Simulation of a two-slope pyramid made by SPIF using an adaptive remeshing method with solid-shell finite element

Single point incremental forming (SPIF) is an emerging application in sheet metal prototyping and small batch production, which enables dieless production of sheet metal parts. This research area has grown in the last years, both experimentally and numerically. However, numerical investigations into SPIF process need further improvement to predict the formed shape correctly and faster than current approaches. The current work aims the use of an adaptive remeshing technique, originally developed for shell and later extended to 3D “brick” elements, leading to a Reduced Enhanced Solid-Shell formulation. The CPU time reduction is a demanded request to perform the numerical simulations. A two-slope pyramid shape is used to carry out the numerical simulation and modelling. Its geometric difficulty on the numerical shape prediction and the through thickness stress behaviour are the main analysis targets in the present work. This work confirmed a significant CPU time reduction and an acceptable shape prediction accuracy using an adaptive remeshing method combined with the selected solid-shell element. The stress distribution in thickness direction revealed the occurrence of bending/unbending plus stretching and plastic deformation in regions far from the local deformation in the tool vicinity.     

Microstructural features of dynamic recrystallization in alloy 625 friction surfacing coatings

In friction surfacing (FS), material is deposited onto a substrate in the plasticized state, using frictional heat and shear stresses. The coating material remains in the solid state and undergoes severe plastic deformation (SPD) at high process temperatures (≈0.8 T_melt), followed by high cooling rates in the range of 30?K/s. Dynamic recrystallization and the thermal cycle determine the resulting microstructure. In this study, Ni-based alloy 625 was deposited onto 42CrMo4 substrate, suitable, for instance, for repair welding of corrosion protection layers. Alloy 625 is known to undergo discontinuous dynamic recrystallization under SPD, and the resulting grain size depends on the strain rate. The coating microstructure was studied by microscopy and electron backscatter diffraction (EBSD). The coatings exhibit a fully recrystallized microstructure with equiaxed grains (0.5–12?µm) and a low degree of grain average misorientation. Flow lines caused by a localized decrease in grain size and linear alignment of grain boundaries are visible. Grain nucleation and growth were found to be strongly affected by localized shear and nonuniform material flow, resulting in varying amounts of residual strain, twins and low-angle grain boundaries in different regions within a single coating layer’s cross section.

FS can be used to study dynamic recrystallization at high temperatures, strains and strain rates, while at the same time materials with a recrystallization grain size sensitive to the strain rate can be used to study the material flow during the process.     

PROJECT TEAM SELECTION USING FUZZY OPTIMIZATION APPROACH

With their high potential, high motivation, great problem-solving ability and flexibility, project teams are important work structures for the business life. The success of these teams is highly dependent upon the people involved in the project team. This makes the project team selection an important factor for project success. The project team selection can be defined as selecting the right team members, which will together perform a particular project/task within a given deadline. In this article, an analytical model for the project team selection problem is proposed by considering several human and nonhuman factors. Because of the imprecise nature of the problem, fuzzy concepts like triangular fuzzy numbers and linguistic variables are used. The proposed model is a fuzzy multiple objective optimization model with fuzzy objectives and crisp constraints. The skill suitability of each team candidate is reflected to the model by suitability values. These values are obtained by using the fuzzy ratings method. The suitability values of the candidates and the size of the each project team are modeled as fuzzy objectives. The proposed algorithm takes into account the time and the budget limitations of each project and interpersonal relations between the team candidates. These issues are modeled as hard-crisp constraints. The proposed model uses fuzzy objectives and crisp constraints to select the most suitable team members to form the best possible team for a given project. A simulated annealing algorithm is developed to solve the proposed fuzzy optimization model. Software based on C + + computer programming language is also developed to experiment on the proposed model in forming project teams.     

Use of geographical information system and remote sensing techniques for planning culture‐based fisheries in non‐perennial reservoirs of Sri Lanka

The presence of a wide areal extent of small‐sized village reservoirs offers a considerable potential for the development of culture‐based fisheries (CBFs) in Sri Lanka. To this end, this study uses geographical information systems (GISs) and remote sensing (RS) techniques to determine the morphometric and biological characteristics most useful for classifying non‐perennial reservoirs for CBF development and for assessing the influence of catchment land‐use patterns on potential CBF yields. The reservoir shorelines at full water supply level were mapped with a Global Positioning System to determine shoreline length and reservoir areal extent. The ratio of shoreline length to reservoir extent, which was reported to be a powerful predictor variable of CBF yields, could be reliably quantified using RS techniques. The areal extent of reservoirs, quantified with RS techniques (RS extent), was used to estimate the ratio of forest cover plus scrubland cover to RS extent and was found to be significantly related to the CBF yield (R² = 0.400; P < 0.05). The results of this study indicated that morphometric characteristics and catchment land‐use patterns, which might be viewed as indices of biological productivity, can be quantified using RS and GIS techniques.     

Residual entanglement with negativity for pure four-qubit quantum states

In this work we study the entanglement of pure four-qubit quantum states. The analysis is realized, firstly, through the comparison between two different entanglement measures: the Groverian entanglement measure and the residual entanglement calculated with negativities. After, we use the last to measure the entanglement of several four-qubit states and the variation of the entanglement when the four-qubit state is processed by a two-qubit gate.     

