scholarly journals Specific Modeling Issues on an Adaptive Winglet Skeleton

2021 ◽  
Vol 11 (8) ◽  
pp. 3565
Author(s):  
Salvatore Ameduri ◽  
Ignazio Dimino ◽  
Antonio Concilio ◽  
Umberto Mercurio ◽  
Lorenzo Pellone
Keyword(s):  
Adaptive Systems ◽  
Single Point ◽  
Mesh Size ◽  
The Other ◽  
Stress And Strain ◽  
Ongoing Research ◽  
Local Methods ◽  
Numerical Effect ◽  
Optimal Efficiency ◽  
Structural Architecture

Morphing aeronautical systems may be used for a number of aims, ranging from improving performance in specific flight conditions, to keeping the optimal efficiency over a certain parameters domain instead of confining it to a single point, extending the flight envelope, and so on. An almost trivial statement is that traditional skeleton architectures cannot be held as a structure modified from being rigid to deformable. That passage is not simple, as a structure that is able to be modified shall be designed and constructed to face those new requirements. What is not marginal, is that the new configurations can lead to some peculiar problems for both the morphing and the standard, supporting, elements. In their own nature, in fact, adaptive systems are designed to contain all the parts within the original geometry, without any “external adjoint”, such as nacelles or others. Stress and strain distribution may vary a lot with respect to usual structures and some particular modifications are required. Sometimes, it happens that the structural behavior does not match with the common experience and some specific adjustment shall be done to overcome the problem. What is reported in this paper is a study concerning the adaptation of the structural architecture, used to host a winglet morphing system, to make it accomplish the original requirements, i.e., allow the deformation values to be under the safety threshold. When facing that problem, an uncommon behavior of the finite element (FE) solver has been met: the safety factors appear to be tremendously dependent on the mesh size, so as to raise serious questions about the actual expected value, relevant for the most severe load conditions. On the other side, such singularities are more and more confined into single points (or single lines), as the mesh refines, so to evidence somehow the numerical effect behind those results. On the other side, standard engineering local methods to reduce the abovementioned strain peaks seem to work very well in re-distributing the stress and strain excesses to the whole system domain. The work does not intend to give an answer to the presented problem, being instead focused on describing its possible causes and its evident effects. Further work is necessary to detect the original source of such inconsistencies, and propose and test operative solutions. That will be the subject of the next steps of the ongoing research.

scholarly journals Purcell’s Three-Link Swimmer: Assessment of Geometry and Gaits for Optimal Displacement and Efficiency

Mathematics ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1088
Author(s):  
Cristina Nuevo-Gallardo ◽  
José Emilio Traver ◽  
Inés Tejado ◽  
Blas M. Vinagre
Keyword(s):  
Reynolds Number ◽  
Multiobjective Optimization ◽  
The Other ◽  
Optimal Method ◽  
Optimal Velocity ◽  
Motion Primitives ◽  
Motion Primitive ◽  
Control Objective ◽  
Optimal Efficiency ◽  
The One

This paper studies the displacement and efficiency of a Purcell’s three-link microswimmer in low Reynolds number regime, capable of moving by the implementation of a motion primitive or gait. An optimization is accomplished attending to the geometry of the swimmer and the motion primitives, considering the shape of the gait and its amplitude. The objective is to find the geometry of the swimmer, amplitude and shape of the gaits which make optimal the displacement and efficiency, in both an individual way and combined (the last case will be referred to as multiobjective optimization). Three traditional gaits are compared with two primitives proposed by the authors and other three gaits recently defined in the literature. Results demonstrate that the highest displacement is obtained by the Tam and Hosoi optimal velocity gait, which also achieves the best efficiency in terms of energy consumption. The rectilinear and Tam and Hosoi optimal efficiency gaits are the second optimum primitives. Regarding the multiobjective optimization and considering the two criteria with the same weight, the optimum gaits turn out to be the rectilinear and Tam and Hosoi optimal efficiency gaits. Thus, the conclusions of this study can help designers to select, on the one hand, the best swimmer geometry for a desired motion primitive and, on the other, the optimal method of motion for trajectory tracking for such a kind of Purcell’s swimmers depending on the desired control objective.

