An algorithm to simulate the one-dimensional superelastic cyclic behavior of NiTi strings, for civil engineering applications

An algorithm to model the one-dimensional cyclic behavior of NiTi strings is addressed. The NiTi alloy belongs to the shape memory alloy class of materials, therefore it presents both shape memory effect, for thermally-induced cycling, and superelasticity, for stress-induced cycles. The superelastic property has been the basis of some devices designed to mitigate the earthquake hazard level in structures. Throughout this paper the implementation of a one-dimensional cyclic behavior algorithm to model the NiTi constitutive relation is presented, supported by the thermomechanical formulation developed by Lagoudas and co-workers. The model was set up in MatLab environment and it accounts for isothermal superelastic behavior, incorporating minor hysteretic transformation loops. The definition of the transformation hardening function allowed for a better adjustment of the numerical model weighted against experimental results. Especial emphasis was given to the process of calibration of the model, regarding the definition of material parameters. The validation process consisted of the comparison between the results achieved with this algorithm and experimental tests performed at the Pacific Earthquake Engineering Research Center at the University of California at Berkeley. Quasi-static tensile tests and shake table tests of a small-scale steel structure with NiTi cross-bracing systems were used as reference. The model was able to simulate the experimental performance. This formulation can be implemented in more robust finite element analysis software, in order to perform studies in more elaborate structures.     

Developing a prebiotic yogurt: Rheological,physico-chemical and microbiological aspects and adequacy of survival analysis methodology

The addition of prebiotics such as oligofructose to yogurt can result in a product with consumer benefits, since they stimulate growth of benefic bacteria present in the intestine and also provide a low calorie product, since one can add less sugar to the formulation due to their sweetening power. This work aimed to evaluate the effect of increasing concentrations of oligofructose addition on physicochemical, rheological and microbiological characteristics of non-flavored yogurt. Furthermore, it was investigated the reaction of consumers with the use of the survival analysis methodology. The addition of oligofructose showed no influence on the pH, proteolysis or the viability of Streptococcus thermophilus or Lactobacillus bulgaricus during 28 days of refrigerated storage (p > 0.05). According to rheological measurements the yogurt supplemented with oligofructose was characterized as a weak gel, showing thixotropic and pseudoplastic behavior. Survival analysis was used to investigate consumer responses with respect to different levels of supplementation of plain yogurt with oligofructose (0%, 2%, 4%, 6% and 8% wt. v⁻¹). Using the survival analysis and considering a rejection by 25% of the consumers, the level of oligofructose that can be added to the yogurt was shown to be 2.58% wt. v⁻¹.     

The T2 chart with mixed samples to control bivariate autocorrelated processes

In this paper, we propose the use of the T² chart with the mixed sampling strategy (MS) to monitor the mean vector of bivariate processes with observations that fit to a first-order vector autoregressive model. With the MS, rational subgroups of size n are taken from the process and the selected units are regrouped to form the mixed samples. The units of the mixed samples are units selected from the last two rational subgroups. The aim of the proposed sampling strategy is to reduce the negative effect of the autocorrelation on the performance of the T² chart. When the two variables are autocorrelated, the MS always enhances the T² chart performance, however, the mixed samples are not recommended for bivariate processes with only one autocorrelated variable which is rarely affected by the assignable cause.     

Gastric cytoprotective activity of 2-cyclopenten-1-one and related compounds

The cytoprotective activity of the isolated functional groups of several sesquiterpene lactones is reported. Among them the highest activity is shown by alpha-methylen-gamma-butyrolactone and 2-cyclopenten-1-one. The activity shown by those Michael acceptors with a beta carbon hindered by an alkyl substituent was always lower or almost null. A three-way mechanism of action is proposed: a) reduced glutathione synthesis, b) prostaglandin synthesis and c) mucosal glycoprotein synthesis.     

