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Jiang M.,Tongji University | Chen H.,Impact Lab | Tapias M.,Polytechnic University of Catalonia | Arroyo M.,Polytechnic University of Catalonia | Fang R.,Impact Lab
Computers and Geotechnics | Year: 2014

This paper presents a numerical investigation into mechanical behavior and strain localization in methane hydrate (MH) bearing sediments using the distinct element method (DEM). Based on the results of a series of laboratory tests on the bonded granules idealized by two glued aluminum rods and the available experimental data of methane hydrate samples, a pressure and temperature dependent bond contact model was proposed and implemented into a two-dimensional (2D) DEM code. This 2D DEM code was then used to numerically carry out a series of biaxial compression tests on the MH samples with different methane hydrate saturations, whose results were then compared with the experimental data obtained by Masui et al. [9]. In addition, stress, strain, void ratio and velocity fields, the distributions of bond breakage and averaged pure rotation rate (APR) as well as the evolution of strain localization were examined to investigate the relationships between micromechanical variables and macromechanical responses in the DEM MH samples. The numerical results show that: (1) the shear strength increases as methane hydrate saturation SMH increases, which is in good agreement with the experimental observation; (2) the strain localization in all the DEM MH samples develops with onset of inhomogeneity of void ratio, velocity, strain, APR, and distortion of stress fields and contact force chains; and (3) the methane hydrate saturation affects the type of strain localization, with one shear band developed in the case of 40.9% and 67.8% methane saturation samples, and two shear bands formed for 50.1% methane saturation sample. © 2014 Elsevier Ltd.


Hartung T.,Johns Hopkins University | Hartung T.,University of Konstanz | Sabbioni E.,Impact Lab | Sabbioni E.,University of Chieti Pescara
Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology | Year: 2011

Nanomaterials are acclaimed for their novel properties, for which broad new uses are being discovered with increasing frequency. It is obvious that, as the properties change, unwanted properties (toxicity) are to be expected as well. Current toxicology, however, is already overwhelmed with the challenge of addressing new chemicals, not to mention the enormous number of old chemicals never properly assessed. Limitations of traditional approaches range from animal welfare issues, which were a strong driving force for alternative approaches (the 3Rs concept) over the last two decades, to aspects of throughput and accuracy of the predicted toxicities. The latter has prompted discussion about a revolutionary change in chemical safety assessment, now known as Toxicology for the 21st Century (Tox-21c). The multitude of possible formulations of nanomaterials to be assessed for novel toxic properties makes these alternative approaches especially attractive, given the well recognized limitations of traditional animal-based approaches-limitations that might be even more pronounced for nanomaterials, which have notably altered biokinetics. © 2011 John Wiley & Sons, Inc.


Grant
Agency: European Commission | Branch: H2020 | Program: RIA | Phase: FCT-14-2014 | Award Amount: 5.00M | Year: 2015

The challenges of international police reform assistance are formidable. Conventional top-down institutional reform has proven neither effective nor sustainable. Community-based policing (COP) holds promise, however evaluations have pointed to a lack of in-depth understanding of police-community relations in police reform assistance. This project will conduct integrated social and technical research on COP in post-conflict countries in S.E. Europe, Asia, Africa and Central America. New knowledge, reflection on lessons learnt and best practices will support both national police and EU/International police reform assistance. The project will lead to a better understanding of police-community relations, and innovation in information and communication technology (ICT) for enhancing these relations in post-conflict countries undergoing serious security reform. Linking social and technological research, the project will study social, cultural, human security, legal and ethical dimensions of COP to understand how citizens and police can develop sustainable relations with the use of ICTs. We will explore how technological innovation can support COP in crime reporting and prevention. The project will explore ICT solutions to facilitate, strengthen and accelerate positive COP efforts and police-citizen interactions where trust levels are weak. Solutions will depend on the context and identified needs of end-users: communities, local police, national and international police (EU/UN), and policymakers, and may include citizen reporting, information monitoring, mobile value transfer, or improved organizational systems. The project includes a Policing Experts Network whose role is to support research planning, and dissemination and exploitation of findings, grounding the research in police practice. This will ensure findings are communicated by engaged police practitioners, and directly applied in COP education and training curricula in Europe and case countries.


Hudson L.W.,Impact Lab
ACM International Conference Proceeding Series | Year: 2013

This paper examines the use of SMS, or text messaging. It seeks to lay out the potential for use of SMS not only for beneficiary feedback mechanisms, but also for the critical work to carry out participatory planning and evaluation, and inform communities about program aims and activities. The paper will also outline the learning coming out of documented pilots, identify key challenges, and suggest some next steps for the future.