Size Selectivity of Diamond and Square Mesh Codends in Pelagic Herring Trawls: Only Small Herring Will Notice the Difference

1992 ◽  
Vol 49 (10) ◽  
pp. 2104-2117 ◽  
Author(s):  
Petri Suuronen ◽  
Russell B. Millar
Keyword(s):  
Relative Size ◽  
Mesh Size ◽  
The Other ◽  
Size Selectivity ◽  
The Difference ◽  
Catch Rates ◽  
Two Sides ◽  
High Catch

A twin codend trawl was fished in the northern Baltic to study the size selectivity of square mesh and diamond mesh codends of 36-mm nominal mesh size. For each codend, 15 hauls were completed with a small mesh (20 mm) codend deployed on the other side of the trawl. The relative size of the catches in the two sides of the trawl varied considerably from haul to haul (the separator section was not operating properly) and selection curves were estimated from each individual haul using a method that incorporated the differences in catching efficiency of the two sides. The length of 50% retention decreased with increased catch for both the diamond and square mesh codends, although in neither case was this relationship statistically significant. Selection curves fitted to the combined haul data were asymmetric. The square mesh codend retained significantly less small herring than the diamond mesh codend, and for larger herring the two codends had similar selectivity. In both codends, most escapes occurred at the front of the catch bulge, from the upper side of the codend. At high catch rates, mesh blockage was observed for several metres ahead of the catch bulge during the later part of the tow.

scholarly journals Siphonophora from the coast of Brazil (17ºS to 24ºS)

1991 ◽  
Vol 39 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Catarina Ramis Nogueira ◽  
Sérgio dos Reis Oliveira Jr
Keyword(s):  
East Coast ◽  
Coastal Upwelling ◽  
Mesh Size ◽  
Abundant Species ◽  
Factorial Analysis ◽  
The Other ◽  
Trophic Interaction ◽  
Principal Axes ◽  
Bank System

This work is based on the analysis of 99 zooplankton samples collected during the Oceanographic Expedition "ESPÍRITO SANTO I", held along the east coast of Brazil, between Cabo Frio and Abrolhos Archipelago, an area characterized by the occurrence of coastal upwelling, from July to September 1984. Zooplankton was collected with vertical plankton net hauls of 250 µm mesh size in the upper 200 meters layer. A total of twenty one species of Siphonophora was observed, two of which were identified as being physonect and the other as calycophorans. Specific diversity close to the shore and at the neighborhood of the Vitória-Trindade Bank System, showed smaller values, in comparison with those in the oceanic regions. Factorial analysis was used in order to access the changes observed in the population of the eleven most abundant species. The first two principal axes represented the influence of the nearshore - offshore gradient and the role of trophic interaction, accounted for 60% of the total variance of the data.

scholarly journals Comparison of Multicast Algorithm Evaluation Results in Low and High Multicast Saturation Environments

2019 ◽  
Vol 3 ◽  
pp. 3-7
Author(s):  
Krzysztof Stachowiak ◽  
Piotr Zwierzykowski
Keyword(s):  
Quality Of Service ◽  
Computational Complexity ◽  
Optimization Methods ◽  
The Other ◽  
Ongoing Research ◽  
Mathematical Problems ◽  
Point To Point ◽  
Difficult Challenge ◽  
Entire Network

The multicast quality of service-enabled routing is a computationally challenging task. Despite ongoing research efforts, the associated mathematical problems are still considered to be NP-hard. In certain applications, computational complexity of finding the optimal connection between a set of network devices may be a particularly difficult challenge. For example, connecting a small group of participants of a teleconference is not much more complex than setting up a set of mutual point-to-point connections. On the other hand, satisfying the demand for such services as IPTV, with their receivers constituting the majority of the network, requires applying appropriate optimization methods in order to ensure real system execution. In this paper, algorithms solving this class of problems are considered. The notion of multicast saturation is introduced to measure the amount of multicast participants relative to the entire network, and the efficiency of the analyzed algorithms is evaluated for different saturation degrees.

