scholarly journals Field responsive mechanical metamaterials

2018 ◽  
Vol 4 (12) ◽  
pp. eaau6419 ◽  
Author(s):  
Julie A. Jackson ◽  
Mark C. Messner ◽  
Nikola A. Dudukovic ◽  
William L. Smith ◽  
Logan Bekker ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Environmental Conditions ◽  
Dynamic Control ◽  
Magnetorheological Fluid ◽  
Complex Structures ◽  
New Class ◽  
Mechanical Metamaterials ◽  
Application Requirements ◽  
Careful Design ◽  
Selection Of

Typically, mechanical metamaterial properties are programmed and set when the architecture is designed and constructed, and do not change in response to shifting environmental conditions or application requirements. We present a new class of architected materials called field responsive mechanical metamaterials (FRMMs) that exhibit dynamic control and on-the-fly tunability enabled by careful design and selection of both material composition and architecture. To demonstrate the FRMM concept, we print complex structures composed of polymeric tubes infilled with magnetorheological fluid suspensions. Modulating remotely applied magnetic fields results in rapid, reversible, and sizable changes of the effective stiffness of our metamaterial motifs.

Vibration Isolator System for Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 182-183
Author(s):  
K. Ohi ◽  
M. Mizuno ◽  
T. Kasai ◽  
Y. Ohkura ◽  
K. Mizuno ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Magnetic Fields ◽  
Environmental Conditions ◽  
Vibration Isolator ◽  
Air Conditioners ◽  
Vibration Isolators ◽  
Large Size ◽  
Electron Microscopes

In recent years, with electron microscopes coming into wider use, their installation environments do not necessarily give their performance full play. Their environmental conditions include air-conditioners, magnetic fields, and vibrations. We report a jointly developed entirely new vibration isolator which is effective against the vibrations transmitted from the floor.Conventionally, large-sized vibration isolators which need the digging of a pit have been used. These vibration isolators, however, are large present problems of installation and maintenance because of their large-size.Thus, we intended to make a vibration isolator which1) eliminates the need for changing the installation room2) eliminates the need of maintenance and3) are compact in size and easily installable.

scholarly journals A Multiple and Multi-Level Substructure Method for the Dynamics of Complex Structures

2021 ◽  
Vol 11 (12) ◽  
pp. 5570
Author(s):  
Binbin Wang ◽  
Jingze Liu ◽  
Zhifu Cao ◽  
Dahai Zhang ◽  
Dong Jiang
Keyword(s):  
Structural Characteristics ◽  
Complex Structure ◽  
Complex Structures ◽  
System Matrix ◽  
Substructure Method ◽  
Residual Structure ◽  
The Matrix ◽  
Multi Level ◽  
Fixed Interface ◽  
Selection Of

Based on the fixed interface component mode synthesis, a multiple and multi-level substructure method for the modeling of complex structures is proposed in this paper. Firstly, the residual structure is selected according to the structural characteristics of the assembled complex structure. Secondly, according to the assembly relationship, the parts assembled with the residual structure are divided into a group of substructures, which are named the first-level substructure, the parts assembled with the first-level substructure are divided into a second-level substructure, and consequently the multi-level substructure model is established. Next, the substructures are dynamically condensed and assembled on the boundary of the residual structure. Finally, the substructure system matrix, which is replicated from the matrix of repeated physical geometry, is obtained by preserving the main modes and the constrained modes and the system matrix of the last level of the substructure is assembled to the upper level of the substructure, one level up, until it is assembled in the residual structure. In this paper, an assembly structure with three panels and a gear box is adopted to verify the method by simulation and a rotor is used to experimentally verify the method. The results show that the proposed multiple and multi-level substructure modeling method is not unique to the selection of residual structures, and different classification methods do not affect the calculation accuracy. The selection of 50% external nodes can further improve the analysis efficiency while ensuring the calculation accuracy.

