Topological and dimensional synthesis of planar linkages for multiple kinematic tasks

This paper presents the combined use of two systematic methods for the synthesis of planar linkage mechanisms satisfying multiple kinematic tasks. First, a Graph Theory-based method is used to exhaustively enumerate the topological alternatives for a given problem. Then each feasible alternative is automatically dimensioned using the Precision Position Method; this computation includes space and design constraints. The existing methods to synthesize multiple tasks solve, in sequence, a decomposition of the problem into single kinematic tasks. The task decomposition and the topology selection for each task are usually performed by hand. This process leads to topologies with a repeated pattern and could lead to ignoring potentially desirable topologies. This paper analyzes a design strategy for the simultaneous solution of multiple kinematic tasks. This strategy has two advantages: (i) it eliminates the need for task decomposition, and (ii) it allows the exhaustive exploration of all non-isomorphic topologies up to a defined number of links. An example of simultaneous synthesis for a double rigid-body guidance task with application to a flap-tab mechanism is shown to illustrate the methodology.     

Microbial and enzymatic stability of fruit juice-milk beverages treated by high intensity pulsed electric fields or heat during refrigerated storage

The influence of high intensity pulsed electric fields (HIPEF) treatment (35 kV/cm, bipolar 4 μs square wave pulses at 200 Hz) on the inactivation of Listeria innocua in fruit juice–whole (FJ–WM) or skim milk (FJ–SM) beverages was assessed. As well, the effects of HIPEF or conventional thermal (90 °C 60 s) processing in terms of microbial and enzymatic stability and changes on physicochemical parameters of the beverages during refrigerated storage were also studied. HIPEF and thermal processing ensured the microbial stability of the beverages during 56 days at 4 °C without significant changes on pH, acidity and soluble solid content values. Thermal processing was more effective than HIPEF in reducing Pectin Methyl Esterase (PME) activity in FJ–SM and FJ–WM beverages since its activity was reduced by 70.66% and 87.33%, respectively. With regards to Polygalacturonase (PG), HIPEF treatment reduced by 26.92% and 20.93% the enzyme activity in the FJ–WM and FJ–SM beverages, respectively, whereas thermal treatment did not inactivate PG in both beverages. HIPEF or thermally-treated samples showed higher viscosity than the untreated ones, being this increment more pronounced in the beverages with whole milk. Therefore, HIPEF processing may be a feasible technology in order to obtain shelf stable and fresh-like fruit juice-milk beverages.     

Applicability assessment of a real-time PCR assay for the specific detection of bovine,ovine and caprine material in feedstuffs

A TaqMan real-time polymerase chain reaction (PCR) method was developed for specific detection of bovine, ovine and caprine processed animal protein (PAP) in industrial feedstuffs. The method uses species-specific primers and probes targeting short mitochondrial D-loop sequences, and a positive amplification control based on 18S rRNA gene. The applicability of the real-time PCR protocol was assessed through analysis of 126 industrial feed samples that were manufactured to reproduce rendering processes of commercial feeds destined for farmed animals. The assay successfully classified samples as positive or negative according to the ruminant composition, enabling qualitative detection of banned material in feeds at levels as low as 0.1%. Although the method provides quantitative potential, results suggest that the real quantitative capability of the assay is limited by the existing variability in terms of composition and processing treatments of the feeds, which affect the amount and quality of amplifiable DNA.     

Small-angle scattering study of colloidal particles in heavy crude oils

The structural and dispersion characteristics of samples of heavy crude oils and fractions isolated from them have been studied. A method of in situ analysis of the aggregation of asphaltenes directly in crude oils on the basis of small-angle X-ray scattering is proposed. It has been shown that the maximum size of scattering particles in all crude oil samples is limited to the value on the order of 8.0 nm; the average diameter is ∼2.0 nm. It has been found that the fraction with sizes of 0.8–2.5 nm is mostly composed of resins. Asphaltenes in crude oils form larger aggregated particles with a size up to 8 nm. A comparative study of model dilute solutions of asphaltenes in toluene (0.23 wt %) has shown that the major part of asphaltenes in the liquid (∼94%) is in the form of individual molecules with a size of 0.4–1.2 nm, and only an insignificant remaining part (∼6%) occurs in the form of large aggregates.     

Microstructure of NiCoAlFeCuCr multi-component systems synthesized by mechanical alloying

The present study uses the mechanical alloying method to produce series of binary to senary alloys based on Ni, Co, Al, Fe, Cu, Cr. Milling times are 0, 10, 20 and 30 h and experiments are performed in a high energy ball mill. The results of this investigation show that an FCC solid solution is formed in all the studied systems, but a different phase formation response is presented in each system. A mixture of FCC and BCC solid solutions in quaternary to senary systems, is formed for short milling times. Apparently, the dissolution rate of Fe and Cr into the FCC solid solution, is low. Moreover, it is observed that additions of these elements promote the formation of BCC solid solution, which is stable at temperatures up to ?1273 K. Finally, it is observed that the heat treated products present a mixture of FCC and BCC solid solutions with lattice parameters close to those found in the milled products.     

