Examination of vibration control of linear oscillatory actuator

Linear oscillatory actuators (LOAs) are widely used in linear motor shavers, electric toothbrushes, and mobile phone vibrators as high‐speed oscillatory driving devices. The maximum amplitude of the motor is obtained at a resonant frequency that is determined from the spring constant and the mass of the motor. However, there is a problem with these actuators: the amplitude decreases sharply when the driving frequency differs from the resonant frequency in a mechanical vibration system with minimal damping. In this paper, we propose a control method for the resonant frequency in which the thrust, which shows the characteristics of a spring, is generated on the basis of the displacement of the mover and the damping factor, in which the thrust, which shows the characteristics of damping, is generated based on the velocity of the mover. The proposed method assures that the resonant frequency always corresponds to the driving frequency and that rapid changes in the amplitude are avoided. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(4): 55–62, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21172     

Nucleation and Avalanche of 4He Crystals in Aerogel

Dynamical transition of ⁴He crystals in aerogel was reported recently (Nomura et al. Phys. Rev. Lett. 101:175703, 2008). Bare aerogel, which was placed in the bulk ⁴He crystals, was used in the report. ⁴He crystals inside the aerogel grew via creep at high temperatures and via avalanche at low temperatures owing to the competition between thermal fluctuation and quenched disorder. Crystal-liquid interface advanced from the edge to inside of the aerogel. Crystal has a greater density than liquid so that the extra mass has to be transported in the crystallization process. It is not known how the mass is transported in the aerogel. To find a clue to this issue, we did an experiment with aerogel in a glass tube so that the aerogel had contact with the bulk on only one surface. In this case, a similar dynamical transition was observed at low temperatures. In the avalanche region, however, ⁴He crystals did not grow from the outer surface of the aerogel but nucleated at various sites inside the aerogel. This means that crystallization in aerogel does not occur by the forced invasion of ⁴He crystal but by a process of the bulk crystal once being melted and transported to increase the pressure of the liquid in the aerogel. Thus, a mass transport mechanisms for the crystallization has been revealed by this observation.     

Sugar response of boronic acid-substituted azobenzene dye-modified polymer

We synthesized a boronic acid-appended azobenzene dye (BA) and attached it to poly(ethyleneimine) (polyBA) for studying its sugar response. The addition of d-glucose induced a significant change in the UV–visible absorption spectra of the polyBA solution. The binding constants for d-glucose (K_glu) and d-fructose (K_fru) were calculated to be 54 M^? 1 and 110 M^? 1, respectively. The selectivity for d-glucose was higher in polyBA as compared with that of monomeric BA (K_glu = 1.2 M^? 1, K_fru = 17 M^? 1). We also fabricated multilayered films composed of polyBA and polyanions {poly(vinyl sulfate) (PVS), carboxymethylcellulose (CMC)} using a layer-by-layer deposition technique. In (PVS/polyBA)₁₀ films, the affinity for d-glucose was relatively low (K_glu = 1.7 M^? 1, K_fru = 28 M^? 1). In contrast, (CMC/polyBA)₅ films showed a high affinity for d-glucose (K_glu = 18 M^? 1, K_fru = 42 M^? 1). The loosely packed structure of the (CMC/polyBA)₅ film and the suitable chemical structures of CMC probably led to a high affinity for d-glucose.     

Estimation of sensitivity coefficients of core characteristics based on reduced-order modeling using sensitivity matrix of assembly characteristics

We propose an estimation method of sensitivity coefficients of core neutronics parameters based on a multi-level reduced-order modeling approach. The idea is to use lower-level models to identify the dominant input parameter variations, constrained to the so-called active subspace, which are employed to determine the sensitivity coefficients of the core neutronic parameters. In our implementation, the lower-level model is represented by two-dimensional assembly calculations, which are employed in the preparation of the few-group cross-sections for core-wide calculations. The active subspace basis is estimated using the singular value decomposition of sensitivity matrices of assembly neutronics parameters. In numerical verification calculation, sensitivity coefficients of core characteristics for a typical three-loop PWR equilibrium-cycle are estimated using the proposed method and the direct method. Comparison of these two results shows that the proposed method well reproduces the results obtained by the direct method with lower calculation costs. Through the verification calculations, applicability of the proposed method to practical light water reactor analysis is confirmed.     

