217 research outputs found
Enhancement of non-resonant dielectric cloaks using anisotropic composites
Cloaking techniques conceal objects by controlling the flow of
electromagnetic waves to minimize scattering. Herein, the effectiveness of
homogenized anisotropic materials in non-resonant dielectric multilayer
cloaking is studied. Because existing multilayer cloaking by isotropic
materials can be regarded as homogenous anisotropic cloaking from a macroscopic
view, anisotropic materials can be efficiently designed through optimization of
their physical properties. Anisotropic properties can be realized in two-phase
composites if the physical properties of the material are within appropriate
bounds. The optimized anisotropic physical properties are identified by a
numerical optimization technique based on a full-wave simulation using the
finite element method. The cloaking performance measured by the total
scattering width is improved by about 2.8% and 25% in eight- and three-layer
cylindrical cloaking materials, respectively, compared with multilayer cloaking
by isotropic materials. In all cloaking examples, the optimized microstructures
of the two-phase composites are identified as the simple lamination of two
materials, which maximizes the anisotropy. The same performance as published
for eight-layer cloaking by isotropic materials is achieved by three-layer
cloaking using the anisotropic material. Cloaking with an approximately 50%
reduction of total scattering width is achieved even in an octagonal object.
Since the cloaking effect can be realized using just a few layers of the
laminated anisotropic dielectric composite, this may have an advantage in the
mass production of cloaking devices.Comment: 15 pages, 11 figure
Porous composite with negative thermal expansion obtained by photopolymer additive manufacturing
Additive manufacturing (AM) could be a novel method of fabricating composite
and porous materials having various effective performances based on mechanisms
of their internal geometries. Materials fabricated by AM could rapidly be used
in industrial application since they could easily be embedded in the target
part employing the same AM process used for the bulk material. Furthermore,
multi-material AM has greater potential than usual single-material AM in
producing materials with effective properties. Negative thermal expansion is a
representative effective material property realized by designing a composite
made of two materials with different coefficients of thermal expansion. In this
study, we developed a porous composite having planar negative thermal expansion
by employing multi-material photopolymer AM. After measurement of the physical
properties of bulk photopolymers, the internal geometry was designed by
topology optimization, which is the most effective structural optimization in
terms of both minimizing thermal stress and maximizing stiffness. The designed
structure was converted to a three-dimensional STL model, which is a native
digital format of AM, and assembled as a test piece. The thermal expansions of
the specimens were measured using a laser scanning dilatometer. The test pieces
clearly showed negative thermal expansion around room temperature.Comment: 11 pages, 4 figure
An Evaluation of Cutting Edge and Machinability of Inclined Planetary Motion Milling for Difficult-to-cut Materials
AbstractRecently, the applications of difficult-to-cut materials (e.g. CFRP and titanium alloy) are increasing in the aviation and automotive industries. Conventional drilling tools occur burr and/or delamination on their materials. The inclined planetary motion milling consists of two independent spindle motions which are tool rotation and revolution. Eccentricity of the tool rotation axis is realized by inclination of few degrees from revolution axis. The movement of eccentric mechanism can be reduced by comparison with that of the orbital drilling. The inclined planetary motion milling reduces inertial vibration and decreases cutting force. According to the geometrical cutting principle, it can be decreased delamination and burr of their materials, comparing to orbital drilling. In the study, the authors revaluated optimum cutting condition for titanium alloy by use of the experimental design and carried out its repeatability test. And the authors developed on measurement and evaluation method for cutting edge profiles and examined the comprehensive discussion of the relationship among change to cutting edge wear and surface texture and circularity on drilling hole, tool rotation torque after based on the practical drilling experiments
1-DiazoÂnaphthalen-2(1H)-one
The molÂecule of the title compound, C10H6N2O, is nearly planar [maximum deviation = 0.030 (1) Å]. The CN2 moiety is almost linear, with a C—N—N angle of 175.50 (14)°. A single interÂmolecular C—H⋯O hydrogen bond is observed in the crystal structure. A π–π interÂaction is also observed with the shortest distance being 3.6832 (12) Å between the the centroids of the six-membered rings
Is Ethereum Proof of Stake Sustainable? Considering from the Perspective of Competition Among Smart Contract Platforms
Since the Merge update upon which Ethereum transitioned to Proof of Stake, it
has been touted that it resulted in lower power consumption and increased
security. However, even if that is the case, can this state be sustained?
In this paper, we focus on the potential impact of competition with other
smart contract platforms on the price of Ethereum's native currency, Ether
(ETH), thereby raising questions about the safety and sustainability
purportedly brought about by the design of Proof of Stake.Comment: 30 pages, 1 figur
Unprecedented formation of η4-(vinylketene)iron complexes from η4-(diene)iron complexes and aromatic compounds in the presence of a Lewis acid
A novel and unprecedented formation of η4-(vinylketene)iron complexes from η4-(diene)iron complexes is described herein. Treatment of η4-(diene)iron complexes with a Lewis acid such as GaCl3 or AlCl3 in the presence of aromatic compounds under a CO atmosphere affords η4-(vinylketene)iron complexes via electrophilic aromatic substitution
Pd-catalyzed Cyclization of Terminal Alkynes using Diazonaphthoquinones: Synthesis of Naphtho[1,2-b]furans
Naphtho[1,2-b] furans were synthesized via a Pd-catalyzed reaction of diazonaphthoquinones and terminal alkynes in the presence of CuI and diisopropylamine. This method was then successfully applied to the synthesis of natural product, furomollugin
Selective Transesterification of 2,2,2-Trifluoroethyl Phosphates: Synthesis of Mixed Unsymmetrical Phosphates
A selective transesterification starting with tris(2,2,2-trifluoroethyl) phosphate has been developed. This method involves a three-step substitution for 2,2,2-trifluoroethoxy groups and enables the facile synthesis of mixed unsymmetric phosphate triesters from three different alcohols. The substitution of the trifluoroethoxy group at the phosphorus proceeds selectively in the presence of DBU or lithium alkoxides. This method can be applied for the preparation of phospholipids
Design methodology using topology optimization for anti- vibration reinforcement of generators in a ship’s engine room
Structural optimization for reinforcing the anti-vibration characteristics of the generators in the engine room of a ship is presented. To improve the vibration characteristics of the structures, topology optimization methods can be effective because they can optimize the fundamental characteristics of the structure with their ability to change the topology of the target structure. Topology optimization is used to improve the characteristics of the anti-vibration reinforcement of the generators in the engine room. First, an experimentally observed vibration phenomenon is simulated using the finite element method for frequency response problems. Next, the objective function used in topology optimization is set as the dynamic work done by the load based on the energy equilibrium of the structural vibration. The optimization problem is then constructed by adding the volume constraint. Finally, based on finite element analysis and the optimization problem, topology optimization is performed on several vibration cases to improve their performance and reduce weight.This work was supported by the JSPS KAKENHI Grant Numbers 24360356 and 25820422
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