A dislocation-density-based 3D crystal plasticity model for pure aluminum

A dislocation-density-based crystal plasticity finite-element model (CPFEM) is developed in which different dislocation densities evolve. Based upon the kinematics of crystal deformation and dislocation interaction laws, dislocation generation and annihilation are modeled. The CPFEM model is calibrated for pure aluminum using experimental stress–strain curves of pure aluminum single crystal from the literature. Crystallographic texture predictions in plane-strain compression of aluminum are validated against experimental observations in the literature. The framework is implemented in ABAQUS with user interface UMAT subroutine.     

Spark ignition of turbulent recirculating non-premixed gas and spray flames: A model for predicting ignition probability

A model that synthesizes previous knowledge from experiments and simulations on spark ignition of gas and liquid-fuelled non-premixed recirculating flames has been developed. Attention is focused on the flame expansion process and the overall filling of the combustor volume with flame. The model is meant to provide a quick assessment of the ignition behaviour of a combustor. It uses information from the flow patterns before ignition and calculates possible trajectories that a flame emanating from a spark may experience. The calculation of these trajectories includes flame extinction to capture the experimentally-observed flame quenching, mixture fraction fluctuations to capture the non-premixed nature of the flame, convection by the mean and the random turbulent flow to capture the probabilistic nature of the flame evolution, and uses recent results on the laminar burning velocity in sprays. The model is applied to gas and spray flames and the calculated ignition probability distributions and the timescale of complete ignition agree reasonably well with experiment. The results of the model provide insights into spark ignition processes in complicated flow patterns.     

Aerosol nucleation and growth in a turbulent jet using the Stochastic Fields method

The Stochastic Fields transported PDF method for turbulent reacting flows has been used to model the nucleation and growth of dibutyl phthalate particles in a hot, turbulent jet in a colder background for which experimental data is available. The aerosol population is modelled using an assumed log-normal size distribution. It has been found that neglecting the effect of turbulent fluctuations leads to the peak particle concentration being predicted too close to the jet and the concentration downstream underpredicted. However, this effect was small compared to that of adjusting modelled surface tension. Only by adjusting this was it possible to reproduce correctly the downstream evolution of particle number found in experiment. Particle mass mean diameter was significantly underpredicted at the centre of the jet, which may be due to the inability of log-normal size distribution to capture the distribution in detail. Taking account of turbulent fluctuations leads to increased mean particle size at the edge of the plume. The extent of this increase is strongly dependent on the choice of micromixing timescale.     

Browning development in white wines: dependence on compositional parameters and impact on antioxidant characteristics

Browning is a serious problem in relation to white wine quality and mostly affects the sensory attributes, whereas its impact on the dietary value of wines has never been investigated. Browning, however, is well known to be associated with polyphenol oxidation, and therefore it may be accompanied by changes in the antioxidant capacity. On the basis of this consideration, experimental white wines vinified and stored under identical conditions were subjected to accelerated browning, and efforts were made to distinguish compositional parameters that might be related to the extent of browning development. Further, the consequences of browning on the reducing power and antiradical activity were assessed. It was shown that none of the parameters examined (titratable acidity, pH, total SO₂, total polyphenols and total flavanols) play an important role in browning onset, but SO₂ appeared to exert a statistically significant influence (r²=0.6394, P<0.05) on the percentage change in the antiradical activity. Evidence also suggested that browning development might be prominently associated with decreases in both antiradical activity (r²=0.7891, P<0.01) and reducing power (r²=0.6925, P<0.05).     

Anti-tumor necrosis factor alpha therapy suppresses the induction of experimental autoimmune uveoretinitis in mice by inhibiting antigen priming

