scholarly journals Multi-stable composite twisting structure for morphing applications

2012 ◽  
Vol 468 (2141) ◽  
pp. 1230-1251 ◽  
Author(s):  
X. Lachenal ◽  
P. M. Weaver ◽  
S. Daynes
Keyword(s):  
Analytical Model ◽  
Material Properties ◽  
Degrees Of Freedom ◽  
Design Parameters ◽  
Engineering Structures ◽  
The Past ◽  
Wide Range ◽  
Morphing Structure ◽  
Low Mass ◽  
Unstable States

Conventional shape-changing engineering structures use discrete parts articulated around a number of linkages. Each part carries the loads, and the articulations provide the degrees of freedom of the system, leading to heavy and complex mechanisms. Consequently, there has been increased interest in morphing structures over the past decade owing to their potential to combine the conflicting requirements of strength, flexibility and low mass. This article presents a novel type of morphing structure capable of large deformations, simply consisting of two pre-stressed flanges joined to introduce two stable configurations. The bistability is analysed through a simple analytical model, predicting the positions of the stable and unstable states for different design parameters and material properties. Good correlation is found between experimental results, finite-element modelling and predictions from the analytical model for one particular example. A wide range of design parameters and material properties is also analytically investigated, yielding a remarkable structure with zero stiffness along the twisting axis.

Preliminary Experimental Study of SMA Knitted Actuation Architectures

Aerospace ◽  
2006 ◽  
Author(s):  
Julianna Evans ◽  
Diann Brei ◽  
Jonathan Luntz
Keyword(s):  
Experimental Study ◽  
Smart Materials ◽  
Material Properties ◽  
Geometric Parameters ◽  
Design Parameters ◽  
Static Force ◽  
Vast Array ◽  
Material Parameters ◽  
Wide Range ◽  
And Control

Nature builds an immense set of materials exhibiting a wide range of behaviors using only a small number of basic compounds. The range of materials comes about through architecture, giving functional structure to the basic materials. Analogously, a new genre of actuators can be derived from existing smart materials through architecture. This paper presents a preliminary experimental study of knitted actuation architectures that yield high strains (up to 73%) with moderate forces (tens of Newtons or more) from basic contracting smart material fibers. By different combinations of the two primary knit loops – purl and knit – a variety of behaviors can be achieved including contraction, rolling, spirals, accordions, arching, and any combination of these across the fabric. This paper catalogs several basic knit stitches and their actuated form: garter, stockinette, seed, rib and I-cord. These knitted architectures provide performance tailorability (force, strain, stiffness, and motion) by manipulation of key design parameters such as the material properties of the wire, the geometric parameters (wire diameter, loop size, and gauge), and architectural parameters (stitch type and orientation). This is demonstrated via a quasi-static force-deflection experimental study with several shape memory alloy garter prototypes with varying geometric parameters. While the basic architecture of a knit is simple, it affords a vast array of architectural combinations and control of geometrical and material parameters that generate a myriad of gross motion capabilities beyond that of current day actuation strategies.

Probabilistic Optimum Design of Compact Spur Gear Sets

1995 ◽  
Author(s):  
Chinyere Onwubiko ◽  
Landon Onyebueke ◽  
Feng C. Chen
Keyword(s):  
Optimum Design ◽  
Material Properties ◽  
Probabilistic Method ◽  
Spur Gear ◽  
Optimization Techniques ◽  
Design Parameters ◽  
Deterministic Method ◽  
Wide Range ◽  
Comparison Of The Results ◽  
Center Distance

Abstract Several methods have been proposed in the past for optimum design of spur gears. These methods have utilized deterministic design optimization techniques to obtain what could be considered satisfactory design parameters. At least two problems arise with the results of the deterministic approach; the inability to deal with uncertainties in material properties and over conservative design. On the other hand, probabilistic analysis methodology seeks to account for the uncertainties in material properties, loading conditions and disparate failure models. This paper discusses the application of probabilistic design methodology to the design of compact gear set. This is done by minimizing the gear center distance while constrained by the allowable surface pressure and bending stress. A comparison of the results of compact gear design using both deterministic and probabilistic methodologies is presented. The results indicate that deterministic method though satisfactory does not provide the designer enough information to make vast design decisions. The deterministic method provides only one value of the center distance while the probabilistic method provides the designer a range of choices. In fact, a designer is provided a wide range of design options depending on a desired level of reliability.

