Time-averaged aerodynamic forces acting on a hemisphere immersed in a turbulent boundary

The time-averaged pressure distribution over the surface of a hemisphere immersed in a fully developed turbulent boundary layer developing along a smooth, plane wall has been measured for a number of hemispheres of differing diameter d in order to establish the relationship between the aerodynamic force acting on such a hemisphere and the characteristics of the boundary layer. It is found that the drag coefficients defined by $\text{C}{}_{\mathrm{<mtext>D</mtext><mtext>\tau </mtext>}}\text{= D/(}\text{1}\text{2}\text{πu}{}_{\mathrm{\tau }}{}^2\text{A}$ may be expressed as a function of u_τd/ν alone in the range $\text{d/δ ? 1.0}$, where D is the pressure drag, u_τ the shear velocity, ν the kinematic viscosity, A denotes the area of the hemisphere projected onto a plane normal to the main flow direction, and δ is the boundary-layer thickness.     

Properties of hydroxyapatite prepared by the hydrolysis of tricalcium phosphate

Non-stoichiometric hydroxyapatite was prepared by the hydrolysis of α-tricalcium phosphate. The apatite was obtained as a powder and hardened with and without stirring during the hydrolysis. The apatite had a general formula, characteristic dehydration and pyrolysis behaviour similar to that of precipitated non-stoichiometric hydroxyapatite. In addition, it exhibited some new phenomena (i.e. thermal reaction between lattice H₂O and PO₄^3? above 473 K, formation of ESR centres above 473 K and disappearance at 873–973 K, and a slight weight loss at 873–973 K). Apatite particles were composed of aggregates of cylindrical rods or thin blades grown along the c-axis or {100} faces of apatite structure. Hardened apatite materials with various porosities above 55% and bulk densities below 1.4 g cm^?3 were obtained by using different water-soluble additives. The strength of the hardened materials was 20–500 kg cm^?2 in compression and 10–120 kg cm^?2 in bending. The strengths were improved at least two to three times by impregnating the hardened materials with methyl methacrylate polymer.     

High-density formation of Ge quantum dots on SiO2

We formed high-density Ge quantum dots (QDs) on an ultrathin SiO₂ layer by controlling the early stages of low-pressure chemical vapor deposition (LPCVD) with a germane gas (GeH₄) assisted by a remote plasma of pure H₂. We then characterized the electronic charged states of the QDs by an AFM/Kelvin probe technique. The formation of single crystalline Ge-QDs with an areal dot density of ∼2.0 × 10¹¹ cm⁻² was confirmed after examining the surface morphology and lattice by atomic force microscopy and transmission electron microscopy, respectively. It has been suggested that an increase in the flux of deposition precursors due to efficient decomposition of GeH₄ by a supply of hydrogen radicals and the dehydration reaction of surface OH bonds plays a role in nucleation of Ge-QDs on SiO₂. Surface passivation with hydrogen may also promote the surface migration of deposition precursors during LPCVD. The surface potential of the dots changed in a stepwise manner with respect to the tip bias due to multistep electron injection into and extraction from the Ge-QDs.     

Fabrication of a Au/Si nanocomposite structure by nanosecond pulsed laser irradiation

A gold/silicon nanocomposite structure (NCS) was formed on a Si(100) surface by nanosecond pulsed laser irradiation. The Au/Si NCS contained both Au nanoparticles (NPs) and Au-Si alloy layers. We report that the use of laser irradiation to form Au NPs comprises two competing processes: a top-down effect involving decomposition into smaller NPs and a bottom-up effect involving self-assembly or self-organization into larger NPs. The formation of the periodic structure involved self-organization, i.e., the bottom-up effect, and was observed in situ using a pulsed-laser-equipped high-voltage electron microscope. The NCS formed by laser irradiation can be controlled by adjusting the laser energy density and the number of laser pulses.     

Performance analysis of desiccant dehumidification systems driven by low-grade heat source

If a desiccant dehumidification system can be driven by a heat source whose temperature is below 50 °C, exhaust heat from devices such as fuel cells or air conditioners can be used as its heat source, thereby saving energy. Therefore, in this study, we used a previously validated simulation model to determine the minimum heat source temperature for driving a desiccant dehumidification system. We considered four desiccant dehumidification systems that can be driven by waste heat—conventional desiccant-type systems (wheel type and batch type with only desiccant), a system with a precooler, double-stage-type systems (a type with two desiccant wheels and a four-partition desiccant wheel type), and a batch-type system with an internal heat exchanger. We found that among these systems, the last system can be driven by the lowest heated air temperature—approximately 33 °C—which is considerably lower than that of the conventional system.     

