The influence of the punch land in backward can extrusion

Backward can extrusion punches are commonly made with a cylindrical punch land as also recommended by the ICFG. The contact forces on the punch land have been determined using the slab analysis method and FEM. The results show that a slight tilt of the punch land changes the contact conditions between punch land and can wall causing on the punch a net force, which will deflect the punch off centre leading to variations in wall thickness. A new punch design is proposed in which the cylindrical punch land is replaced with a circular profiled punch land. Using a circular profiled punch land, a slight tilt of the punch gives only rise to minor changes in the contact conditions between punch land and can wall and thus only rise to minor variations in the wall thickness. The backward extrusion of a high thin walled aluminium can has been carried out experimentally and the results show that cans produced with the circular profiled punch land have a significant lower variation in wall thickness than the cans produced with the punch with the cylindrical punch land.     

板金液压柔性技术及其产品设计

板金液压柔性成形具有诸多的优点,受到了汽车、航空航天等领域设计和研究者的普遍重视。文章主要介绍了板金液压柔性成形技术的内涵和外延,针对所提出的无模液压柔性成形技术和复合液压柔性成形技术,从不同的工艺方法入手,基于所研制的液压柔性成形设备,介绍了相关的飞机等领域产品特点以及设计要点,并对其中的关键工艺参数进行了描述。     

Reflections on blindsight: Neuroimaging and behavioural explorations clarify a case of reversed localisation in the blind field of a patient with hemianopia.

Blindsight refers to residual visual abilities of patients with primary visual cortex lesions. Most of this research uses single case studies, most famously patient GY. We examined a patient (DC) after surgical resection of V1 who demonstrated robust but reversed blind field target localisation, mislocalising midline blind field targets to the periphery and vice versa. This pattern was reliable across multiple sessions and was not because of extraocular light scatter. We then used functional magnetic resonance imaging to examine neural responses to blind field motion stimuli with no evidence of motion-selective activation in DC's extrastriate cortex in the damaged hemisphere, in stark contrast to GY who showed robust bilateral activation in response to blind field stimuli. This suggests that DC's blind field performance may not represent true blindsight. Follow-up testing with the target—background contrast reversed (i.e., black targets/white background), eliminated DC's reversed localisation, strongly suggesting that she was employing an unusual decision criterion based on intraocular light scatter. DC's failure to demonstrate true blindsight may be related to the age at which she acquired her lesion—much later in life than GY. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of the age structure of a cat population compared with the dog

The dogs and cats, treated at the Clinic of Internal Medicine of the University of Munich since 1983 show a tendency to a higher age of life; this is true especially in cats. The age structure of the dog population expresses a tendency to an increase of older individuals since a longer time period, whereas in the cat population this development could not be verified before the year of 1987. The results of this examination require an intensive work on the problems of increasing age, especially with those of multimorbidity, the preponderance of chronic diseases, prophylaxis, nutrition, and posture.     

Inhibitory processes in covert orienting in patients with Alzheimer's disease

Previous studies of covert orienting in Alzheimer's disease (AD) have investigated exogenous and endogenous processes separately. We aimed to investigate how the 2 modes of orienting interact to control attention in healthy older participants and patients with AD. The covert orienting of visual attention task (COVAT) with abrupt onset cues was used in all experiments. In Experiments 1 and 2, predictive information was added to cues to initiate an endogenous orienting response. Results showed that healthy older participants were able to use endogenous processes to inhibit exogenous orienting. In contrast, patients with AD were unable to inhibit exogenous orienting to cues even when targets rarely appeared there. Experiment 3 investigated inhibition of return (IOR) in patients with AD. Both healthy older controls and patients with AD showed a normal IOR, suggesting that exogenous orienting processes are relatively unaffected by the normal aging process or in patients with AD. A model of covert orienting in which exogenous and endogenous orienting processes interact to control attentional behaviors is discussed.     

Spatiotemporal distribution of facilitation and inhibition of return arising from the reflexive orienting of covert attention.

Currently, there is debate regarding both the spatial and temporal relationship between facilitation and inhibition of return (IOR) components of attention, as observed on the covert orienting of visual attention task (COVAT). These issues were addressed in a series of experiments where the spatial and temporal relationships between cue and target were manipulated. Facilitation occurred only when the stimulus onset asynchrony (SOA) was short and there was temporal overlap between cue and target. IOR occurred only when SOA was long and there was no temporal overlap between cue and target. Facilitation encompassed the cued location and all locations between the cue and fixation, whereas IOR arose for the entire cued hemifield. These findings suggest that the facilitation and IOR found on COVATs that use noninformative peripheral cues are separable and stimulus-driven processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

板液压成形及无模充液拉深技术

板液压成形技术是液压成形技术中重要的一类 ,广泛地应用于宇航、汽车等工业领域。近年来由于新材料和复杂几何形状零件的不断出现 ,更加突出此种技术的关键性。本文就板液压成形技术原理、数值模拟技术和分类进行了研究 ,探讨了此种技术将来的发展 ,介绍了基于板液压成形技术的无模充液拉深技术 ,利用实验和数值模拟技术对此技术进行了分析 ,验证了此项技术的可行性 ,并取得了较好的结果     

A novel feedback control system – Controlling the material flow in deep drawing using distributed blank-holder force

The performance of a feedback control system is often limited by the quality of the model on which it is based, and often the controller design is based on trial and error due to insufficient modeling capabilities. A framework is proposed where the controller design is based on classical state space control theory and time series. The system plant has been modeled using non-linear finite element and the gain factors for the control loop were identified by solving the optimal control problem using a non-linear least square optimization algorithm.The proposed design method has been applied on a deep drawing operation where the objective was to control material flow throughout the part using only spatial information regarding flange draw-in. The control system controls both the magnitude and distribution of the blank-holder force.The methodology proved stable and flexible with respect to controlling the dynamic behavior of the system and the numerical tests showed that it is possible to control the material flow.Preliminary experimental results show that the proposed control system can eliminate process instability when the process is subject to a systematic error.     

Hydromechanical deep-drawing of aluminum parabolic workpieces—experiments and numerical simulation

Aluminum parabolic workpieces were formed with hydromechanical deep-drawing technology. The deep-drawing process was analyzed by using the explicit finite element method with various process parameters. Defects of wrinkling and rupture are predicted for some forming conditions, and the thickness distribution results are in good agreement with the experimental results. Thinning mainly takes place during the first third of the punch travel, while wrinkling mainly takes place during the final half-stage of the punch travel. The effects of chamber pressure and blank holding force on the deformation of the workpieces are discussed. The numerical results are compared with those obtained in the experiments.     

Goal-directed selective attention and response competition monitoring: Evidence from unilateral parietal and anterior cingulate lesions.

Competing visual stimuli lead to slower responses to targets. This response competition must be resolved before correct responses are executed. Neuroimaging suggests that response competition monitoring may be subserved by an integrated neural network including the anterior cingulate cortex (ACC). In this study, 1 patient with a parietal lesion (Patient J.S.) and 1 with an ACC lesion (Patient G.M.) were presented with 2 flanker tasks; 1 required verbal identification of color targets, and the other required an opposite response to targets (e.g., see red and say "green"); a control group was also tested. For controls, perceptually incongruent flankers interfered with the ability to inhibit prepotent responses to targets. Patient J.S. performed in a similar manner, even when flankers appeared in the neglected field. Patient G.M. demonstrated reduced interference effects for contralesional flankers. Results are discussed in terms of goal-directed selective attention and response competition monitoring. (PsycINFO Database Record (c) 2010 APA, all rights reserved)