Annealing and crystallization kinetics of poly(lactic acid) pieces obtained by additive manufacturing

In this study, we investigated the influence of isothermal treatment of poly(lactic acid) (PLA) 3D printed samples at different crystallization temperatures. In this case, we analyzed the effect of each crystallization temperature on spherulites formation in printed PLA, affecting the final mechanical properties of pieces. For such, the thermomechanical properties, morphological structure, and crystallization kinetics were analyzed before and after thermal treatment. The 3D printed samples were heat treated at 80°C, 90°C, 100°C, 110°C, and 119°C. With annealing, we observed an improvement in the mechanical PLA properties; however, the exothermic crystallization peak was different for the samples. Pieces before annealing were found to have a low crystallinity index (Ic) of 2%–7%, and the pieces after annealing presented a considerable Ic (27%–34%). Annealing temperatures of 100°C, 110°C, and 119°C produced the fastest crystallization kinetics, while annealing temperatures of 80°C and 90°C resulted in the lowest crystallization kinetics for complete crystallization. After annealing, improvement in the flexural strength (34%–47%) and Young's modulus (26%–51%) for all annealed pieces occurred. The appropriate condition was observed at 100°C, which was the onset temperature of crystallization, owing to the combination of the shorter time of crystallization with the increased mechanical properties.     

Effects of river impoundment on body condition and reproductive performance of the Australian native fish, Macquarie perch (Macquaria australasica)

This study attempts to evaluate the influence of the impounding of Lake Dartmouth (36°35′S, 147°31′E; on Mitta Mitta River in Victoria) on the Macquarie perch (Macquaria australasica, Cuvier 1830), an Australian percichthyid fish of riverine origin. In this study the yearly changes in body condition and spawning performance of adult populations in the impoundment were evaluated in relation to lake features, in particular the water level. Body condition of the spawning population of Macquarie perch in Lake Dartmouth, in year n was related to mean annual storage volume of the lake, with a time lag of one year during the post‐filling phase of the lake (1991–1997). The influence of condition on the reproductive performance of captive female Macquarie perch from Lake Dartmouth using artificial propagation techniques was evaluated over the period 1991–1997. The mean relative fecundity (mrf), expressed as the number of eggs produced per kilogram of body weight of hypophysed fish, showed a decrease over the period, but the mean weight of hypophysed fish did not decrease over the same time period. The mrf (Y_mrf) was positively correlated to yearly mean relative condition factor (X_Rc), the relationship being: The spawning variables, mean percentage fertilization (Y_fn) (1991–1997) and mean larval production (Y_ln) (1992–1996) in each year (n) were also related to the mean relative condition factor (X_Rc) of female fish that spawned after hypophysation in each year. It is suggested that the declining success in the artificial propagation of this species is caused by a declining maternal condition of female fish collected from the impoundment, resulting from poor nutrition.     

An evaluation of the marmoset Callithrix jacchus (sagüi) as an experimental model for the dyslipoproteinemia of human Schistosomiasis mansoni

BACKGROUND: There have been only a few brain computed tomography imaging studies, with mostly negative findings, in subjects with borderline personality disorder (BPD). This is the first MRI study which evaluated the structural abnormalities of the brain in subjects with the sole diagnosis of BPD. METHODS: Twenty-five subjects with BPD were compared with age-, gender-matched healthy comparison subjects (n=25) on volumes of the frontal lobes, the temporal lobes, the lateral ventricles, and the cerebral hemispheres in brain magnetic resonance imaging. RESULTS: Subjects with BPD had a significantly smaller frontal lobe compared to comparison subjects (multivariate regression analysis, t=2.225, df=46, P=0.031). There were no significant differences in volumes of the temporal lobes, the lateral ventricles, and the cerebral hemispheres between subjects with and without BPD. LIMITATIONS: Strict inclusion and exclusion criteria employed in the present study may make it difficult to generalize our findings. The gray matter and white matter of the brain were not measured separately. Differences in head tilt during image acquisition were not corrected. CONCLUSIONS: The current study reports a smaller frontal lobe volume on brain MRI in subjects with BPD compared with healthy comparison subjects. This finding may serve as a potentially useful biological variable that may allow for subtyping BPD.     

Bond Behavior of Near-Surface Mounted CFRP Laminate Strips under Monotonic and Cyclic Loading

Near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) laminate strips are used to increase the load-carrying capacity of concrete structures. This is done by inserting the CFRP strips into slits made in the concrete cover of the elements to be strengthened and gluing the strips to the concrete with an epoxy adhesive. In several cases the NSM technique has substantial advantages when compared with externally bonded laminates. To assess the bond behavior between the CFRP and concrete under monotonic and cyclic loading, an experimental program was carried out based on a series of pullout-bending tests. The influence of the bond length and loading history on the bond behavior was investigated. In this work the details of the tests are described and the obtained results discussed. Using the experimental data and an analytical-numerical strategy, a local bond stress-slip relationship was determined. A finite-element analysis was performed to evaluate the influence of the adhesive on the global response observed in the pullout-bending tests.