scholarly journals Geometric Prepatterning-Based Tuning of the Period Doubling Onset Strain During Thin-Film Wrinkling

2017 ◽  
Vol 84 (5) ◽  
Author(s):  
Sourabh K. Saha
Keyword(s):  
Low Cost ◽  
Period Doubling ◽  
Delay Period ◽  
Natural Period ◽  
Nanoscale Structures ◽  
Formation Behavior ◽  
Sinusoidal Pattern ◽  
System Knowledge ◽  
Practical Scheme ◽  
Nonlinear Pattern

Wrinkling of thin films is an easy-to-implement and low-cost technique to fabricate stretch-tunable periodic micro and nanoscale structures. However, the tunability of such structures is often limited by the emergence of an undesirable period-doubled mode at high strains. Predictively tuning the onset strain for period doubling via existing techniques requires one to have extensive knowledge about the nonlinear pattern formation behavior. Herein, a geometric prepatterning-based technique is introduced that can be implemented even with limited system knowledge to predictively delay period doubling. The technique comprises prepatterning the film/base bilayer with a sinusoidal pattern that has the same period as the natural period of the system. This technique has been verified via physical and computational experiments on the polydimethylsiloxane (PDMS)/glass bilayer system. It is observed that the onset strain can be increased from the typical value of 20% for flat films to greater than 30% with a modest prepattern aspect ratio (2·amplitude/period) of 0.15. In addition, finite element simulations reveal that (i) the onset strain increases with increasing prepattern amplitude and (ii) the delaying effect can be captured entirely by the prepattern geometry. Therefore, one can implement this technique even with limited system knowledge, such as material properties or film thickness, by simply replicating pre-existing wrinkled patterns to generate prepatterned bilayers. Thus, geometric prepatterning is a practical scheme to increase the operating range of stretch-tunable wrinkle-based devices by at least 50%.

Research and Development of Distributed Multistage TMD for Long Period Structure Using Coil Spring

2013 ◽  
Author(s):  
Osamu Furuya ◽  
Hiroshi Kurabayashi
Keyword(s):  
Low Cost ◽  
Tuned Mass Damper ◽  
Installation Space ◽  
Coil Spring ◽  
Additional Mass ◽  
Natural Period ◽  
Long Period ◽  
Compact Size ◽  
Mass Damper ◽  
And Performance

The response control techniques are mainly divided into two categories. One is a storey installation damper type using a damping element such as oil, elasto-plastic, viscoelastic, and so on. The other is an additional mass damper type such as a active and passive type tuned mass damper including a hybrid type. The device configuration of later damper type becomes larger into high-rise structure and long natural period structure because of increase of additional mass in the same case of mass ratio and necessary design stroke of moving mass. In generally, however, it is desired to be a compact size with a same vibration attenuation performance because of that there is a limitation of installation space for the device, and also it is important to be realize the application of the damper with low cost and with a necessary specification for damper performance. This study has been conducted to develop the passive tuned mass damper system using coil spring for long period structure considering a design indexes such as compact size, low cost and robustness. Although a coil spring has been well used by the tuned mass damper system as one way of solving a cost problem and performance stability, the problem of compact size still remains in case of the application to a long period structure. Multistage type is therefore proposed to the system in this time. Furthermore, the distributed TMD theory is applied to the system for robustness of the system. This paper summarizes from a basic theory to the application of proposed device to the real scale long period structure.

scholarly journals Demonstration of thermal modulation using nanoscale and microscale structures for ultralarge pixel array photothermal transducers

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Jinying Zhang ◽  
Defang Li ◽  
Zhuo Li ◽  
Xin Wang ◽  
Suhui Yang
Keyword(s):  
Temperature Difference ◽  
Infrared Imaging ◽  
Wide Spectrum ◽  
Low Cost ◽  
Fold Increase ◽  
Fast Time ◽  
Thermal Modulation ◽  
Nanoscale Structures ◽  
Pixel Array ◽  
Black Coating

AbstractLarge-pixel-array infrared emitters are attractive in the applications of infrared imaging and detection. However, the array scale has been restricted in traditional technologies. Here, we demonstrated a light-driven photothermal transduction approach for an ultralarge pixel array infrared emitter. A metal-black coating with nanoporous structures and a silicon (Si) layer with microgap structures were proposed to manage the thermal input and output issues. The effects of the nanoscale structures in the black coating and microscale structures in the Si layer were investigated. Remarkable thermal modulation could be obtained by adjusting the nanoscale and microscale structures. The measured stationary and transient results of the fabricated photothermal transducers agreed well with the simulated results. From the input view, due to its wide spectrum and high absorption, the black coating with nanoscale structures contributed to a 5.6-fold increase in the temperature difference compared to that without the black coating. From the output view, the microgap structures in the Si layer eliminated the in-plane thermal crosstalk. The temperature difference was increased by 340% by modulating the out-of-plane microstructures. The proposed photothermal transducer had a rising time of 0.95 ms and a falling time of 0.53 ms, ensuring a fast time response. This method is compatible with low-cost and mass manufacturing and has promising potential to achieve ultralarge-array pixels beyond ten million.