Stress–strain relationship in axial compression for concrete using recycled saturated coarse aggregate

In this work the stress–strain curve of the recycled concretes was determined by replacing different percentages of the natural coarse aggregate with recycled coarse aggregate (20%, 50% and 100%). The results made it possible to establish the differences between the stress–strain relationship of a conventional concrete and this relationship for a recycled concrete depending on the percentage of replacement. In this way, it was found that the longitudinal strain of the recycled concretes increases with the percentage of recycled coarse aggregate used.Finally, using the experimental results, an analytical expression of the stress–strain curve accounting for the percentage of replacement was developed. The verification of the proposed model equation was done by comparing it to the experimental data. The results show that the proposed model equation satisfactorily describes the effect of the recycled aggregate on the stress–strain curve.     

Assessment of properties of recycled concrete by means of a highly fractioned factorial design of experiment

The study presented in this paper has been carried out using a highly fractional factorial experimental design. This design allows the analysis of a greater number of factors and levels with a reduced number of mixes. In the state of art of recycled concrete the studies have been carried out varying the level of one factor while the rest remained fixed. However an excessive number of factors or levels are not considered. This highly simplified test program was designed in order to make the number of tests viable whilst guaranteeing the reliability of the conclusions. The concrete has been produced by substituting the natural coarse aggregates for recycled aggregates from construction and demolition waste, which is mainly composed of concrete. In this research some factors that have not been analyzed in previous studies, such as the granular structure of the concrete or the replacement criteria, have been studied. The properties of recycled concrete analyzed were: density, absorption, compressive strength, elastic modulus and penetration of water under pressure. The concrete was made with dry recycled aggregate. The percentage of replacement of the recycled aggregate did not affect the compressive strength since the water/cement rate remained constant. However the elastic modulus is affected by the percentage of replacement when it exceeds 50%.     

Regulation of memory accuracy with multiple answers: The plurality option.

We report two experiments that investigated the regulation of memory accuracy with a new regulatory mechanism: the plurality option. This mechanism is closely related to the grain-size option but involves control over the number of alternatives contained in an answer rather than the quantitative boundaries of a single answer. Participants were presented with a slideshow depicting a robbery (Experiment 1) or a murder (Experiment 2), and their memory was tested with five-alternative multiple-choice questions. For each question, participants were asked to generate two answers: a single answer consisting of one alternative and a plural answer consisting of the single answer and two other alternatives. Each answer was rated for confidence (Experiment 1) or for the likelihood of being correct (Experiment 2), and one of the answers was selected for reporting. Results showed that participants used the plurality option to regulate accuracy, selecting single answers when their accuracy and confidence were high, but opting for plural answers when they were low. Although accuracy was higher for selected plural than for selected single answers, the opposite pattern was evident for confidence or likelihood ratings. This dissociation between confidence and accuracy for selected answers was the result of marked overconfidence in single answers coupled with underconfidence in plural answers. We hypothesize that these results can be attributed to overly dichotomous metacognitive beliefs about personal knowledge states that cause subjective confidence to be extreme. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The influence of general identity disturbance on reports of lifetime substance use disorders and related outcomes among sexual minority adults with a history of substance use.

Previous research has shown that sexual minority (i.e., nonheterosexual) individuals report increased problematic substance use involvement, compared with their sexual majority counterparts. We hypothesize that feelings of an unstable sense of self (i.e., identity disturbance) may potentially drive problematic substance use. The purpose of the current study is to examine identity disturbance among sexual minorities as a potential explanatory mechanism of increased sexual minority lifetime rates of substance dependence. Measures of identity disturbance and three indicators of sexual orientation from lifetime female (n = 16,629) and male (n = 13,553) alcohol/illicit drug users in Wave 2 of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) were examined. Findings generally showed that the increased prevalence of alcohol dependence, illicit drug dependence, and combined alcohol/illicit drug dependence as well as a younger age of alcohol use initiation among sexual minority women was associated with elevated levels of identity disturbance. The results were consistent with a mediational role for identity disturbance in explaining the association between sexual minority status and substance dependence and were generally replicated among male sexual minority respondents. The current research suggests that identity disturbance, a predictor of substance use, may contribute to heightened risk for substance dependence among certain subgroups of sexual minority individuals. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A formulation to model the nonlinear viscoelastic properties of the vascular tissue

Nearly all soft tissues, including the vascular tissue, present a certain degree of viscoelastic material response, which becomes apparent performing multiple relaxation tests over a wide range of strain levels and plotting the resulting stress relaxation curves, nonlinear viscoelasticity of the tissue. Changes in relaxation rate at each strain may occur at multiple strain levels. A constitutive formulation considering the particular features of the vascular tissue, such as anisotropy, together with these nonlinear viscoelastic phenomena is here presented and used to fit stress?Cstretch curves from experimental relaxation tests. This constitutive model was used to fit several data set of in vitro experimental stress relaxation tests performed on ovine and porcine aorta. The good fitting of the experimental data shows the capability of the model to reproduce the viscoelastic response of the vascular tissue.