Analysis of minority carrier diffusion length in SiC toward high quality epitaxial growth

Homoepitaxy of 4H-SiC grown by a horizontal hot-wall chemical vapor deposition and the minority carrier diffusion length were studied. With the addition of HCl during the etching and the epitaxy, an optimum growth window on the C face became wide. Minority carrier diffusion length in SiC epilayers was evaluated by a line-scanning electron-beam-induced current method.     

Observation of Remanent Vortices Attached to Rough Boundaries in Superfluid 4He

We report the study on remanent vortices attached to rough boundaries in superfluid ⁴He after the turbulent transition. We used 2.6 µm vibrating wires with smooth surfaces and rough surfaces, a cover box and slow cooling method, in order to investigate the effect of surface roughness on the condition and the number of vortices attached to a wire. The responses of the wire with smooth surfaces show large hysteresis at the turbulent transition. This result indicates that remanent vortices attached between the wire and surrounding boundaries cause turbulence. At first sweep of driving force of the wire with rough surfaces, we also observed hysteresis as large as the case of the smooth wire: at the other sweeps, however, small hysteresis was observed. These results indicate that once turbulence is generated at a wire velocity during first sweep, vortex lines newly attach between rough surfaces of the wire, which easily cause turbulence at a low wire velocity. Therefore, we conclude that a smooth wire can reduce the number of vortices attached to a wire.     

Application of in situ loop-mediated isothermal amplification method for detection of Salmonella in foods

In situ loop-mediated isothermal amplification (in situ LAMP) as a novel technique for detection of food-borne pathogens, has been successfully applied to detect Salmonella in artificially contaminated eggshells. Escherichia coli C600 was used as a negative control in specificity experiment. The sensitivity of the in situ LAMP assay was confirmed by the test in serial 10-fold dilutions of Salmonella cells, and the detection limit of this method may reach 1 CFU/cm² on eggshells. Compared with traditional culture methods and PCR-based methods, the in situ LAMP assay is advantageous on rapidity, high specificity, less time consumption and ease in operation. This is the first study carried out to apply the in situ LAMP method in practical food-borne pathogens detection. The results indicate that this method has great potential for use in food safety laboratories.     

Ethanol demand under the flex-fuel technology regime in Brazil

This paper analyzes the characteristics of ethanol demand in the context of fuel mix diversification in Brazil. Currently, ethanol is the most important gasoline additive and alternative fuel consumed in Brazil and is responsible there for profound changes in the dynamics of fuel consumption. The diffusion of flex-fuel vehicles in Brazil symbolizes a new stage of ethanol expansion and is a central component of the increasing demand for fuel. Accordingly, we evaluate ethanol demand in Brazil following the introduction of flex-fuel vehicles using a cointegration approach and autoregressive distributed lag bounds tests over the period 2003–2010. The evidences confirm that during the last decade, ethanol has strengthened its position as both an independent fuel and a substitute for gasoline. There is also evidence that growth in the Brazilian automobile fleet based on flex-fuel technology is a major driving factor of long-run ethanol demand. Further, the dynamics of gasohol (mandatory blend of gasoline and ethanol) and ethanol prices operate in a symmetric manner over ethanol demand, thereby evidencing the increasing substitutability between these alternative fuels.     

High‐resolution and high‐brightness full‐colour “Silicon Display” for augmented and mixed reality

High‐brightness micro‐LED display bonded onto silicon backplane has been successfully demonstrated. The 0.38‐inch full‐colour active matrix LED microdisplay system consists of 352 × 198 pixels. Each pixel is 24 μm square composed of red, green, and blue (RGB) subpixels corresponding to a pixel resolution of 1053 ppi. Quantum‐dot materials are formed on III‐nitride blue micro‐LED array to convert blue light into red and green for full‐colour operation. We have confirmed that this microdisplay, which we call “Silicon Display” has wide colour gamut exceeding 120% of sRGB. We describe the advantage of this colour‐converting approach for the full‐colour micro‐LEDs. Progress toward higher resolution is also described. Brightness of more than 30 000 cd/m² has been confirmed at a driving current density of 4 A/cm² for 3000 ppi blue monochrome micro‐LED prepared for full‐colour Silicon Display. We believe our “Silicon Display” is ideally suited for near‐to‐eye displays for augmented and mixed reality.     