Selection of Degrees of Freedom for Dynamic Analysis

1987 ◽  
Vol 109 (1) ◽  
pp. 65-69 ◽  
Author(s):  
K. W. Matta
Keyword(s):  
Finite Element ◽  
Dynamic Analysis ◽  
Degrees Of Freedom ◽  
General Purpose ◽  
Component Mode Synthesis ◽  
Complex Structures ◽  
Large Complex ◽  
Static Condensation ◽  
Basis Vectors ◽  
Selection Of

A technique for the selection of dynamic degrees of freedom (DDOF) of large, complex structures for dynamic analysis is described and the formulation of Ritz basis vectors for static condensation and component mode synthesis is presented. Generally, the selection of DDOF is left to the judgment of engineers. For large, complex structures, however, a danger of poor or improper selection of DDOF exists. An improper selection may result in singularity of the eigenvalue problem, or in missing some of the lower frequencies. This technique can be used to select the DDOF to reduce the size of large eigenproblems and to select the DDOF to eliminate the singularities of the assembled eigenproblem of component mode synthesis. The execution of this technique is discussed in this paper. Examples are given for using this technique in conjunction with a general purpose finite element computer program GENSAM[1].

scholarly journals Engineering the acyltransferase domain of epothilone polyketide synthase to alter the substrate specificity

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Huimin Wang ◽  
Junheng Liang ◽  
Qianwen Yue ◽  
Long Li ◽  
Yan Shi ◽  
...  
Keyword(s):  
Parental Strain ◽  
Assembly Line ◽  
Polyketide Synthase ◽  
Acyl Carrier Protein ◽  
Critical Factor ◽  
Catalytic Domains ◽  
Malonyl Coa ◽  
Epothilone D ◽  
Careful Design ◽  
Selection Of

Abstract Background Polyketide synthases (PKSs) include ketone synthase (KS), acyltransferase (AT) and acyl carrier protein (ACP) domains to catalyse the elongation of polyketide chains. Some PKSs also contain ketoreductase (KR), dehydratase (DH) and enoylreductase (ER) domains as modification domains. Insertion, deletion or substitution of the catalytic domains may lead to the production of novel polyketide derivatives or to the accumulation of desired products. Epothilones are 16-membered macrolides that have been used as anticancer drugs. The substrate promiscuity of the module 4 AT domain of the epothilone PKS (EPOAT4) results in production of epothilone mixtures; substitution of this domain may change the ratios of epothilones. In addition, there are two dormant domains in module 9 of the epothilone PKS. Removing these redundant domains to generate a simpler and more efficient assembly line is a desirable goal. Results The substitution of module 4 drastically diminished the activity of epothilone PKS. However, with careful design of the KS-AT linker and the post-AT linker, replacing EPOAT4 with EPOAT2, EPOAT6, EPOAT7 or EPOAT8 (specifically incorporating methylmalonyl-CoA (MMCoA)) significantly increased the ratio of epothilone D (4) to epothilone C (3) (the highest ratio of 4:3 = 4.6:1), whereas the ratio of 4:3 in the parental strain Schlegelella brevitalea 104-1 was 1.4:1. We also obtained three strains by swapping EPOAT4 with EPOAT3, EPOAT5, or EPOAT9, which specifically incorporate malonyl-CoA (MCoA). These strains produced only epothilone C, and the yield was increased by a factor of 1.8 compared to that of parental strain 104-1. Furthermore, mutations of five residues in the AT domain identified Ser310 as the critical factor for MMCoA recognition in EPOAT4. Then, the mutation of His308 to valine or tyrosine combined with the mutation of Phe310 to serine further altered the product ratios. At the same time, we successfully deleted the inactive module 9 DH and ER domains and fused the ΨKR domain with the KR domain through an ~ 25-residue linker to generate a productive and simplified epothilone PKS. Conclusions These results suggested that the substitution and deletion of catalytic domains effectively produces desirable compounds and that selection of the linkers between domains is crucial for maintaining intact PKS catalytic activity.