Cs–Te corrosion depth dependence on distribution of chromium carbide precipitation in high chromium steel

In an attempt to investigate Cs–Te corrosion depth dependence on distribution of chromium carbide precipitation in high chromium steel, Cs–Te corrosion out-pile tests of two 9Cr steels with different distributions of chromium carbide were carried out at 975 K for 100 h, and their corrosion depths were compared. The corrosion is obviously more advanced in a specimen which has grain boundary carbide than in the one that does not. A considerable reason of the result is that the carbide distributed at grain boundaries promoted the corrosion reaction and the corrosion extended along the grain boundary. This is the first case in which the Cs–Te corrosion depth dependence on distribution of chromium carbide precipitation in Fe–Cr steel is clarified experimentally.     

High efficiency production of astaxanthin in an airlift photobioreactor

In photobioreactors, photosynthetic microorganisms are exposed to certain light/dark cycles caused by light intensity distribution and mixing inside the photobioreactor. In this study, Haematococcus pluvialis was cultivated in an airlift and a bubble column photobioreactor, and the cell growth and astaxanthin production were compared to clarify the effects of liquid circulation.     

Formation of Mg2Cu at low temperature in Mg/Cu super-laminate composites during initial hydrogenation

The formation mechanism of microstructures in Mg/Cu super-laminates composites (SLCs) fabricated by accumulative roll-bonding (ARB) during initial activation was investigated. It is revealed that Mg₂Cu can grow with sufficient growth rate at low temperatures (<453 K) in Mg/Cu SLCs. The growth of Mg₂Cu layers for short growth length is diffusion-controlled. The activation energies for layer growth process of Mg₂Cu layers in Mg/Cu SLCs are 107 ± 8 kJmol^?1 with acid cleaning prior to ARB and 103 ± 12 kJmol^?1 without acid cleaning prior to ARB, respectively, which are about 2/3 of those in MgCu diffusion couples. It is considered that the high density of lattice defects in Mg/Cu SLCs fabricated by ARB contributes the much lower activation energies for layer growth process of Mg₂Cu layers in Mg/Cu SLCs than in MgCu diffusion couples.     

Tadalafil Treatment of Mice with Fetal Growth Restriction and Preeclampsia Improves Placental mTOR Signaling

Fetal growth restriction (FGR) is a major cause of poor perinatal outcomes. Although several studies have been conducted to improve the prognosis of FGR in infants, no effective intrauterine treatment method has been established. This study aimed to use tadalafil, a phosphodiesterase 5 inhibitor (PDE5) inhibitor, as a novel intrauterine treatment and conducted several basic and clinical studies. The study investigated the effects of tadalafil on placental mTOR signaling. Tadalafil was administered to mice with L-NG-nitroarginine methyl ester (L-NAME)-induced FGR and associated preeclampsia (PE). Placental phosphorylated mTOR (p-mTOR) signaling was assessed by fluorescent immunohistochemical staining and Western blotting. The expression of p-mTOR was significantly decreased in mice with FGR on 13 days post coitum (d.p.c.) but recovered to the same level as that of the control on 17 d.p.c. following tadalafil treatment. The results were similar for 4E-binding protein 1 (4E-BP1) and S6 ribosomal (S6R) protein, which act downstream in the mTOR signaling pathway. We demonstrate that the tadalafil treatment of FGR in mice improved placental mTOR signaling to facilitate fetal growth. Our study provides the key mechanistic detail about the mode of action of tadalafil and thus would be helpful for future clinical studies on FGR.