Terrain Avoidance Nonlinear Model Predictive Control for Autonomous Rotorcraft

This paper describes a terrain avoidance control methodology for autonomous rotorcraft applied to low altitude flight. A simple nonlinear model predictive control (NMPC) formulation is used to adequately address the terrain avoidance problem, which involves stabilizing a nonlinear and highly coupled dynamic model of a helicopter, while avoiding collisions with the terrain as well as preventing input and state saturations. The physical input saturations are made intrinsic to the model, such that the control is always admissible and the MPC design is simplified. A comparison of several optimization approaches is provided, where the performance of the traditional gradient method with fixed step is compared with the quasi-Newton method and a line search algorithm. The simulation results show that the adopted strategy achieves good performance even when the desired path is on collision course with the terrain.     

The skipping strategy to reduce the effect of the autocorrelation on the <Emphasis Type="Italic">T</Emphasis><Superscript>2</Superscript> chart’s performance

In this article, we consider the T ² control chart for bivariate samples of size n with observations that are not only cross-correlated but also autocorrelated. The cross-covariance matrix of the sample mean vectors were derived with the assumption that the observations are described by a first-order vector autoregressive model—VAR (1). To counteract the undesired effect of autocorrelation, we build up the samples taking one item from the production line and skipping one, two, or more before selecting the next one. The skipping strategy always improves the chart’s performance, except when only one variable is affected by the assignable cause, and the observations of this variable are not autocorrelated. If only one item is skipped, the average run length (ARL) reduces in more than 30 %, on average. If two items are skipped, this number increases to 40 %.     

Mobile text-entry and visual demands: reusing and optimizing current solutions

Mobile devices are increasingly used for text-entry in contexts where visual attention is fragmented and graphical information is inadequate, yet the current solutions to typing on virtual keyboards make it a visually demanding task. This work looks at assistive technologies and interface attributes as tools to ease the task. Two within-subject experiments were performed with 23 and 17 participants, respectively. The first experiment aimed to understand how walking affected text-entry performance and additionally to assess how effective assistive technologies can be in mobile contexts. In the second experiment, adaptive keyboards featuring character prediction and pre-attentive attributes to ease visual demands of text-entry interfaces were developed and evaluated. It has been found that both text-input speed and overall quality are affected in mobile situations. Contrary to the expectations, assistive technologies proved ineffective with visual feedback. The second experiment showed that pre-attentive attributes do not affect users’ performance in task-entry tasks, even though a 3.3–4.3 % decrease in error rates was measured. It was found that users reduce walking speed to compensate for challenges placed by mobile text-entry. Caution should be exercised when transferring assistive technologies to mobile contexts, since they need adaptations to address mobile users’ needs. Also, while pre-attentive attributes seemingly have no effect on experienced QWERTY typists’ performance, they showed promise for both novice users and typists in attention-demanding contexts.     

In situ cultured preantral follicles is a useful model to evaluate the effect of anticancer drugs on caprine folliculogenesis

Despite the increase in the incidence of cancer, the number of women who survive cancer treatment is growing. However, one of the principal results of chemotherapy is premature ovarian failure (POF). The aim of this study was to use the in situ culture preantral follicles as an in vitro model to evaluate the toxicity of two anticancer drugs, doxorubicin (DXR) and paclitaxel (PTX), on the integrity and development of ovarian follicles. Fragments of the ovarian cortex of goats were cultured in vitro for 1 or 7 days in α‐MEM⁺ supplemented with different concentrations of DXR (0.003, 0.03, or 0.3 µg/mL) and PTX (0.001, 0.01, or 0.1 µg/mL). Analyses were performed before and after culture to evaluate tissue integrity by classical histology, apoptosis by TUNEL assay, DNA laddering kit and the detection of activated caspase 3, and DNA damage by the immune detection of phosphorylated histone H2A.x (H2AXph139). Both DXR and PTX reduced the number of morphologically normal primordial and developing follicles. Positive staining for TUNEL and active caspase 3 was detected in all the samples (P < 0.05). Therefore, we propose the in situ culture of caprine preantral follicles as a useful experimental model for assessing the toxic effects of the chemotherapeutic agents on ovarian folliculogenesis. Microsc. Res. Tech. 79:773–781, 2016. © 2016 Wiley Periodicals, Inc.