A Model for the Pull-In Parameters of Magnetostatic Actuators with Fringing Effect

2013 ◽  
Vol 432 ◽  
pp. 229-234
Author(s):  
Yu Ming Fang ◽  
Jun Jian Qie
Keyword(s):  
Analytical Model ◽  
Simple Analytical Model ◽  
The Past ◽  
Wide Range ◽  
Mems Actuators ◽  
Fringing Field ◽  
Simulation Results ◽  
Fringing Field Effect ◽  
Gap Spacing ◽  
Good Agreement

Predicting Pull-In parameters is crucial in the design of MEMS actuators. In the past, the Pull-In parameters of magnetostatic actuators with the fringing field effect are often estimated using finite element method (FEM). However, FEM is cumbersome, time consuming and non-transparent, which is not convenient for the design optimization. Usually, there are a simple analytical model without leakage reluctance and a detailed analytical model with leakage reluctance respectively. This paper used the two models to derive the Pull-In model of magnetostatic actuators respectively. The accuracy of the two Pull-In models is examined by comparing their results with the FEM results. Simulation results show that the Pull-In model without leakage reluctance is unsuitable to predict Pull-In parameters. The Pull-In model with leakage reluctance has shown a good agreement with the FEM results for a wide range of gap spacing.

"SOFT" EXOSKELETONS FOR UPPER AND LOWER BODY REHABILITATION — DESIGN, CONTROL AND TESTING

2007 ◽  
Vol 04 (03) ◽  
pp. 549-573 ◽  
Author(s):  
DARWIN G. CALDWELL ◽  
N. G. TSAGARAKIS ◽  
SOPHIA KOUSIDOU ◽  
NELSON COSTA ◽  
IOANNIS SARAKOGLOU
Keyword(s):  
Degrees Of Freedom ◽  
Emergency Services ◽  
Lower Limbs ◽  
Medical Rehabilitation ◽  
Lower Body ◽  
Actuation System ◽  
Wide Range ◽  
Low Mass ◽  
Effective Use ◽  
Muscle Actuators

The basic concepts for exoskeletal systems have been suggested for some time with applications ranging from construction, manufacturing and mining to rescue and emergency services. In recent years, research has been driven by possible uses in medical/rehabilitation and military applications. Yet there are still significant barriers to the effective use and exploitation of this technology. Among the most pertinent of these factors is the power and actuation system and its impact of control, strength, speed and, perhaps most critically, safety. This work describes the design, construction and testing of an ultra low-mass, full-body exoskeleton system having seven degrees of freedom (DOFs) for the upper limbs and five degrees of freedom (DOFs) for each of the lower limbs. This low mass is primarily due to the use of a new range of pneumatic muscle actuators as the power source for the system. The work presented will show how the system takes advantage of the inherent controllable compliance to produce a unit that is powerful, providing a wide range of functionality (motion and forces over an extended range) in a manner that has high safety integrity for the user. The general layout of both the upper and the lower body exoskeleton is presented together with results from preliminary experiments to demonstrate the potential of the device in limb retraining, rehabilitation and power assist (augmentation) operations.

Optical Properties of HVEM Accelerators

1975 ◽  
Vol 33 ◽  
pp. 180-181
Author(s):  
A. Strojnik ◽  
J.W. Scholl ◽  
V. Bevc
Keyword(s):  
Optical Properties ◽  
Electron Accelerator ◽  
Systematic Investigation ◽  
Electron Source ◽  
High Brightness ◽  
The Past ◽  
Wide Range ◽  
Optical Behavior

The electron accelerator, as inserted between the electron source (injector) and the imaging column of the HVEM, is usually a strong lens and should be optimized in order to ensure high brightness over a wide range of accelerating voltages and illuminating conditions. This is especially true in the case of the STEM where the brightness directly determines the highest resolution attainable. In the past, the optical behavior of accelerators was usually determined for a particular configuration. During the development of the accelerator for the Arizona 1 MEV STEM, systematic investigation was made of the major optical properties for a variety of electrode configurations, number of stages N, accelerating voltages, 1 and 10 MEV, and a range of injection voltages ϕ0 = 1, 3, 10, 30, 100, 300 kV).

