preprocessing, time-frequency spectral analyses. The heart sounds are first acquired using a modified stethoscope which has an electret microphone in it. Then, the signals are analysed using the time-frequency/scale spectral analysis techniques such as STFT, Wigner-Ville distribution and wavelet transforms. HSA modules have been tested with real heart sounds from 35 volunteers and proved to be quite efficient and robust while dealing with a large variety of pathological conditions.

  19. Fracturing and Transformation Into Veins Beneath the Crustal Scale Brittle Ductile Transition - a Record of Co-seismic Loading and Post-seismic Relaxation

    NASA Astrophysics Data System (ADS)

    Nüchter, J. A.; Stöckhert, B.

    2005-12-01

    Metamorphic rocks approaching the crustal scale brittle-ductile transition (BDT) during exhumation are expected to become increasingly affected by short term stress fluctuations related to seismic activity in the overlying seismogenic layer (schizosphere), while still residing in a long-term viscous environment (plastosphere). The structural and microstructural record of quartz veins in low grade - high pressure metamorphic rocks from southern Evia, Greece, yields insight into the processes and conditions just beneath the long-term BDT at temperatures of about 300 to 350°C, which switches between brittle failure and viscous flow as a function of imposed stress or strain rate. The following features are characteristic: (1) The veins have formed from tensile fractures, with a typical length on the order of 10-1 to 101 m; (2) The veins are discordant with respect to foliation and all pre-existing structures, with a uniform orientation over more than 500 km2; (3) The veins show a low aspect ratio of about 10 to 100 and an irregular or characteristic flame shape, which requires distributed ductile deformation of the host rock; (4) Fabrics of the sealing vein quartz indicate that - at a time - the veins were wide open cavities; (5) The sealing quartz crystals reveal a broad spectrum of microstructural features indicative of crystal plastic deformation at high stress and temperatures of about 300 to 350°C. These features indicate that opening and sealing of the fractures commenced immediately after brittle failure, controlled by ductile deformation of the host rock. Vein-parallel shortening was generally less than about 2%. Crystals formed early during sealing were plastically deformed upon progressive deformation and opening of the vein. The structural and microstructural record is interpreted as follows: Brittle failure is proposed to be a consequence of short term co-seismic loading. Subsequent opening of the fracture and sealing to become a vein is interpreted to

  20. Battling Brittle Bones

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The accuDEXA(R) Bone Mineral Density Assessment System, manufactured by Schick Technologies, Inc., utilizes "camera on a chip" sensor technology invented and developed by NASA's Jet Propulsion Laboratory. Schick's accuDEXA system offers several advantages over traditional osteoporosis tests, which assess bone density loss in the hip and spine, and require specialized personnel to conduct. With accuDEXA, physicians can test the entire body's bone density at a peripheral site, such as the finger, without applying gels or having patients remove garments. Results are achieved in 30 seconds and printed out in less than a minute, compared to the estimated exam time of 15 minutes for hip and spine density analyses. Schick has also applied the CMOS APS technology to a new software product that performs dental radiography using up to 90 percent less radiation exposure than conventional X-rays. Called Computed Dental Radiography(R), the new digital imaging product utilizes an electronic sensor in place of X-ray film to generate sharp and clear images that appear on a computer screen within 3 seconds, and can be enlarged and enhanced to identify problems.

  1. Fault-slip inversions: Their importance in terms of strain, heterogeneity, and kinematics of brittle deformation

    NASA Astrophysics Data System (ADS)

    Riller, U.; Clark, M. D.; Daxberger, H.; Doman, D.; Lenauer, I.; Plath, S.; Santimano, T.

    2017-08-01

    Heterogeneous deformation is intrinsic in natural deformation, but often underestimated in the analysis and interpretation of mesoscopic brittle shear faults. Based on the analysis of 11,222 faults from two distinct tectonic settings, the Central Andes in Argentina and the Sudbury area in Canada, interpolation of principal strain directions and scaled analogue modelling, we revisit controversial issues of fault-slip inversions, collectively adhering to heterogeneous deformation. These issues include the significance of inversion solutions in terms of (1) strain or paleo-stress; (2) displacement, notably plate convergence; (3) local versus far-field deformation; (4) strain perturbations and (5) spacing between stations of fault-slip data acquisition. Furthermore, we highlight the value of inversions for identifying the kinematics of master fault zones in the absence of displaced geological markers. A key result of our assessment is that fault-slip inversions relate to local strain, not paleo-stress, and thus can aid in inferring, the kinematics of master faults. Moreover, strain perturbations caused by mechanical anomalies of the deforming upper crust significantly influence local principal strain directions. Thus, differently oriented principal strain axes inferred from fault-slip inversions in a given region may not point to regional deformation caused by successive and distinct deformation regimes. This outcome calls into question the common practice of separating heterogeneous fault-slip data sets into apparently homogeneous subsets. Finally, the fact that displacement vectors and principal strains are rarely co-linear defies the use of brittle fault data as proxy for estimating directions of plate-scale motions.

  2. ScaffoldSeq: Software for characterization of directed evolution populations.

    PubMed

    Woldring, Daniel R; Holec, Patrick V; Hackel, Benjamin J

    2016-07-01

    ScaffoldSeq is software designed for the numerous applications-including directed evolution analysis-in which a user generates a population of DNA sequences encoding for partially diverse proteins with related functions and would like to characterize the single site and pairwise amino acid frequencies across the population. A common scenario for enzyme maturation, antibody screening, and alternative scaffold engineering involves naïve and evolved populations that contain diversified regions, varying in both sequence and length, within a conserved framework. Analyzing the diversified regions of such populations is facilitated by high-throughput sequencing platforms; however, length variability within these regions (e.g., antibody CDRs) encumbers the alignment process. To overcome this challenge, the ScaffoldSeq algorithm takes advantage of conserved framework sequences to quickly identify diverse regions. Beyond this, unintended biases in sequence frequency are generated throughout the experimental workflow required to evolve and isolate clones of interest prior to DNA sequencing. ScaffoldSeq software uniquely handles this issue by providing tools to quantify and remove background sequences, cluster similar protein families, and dampen the impact of dominant clones. The software produces graphical and tabular summaries for each region of interest, allowing users to evaluate diversity in a site-specific manner as well as identify epistatic pairwise interactions. The code and detailed information are freely available at http://research.cems.umn.edu/hackel. Proteins 2016; 84:869-874. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  3. Semantic Entity-Component State Management Techniques to Enhance Software Quality for Multimodal VR-Systems.

    PubMed

    Fischbach, Martin; Wiebusch, Dennis; Latoschik, Marc Erich

    2017-04-01

    Modularity, modifiability, reusability, and API usability are important software qualities that determine the maintainability of software architectures. Virtual, Augmented, and Mixed Reality (VR, AR, MR) systems, modern computer games, as well as interactive human-robot systems often include various dedicated input-, output-, and processing subsystems. These subsystems collectively maintain a real-time simulation of a coherent application state. The resulting interdependencies between individual state representations, mutual state access, overall synchronization, and flow of control implies a conceptual close coupling whereas software quality asks for a decoupling to develop maintainable solutions. This article presents five semantics-based software techniques that address this contradiction: Semantic grounding, code from semantics, grounded actions, semantic queries, and decoupling by semantics. These techniques are applied to extend the well-established entity-component-system (ECS) pattern to overcome some of this pattern's deficits with respect to the implied state access. A walk-through of central implementation aspects of a multimodal (speech and gesture) VR-interface is used to highlight the techniques' benefits. This use-case is chosen as a prototypical example of complex architectures with multiple interacting subsystems found in many VR, AR and MR architectures. Finally, implementation hints are given, lessons learned regarding maintainability pointed-out, and performance implications discussed.

  4. The development of a multi-target compiler-writing system for flight software development

    NASA Technical Reports Server (NTRS)

    Feyock, S.; Donegan, M. K.

    1977-01-01

    A wide variety of systems designed to assist the user in the task of writing compilers has been developed. A survey of these systems reveals that none is entirely appropriate to the purposes of the MUST project, which involves the compilation of one or at most a small set of higher-order languages to a wide variety of target machines offering little or no software support. This requirement dictates that any compiler writing system employed must provide maximal support in the areas of semantics specification and code generation, the areas in which existing compiler writing systems as well as theoretical underpinnings are weakest. This paper describes an ongoing research and development effort to create a compiler writing system which will overcome these difficulties, thus providing a software system which makes possible the fast, trouble-free creation of reliable compilers for a wide variety of target computers.

  5. Wildlife software: procedures for publication of computer software

    USGS Publications Warehouse

    Samuel, M.D.

    1990-01-01

    Computers and computer software have become an integral part of the practice of wildlife science. Computers now play an important role in teaching, research, and management applications. Because of the specialized nature of wildlife problems, specific computer software is usually required to address a given problem (e.g., home range analysis). This type of software is not usually available from commercial vendors and therefore must be developed by those wildlife professionals with particular skill in computer programming. Current journal publication practices generally prevent a detailed description of computer software associated with new techniques. In addition, peer review of journal articles does not usually include a review of associated computer software. Thus, many wildlife professionals are usually unaware of computer software that would meet their needs or of major improvements in software they commonly use. Indeed most users of wildlife software learn of new programs or important changes only by word of mouth.

  6. Linking megathrust earthquakes to brittle deformation in a fossil accretionary complex

    PubMed Central

    Dielforder, Armin; Vollstaedt, Hauke; Vennemann, Torsten; Berger, Alfons; Herwegh, Marco

    2015-01-01

    Seismological data from recent subduction earthquakes suggest that megathrust earthquakes induce transient stress changes in the upper plate that shift accretionary wedges into an unstable state. These stress changes have, however, never been linked to geological structures preserved in fossil accretionary complexes. The importance of coseismically induced wedge failure has therefore remained largely elusive. Here we show that brittle faulting and vein formation in the palaeo-accretionary complex of the European Alps record stress changes generated by subduction-related earthquakes. Early veins formed at shallow levels by bedding-parallel shear during coseismic compression of the outer wedge. In contrast, subsequent vein formation occurred by normal faulting and extensional fracturing at deeper levels in response to coseismic extension of the inner wedge. Our study demonstrates how mineral veins can be used to reveal the dynamics of outer and inner wedges, which respond in opposite ways to megathrust earthquakes by compressional and extensional faulting, respectively. PMID:26105966

  7. Space Flight Software Development Software for Intelligent System Health Management

    NASA Technical Reports Server (NTRS)

    Trevino, Luis C.; Crumbley, Tim

    2004-01-01

    The slide presentation examines the Marshall Space Flight Center Flight Software Branch, including software development projects, mission critical space flight software development, software technical insight, advanced software development technologies, and continuous improvement in the software development processes and methods.

  8. Self-similar crack-generation effects in the fracture process in brittle materials

    NASA Astrophysics Data System (ADS)

    Hilarov, V. L.

    1998-07-01

    Using acoustic-emission data banks we have computed time and space correlation functions for the purpose of investigation of crack-propagation self-similarity during the fracture process in brittle materials. It is shown that the whole fracture process may be represented as a two-stage process. In the first stage, the crack propagation is uniform and uncorrelated in space, having a time spectral density of the white-noise type and a correlation fractal dimension approximately equal to that of 3D Euclidean space. In the second stage, this fractal dimension decreases significantly, reaching the value of 2.2-2.4, characteristic for the fracture surfaces, while the time spectral density exhibits a significant low-frequency increase becoming of 0965-0393/6/4/002/img1-noise type. The resulting fractal shows no multifractal behaviour, appearing to be a single fractal.

  9. Software for Generating Troposphere Corrections for InSAR Using GPS and Weather Model Data

    NASA Technical Reports Server (NTRS)

    Moore, Angelyn W.; Webb, Frank H.; Fishbein, Evan F.; Fielding, Eric J.; Owen, Susan E.; Granger, Stephanie L.; Bjoerndahl, Fredrik; Loefgren, Johan; Fang, Peng; Means, James D.; hide

    2013-01-01

    Atmospheric errors due to the troposphere are a limiting error source for spaceborne interferometric synthetic aperture radar (InSAR) imaging. This software generates tropospheric delay maps that can be used to correct atmospheric artifacts in InSAR data. The software automatically acquires all needed GPS (Global Positioning System), weather, and Digital Elevation Map data, and generates a tropospheric correction map using a novel algorithm for combining GPS and weather information while accounting for terrain. Existing JPL software was prototypical in nature, required a MATLAB license, required additional steps to acquire and ingest needed GPS and weather data, and did not account for topography in interpolation. Previous software did not achieve a level of automation suitable for integration in a Web portal. This software overcomes these issues. GPS estimates of tropospheric delay are a source of corrections that can be used to form correction maps to be applied to InSAR data, but the spacing of GPS stations is insufficient to remove short-wavelength tropospheric artifacts. This software combines interpolated GPS delay with weather model precipitable water vapor (PWV) and a digital elevation model to account for terrain, increasing the spatial resolution of the tropospheric correction maps and thus removing short wavelength tropospheric artifacts to a greater extent. It will be integrated into a Web portal request system, allowing use in a future L-band SAR Earth radar mission data system. This will be a significant contribution to its technology readiness, building on existing investments in in situ space geodetic networks, and improving timeliness, quality, and science value of the collected data

  10. Software attribute visualization for high integrity software

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pollock, G.M.

    1998-03-01

    This report documents a prototype tool developed to investigate the use of visualization and virtual reality technologies for improving software surety confidence. The tool is utilized within the execution phase of the software life cycle. It provides a capability to monitor an executing program against prespecified requirements constraints provided in a program written in the requirements specification language SAGE. The resulting Software Attribute Visual Analysis Tool (SAVAnT) also provides a technique to assess the completeness of a software specification.

  11. DVS-SOFTWARE: An Effective Tool for Applying Highly Parallelized Hardware To Computational Geophysics

    NASA Astrophysics Data System (ADS)

    Herrera, I.; Herrera, G. S.

    2015-12-01

    Most geophysical systems are macroscopic physical systems. The behavior prediction of such systems is carried out by means of computational models whose basic models are partial differential equations (PDEs) [1]. Due to the enormous size of the discretized version of such PDEs it is necessary to apply highly parallelized super-computers. For them, at present, the most efficient software is based on non-overlapping domain decomposition methods (DDM). However, a limiting feature of the present state-of-the-art techniques is due to the kind of discretizations used in them. Recently, I. Herrera and co-workers using 'non-overlapping discretizations' have produced the DVS-Software which overcomes this limitation [2]. The DVS-software can be applied to a great variety of geophysical problems and achieves very high parallel efficiencies (90%, or so [3]). It is therefore very suitable for effectively applying the most advanced parallel supercomputers available at present. In a parallel talk, in this AGU Fall Meeting, Graciela Herrera Z. will present how this software is being applied to advance MOD-FLOW. Key Words: Parallel Software for Geophysics, High Performance Computing, HPC, Parallel Computing, Domain Decomposition Methods (DDM)REFERENCES [1]. Herrera Ismael and George F. Pinder, Mathematical Modelling in Science and Engineering: An axiomatic approach", John Wiley, 243p., 2012. [2]. Herrera, I., de la Cruz L.M. and Rosas-Medina A. "Non Overlapping Discretization Methods for Partial, Differential Equations". NUMER METH PART D E, 30: 1427-1454, 2014, DOI 10.1002/num 21852. (Open source) [3]. Herrera, I., & Contreras Iván "An Innovative Tool for Effectively Applying Highly Parallelized Software To Problems of Elasticity". Geofísica Internacional, 2015 (In press)

  12. Software cost/resource modeling: Software quality tradeoff measurement

    NASA Technical Reports Server (NTRS)

    Lawler, R. W.

    1980-01-01

    A conceptual framework for treating software quality from a total system perspective is developed. Examples are given to show how system quality objectives may be allocated to hardware and software; to illustrate trades among quality factors, both hardware and software, to achieve system performance objectives; and to illustrate the impact of certain design choices on software functionality.

  13. Software system safety

    NASA Technical Reports Server (NTRS)

    Uber, James G.

    1988-01-01

    Software itself is not hazardous, but since software and hardware share common interfaces there is an opportunity for software to create hazards. Further, these software systems are complex, and proven methods for the design, analysis, and measurement of software safety are not yet available. Some past software failures, future NASA software trends, software engineering methods, and tools and techniques for various software safety analyses are reviewed. Recommendations to NASA are made based on this review.

