This paper presents a slew maneuver control design of three-axis rotational flexible spacecraft. The focus of the work is to investigate the nonlinear effect of the three axis maneuver for a flexible spacecraft when a...
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This paper presents a slew maneuver control design of three-axis rotational flexible spacecraft. The focus of the work is to investigate the nonlinear effect of the three axis maneuver for a flexible spacecraft when a vibration suppression technique for linear systems such as input shaping is used in the control design. A simple method of slewing three-axis rotational spacecraft using input shaping is proposed and the proposed technique is implemented on an experimental three-axis spacecraft simulator.
Combined adaptive control law, using both variable and identification approaches for an autopilot of the unmanned aerial vehicle (UAV) homing guidance system is proposed. The combined adaptive controller design is bas...
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Combined adaptive control law, using both variable and identification approaches for an autopilot of the unmanned aerial vehicle (UAV) homing guidance system is proposed. The combined adaptive controller design is based upon shunting method and passification with Feedback Kalman-Yakubovich Lemma. The adaptation algorithm provides prescribed attitude motion dynamics for different flight conditions. Simulation results verify efficiency of the combined adaptive controller in the case of significant uncertainty of the UAV parameters and time dependence of the guidance loop.
In the daily practice of science for policy, as experienced by governmental agencies which inform the policy and the public on the state and outlook of the environment, there is a pressing need for guidance in assessi...
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In the daily practice of science for policy, as experienced by governmental agencies which inform the policy and the public on the state and outlook of the environment, there is a pressing need for guidance in assessing and communicating uncertainties. This need extends beyond the quantitative assessment of uncertainties in model results, and focuses on the entire process of environmental assessment, running from problem framing towards reporting the results of the study. Using the Netherlands Environmental Assessment Agency (RIVM/MNP) as a case, the development, structure and content of such a guidance system is highlighted. Conditions for a successful implementation of the guidance system are discussed, and some prospects for future work are outlined.
Numerical guidance methods for decision making support of aviation meteorological forecasters a-re presented. The methods have been developed to enhance the usefulness of numerical weather prediction (NWP) model data ...
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Numerical guidance methods for decision making support of aviation meteorological forecasters a-re presented. The methods have been developed to enhance the usefulness of numerical weather prediction (NWP) model data and local and upstream observations in the production of terminal aerodrome forecasts (TAFs) and trend-type forecasts (TRENDs) for airports. In this paper two newly developed methods are described and it is shown how they are used to derive numerical guidance products for aviation. The first is a combination of statistical and physical postprocessing of NWP model data and in situ observations. This method is used to derive forecasts for all aviation-related meteorological parameters at the airport. The second is a high-resolution wind transformation method. a technique used to derive local wind at airports from grid-box-averaged NWP model winds. For operational use of the numerical guidance products encoding software is provided for automatic production of an alphanumeric TA-F and TREND code. A graphical user interface,with an integrated code editor enables the forecaster to modify the suggested automatic codes. For aviation, the most important parameters in the numerical guidance are visibility and cloud-base height. Both have been subjected to a,statistical verification analysis. together with their automatically produced codes. The results in terms of skill score are compared to the skill of the forecasters' TAT and TREND code. The statistical measures suggest that the guidance has the best skill at lead times of +4 h and more. For the short term, mainly trend-type forecasts, the persistence forecast based on recent observations is difficult to beat. Verification has also shown that the wind transformation method. which has been applied to generate 10-m winds at Amsterdam Airport Schiphol, reduces the mean error in the (grid box averaged.) NWP model wind significantly. Among the potential benefits of these numerical guidance methods is increasing for
The development of a hypertext-based diagnosis system requires, on one hand, adapted tools for a task oriented navigation across the documents, and on the other hand, context sensitive browsing capability of the knowl...
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The development of a hypertext-based diagnosis system requires, on one hand, adapted tools for a task oriented navigation across the documents, and on the other hand, context sensitive browsing capability of the knowledge base. This paper presents a system that possesses both properties. It is based on a formal model ontology for representing a diagnostic domain, a computational scheme to implement and use the ontology, and a human-machine interface to provide users with an efficient access to objects, methods, and relations described in the ontology. We use an example based on the diagnosis of vibrations of rotating machines throughout the paper to illustrate the approach. The example has been built and implemented according to the norm (AFNOR 1998), which defines the protocol and the evaluation procedure of vibration from signals measured and recorded on the rotating machines.