Pursuit of the Abscopal Effect

2020 ◽  
Vol 04 (04) ◽  
pp. 369-372
Author(s):  
Paul B. Romesser ◽  
Christopher H. Crane
Keyword(s):  
Tumor Immunology ◽  
Antitumor Immunity ◽  
Clinical Success ◽  
Immune Recognition ◽  
Immune Modulators ◽  
Cancer Subtypes ◽  
The Past ◽  
Tumor Irradiation ◽  
Wide Range ◽  
Tumor Recognition

AbstractEvasion of immune recognition is a hallmark of cancer that facilitates tumorigenesis, maintenance, and progression. Systemic immune activation can incite tumor recognition and stimulate potent antitumor responses. While the concept of antitumor immunity is not new, there is renewed interest in tumor immunology given the clinical success of immune modulators in a wide range of cancer subtypes over the past decade. One particularly interesting, yet exceedingly rare phenomenon, is the abscopal response, characterized by a potent systemic antitumor response following localized tumor irradiation presumably attributed to reactivation of antitumor immunity.

The Many Pasts of Detective Fiction

2020 ◽  
Vol 1 (2) ◽  
pp. 157-172
Author(s):  
Thomas Leitch
Keyword(s):  
Detective Fiction ◽  
Golden Age ◽  
Public History ◽  
Detective Novel ◽  
Sherlock Holmes ◽  
Detective Story ◽  
The Past ◽  
Wide Range ◽  
Detective Novels ◽  
The Many

Building on Tzvetan Todorov's observation that the detective novel ‘contains not one but two stories: the story of the crime and the story of the investigation’, this essay argues that detective novels display a remarkably wide range of attitudes toward the several pasts they represent: the pasts of the crime, the community, the criminal, the detective, and public history. It traces a series of defining shifts in these attitudes through the evolution of five distinct subgenres of detective fiction: exploits of a Great Detective like Sherlock Holmes, Golden Age whodunits that pose as intellectual puzzles to be solved, hardboiled stories that invoke a distant past that the present both breaks with and echoes, police procedurals that unfold in an indefinitely extended present, and historical mysteries that nostalgically fetishize the past. It concludes with a brief consideration of genre readers’ own ambivalent phenomenological investment in the past, present, and future each detective story projects.

Nine Centuries of Man

2017 ◽  
Keyword(s):  
Twentieth Century ◽  
Diverse Range ◽  
Gender Expectations ◽  
Court Records ◽  
The Past ◽  
Wide Range ◽  
Police Reports ◽  
Late Twentieth ◽  
Scottish History ◽  
Late Twentieth Century

What did it mean to be a man in Scotland over the past nine centuries? Scotland, with its stereotypes of the kilted warrior and the industrial ‘hard man’, has long been characterised in masculine terms, but there has been little historical exploration of masculinity in a wider context. This interdisciplinary collection examines a diverse range of the multiple and changing forms of masculinities from the late eleventh to the late twentieth century, exploring the ways in which Scottish society through the ages defined expectations for men and their behaviour. How men reacted to those expectations is examined through sources such as documentary materials, medieval seals, romances, poetry, begging letters, police reports and court records, charity records, oral histories and personal correspondence. Focusing upon the wide range of activities and roles undertaken by men – work, fatherhood and play, violence and war, sex and commerce – the book also illustrates the range of masculinities that affected or were internalised by men. Together, the chapters illustrate some of the ways Scotland’s gender expectations have changed over the centuries and how, more generally, masculinities have informed the path of Scottish history

Free but fragile: Human relations amidst poverty and HIV in democratic South Africa

2015 ◽  
Vol 2 (2) ◽  
pp. 85-94
Author(s):  
Christina Landman
Keyword(s):  
South Africa ◽  
Predominantly White ◽  
Black People ◽  
Hiv Treatment ◽  
Human Relations ◽  
White People ◽  
Black And White ◽  
The Past ◽  
Wide Range ◽  
Black Township

Dullstroom-Emnotweni is the highest town in South Africa. Cold and misty, it is situated in the eastern Highveld, halfway between the capital Pretoria/Tswane and the Mozambique border. Alongside the main road of the white town, 27 restaurants provide entertainment to tourists on their way to Mozambique or the Kruger National Park. The inhabitants of the black township, Sakhelwe, are remnants of the Southern Ndebele who have lost their land a century ago in wars against the whites. They are mainly dependent on employment as cleaners and waitresses in the still predominantly white town. Three white people from the white town and three black people from the township have been interviewed on their views whether democracy has brought changes to this society during the past 20 years. Answers cover a wide range of views. Gratitude is expressed that women are now safer and HIV treatment available. However, unemployment and poverty persist in a community that nevertheless shows resilience and feeds on hope. While the first part of this article relates the interviews, the final part identifies from them the discourses that keep the black and white communities from forming a group identity that is based on equality and human dignity as the values of democracy.

Sign in / Sign up

Export Citation Format

Share Document