Preparation and properties of TiC micro-coils and micro-tubes by the vapour phase titanizing of carbon micro-coils

TiC micro-coils and micro-tubes were prepared by the vapour phase titanizing of the regular carbon micro-coils, and the preparation conditions and some properties were examined. The carbon coils were titanized from the surface of the fiber to the core with full preservation of the coiling morphology to form TiC micro-coils or micro-tubes. The bulk electrical resistivity was 0.1–0.01 ·cm depending on the titanized rate and the bulk density. The specific surface area of the source carbon coils (about 100 m²/g) was significantly decreased with increasing reaction temperature and reaction time. The tensile strength of a TiC micro-tube was 660 MPa. The attenuation ratio against an electromagnetic wave of the TiC micro-tubes (30 wt % in epoxy resin) was about 90% (dB = –10) for 800–900 MHz.     

Preparation of carbon microcoils by catalytic methane hot-wire CVD process

Three-dimensional (3D) double-helix carbon microcoils (CMCs) were synthesized by the catalytic pyrolysis of methane using Ni catalyst in various hot-wire CVD processes. The most effective process is: using preheating method, in which methane was preheated at 1500 °C in a upper reaction tube by a hot wire, and chemical vapor deposition of carbon then occurred at 700-750 °C in a lower reaction tube, where CMCs were synthesized. The growth morphologies and microstructure were examined and compared with the conventional CMCs grown by acetylene catalytic pyrolysis.     

Effective input order of dynamics learning tree

In this paper, we discuss about the learning performance of dynamics learning tree (DLT) while mainly focusing on the implementation on robot arms. We propose an input-order-designing method for DLT. DLT has been applied to the modeling of boat, vehicle, and humanoid robot. However, the relationship between the input order and the performance of DLT has not been investigated. In the proposed method, a developer is able to design an effective input order intuitively. The proposed method was validated in the model learning tasks on a simulated robot manipulator, a real robot manipulator, and a simulated vehicle. The first/second manipulator was equipped with flexible arm/finger joints that made uncertainty around the trajectories of manipulated objects. In all of the cases, the proposed method improved the performance of DLT.     

Formation of an Environmental Barrier Coating Using DC–RF Hybrid Plasma

The characteristics of an Al₂O₃ coating on a Nb or Mo substrate using a direct current-radio frequency induction (DC-RF) thermal plasma of Ar-H₂ were studied. A porous and crystallographically stable coating with highly preferred orientation of {110} planes of α-Al₂O₃ crystals was obtained. The preferred orientation was strongly dependent on the diameter of the introduced Al₂O₃ powder. The formation mechanism of the preferred orientation of the coating is explained by accumulation of charged clusters on the substrate. The coating prepared by this procedure revealed the superior capability of protecting the substrate against high-temperature oxidation.     

Sonographic patterns of radiolucent gall-bladder stones for predicting successful shock-wave lithotripsy

The aim of this study was to examine whether the sonographic patterns of gallstones are useful for predicting the outcome of piezoelectric shock-wave lithotripsy. Pretreatment analysis of gallstones based on our sonographic classification was conducted on 115 patients with radiolucent solitary stones of 10-30 mm in diameter, monitored for at least a year after the first lithotripsy. All stones were categorized as type I with gradual attenuation of echoes: type Ia, the stone echo appears as a full moon, usually accompanied by comet-tail artifacts beyond the stone itself (n = 55); type Ib, the stone echo showing the anterior half of the stone, seen as a half moon (n = 29); and type Ic, the stone echo seen as a crescent (n = 31). The most complete fragmentation, 'pulverization', was achieved at a significantly higher rate for type Ia (51%) than for type Ib (14%, P < 0.005) and type Ic (7%, P < 0.0001) after significantly fewer shock-waves (vs type Ib, P < 0.01; vs type Ic, P < 0.0001). The rate of complete clearance at 12 months after lithotripsy was significantly greater for type Ia (91%) than for type Ib (62%, P < 0.01) and type Ic (45%, P < 0.0001). Comparison of the sonographic and computed tomography (CT) patterns of stones revealed a close relationship between the two: the vast majority (98%) of type Ia showed the iso- or hypo-dense, and the majority (90%) of type Ic the rimmed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Morphology and microstructure of spring-like carbon micro-coils/nano-coils prepared by catalytic pyrolysis of acetylene using Fe-containing alloy catalysts

Three-dimensional (3D) spring-like carbon nano-coils were obtained in high purity (nearly 100%) and high yield (20%) by the catalytic pyrolysis of acetylene at 750-790 °C using an Fe-based catalyst; 54Fe-38Cr-4Mn-4Mo or 71Fe-18Cr-8Ni-3Mo (SUS513). The morphologies and microstructure were examined in detail, and the growth mechanism is also discussed. The diameter of carbon fiber, from which the carbon nano-coils was formed, was 50-200 nm, the coil diameter 100-1000 nm, and the coil pitch 10-500 nm. The nano-coils were generally grown by a mono-directional growth mode, and laces with various morphologies were very commonly observed on the surface. It was observed that the spring-like carbon nano-coils are actually composed of two fused nano-coils.     

Analysis of dependence of short-channel effects in double-gate MOSFETs on channel thickness

A systematic study of the dependence of short-channel effects (SCEs) on the channel thickness (Tch) of double-gate MOSFETs revealed that there is a particular range of Tch in which SCEs are significantly degraded compared to those of conventional planar MOSFETs. This phenomenon was found to originate from the electric field penetrating the channel region from the drain due to the disappearance of a neutral region in the channel. This dependence of this phenomenon on device parameters such as the channel doping concentration (Nc), the equivalent oxide thickness (EOT) and the gate length (Lg) was examined. The degradation of SCEs due to an inappropriate Tch was found to become more significant as Nc and Lg are reduced.     

Kinetics of Solid-State Reactive Diffusion in the (Ni-Cr)/Sn System

The kinetics of solid-state reactive diffusion in the (Ni-Cr)/Sn system was experimentally observed to examine the influence of the addition of Cr into Ni on the growth behavior of compounds at the interconnection between Sn-based solder and multilayer Au/Ni/Cu conductor during energization heating. In the experiment, Sn/(Ni-Cr)/Sn diffusion couples with Cr mol fractions of y?=?0.051 to 0.282 were isothermally annealed at temperatures of T?=?433?K to 473?K for various times up to t?=?3167?h. During annealing at T?=?453?K to 473?K, a two-phase compound layer with rather uniform thickness consisting of Ni₃Sn₄ and CrSn₂ is produced at the initial (Ni-Cr)/Sn interface in the diffusion couple, where the compound layer indicates a periodic lamellar microstructure parallel to the initial interface typically for y?=?0.150. On the other hand, at T?=?433?K, Ni₃Sn₄ and CrSn₂ are formed also as a two-phase layer for y?=?0.117 but as granular particles for y?=?0.051 and y?=?0.150 to 0.282. The mean thickness l of the compound layer is proportional to a power function of the annealing time t. Since the exponent n of the power function takes values of 0.58 to 0.85, interface reaction as well as diffusion contribute to the rate-controlling process for compound growth. The overall growth rate of the compound layer reaches a maximum value at y?=?0.12 within the experimental annealing times. Thus, the compound growth at the interconnection is remarkably accelerated by the addition of Cr with y?=?0.12 into Ni in the multilayer Au/Ni/Cu conductor, though the addition of Cr improves the heat resistance of Ni.