Strack O.E.,Sandia National Laboratories | Leavy R.B.,Impact Lab | Brannon R.M.,University of Utah
International Journal for Numerical Methods in Engineering | Year: 2014

Stress concentrations near grain boundaries, precipitates, and similar micro-heterogeneities nucleate instabilities leading to macroscale fracture. As it is not practical to model each flaw explicitly, their ensemble effect is modeled statistically. Accounting for this aleatory uncertainty requires smaller specimens (e.g., small finite elements) to have generally higher and more variable strengths, which is necessary for the initial failure probability of a finite domain to be unaffected by its discretization into elements. Localization itself, which might be attributed to constitutive instability, requires realistic numerical perturbations to predict bifurcations such as radial cracking in axisymmetric problems. These perturbations, stemming from microscale heterogeneity, are incorporated in simulations by imposing statistical spatial variability in the parameters of an otherwise conventional (deterministic and scale-independent) damage model. This approach is attractive for its algorithmic simplicity and straightforward calibration from standard strength tests. In addition, it results in virtually no loss of efficiency or robustness relative to deterministic models and accommodates general three-dimensional loading. Despite these advantages, some significant challenges remain and are discussed. However, it is demonstrated that including aleatory uncertainty with associated scale effects significantly improves predictiveness on large-scale computational domains, where it is impractical to resolve each crack or localization zone. © 2014 John Wiley & Sons, Ltd.


Kaveri S.V.,French Institute of Health and Medical Research | Kaveri S.V.,University Pierre and Marie Curie | Kaveri S.V.,University of Paris Descartes | Kaveri S.V.,Impact Lab
Autoimmunity Reviews | Year: 2012

Antibodies present in healthy conditions in the absence of deliberate immunization or infections are called natural antibodies. A significant proportion of natural antibody pool is believed to interact with self-antigens, and thus is called natural autoantibodies. Natural autoantibodies belong to IgG, IgM and IgA subclasses, and are encoded by V(D)J genes in germline configuration and bind to self molecules with varying affinities. In addition to serving in first line defense mechanism, natural antibodies participate in the homeostasis of the immune system. Intravenous immunoglobulin (IVIg) is a therapeutic preparation that contains substantial amount of natural antibodies exclusively of IgG subclass. In addition to its role in protection against pathogens in primary and secondary immunodeficiency patients, IVIg exerts a number of immunoregulatory functions through its interaction with innate and adaptive immune system and thereby imposing immune homeostasis. © 2012 Elsevier B.V.


Hallworth M.J.,Impact Lab
Annals of Clinical Biochemistry | Year: 2015

Hard evidence of the specific contribution made by laboratory testing to patient outcomes and the delivery of health care is not easy to obtain. An understanding of the value of laboratory medicine, how that value can be measured and the various factors that influence it is vital to ensuring that laboratory services are provided and used optimally to improve patient care. To maximise the value of laboratory medicine, work is required to improve the utilisation of existing and new biomarkers, develop standard protocols for prospective patient-centred studies of biomarker clinical effectiveness or extra-analytical process effectiveness, benchmark existing and new tests in specified clinical situations with commonly accepted effectiveness measures, and define new roles for laboratory professionals that are focussed on optimising patient outcomes by adding value throughout the total testing process. This requires effective collaboration with clinical staff and a determination to accept patient outcome and patient experience as the primary measure of laboratory performance. © 2015, © The Author(s) 2015.


Borvik T.,Impact Lab | Borvik T.,Norwegian Defence Estates Agency | Hopperstad O.S.,Impact Lab | Pedersen K.O.,Impact Lab | Pedersen K.O.,Sintef
International Journal of Impact Engineering | Year: 2010

The stress-strain behaviour of the aluminium alloy 7075 in T651 temper is characterized by tension and compression tests. The material was delivered as rolled plates of thickness 20 mm. Quasi-static tension tests are carried out in three in-plane directions to characterize the plastic anisotropy of the material, while the quasi-static compression tests are done in the through-thickness direction. Dynamic tensile tests are performed in a split Hopkinson tension bar to evaluate the strain-rate sensitivity of the material. Notched tensile tests are conducted to study the influence of stress triaxiality on the ductility of the material. Based on the material tests, a thermoelastic-thermoviscoplastic constitutive model and a ductile fracture criterion are determined for AA7075-T651. Plate impact tests using 20 mm diameter, 197 g mass hardened steel projectiles with blunt and ogival nose shapes are carried out in a compressed gas-gun to reveal the alloy's resistance to ballistic impact, and both the ballistic limit velocities and the initial versus residual velocity curves are obtained. It is found that the alloy is rather brittle during impact, and severe fragmentation and delamination of the target in the impact zone are detected. All impact tests are analysed using the explicit solver of the non-linear finite element code LS-DYNA. Simulations are run with both axisymmetric and solid elements. The failure modes are seen to be reasonably well captured in the simulations, while some deviations occur between the numerical and experimental ballistic limit velocities. The latter is ascribed to the observed fragmentation and delamination of the target which are difficult to model accurately in the finite element simulations. © 2009 Elsevier Ltd. All rights reserved.


Zhang Z.-H.,Beijing Institute of Technology | Zhang Z.-H.,Impact Lab | Liu Z.-F.,Beijing Institute of Technology | Lu J.-F.,Beijing Institute of Technology | And 4 more authors.
Scripta Materialia | Year: 2014

Typical sintering experiments were conducted to understand the spark plasma sintering (SPS) mechanisms. Based on the results of the direct visual observations and characteristic microstructure analysis, we believe that spark discharge does indeed occur during the SPS process. The high-temperature spark plasma could be generated in the microgaps due to the discharge effect. Fast and efficient sintering can be achieved under the combined action of spark discharge, Joule heating, electrical diffusion and plastic deformation effect in the SPS process. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


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