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

From Agribusiness to Food Democracy: Comparative Study on Agricultural Policy and Organic Farming in France and in Japan

Food and agriculture are main fields of human sciences. This paper elucidates changes in food and agriculture that have progressed in France and in Japan during the 20th century and presents some attempts to create a new agri-food system. Agribusiness has developed as a branch of industry since the beginning of the 20th century. After the invention of agricultural machinery, it invented chemical fertilizer and pesticide, and genetically modified crops from the 1980s. Such technologies now strongly affect agriculture worldwide and in Japan. Contrary to this type of agriculture is a type promoted by the French government and the European Union commission, which established new agricultural policies in the 1990s. These policies reformulate the fundamental idea of agriculture: Agriculture is not a purely economic activity, but a multi-functional activity that must be regarded as the core factor of environmental protection, local community maintenance, and local economic revitalization. From this perspective, the EU and France have provided financial support and a path to rapid growth of organic farming. The ratio of the organic farmland in 2016 was 21.9% in Austria, 18.2% in Sweden, and 14.5% in Italy. More interesting is the case of France, where the ratio of organic farming was only 1.9% in 2007, but where it has advanced rapidly to 3.6% in 2011, and 6.6% in 2016.By contrast, the proportion of Japan remains extremely low: only 0.1% in 2007 and 0.2% in 2011. The reasons are multiple, but apparently include failure of government agricultural reform policy, indifference of Japan Agricultural Cooperatives which profit from agrichemical sales, and lax ethics of farmers opposed to drastic changes in agriculture. However, governmental policy is not the unique factor for the promotion of organic farming. Some farmer and consumer activities have also made great contributions to the progress of organic farming. Furthermore, such activities are developing rapidly also in Japan. These activities have common features such as relationships based on producer-consumer trust, active involvement, disclosure of information related to production, and self-determination of producers and consumers in deciding what to produce and eat. These features are common with those of democracy. This is the reason we qualify these practices as “food democracy”. Based on concrete cases, this paper is aimed at showing the future of agriculture and food systems by examining the possibilities and limits of these practices

Racialization and discourses of “privileges” in the Middle Ages: Jews, “Gypsies”, and Kawaramono

The dominant contention in the sociology of racialization asserts race as a modern Western construction. However, we lack studies that juxtapose the experiences in the Trans-Atlantic with the Trans-Pacific. This article, by examining the social conditions experienced by Jews in Spain, the “Gypsies” in Romania, and the Kawaramono in Japan in the Middle Ages, claims that the racialization had already begun before European colonization. It points out a variety of parallel patterns of marginalization and racialization, including but not limited to, “monopolization” of economic activities, an ambiguous relationship with the ruling class, and the discourses of “privileges.” My examination can contribute to understanding global trends of racism and the backlash against minoritized groups associated with the mythical discourses of “privileges” facing us all in the twenty-first century

Relationship between Microstructure and Magnetic Domain Structure of Nd-Fe-B Melt-Spun Ribbon Magnets

The relation between the microstructure, observed using an electron probe microanalyzer, and the domain structure, observed using a Kerr microscope, was established to evaluate the effects of hot rolling and the addition of Ti-C on the c-axis orientation and the magnetization process of hot-rolled Nd-Fe-B-Ti-C melt-spun ribbons. The addition of Ti-C promotes the c-axis orientation and high coercivity in the ribbons. Elemental mapping suggests a uniform elemental distribution; however, an uneven distribution of Ti was observed in an enlarged grain with Ti-enriched points inside the grain. The reversal domains that nucleated at the Ti-enriched point inside the grain cause low coercivity