3-D BIODYNAMIC CONSTRAINT CONDITIONS WITH THREE SEGMENTS AND TWO ARTICULATING JOINTS ON THE HUMAN KNEE

2002 ◽  
Vol 14 (05) ◽  
pp. 183-188
Author(s):  
XISHI WANG ◽  
LI-QUN ZHANG
Keyword(s):  
Knee Joint ◽  
Lower Extremity ◽  
Patellofemoral Joint ◽  
Single Point ◽  
Point Contact ◽  
The Other ◽  
Human Knee ◽  
Human Knee Joint ◽  
Constraint Modeling ◽  
Biodynamic Modeling

In the paper, the 3-D biodynamic constraint conditions with three-segments (femur-patella-tibia) and two articulating joints (patellofemoral joint and tibiaofemoral joint) on the human knee are established. These constraint conditions of motion accommodate two situations: a two-point and a single-point contact on the patellofemoral joint and tibiaofemoral joint. On the other word, the present constraint modeling includes both rolling and sliding motions between the patella-femoral joint and tibia-femoral joint. This study can be explored a realistically 3-D biodynamic modeling of the human knee joint or human lower extremity.

An Amendment Method for Stress and Strain of Double-Curved Laminated Composite

2007 ◽  
Vol 561-565 ◽  
pp. 757-760
Author(s):  
Yong Shou Liu ◽  
Jun Liu ◽  
An Qiang Wang ◽  
Zhu Feng Yue
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Laminated Composite ◽  
Mesh Size ◽  
Stress And Strain ◽  
Complex Structures ◽  
Coarse Mesh ◽  
Element Analysis ◽  
User Material Subroutine ◽  
Modified Formula

In this paper, an amendment method for stress and strain of double-curved laminated composite is proposed and studied. According to finite element analysis results of the same model with two different mesh size (coarse mesh size 120mm× 300mm and refined mesh size 30mm× 30mm ), stress and strain have been amended with modified formula in user material subroutine (UMAT) subprogram so that the corrected results of model with coarse mesh is similar to the results of model with refined mesh. Using this method, with coarse mesh, a satisfied accuracy results still can be obtained without refining mesh. It’s efficient for design and analysis of complex structures.

EDITORIAL: "TECHNOLOGY AND ORGANISATION: A SPECIAL ISSUE IN HONOUR OF KEITH PAVITT"

2005 ◽  
Vol 09 (01) ◽  
pp. v-xi ◽  
Author(s):  
JONATHAN SAPSED ◽  
PETER AUGSDÖRFER ◽  
JAMES UTTERBACK
Keyword(s):  
Technological Change ◽  
Innovation Management ◽  
The Other ◽  
Future Research ◽  
Special Issue ◽  
Ongoing Research ◽  
Technology And Innovation ◽  
Management Of Technology ◽  
Research Agendas ◽  
The Impact

In honour of the late Keith Pavitt, we introduce this Special Issue of International Journal of Innovation Management. We discuss the impact of Pavitt's work in technology and innovation on the management field. He showed empirically a number of core principles of technological change and knowledge, and how these affected managerial and organisational tasks. His influence is indicated by his publication channels, citations to his work and the other authors with whom he was cited. Pavitt had signalled several themes for future research in the management of technology and innovation. This introduction explains how the articles of this special issue make contributions to all these ongoing research agendas.