Using Vibration Measurements to Assess Structural Integrity

2009 ◽  
Author(s):  
Jared L. Black
Keyword(s):  
Structural Damage ◽  
Structural Integrity ◽  
Low Cost ◽  
Low Frequency ◽  
Vibration Monitoring ◽  
Life Extension ◽  
Structural Vibration ◽  
Natural Period ◽  
Production Area ◽  
Fit For Purpose

Structural vibration monitoring can aid in assessing offshore platform structural integrity. The method utilizes topside acceleration measurements to detect the platform’s natural periods of vibration; the periods depend only on platform weights (mass) and resistance (stiffness). If the platform’s natural period increases over time, in the absence of a change in mass, it can indicate a loss of structural integrity. The vibration survey utilizes a portable monitoring system, which includes sensitive low frequency accelerometers. The above water monitoring provides information on the below water structural integrity; the method is very low cost when compared to diver or ROV surveys. Examples of structural monitoring surveys are presented, including the following: verification that a platform remained fit for purpose despite having its foundation disturbed by a shallow gas release, two cases of using surveys to confirm jacket stiffness recovery following repairs of structural damage caused by Gulf of Mexico hurricanes and evaluation of a minimal platform after a heavy compressor was installed. The development of a natural period database is reviewed. The database, covering 95 platforms in Asian waters, was developed to reduce inspection costs and aid in life extension reviews, as well as providing quick integrity assessments should a tropical cyclone cross the production area.

DYNAMIC COMPLEXITIES IN AN EPIDEMIC MODEL WITH BIRTH PULSES AND PULSE CULLING

2007 ◽  
Vol 17 (02) ◽  
pp. 521-533 ◽  
Author(s):  
SHUJING GAO ◽  
LANSUN CHEN ◽  
ZHIDONG TENG ◽  
DEHUI XIE
Keyword(s):  
Birth Rate ◽  
Discrete Dynamical System ◽  
Sufficient Conditions ◽  
Period Doubling ◽  
Basins Of Attraction ◽  
Complex Dynamic ◽  
Natural Period ◽  
Dynamical Behaviors ◽  
Threshold Conditions ◽  
Fixed Times

In this paper, we propose a model for the dynamics of a fatal infectious disease in a wild animal population with birth pulses and pulse culling, where periodic birth pulses and pulse culling occur at different fixed times. Using the discrete dynamical system determined by stroboscopic map, we obtain an exact cycle of the system, and obtain the threshold conditions for its stability. Bifurcation diagrams are constructed with the birth rate (or culling effort) as the bifurcation parameter, and these are observed to display complex dynamic behaviors, including chaotic bands with period windows, period-doubling and period-halving bifurcations, pitch-fork and tangent bifurcations, nonunique dynamics (meaning that several attractors or attractor and chaos coexist), basins of attraction and attractor crisis. This suggests that birth pulses and pulse culling provide a natural period or cyclicity that makes the dynamical behaviors more complex. Moreover, we investigate the sufficient conditions for global stability of semi-trivial periodic solutions.

Vision Based Force Sensing for Nanorobotic Manipulation

2006 ◽  
Author(s):  
Abhishek Gupta ◽  
Volkan Patoglu ◽  
Marcia K. O'Malley
Keyword(s):  
Visual Feedback ◽  
Force Feedback ◽  
Low Cost ◽  
Primary Component ◽  
Force Sensing ◽  
End Effector ◽  
Nanoscale Structures ◽  
Force Microscopy ◽  
Mechanics Model ◽  
Primary Advantage

