Advantages of Natural Propulsive Systems

2013 ◽  
Vol 47 (5) ◽  
pp. 37-44 ◽  
Author(s):  
Frank E. Fish
Keyword(s):  
Performance Criteria ◽  
Aquatic Animals ◽  
New Developments ◽  
Marine Propulsion ◽  
Screw Propeller ◽  
Improved Performance

AbstractThe screw propeller has been the mainstay of marine propulsion, but new developments in biomimetic propulsion can provide advantages in terms of speed, maneuverability, efficiency, and stealth. The diversity of aquatic animals provides designs for drag-based paddling and lift-based oscillatory hydrofoils that can be incorporated into engineered propulsive systems for enhanced performance. While the screw propeller will remain the prominent propulsive device, the choice of alternative biomimetic propulsive systems will be dependent on particular applications, where the specifications dictate improved performance criteria.

A discussion on building technology in the 1980s - Defining new materials for the 1980s

1972 ◽  
Vol 272 (1229) ◽  
pp. 579-584
Keyword(s):  
Performance Criteria ◽  
Systematic Evaluation ◽  
New Materials ◽  
Building Science ◽  
New Developments ◽  
Scientific Methods ◽  
Building Research ◽  
Building Technology ◽  
The Future ◽  
Point Of Departure

The author’s point of departure is that building today is the early architecture of the age of science. It increasingly uses scientific methods and technologies of science. Consequently there are many pressures and necessities to innovate, but resistances exist in the form of inertia of the industry, the educational deficiencies of the professions and constructors, the demanding conditions for trouble-free design and construction, and the penalties now consequent upon trouble. In order to open the way for safe innovation there has been a shift towards regulation by performance criteria in place of the former definition by specific requirements; and in order to assess performance in advance of experience, a systematic evaluation is now available. The existence of these two developments has been made possible by the growth of building science, and they in turn define the monitoring and feed-back of experience as important functions of building research for the future. There is a need and capability developing to analyse building problems with increasing precision in several directions, and the process often defines new needs for materials and techniques. This is a centreto-periphery process, and the reverse also takes place, where product makers thrust into the market innovations which result from some matching of fresh ideas to apparent needs. In all cases the needs are defined consciously or unconsciously from the context of the subsystem within which the product or component will function. Buildings are always systems comprising many subsystems. Examples are then given of directions in which the author foresees needs for new developments being defined.

Improvement of a Forward Dynamic Predictive Human Gait Model

2019 ◽  
Author(s):  
Jessica B. Thayer ◽  
Philip A. Voglewede
Keyword(s):  
Predictive Control ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Performance Criteria ◽  
Human Gait ◽  
Optimization Criteria ◽  
Optimization Framework ◽  
Normal Gait ◽  
The Central Nervous System ◽  
Improved Performance

Abstract Lack of understanding of human gait is detrimental to the development of gait related treatments and devices. This study improves a dynamic, predictive model of human gait which uses model predictive control (MPC) to replicate the control of the central nervous system (CNS). In this work, improved performance criteria, including metabolic cost and dynamic effort, are developed using an existing optimization framework to better mimic control of the CNS. Consistent with existing literature, incorporating dynamic effort and COM energy into the objective function improved gait simulations. This study also demonstrates COM energy and dynamic effort can both be used to predict metabolic energy consumption, which is likely the primary optimization criteria in normal gait generation.

The Propeller: How Many Blades?

1941 ◽  
Vol 45 (368) ◽  
pp. 267-274
Author(s):  
F. W. Lanchester
Keyword(s):  
Propeller Blade ◽  
Helical Surface ◽  
Vortex Theory ◽  
Marine Propulsion ◽  
Screw Propeller ◽  
The Way

Propeller theory has always been a subject of extreme difficulty, and those who riginated the screw propeller as a means of propulsion and developed itduring the latter half of last century were in most part guided by common senseand empiricism. Without much in the way of theory to guide them the results thus achieved in connection with marine propulsion were remarkable—but little short of the best possible. The designers of the early experimental aircraft were able to make use of the wealth of experience thus placed at their disposal; nevertheless, some new aspects of the problem presented themselves—fortunately the vortex theory, newly developed to deal with the problem of sustentation in flight came to their aid, though the manner of its application was not obvious or easy. The writer's first attempt consisted in treating the propeller blade as an aerofoil connected to the boss by an arm of spar section, geometrically related to a helical surface, in which the tracks of the blades relatively to the fluid follow these surfaces.