PURPOSE: Experimental autoimmune uveoretinitis (EAU) serves as a model for several immune-mediated diseases that affect the eye in humans. Previous studies indicated that tumor necrosis factor alpha (TNF-alpha) has an important proinflammatory role in EAU and possibly in human uveitis. In this study, the authors investigated the effect of anti-TNF-alpha therapy on EAU in mice. METHODS: Experimental autoimmune uveoretinitis was induced in B10.A mice by immunization with interphotoreceptor retinoid-binding protein (IRBP). The mice were treated with 100 or 300 microliters rabbit antiserum or polyclonal antibodies to human TNF-alpha. The treatment spanned either the afferent or the efferent stage of EAU (days -1, 1, 3, 5, 7, or days 8, 10, 12, 14, 16, respectively). Control animals were injected with preimmune rabbit serum at the corresponding times or were not treated. Three weeks after immunization, EAU was assessed by clinical evaluation and by histopathology. Immunologic responses were assessed by delayed-type hypersensitivity (DTH), lymphocyte proliferation to IRBP, and relative abundance of IRBP-primed splenocytes. RESULTS: The treatment with rabbit anti-TNF-alpha serum significantly ameliorated disease when given during the afferent stage but had no effect when given during the efferent stage of EAU. The effect on DTH, lymphocyte proliferation, and abundance of antigen-reactive cells roughly paralleled the effect on disease. CONCLUSIONS: Neutralization of systemic TNF ameliorates EAU. The effectiveness of afferent treatment in comparison to the treatment during the efferent stage, together with the reduced proliferation and the reduced abundance of IRBP-responsive cells, suggest that interference with afferent-acting processes such as antigen priming is important to achieve protection from EAU by anti-TNF treatment.     

Ignition of turbulent non-premixed flames

The initiation of turbulent non-premixed combustion of gaseous fuels through autoignition and through spark ignition is reviewed, motivated by the increasing relevance of these phenomena for new combustion technologies. The fundamentals of the associated turbulent-chemistry interactions are emphasized. Background information from corresponding laminar flow problems, relevant turbulent combustion modelling approaches, and the ignition of turbulent sprays are included. For both autoignition and spark ignition, examination of the reaction zones in mixture fraction space is revealing. We review experimental and numerical data on the stochastic nature of the emergence of autoignition kernels and of the creation of kernels and subsequent flame establishment following spark ignition, aiming to reveal the particular facet of the turbulence causing the stochasticity. In contrast to fully-fledged turbulent combustion where the effects of turbulence on the reaction are reasonably well-established, at least qualitatively, here the turbulence can cause trends that are not straightforward.     

Machine Learning Utilization for Bed Load Transport in Gravel-Bed Rivers

Three data-driven techniques, namely artificial neural networks, adaptive-network-based fuzzy inference system, and symbolic regression based on genetic programming, are employed for the prediction of bed load transport rates in gravel-bed steep mountainous streams and rivers in Idaho (U.S.A.), and the potential of several input variables is investigated. The input combinations that were tested are based, mainly, on unit stream power, stream power, and shear stress, and exhibited similarly good performance, with respect to the machine learning technique used, accentuating the importance of the regression model. The derived models are robust, generalize very well in unseen data, and generated results superior to those of some of the widely used bed load formulae, without the need to set a threshold for the initiation of motion, and consequently avoid predicting erroneous zero transport rates.     

Numerical simulation of interface crack in thin films

The de-adhesion of a thin film from a rigid substrate is studied. It is assumed, that a periodic array of micro-cracks exists along the film/substrate interface. During formation, the film expands, while being constrained by the substrate. This phenomenon leads to development of compressive stresses. Then buckling may occur and cause crack growth either along the interface or in the film towards the free surface. A finite element model has been developed, which simulates film buckling and subsequent interfacial crack growth, based on film/substrate adhesive constitutive relations. These relations have been motivated by atomistic calculations on bimaterial failure. The model does not require any facture criterion. Interfacial work of separation has a significant effect on damage growth ahead of the crack tip, along the interface. Also, a critical remote compressive stress exists, at which damage progresses without further loading of the film. The relation between the critical compressive stress for extensive damage and the interfacial work of separation can be used in combination with experiments for the quantitative characterization of the film/substrate interface. This revised version was published online in July 2006 with corrections to the Cover Date.     