The effect of clam shell powder on kinetics of water absorption of jute epoxy composite

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hemalata Jena ◽  
Abinash Panigrahi
Keyword(s):  
Water Absorption ◽  
Environmental Conditions ◽  
Epoxy Composite ◽  
Jute Fibre ◽  
Content Type ◽  
Clam Shell ◽  
New Class ◽  
Kinetics Of ◽  
Shell Powder ◽  
Marine Waste

Purpose Here, attempts have been made to explore the possible use of Marine waste as filler materials into the bio-fibre composites. Clam shell is a type of marine waste which belongs to the class of Bivalvia. It is mainly made of aragonite crystalline polymorphs. This paper aims to develop a new class of natural fibre composite in which jute fibre as reinforcement, epoxy as matrix and clam shell, as particulate microsphere filler. The study investigates the effects of different amounts of clam shell powder on the kinetics of water absorption of jute fibre-reinforced epoxy composite. Two different environmental conditions at room temperature, i.e. distilled water and seawater, are collected for this purpose. Moisture absorption reduces when clam shell is added to the jute-epoxy composite. The curve of water absorption of jute-epoxy composites with filler loading at both environmental conditions follows as Fickian behaviour. Design/methodology/approach Hand lay-up technique to fabricate the composite – Experimental observation Findings The incorporation of Clam shell filler in jute epoxy composite modified the water absorption property of the composite. Hence the present marine waste is an potential filler in jute fibre reinforced polymer composite. Originality/value The paper demonstrates a new class hybrid composite material which uses a marine waste as important phase in the bio-fibre-reinforced composite. It is a new work submitted for original research paper.

Endless skies and open seas – how birds and fish navigate

Neuroforum ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Lisa Spiecker ◽  
Bo Leberecht ◽  
Corinna Langebrake ◽  
Malien Laurien ◽  
Shambhavi Rajendra Apte ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Magnetic Fields ◽  
Home Range ◽  
Environmental Conditions ◽  
Geomagnetic Field ◽  
Visual Cues ◽  
Quantum Mechanical ◽  
The Sun ◽  
Seasonal Migrations ◽  
Research Questions

Abstract Every year, billions of animals leave their home range and start seasonal migrations in order to find more favorable resources and to escape harsh environmental conditions. These round trips often span thousands of kilometers. To successfully navigate along their route, animals rely on various external references. While landmarks and celestial cues like stars or the sun are easy to imagine as guidance on these journeys, using the geomagnetic field for orientation is more elusive. The geomagnetic field is an omnipresent cue, which can be sensed and relied upon by many animals, even when visual cues are sparse. How magnetic fields can be perceived seems to vary between birds and fish. While birds seem to use a mechanism based on the quantum mechanical properties of electron spins, fish may have evolved a compass similar in its function to the technical devises developed by humans. How these mechanisms work precisely and how they are integrated are research questions addressed in SFB 1372.

Optimal Offloading Configuration of Spread-Moored FPSOs

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Steven M. Wilkerson ◽  
Satish Nagarajaiah
Keyword(s):  
Environmental Conditions ◽  
Main Tool ◽  
Design Parameters ◽  
Optimization Approach ◽  
Analysis Model ◽  
Simple Analysis ◽  
Formal Approach ◽  
Fine Tune ◽  
Formal Optimization ◽  
Selection Of

As the oil offloading operations of floating production storage and offloading (FPSO) units become more routine, the desire grows to increase the availability for offloading and thus decrease production downtime. Experience with these operations is the main tool available to increase the efficiency of this aspect of deepwater production. However, it is clear that a formal optimization approach can help to fine tune design parameters so that not only is availability increased but the significance of each design parameter can be better understood. The key issue is to define the environmental conditions under which the vessels involved in offloading are able to maintain position. By this, we reduce the notion of availability to a set of operating criteria, which can or cannot be met for a particular set of environmental conditions. The actual operating criteria such as relative vessel heading depend on selection of design parameters, such as the direction and magnitude of external force applied by thrusters or tugs. In the earliest offloading operations, engineering judgment was used to determine the feasibility of offloading at a particular time. For example, if wind and current were not expected to exceed a 1year return period, offloading may be considered safe. This approach can be both conservative and unconservative, depending on the nuances of the particular environmental conditions. This study will propose a formal approach to choosing the design parameters that optimize the availability of a FPSO for offloading. A simple analysis model will be employed so that optimization can be performed quickly using a robust second order method. The proposed analysis model will be compared to model test data to demonstrate its agreement with the more complex system.

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