Driving mechanism, design, fabrication process, and experiments of a cylindrical ultrasonic linear microactuator

A new type of cylindrical ultrasonic linear microactuator (CULMA) is introduced. The traveling wave generation condition in the stator is presented, which was confirmed using simulation and experimentation. The design and fabrication process to develop the stator is described. The stator was successfully fabricated using metallic glass and a sputtering method, and the vibration of the prototype matched the simulation results. When the driving frequency is at 626 kHz, the traveling wave in the stator was observed. Loaded with a pipe slider, the slider movement was experimentally demonstrated and the motion measured with 26 mm/s in peak speed. This paper presents a traveling wave generation method in a CULMA which would also available in other microactuators or MEMS-scale ones.     

Critical light scattering in4He near the gas-liquid critical point

Scattered intensities of light were measured near the gas-liquid critical point of ⁴ He at scattering angles of 30, 60, and 90° as functions of the reduced temperature =|T–T _c |/T _c along the critical isochore (T>T _c ) and the coexistence curve (T>T _c ). The temperature range was 3×10 ^–5 <<1.5×10 ^–2 . Critical exponents and coefficients describing divergence of the generalized susceptibility and the correlation length are obtained as (T>T _c )=1.31±0.02, v(T>T _c )=0.66±0.02, ₀ (T>T _c )=4.2±0.6 Å, (T>T _c )=1.32±0.02, v(T>T _c )=0.68±0.02, _± (T>T _c )=2.6±0.7 Å, =0.06±0.06(T>T _c ), 0.05±0.05(T>T _c ), and ₀(T>T _c )/x_± (T>T _c )=3.6±0.4. It is pointed out that the quantal nature of ⁴ He has remarkable influence on the critical behavior of ⁴ He in the above-mentioned temperature region.     

Low-loss and wide-band double-mode surface acoustic wave filters using pitch-modulated interdigital transducers and reflectors

This paper proposes use of pitch-modulated interdigital transducers (IDTs) and reflectors for the realization of low-loss and wideband longitudinally coupled double-mode surface acoustic wave (DMS) filters. This technique offers drastic improvement of the device performances through the introduction of a sufficient number of degrees of freedom in the DMS filter design. Namely, the pass-band becomes wide and flat, and insertion loss can be reduced through the suppression of the bulk acoustic wave (BAW) scattering. First, it is shown how the BAW scattering loss can be reduced by the use of the pitch-modulated structure. The DMS filter with this structure is designed so that the frequency response becomes similar to that of the filter with the conventional unmodulated structure, and device performances are compared both theoretically and experimentally. It then is demonstrated how the total device performances are improved by the use of this technology when the device is designed optimally for given specifications. Adding to the reduced bulk wave scattering loss, various distinctive features offer drastic improvement of total device performances.     

Active contour model-based segmentation algorithm for medical robots recognition

In this paper, an identifying and classifying algorithm is proposed to solve the problem of recognizing objects accurately and effectively. First, via image preprocessing, initial images are obtained via denoising, smoothness, and image erosion. Then, we use granularity analysis and morphology methods to recognize the objects. For small objects identification and to analyze the objects, we calculate four characteristics of each cell: area, roundness, rectangle factor, and elongation. Finally, we segment the cells using the modified active contour method. In addition, we apply chromatic features to recognize the blood cancer cells. The algorithm is tested on multiple collected clinical cases of blood cell images. The results prove that the algorithm is valid and efficient when recognizing blood cancer cells and has relatively high accuracy rates for identification and classification. The experimental results also certificate the effectiveness of the proposed method for extracting precise, continuous edges with limited human intervention, especially for images with neighboring or overlapping blood cells. In addition, the results of the experiments show that this algorithm can accelerate the detection velocity.     

Improvement of pressure distribution to arbitrary geometry with boundary condition represented by polygons in particle method

The boundary condition represented by polygons in the moving particle semi‐implicit method can accurately represent geometries and treat complex geometry with high efficiency. However, inaccurate wall contribution to the Poisson's equation leads to drastic numerical oscillation. To address this issue, in this research, we analyzed the problems of the Poisson's equation used in the boundary condition represented by polygons. The new Poisson's equation is proposed based on the improved source term (Tanaka and Masunaga, Trans Jpn Soc Comput Eng Sci, 2008). The asymmetric gradient model (Khayyer and Gotoh, Coastal Engineering Journal, 2008) is also adopted to further suppress the numerical oscillation of fluid particles. The proposed method can dramatically improve the pressure distribution to arbitrary geometry in three dimensions and keep the efficiency. Four examples including the hydrostatic simulation, dam break simulation, and two complex geometries are verified to show the general applicability of the proposed method. Copyright © 2017 John Wiley & Sons, Ltd.