Injection molding shrinkage of PP: Experimental progress

Injection molding shrinkage deals with dimensional differences between a molded part and the cavity. By adding an array of orthogonal marks into a mold, local shrinkage values may be obtained by comparing dimensions of this array with dimensions of the array replicated on the surface of the parts. A profilograph is employed to obtain dimensional measurements, in the parallel to flow direction and in the cross flow direction. A sensitivity analysis is conducted to determine aspects of shrinkage evaluation causing uncertainty on the results. Prominent sources of uncertainty found are mark straightness defect and part warpage. Uncertainty on shrinkage is evaluated to 0.00025 mm/mm for a distance between the marks of 6.350 mm. Shrinkages have been evaluated locally for molded plates. Different distribution forms were observed for parallel to flow and cross flow shrinkage. Important anisotropy is also observed. The effects of holding pressure and injection velocity on shrinkages have been evaluated using a 2³ factorial design of experiment for three locations on the plates. Finally, shrinkages for three mold geometries have been compared: constant thickness plate, variable in thickness symmetrical plate, and variable in thickness asymmetrical plate. Variable in thickness plates showed the importance of solidification dynamics on final shrinkages. POLYM. ENG. SCI., 46:1275–1283, 2006. © 2006 Society of Plastics Engineers     

Three‐dimensional localization for the MagneBike inspection robot

The MagneBike inspection robot is a climbing robot equipped with magnetic wheels. The robot is designed to drive on three‐dimensional (3D) complexly shaped pipe structures; therefore it is necessary to provide 3D visualization tools for the user, who remotely controls the robot out of sight. The localization system is required to provide a 3D map of the unknown environment and the 3D location of the robot in the environment's map. The localization strategy proposed in this paper consists of combining 3D odometry with 3D scan registration. The odometry model is based on wheel encoders and a three‐axis accelerometer. Odometry enables the tracking of the robot trajectory between consecutive 3D scans and is used as a prior for the scan matching algorithm. The 3D scan registration facilitates the construction of a 3D map of the environment and refines the robot position computed with odometry. This paper describes in detail the implementation of the localization concept. It presents the lightweight, small‐sized 3D range finder that has been developed for the MagneBike. It also proposes an innovative 3D odometry model that estimates the local surface curvature to compensate for the absence of angular velocity inputs. The different tools are characterized in detail based on laboratory and field experiments. They show that the localization concepts reliably track the robot moving in the specific application environment. We also describe various techniques to optimize the 3D scanning process, which is time consuming, and to compensate for the identified limitations. These techniques are useful inputs for the future automatization of the robot's control and optimization of its localization process. © 2010 Wiley Periodicals, Inc.     

Adaptive continuous‐space informative path planning for online environmental monitoring

Autonomous mobile robots are increasingly employed to take measurements for environmental monitoring, but planning informative, measurement‐rich paths through large three‐dimensional environments is still challenging. Designing such paths, known as the informative path planning (IPP) problem, has been shown to be NP‐hard. Existing algorithms focus on providing guarantees on suboptimal solutions, but do not scale well to large problems. In this paper, we introduce a novel IPP algorithm that uses an evolutionary strategy to optimize a parameterized path in continuous space, which is subject to various constraints regarding path budgets and motion capabilities of an autonomous mobile robot. Moreover, we introduce a replanning scheme to adapt the planned paths according to the measurements taken in situ during data collection. When compared to two state‐of‐the‐art solutions, our method provides competitive results at significantly lower computation times and memory requirements. The proposed replanning scheme enables to build models with up to 25% lower uncertainty within an initially unknown area of interest. Besides presenting theoretical results, we tailored the proposed algorithms for data collection using an autonomous surface vessel for an ecological study, during which the method was validated through three field deployments on Lake Zurich, Switzerland. Spatiotemporal variations are shown over a period of three months and in an area of 350 m × 350 m × 13 m. Whereas our theoretical solution can be applied to multiple applications, our field results specifically highlight the effectiveness of our planner for monitoring toxic microorganisms in a pre‐alpine lake, and for identifying hot‐spots within their distribution.     

