On finite element implementation and computational techniques for constitutive modeling of high temperature composites

The research work performed during the past year on finite element implementation and computational techniques pertaining to high temperature composites is outlined. In the present research, two main issues are addressed: efficient geometric modeling of composite structures and expedient numerical integration techniques dealing with constitutive rate equations. In the first issue, mixed finite elements for modeling laminated plates and shells were examined in terms of numerical accuracy, locking property and computational efficiency. Element applications include (currently available) linearly elastic analysis and future extension to material nonlinearity for damage predictions and large deformations. On the material level, various integration methods to integrate nonlinear constitutive rate equations for finite element implementation were studied. These include explicit, implicit and automatic subincrementing schemes. In all cases, examples are included to illustrate the numerical characteristics of various methods that were considered

A Modeling Investigation of Thermal and Strain Induced Recovery and Nonlinear Hardening in Potential Based Viscoplasticity

Specific forms for both the Gibb's and the complementary dissipation potentials were chosen such that a complete potential based multiaxial, isothermal, viscoplastic model was obtained. This model in general possesses three internal state variables (two scalars associated with dislocation density and one tensor associated with dislocation motion) both thermal and dynamic recovery mechanisms, and nonlinear kinematic hardening. This general model, although possessing associated flow and evolutionary laws, is shown to emulate three distinct classes of theories found in the literature, by modification of the driving threshold function F. A parametric study was performed on a specialized nondimensional multiaxial form containing only a single tensorial internal state variable (i.e., internal stress). The study was conducted with the idea of examining the impact of including a strain-induced recovery mechanism and the compliance operator, derived from the Gibb's potential, on the uniaxial and multiaxial response. One important finding was that inclusion of strain recovery provided the needed flexibility in modeling stress-strain and creep response of metals at low homologous temperatures, without adversely affecting the high temperature response. Furthermore, for nonproportional loading paths, the inclusion of the compliance operator had a significant influence on the multiaxial response, but had no influence on either uniaxial or proportional load histories

Peeled film GaAs solar cells for space power

Gallium arsenide (GaAs) peeled film solar cells were fabricated, by Organo-Metallic Vapor Phase Epitaxy (OMVPE), incorporating an aluminum arsenide (AlAs) parting layer between the device structure and the GaAs substrate. This layer was selectively removed by etching in dilute hydrofloric (HF) acid to release the epitaxial film. Test devices exhibit high series resistance due to insufficient back contact area. A new design is presented which uses a coverglass superstrate for structural support and incorporates a coplanar back contact design. Devices based on this design should have a specific power approaching 700 W/Kg

Isolated limb perfusion with actinomycin D and TNF-alpha results in improved tumour response in soft-tissue sarcoma-bearing rats but is accompanied by severe local toxicity

Previously we demonstrated that addition of Tumour Necrosis Factor-α to melphalan or doxorubicin in a so-called isolated limb perfusion results in synergistic antitumour responses of sarcomas in both animal models and patients. Yet, 20 to 30% of the treated tumours do not respond. Therefore agents that synergise with tumour necrosis factor alpha must be investigated. Actinomycin D is used in combination with melphalan in isolated limb perfusion in the treatment of patients with melanoma in-transit metastases and is well known to augment tumour cell sensitivity towards tumour necrosis factor alpha in vitro. Both agents are very toxic, which limits their systemic use. Their applicability may therefore be tested in the isolated limb perfusion setting, by which the tumours can be exposed to high concentrations in the absence of systemic exposure. To study the beneficial effect of the combination in vivo, BN-175 soft tissue sarcoma-bearing rats were perfused with various concentrations of actinomycin D and tumour necrosis factor alpha. When used alone the drugs had only little effect on the tumour. Only when actinomycin D and tumour necrosis factor alpha were combined a tumour response was achieved. However, these responses were accompanied by severe, dose limiting, local toxicity such as destruction of the muscle tissue and massive oedema. Our results show that isolated limb perfusion with actinomycin D in combination with tumour necrosis factor alpha leads to a synergistic anti-tumour response but also to idiosyncratic locoregional toxicity to the normal tissues. Actinomycin D, in combination with tumour necrosis factor alpha, should not be explored in the clinical setting because of this. The standard approach in the clinic remains isolated limb perfusion with tumour necrosis factor alpha in combination with melphalan

