83,159 research outputs found

    Fuselage structure using advanced technology fiber reinforced composites

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    A fuselage structure is described in which the skin is comprised of layers of a matrix fiber reinforced composite, with the stringers reinforced with the same composite material. The high strength to weight ratio of the composite, particularly at elevated temperatures, and its high modulus of elasticity, makes it desirable for use in airplane structures

    A Cellular, Language Directed Computer Architecture

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    If a VLSI computer architecture is to influence the field of computing in some major way, it must have attractive properties in all important aspects affecting the design, production, and the use of the resulting computers. A computer architecture that is believed to have such properties is briefly discussed

    A simple model of EMI-induced timing jitter in digital circuits, its statistical distribution and its effect on circuit performance

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    A simple model has been developed to characterize electromagnetic interference induced timing variations (jitter) in digital circuits. The model is based on measurable switching parameters of logic gates, and requires no knowledge of the internal workings of a device. It correctly predicts not only the dependence of jitter on the amplitude, modulation depth and frequency of the interfering signal, but also its statistical distribution. The model has been used to calculate the immunity level and bit error rate of a synchronous digital circuit subjected to radio frequency interference, and to compare the electromagnetic compatibility performance of fast and slow logic devices in such a circuit

    An introduction to time-resolved decoding analysis for M/EEG

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    The human brain is constantly processing and integrating information in order to make decisions and interact with the world, for tasks from recognizing a familiar face to playing a game of tennis. These complex cognitive processes require communication between large populations of neurons. The non-invasive neuroimaging methods of electroencephalography (EEG) and magnetoencephalography (MEG) provide population measures of neural activity with millisecond precision that allow us to study the temporal dynamics of cognitive processes. However, multi-sensor M/EEG data is inherently high dimensional, making it difficult to parse important signal from noise. Multivariate pattern analysis (MVPA) or "decoding" methods offer vast potential for understanding high-dimensional M/EEG neural data. MVPA can be used to distinguish between different conditions and map the time courses of various neural processes, from basic sensory processing to high-level cognitive processes. In this chapter, we discuss the practical aspects of performing decoding analyses on M/EEG data as well as the limitations of the method, and then we discuss some applications for understanding representational dynamics in the human brain

    Single wall penetration equations

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    Five single plate penetration equations are compared for accuracy and effectiveness. These five equations are two well-known equations (Fish-Summers and Schmidt-Holsapple), two equations developed by the Apollo project (Rockwell and Johnson Space Center (JSC), and one recently revised from JSC (Cour-Palais). They were derived from test results, with velocities ranging up to 8 km/s. Microsoft Excel software was used to construct a spreadsheet to calculate the diameters and masses of projectiles for various velocities, varying the material properties of both projectile and target for the five single plate penetration equations. The results were plotted on diameter versus velocity graphs for ballistic and spallation limits using Cricket Graph software, for velocities ranging from 2 to 15 km/s defined for the orbital debris. First, these equations were compared to each other, then each equation was compared with various aluminum projectile densities. Finally, these equations were compared with test results performed at JSC for the Marshall Space Flight Center. These equations predict a wide variety of projectile diameters at a given velocity. Thus, it is very difficult to choose the 'right' prediction equation. The thickness of a single plate could have a large variation by choosing a different penetration equation. Even though all five equations are empirically developed with various materials, especially for aluminum alloys, one cannot be confident in the shield design with the predictions obtained by the penetration equations without verifying by tests

    Tackling disinvestment in health care services

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    Rising levels of demand due to ageing populations and increases in long term conditions (White 2007), increased levels of expectation amongst patients and inflationary pressure caused by the rising cost of new technologies are amongst the explanations for the funding shortfalls in government funded health systems across the world (Newhouse 1992). The challenge facing these health systems has also been intensified by the worldwide economic downturn. Within health systems, efforts have been made to increase productivity and efficiency and to control costs without reducing quality (Garner and Littlejohns 2011) but the scale of the task necessitates further action (Donaldson et al. 2010). Beyond productivity and efficiency gains the next logical step for decision makers is disinvestment in cost-ineffective services, prioritisation of funding for one service over another or what Prasad (2012) refers to as ‘medical reversal’. The aims of this study were to explore the experiences of budget holders within the English National Health Service (NHS) in their attempts to implement programmes of disinvestment, and to consider factors which influence the success (or otherwise) of this activity. This paper begins with clarification of terminology and a summary of the current state of knowledge with regard to health service disinvestment, before presenting and discussing findings. The research suggests that disinvestment activity is varied across organisations and ranges from ‘invest to save’ schemes through to ‘true disinvestment.’ Although the majority of interviewees accept that disinvestment is necessary most had made little progress at the time of interview beyond ‘picking the low hanging fruit’. Interviewees identify a number of determinants of disinvestment such as: local/national relationships, co-ordination/ collaboration and; professional understanding and support

    Children's suggestibility in relation to their understanding about sources of knowledge

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    In the experiments reported here, children chose either to maintain their initial belief about an object's identity or to accept the experimenter's contradicting suggestion. Both 3– to 4–year–olds and 4– to 5–year–olds were good at accepting the suggestion only when the experimenter was better informed than they were (implicit source monitoring). They were less accurate at recalling both their own and the experimenter's information access (explicit recall of experience), though they performed well above chance. Children were least accurate at reporting whether their final belief was based on what they were told or on what they experienced directly (explicit source monitoring). Contrasting results emerged when children decided between contradictory suggestions from two differentially informed adults: Three– to 4–year–olds were more accurate at reporting the knowledge source of the adult they believed than at deciding which suggestion was reliable. Decision making in this observation task may require reflective understanding akin to that required for explicit source judgments when the child participates in the task
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