Highly-accurate 5-axis flank CNC machining with conical tools

A new method for $5$-axis flank computer numerically controlled (CNC) machining using a predefined set of tappered ball-end-mill tools (aka conical) cutters is proposed. The space of lines that admit tangential motion of an associated truncated cone along a general, doubly curved, free-form surface is explored. These lines serve as discrete positions of conical axes in 3D space. Spline surface fitting is used to generate a ruled surface that represents a single continuous sweep of a rigid conical milling tool. An optimization based approach is then applied to globally minimize the error between the design surface and the conical envelope. Our computer simulation are validated with physical experiments on two benchmark industrial datasets, reducing significantly the execution times while preserving or even reducing the milling error when compared to the state-of-the-art industrial software

Tool path pattern and feed direction selection in robotic milling for increased chatter-free material removal rate

Robotic milling becomes increasingly relevant to large-scale part manufacturing industries thanks to its cost-effective and portable manufacturing concept compared to large-scale CNC machine tools. Integration of milling processes with industrial robots is proposed to be well aligned with the aims and objective of the recent fourth industrial revolution. However, the industrial robots introduce position-dependent and asymmetrical dynamic flexibility, which may reflect to the tool tip dynamics under several conditions. Under such circumstances, the stability limits become dependent on the machining location and the feed direction. In this respect, selection of machining tool path patterns is crucial for increased chatter-free material removal rates (MRR). This paper proposes an approach to evaluate and select tool path patterns, offered by the existing CAM packages, for increased chatter-free MRR. The machining area is divided into number of machining locations. The optimal feed direction is decided based on the absolute stability at each region considering the asymmetrical and position-dependent tool tip dynamics. Then, the alternative tool path patterns are evaluated and the corresponding optimum feed direction is decided for increased chatter-free material removal. The application of the proposed approach is demonstrated through simulations and representative experiments

Generating tool-path with smooth posture change for five-axis sculptured surface machining based on cutter's accessibility map

10.1007/s00170-010-2849-2International Journal of Advanced Manufacturing Technology535-8699-709IJAT

The autonomic nervous system

The autonomic nervous system innervates the visceral organs, the glands and the blood vessels. It regulates the internal environment, and it is largely responsible for maintaining normal bodily functions such as respiration, blood pressure and micturition. The peripheral autonomic nervous system consists of two parts, a thoracolumbar or sympathetic and a craniosacral or parasympathetic division, which usually have antagonistic effects (Sect. 12.2). The sympathetic system is organized to mobilize the body for activities, especially in stressful situations (Cannon’s fight or flight), whereas the parasympathetic system in particular stimulates the peristaltic and secretory activities of the gastrointestinal tract (also known as rest and digest response). The peripheral part of the autonomic nervous system includes neurons in the viscera and peripheral ganglia, which are innervated by the lateral horn of the spinal cord and certain brain stem nuclei. Neuronal plexuses in the gastrointestinal tract form the enteric nervous system, which is often viewed as the third component of the autonomic nervous system. Tonically active bulbar centres control vital functions such as blood pressure and respiration. The autonomic centres in the brain stem and spinal cord are reciprocally connected with the central autonomic network (Sect. 12.3), which includes the hypothalamus and several other forebrain (in particular the extended amygdala and the insula) and brain stem structures such as the periaqueductal grey and the parabrachial nucleus. This network is essential for the integration of autonomic, endocrine and somatomotor functions. The peripheral and central autonomic pathways may be affected by many diseases, which cause derangement of autonomic functions as exemplified in several Clinical Cases on disorders of the neural control of blood pressure, breathing and micturition. The English terms of the Terminologia Neuroanatomica are used throughout

Brain imaging of neurovascular dysfunction in Alzheimer’s disease

Neurovascular dysfunction, including blood–brain barrier (BBB) breakdown and cerebral blood flow (CBF) dysregulation and reduction, are increasingly recognized to contribute to Alzheimer’s disease (AD). The spatial and temporal relationships between different pathophysiological events during preclinical stages of AD, including cerebrovascular dysfunction and pathology, amyloid and tau pathology, and brain structural and functional changes remain, however, still unclear. Recent advances in neuroimaging techniques, i.e., magnetic resonance imaging (MRI) and positron emission tomography (PET), offer new possibilities to understand how the human brain works in health and disease. This includes methods to detect subtle regional changes in the cerebrovascular system integrity. Here, we focus on the neurovascular imaging techniques to evaluate regional BBB permeability (dynamic contrast-enhanced MRI), regional CBF changes (arterial spin labeling- and functional-MRI), vascular pathology (structural MRI), and cerebral metabolism (PET) in the living human brain, and examine how they can inform about neurovascular dysfunction and vascular pathophysiology in dementia and AD. Altogether, these neuroimaging approaches will continue to elucidate the spatio-temporal progression of vascular and neurodegenerative processes in dementia and AD and how they relate to each other

The multifaceted role of PIP2 in leukocyte biology

Phosphatidylinositol 4,5-bisphosphate (PIP2) represents about 1 % of plasma membrane phospholipids and behaves as a pleiotropic regulator of a striking number of fundamental cellular processes. In recent years, an increasing body of literature has highlighted an essential role of PIP2 in multiple aspects of leukocyte biology. In this emerging picture, PIP2 is envisaged as a signalling intermediate itself and as a membrane-bound regulator and a scaffold of proteins with specific PIP2 binding domains. Indeed PIP2 plays a key role in several functions. These include directional migration in neutrophils, integrin-dependent adhesion in T lymphocytes, phagocytosis in macrophages, lysosomes secretion and trafficking at immune synapse in cytolytic effectors and secretory cells, calcium signals and gene transcription in B lymphocytes, natural killer cells and mast cells. The coordination of these different aspects relies on the spatio-temporal organisation of distinct PIP2 pools, generated by the main PIP2 generating enzyme, phosphatidylinositol 4-phosphate 5-kinase (PIP5K). Three different isoforms of PIP5K, named α, β and γ, and different splice variants have been described in leukocyte populations. The isoform-specific coupling of specific isoforms of PIP5K to different families of activating receptors, including integrins, Fc receptors, toll-like receptors and chemokine receptors, is starting to be reported. Furthermore, PIP2 is turned over by multiple metabolising enzymes including phospholipase C (PLC) γ and phosphatidylinositol 3-kinase (PI3K) which, along with Rho family small G proteins, is widely involved in strategic functions within the immune system. The interplay between PIP2, lipid-modifying enzymes and small G protein-regulated signals is also discussed