Over the last decade, considerable interest has been generated in building and manipulating nanoscale structures. Applications of nanomanipulation include study of nanoparticles, molecules, DNA and viruses, and bottom-up nanoassembly. We propose a Nanomanipulation System using the Zyvex S100 nanomanipulator, which operates within a scanning electron microscope (SEM), as its primary component. The primary advantage of the S100 setup over standard scanning probe microscopy based nanomanipulators is the ability to see the object during manipulation. Relying on visual feedback alone to control the nanomanipulator is not preferable due to perceptual limitations of depth and contact within the SEM. To improve operator performance over visual feedback alone, an impedance-controlled bilateral teleoperation setup is envisioned. Lack of on-board force sensors on the S100 system is the primary hindrance in the realization of the proposed architecture. In this paper, we present a computer vision based force sensing scheme. The advantages of this sensing strategy include its low cost and lack of requirement of hardware modification(s). Force sensing is implemented using an atomic force microscopy (AFM) probe attached to the S100 end-effector. Deformation of the cantilever probe is monitored using a Hough transform based algorithm. These deformations are mapped to corresponding end-effector forces following the Euler-Bernoulli beam mechanics model. The forces thus sensed can be used to provide force-feedback to the operator through a master manipulator.

scholarly journals Development of Rolling Technology for an Iron-Based Shape-Memory-Alloy

2016 ◽  
Vol 854 ◽  
pp. 79-86 ◽  
Author(s):  
Christian Leinenbach ◽  
Christoph Czaderski ◽  
Julien Michels ◽  
Marcel Graf ◽  
Rudolf Kawalla
Keyword(s):  
Shape Memory ◽  
Mechanical Engineering ◽  
Thermal Hysteresis ◽  
Low Cost ◽  
Cost Effective ◽  
Experimental Simulation ◽  
Basic Material ◽  
Formation Behavior ◽  
Commercial Applications ◽  
Rolling Technology

Low cost Fe-Mn-Si based shape memory alloys (SMA) have drawn much attention during the last two decades as a cost-effective alternative to the expensive Ni-Ti based SMA. In particular, the alloy Fe-17Mn-5Si-10Cr-4Ni-1(V,C) (mass%), which has been developed at Empa shows very promising properties with regard to potential commercial applications in civil and mechanical engineering. This alloy has a higher reverse transformation temperature and larger thermal hysteresis in comparison to the Ni-Ti based alloys, which is adequate for producing stable recovery stresses at room temperature. Furthermore, recovery stresses of up to 300 MPa after heating to only 160°C can be achieved without so-called ‘training’ treatment. Furthermore, the alloy can be easily and cost effectively produced under standard air melting and casting conditions. For availability of these heavily microstructure dependent skills for civil and mechanical engineering, e.g. as prestressing elements in concrete structures or coupling/clamping devices, a process chain for manufacturing is necessary. Therefore, a hot and cold rolling technology for strip production with thermal heat treatment processes was developed at TU Bergakademie on base of experimental simulation results. The last one helps to understand the dependencies of deformation parameters, the deformation behavior and their influence to the microstructure evolution in correlation to the recovery.This paper discusses the basic material properties, recovery stress formation behavior and finally the feasibility of the alloy as reinforcing elements in civil engineering applications by using a rolling technology for flat products.

scholarly journals A Light-Weight Vibrational Motor Powered Recoil Robot That Hops Rapidly Across Granular Media

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Alice C. Quillen ◽  
Randal C. Nelson ◽  
Hesam Askari ◽  
Kathryn Chotkowski ◽  
Esteban Wright ◽  
...  
Keyword(s):  
Numerical Model ◽  
Froude Number ◽  
Drag Force ◽  
Granular Media ◽  
Low Cost ◽  
Period Doubling ◽  
Light Weight ◽  
Two Dimensional ◽  
Ball Bouncing ◽  
Vibrating Table

Abstract A 1-cm coin vibrational motor fixed to the center of a 4-cm square foam platform moves rapidly across granular media at a speed of up to 30 cm/s or about 5 body lengths/s. Fast speeds are achieved with dimensionless acceleration number, similar to a Froude number, up to 50, allowing the light-weight 1.4 g mechanism to remain above the substrate, levitated and propelled by its kicks off the surface. The mechanism is low cost and moves across granular media without any external moving parts. With 2-s exposure, we photograph the trajectory of the mechanism with an LED fixed to the mechanism. Trajectories can exhibit period doubling phenomena similar to a ball bouncing on a vibrating table top. A two-dimensional robophysics model is developed to predict mechanism trajectories. We find that a vertical drag force is required in the model to match the height above the surface reached by the mechanism. We attribute the vertical drag force to suction from air flow below the mechanism base and through the granular substrate. Our numerical model suggests that horizontal speed is maximized when the mechanism is prevented from jumping high off the surface. In this way, the mechanism resembles a galloping or jumping animal whose body remains nearly at the same height above the ground during its gait. Our mechanism and model illustrate that speed and efficiency of light-weight hoppers on granular media can be affected by aerodynamics and substrate permeability.