  14. Open core control software for surgical robots.

    PubMed

    Arata, Jumpei; Kozuka, Hiroaki; Kim, Hyung Wook; Takesue, Naoyuki; Vladimirov, B; Sakaguchi, Masamichi; Tokuda, Junichi; Hata, Nobuhiko; Chinzei, Kiyoyuki; Fujimoto, Hideo

    2010-05-01

    In these days, patients and doctors in operation room are surrounded by many medical devices as resulting from recent advancement of medical technology. However, these cutting-edge medical devices are working independently and not collaborating with each other, even though the collaborations between these devices such as navigation systems and medical imaging devices are becoming very important for accomplishing complex surgical tasks (such as a tumor removal procedure while checking the tumor location in neurosurgery). On the other hand, several surgical robots have been commercialized, and are becoming common. However, these surgical robots are not open for collaborations with external medical devices in these days. A cutting-edge "intelligent surgical robot" will be possible in collaborating with surgical robots, various kinds of sensors, navigation system and so on. On the other hand, most of the academic software developments for surgical robots are "home-made" in their research institutions and not open to the public. Therefore, open source control software for surgical robots can be beneficial in this field. From these perspectives, we developed Open Core Control software for surgical robots to overcome these challenges. In general, control softwares have hardware dependencies based on actuators, sensors and various kinds of internal devices. Therefore, these control softwares cannot be used on different types of robots without modifications. However, the structure of the Open Core Control software can be reused for various types of robots by abstracting hardware dependent parts. In addition, network connectivity is crucial for collaboration between advanced medical devices. The OpenIGTLink is adopted in Interface class which plays a role to communicate with external medical devices. At the same time, it is essential to maintain the stable operation within the asynchronous data transactions through network. In the Open Core Control software, several

  15. Open core control software for surgical robots

    PubMed Central

    Kozuka, Hiroaki; Kim, Hyung Wook; Takesue, Naoyuki; Vladimirov, B.; Sakaguchi, Masamichi; Tokuda, Junichi; Hata, Nobuhiko; Chinzei, Kiyoyuki; Fujimoto, Hideo

    2010-01-01

    Object In these days, patients and doctors in operation room are surrounded by many medical devices as resulting from recent advancement of medical technology. However, these cutting-edge medical devices are working independently and not collaborating with each other, even though the collaborations between these devices such as navigation systems and medical imaging devices are becoming very important for accomplishing complex surgical tasks (such as a tumor removal procedure while checking the tumor location in neurosurgery). On the other hand, several surgical robots have been commercialized, and are becoming common. However, these surgical robots are not open for collaborations with external medical devices in these days. A cutting-edge “intelligent surgical robot” will be possible in collaborating with surgical robots, various kinds of sensors, navigation system and so on. On the other hand, most of the academic software developments for surgical robots are “home-made” in their research institutions and not open to the public. Therefore, open source control software for surgical robots can be beneficial in this field. From these perspectives, we developed Open Core Control software for surgical robots to overcome these challenges. Materials and methods In general, control softwares have hardware dependencies based on actuators, sensors and various kinds of internal devices. Therefore, these control softwares cannot be used on different types of robots without modifications. However, the structure of the Open Core Control software can be reused for various types of robots by abstracting hardware dependent parts. In addition, network connectivity is crucial for collaboration between advanced medical devices. The OpenIGTLink is adopted in Interface class which plays a role to communicate with external medical devices. At the same time, it is essential to maintain the stable operation within the asynchronous data transactions through network. In the Open

  16. SAMPA: A free software tool for skin and membrane permeation data analysis.

    PubMed

    Bezrouk, Aleš; Fiala, Zdeněk; Kotingová, Lenka; Krulichová, Iva Selke; Kopečná, Monika; Vávrová, Kateřina

    2017-10-01

    Skin and membrane permeation experiments comprise an important step in the development of a transdermal or topical formulation or toxicological risk assessment. The standard method for analyzing these data relies on the linear part of a permeation profile. However, it is difficult to objectively determine when the profile becomes linear, or the experiment duration may be insufficient to reach a maximum or steady state. Here, we present a software tool for Skin And Membrane Permeation data Analysis, SAMPA, that is easy to use and overcomes several of these difficulties. The SAMPA method and software have been validated on in vitro and in vivo permeation data on human, pig and rat skin and model stratum corneum lipid membranes using compounds that range from highly lipophilic polycyclic aromatic hydrocarbons to highly hydrophilic antiviral drug, with and without two permeation enhancers. The SAMPA performance was compared with the standard method using a linear part of the permeation profile and a complex mathematical model. SAMPA is a user-friendly, open-source software tool for analyzing the data obtained from skin and membrane permeation experiments. It runs on a Microsoft Windows platform and is freely available as a Supporting file to this article. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. A Maxwell elasto-brittle rheology for sea ice modelling

    NASA Astrophysics Data System (ADS)

    Dansereau, Véronique; Weiss, Jérôme; Saramito, Pierre; Lattes, Philippe

    2016-07-01

    A new rheological model is developed that builds on an elasto-brittle (EB) framework used for sea ice and rock mechanics, with the intent of representing both the small elastic deformations associated with fracturing processes and the larger deformations occurring along the faults/leads once the material is highly damaged and fragmented. A viscous-like relaxation term is added to the linear-elastic constitutive law together with an effective viscosity that evolves according to the local level of damage of the material, like its elastic modulus. The coupling between the level of damage and both mechanical parameters is such that within an undamaged ice cover the viscosity is infinitely large and deformations are strictly elastic, while along highly damaged zones the elastic modulus vanishes and most of the stress is dissipated through permanent deformations. A healing mechanism is also introduced, counterbalancing the effects of damaging over large timescales. In this new model, named Maxwell-EB after the Maxwell rheology, the irreversible and reversible deformations are solved for simultaneously; hence drift velocities are defined naturally. First idealized simulations without advection show that the model reproduces the main characteristics of sea ice mechanics and deformation: strain localization, anisotropy, intermittency and associated scaling laws.

  18. First year of ALMA site software deployment: where everything comes together

    NASA Astrophysics Data System (ADS)

    González, Víctor; Mora, Matias; Araya, Rodrigo; Arredondo, Diego; Bartsch, Marcelo; Burgos, Pablo; Ibsen, Jorge; Reveco, Johnny; Sáez, Norman; Schemrl, Anton; Sepulveda, Jorge; Shen, Tzu-Chiang; Soto, Rubén; Troncoso, Nicolás; Zambrano, Mauricio; Barriga, Nicolás; Glendenning, Brian; Raffi, Gianni; Kern, Jeff

    2010-07-01

    Starting 2009, the ALMA project initiated one of its most exciting phases within construction: the first antenna from one of the vendors was delivered to the Assembly, Integration and Verification team. With this milestone and the closure of the ALMA Test Facility in New Mexico, the JAO Computing Group in Chile found itself in the front line of the project's software deployment and integration effort. Among the group's main responsibilities are the deployment, configuration and support of the observation systems, in addition to infrastructure administration, all of which needs to be done in close coordination with the development groups in Europe, North America and Japan. Software support has been the primary interaction key with the current users (mainly scientists, operators and hardware engineers), as the software is normally the most visible part of the system. During this first year of work with the production hardware, three consecutive software releases have been deployed and commissioned. Also, the first three antennas have been moved to the Array Operations Site, at 5.000 meters elevation, and the complete end-to-end system has been successfully tested. This paper shares the experience of this 15-people group as part of the construction team at the ALMA site, and working together with Computing IPT, on the achievements and problems overcomed during this period. It explores the excellent results of teamwork, and also some of the troubles that such a complex and geographically distributed project can run into. Finally, it approaches the challenges still to come, with the transition to the ALMA operations plan.

  19. The Feasibility of the Use of E-Books for Replacing Lost or Brittle Books in the Kent State University Library.

    ERIC Educational Resources Information Center

    Lareau, Susan

    This study examined the feasibility of ordering an e-book (electronic book) to replace a lost or brittle book in the Kent State University (Ohio) library. The study checked a representative sample of 234 books lost during July to December 2000 to see the availability of the book in e-form, as well as the cost of the print versus the e-book…

  20. Avoidable Software Procurements

    DTIC Science & Technology

    2012-09-01

    software license, software usage, ELA, Software as a Service , SaaS , Software Asset...PaaS Platform as a Service SaaS Software as a Service SAM Software Asset Management SMS System Management Server SEWP Solutions for Enterprise Wide...delivery of full Cloud Services , we will see the transition of the Cloud Computing service model from Iaas to SaaS , or Software as a Service . Software

  1. Forced-rupture of cell-adhesion complexes reveals abrupt switch between two brittle states

    NASA Astrophysics Data System (ADS)

    Toan, Ngo Minh; Thirumalai, D.

    2018-03-01

    Cell adhesion complexes (CACs), which are activated by ligand binding, play key roles in many cellular functions ranging from cell cycle regulation to mediation of cell extracellular matrix adhesion. Inspired by single molecule pulling experiments using atomic force spectroscopy on leukocyte function-associated antigen-1 (LFA-1), expressed in T-cells, bound to intercellular adhesion molecules (ICAM), we performed constant loading rate (rf) and constant force (F) simulations using the self-organized polymer model to describe the mechanism of ligand rupture from CACs. The simulations reproduce the major experimental finding on the kinetics of the rupture process, namely, the dependence of the most probable rupture forces (f*s) on ln rf (rf is the loading rate) exhibits two distinct linear regimes. The first, at low rf, has a shallow slope, whereas the slope at high rf is much larger, especially for a LFA-1/ICAM-1 complex with the transition between the two occurring over a narrow rf range. Locations of the two transition states (TSs) extracted from the simulations show an abrupt change from a high value at low rf or constant force, F, to a low value at high rf or F. This unusual behavior in which the CACs switch from one brittle (TS position is a constant over a range of forces) state to another brittle state is not found in forced-rupture in other protein complexes. We explain this novel behavior by constructing the free energy profiles, F(Λ)s, as a function of a collective reaction coordinate (Λ), involving many key charged residues and a critical metal ion (Mg2+). The TS positions in F(Λ), which quantitatively agree with the parameters extracted using the Bell-Evans model, change abruptly at a critical force, demonstrating that it, rather than the molecular extension, is a good reaction coordinate. Our combined analyses using simulations performed in both the pulling modes (constant rf and F) reveal a new mechanism for the two loading regimes observed in the

  2. Brittle-viscous deformation of vein quartz under fluid-rich lower greenschist facies conditions

    NASA Astrophysics Data System (ADS)

    Kjøll, H. J.; Viola, G.; Menegon, L.; Sørensen, B. E.

    2015-06-01

    We studied by Electron BackScatter Diffraction (EBSD) and optical microscopy a coarse-grained (ca. 0.5-6 mm) quartz vein embedded in a phyllonitic matrix to gain insights into the recrystallization mechanisms and the processes of strain localization in quartz deformed under lower greenschist facies conditions, broadly coincident with the brittle-viscous transition. The vein deformed during faulting along a phyllonitic thrust of Caledonian age within the Porsa Imbricate Stack in the Paleoproterozoic Repparfjord Tectonic Window in northern Norway. The phyllonite hosting the vein formed at the expense of a metabasaltic protolith through feldspar breakdown to form interconnected layers of fine, synkinematic phyllosilicates. In the mechanically weak framework of the phyllonite, the quartz vein acted as a relatively rigid body. Viscous deformation in the vein was initially accommodated by quartz basal slip. Under the prevailing deformation conditions, however, dislocation glide- and possibly creep-accommodated deformation of quartz was inefficient, and this resulted in localized strain hardening. In response to the (1) hardening, (2) progressive and cyclic increase of the fluid pressure, and (3) increasing competence contrast between the vein and the weakly foliated host phyllonite, vein quartz crystals began to deform by brittle processes along specific, suitably oriented lattice planes, creating microgouges along microfractures. Nucleated new grains rapidly sealed these fractures as fluids penetrated the actively deforming system. The grains grew initially by solution precipitation and later by grain boundary migration. We suggest that the different initial orientation of the vein crystals led to strain accommodation by different mechanisms in the individual crystals, generating remarkably different microstructures. Crystals suitably oriented for basal slip, for example, accommodated strain mainly viscously and experienced only minor fracturing. Instead, crystals

  3. Quasi-Brittle Fracture of Compact Specimens with Sharp Notches and U-Shaped Cuts

    NASA Astrophysics Data System (ADS)

    Kornev, V. M.; Demeshkin, A. G.

    2018-01-01

    A two-parameter (coupled) discrete-integral criterion of fracture is proposed. It can be used to construct fracture diagrams for compact specimens with sharp cracks. Curves separating the stress-crack length plane into three domains are plotted. These domains correspond to the absence of fracture, damage accumulation in the pre-fracture region under repeated loading, and specimen fragmentation under monotonic loading. Constants used for the analytical description of fracture diagrams for quasi-brittle materials with cracks are selected with the use of approximation of the classical stress-strain diagrams for the initial material and the critical stress intensity factor. Predictions of the proposed theory are compared with experimental results on fracture of compact specimens with different radii made of polymethylmethacrylate (PMMA) and solid rubber with crack-type effects in the form of U-shaped cuts.

  4. Effectiveness of an automatic tracking software in underwater motion analysis.

    PubMed

    Magalhaes, Fabrício A; Sawacha, Zimi; Di Michele, Rocco; Cortesi, Matteo; Gatta, Giorgio; Fantozzi, Silvia

    2013-01-01

    supervision, thus allowing short processing time.When tracking underwater movements, the degree of automation of the tracking procedure is influenced by the capability of the algorithm to overcome difficulties linked to the small target size, the low image quality and the presence of background clutters.The newly developed feature-tracking algorithm has shown a good automatic tracking effectiveness in underwater motion analysis with significantly smaller percentage of required manual interventions when compared to a commercial software.

  5. Secure software practices among Malaysian software practitioners: An exploratory study

    NASA Astrophysics Data System (ADS)

    Mohamed, Shafinah Farvin Packeer; Baharom, Fauziah; Deraman, Aziz; Yahya, Jamaiah; Mohd, Haslina

    2016-08-01

    Secure software practices is increasingly gaining much importance among software practitioners and researchers due to the rise of computer crimes in the software industry. It has become as one of the determinant factors for producing high quality software. Even though its importance has been revealed, its current practice in the software industry is still scarce, particularly in Malaysia. Thus, an exploratory study is conducted among software practitioners in Malaysia to study their experiences and practices in the real-world projects. This paper discusses the findings from the study, which involved 93 software practitioners. Structured questionnaire is utilized for data collection purpose whilst statistical methods such as frequency, mean, and cross tabulation are used for data analysis. Outcomes from this study reveal that software practitioners are becoming increasingly aware on the importance of secure software practices, however, they lack of appropriate implementation, which could affect the quality of produced software.

  6. Software For Computing Reliability Of Other Software

    NASA Technical Reports Server (NTRS)

    Nikora, Allen; Antczak, Thomas M.; Lyu, Michael

    1995-01-01

    Computer Aided Software Reliability Estimation (CASRE) computer program developed for use in measuring reliability of other software. Easier for non-specialists in reliability to use than many other currently available programs developed for same purpose. CASRE incorporates mathematical modeling capabilities of public-domain Statistical Modeling and Estimation of Reliability Functions for Software (SMERFS) computer program and runs in Windows software environment. Provides menu-driven command interface; enabling and disabling of menu options guides user through (1) selection of set of failure data, (2) execution of mathematical model, and (3) analysis of results from model. Written in C language.

  7. 75 FR 58347 - Information Collection; Overcoming Barriers to Wildland Fire Defensible Space Behaviors

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-24

    ... Information Collection; Overcoming Barriers to Wildland Fire Defensible Space Behaviors AGENCY: Forest Service... new information collection, Overcoming Barriers to Wildland Fire Defensible Space Behaviors. DATES... time, Monday through Friday. SUPPLEMENTARY INFORMATION: Title: Overcoming Barriers to Wildland Fire...

  8. Spectral Knowledge (SK-UTALCA): Software for Exploratory Analysis of High-Resolution Spectral Reflectance Data on Plant Breeding

    PubMed Central

    Lobos, Gustavo A.; Poblete-Echeverría, Carlos

    2017-01-01

    This article describes public, free software that provides efficient exploratory analysis of high-resolution spectral reflectance data. Spectral reflectance data can suffer from problems such as poor signal to noise ratios in various wavebands or invalid measurements due to changes in incoming solar radiation or operator fatigue leading to poor orientation of sensors. Thus, exploratory data analysis is essential to identify appropriate data for further analyses. This software overcomes the problem that analysis tools such as Excel are cumbersome to use for the high number of wavelengths and samples typically acquired in these studies. The software, Spectral Knowledge (SK-UTALCA), was initially developed for plant breeding, but it is also suitable for other studies such as precision agriculture, crop protection, ecophysiology plant nutrition, and soil fertility. Various spectral reflectance indices (SRIs) are often used to relate crop characteristics to spectral data and the software is loaded with 255 SRIs which can be applied quickly to the data. This article describes the architecture and functions of SK-UTALCA and the features of the data that led to the development of each of its modules. PMID:28119705

  9. Software Design Improvements. Part 1; Software Benefits and Limitations

    NASA Technical Reports Server (NTRS)

    Lalli, Vincent R.; Packard, Michael H.; Ziemianski, Tom

    1997-01-01

    Computer hardware and associated software have been used for many years to process accounting information, to analyze test data and to perform engineering analysis. Now computers and software also control everything from automobiles to washing machines and the number and type of applications are growing at an exponential rate. The size of individual program has shown similar growth. Furthermore, software and hardware are used to monitor and/or control potentially dangerous products and safety-critical systems. These uses include everything from airplanes and braking systems to medical devices and nuclear plants. The question is: how can this hardware and software be made more reliable? Also, how can software quality be improved? What methodology needs to be provided on large and small software products to improve the design and how can software be verified?

  10. Impact of Agile Software Development Model on Software Maintainability

    ERIC Educational Resources Information Center

    Gawali, Ajay R.

    2012-01-01

    Software maintenance and support costs account for up to 60% of the overall software life cycle cost and often burdens tightly budgeted information technology (IT) organizations. Agile software development approach delivers business value early, but implications on software maintainability are still unknown. The purpose of this quantitative study…

  11. Progressive softening of brittle-ductile transition due to interplay between chemical and deformation processes

    NASA Astrophysics Data System (ADS)

    Jeřábek, Petr; Bukovská, Zita; Morales, Luiz F. G.

    2017-04-01

    The micro-scale shear zones (shear bands) in granitoids from the South Armorican Shear Zone reflect localization of deformation and progressive weakening in the conditions of brittle-ductile transition. We studied microstructures in the shear bands with the aim to establish their P-T conditions and to derive stress and strain rates for specific deformation mechanisms. The evolving microstructure within shear bands documents switches in deformation mechanisms related to positive feedbacks between deformation and chemical processes and imposes mechanical constraints on the evolution of the brittle-ductile transition in the continental transform fault domains. The metamorphic mineral assemblage present in the shear bands indicate their formation at 300-350 ˚ C and 100-400 MPa. Focusing on the early development of shear bands, we identified three stages of shear band evolution. The early stage I associated with initiation of shear bands occurs via formation of microcracks with possible yielding differential stress of up to 250 MPa (Diamond and Tarantola, 2015). Stage II is associated with subgrain rotation recrystallization and dislocation creep in quartz and coeval dissolution-precipitation creep of microcline. Recrystallized quartz grains in shear bands show continual increase in size, and decrease in stress and strain rates from 94 MPa to 17-26 MPa (Stipp and Tullis, 2003) and 3.8*10-12 s-1- 1.8*10-14 s-1 (Patterson and Luan, 1990) associated with deformation partitioning into weaker microcline layer and shear band widening. The quartz mechanical data allowed us to set some constrains for coeval dissolution-precipitation of microcline which at our estimated P-T conditions suggests creep at 17-26 MPa differential stress and 3.8*10-13 s-1 strain rate. Stage III is characterized by localized slip along interconnected white mica bands accommodated by dislocation creep at strain rate 3.8*10-12 s-1 and stress 9.36 MPa (Mares and Kronenberg, 1993). The studied example

  12. Brittle extension of the continental crust along a rooted system of low-angle normal faults: Colorado River extensional corridor

    NASA Technical Reports Server (NTRS)

    John, B. E.; Howard, K. A.