Vascular Architecture Generates Fine Scale Variation in Systemic Induction of Proteinase Inhibitors in Tomato

Systemic induction following damage has been found in many plant species. Despite this widespread appreciation for the importance of induction, few studies have characterized the spatial variability of induction. We used tomato, Lycopersicon esculentum, to examine how damage to a single leaf affected the spatial distribution of systemic induction of proteinase inhibition in leaves above the damaged leaf. We crushed each leaflet of the second true leaf with forceps and measured the spatial distribution of proteinase inhibition in leaves 3, 4, and 5 at 8, 16, 24, 48, 72, and 120 hr. Constitutive levels of proteinase inhibitor activity were quantified in undamaged plants. We hypothesized that, due to vascular control of signal movement, systemic induction would show both among and within leaf variability. Following damage to leaf 2, induction was most pronounced in leaf 5 and minimal in leaf 3. In general, proteinase inhibitor activity was greatest at 24 hr and then declined. As predicted by vascular architecture, the near side of leaves in adjacent orthostichies showed higher induction than the far side of leaves. There was no increase in proteinase inhibitor activity in the undamaged neighboring plants. Overall our results demonstrate that systemic induction of proteinase inhibitors is partially controlled by vascular architecture and that future studies on systemic induction should examine the vascular architecture of the plants being studied. We argue that this spatial variation may influence the performance of herbivores sensitive to induced chemical changes.     

évaluation du développement de l'enfant au cours de la première année: l'utilisation de regroupements d'items du Bayley.

Compared the discriminative powers of (1) the mental and motor indexes of the Bayley Scales of Infant Development (BSID) (N. Bayley, 1969), (2) the 5-cluster regrouping of the BSID by R. Kohen-Raz (1967), and (3) the 7-cluster regrouping of the BSID by L. J. Yarrow et al (1975). Ss were 29 3.5-mo-old, 53 6-mo-old, and 57 9-mo-old Haitian, Canadian, and Vietnamese infants. Ss' performances on the BSID were analyzed with the mental and motor scales of the BSID, the 5-cluster regrouping, and the 7-cluster regrouping. The 3 systems were compared with regard to their ability to detect age, gender, and cultural differences. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Variations du rythme cardiaque d'enfants soumis à des taches d'observation et de contr?le de stimulations complexes.

Three experiments were conducted to determine the cardiac responses of 30 preschool children requested to be attentive to stimulations and/or to try to control their occurrences by a simple or more complex motor behavior. In Exp I, Ss were instructed to pay attention to the movements, lights, and sounds originating from a harlequin puppet (observation condition). In Exp II, Ss were told that they could initiate the harlequin stimulations with a simple motor response (easy control condition). In Exp III, Ss had to perform a more complex response to initiate the stimulation (difficult control condition). In the observation condition, the first stimulations elicited a decelerative heart rate response. In the easy control condition, both groups displayed an equivalent number of keypresses. Ss in the difficult control condition, while making as many keypress responses, obtained fewer stimulations than Ss of the easy contingent group. Their tonic and phasic cardiac responses during the demonstration–observation phase were similar. During the control trials, the first and last stimulations within trials were followed by phasic decelerative responses in this group. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

étude comparative de nourrissons prématurés et nés à terme et des modes de stimulations qu'ils expérimentent au cours des six premiers mois.

Compared preterm and fullterm infants' temperament and development and to evaluate the physical and social stimulations they experience at 2, 4 and 6 months (correcting for prematurity). Fifty-six mother–infant dyads, including 28 premature and 28 fullterm infants, participated in the study. The groups did not differ on temperament and developmental measures, neither on physical environment (density, toys, accessories). However, significant differences were found regarding social stimulation. Mothers of preterm infants had less optimal sensibility-contingency scores and used more distal stimulation at 2 months than mothers of fullterm infants. During the first 6 months, premature infants spent more time in activities involving the immediate family, whereas fullterm infants went more frequently on outings. At home, fullterm infants interacted more with people from their social network. These stimulations could eventually have an impact on infant development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in sensitivity to nicotine: implications for genetic research on nicotine dependence

Recent evidence suggests that cigarette smoking has a heritability index around 53%. While related research on underlying mechanisms also supports the idea that genetic factors contribute to nicotine dependence--as well as to cofactors such as substance use and mood disorders--the nature of the behavioral traits and biological capacity for reinforcement that constitutes vulnerability to nicotine dependence is not well understood. The present review explores the problem of why some people become highly nicotine dependent, others develop a pattern of occasional use, and still others avoid the drug entirely despite extensive exposure and widespread experimentation with tobacco in the population. Recent research--both infrahuman and human--suggests that vulnerability to nicotine dependence is related to high initial sensitivity to nicotine and that the development of tolerance is more rapid and self-administration more extensive in such individuals. Relevant findings from neuroscience and biobehavioral research are reviewed in order to identify variables and methodologies that might improve the reliability and validity of behavioral and molecular genetic studies on cigarette smoking. The integration of research in these areas may lead to new insights in the understanding of nicotine dependence as well as to improved techniques for prevention and treatment.