DYNAMIC COMPLEXITIES IN RATIO-DEPENDENT PREDATOR–PREY ECOSYSTEM MODELS WITH BIRTH PULSE AND PESTICIDE PULSE

2004 ◽  
Vol 14 (08) ◽  
pp. 2893-2903 ◽  
Author(s):  
JING HUI ◽  
LAN-SUN CHEN
Keyword(s):  
Discrete Dynamical System ◽  
Period Doubling ◽  
Ecosystem Models ◽  
Pest Population ◽  
Natural Period ◽  
Predator Prey ◽  
Predator Prey Model ◽  
Birth Pulse ◽  
Prey Model ◽  
Ratio Dependent

In many models of pest control, increases in pest population due to birth are assumed to be continuous, but in fact, pest population reproduces only during a single period; at the same time, pesticides are often applied during the period. So in this paper we propose a ratio-dependent predator–prey model with birth pulse and pesticide pulse. Using the discrete dynamical system determined by the stroboscopic map, we obtain an exact periodic solution of systems which have Ricker functions or Beverton–Holt functions, and obtain the threshold conditions for their stability. Above the threshold, there is a characteristic sequence of bifurcations, leading to chaotic dynamics, which implies that the dynamical behaviors of the ratio-dependent predator–prey model with birth pulse and pesticide pulse are very complex, including small-amplitude oscillations, large-amplitude cycles and chaos. This suggests that birth pulse and pesticide pulse, in effect, provide a natural period or cyclicity that allows for period-doubling bifurcation and period-halving bifurcation route to chaos.

Decomposition of the metastable beta titanium alloy Ti-15-3

1983 ◽  
Vol 41 ◽  
pp. 264-265
Author(s):  
Y. L. Chen ◽  
S. Fujlshiro
Keyword(s):  
Low Cost ◽  
High Strength ◽  
Alpha Phase ◽  
Thick Sheet ◽  
Omega Phase ◽  
Beta Titanium Alloy ◽  
Beta Titanium ◽  
Beta Matrix ◽  
Metastable Beta ◽  
Very High

Metastable beta titanium alloys have been known to have numerous advantages such as cold formability, high strength, good fracture resistance, deep hardenability, and cost effectiveness. Very high strength is obtainable by precipitation of the hexagonal alpha phase in a bcc beta matrix in these alloys. Precipitation hardening in the metastable beta alloys may also result from the formation of transition phases such as omega phase. Ti-15-3 (Ti-15V- 3Cr-3Al-3Sn) has been developed recently by TIMET and USAF for low cost sheet metal applications. The purpose of the present study was to examine the aging characteristics in this alloy.The composition of the as-received material is: 14.7 V, 3.14 Cr, 3.05 Al, 2.26 Sn, and 0.145 Fe. The beta transus temperature as determined by optical metallographic method was about 770°C. Specimen coupons were prepared from a mill-annealed 1.2 mm thick sheet, and solution treated at 827°C for 2 hr in argon, then water quenched. Aging was also done in argon at temperatures ranging from 316 to 616°C for various times.

Chromic Acid Etching of Polyethylene

1973 ◽  
Vol 31 ◽  
pp. 72-73
Author(s):  
J. D. Muzzy ◽  
R. D. Hester ◽  
J. L. Hubbard
Keyword(s):  
Chromic Acid ◽  
Low Cost ◽  
Acid Etching ◽  
Crystalline Morphology ◽  
Bulk Specimen ◽  
Morphological Studies ◽  
Perfect Form ◽  
Molecular Length ◽  
Lamellar Texture ◽  
Cost Studies

Polyethylene is one of the most important plastics produced today because of its good physical properties, ease of fabrication and low cost. Studies to improve the properties of polyethylene are leading to an understanding of its crystalline morphology. Polyethylene crystallized by evaporation from dilute solutions consists of thin crystals called lamellae. The polyethylene molecules are parallel to the thickness of the lamellae and are folded since the thickness of the lamellae is much less than the molecular length. This lamellar texture persists in less perfect form in polyethylene crystallized from the melt.Morphological studies of melt crystallized polyethylene have been limited due to the difficulty of isolating the microstructure from the bulk specimen without destroying or deforming it.

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