Clinical Guidelines are primarily developed in the affluent West. This Viewpoint article discusses whether these guidelines are really useful and relevant to resource-poor, developing countries, and whether attempts t...
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Clinical Guidelines are primarily developed in the affluent West. This Viewpoint article discusses whether these guidelines are really useful and relevant to resource-poor, developing countries, and whether attempts to adhere to such guidelines obscure more fundamental issues such as the provision of basic health care. The authors argue that if guidelines are adapted to local resources and needs, and employ a 'cascade' approach they can work.
Repulsive guidance molecules (RGMs) are recently identified proteins implicated in neuronal differentiation, migration, and apoptosis. However, in non-neural tissues a specific biological function of RGM is still unkn...
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Repulsive guidance molecules (RGMs) are recently identified proteins implicated in neuronal differentiation, migration, and apoptosis. However, in non-neural tissues a specific biological function of RGM is still unknown. In this study, we describe the expression patterns of the RGM members (a, b, and c) during embryonic and postnatal development of the small and large murine intestine. We demonstrated by RT-PCR, in situ hybridization, Western blot, and immunocytochemistry that subtypes RGMa and RGMb but not RGMc were strongly expressed in enteric ganglia cells of the fetal and adult gut. In contrast to the enteric nervous system, RGMa and RGMb expression in the intestinal epithelium started during postnatal gut development. Interestingly, both subtypes were predominantly expressed in the proliferative crypt compartment of the gut epithelium and in paneth cells of small intestine. The development-dependent expression in enteric ganglia and intestinal epithelial cells suggests that RGM may be involved in cell migration, differentiation, and apoptosis with similar cellular mechanisms as described in the central nervous system. (c) 2005 Wiley-Liss, Inc.
The early axon scaffolding in the embryonic vertebrate brain consists of a series of ventrally projecting axon tracts that grow into a single major longitudinal pathway connected across the midline by commissures. We ...
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The early axon scaffolding in the embryonic vertebrate brain consists of a series of ventrally projecting axon tracts that grow into a single major longitudinal pathway connected across the midline by commissures. We have investigated the role of Brother of CDO (BOC), an immunoglobulin (Ig) superfamily member distantly related to the Roundabout (Robo) family of axon-guidance receptors, in the development of this embryonic template of axon tracts in the zebrafish brain. A zebrafish homologue of BOC was isolated and shown to be expressed predominantly in the developing neural plate and later in the neural tube and developing brain. Zebrafish boc was initially highly localized to discrete bands in the mid- and hindbrain, but, as the major brain subdivisions emerged, it became more evenly expressed along the rostrocaudal axis, particularly in dorsal regions. The function of zebrafish boc was examined by a loss-of-function approach. Analysis of embryos injected with antisense morpholinos designed against boc revealed highly selective defects in the development of dorsoventrally projecting axon tracts. Loss of boc caused ventrally projecting axons, particularly those arising from the presumptive telencephalon, to follow aberrant trajectories. These data indicate that boc is an axon-guidance molecule playing a fundamental role in pathfinding during the early patterning of the axon scaffold in the embryonic vertebrate brain. (c) 2005 Wiley-Liss, Inc.
Axon guidance and neuronal migration are critical features of neural development, and it is believed that extracellular gradients of secreted guidance cues play important roles in pathfinding. It has been well documen...
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Axon guidance and neuronal migration are critical features of neural development, and it is believed that extracellular gradients of secreted guidance cues play important roles in pathfinding. It has been well documented that the growth cones of extending axons respond to such extracellular gradients by growing toward or away from the source of the secreted cue via asymmetrical extension of a single growth cone. However, it is unclear whether migrating neurons change direction in response to guidance molecules using the same mode of turning as extending axons. In this study, we demonstrate that migrating neurons turn away from the chemorepellent Slit through repeated rounds of process extension and retraction and do not turn through the reorientation of a single growth cone. We further show that Slit increases the rate of somal process formation and that these processes form preferentially on the side of the cell body furthest away from the Slit source. In addition, Slit causes cell turning through asymmetric process selection. Finally, we show that multiple types of migrating neurons employ this mode of cell turning in response to a variety of guidance cues. These results show that migrating neurons employ a unique type of turning when faced with secreted guidance cues that is distinct from the type employed by axons. (c) 2005 Elsevier Inc. All rights reserved.
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