Open Mobile Alliance (OMA) security layer: Architecture, implementation and performance evaluation of the integrity unit

Security has become a very critical issue in the provision of mobile services. The Open Mobile Alliance (OMA) has specified a powerful security layer, the WTLS. In this paper, a VLSI architecture for the implementation of the WTLS integrity unit is proposed. The proposed architecture is reconfigurable in the sense that operates in three different modes: as Keyed-Hash Authentication Code (HMAC), as SHA-1 and MD5 hash functions, according to WTLS specifications. This multi-mode operation is achieved due to the reconfigurable applied design technique in the proposed architecture, which keeps the allocated area resources at a minimized level. The proposed architecture achieves high speed performance, due to the pipeline designed architecture. Especially, SHA-1 operation achieved throughput is equal to 1,7 Gbps, while MD5 operation mode bit rate is equal to 2,1 Gbps. The proposed architecture has been integrated by using VHDL and has been synthesized placed and routed in an FPGA device. Comparisons with related hash functions implementations have been done in terms of throughput, operating frequency, allocated area and Area-Delay product. The achieved performance of the SHA-1 operation mode is better at about 14–42 times compared with the other conventional works. In addition, MD5 performance is superior to the other works at about 6–18 times, in all of the cases. The proposed Integrity Unit is a very trustful and powerful solution for the WTLS layer. In addition, it can be integrated in security systems which are used for the implementation networks for wireless protocols, with special needs of integrity in data transmission. Nicolas Sklavos, Ph.D.: He is a Ph.D. Researcher with the Electrical and Computer Engineering Department, University of Patras, Greece. His interests include computer security, new encryption algorithms design, wireless communications and reconfigurable computing. He received an award for his Ph.D. thesis on “VLSI Designs of Wireless Communications Security Systems” from IFIP VLSI SOC 2003. He is a referee of International Journals and Conferences. He is a member of the IEEE, the Technical Chamber of Greece and the Greek Electrical Engineering Society. He has authored or co-authored up to 50 scientific articles in the areas of his research. Paris Kitsos, Ph.D.: He is currently pursuing his Ph.D. in the Department of Electrical and computer Engineering, University of Patras, Greece. He received the B.S. in Physics from the University of Patras in 1999. His research interests include VLSI design, hardware implementations of cryptography algorithms, security protocols for wireless communication systems and Galois field arithmetic implementations. He has published many technical papers in the areas of his research. Epaminondas Alexopoulos: He is a student of the Department of Electrical and Computer Engineering, University of Patras, Greece. His research includes hardware implementations, mobile computing and security. He has published papers in the areas of his research. Odysseas Koufopavlou, Ph.D.: He received the Diploma of Electrical Engineering in 1983 and the Ph.D. degree in Electrical Engineering in 1990, both from University of Patras, Greece. From 1990 to 1994 he was at the IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA. He is currently an Associate Professor at the Department of Electrical and Computer Engineering, University of Patras. His research interests include VLSI, low power design, VLSI crypto systems and high performance communication subsystems architecture and implementation. He has published more than 100 technical papers and received patents and inventions in these areas.     

Resection of metastatic renal cell carcinoma

PURPOSE: Resection of solitary metastases from renal cell carcinoma (RCC) is associated with a 5-year survival rate of 35% to 50%. Selection criteria are not well defined. PATIENTS AND METHODS: We retrospectively analyzed our experience with 278 patients with recurrent RCC from 1980 to 1993. RESULTS: One hundred forty-one of 278 patients underwent a curative metastectomy for their first recurrence (44% 5-year overall survival [OS] rate), 70 patients underwent noncurative surgery (14% 5-year OS rate), and 67 patients were treated nonsurgically (11% 5-year OS rate). Favorable features for survival were a disease-free interval (DFI) greater than 12 months versus 12 months or less (55% v 9% 5-year OS rate; P < .0001), solitary versus multiple sites of metastases (54% v 29% 5-year OS rate; P < .001), and age younger than 60 years (49% v 35% 5-year OS rate; P < .05). Among 94 patients with a solitary metastasis, lung (n = 50; 54% 5-year OS rate) was more favorable than brain (n = 11; 18% 5-year OS rate; P < .05). Survival rates after curative resection of second and third metastases were not different compared with initial metastectomy (46% and 44%, respectively, v 43% 5-year OS rates; P = nonsignificant). Favorable predictors of survival by multivariate analysis included a single site of first recurrence, curative resection of first metastasis, a long DFI, a solitary site of first metastasis, and a metachronous presentation with recurrence. CONCLUSION: Selected patients with recurrent RCC who can undergo a curative resection of their disease have a good opportunity for long-term survival, particularly those with a single site of recurrence and/or a long DFI.