On the effect of wear on small mesh wire sieves

1923 ◽  
Vol 13 (4) ◽  
pp. 467-482 ◽  
Author(s):  
Bernard A. Keen ◽  
William B. Haines
Keyword(s):  
Mesh Size ◽  
Wire Diameter ◽  
The Other ◽  
Double Peaks ◽  
Distribution Of Values ◽  
Metal Framework ◽  
The Wire ◽  
Two Peaks ◽  
Frequency Curves

A series of measurements of wire diameter, length of side, and area of holes, has been made on new and used sieves, all of which were originally of the “100 mesh” size, i.e. the square holes were supposed to be ·01″ in length of side and the wire to be ·01″ in diameter. The measurements have been expressed as frequency curves.In the case of unused sieves woven to the I.M.M. specification, the sieve on the whole compared well with the specification, but in used sieves the variations were much greater. The divergence from specification in the new and old sieves is shown by Tables I and II respectively.In one sieve (No. 2) the holes elongated more in one direction than the other. In fact in one direction the alteration which has taken place is a contraction rather than a stretch. This effect was probably connected with the manner in which the sieve was attached to its metal framework, and also to difference in tempering of the wires and the tension in weaving.A number of the frequency curves showed double peaks, and the actual observations showed that there was a systematic distribution of values corresponding to these two peaks. It is probable that some of the guides in one of the combs through which the warp wires are led during the weaving were displaced sideways, thus giving alternate strands of wire and narrow holes. This was particularly the case in the single weave.

Mechanical Fastener Designs for Use in the Microassembly of 3D Microstructures

2004 ◽  
Author(s):  
Nikolai Dechev ◽  
James K. Mills ◽  
William L. Cleghorn
Keyword(s):  
Experimental Results ◽  
The Other ◽  
Ongoing Research ◽  
Interference Fit ◽  
Ongoing Work ◽  
Mechanical Fasteners ◽  
Micro Parts ◽  
Lock Joint ◽  
Mechanical Fastener

This paper describes micro-mechanical fastener designs used to create joints between surface micromachined micro-parts. This is part of ongoing research to develop a general microassembly system capable of assembling various types of microstructures. The microassembly system is based on sequential robotic operations and the use of a microgripper. Two new joint designs referred to as ‘key-lock’ joints and ‘inter-lock’ joints are introduced. Key-lock joints are created by the insertion of a ‘key’ on one micro-part, into a mating slot on another micro-part. By translating the first micro-part within the other, after the key is inserted, it becomes locked into position. Inter-lock joints are created by the perpendicular insertion of one micro-part with a slit, into another micro-part with a slit. The slits create an interference fit and are permanent once the micro-parts are joined. The design of these joints and the experimental results are detailed. In addition, ongoing work involving recent ‘snap-lock’ joint fastener designs is described. This includes an example of a 3D micro-transformer and a stacked microstructure. These various micro-mechanical fasteners demonstrate a number of ways in which micro-parts can be assembled into 3D microstructures.

A Dynamic Model Balancing User Control and Workload in Automatic and Adaptive Systems

2007 ◽  
Vol 51 (4) ◽  
pp. 186-190
Author(s):  
Shelley Roberts ◽  
Avi Parush
Keyword(s):  
User Interfaces ◽  
Adaptive Systems ◽  
Interactive Systems ◽  
The Other ◽  
Dynamic Changes ◽  
Trade Off ◽  
Controlled Systems ◽  
Adaptive User Interfaces ◽  
Interface Adaptation ◽  
The One

Current interactive systems are criticized for having complex interfaces that overload users with information. Two possible solutions to manage overload are automatic interfaces that augment user capabilities, and user-controlled systems that provide support. These two types of interfaces introduce a trade-off: On the one hand, automatic interfaces alleviate workload but create performance problems associated with the absence of control. On the other hand, user-controlled interfaces afford users more control, which may come with additional workload. Based on the analysis of adaptive user interfaces and automation, a model is proposed where automatic and user interface adaptation are in a multidimensional and continuum-based space, allowing for modelling dynamic changes to the roles the human and machine play at various stages of interaction.

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