    1985-01-01

    A transect across the 100 km wide Colorado River extensional corridor of mid-Tertiary age shows that the upper 10 to 15 km of crystalline crust extended along an imbricate system of brittle low-angle normal faults. The faults cut gently down a section in the NE-direction of tectonic transport from a headwall breakaway in the Old Woman Mountains, California. Successively higher allochthons above a basal detachment fault are futher displaced from the headwall, some as much as tens of kilometers. Allochthonous blocks are tilted toward the headwall as evidenced by the dip of the cappoing Tertiary strata and originally horizontal Proterozoic diabase sheets. On the down-dip side of the corridor in Arizona, the faults root under the unbroken Hualapai Mountains and the Colorado Plateau. Slip on faults at all exposed levels of the crust was unidirectional. Brittle thinning above these faults affected the entire upper crust, and wholly removed it locally along the central corridor or core complex region. Isostatic uplift exposed metamorphic core complexes in the domed footwall. These data support a model that the crust in California moved out from under Arizona along an asymmetric, rooted normal-slip shear system. Ductile deformation must have accompanied mid-Tertiary crustal extension at deeper structural levels in Arizona.

  13. Pulverized granite at the brittle-ductile transition: An example from the Kellyland fault zone, eastern Maine, U.S.A.

    NASA Astrophysics Data System (ADS)

    Sullivan, Walter A.; Peterman, Emily M.

    2017-08-01

    Granite from a 50-200-m-wide damage zone adjacent to the brittle-ductile Kellyland Fault Zone contains healed fracture networks that exhibit almost all of the characteristics of dynamically pulverized rocks. Fracture networks exhibit only weak preferred orientations, are mutually cross-cutting, separate jigsaw-like interlocking fragments, and are associated with recrystallized areas likely derived from pervasively comminuted material. Fracture networks in samples with primary igneous grain shapes further indicate pulverization. Minimum fracture densities in microcline are ∼100 mm/mm2. Larger fractures in microcline and quartz are sometimes marked by neoblasts, but most fractures are optically continuous with host grains and only visible in cathodoluminescence images. Fractures in plagioclase are crystallographically controlled and typically biotite filled. Petrologic observations and cross-cutting relationships between brittle structures and mylonitic rocks show that fracturing occurred at temperatures of 400 °C or more and pressures of 200 MPa. These constraints extend the known range of pulverization to much higher temperature and pressure conditions than previously thought possible. The mutually cross-cutting healed fractures also provide the first record of repeated damage in pulverized rocks. Furthermore, pulverization must have had a significant but transient effect on wall-rock porosity, and biotite-filled fracture networks in plagioclase form weak zones that could accommodate future strain localization.

  14. Analyzing huge pathology images with open source software.

    PubMed

    Deroulers, Christophe; Ameisen, David; Badoual, Mathilde; Gerin, Chloé; Granier, Alexandre; Lartaud, Marc

    2013-06-06

    Digital pathology images are increasingly used both for diagnosis and research, because slide scanners are nowadays broadly available and because the quantitative study of these images yields new insights in systems biology. However, such virtual slides build up a technical challenge since the images occupy often several gigabytes and cannot be fully opened in a computer's memory. Moreover, there is no standard format. Therefore, most common open source tools such as ImageJ fail at treating them, and the others require expensive hardware while still being prohibitively slow. We have developed several cross-platform open source software tools to overcome these limitations. The NDPITools provide a way to transform microscopy images initially in the loosely supported NDPI format into one or several standard TIFF files, and to create mosaics (division of huge images into small ones, with or without overlap) in various TIFF and JPEG formats. They can be driven through ImageJ plugins. The LargeTIFFTools achieve similar functionality for huge TIFF images which do not fit into RAM. We test the performance of these tools on several digital slides and compare them, when applicable, to standard software. A statistical study of the cells in a tissue sample from an oligodendroglioma was performed on an average laptop computer to demonstrate the efficiency of the tools. Our open source software enables dealing with huge images with standard software on average computers. They are cross-platform, independent of proprietary libraries and very modular, allowing them to be used in other open source projects. They have excellent performance in terms of execution speed and RAM requirements. They open promising perspectives both to the clinician who wants to study a single slide and to the research team or data centre who do image analysis of many slides on a computer cluster. The virtual slide(s) for this article can be found here

  15. Analyzing huge pathology images with open source software

    PubMed Central

    2013-01-01

    Background Digital pathology images are increasingly used both for diagnosis and research, because slide scanners are nowadays broadly available and because the quantitative study of these images yields new insights in systems biology. However, such virtual slides build up a technical challenge since the images occupy often several gigabytes and cannot be fully opened in a computer’s memory. Moreover, there is no standard format. Therefore, most common open source tools such as ImageJ fail at treating them, and the others require expensive hardware while still being prohibitively slow. Results We have developed several cross-platform open source software tools to overcome these limitations. The NDPITools provide a way to transform microscopy images initially in the loosely supported NDPI format into one or several standard TIFF files, and to create mosaics (division of huge images into small ones, with or without overlap) in various TIFF and JPEG formats. They can be driven through ImageJ plugins. The LargeTIFFTools achieve similar functionality for huge TIFF images which do not fit into RAM. We test the performance of these tools on several digital slides and compare them, when applicable, to standard software. A statistical study of the cells in a tissue sample from an oligodendroglioma was performed on an average laptop computer to demonstrate the efficiency of the tools. Conclusions Our open source software enables dealing with huge images with standard software on average computers. They are cross-platform, independent of proprietary libraries and very modular, allowing them to be used in other open source projects. They have excellent performance in terms of execution speed and RAM requirements. They open promising perspectives both to the clinician who wants to study a single slide and to the research team or data centre who do image analysis of many slides on a computer cluster. Virtual slides The virtual slide(s) for this article can be found here: http

  16. Low coverage sequencing of three echinoderm genomes: the brittle star Ophionereis fasciata, the sea star Patiriella regularis, and the sea cucumber Australostichopus mollis.

    PubMed

    Long, Kyle A; Nossa, Carlos W; Sewell, Mary A; Putnam, Nicholas H; Ryan, Joseph F

    2016-01-01

    There are five major extant groups of Echinodermata: Crinoidea (feather stars and sea lillies), Ophiuroidea (brittle stars and basket stars), Asteroidea (sea stars), Echinoidea (sea urchins, sea biscuits, and sand dollars), and Holothuroidea (sea cucumbers). These animals are known for their pentaradial symmetry as adults, unique water vascular system, mutable collagenous tissues, and endoskeletons of high magnesium calcite. To our knowledge, the only echinoderm species with a genome sequence available to date is Strongylocentrotus pupuratus (Echinoidea). The availability of additional echinoderm genome sequences is crucial for understanding the biology of these animals. Here we present assembled draft genomes of the brittle star Ophionereis fasciata, the sea star Patiriella regularis, and the sea cucumber Australostichopus mollis from Illumina sequence data with coverages of 12.5x, 22.5x, and 21.4x, respectively. These data provide a resource for mining gene superfamilies, identifying non-coding RNAs, confirming gene losses, and designing experimental constructs. They will be important comparative resources for future genomic studies in echinoderms.

  17. Fold-and-thrust belt evolution influenced by along and across strike thickness variations: new insights from brittle-ductile centrifuge analogue models

    NASA Astrophysics Data System (ADS)

    Santolaria Otin, Pablo; Harris, Lyal; Casas, Antonio; Soto, Ruth

    2014-05-01

    Using a new centrifuge analogue modelling approach, 38 models were performed to study the influence of along and across strike thickness variations of a ductile-brittle layered sequence on the kinematics and deformation style of fold-and-thrust belts. Four different series, changing the brittle-ductile thickness ratio in models with i) constant thickness, ii) across strike varying thickness, iii) along strike varying thickness and iv) along and across-strike varying thickness, were performed. The brittle sedimentary cover was simulated by "Moon Sand™", regular fine-grained quartz sand coated by polymer and synthetic rubber binders, allowing layers to be placed vertically in the centrifuge (impossible with normal sand). The ductile décollement (evaporites) was simulated by silicone putty (Crazy Aaron Enterprise's Thinking Putty™). Models were run step by step in a high-acceleration centrifuge attaining 900 g, what allows to drastically reduce the experimental time. In addition to surface observation and serial cross-sections at the end of the models, CT scans portray the progressive 3- and 4-dimensional evolution of several models. With constant thickness, the increase of the brittle-ductile ratio results in the decrease of the number of structures where shortening is accommodated and the development of structures does not follow a linear sequence. Across-strike thickness variations trigger the location of deformation towards the wedge front, precluding the emplacement of structures in the hinterland. Along-strike thickness changes result in the lateral variation of the number of structure and a differential displacement of the deformation front. The occurrence of oblique structures is enhanced in wedges with across and along strike thickness variations where, in addition, rotational domains are observed. Comparison with the South Pyrenean Central Unit, in the Southern Pyrenees, characterized by a west- and southward thinning of the pretectonic Mesozoic series

  18. Overcoming Barriers in Working with Families

    ERIC Educational Resources Information Center

    Heru, Alison M.; Drury, Laura

    2006-01-01

    Objective: The Accreditation Council for Graduate Medical Education and the Residency Review Committee for psychiatry outline the expected competencies for residents. These competencies include working with families. This article describes barriers that residents face when working with families, and offers ways to overcome these barriers. Method:…

  19. Software security checklist for the software life cycle

    NASA Technical Reports Server (NTRS)

    Gilliam, D. P.; Wolfe, T. L.; Sherif, J. S.

    2002-01-01

    A formal approach to security in the software life cycle is essential to protect corporate resources. However, little thought has been given to this aspect of software development. Due to its criticality, security should be integrated as a formal approach in the software life cycle.

  20. Software Epistemology

    DTIC Science & Technology

    2016-03-01

    in-vitro decision to incubate a startup, Lexumo [7], which is developing a commercial Software as a Service ( SaaS ) vulnerability assessment...LTS Label Transition System MUSE Mining and Understanding Software Enclaves RTEMS Real-Time Executive for Multi-processor Systems SaaS Software ...as a Service SSA Static Single Assignment SWE Software Epistemology UD/DU Def-Use/Use-Def Chains (Dataflow Graph)

  1. Adolescents' Self-Efficacy to Overcome Barriers to Physical Activity Scale

    ERIC Educational Resources Information Center

    Dwyer, John J. M.; Chulak, Tala; Maitland, Scott; Allison, Kenneth R.; Lysy, Daria C.; Faulkner, Guy E. J.; Sheeshka, Judy

    2012-01-01

    This paper describes a revised measure of self-efficacy to overcome barriers to moderate and vigorous physical activity in a sample of 484 high school students in Toronto, Ontario. The students had a mean age of 15.3 years. Principal axis factoring with oblique rotation yielded five factors: self-efficacy to overcome internal, harassment, physical…

  2. Computer software.

    PubMed

    Rosenthal, L E

    1986-10-01

    Software is the component in a computer system that permits the hardware to perform the various functions that a computer system is capable of doing. The history of software and its development can be traced to the early nineteenth century. All computer systems are designed to utilize the "stored program concept" as first developed by Charles Babbage in the 1850s. The concept was lost until the mid-1940s, when modern computers made their appearance. Today, because of the complex and myriad tasks that a computer system can perform, there has been a differentiation of types of software. There is software designed to perform specific business applications. There is software that controls the overall operation of a computer system. And there is software that is designed to carry out specialized tasks. Regardless of types, software is the most critical component of any computer system. Without it, all one has is a collection of circuits, transistors, and silicone chips.

  3. Free Webinar February 28: Overcoming the Impacts of Fast Charging | News |

    Science.gov Websites

    NREL Free Webinar February 28: Overcoming the Impacts of Fast Charging Free Webinar February 28 will be moderating a free one-hour webinar titled, "Overcoming the Impacts of Fast Charging on

  4. Fracture spacing in tensile brittle layers adhering to a rigid substrate

    NASA Astrophysics Data System (ADS)

    Lazarus, Véronique

    2017-01-01

    A natural question arising when observing crack networks in brittle layers such as, e.g., paints, muds, skins, pottery glazes, coatings, ceramics, is what determines the distance between cracks. This apparently simple question received a wealth of more or less complex and appropriate answers, but no consensus has emerged. Here, we show that the cracks interact mutually as soon as the spacing between them is smaller than ten times the thickness of the layer. Then, a simple Griffith-type balance between the elastic deformation energy and the fracture bulk and debonding costs captures a broad number of observations, going from the square-root or linear increase of the spacing with the thickness, to its decrease with loading until saturation. The adhesion strength is identified as playing a key role in these behaviour changes. As illustration, we show how the model can be applied to study the influence of the layer thickness on crack patterns. We believe that the versatility of the approach should permit wide applicability, from geosciences to engineering.

  5. Software engineering laboratory series: Annotated bibliography of software engineering laboratory literature

    NASA Technical Reports Server (NTRS)

    Morusiewicz, Linda; Valett, Jon

    1992-01-01

    This document is an annotated bibliography of technical papers, documents, and memorandums produced by or related to the Software Engineering Laboratory. More than 100 publications are summarized. These publications cover many areas of software engineering and range from research reports to software documentation. This document has been updated and reorganized substantially since the original version (SEL-82-006, November 1982). All materials have been grouped into eight general subject areas for easy reference: (1) the Software Engineering Laboratory; (2) the Software Engineering Laboratory: Software Development Documents; (3) Software Tools; (4) Software Models; (5) Software Measurement; (6) Technology Evaluations; (7) Ada Technology; and (8) Data Collection. This document contains an index of these publications classified by individual author.

  6. 38 CFR 17.152 - Devices to assist in overcoming the handicap of deafness.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Devices to assist in overcoming the handicap of deafness. 17.152 Section 17.152 Pensions, Bonuses, and Veterans' Relief DEPARTMENT... in overcoming the handicap of deafness. Devices for assisting in overcoming the handicap of deafness...

  7. 38 CFR 17.152 - Devices to assist in overcoming the handicap of deafness.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Devices to assist in overcoming the handicap of deafness. 17.152 Section 17.152 Pensions, Bonuses, and Veterans' Relief DEPARTMENT... in overcoming the handicap of deafness. Devices for assisting in overcoming the handicap of deafness...

  8. 38 CFR 17.152 - Devices to assist in overcoming the handicap of deafness.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Devices to assist in overcoming the handicap of deafness. 17.152 Section 17.152 Pensions, Bonuses, and Veterans' Relief DEPARTMENT... in overcoming the handicap of deafness. Devices for assisting in overcoming the handicap of deafness...

  9. 38 CFR 17.152 - Devices to assist in overcoming the handicap of deafness.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Devices to assist in overcoming the handicap of deafness. 17.152 Section 17.152 Pensions, Bonuses, and Veterans' Relief DEPARTMENT... in overcoming the handicap of deafness. Devices for assisting in overcoming the handicap of deafness...

  10. 38 CFR 17.152 - Devices to assist in overcoming the handicap of deafness.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Devices to assist in overcoming the handicap of deafness. 17.152 Section 17.152 Pensions, Bonuses, and Veterans' Relief DEPARTMENT... in overcoming the handicap of deafness. Devices for assisting in overcoming the handicap of deafness...

  11. Software Engineering Guidebook

    NASA Technical Reports Server (NTRS)

    Connell, John; Wenneson, Greg

    1993-01-01

    The Software Engineering Guidebook describes SEPG (Software Engineering Process Group) supported processes and techniques for engineering quality software in NASA environments. Three process models are supported: structured, object-oriented, and evolutionary rapid-prototyping. The guidebook covers software life-cycles, engineering, assurance, and configuration management. The guidebook is written for managers and engineers who manage, develop, enhance, and/or maintain software under the Computer Software Services Contract.

  12. The Software Engineering Laboratory: An operational software experience factory

    NASA Technical Reports Server (NTRS)

    Basili, Victor R.; Caldiera, Gianluigi; Mcgarry, Frank; Pajerski, Rose; Page, Gerald; Waligora, Sharon

    1992-01-01

    For 15 years, the Software Engineering Laboratory (SEL) has been carrying out studies and experiments for the purpose of understanding, assessing, and improving software and software processes within a production software development environment at NASA/GSFC. The SEL comprises three major organizations: (1) NASA/GSFC, Flight Dynamics Division; (2) University of Maryland, Department of Computer Science; and (3) Computer Sciences Corporation, Flight Dynamics Technology Group. These organizations have jointly carried out several hundred software studies, producing hundreds of reports, papers, and documents, all of which describe some aspect of the software engineering technology that was analyzed in the flight dynamics environment at NASA. The studies range from small, controlled experiments (such as analyzing the effectiveness of code reading versus that of functional testing) to large, multiple project studies (such as assessing the impacts of Ada on a production environment). The organization's driving goal is to improve the software process continually, so that sustained improvement may be observed in the resulting products. This paper discusses the SEL as a functioning example of an operational software experience factory and summarizes the characteristics of and major lessons learned from 15 years of SEL operations.

  13. Predictive modeling of dynamic fracture growth in brittle materials with machine learning

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Moore, Bryan A.; Rougier, Esteban; O’Malley, Daniel

    We use simulation data from a high delity Finite-Discrete Element Model to build an e cient Machine Learning (ML) approach to predict fracture growth and coalescence. Our goal is for the ML approach to be used as an emulator in place of the computationally intensive high delity models in an uncertainty quanti cation framework where thousands of forward runs are required. The failure of materials with various fracture con gurations (size, orientation and the number of initial cracks) are explored and used as data to train our ML model. This novel approach has shown promise in predicting spatial (path tomore » failure) and temporal (time to failure) aspects of brittle material failure. Predictions of where dominant fracture paths formed within a material were ~85% accurate and the time of material failure deviated from the actual failure time by an average of ~16%. Additionally, the ML model achieves a reduction in computational cost by multiple orders of magnitude.« less

  14. Specimen size effects on ductile?brittle transition temperature in Charpy impact testing

    NASA Astrophysics Data System (ADS)

    Kurishita, H.; Yamamoto, T.; Narui, M.; Suwarno, H.; Yoshitake, T.; Yano, Y.; Yamazaki, M.; Matsui, H.