New Developments in Marine Propulsion Controls

1975 ◽  
Author(s):  
Harold M. Mathers ◽  
Dennis J. Kammeyer
Keyword(s):  
New Developments ◽  
Marine Propulsion

Quantitative nano-characterization of heterogeneous catalysts

1995 ◽  
Vol 53 ◽  
pp. 398-399
Author(s):  
P.A. Crozier ◽  
M. Pan
Keyword(s):  
Heterogeneous Catalysts ◽  
Low Dose ◽  
Imaging Techniques ◽  
Structural Features ◽  
Catalyst Characterization ◽  
New Developments ◽  
Double Phase ◽  
Phase Systems ◽  
Dose Imaging

Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.

Toward The Simultaneous Correction of Spherical and Chromatic Aberration in Electron Optics by Means of an Electrostatic Electron Mirror

1990 ◽  
Vol 48 (1) ◽  
pp. 206-207
Author(s):  
Gertrude. F. Rempfer
Keyword(s):  
Chromatic Aberration ◽  
Transverse Magnetic ◽  
Objective Lens ◽  
Ion Imaging ◽  
Corrected Image ◽  
Electric And Magnetic Fields ◽  
Chromatic Aberrations ◽  
Improved Performance ◽  
Electron Microscopes ◽  
Image Planes

Optimum performance in electron and ion imaging instruments, such as electron microscopes and probe-forming instruments, in most cases depends on a compromise either between imaging errors due to spherical and chromatic aberrations and the diffraction error or between the imaging errors and the current in the image. These compromises result in the use of very small angular apertures. Reducing the spherical and chromatic aberration coefficients would permit the use of larger apertures with resulting improved performance, granted that other problems such as incorrect operation of the instrument or spurious disturbances do not interfere. One approach to correcting aberrations which has been investigated extensively is through the use of multipole electric and magnetic fields. Another approach involves the use of foil windows. However, a practical system for correcting spherical and chromatic aberration is not yet available.Our approach to correction of spherical and chromatic aberration makes use of an electrostatic electron mirror. Early studies of the properties of electron mirrors were done by Recknagel. More recently my colleagues and I have studied the properties of the hyperbolic electron mirror as a function of the ratio of accelerating voltage to mirror voltage. The spherical and chromatic aberration coefficients of the mirror are of opposite sign (overcorrected) from those of electron lenses (undercorrected). This important property invites one to find a way to incorporate a correcting mirror in an electron microscope. Unfortunately, the parts of the beam heading toward and away from the mirror must be separated. A transverse magnetic field can separate the beams, but in general the deflection aberrations degrade the image. The key to avoiding the detrimental effects of deflection aberrations is to have deflections take place at image planes. Our separating system is shown in Fig. 1. Deflections take place at the separating magnet and also at two additional magnetic deflectors. The uncorrected magnified image formed by the objective lens is focused in the first deflector, and relay lenses transfer the image to the separating magnet. The interface lens and the hyperbolic mirror acting in zoom fashion return the corrected image to the separating magnet, and the second set of relay lenses transfers the image to the final deflector, where the beam is deflected onto the projection axis.

Instrumental Assessment in Cleft Palate Care

2013 ◽  
Vol 23 (2) ◽  
pp. 49-61 ◽  
Author(s):  
Jamie Perry ◽  
Graham Schenck
Keyword(s):  
Cleft Palate ◽  
New Developments ◽  
Perceptual Evaluation ◽  
Advantages And Disadvantages ◽  
Instrumental Assessment ◽  
Speech Language Pathologist ◽  
Hypernasal Speech ◽  
Perceptual Assessment ◽  
Velopharyngeal Function ◽  
And Function

Despite advances in surgical management, it is estimated that 20–30% of children with repaired cleft palate will continue to have hypernasal speech and require a second surgery to create normal velopharyngeal function (Bricknell, McFadden, & Curran, 2002; Härtel, Karsten, & Gundlach, 1994; McWilliams, 1990). A qualitative perceptual assessment by a speech-language pathologist is considered the most important step of the evaluation for children with resonance disorders (Peterson-Falzone, Hardin-Jones, & Karnell, 2010). Direct and indirect instrumental analyses should be used to confirm or validate the perceptual evaluation of an experienced speech-language pathologist (Paal, Reulbach, Strobel-Schwarthoff, Nkenke, & Schuster, 2005). The purpose of this article is to provide an overview of current instrumental assessment methods used in cleft palate care. Both direct and indirect instrumental procedures will be reviewed with descriptions of the advantages and disadvantages of each. Lastly, new developments for evaluating velopharyngeal structures and function will be provided.

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