Structure and mechanical properties of a Fe90Zr10 amorphous alloy

The structure of a Fe₉₀Zr₁₀ amorphous alloy was investigated by means of small angle X-ray scattering as well as large-angle diffraction measurements. For as-quenched specimens, SAXS was found to be relatively weak, but spread over a wide scattering angle. After quantitative analysis, it was concluded that a compositional fluctuation occurs on a fine scale of about 0.6 nm. When the specimen was heat treated below the crystallization temperature, the amorphous structure changed to a more stable dual structure consisting of pure iron and a structure similar to Fe₃Zr. By prolonged heat treatment, the iron-rich regions crystallized initially from the amorphous state. An apparent correspondence was found to exist between the changes in the amorphous structure and in the mechanical properties. The microscopic phase separation within the amorphous state resulted in an increase of ultimate tensile strength and fracture toughness. The deterioration of mechanical properties was suggested to be attributed to the gradual crystallization of iron-rich regions.     

H Robust servo problem with H∞ norm constraint

A robust servo problem with an H-infinity norm constraint is investigated based on the LMI (Linear Matrix Inequality) approach to the H-infinity control problem. The following results are obtained. (1) A necessary and sufficient condition for the existence of an H-infinity controller with robust tracking property is derived. It consists of the following two indepent conditions: (i) the existence of an H-infinity controller; (ii) a boundary constraint at the reference mode. (2) If there exists an H-infinity controller with robust tracking performance, there exists one whose order equals the sum of an H-infinity controller and the internal model.     

Numerical study on the effects of linear protrusion on flow-induced carriage excitation force in hard disk drives

The positioning accuracy of magnetic heads needs to be improved to increase the recording capacity of hard disk drives. In our previous study, experimental results confirmed that the head-positioning error could be decreased by attaching linear protrusions on the leading edge of the carriage arms. However, the mechanism underlying the phenomenon has not been elucidated. In the present research, we evaluated the effect of leading-edge protrusions on the flow-induced carriage excitation force using computational fluid dynamics (CFD) analysis and the Hilbert–Huang transform (HHT). We prepared two carriage-arm models, with and without linear protrusions, on the leading edges of the arm, and performed the CFD analyses. Subsequently, we conducted a frequency analysis by applying HHT to the simulated disturbance torque time-series of each carriage-arm model and compared the results. Our results show that the leading-edge protrusions decrease the disturbance torque due to the flow fluctuation between the arm and disk and in the wake flow, although the low-frequency disturbance torque due to the pulsatile flow can be deteriorated.

     

An Improved Approximation Algorithm for the Traveling Tournament Problem

This paper describes the traveling tournament problem, a well-known benchmark problem in the field of tournament timetabling. We propose an approximation algorithm for the traveling tournament problem with the constraints such that both the number of consecutive away games and that of consecutive home games are at most k. When k≤5, the approximation ratio of the proposed algorithm is bounded by (2k−1)/k+O(k/n) where n denotes the number of teams; when k>5, the ratio is bounded by (5k−7)/(2k)+O(k/n). For k=3, the most investigated case of the traveling tournament problem to date, the approximation ratio of the proposed algorithm is 5/3+O(1/n); this is better than the previous approximation algorithm proposed for k=3, whose approximation ratio is 2+O(1/n).     

Motion control of wearable-type walking support system based on the spring-mass model

Many systems and control methods have been proposed as mobility supports for the physically disabled and elderly individuals. In this research, we focus on a wearable-type system that supports the elderly with their walking. Different from typical control methods of wearable-type walking support systems, we propose a simple control method based on the spring–mass model. As a walking aid that does not require additional motions, such as sit-to-stand, this simple system is beneficial for two reasons. First, it reduces the calculation cost of deriving the support joint torque of the user; second, the wearable device hardware can be simply constructed from low-power actuators and springs rather than high-power actuators. In stance phase support mode, our motion control method compensates for a part of the force applied to the upper body as a leg muscle support. During the swing phase, walking is supported by a trajectory-following method using the impedance control as well as the spring–mass model. The proposed methods are applied to a prototype of a wearable-type walking support system, and evaluated in a series of experiments on human subjects.