    2004-08-01

    One key issue for small specimen test techniques is to clarify specimen size effects on test results. In consideration of size effects on determining the ductile-to-brittle transition temperature (DBTT) in Charpy impact testing, a method to evaluate the plastic constraint loss for differently sized Charpy V-notch (CVN) specimens is proposed and applied to a ferritic-martensitic steel, 2WFK, developed by JNC. In the method, a constraint factor, α, that is an index of the plastic constraint is defined as α=σ ∗/σ y∗. Here, σ ∗ is the critical cleavage fracture stress which is a material constant and σ y∗ is the uniaxial yield stress at the DBTT at the strain rate generated in the Charpy impact test. The procedures for evaluating each of σ ∗ and σ y∗ are described and a result of σ ∗ and σ y∗, thus the value of α, is presented for different types of miniaturized and full-sized CVN specimens of 2WFK.

  15. Large-scale 3D modeling of projectile impact damage in brittle plates

    NASA Astrophysics Data System (ADS)

    Seagraves, A.; Radovitzky, R.

    2015-10-01

    The damage and failure of brittle plates subjected to projectile impact is investigated through large-scale three-dimensional simulation using the DG/CZM approach introduced by Radovitzky et al. [Comput. Methods Appl. Mech. Eng. 2011; 200(1-4), 326-344]. Two standard experimental setups are considered: first, we simulate edge-on impact experiments on Al2O3 tiles by Strassburger and Senf [Technical Report ARL-CR-214, Army Research Laboratory, 1995]. Qualitative and quantitative validation of the simulation results is pursued by direct comparison of simulations with experiments at different loading rates and good agreement is obtained. In the second example considered, we investigate the fracture patterns in normal impact of spheres on thin, unconfined ceramic plates over a wide range of loading rates. For both the edge-on and normal impact configurations, the full field description provided by the simulations is used to interpret the mechanisms underlying the crack propagation patterns and their strong dependence on loading rate.

  16. Predictive modeling of dynamic fracture growth in brittle materials with machine learning

    DOE PAGES

    Moore, Bryan A.; Rougier, Esteban; O’Malley, Daniel; ...

    2018-02-22

    We use simulation data from a high delity Finite-Discrete Element Model to build an e cient Machine Learning (ML) approach to predict fracture growth and coalescence. Our goal is for the ML approach to be used as an emulator in place of the computationally intensive high delity models in an uncertainty quanti cation framework where thousands of forward runs are required. The failure of materials with various fracture con gurations (size, orientation and the number of initial cracks) are explored and used as data to train our ML model. This novel approach has shown promise in predicting spatial (path tomore » failure) and temporal (time to failure) aspects of brittle material failure. Predictions of where dominant fracture paths formed within a material were ~85% accurate and the time of material failure deviated from the actual failure time by an average of ~16%. Additionally, the ML model achieves a reduction in computational cost by multiple orders of magnitude.« less

  17. A statistical approach to the brittle fracture of a multi-phase solid

    NASA Technical Reports Server (NTRS)

    Liu, W. K.; Lua, Y. I.; Belytschko, T.

    1991-01-01

    A stochastic damage model is proposed to quantify the inherent statistical distribution of the fracture toughness of a brittle, multi-phase solid. The model, based on the macrocrack-microcrack interaction, incorporates uncertainties in locations and orientations of microcracks. Due to the high concentration of microcracks near the macro-tip, a higher order analysis based on traction boundary integral equations is formulated first for an arbitrary array of cracks. The effects of uncertainties in locations and orientations of microcracks at a macro-tip are analyzed quantitatively by using the boundary integral equations method in conjunction with the computer simulation of the random microcrack array. The short range interactions resulting from surrounding microcracks closet to the main crack tip are investigated. The effects of microcrack density parameter are also explored in the present study. The validity of the present model is demonstrated by comparing its statistical output with the Neville distribution function, which gives correct fits to sets of experimental data from multi-phase solids.

  18. Successful Writing: Five Roadblocks to Overcome

    ERIC Educational Resources Information Center

    King, Kathleen P.

    2013-01-01

    This article provides essential strategies to be more successful in one of the major roles in academia: writing. Most academics struggle with roadblocks in their writing process. We are forever battling to complete research articles, manuscripts, grant proposals or other documents. The strategies and perspective shared here help overcome several…

  19. Computer-Aided Software Engineering - An approach to real-time software development

    NASA Technical Reports Server (NTRS)

    Walker, Carrie K.; Turkovich, John J.

    1989-01-01

    A new software engineering discipline is Computer-Aided Software Engineering (CASE), a technology aimed at automating the software development process. This paper explores the development of CASE technology, particularly in the area of real-time/scientific/engineering software, and a history of CASE is given. The proposed software development environment for the Advanced Launch System (ALS CASE) is described as an example of an advanced software development system for real-time/scientific/engineering (RT/SE) software. The Automated Programming Subsystem of ALS CASE automatically generates executable code and corresponding documentation from a suitably formatted specification of the software requirements. Software requirements are interactively specified in the form of engineering block diagrams. Several demonstrations of the Automated Programming Subsystem are discussed.

  20. Autonomous robot software development using simple software components

    NASA Astrophysics Data System (ADS)

    Burke, Thomas M.; Chung, Chan-Jin

    2004-10-01

    Developing software to control a sophisticated lane-following, obstacle-avoiding, autonomous robot can be demanding and beyond the capabilities of novice programmers - but it doesn"t have to be. A creative software design utilizing only basic image processing and a little algebra, has been employed to control the LTU-AISSIG autonomous robot - a contestant in the 2004 Intelligent Ground Vehicle Competition (IGVC). This paper presents a software design equivalent to that used during the IGVC, but with much of the complexity removed. The result is an autonomous robot software design, that is robust, reliable, and can be implemented by programmers with a limited understanding of image processing. This design provides a solid basis for further work in autonomous robot software, as well as an interesting and achievable robotics project for students.

  1. Enamel: From brittle to ductile like tribological response.

    PubMed

    Guidoni, G; Swain, M; Jäger, I

    2008-10-01

    To identify the intrinsic nano-scale wear mechanisms of enamel by comparing it with that of highly brittle glass, and highly ductile copper and silver monocrystals. A sharp cube corner indenter tip (20-50 nm radius) was used to abrade glass, enamel as well as copper and silver monocrystals. Square abraded areas (5 microm x 5 microm, 10 microm x 10 microm) were generated with loads of 50 microN for enamel and 100 microN for the remaining materials (2D abrasion). The normal load and displacement data were utilized in a complementary manner to support the comparison. In addition normal and lateral forces were simultaneously measured along 10 microm single scratched lines (1D abrasion). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were also used to characterise the worn areas and debris. The sharp tip cuts into and ploughs the specimens creating a wedge or ridge of material ahead of itself which eventually detaches, for the ductile materials and at high loads in enamel. For glass and enamel at low loads, the indenter tip ploughs into the material and the removed material is redistributed and pressed back into the abraded area. The wear behaviour of enamel at the nano-level resembles that obtained with glass at low loads (50 microN) and that obtained with metal mono-crystals at high load (100 microN). The role of the microstructural heterogeneity in the wear behaviour of enamel is considered in the discussion. The relevance to clinical wear of enamel is also considered.

  2. NASA software documentation standard software engineering program

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The NASA Software Documentation Standard (hereinafter referred to as Standard) can be applied to the documentation of all NASA software. This Standard is limited to documentation format and content requirements. It does not mandate specific management, engineering, or assurance standards or techniques. This Standard defines the format and content of documentation for software acquisition, development, and sustaining engineering. Format requirements address where information shall be recorded and content requirements address what information shall be recorded. This Standard provides a framework to allow consistency of documentation across NASA and visibility into the completeness of project documentation. This basic framework consists of four major sections (or volumes). The Management Plan contains all planning and business aspects of a software project, including engineering and assurance planning. The Product Specification contains all technical engineering information, including software requirements and design. The Assurance and Test Procedures contains all technical assurance information, including Test, Quality Assurance (QA), and Verification and Validation (V&V). The Management, Engineering, and Assurance Reports is the library and/or listing of all project reports.

  3. 48 CFR 227.7202 - Commercial computer software and commercial computer software documentation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... software and commercial computer software documentation. 227.7202 Section 227.7202 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7202 Commercial computer software and commercial computer software documentation. ...

  4. 48 CFR 227.7203 - Noncommercial computer software and noncommercial computer software documentation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... software and noncommercial computer software documentation. 227.7203 Section 227.7203 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203 Noncommercial computer software and noncommercial computer software documentation. ...

  5. 48 CFR 227.7203 - Noncommercial computer software and noncommercial computer software documentation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... software and noncommercial computer software documentation. 227.7203 Section 227.7203 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203 Noncommercial computer software and noncommercial computer software documentation. ...

  6. 48 CFR 227.7203 - Noncommercial computer software and noncommercial computer software documentation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... software and noncommercial computer software documentation. 227.7203 Section 227.7203 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203 Noncommercial computer software and noncommercial computer software documentation. ...

  7. 48 CFR 227.7202 - Commercial computer software and commercial computer software documentation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... software and commercial computer software documentation. 227.7202 Section 227.7202 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7202 Commercial computer software and commercial computer software documentation. ...

  8. 48 CFR 227.7203 - Noncommercial computer software and noncommercial computer software documentation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... software and noncommercial computer software documentation. 227.7203 Section 227.7203 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203 Noncommercial computer software and noncommercial computer software documentation. ...

  9. 48 CFR 227.7202 - Commercial computer software and commercial computer software documentation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... software and commercial computer software documentation. 227.7202 Section 227.7202 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7202 Commercial computer software and commercial computer software documentation. ...

  10. 48 CFR 227.7202 - Commercial computer software and commercial computer software documentation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... software and commercial computer software documentation. 227.7202 Section 227.7202 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7202 Commercial computer software and commercial computer software documentation. ...

  11. 48 CFR 227.7202 - Commercial computer software and commercial computer software documentation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... software and commercial computer software documentation. 227.7202 Section 227.7202 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7202 Commercial computer software and commercial computer software documentation. ...

  12. 48 CFR 227.7203 - Noncommercial computer software and noncommercial computer software documentation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... software and noncommercial computer software documentation. 227.7203 Section 227.7203 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203 Noncommercial computer software and noncommercial computer software documentation. ...

  13. A phenomenological molecular model for yielding and brittle-ductile transition of polymer glasses

    NASA Astrophysics Data System (ADS)

    Wang, Shi-Qing; Cheng, Shiwang; Lin, Panpan; Li, Xiaoxiao

    2014-09-01

    This work formulates, at a molecular level, a phenomenological theoretical description of the brittle-ductile transition (BDT) in tensile extension, exhibited by all polymeric glasses of high molecular weight (MW). The starting point is our perception of a polymer glass (under large deformation) as a structural hybrid, consisting of a primary structure due to the van der Waals bonding and a chain network whose junctions are made of pairs of hairpins and function like chemical crosslinks due to the intermolecular uncrossability. During extension, load-bearing strands (LBSs) emerge between the junctions in the affinely strained chain network. Above the BDT, i.e., at "warmer" temperatures where the glass is less vitreous, the influence of the chain network reaches out everywhere by activating all segments populated transversely between LBSs, starting from those adjacent to LBSs. It is the chain network that drives the primary structure to undergo yielding and plastic flow. Below the BDT, the glassy state is too vitreous to yield before the chain network suffers a structural breakdown. Thus, brittle failure becomes inevitable. For any given polymer glass of high MW, there is one temperature TBD or a very narrow range of temperature where the yielding of the glass barely takes place as the chain network also reaches the point of a structural failure. This is the point of the BDT. A theoretical analysis of the available experimental data reveals that (a) chain pullout occurs at the BDT when the chain tension builds up to reach a critical value fcp during tensile extension; (b) the limiting value of fcp, extrapolated to far below the glass transition temperature Tg, is of a universal magnitude around 0.2-0.3 nN, for all eight polymers examined in this work; (c) pressurization, which is known [K. Matsushige, S. V. Radcliffe, and E. Baer, J. Appl. Polym. Sci. 20, 1853 (1976)] to make brittle polystyrene (PS) and poly(methyl methacrylate) (PMMA) ductile at room temperature

  14. A phenomenological molecular model for yielding and brittle-ductile transition of polymer glasses.

    PubMed

    Wang, Shi-Qing; Cheng, Shiwang; Lin, Panpan; Li, Xiaoxiao

    2014-09-07

    This work formulates, at a molecular level, a phenomenological theoretical description of the brittle-ductile transition (BDT) in tensile extension, exhibited by all polymeric glasses of high molecular weight (MW). The starting point is our perception of a polymer glass (under large deformation) as a structural hybrid, consisting of a primary structure due to the van der Waals bonding and a chain network whose junctions are made of pairs of hairpins and function like chemical crosslinks due to the intermolecular uncrossability. During extension, load-bearing strands (LBSs) emerge between the junctions in the affinely strained chain network. Above the BDT, i.e., at "warmer" temperatures where the glass is less vitreous, the influence of the chain network reaches out everywhere by activating all segments populated transversely between LBSs, starting from those adjacent to LBSs. It is the chain network that drives the primary structure to undergo yielding and plastic flow. Below the BDT, the glassy state is too vitreous to yield before the chain network suffers a structural breakdown. Thus, brittle failure becomes inevitable. For any given polymer glass of high MW, there is one temperature TBD or a very narrow range of temperature where the yielding of the glass barely takes place as the chain network also reaches the point of a structural failure. This is the point of the BDT. A theoretical analysis of the available experimental data reveals that (a) chain pullout occurs at the BDT when the chain tension builds up to reach a critical value f(cp) during tensile extension; (b) the limiting value of f(cp), extrapolated to far below the glass transition temperature T(g), is of a universal magnitude around 0.2-0.3 nN, for all eight polymers examined in this work; (c) pressurization, which is known [K. Matsushige, S. V. Radcliffe, and E. Baer, J. Appl. Polym. Sci. 20, 1853 (1976)] to make brittle polystyrene (PS) and poly(methyl methacrylate) (PMMA) ductile at room

  15. Science and Software

    NASA Astrophysics Data System (ADS)

    Zelt, C. A.

    2017-12-01

    Earth science attempts to understand how the earth works. This research often depends on software for modeling, processing, inverting or imaging. Freely sharing open-source software is essential to prevent reinventing the wheel and allows software to be improved and applied in ways the original author may never have envisioned. For young scientists, releasing software can increase their name ID when applying for jobs and funding, and create opportunities for collaborations when scientists who collect data want the software's creator to be involved in their project. However, we frequently hear scientists say software is a tool, it's not science. Creating software that implements a new or better way of earth modeling or geophysical processing, inverting or imaging should be viewed as earth science. Creating software for things like data visualization, format conversion, storage, or transmission, or programming to enhance computational performance, may be viewed as computer science. The former, ideally with an application to real data, can be published in earth science journals, the latter possibly in computer science journals. Citations in either case should accurately reflect the impact of the software on the community. Funding agencies need to support more software development and open-source releasing, and the community should give more high-profile awards for developing impactful open-source software. Funding support and community recognition for software development can have far reaching benefits when the software is used in foreseen and unforeseen ways, potentially for years after the original investment in the software development. For funding, an open-source release that is well documented should be required, with example input and output files. Appropriate funding will provide the incentive and time to release user-friendly software, and minimize the need for others to duplicate the effort. All funded software should be available through a single web site

  16. Software archeology: a case study in software quality assurance and design

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Macdonald, John M; Lloyd, Jane A; Turner, Cameron J

    2009-01-01

    Ideally, quality is designed into software, just as quality is designed into hardware. However, when dealing with legacy systems, demonstrating that the software meets required quality standards may be difficult to achieve. As the need to demonstrate the quality of existing software was recognized at Los Alamos National Laboratory (LANL), an effort was initiated to uncover and demonstrate that legacy software met the required quality standards. This effort led to the development of a reverse engineering approach referred to as software archaeology. This paper documents the software archaeology approaches used at LANL to document legacy software systems. A case studymore » for the Robotic Integrated Packaging System (RIPS) software is included.« less

  17. Excess vibrational density of states and the brittle to ductile transition in crystalline and amorphous solids.

    PubMed

    Babu, Jeetu S; Mondal, Chandana; Sengupta, Surajit; Karmakar, Smarajit

    2016-01-28

    The conditions which determine whether a material behaves in a brittle or ductile fashion on mechanical loading are still elusive and comprise a topic of active research among materials physicists and engineers. In this study, we present the results of in silico mechanical deformation experiments from two very different model solids in two and three dimensions. The first consists of particles interacting with isotropic potentials and the other has strongly direction dependent interactions. We show that in both cases, the excess vibrational density of states is one of the fundamental quantities which characterizes the ductility of the material. Our results can be checked using careful experiments on colloidal solids.

  18. Overcoming Space and Time Disadvantages in Joint Theater Missile Defense

    DTIC Science & Technology

    2002-02-04

    Disadvantages in Joint Theater Missile Defense (Unclassified) 9. Personal Authors: Major Robert Kelley 10.Type of Report: FINAL 11. Date of Report...Classification of This Page Unclassified NAVAL WAR COLLEGE Newport, RI Overcoming Space and Time Disadvantages in Joint Theater Missile Defense By Robert...Covered (from... to) - Title and Subtitle Overcoming Space and Time Disadvantages in Joint Theater Missile Defense Contract Number Grant Number

  19. A Probabilistic Software System Attribute Acceptance Paradigm for COTS Software Evaluation

    NASA Technical Reports Server (NTRS)

    Morris, A. Terry

    2005-01-01

    Standard software requirement formats are written from top-down perspectives only, that is, from an ideal notion of a client s needs. Despite the exactness of the standard format, software and system errors in designed systems have abounded. Bad and inadequate requirements have resulted in cost overruns, schedule slips and lost profitability. Commercial off-the-shelf (COTS) software components are even more troublesome than designed systems because they are often provided as is and subsequently delivered with unsubstantiated validation of described capabilities. For COTS software, there needs to be a way to express the client s software needs in a consistent and formal manner using software system attributes derived from software quality standards. Additionally, the format needs to be amenable to software evaluation processes that integrate observable evidence garnered from historical data. This paper presents a paradigm that effectively bridges the gap between what a client desires (top-down) and what has been demonstrated (bottom-up) for COTS software evaluation. The paradigm addresses the specification of needs before the software evaluation is performed and can be used to increase the shared understanding between clients and software evaluators about what is required and what is technically possible.