Dense molecular gas at 12 mm towards Galactic TeV gamma-ray sources

The High Energy Stereoscopic System has revealed many TeV (1012 eV) gamma-ray sources along the Galactic plane, and around 30 per cent of these sources remain unidentified. The morphology and dynamics of dense gas coincident and surrounding the gamma-ray emission can provide clues about the nature of the TeV emission. The H2O Southern Galactic Plane Survey (HOPS) undertaken with the Mopra radio telescope includes several dense gas tracers, such as NH3 (n,n) transitions and HC3N (3–2), star formation tracers including H2O masers and radio recombination lines that trace ionized gas. A search for dense gas, traced by NH3 (1,1) emission seen in HOPS and additional observations, towards Galactic TeV sources has been undertaken. Of the 49 Galactic TeV sources covered by 12 mm observations, NH3 (1,1) is detected towards or adjacent to 38 of them. Dense gas counterparts have been detected near several unidentified Galactic TeV sources that display morphology pointing to a hadronic origin to the TeV gamma-rays. The dense gas detected towards some TeV sources displays unusual emission characteristics, including very broad linewidths and enhanced ortho-to-para NH3 abundance ratios towards HESS J1745−303 and HESS J1801−233, which reflects previous shock activity within the gas

Challenges and solutions for enhancing agriculture value chain decision-making. A short review

© IFIP International Federation for Information Processing 2017. Increasingly challenging global and environmental requirements have resulted in agricultural systems coming under increasing pressure to enhance their resilience capabilities. This in special to respond to the abrupt changes in resource quality, quantity and availability, especially during unexpected environmental circumstances, such as uncertain weather, pests and diseases, volatile market conditions and commodity prices. Therefore, integrated solutions are necessary to support the knowledge-management, collaborative ICT solution, risk management and regulation management across agriculture stakeholders. Therefore, and based on the on-going work under the H2020 RUC-APS project research network, this book chapter is oriented to contribute to agriculture value chain decision-making field to cover the current need on gathering a common understanding and appreciation of new trends in agriculture value chain, in special the multi-disciplinary challenges. For this, a short a literature review is conducted to summarise the main findings on real application and current research trends. This within the objective to propose an integrated framework based on better use of communication ways, standardised structures, development of training and awareness, regulation based initiatives and vertical Integration

Investigation of Dense Gas Towards Relativistic Outflow Sources

We probe the interstellar medium towards the objects Circinus X-1, a low-mass X-ray binary with relativistic jets; and the highly energetic Westerlund 2 stellar cluster, which is located towards TeV gamma-ray emission and interesting arc- and jet-like features seen in Nanten 12CO data. We have mapped both regions with the Mopra radio telescope, in 7 mm and 12 mm wavebands, looking for evidence of disrupted/dense gas caused by the interaction between high energy outflows and the ISM. Towards Westerlund 2, peaks in CS(J=1-0) emission indicate high density gas towards the middle of the arc and the endpoint of the jet; and radio recombination line emission is seen overlapping the coincident HII region RCW49. Towards Circinus X-1, 12CO(J = 1-0) Nanten data reveals three molecular clouds that lie in the region of Cir X-1. Gas parameters for each cloud are presented here

Liver Resection for Hepatic Metastases from Soft Tissue Sarcoma:A Nationwide Study

Contains fulltext : 209467pub.pdf (publisher's version ) (Open Access

Implementation of prehabilitation in colorectal cancer surgery:qualitative research on how to strengthen facilitators and overcome barriers

Purpose Prehabilitation is increasingly offered to patients with colorectal cancer (CRC) undergoing surgery as it could prevent complications and facilitate recovery. However, implementation of such a complex multidisciplinary intervention is challenging. This study aims to explore perspectives of professionals involved in prehabilitation to gain understanding of barriers or facilitators to its implementation and to identify strategies to successful operationalization of prehabilitation. Methods In this qualitative study, semi-structured interviews were performed with healthcare professionals involved in prehabilitation for patients with CRC. Prehabilitation was defined as a preoperative program with the aim of improving physical fitness and nutritional status. Parallel with data collection, open coding was applied to the transcribed interviews. The Ottawa Model of Research Use (OMRU) framework, a comprehensive interdisciplinary model guide to promote implementation of research findings into healthcare practice, was used to categorize obtained codes and structure the barriers and facilitators into relevant themes for change. Results Thirteen interviews were conducted. Important barriers were the conflicting scientific evidence on (cost-)effectiveness of prehabilitation, the current inability to offer a personalized prehabilitation program, the complex logistic organization of the program, and the unawareness of (the importance of) a prehabilitation program among healthcare professionals and patients. Relevant facilitators were availability of program coordinators, availability of physician leadership, and involving skeptical colleagues in the implementation process from the start. Conclusions Important barriers to prehabilitation implementation are mainly related to the intervention being complex, relatively unknown and only evaluated in a research setting. Therefore, physicians' leadership is needed to transform care towards more integration of personalized prehabilitation programs. Implications for cancer survivors By strengthening prehabilitation programs and evidence of their efficacy using these recommendations, it should be possible to enhance both the pre- and postoperative quality of life for colorectal cancer patients during survivorship