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

Formation experiments of CO2 hydrate chimney in a pressure cell

Experimental investigations were conducted to understand the formation process of CO_2 hydrate the chimney structure by using a gas bubble emission technique in water within a pressure cell. The detailed process was video-recorded and analyzed to study the initiation and growth behavior of hydrate chimney while the cell pressure was increased and gas supply rate decreased gradually with time. In the initial stage of chimney growth, a hydrate crystal started to form in a cup shape at the gas nozzle and ascended together with gas bubbles due to mechanical weakness of the hydrate/nozzle contact. Growth of hydrate chimney occurred with supercooling of 3K(overpressure of 0.60MPa) or more, and continued until the top end was closed completely by hydrate

GLOVEBOX DISMANTLEMENT AND EQUIPMENT PROTECTION IN CONTAMINATED ENVIRONMENTS

ABSTRACT It has been revealed from the experiences of Decontamination and Decommissioning (D&D) activities that even a small improvement in performance can result in significant risk reduction and cost savings. For example, Race Scan Ear Mic System, which was originally developed for communications between racecar drivers and crews in loud environments, has been successfully applied to D&D work and proved to enhance worker safety and communications. Glovebox dismantlement is an important and costly process in D&D activities of nuclear facilities. Adequate decontamination and size reduction of the gloveboxes are especially important in this activity because they have the potential to reduce risks and costs significantly. This paper presents some simple approaches to support D&D tasks and discusses their potential advantages. Examples discussed include: • Repeated shear wiping of large pipes and ducts • Application of thin layers on radiological counters for uninterrupted use • Partial use of robotics for glovebox dismantling The paper also discusses schematics for protecting equipment interiors and/or glovebox inner surfaces from contamination, which may result in significant savings and waste minimization upon future dismantlement. Examples discussed include: • Smart coating for contamination prevention • Protecting equipment by geometrically simple cove

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

Quantification of Modified Tyrosines in Healthy and Diabetic Human Urine using Liquid Chromatography/Tandem Mass Spectrometry

The quantification of urinary oxidized tyrosines, dityrosine (DiY), nitrotyrosine (NY), bromotyrosine (BrY), and dibromotyrosine (DiBrY), was accomplished by quadruple liquid chromatography-tandem mass spectrometry (LC/MS/MS). The sample was partially purified by solid phase extraction, and was then applied to the LC/MS/MS using multiple-reaction monitoring (MRM) methods. The analysis for the DiY quantification was done first. The residual samples were further butylated with n-butanol/HCl, and the other modified tyrosines were then quantified with isotopic dilution methods. MRM peaks of the modified tyrosines (DiY, NY, BrY, and DiBrY) from human urine were measured and the elution times coincided with the authentic and isotopic standards. The amounts of modified tyrosines in healthy human urine (n = 23) were 8.8 ± 0.6 (DiY), 1.4 ± 0.4 (NY), 3.8 ± 0.3 (BrY), and 0.7 ± 0.1 (DiBrY) µmol/mol of creatinine, respectively. A comparison of the modified tyrosines with urinary 8-oxo-deoxyguanosine, pentosidine, and Nε-(hexanoyl)lysine was also performed. Almost all products, except for NY, showed good correlations with each other. The amounts of the modified tyrosines (NY, BrY, and DiBrY) in the diabetic urine were higher than those in the urine from healthy people

Transcriptional suppression of nephrin in podocytes by macrophages: Roles of inflammatory cytokines and involvement of the PI3K/Akt pathway

AbstractExpression of nephrin, a crucial component of the glomerular slit diaphragm, is downregulated in patients with proteinuric glomerular diseases. Using conditionally immortalized reporter podocytes, we found that bystander macrophages as well as macrophage-derived cytokines IL-1β and TNF-α markedly suppressed activity of the nephrin gene promoter in podocytes. The cytokine-initiated repression was reversible, observed on both basal and inducible expression, independent of Wilms’ tumor suppressor WT1, and caused in part via activation of the phosphatidylinositol-3-kinase/Akt pathway. These results indicated a novel mechanism by which activated macrophages participate in the induction of proteinuria in glomerular diseases

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

Topology optimization of damping material for reducing resonance response based on complex dynamic compliance

In this research, we propose a new objective function for optimizing damping materials to reduce the resonance peak response in the frequency response problem, which cannot be achieved using existing criteria. The dynamic compliance in the frequency response problem is formulated as the scalar product of the conjugate transpose of the amplitude vector and the force vector of the loading nodes. The proposed objective function methodology is implemented using the common solid isotropic material with penalization (SIMP) method for topology optimization. The optimization problem is formulated as maximizing the complex part of the proposed complex dynamic compliance under a volume constraint. 2D and 3D numerical examples of optimizing the distribution of the damping material on the host structure are provided to illustrate the validity and utility of the proposed methodology. In these numerical studies, the proposed objective function worked well for reducing the response peak in both lower and upper excitation frequencies around the resonance. By adjusting the excitation frequency, multi-resonance peak reduction may be achieved with a single frequency excitation optimization.This research was partially supported by JSPS KAKENHI Grant Numbers 25820422 and 25630436