  20. Predicting the mechanical properties of brittle porous materials with various porosity and pore sizes.

    PubMed

    Cui, Zhiwei; Huang, Yongmin; Liu, Honglai

    2017-07-01

    In this work, a micromechanical study using the lattice spring model (LSM) was performed to predict the mechanical properties of BPMs by simulation of the Brazilian test. Stress-strain curve and Weibull plot were analyzed for the determination of fracture strength and Weibull modulus. The presented model composed of linear elastic elements is capable of reproducing the non-linear behavior of BPMs resulting from the damage accumulation and provides consistent results which are in agreement with experimental measurements. Besides, it is also found that porosity shows significant impact on fracture strength while pore size dominates the Weibull modulus, which enables us to establish how choices made in the microstructure to meet the demand of brittle porous materials functioning in various operating conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Dependence of the brittle ductile transition on strain-rate-dependent critical homologous temperature

    NASA Astrophysics Data System (ADS)

    Davis, Paul M.

    2017-05-01

    Earthquakes mainly occur in crust or mantle that is below a critical temperature for the tectonic strain-rate, \\dot{e}_t, such that stress builds up to the breaking point before it can relax due to creep. Then long-range stress correlation gives rise to power law seismicity including large events. The limiting temperature depends on pressure, which is taken into account by finding a critical homologous temperature THc = T/TM above which earthquakes are rarely observed (where T, TM are temperature and average melting temperature of constituent minerals). We find that THc for ocean plates is ∼0.55. For California earthquakes, it is also close to 0.55. The uppermost mantle layer of oceanic plates of thickness ∼50 km is composed of harzburgite and depleted peridotite from which basalt has been removed to form ocean crust. Thus it has a higher melting temperature than the peridotite of the surrounding mantle, or the lower halves of plates. Thicknesses of seismicity in deep subduction zones, determined from 2-D polynomial fits to a relocated catalogue, are ∼50 km, which suggests that the earthquake channel is confined to this layer. We construct models to find homologous temperatures in slabs, and find that seismicity thicknesses are also, on average, confined to TH ≤ 0.55 ± 0.05. The associated rheology is compared with that obtained from flexure models of ocean lithosphere. The brittle-ductile transition occurs where viscosity drops from high values in the cold cores of slabs to values of 1022-1023 Pa s, that is, where creep strain-rates become comparable to tectonic rates. The cut-off for deep earthquakes is not sharp. However they appear unlikely to occur if homologous temperature is high TH > 0.55. Exceptions to the rule are anomalously deep earthquakes such as those beneath the Iceland and the Hawaiian hotspots, and the Newport Inglewood Fault. These are smaller events with short-range stress correlation, and can be explained if strain-rates are two to

  2. Software safety

    NASA Technical Reports Server (NTRS)

    Leveson, Nancy

    1987-01-01

    Software safety and its relationship to other qualities are discussed. It is shown that standard reliability and fault tolerance techniques will not solve the safety problem for the present. A new attitude requires: looking at what you do NOT want software to do along with what you want it to do; and assuming things will go wrong. New procedures and changes to entire software development process are necessary: special software safety analysis techniques are needed; and design techniques, especially eliminating complexity, can be very helpful.

  3. Software Engineering Laboratory Series: Collected Software Engineering Papers. Volume 15

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Software Engineering Laboratory (SEL) is an organization sponsored by NASA/GSFC and created to investigate the effectiveness of software engineering technologies when applied to the development of application software. The activities, findings, and recommendations of the SEL are recorded in the Software Engineering Laboratory Series, a continuing series of reports that includes this document.

  4. Software Engineering Laboratory Series: Collected Software Engineering Papers. Volume 14

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Software Engineering Laboratory (SEL) is an organization sponsored by NASA/GSFC and created to investigate the effectiveness of software engineering technologies when applied to the development of application software. The activities, findings, and recommendations of the SEL are recorded in the Software Engineering Laboratory Series, a continuing series of reports that includes this document.

  5. Software Engineering Laboratory Series: Collected Software Engineering Papers. Volume 13

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The Software Engineering Laboratory (SEL) is an organization sponsored by NASA/GSFC and created to investigate the effectiveness of software engineering technologies when applied to the development of application software. The activities, findings, and recommendations of the SEL are recorded in the Software Engineering Laboratory Series, a continuing series of reports that includes this document.

  6. Brittle failure of rock: A review and general linear criterion

    NASA Astrophysics Data System (ADS)

    Labuz, Joseph F.; Zeng, Feitao; Makhnenko, Roman; Li, Yuan

    2018-07-01

    A failure criterion typically is phenomenological since few models exist to theoretically derive the mathematical function. Indeed, a successful failure criterion is a generalization of experimental data obtained from strength tests on specimens subjected to known stress states. For isotropic rock that exhibits a pressure dependence on strength, a popular failure criterion is a linear equation in major and minor principal stresses, independent of the intermediate principal stress. A general linear failure criterion called Paul-Mohr-Coulomb (PMC) contains all three principal stresses with three material constants: friction angles for axisymmetric compression ϕc and extension ϕe and isotropic tensile strength V0. PMC provides a framework to describe a nonlinear failure surface by a set of planes "hugging" the curved surface. Brittle failure of rock is reviewed and multiaxial test methods are summarized. Equations are presented to implement PMC for fitting strength data and determining the three material parameters. A piecewise linear approximation to a nonlinear failure surface is illustrated by fitting two planes with six material parameters to form either a 6- to 12-sided pyramid or a 6- to 12- to 6-sided pyramid. The particular nature of the failure surface is dictated by the experimental data.

  7. Fracture toughness of brittle materials determined with chevron notch specimens

    NASA Technical Reports Server (NTRS)

    Shannon, J. L., Jr.; Bursey, R. T.; Munz, D.; Pierce, W. S.

    1980-01-01

    The use of chevron-notch specimens for determining the plane strain fracture toughness (K sub Ic) of brittle materials is discussed. Three chevron-notch specimens were investigated: short bar, short rod, and four-point-bend. The dimensionless stress intensity coefficient used in computing K sub Ic is derived for the short bar specimen from the superposition of ligament-dependent and ligament-independent solutions for the straight through crack, and also from experimental compliance calibrations. Coefficients for the four-point-bend specimen were developed by the same superposition procedure, and with additional refinement using the slice model of Bluhm. Short rod specimen stress intensity coefficients were determined only by experimental compliance calibration. Performance of the three chevron-notch specimens and their stress intensity factor relations were evaluated by tests on hot-pressed silicon nitride and sintered aluminum oxide. Results obtained with the short bar and the four-point-bend specimens on silicon nitride are in good agreement and relatively free of specimen geometry and size effects within the range investigated. Results on aluminum oxide were affected by specimen size and chevron-notch geometry, believed due to a rising crack growth resistance curve for the material. Only the results for the short bar specimen are presented in detail.

  8. Software assurance standard

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This standard specifies the software assurance program for the provider of software. It also delineates the assurance activities for the provider and the assurance data that are to be furnished by the provider to the acquirer. In any software development effort, the provider is the entity or individual that actually designs, develops, and implements the software product, while the acquirer is the entity or individual who specifies the requirements and accepts the resulting products. This standard specifies at a high level an overall software assurance program for software developed for and by NASA. Assurance includes the disciplines of quality assurance, quality engineering, verification and validation, nonconformance reporting and corrective action, safety assurance, and security assurance. The application of these disciplines during a software development life cycle is called software assurance. Subsequent lower-level standards will specify the specific processes within these disciplines.

  9. A New Multiaxial High-Cycle Fatigue Criterion Based on the Critical Plane for Ductile and Brittle Materials

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Shang, De-Guang; Wang, Xiao-Wei

    2015-02-01

    An improved high-cycle multiaxial fatigue criterion based on the critical plane was proposed in this paper. The critical plane was defined as the plane of maximum shear stress (MSS) in the proposed multiaxial fatigue criterion, which is different from the traditional critical plane based on the MSS amplitude. The proposed criterion was extended as a fatigue life prediction model that can be applicable for ductile and brittle materials. The fatigue life prediction model based on the proposed high-cycle multiaxial fatigue criterion was validated with experimental results obtained from the test of 7075-T651 aluminum alloy and some references.

  10. Proprietary software

    NASA Technical Reports Server (NTRS)

    Marnock, M. J.

    1971-01-01

    The protection of intellectual property by a patent, a copyright, or trade secrets is reviewed. The present and future use of computers and software are discussed, along with the governmental uses of software. The popularity of contractual agreements for sale or lease of computer programs and software services is also summarized.

  11. The Evolutionary Fate of Phenotypic Plasticity and Functional Traits under Domestication in Manioc: Changes in Stem Biomechanics and the Appearance of Stem Brittleness

    PubMed Central

    Ménard, Léa; McKey, Doyle; Mühlen, Gilda S.; Clair, Bruno; Rowe, Nick P.

    2013-01-01

    Domestication can influence many functional traits in plants, from overall life-history and growth form to wood density and cell wall ultrastructure. Such changes can increase fitness of the domesticate in agricultural environments but may negatively affect survival in the wild. We studied effects of domestication on stem biomechanics in manioc by comparing domesticated and ancestral wild taxa from two different regions of greater Amazonia. We compared mechanical properties, tissue organisation and wood characteristics including microfibril angles in both wild and domesticated plants, each growing in two different habitats (forest or savannah) and varying in growth form (shrub or liana). Wild taxa grew as shrubs in open savannah but as lianas in overgrown and forested habitats. Growth form plasticity was retained in domesticated manioc. However, stems of the domesticate showed brittle failure. Wild plants differed in mechanical architecture between shrub and liana phenotypes, a difference that diminished between shrubs and lianas of the domesticate. Stems of wild plants were generally stiffer, failed at higher bending stresses and were less prone to brittle fracture compared with shrub and liana phenotypes of the domesticate. Biomechanical differences between stems of wild and domesticated plants were mainly due to changes in wood density and cellulose microfibril angle rather than changes in secondary growth or tissue geometry. Domestication did not significantly modify “large-scale” trait development or growth form plasticity, since both wild and domesticated manioc can develop as shrubs or lianas. However, “finer-scale” developmental traits crucial to mechanical stability and thus ecological success of the plant were significantly modified. This profoundly influenced the likelihood of brittle failure, particularly in long climbing stems, thereby also influencing the survival of the domesticate in natural situations vulnerable to mechanical perturbation

  12. Revealing stiffening and brittling of chronic myelogenous leukemia hematopoietic primary cells through their temporal response to shear stress.

    PubMed

    Laperrousaz, B; Berguiga, L; Nicolini, F E; Martinez-Torres, C; Arneodo, A; Satta, V Maguer; Argoul, F

    2016-06-02

    Cancer cell transformation is often accompanied by a modification of their viscoelastic properties. When capturing the stress-to-strain response of primary chronic myelogenous leukemia (CML) cells, from two data sets of CD34+ hematopoietic cells isolated from healthy and leukemic bone marrows, we show that the mean shear relaxation modulus increases upon cancer transformation. This stiffening of the cells comes along with local rupture events, detected as reinforced sharp local maxima of this modulus, suggesting that these cancer cells respond to a local mechanical stress by a cascade of local brittle failure events.

  13. Revealing stiffening and brittling of chronic myelogenous leukemia hematopoietic primary cells through their temporal response to shear stress

    NASA Astrophysics Data System (ADS)

    Laperrousaz, B.; Berguiga, L.; Nicolini, F. E.; Martinez-Torres, C.; Arneodo, A.; Maguer Satta, V.; Argoul, F.

    2016-06-01

    Cancer cell transformation is often accompanied by a modification of their viscoelastic properties. When capturing the stress-to-strain response of primary chronic myelogenous leukemia (CML) cells, from two data sets of CD34+ hematopoietic cells isolated from healthy and leukemic bone marrows, we show that the mean shear relaxation modulus increases upon cancer transformation. This stiffening of the cells comes along with local rupture events, detected as reinforced sharp local maxima of this modulus, suggesting that these cancer cells respond to a local mechanical stress by a cascade of local brittle failure events.

  14. Using software metrics and software reliability models to attain acceptable quality software for flight and ground support software for avionic systems

    NASA Technical Reports Server (NTRS)

    Lawrence, Stella

    1992-01-01

    This paper is concerned with methods of measuring and developing quality software. Reliable flight and ground support software is a highly important factor in the successful operation of the space shuttle program. Reliability is probably the most important of the characteristics inherent in the concept of 'software quality'. It is the probability of failure free operation of a computer program for a specified time and environment.

  15. Near real-time, on-the-move software PED using VPEF

    NASA Astrophysics Data System (ADS)

    Green, Kevin; Geyer, Chris; Burnette, Chris; Agarwal, Sanjeev; Swett, Bruce; Phan, Chung; Deterline, Diane

    2015-05-01

    The scope of the Micro-Cloud for Operational, Vehicle-Based EO-IR Reconnaissance System (MOVERS) development effort, managed by the Night Vision and Electronic Sensors Directorate (NVESD), is to develop, integrate, and demonstrate new sensor technologies and algorithms that improve improvised device/mine detection using efficient and effective exploitation and fusion of sensor data and target cues from existing and future Route Clearance Package (RCP) sensor systems. Unfortunately, the majority of forward looking Full Motion Video (FMV) and computer vision processing, exploitation, and dissemination (PED) algorithms are often developed using proprietary, incompatible software. This makes the insertion of new algorithms difficult due to the lack of standardized processing chains. In order to overcome these limitations, EOIR developed the Government off-the-shelf (GOTS) Video Processing and Exploitation Framework (VPEF) to be able to provide standardized interfaces (e.g., input/output video formats, sensor metadata, and detected objects) for exploitation software and to rapidly integrate and test computer vision algorithms. EOIR developed a vehicle-based computing framework within the MOVERS and integrated it with VPEF. VPEF was further enhanced for automated processing, detection, and publishing of detections in near real-time, thus improving the efficiency and effectiveness of RCP sensor systems.

  16. Software verification plan for GCS. [guidance and control software

    NASA Technical Reports Server (NTRS)

    Dent, Leslie A.; Shagnea, Anita M.; Hayhurst, Kelly J.

    1990-01-01

    This verification plan is written as part of an experiment designed to study the fundamental characteristics of the software failure process. The experiment will be conducted using several implementations of software that were produced according to industry-standard guidelines, namely the Radio Technical Commission for Aeronautics RTCA/DO-178A guidelines, Software Consideration in Airborne Systems and Equipment Certification, for the development of flight software. This plan fulfills the DO-178A requirements for providing instructions on the testing of each implementation of software. The plan details the verification activities to be performed at each phase in the development process, contains a step by step description of the testing procedures, and discusses all of the tools used throughout the verification process.

  17. SG2PS (structural geology to postscript converter) - A graphical solution for brittle structural data evaluation and paleostress calculation

    NASA Astrophysics Data System (ADS)

    Sasvári, Ágoston; Baharev, Ali

    2014-05-01

    The aim of this work was to create an open source cross platform application to process brittle structural geological data with seven paleostress inversion algorithms published by different authors and formerly not available within a single desktop application. The tool facilitates separate processing and plotting of different localities, data types and user made groups, using the same single input file. Simplified data input is supported, requiring as small amount of data as possible. Data rotation to correct for bedding tilting, rotation with paleomagnetic declination and k-means clustering are available. RUP and ANG stress estimators calculation and visualization, resolved shear direction display and Mohr circle stress visualization are available. RGB-colored vector graphical outputs are automatically generated in Encapsulated PostScript and Portable Document Format. Stereographical displays on great circle or pole point plot, equal area or equal angle net and upper or lower hemisphere projections are implemented. Rose plots displaying dip direction or strike, with dip angle distribution of the input data set are available. This tool is ideal for preliminary data interpretation on the field (quick processing and visualization in seconds); the implemented methods can be regularly used in the daily academic and industrial work as well. The authors' goal was to create an open source and self-contained desktop application that does not require any additional third party framework (such as .NET) or the Java Virtual Machine. The software has a clear and highly modular structure enabling good code portability, easy maintainability, reusability and extensibility. A Windows installer is publicly available and the program is also fully functional on Linux. The Mac OS X port should be feasible with minimal effort. The install file with test and demo data sets, detailed manual, and links to the GitHub repositories are available on the regularly updated website www.sg2ps.eu.

  18. Payload software technology: Software technology development plan

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Programmatic requirements for the advancement of software technology are identified for meeting the space flight requirements in the 1980 to 1990 time period. The development items are described, and software technology item derivation worksheets are presented along with the cost/time/priority assessments.

  19. Overcoming default categorical bias in spatial memory.

    PubMed

    Sampaio, Cristina; Wang, Ranxiao Frances

    2010-12-01

    In the present study, we investigated whether a strong default categorical bias can be overcome in spatial memory by using alternative membership information. In three experiments, we tested location memory in a circular space while providing participants with an alternative categorization. We found that visual presentation of the boundaries of the alternative categories (Experiment 1) did not induce the use of the alternative categories in estimation. In contrast, visual cuing of the alternative category membership of a target (Experiment 2) and unique target feature information associated with each alternative category (Experiment 3) successfully led to the use of the alternative categories in estimation. Taken together, the results indicate that default categorical bias in spatial memory can be overcome when appropriate cues are provided. We discuss how these findings expand the category adjustment model (Huttenlocher, Hedges, & Duncan, 1991) in spatial memory by proposing a retrieval-based category adjustment (RCA) model.

