Chiba Institute of Technology

About: Chiba Institute of Technology is a education organization based out in Narashino, Japan. It is known for research contribution in the topics: RNA & Magnet. The organization has 2663 authors who have published 4999 publications receiving 56870 citations. The organization is also known as: Chiba kōgyō daigaku & Kōa Institute of Technology.

Static compression of porous dust aggregates

Abstract: Context. In protoplanetary disks, dust grains coagulate with each other and grow to form aggregates. While these aggregates are growing by coagulation, their filling factor φ decreases to φ ≪ 1; however, comets, the remnants of these early planetesimals, have φ ~ 0.1. Thus, static compression of porous dust aggregates is important in planetesimal formation. However, the static compressive strength has only been investigated for relatively high-density aggregates (φ > 0.1).Aims. We investigate and find the compressive strength of highly porous aggregates (φ ≪ 1).Methods. We performed three-dimensional N -body simulations of aggregate compression with a particle-particle interaction model. We introduced a new method of static compression: the periodic boundary condition was adopted, and the boundaries move with low speed to get closer. The dust aggregate is compressed uniformly and isotropically by themselves over the periodic boundaries.Results. We empirically derive a formula of the compressive strength of highly porous aggregates (φ ≪ 1). We check the validity of the compressive strength formula for wide ranges of numerical parameters, such as the size of initial aggregates, the boundary speed, the normal damping force, and material. We also compare our results to the previous studies of static compression in the relatively high-density region (φ > 0.1) and confirm that our results consistently connect to those in the high-density region. The compressive strength formula is also derived analytically.

Nanocomposites based on poly(butylene adipate‐co‐terephthalate) and montmorillonite

Abstract: Nanocomposites based on biodegradable poly(butylene adipate-co-terephthalate) (PBAT) and layered silicates were prepared by the melt intercalation method. Nonmodified montmorillonite (MMT) and organo-modified MMTs (DA-M, ODA-M, and LEA-M) by the protonated ammonium cations of dodecylamine, octadecylamine, and N-lauryldiethanolamine, respectively, were used as the layered silicates. The comparison of interlayer spacing between clay and PBAT composites with inorganic content 3 wt % measured by X-ray diffraction (XRD) revealed the formation of intercalated nanocomposites in DA-M and LEA-M. In case of PBAT/ODA-M (3 wt %), no clear peak related to interlayer spacing was observed. From morphological studies using transmission electron microscopy, the ODA-M was found to be finely and homogeneously dispersed in the matrix polymer, indicating the formation of exfoliated nanocomposite. When ODA-M content was increased, the XRD peak related to intercalated clay increased. Although the exfoliated ODA-M (3 wt %) nanocomposite showed a lower tensile modulus than the intercalated DA-M and LEA-M (3 wt %) composites, the PBAT/ODA-M composite with inorganic content 5 wt % showed the highest tensile modulus, strength, and elongation at break among the PBAT composites with inorganic content 5 wt %. Their tensile properties are discussed in relation to the degree of crystallinity of the injection molded samples. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 386–392, 2005

Cohesion of amorphous silica spheres: toward a better understanding of the coagulation growth of silicate dust aggregates

Abstract: Adhesion forces between submicrometer-sized silicate grains play a crucial role in the formation of silicate dust agglomerates, rocky planetesimals, and terrestrial planets. The surface energy of silicate dust particles is the key to their adhesion and rolling forces in a theoretical model based on the contact mechanics. Here we revisit the cohesion of amorphous silica spheres by compiling available data on the surface energy for hydrophilic amorphous silica in various circumstances. It turned out that the surface energy for hydrophilic amorphous silica in a vacuum is a factor of 10 higher than previously assumed. Therefore, the previous theoretical models underestimated the critical velocity for the sticking of amorphous silica spheres, as well as the rolling friction forces between them. With the most plausible value of the surface energy for amorphous silica spheres, theoretical models based on the contact mechanics are in harmony with laboratory experiments. Consequently, we conclude that silicate grains with a radius of $0.1~\mu$m could grow to planetesimals via coagulation in a protoplanetary disk. We argue that the coagulation growth of silicate grains in a molecular cloud is advanced either by organic mantles rather than icy mantles or, if there are no mantles, by nanometer-sized grain radius.

Robust 3D SLAM with a stereo camera based on an edge-point ICP algorithm

Abstract: Most vision-based SLAM systems utilize corner-like features, and may be unstable in non-textured environments where only a few corner features can be extracted. To cope with this problem, we employ edge points to perform SLAM with a stereo camera. The edge-point based SLAM is applicable to non-textured environments since plenty of edge points can be obtained even from a small number of lines. The proposed method estimates camera poses and builds detailed 3D maps robustly by aligning edge points between frames using the ICP algorithm. In indoor experiments, the method successfully built detailed 3D maps even under noisy condition.