  20. Healthcare software assurance.

    PubMed

    Cooper, Jason G; Pauley, Keith A

    2006-01-01

    Software assurance is a rigorous, lifecycle phase-independent set of activities which ensure completeness, safety, and reliability of software processes and products. This is accomplished by guaranteeing conformance to all requirements, standards, procedures, and regulations. These assurance processes are even more important when coupled with healthcare software systems, embedded software in medical instrumentation, and other healthcare-oriented life-critical systems. The current Food and Drug Administration (FDA) regulatory requirements and guidance documentation do not address certain aspects of complete software assurance activities. In addition, the FDA's software oversight processes require enhancement to include increasingly complex healthcare systems such as Hospital Information Systems (HIS). The importance of complete software assurance is introduced, current regulatory requirements and guidance discussed, and the necessity for enhancements to the current processes shall be highlighted.

  1. Healthcare Software Assurance

    PubMed Central

    Cooper, Jason G.; Pauley, Keith A.

    2006-01-01

    Software assurance is a rigorous, lifecycle phase-independent set of activities which ensure completeness, safety, and reliability of software processes and products. This is accomplished by guaranteeing conformance to all requirements, standards, procedures, and regulations. These assurance processes are even more important when coupled with healthcare software systems, embedded software in medical instrumentation, and other healthcare-oriented life-critical systems. The current Food and Drug Administration (FDA) regulatory requirements and guidance documentation do not address certain aspects of complete software assurance activities. In addition, the FDA’s software oversight processes require enhancement to include increasingly complex healthcare systems such as Hospital Information Systems (HIS). The importance of complete software assurance is introduced, current regulatory requirements and guidance discussed, and the necessity for enhancements to the current processes shall be highlighted. PMID:17238324

  2. Framework for Small-Scale Experiments in Software Engineering: Guidance and Control Software Project: Software Engineering Case Study

    NASA Technical Reports Server (NTRS)

    Hayhurst, Kelly J.

    1998-01-01

    Software is becoming increasingly significant in today's critical avionics systems. To achieve safe, reliable software, government regulatory agencies such as the Federal Aviation Administration (FAA) and the Department of Defense mandate the use of certain software development methods. However, little scientific evidence exists to show a correlation between software development methods and product quality. Given this lack of evidence, a series of experiments has been conducted to understand why and how software fails. The Guidance and Control Software (GCS) project is the latest in this series. The GCS project is a case study of the Requirements and Technical Concepts for Aviation RTCA/DO-178B guidelines, Software Considerations in Airborne Systems and Equipment Certification. All civil transport airframe and equipment vendors are expected to comply with these guidelines in building systems to be certified by the FAA for use in commercial aircraft. For the case study, two implementations of a guidance and control application were developed to comply with the DO-178B guidelines for Level A (critical) software. The development included the requirements, design, coding, verification, configuration management, and quality assurance processes. This paper discusses the details of the GCS project and presents the results of the case study.

  3. Statistical Software Engineering

    DTIC Science & Technology

    1998-04-13

    multiversion software subject to coincident errors. IEEE Trans. Software Eng. SE-11:1511-1517. Eckhardt, D.E., A.K Caglayan, J.C. Knight, L.D. Lee, D.F...J.C. and N.G. Leveson. 1986. Experimental evaluation of the assumption of independence in multiversion software. IEEE Trans. Software

  4. Fracture Property of Y-Shaped Cracks of Brittle Materials under Compression

    PubMed Central

    Zhang, Xiaoyan; Zhu, Zheming; Liu, Hongjie

    2014-01-01

    In order to investigate the properties of Y-shaped cracks of brittle materials under compression, compression tests by using square cement mortar specimens with Y-shaped crack were conducted. A true triaxial loading device was applied in the tests, and the major principle stresses or the critical stresses were measured. The results show that as the branch angle θ between the branch crack and the stem crack is 75°, the cracked specimen has the lowest strength. In order to explain the test results, numerical models of Y-shaped cracks by using ABAQUS code were established, and the J-integral method was applied in calculating crack tip stress intensity factor (SIF). The results show that when the branch angle θ increases, the SIF K I of the branch crack increases from negative to positive and the absolute value K II of the branch crack first increases, and as θ is 50°, it is the maximum, and then it decreases. Finally, in order to further investigate the stress distribution around Y-shaped cracks, photoelastic tests were conducted, and the test results generally agree with the compressive test results. PMID:25013846

  5. Northwestern University Schizophrenia Data and Software Tool (NUSDAST)

    PubMed Central

    Wang, Lei; Kogan, Alex; Cobia, Derin; Alpert, Kathryn; Kolasny, Anthony; Miller, Michael I.; Marcus, Daniel

    2013-01-01

    The schizophrenia research community has invested substantial resources on collecting, managing and sharing large neuroimaging datasets. As part of this effort, our group has collected high resolution magnetic resonance (MR) datasets from individuals with schizophrenia, their non-psychotic siblings, healthy controls and their siblings. This effort has resulted in a growing resource, the Northwestern University Schizophrenia Data and Software Tool (NUSDAST), an NIH-funded data sharing project to stimulate new research. This resource resides on XNAT Central, and it contains neuroimaging (MR scans, landmarks and surface maps for deep subcortical structures, and FreeSurfer cortical parcellation and measurement data), cognitive (cognitive domain scores for crystallized intelligence, working memory, episodic memory, and executive function), clinical (demographic, sibling relationship, SAPS and SANS psychopathology), and genetic (20 polymorphisms) data, collected from more than 450 subjects, most with 2-year longitudinal follow-up. A neuroimaging mapping, analysis and visualization software tool, CAWorks, is also part of this resource. Moreover, in making our existing neuroimaging data along with the associated meta-data and computational tools publically accessible, we have established a web-based information retrieval portal that allows the user to efficiently search the collection. This research-ready dataset meaningfully combines neuroimaging data with other relevant information, and it can be used to help facilitate advancing neuroimaging research. It is our hope that this effort will help to overcome some of the commonly recognized technical barriers in advancing neuroimaging research such as lack of local organization and standard descriptions. PMID:24223551

  6. Northwestern University Schizophrenia Data and Software Tool (NUSDAST).

    PubMed

    Wang, Lei; Kogan, Alex; Cobia, Derin; Alpert, Kathryn; Kolasny, Anthony; Miller, Michael I; Marcus, Daniel

    2013-01-01

    The schizophrenia research community has invested substantial resources on collecting, managing and sharing large neuroimaging datasets. As part of this effort, our group has collected high resolution magnetic resonance (MR) datasets from individuals with schizophrenia, their non-psychotic siblings, healthy controls and their siblings. This effort has resulted in a growing resource, the Northwestern University Schizophrenia Data and Software Tool (NUSDAST), an NIH-funded data sharing project to stimulate new research. This resource resides on XNAT Central, and it contains neuroimaging (MR scans, landmarks and surface maps for deep subcortical structures, and FreeSurfer cortical parcellation and measurement data), cognitive (cognitive domain scores for crystallized intelligence, working memory, episodic memory, and executive function), clinical (demographic, sibling relationship, SAPS and SANS psychopathology), and genetic (20 polymorphisms) data, collected from more than 450 subjects, most with 2-year longitudinal follow-up. A neuroimaging mapping, analysis and visualization software tool, CAWorks, is also part of this resource. Moreover, in making our existing neuroimaging data along with the associated meta-data and computational tools publically accessible, we have established a web-based information retrieval portal that allows the user to efficiently search the collection. This research-ready dataset meaningfully combines neuroimaging data with other relevant information, and it can be used to help facilitate advancing neuroimaging research. It is our hope that this effort will help to overcome some of the commonly recognized technical barriers in advancing neuroimaging research such as lack of local organization and standard descriptions.

  7. Brittle deformation during Alpine basal accretion and the origin of seismicity nests above the subduction interface

    NASA Astrophysics Data System (ADS)

    Menant, Armel; Angiboust, Samuel; Monié, Patrick; Oncken, Onno; Guigner, Jean-Michel

    2018-04-01

    Geophysical observations on active subduction zones have evidenced high seismicity clusters at 20-40 km depth in the fore-arc region whose origin remains controversial. We report here field observations of pervasive pseudotachylyte networks (interpreted as evidence for paleo-seismicity) in the now-exhumed Valpelline continental unit (Dent Blanche complex, NW. Alps, Italy), a tectonic sliver accreted to the upper plate at c. 30 km depth during the Paleocene Alpine subduction. Pre-alpine granulite-facies paragneiss from the core of the Valpelline unit are crosscut by widespread, mm to cm-thick pseudotachylyte veins. Co-seismic heating and subsequent cooling led to the formation of Ti-rich garnet rims, ilmenite needles, Ca-rich plagioclase, biotite microliths and hercynite micro-crystals. 39Ar-40Ar dating yields a 51-54 Ma age range for these veins, thus suggesting that frictional melting events occurred near peak burial conditions while the Valpelline unit was already inserted inside the duplex structure. In contrast, the base of the Valpelline unit underwent synchronous ductile and brittle, seismic deformation under water-bearing conditions followed by a re-equilibration at c. 40 Ma (39Ar-40Ar on retrograded pseudotachylyte veins) during exhumation-related deformation. Calculated rheological profiles suggest that pseudotachylyte veins from the dry core of the granulite unit record upper plate micro-seismicity (Mw 2-3) formed under very high differential stresses (>500 MPa) while the sheared base of the unit underwent repeated brittle-ductile deformation at much lower differential stresses (<40 MPa) in a fluid-saturated environment. These results demonstrate that some of the seismicity clusters nested along and above the plate interface may reflect the presence of stiff tectonic slivers rheologically analogous to the Valpelline unit acting as repeatedly breaking asperities in the basal accretion region of active subduction zones.

  8. Validation of a New Elastoplastic Constitutive Model Dedicated to the Cyclic Behaviour of Brittle Rock Materials

    NASA Astrophysics Data System (ADS)

    Cerfontaine, B.; Charlier, R.; Collin, F.; Taiebat, M.

    2017-10-01

    Old mines or caverns may be used as reservoirs for fuel/gas storage or in the context of large-scale energy storage. In the first case, oil or gas is stored on annual basis. In the second case pressure due to water or compressed air varies on a daily basis or even faster. In both cases a cyclic loading on the cavern's/mine's walls must be considered for the design. The complexity of rockwork geometries or coupling with water flow requires finite element modelling and then a suitable constitutive law for the rock behaviour modelling. This paper presents and validates the formulation of a new constitutive law able to represent the inherently cyclic behaviour of rocks at low confinement. The main features of the behaviour evidenced by experiments in the literature depict a progressive degradation and strain of the material with the number of cycles. A constitutive law based on a boundary surface concept is developed. It represents the brittle failure of the material as well as its progressive degradation. Kinematic hardening of the yield surface allows the modelling of cycles. Isotropic softening on the cohesion variable leads to the progressive degradation of the rock strength. A limit surface is introduced and has a lower opening than the bounding surface. This surface describes the peak strength of the material and allows the modelling of a brittle behaviour. In addition a fatigue limit is introduced such that no cohesion degradation occurs if the stress state lies inside this surface. The model is validated against three different rock materials and types of experiments. Parameters of the constitutive laws are calibrated against uniaxial tests on Lorano marble, triaxial test on a sandstone and damage-controlled test on Lac du Bonnet granite. The model is shown to reproduce correctly experimental results, especially the evolution of strain with number of cycles.

  9. Sesquiterpenes with TRAIL-resistance overcoming activity from Xanthium strumarium.

    PubMed

    Karmakar, Utpal K; Ishikawa, Naoki; Toume, Kazufumi; Arai, Midori A; Sadhu, Samir K; Ahmed, Firoj; Ishibashi, Masami

    2015-08-01

    The ability of TRAIL to selectively induce apoptosis in cancer cells while sparing normal cells makes it an attractive target for the development of new cancer therapy. In search of bioactive natural products for overcoming TRAIL-resistance from natural resources, we previously reported a number of active compounds. In our screening program on natural resources targeting overcoming TRAIL-resistance, activity-guided fractionations of the extract of Xanthium strumarium led to the isolation of five sesquiterpene compounds (1-5). 11α,13-dihydroxanthinin (2) and 11α,13-dihydroxanthuminol (3) were first isolated from natural resources and xanthinosin (1), desacetylxanthanol (4), and lasidiol p-methoxybenzoate (5) were known compounds. All compounds (1-5) showed potent TRAIL-resistance overcoming activity at 8, 20, 20, 16, and 16 μM, respectively, in TRAIL-resistant AGS cells. Compounds 1 and 5 enhanced the levels of apoptosis inducing proteins DR4, DR5, p53, CHOP, Bax, cleaved caspase-3, cleaved caspase-8, and cleaved caspase-9 and also decreased the levels of cell survival protein Bcl-2 in TRAIL-resistant AGS cells in a dose-dependent manner. Compound 1 also enhanced the levels of DR4 and DR5 proteins in a time-dependent manner. Thus, compounds 1 and 5 were found to induce both extrinsic and intrinsic apoptotic cell death. Compound 1 also exhibit TRAIL-resistance overcoming activity in DLD1, DU145, HeLa, and MCF7 cells but did not decrease viability in non-cancer HEK293 cells up to 8 μM. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Overcoming Learned Helplessness in Community College Students.

    ERIC Educational Resources Information Center

    Roueche, John E.; Mink, Oscar G.

    1982-01-01

    Reviews research on the effects of repeated experiences of helplessness and on locus of control. Identifies conditions necessary for overcoming learned helplessness; i.e., the potential for learning to occur; consistent reinforcement; relevant, valued reinforcers; and favorable psychological situation. Recommends eight ways for teachers to…

  11. Commercial Literacy Software.

    ERIC Educational Resources Information Center

    Balajthy, Ernest

    1997-01-01

    Presents the first year's results of a continuing project to monitor the availability of software of relevance for literacy education purposes. Concludes there is an enormous amount of software available for use by teachers of reading and literacy--whereas drill-and-practice software is the largest category of software available, large numbers of…

  12. Software Configuration Management Guidebook

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The growth in cost and importance of software to NASA has caused NASA to address the improvement of software development across the agency. One of the products of this program is a series of guidebooks that define a NASA concept of the assurance processes which are used in software development. The Software Assurance Guidebook, SMAP-GB-A201, issued in September, 1989, provides an overall picture of the concepts and practices of NASA in software assurance. Lower level guidebooks focus on specific activities that fall within the software assurance discipline, and provide more detailed information for the manager and/or practitioner. This is the Software Configuration Management Guidebook which describes software configuration management in a way that is compatible with practices in industry and at NASA Centers. Software configuration management is a key software development process, and is essential for doing software assurance.

  13. Accounting for Uncertainties in Strengths of SiC MEMS Parts

    NASA Technical Reports Server (NTRS)

    Nemeth, Noel; Evans, Laura; Beheim, Glen; Trapp, Mark; Jadaan, Osama; Sharpe, William N., Jr.

    2007-01-01

    A methodology has been devised for accounting for uncertainties in the strengths of silicon carbide structural components of microelectromechanical systems (MEMS). The methodology enables prediction of the probabilistic strengths of complexly shaped MEMS parts using data from tests of simple specimens. This methodology is intended to serve as a part of a rational basis for designing SiC MEMS, supplementing methodologies that have been borrowed from the art of designing macroscopic brittle material structures. The need for this or a similar methodology arises as a consequence of the fundamental nature of MEMS and the brittle silicon-based materials of which they are typically fabricated. When tested to fracture, MEMS and structural components thereof show wide part-to-part scatter in strength. The methodology involves the use of the Ceramics Analysis and Reliability Evaluation of Structures Life (CARES/Life) software in conjunction with the ANSYS Probabilistic Design System (PDS) software to simulate or predict the strength responses of brittle material components while simultaneously accounting for the effects of variability of geometrical features on the strength responses. As such, the methodology involves the use of an extended version of the ANSYS/CARES/PDS software system described in Probabilistic Prediction of Lifetimes of Ceramic Parts (LEW-17682-1/4-1), Software Tech Briefs supplement to NASA Tech Briefs, Vol. 30, No. 9 (September 2006), page 10. The ANSYS PDS software enables the ANSYS finite-element-analysis program to account for uncertainty in the design-and analysis process. The ANSYS PDS software accounts for uncertainty in material properties, dimensions, and loading by assigning probabilistic distributions to user-specified model parameters and performing simulations using various sampling techniques.

  14. Software Quality Assurance Metrics

    NASA Technical Reports Server (NTRS)

    McRae, Kalindra A.

    2004-01-01

    Software Quality Assurance (SQA) is a planned and systematic set of activities that ensures conformance of software life cycle processes and products conform to requirements, standards and procedures. In software development, software quality means meeting requirements and a degree of excellence and refinement of a project or product. Software Quality is a set of attributes of a software product by which its quality is described and evaluated. The set of attributes includes functionality, reliability, usability, efficiency, maintainability, and portability. Software Metrics help us understand the technical process that is used to develop a product. The process is measured to improve it and the product is measured to increase quality throughout the life cycle of software. Software Metrics are measurements of the quality of software. Software is measured to indicate the quality of the product, to assess the productivity of the people who produce the product, to assess the benefits derived from new software engineering methods and tools, to form a baseline for estimation, and to help justify requests for new tools or additional training. Any part of the software development can be measured. If Software Metrics are implemented in software development, it can save time, money, and allow the organization to identify the caused of defects which have the greatest effect on software development. The summer of 2004, I worked with Cynthia Calhoun and Frank Robinson in the Software Assurance/Risk Management department. My task was to research and collect, compile, and analyze SQA Metrics that have been used in other projects that are not currently being used by the SA team and report them to the Software Assurance team to see if any metrics can be implemented in their software assurance life cycle process.

  15. Incorporation of the NAG-FRAG Model for Ductile and Brittle Fracture into Help, a 2D Multimaterial Eulerian Program

    DTIC Science & Technology

    1978-09-01

    Models HELP Ductile Material HEMP Brittle Material PUFF Iron Aluminum Eulerian Codea Tap«.r«»H Flyor Pl^«-» rmp«^» tO. ABITRACT (Conllmjm M r«v... HEMP ) code with those obtained by the Eulerian (HELP) code 5.3 Relative void volume of damage regions at three times after impact in the 1145...plate calculation 5.5 Relative void volume of material in the 1145 aluminum target at 1.46 us after impact as computed by the Lagrangian ( HEMP

  16. Software Quality Perceptions of Stakeholders Involved in the Software Development Process

    ERIC Educational Resources Information Center

    Padmanabhan, Priya

    2013-01-01

    Software quality is one of the primary determinants of project management success. Stakeholders involved in software development widely agree that quality is important (Barney and Wohlin 2009). However, they may differ on what constitutes software quality, and which of its attributes are more important than others. Although, software quality…

  17. Software Reliability Analysis of NASA Space Flight Software: A Practical Experience

    PubMed Central

    Sukhwani, Harish; Alonso, Javier; Trivedi, Kishor S.; Mcginnis, Issac

    2017-01-01

    In this paper, we present the software reliability analysis of the flight software of a recently launched space mission. For our analysis, we use the defect reports collected during the flight software development. We find that this software was developed in multiple releases, each release spanning across all software life-cycle phases. We also find that the software releases were developed and tested for four different hardware platforms, spanning from off-the-shelf or emulation hardware to actual flight hardware. For releases that exhibit reliability growth or decay, we fit Software Reliability Growth Models (SRGM); otherwise we fit a distribution function. We find that most releases exhibit reliability growth, with Log-Logistic (NHPP) and S-Shaped (NHPP) as the best-fit SRGMs. For the releases that experience reliability decay, we investigate the causes for the same. We find that such releases were the first software releases to be tested on a new hardware platform, and hence they encountered major hardware integration issues. Also such releases seem to have been developed under time pressure in order to start testing on the new hardware platform sooner. Such releases exhibit poor reliability growth, and hence exhibit high predicted failure rate. Other problems include hardware specification changes and delivery delays from vendors. Thus, our analysis provides critical insights and inputs to the management to improve the software development process. As NASA has moved towards a product line engineering for its flight software development, software for future space missions will be developed in a similar manner and hence the analysis results for this mission can be considered as a baseline for future flight software missions. PMID:29278255

  18. Software Reliability Analysis of NASA Space Flight Software: A Practical Experience.

    PubMed

    Sukhwani, Harish; Alonso, Javier; Trivedi, Kishor S; Mcginnis, Issac

    2016-01-01

    In this paper, we present the software reliability analysis of the flight software of a recently launched space mission. For our analysis, we use the defect reports collected during the flight software development. We find that this software was developed in multiple releases, each release spanning across all software life-cycle phases. We also find that the software releases were developed and tested for four different hardware platforms, spanning from off-the-shelf or emulation hardware to actual flight hardware. For releases that exhibit reliability growth or decay, we fit Software Reliability Growth Models (SRGM); otherwise we fit a distribution function. We find that most releases exhibit reliability growth, with Log-Logistic (NHPP) and S-Shaped (NHPP) as the best-fit SRGMs. For the releases that experience reliability decay, we investigate the causes for the same. We find that such releases were the first software releases to be tested on a new hardware platform, and hence they encountered major hardware integration issues. Also such releases seem to have been developed under time pressure in order to start testing on the new hardware platform sooner. Such releases exhibit poor reliability growth, and hence exhibit high predicted failure rate. Other problems include hardware specification changes and delivery delays from vendors. Thus, our analysis provides critical insights and inputs to the management to improve the software development process. As NASA has moved towards a product line engineering for its flight software development, software for future space missions will be developed in a similar manner and hence the analysis results for this mission can be considered as a baseline for future flight software missions.

  19. Space Station Software Issues

    NASA Technical Reports Server (NTRS)

    Voigt, S. (Editor); Beskenis, S. (Editor)

    1985-01-01

    Issues in the development of software for the Space Station are discussed. Software acquisition and management, software development environment, standards, information system support for software developers, and a future software advisory board are addressed.

  20. Agile Software Development

    ERIC Educational Resources Information Center

    Biju, Soly Mathew

    2008-01-01

    Many software development firms are now adopting the agile software development method. This method involves the customer at every level of software development, thus reducing the impact of change in the requirement at a later stage. In this article, the principles of the agile method for software development are explored and there is a focus on…

  1. Migration of the Gaudi and LHCb software repositories from CVS to Subversion

    NASA Astrophysics Data System (ADS)

    Clemencic, M.; Degaudenzi, H.; LHCb Collaboration

    2011-12-01

    A common code repository is of primary importance in a distributed development environment such as large HEP experiments. CVS (Concurrent Versions System) has been used in the past years at CERN for the hosting of shared software repositories, among which were the repositories for the Gaudi Framework and the LHCb software projects. Many developers around the world produced alternative systems to share code and revisions among several developers, mainly to overcome the limitations in CVS, and CERN has recently started a new service for code hosting based on the version control system Subversion. The differences between CVS and Subversion and the way the code was organized in Gaudi and LHCb CVS repositories required careful study and planning of the migration. Special care was used to define the organization of the new Subversion repository. To avoid as much as possible disruption in the development cycle, the migration has been gradual with the help of tools developed explicitly to hide the differences between the two systems. The principles guiding the migration steps, the organization of the Subversion repository and the tools developed will be presented, as well as the problems encountered both from the librarian and the user points of view.

  2. Investigation of the physico-chemical and mechanical properties of hard brittle shales from the Shahejie Formation in the Nanpu Sag, northern China

    NASA Astrophysics Data System (ADS)

    Xiangjun, Liu; Jian, Xiong; Lixi, Liang; Yi, Ding

    2017-06-01

    With increasing demand for energy and advances in exploration and development technologies, more attention is being devoted to exploration and development of deep oil and gas reservoirs. The Nanpu Sag contains huge reserves in deep oil and gas reservoirs and is a promising area. In this paper, the physico-chemical and mechanical properties of hard brittle shales from the Shahejie Formation in the Nanpu Sag in the Bohai Bay Basin of northern China were investigated using a variety of methods, including x-ray diffraction analysis, cation exchange capacity (CEC) analysis, contact angle measurements, scanning electron microscope observations, immersion experiments, ultrasonic testing and mechanical testing. The effects of the physico-chemical properties of the shales on wellbore instability were observed, and the effects of hydration of the shales on wellbore instability were also examined. The results show that the major mineral constituents of the investigated shales are quartz and clay minerals. The clay mineral contents range from 25.33% to 52.03%, and the quartz contents range from 20.03% to 46.45%. The clay minerals do not include montmorillonite, but large amounts of mixed-layer illite/smectite were observed. The CEC values of the shales range from 90 to 210 mmol kg-1, indicating that the shales are partly hydrated. The wettability of the shales is strongly water-wetted, indicating that water would enter the shales due to the capillary effect. Hydration of hard brittle shales can generate cracks, leading to changes in microstructure and increases in the acoustic value, which could generate damage in the shales and reduce their strength. With increasing hydration time, the shale hydration effect gradually becomes stronger, causing an increase in the range of the acoustic travel time and decreases in the ranges of cohesion and internal friction angles. For the hard brittle shales of the Nanpu Sag, drilling fluid systems should aim to enhance sealing ability

  3. Payload software technology

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A software analysis was performed of known STS sortie payload elements and their associated experiments. This provided basic data for STS payload software characteristics and sizes. A set of technology drivers was identified based on a survey of future technology needs and an assessment of current software technology. The results will be used to evolve a planned approach to software technology development. The purpose of this plan is to ensure that software technology is advanced at a pace and a depth sufficient to fulfill the identified future needs.

  4. Objections to tubal sterilization: what reversibility can and cannot overcome.

    PubMed

    Shain, R N

    1980-09-01

    In a study of 1074 women, 696 and 338 subjects would not seriously consider permanent and hypothetically reversible sterilization, respectively; they were asked to explain their feelings. The reason accounting for most objections to permanent sterilization (65%) was irreversibility and of the subjects who would not consider reversible sterilization or were unsure, 42.7% attributed their principal objection to unnecessary surgery, a factor at least currently intrinsic to the procedure and not readily overcome by education. Many of the remaining objections to both permanent and reversible sterilization may be amenable to change either through education or financial subsidies. In response to a question concerning female attractiveness subsequent to permanent sterilization, 3% of the sample felt attractiveness would decrease and 17.5% were unsure of the surgery's effect. Unsure responses were largely negative in character. This issue is important because of its relationship to intention to undergo sterilization. Upon consideration of reversible sterilization, negative and unsure responses significantly declined, even on the part of those women whose friends have had a poor experience with currently available procedures. Thus, whereas the option of reversibility cannot overcome objections to surgery, it does overcome those regarding permanency; moreover, the "temporary" character it bestows upon surgical sterilization appears to help certain individuals overcome their fears of losing their physical appeal as a result of such procedures.

  5. Oscillating brittle and viscous behavior through the earthquake cycle in the Red River Shear Zone: Monitoring flips between reaction and textural softening and hardening

    NASA Astrophysics Data System (ADS)

    Wintsch, Robert P.; Yeh, Meng-Wan

    2013-03-01

    Microstructures associated with cataclasites and mylonites in the Red River shear zone in the Diancang Shan block, Yunnan Province, China show evidence for both reaction hardening and softening at lower greenschist facies metamorphic conditions. The earliest fault-rocks derived from Triassic porphyritic orthogneiss protoliths are cataclasites. Brittle fractures and crushed grains are cemented by newly precipitated quartz. These cataclasites are subsequently overprinted by mylonitic fabrics. Truncations and embayments of relic feldspars and biotites show that these protolith minerals have been dissolved and incompletely replaced by muscovite, chlorite, and quartz. Both K-feldspar and plagioclase porphyroclasts are truncated by muscovite alone, suggesting locally metasomatic reactions of the form: 3K-feldspar + 2H+ = muscovite + 6SiO2(aq) + 2K+. Such reactions produce muscovite folia and fish, and quartz bands and ribbons. Muscovite and quartz are much weaker than the reactant feldspars and these reactions result in reaction softening. Moreover, the muscovite tends to align in contiguous bands that constitute textural softening. These mineral and textural modifications occurred at constant temperature and drove the transition from brittle to viscous deformation and the shift in deformation mechanism from cataclasis to dissolution-precipitation and reaction creep. These mylonitic rocks so produced are cut by K-feldspar veins that interrupt the mylonitic fabric. The veins add K-feldspar to the assemblage and these structures constitute both reaction and textural hardening. Finally these veins are boudinaged by continued viscous deformation in the mylonitic matrix, thus defining a late ductile strain event. Together these overprinting textures and microstructures demonstrate several oscillations between brittle and viscous deformation, all at lower greenschist facies conditions where only frictional behavior is predicted by experiments. The overlap of the depths of

  6. MPA Portable: A Stand-Alone Software Package for Analyzing Metaproteome Samples on the Go.

    PubMed

    Muth, Thilo; Kohrs, Fabian; Heyer, Robert; Benndorf, Dirk; Rapp, Erdmann; Reichl, Udo; Martens, Lennart; Renard, Bernhard Y

    2018-01-02

    Metaproteomics, the mass spectrometry-based analysis of proteins from multispecies samples faces severe challenges concerning data analysis and results interpretation. To overcome these shortcomings, we here introduce the MetaProteomeAnalyzer (MPA) Portable software. In contrast to the original server-based MPA application, this newly developed tool no longer requires computational expertise for installation and is now independent of any relational database system. In addition, MPA Portable now supports state-of-the-art database search engines and a convenient command line interface for high-performance data processing tasks. While search engine results can easily be combined to increase the protein identification yield, an additional two-step workflow is implemented to provide sufficient analysis resolution for further postprocessing steps, such as protein grouping as well as taxonomic and functional annotation. Our new application has been developed with a focus on intuitive usability, adherence to data standards, and adaptation to Web-based workflow platforms. The open source software package can be found at https://github.com/compomics/meta-proteome-analyzer .

  7. The Elements of an Effective Software Development Plan - Software Development Process Guidebook

    DTIC Science & Technology

    2011-11-11

    standards and practices required for all XMPL software development. This SDP implements the <corporate> Standard Software Process (SSP). as tailored...Developing and integrating reusable software products • Approach to managing COTS/Reuse software implementation • COTS/Reuse software selection...final selection and submit to change board for approval MAINTENANCE Monitor current products for obsolescence or end of support Track new

  8. Report: Scientific Software.

    ERIC Educational Resources Information Center

    Borman, Stuart A.

    1985-01-01

    Discusses various aspects of scientific software, including evaluation and selection of commercial software products; program exchanges, catalogs, and other information sources; major data analysis packages; statistics and chemometrics software; and artificial intelligence. (JN)

  9. Near-tip dual-length scale mechanics of mode-I cracking in laminate brittle matrix composites

    NASA Technical Reports Server (NTRS)

    Ballarini, R.; Islam, S.; Charalambides, P. G.

    1992-01-01

    This paper presents the preliminary results of an on-going study of the near-tip mechanics of mode-I cracking in brittle matrix composite laminates. A finite element model is developed within the context of two competing characteristic lengths present in the composite: the microstructural length (the thickness of the layers) and a macro-length (crack-length, uncracked ligament size, etc.). For various values of the parameters which describe the ratio of these lengths and the constituent properties, the stresses ahead of a crack perpendicular to the laminates are compared with those predicted by assuming the composite is homogeneous orthotropic. The results can be used to determine the conditions for which homogenization can provide a sufficiently accurate description of the stresses in the vicinity of the crack-tip.

  10. Problem-Solving Software

    NASA Technical Reports Server (NTRS)

    1992-01-01

    CBR Express software solves problems by adapting sorted solutions to new problems specified by a user. It is applicable to a wide range of situations. The technology was originally developed by Inference Corporation for Johnson Space Center's Advanced Software Development Workstation. The project focused on the reuse of software designs, and Inference used CBR as part of the ACCESS prototype software. The commercial CBR Express is used as a "help desk" for customer support, enabling reuse of existing information when necessary. It has been adopted by several companies, among them American Airlines, which uses it to solve reservation system software problems.

  11. Geothermal Frontier: Penetrate a boundary between hydrothermal convection and heat conduction zones to create 'Beyond Brittle Geothermal Reservoir'

    NASA Astrophysics Data System (ADS)

    Tsuchiya, N.; Asanuma, H.; Sakaguchi, K.; Okamoto, A.; Hirano, N.; Watanabe, N.; Kizaki, A.

    2013-12-01

    EGS has been highlightened as a most promising method of geothermal development recently because of applicability to sites which have been considered to be unsuitable for geothermal development. Meanwhile, some critical problems have been experimentally identified, such as low recovery of injected water, difficulties to establish universal design/development methodology, and occurrence of large induced seismicity. Future geothermal target is supercritical and superheated geothermal fluids in and around ductile rock bodies under high temperatures. Ductile regime which is estimated beyond brittle zone is target region for future geothermal development due to high enthalpy fluids and relatively weak water-rock interaction. It is very difficult to determine exact depth of Brittle-Ductile boundary due to strong dependence of temperature (geotherm) and strain rate, however, ductile zone is considered to be developed above 400C and below 3 km in geothermal fields in Tohoku District. Hydrothermal experiments associated with additional advanced technology will be conducting to understand ';Beyond brittle World' and to develop deeper and hotter geothermal reservoir. We propose a new concept of the engineered geothermal development where reservoirs are created in ductile basement, expecting the following advantages: (a)simpler design and control the reservoir, (b)nearly full recovery of injected water, (c)sustainable production, (d)cost reduction by development of relatively shallower ductile zone in compression tectonic zones, (e)large quantity of energy extraction from widely distributed ductile zones, (f)establishment of universal and conceptual design/development methodology, and (g) suppression of felt earthquakes from/around the reservoirs. In ductile regime, Mesh-like fracture cloud has great potential for heat extraction between injection and production wells in spite of single and simple mega-fracture. Based on field observation and high performance hydrothermal

  12. Software Formal Inspections Standard

    NASA Technical Reports Server (NTRS)

    1993-01-01

    This Software Formal Inspections Standard (hereinafter referred to as Standard) is applicable to NASA software. This Standard defines the requirements that shall be fulfilled by the software formal inspections process whenever this process is specified for NASA software. The objective of this Standard is to define the requirements for a process that inspects software products to detect and eliminate defects as early as possible in the software life cycle. The process also provides for the collection and analysis of inspection data to improve the inspection process as well as the quality of the software.

  13. Overcoming Barriers to Engaging in College Academics

    ERIC Educational Resources Information Center

    Hensley, Lauren; Shaulskiy, Stephanie; Zircher, Andrew; Sanders, Megan

    2015-01-01

    Underprepared college students face transition issues that prevent full academic engagement. The written responses of 176 students in a learning-strategies course were used to develop a grounded model of overcoming barriers to academic engagement. Findings revealed contexts in which academic engagement involved high costs (i.e., effort, trade-off,…

  14. A Quantitative Study of Global Software Development Teams, Requirements, and Software Projects

    ERIC Educational Resources Information Center

    Parker, Linda L.

    2016-01-01

    The study explored the relationship between global software development teams, effective software requirements, and stakeholders' perception of successful software development projects within the field of information technology management. It examined the critical relationship between Global Software Development (GSD) teams creating effective…

  15. Ultrasonic Apparatus for Pulverizing Brittle Material

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Bao, Xiaoqi; Bar-Cohen, Yoseph; Dolgin, Benjamin; Chang, Zensheu

    2004-01-01

    The figure depicts an apparatus that pulverizes brittle material by means of a combination of ultrasonic and sonic vibration, hammering, and abrasion. The basic design of the apparatus could be specialized to be a portable version for use by a geologist in collecting powdered rock samples for analysis in the field or in a laboratory. Alternatively, a larger benchtop version could be designed for milling and mixing of precursor powders for such purposes as synthesis of ceramic and other polycrystalline materials or preparing powder samples for x-ray diffraction or x-ray fluorescence measurements to determine crystalline structures and compositions. Among the most attractive characteristics of this apparatus are its light weight and the ability to function without need for a large preload or a large power supply: It has been estimated that a portable version could have a mass <0.5 kg, would consume less than 1 W h of energy in milling a 1-cm3 volume of rock, and could operate at a preload <10 N. The basic design and principle of operation of this apparatus are similar to those of other apparatuses described in a series of prior NASA Tech Briefs articles, the two most relevant being Ultrasonic/ Sonic Drill/Corers With Integrated Sensors (NPO-20856), Vol. 25, No. 1 (January 2001), page 38 and Ultrasonic/ Sonic Mechanisms for Deep Drilling and Coring (NPO-30291), Vol. 27, No. 9 (September 2003), page 65. As before, vibrations are excited by means of a piezoelectric actuator, an ultrasonic horn, and a mass that is free to move axially over a limited range. As before, the ultrasonic harmonic motion of the horn drives the free-mass in a combination of ultrasonic harmonic and lower-frequency hammering motion. In this case, the free-mass is confined within a hollow cylinder that serves as a crushing chamber, and the free-mass serves as a crushing or milling tool. The hammering of the free-mass against a material sample at the lower end of the chamber grinds the sample into

  16. Software Assurance Competency Model

    DTIC Science & Technology

    2013-03-01

    COTS) software , and software as a service ( SaaS ). L2: Define and analyze risks in the acquisition of contracted software , COTS software , and SaaS ...2010a]: Application of technologies and processes to achieve a required level of confidence that software systems and services function in the...

  17. Microstructures and composition of brittle faults in claystones: Constraints on the barrier behavior

    NASA Astrophysics Data System (ADS)

    Kneuker, Tilo; Hammer, Jörg; Jahn, Steffen; Zulauf, Gernold

    2017-04-01

    Investigations of fault rocks are crucial to evaluate the barrier properties of clay rich formations used for the storage of hydrocarbons, carbon dioxide gas or for the storage of heat generating radioactive waste. Claystones are considered as a geological barrier. However, their barrier capability can be reduced if the claystones are cut by brittle faults. Our study is focusing on the microfabrics and element mobility of artificially and naturally fractured claystones using a multi-method approach. Particular attention was paid to small scale lithological heterogeneities occurring in the clayey sequence. The microfabrics were investigated using SEM and optical microscopy. Geochemical and phase analyses were carried out using XRD, XRF and ICP-MS. In addition, organic (TOC) and inorganic carbon (TIC), total sulphur (TS) as well as the cation exchange capacity (CEC) were determined. Macroscopic observations of fault zones on outcrops and drill cores indicate closely spaced planar and undulating discontinuities, including slickenside striations. The investigated fault zones are often accompanied by calcite veins and calcite enriched zones. The fault core is formed by a mm to cm thick clayey, fine grained, cohesionless fault gouge including reworked calcite fragments. Duplex-like domains are separated by discrete microshears, along which the rocks disintegrate. Calcareous fossils, common in undeformed claystones, appear in these zones fragmented and rotated. In contrast to calcite, quartz is more resistant to solution-precipitation processes. Rarely intracrystalline fracturing was observed. The calcite mineralization in veins, and solution-precipitation processes of calcite, documented by stylolites, reflect enhanced palaeo-permeability and activity of Ca2+- and CO2-rich fluids inside some of the fault zones, mainly along fault parallel shear planes. Elevated Sr and Ba concentrations are bound to the tectonic, secondary calcite veins within and outside the investigated

  18. LEGOS: Object-based software components for mission-critical systems. Final report, June 1, 1995--December 31, 1997

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    NONE

    1998-08-01

    An estimated 85% of the installed base of software is a custom application with a production quantity of one. In practice, almost 100% of military software systems are custom software. Paradoxically, the marginal costs of producing additional units are near zero. So why hasn`t the software market, a market with high design costs and low productions costs evolved like other similar custom widget industries, such as automobiles and hardware chips? The military software industry seems immune to market pressures that have motivated a multilevel supply chain structure in other widget industries: design cost recovery, improve quality through specialization, and enablemore » rapid assembly from purchased components. The primary goal of the ComponentWare Consortium (CWC) technology plan was to overcome barriers to building and deploying mission-critical information systems by using verified, reusable software components (Component Ware). The adoption of the ComponentWare infrastructure is predicated upon a critical mass of the leading platform vendors` inevitable adoption of adopting emerging, object-based, distributed computing frameworks--initially CORBA and COM/OLE. The long-range goal of this work is to build and deploy military systems from verified reusable architectures. The promise of component-based applications is to enable developers to snap together new applications by mixing and matching prefabricated software components. A key result of this effort is the concept of reusable software architectures. A second important contribution is the notion that a software architecture is something that can be captured in a formal language and reused across multiple applications. The formalization and reuse of software architectures provide major cost and schedule improvements. The Unified Modeling Language (UML) is fast becoming the industry standard for object-oriented analysis and design notation for object-based systems. However, the lack of a standard real

  19. Ideas for Creating and Overcoming Student Silences

    ERIC Educational Resources Information Center

    Woods, Donald R.; Sheardown, Heather

    2009-01-01

    The key idea is that 50 minutes of teacher talk with passive student listening is relatively ineffective in developing student learning. Teachers can create silences for productive active student learning. Students can also change from passive listeners to active talker-discussers of their learning. Ideas are given about how to overcome silences…

  20. Software for Optimizing Quality Assurance of Other Software

    NASA Technical Reports Server (NTRS)

    Feather, Martin; Cornford, Steven; Menzies, Tim

    2004-01-01

    Software assurance is the planned and systematic set of activities that ensures that software processes and products conform to requirements, standards, and procedures. Examples of such activities are the following: code inspections, unit tests, design reviews, performance analyses, construction of traceability matrices, etc. In practice, software development projects have only limited resources (e.g., schedule, budget, and availability of personnel) to cover the entire development effort, of which assurance is but a part. Projects must therefore select judiciously from among the possible assurance activities. At its heart, this can be viewed as an optimization problem; namely, to determine the allocation of limited resources (time, money, and personnel) to minimize risk or, alternatively, to minimize the resources needed to reduce risk to an acceptable level. The end result of the work reported here is a means to optimize quality-assurance processes used in developing software.

  1. Software engineering

    NASA Technical Reports Server (NTRS)

    Fridge, Ernest M., III; Hiott, Jim; Golej, Jim; Plumb, Allan

    1993-01-01

    Today's software systems generally use obsolete technology, are not integrated properly with other software systems, and are difficult and costly to maintain. The discipline of reverse engineering is becoming prominent as organizations try to move their systems up to more modern and maintainable technology in a cost effective manner. The Johnson Space Center (JSC) created a significant set of tools to develop and maintain FORTRAN and C code during development of the space shuttle. This tool set forms the basis for an integrated environment to reengineer existing code into modern software engineering structures which are then easier and less costly to maintain and which allow a fairly straightforward translation into other target languages. The environment will support these structures and practices even in areas where the language definition and compilers do not enforce good software engineering. The knowledge and data captured using the reverse engineering tools is passed to standard forward engineering tools to redesign or perform major upgrades to software systems in a much more cost effective manner than using older technologies. The latest release of the environment was in Feb. 1992.

  2. 48 CFR 227.7203-15 - Subcontractor rights in computer software or computer software documentation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... computer software or computer software documentation. 227.7203-15 Section 227.7203-15 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203-15 Subcontractor rights in computer software or computer software documentation. (a...

  3. 48 CFR 227.7203-15 - Subcontractor rights in computer software or computer software documentation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... computer software or computer software documentation. 227.7203-15 Section 227.7203-15 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203-15 Subcontractor rights in computer software or computer software documentation. (a...

  4. 48 CFR 227.7203-15 - Subcontractor rights in computer software or computer software documentation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... computer software or computer software documentation. 227.7203-15 Section 227.7203-15 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203-15 Subcontractor rights in computer software or computer software documentation. (a...

  5. 48 CFR 227.7203-15 - Subcontractor rights in computer software or computer software documentation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... computer software or computer software documentation. 227.7203-15 Section 227.7203-15 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203-15 Subcontractor rights in computer software or computer software documentation. (a...

  6. 48 CFR 227.7203-15 - Subcontractor rights in computer software or computer software documentation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... computer software or computer software documentation. 227.7203-15 Section 227.7203-15 Federal Acquisition... REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203-15 Subcontractor rights in computer software or computer software documentation. (a...

  7. Overcoming prejudice.

    PubMed

    Da Silva, J M; Correa, J; Terto, V

    1998-02-01

    People of African descent comprise a large proportion of Brazil's population. While racism exists in the country, it is commonly denied. Most Afro-Brazilians live in poor areas, with poor health care services, sanitation, schools, and transport. Since HIV is linked to poverty, Afro-Brazilians are more affected by HIV than is the overall population. Although Afro-Brazilians contribute to Brazil's culture, they do not benefit from that contribution. Recognizing this considerable social problem, Project Araye was created in 1996 to address issues of race and HIV. Building upon religious and cultural traditions, the project is staffed by Afro-Brazilians who are knowledgeable in both health issues and Afro-Brazilian culture. Project Araye supports a wide range of diverse community leaders in linking sexual health and HIV with other health concerns which affect Afro-Brazilians such as sickle-cell anemia, diabetes, and leprosy. One important challenge has been overcoming the target population's denial of HIV and encouraging Afro-Brazilians to accept that HIV also affects them. Community leaders include religious leaders, rap musicians, artists, and other people respected by various communities. Activities include visits to samba dance schools, Umbanda and Candomble temples, and street youth groups to provide HIV-related information.

  8. 48 CFR 227.7203-2 - Acquisition of noncommercial computer software and computer software documentation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... noncommercial computer software and computer software documentation. 227.7203-2 Section 227.7203-2 Federal... CONTRACTING REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203-2 Acquisition of noncommercial computer software and computer software documentation. (a...

  9. 48 CFR 227.7203-2 - Acquisition of noncommercial computer software and computer software documentation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... noncommercial computer software and computer software documentation. 227.7203-2 Section 227.7203-2 Federal... CONTRACTING REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203-2 Acquisition of noncommercial computer software and computer software documentation. (a...

  10. 48 CFR 227.7203-2 - Acquisition of noncommercial computer software and computer software documentation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... noncommercial computer software and computer software documentation. 227.7203-2 Section 227.7203-2 Federal... CONTRACTING REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203-2 Acquisition of noncommercial computer software and computer software documentation. (a...

  11. 48 CFR 227.7203-2 - Acquisition of noncommercial computer software and computer software documentation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... noncommercial computer software and computer software documentation. 227.7203-2 Section 227.7203-2 Federal... CONTRACTING REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203-2 Acquisition of noncommercial computer software and computer software documentation. (a...

  12. 48 CFR 227.7203-2 - Acquisition of noncommercial computer software and computer software documentation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... noncommercial computer software and computer software documentation. 227.7203-2 Section 227.7203-2 Federal... CONTRACTING REQUIREMENTS PATENTS, DATA, AND COPYRIGHTS Rights in Computer Software and Computer Software Documentation 227.7203-2 Acquisition of noncommercial computer software and computer software documentation. (a...

  13. Experimental Determination of the Fracture Toughness and Brittleness of the Mancos Shale, Utah.

    NASA Astrophysics Data System (ADS)

    Chandler, Mike; Meredith, Phil; Crawford, Brian

    2013-04-01

    non-linearity. This produces hysteresis during cyclic loading, allowing for the calculation of a brittleness coefficient using the residual displacement after successive loading cycles. This can then be used to define a brittleness corrected Fracture Toughness, KIcc. We report anisotropic KIcc values and a variety of supporting measurements made on the Mancos Shale in the three principle Mode-I crack orientations (Arrester, Divider and Short-Transverse) using a modified Short-Rod sample geometry. The Mancos is an Upper Cretaceous shale from western Colorado and eastern Utah with a relatively high siliclastic content for a gas target formation. The Short-Rod methodology involves the propagation of a crack through a triangular ligament in a chevron-notched cylindrical sample [3]. A very substantial anisotropy is observed in the loading curves and KIcc values for the three crack orientations, with the Divider orientation having KIcc values 25% higher than the other orientations. The measured brittleness for these Mancos shales is in the range 1.5-2.1; higher than for any other rocks we have found in the literature. This implies that the material is extremely non-linear. Increases in KIcc with increasing confining pressure are also investigated, as Shale Gas reservoirs occur at depths where confining pressure may be as high as 35MPa and temperature as high as 100oC. References [1] C.A. Green, P. Styles & B.J. Baptie, "Preese Hall Shale Gas Fracturing", Review & Recommendations for Induced Seismic Mitigation, 2012. [2] N.R. Warpinski & M.B. Smith, "Rock Mechanics and Fracture Geometry", Recent advances in Hydraulic Fracturing, SPE Monograms, Vol. 12, pp. 57-80, 1990. [3] F. Ouchterlony, "International Society for Rock Mechanics Commision on Testing Methods: Suggested Methods for Determining the Fracture Toughness of Rock", International Journal of Rock Mechanics and Mining Science & Geomechanics Abstracts, Vol. 25, 1988.

  14. Software To Go: A Catalog of Software Available for Loan.

    ERIC Educational Resources Information Center

    Kurlychek, Ken, Comp.

    This catalog lists the holdings of the Software To Go software lending library and clearinghouse for programs and agencies serving students or clients who are deaf or hard of hearing. An introduction describes the clearinghouse and its collection of software, much of it commercial and copyrighted material, for Apple, Macintosh, and IBM (MS-DOS)…

  15. Shakedown Analysis of Composite Steel-Concrete Frame Systems with Plastic and Brittle Elements Under Seismic Action

    NASA Astrophysics Data System (ADS)

    Alawdin, Piotr; Bulanov, George

    2017-06-01

    In this paper the earthquake analysis of composite steel-concrete frames is performed by finding solution of the optimization problem of shakedown analysis, which takes into account the nonlinear properties of materials. The constructions are equipped with systems bearing structures of various elastic-plastic and brittle elements absorbing energy of seismic actions. A mathematical model of this problem is presented on the base of limit analysis theory with partial redistribution of self-stressed internal forces. It is assumed that the load varies randomly within the specified limits. These limits are determined by the possible direction and magnitude of seismic loads. The illustrative example of such analysis of system is introduced. Some attention has been paid to the practical application of the proposed mathematical model.

  16. Software Metrics

    DTIC Science & Technology

    1988-12-01

    software development scene is often charac- c. SPQR Model-Jones terized by: * schedule and cost estimates that are gross-d. COPMO-Thebaut ly inaccurate, SEI...time c. SPQR Model-Jones (in seconds) is simply derived from E by dividing T. Capers Jones has developed a software cost by the Stroud number, S...estimation model called the Software Produc- T=E/S tivity, Quality, and Reliability ( SPQR ) model. The basic approach is similar to that of Boehm’s The value

  17. Software Smarts

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Under an SBIR (Small Business Innovative Research) contract with Johnson Space Center, Knowledge Based Systems Inc. (KBSI) developed an intelligent software environment for modeling and analyzing mission planning activities, simulating behavior, and, using a unique constraint propagation mechanism, updating plans with each change in mission planning activities. KBSI developed this technology into a commercial product, PROJECTLINK, a two-way bridge between PROSIm, KBSI's process modeling and simulation software and leading project management software like Microsoft Project and Primavera's SureTrak Project Manager.

  18. Software Management Metrics

    DTIC Science & Technology

    1988-05-01

    obtained from Dr. Barry Boehm’s Software 5650, Contract No. F19628-86-C-O001, Engineering Economics [1] and from T. J. ESD/MITRE Software Center Acquisition...of References 1. Boehm, Barry W., SoJtware Engineering 3. Halstead, M. H., Elements of SoJhtare Economics, Englewood Cliffs, New Science, New York...1983, pp. 639-648. 35 35 - Bibliography Beizer, B., Software System Testing and Pressman , Roger S., Software Engineering:QualtyO Assurance, New York: Van

  19. From brittle to ductile: a structure dependent ductility of diamond nanothread.

    PubMed

    Zhan, Haifei; Zhang, Gang; Tan, Vincent B C; Cheng, Yuan; Bell, John M; Zhang, Yong-Wei; Gu, Yuantong

    2016-06-07

    As a potential building block for the next generation of devices/multifunctional materials that are spreading in almost every technology sector, one-dimensional (1D) carbon nanomaterial has received intensive research interests. Recently, a new ultra-thin diamond nanothread (DNT) has joined this palette, which is a 1D structure with poly-benzene sections connected by Stone-Wales (SW) transformation defects. Using large-scale molecular dynamics simulations, we found that this sp(3) bonded DNT can transition from brittle to ductile behaviour by varying the length of the poly-benzene sections, suggesting that DNT possesses entirely different mechanical responses than other 1D carbon allotropes. Analogously, the SW defects behave like a grain boundary that interrupts the consistency of the poly-benzene sections. For a DNT with a fixed length, the yield strength fluctuates in the vicinity of a certain value and is independent of the "grain size". On the other hand, both yield strength and yield strain show a clear dependence on the total length of DNT, which is due to the fact that the failure of the DNT is dominated by the SW defects. Its highly tunable ductility together with its ultra-light density and high Young's modulus makes diamond nanothread ideal for the creation of extremely strong three-dimensional nano-architectures.

  20. Temporary brittle bone disease: relationship between clinical findings and judicial outcome

    PubMed Central

    Paterson, Colin R.; Monk, Elizabeth A.

    2011-01-01

    There is a wide differential diagnosis for the child with unexplained fractures including non-accidental injury, osteogenesis imperfecta and vitamin D deficiency rickets. Over the last 20 years we and others have described a self-limiting syndrome characterised by fractures in the first year of life. This has been given the provisional name temporary brittle bone disease. This work had proved controversial mostly because the fractures, including rib fractures and metaphyseal fractures, were those previously regarded as typical or even diagnostic of non-accidental injury. Some have asserted that the condition does not exist. Over the years 1985 to 2000 we investigated 87 such cases with fractures with a view to determining the future care of the children. In 85 of these the judiciary was involved. We examined the clinical and radiological findings in the 33 cases in which there was a judicial finding of abuse, the 24 cases in which the parents were exonerated and the 28 cases in which no formal judicial finding was made. The three groups of patients were similar in terms of demographics, age at fracturing and details of the fractures. The clinical similarities between the three groups of patients contrast with the very different results of the judicial process. PMID:22053268