A power decoupling control method for an isolated single‐phase AC‐to‐DC converter based on a high‐frequency cycloconverter

This paper proposes a new power decoupling method for a high‐frequency cycloconverter which converts the single‐phase line‐frequency ac input to the high‐frequency ac output directly. The cycloconverter consists of two half‐bridge inverters, two input filter capacitors, and a series‐resonant circuit. The proposed power decoupling method stores the input power ripple at double the line frequency in the filter capacitors. Therefore, the proposed method achieves a unity power factor in ac input and a constant current amplitude in the high‐frequency output without any additional switching device or energy storage element. This paper theoretically discusses the principle and operating performance of the proposed power decoupling method, and the viability is confirmed by using an experimental isolated ac‐to‐dc converter based on the high‐frequency cycloconverter. As a result, the proposed power decoupling method effectively improved the displacement power factor in the line current to more than 0.99 and reduced the output voltage ripple to 4% without any electrolytic capacitor.     

One‐dimensional polymer nanofiber arrays with high aspect ratio obtained by thermal nanoimprint method

Polymer surface modification that mimicks natural behaviors has been a subject of great interest. Fabrication of polymer nanofiber arrays with various applications has been studied intensively. Avoidance of chemical solvents, reduction of processing time, improvement of the nanofiber size distribution and aspect ratios, and improvement of reproducibility have been sought for industrial value creation. This study examines an alternative fabrication methods for polymer nanofiber arrays using a combination of anodic aluminum oxide (AAO) nanoporous template and thermal nanoimprinting lithography for simple, precise processing. Based on those results, nanofiber arrays were fabricated with 40‐µm‐thick film and 50–100 nm fiber diameter polystyrene (PS) and polypropylene (PP). For this study, 50‐nm diameter PS nanofibers with 50 µm maximum length and a maximum aspect ratio of 1,000 were produced in addition to PP nanofibers having 130 µm maximum length and an aspect ratio of 2,600. The nanofiber lengths were affected considerably by molten polymer flow related to imprint processing conditions, polymer properties, AAO properties, and surface wettability between AAO and molten polymers. Moreover, AAO nanoconfinement demonstrated molecular orientation alignment of polymers that affect thermal properties, crystallinity, and mechanical properties of the obtained polymer nanofiber arrays. POLYM. ENG. SCI., 57:214–223, 2017. © 2016 Society of Plastics Engineers     

Isolation of methyl syringate as a specific aflatoxin production inhibitor from the essential oil of Betula alba and aflatoxin production inhibitory activities of its related compounds

Methyl syringate was isolated from the essential oil of Betula alba as an aflatoxin production inhibitor. It inhibited aflatoxin production of Aspergillus parasiticus and Aspergillus flavus with IC₅₀ values of 0.9 and 0.8 mM, respectively, without significantly inhibiting fungal growth. Methyl syringate reduced mRNA levels of genes (aflR, pksA, and omtA) encoding proteins required for aflatoxin biosynthesis. Methyl gallate, methyl 3,4,5-trimethoxybenzoate, and methyl 3-O-methylgallate inhibited both aflatoxin production and fungal growth of A. parasiticus and A. flavus. However, their acids and syringic acid did not inhibit aflatoxin production and growth of A. parasiticus significantly, although gallic acid inhibited aflatoxin production of A. flavus with selectivity. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of methyl syringate was much weaker than that of gallic acid. These results showed that methyl syringate has a unique inhibitory activity toward aflatoxin production with a different mode of action from that of gallic acid.     

Comparison of Oil‐in‐Water Emulsion between Ultrasonic Irradiation and Mechanical Stirring

To compare oil‐in‐water emulsification behaviors between ultrasonic irradiation and impeller stirring, experiments and calculation by mathematical models were performed. For ultrasonic irradiation, the peak diameter of dispersed oil droplets decreased with an increase in input power and reductions in ultrasonic frequency, ratio of dispersed volume, and interfacial tension. For mechanical stirring, it declined with higher mechanical rotation speed. The results calculated by the mathematical models approximately agreed with the experiments. Ultrasonic irradiation was better than mechanical stirring by an impeller for producing a fine emulsion at higher supplied energy rate into liquid, whereas the tendency was inverse for a rough emulsion at lower input energy rate.     

A differential mobility analyzer and a Faraday cup electrometer for operation at 200–930 Pa pressure

We have developed a differential mobility analyzer (DMA) based on the DMA devised by Seto et al. (1997) and a Faraday cup electrometer for measurement of nanometer-sized particles at a few hundred Pa and examined the operating characteristics of the DMA using the tandem DMA technique. The tandem DMA calibration establishes that the DMA successfully classifies particles in the 200–930 Pa pressure range. It was also found that the transfer function of the DMA follows the triangular transfer function and the resolution of the DMA is close to that given for an ideal case. As a standard of a minimum pressure that may be probed with the present DMA system, 400 Pa is estimated when the DMA operates with a 3 nlmin⁻¹ sheath flow and a 1 nlmin⁻¹ aerosol flow rate.     

Spectroscopic study of lactonic rhodamine B immobilised on polytetrafluoroethylene porous film

Rhodamine B (RB) is frequently used in chemical sensors, where the sensing principle depends on its structural changes to lactone (L), zwitterion (Z), and cation (C) forms in response to the local environment. Compared to the Z- and C-forms, stabilising the L-form in matrices is difficult because of the required low environmental polarity. In this study, we report a simple and easy method to stabilise the L-form of RB on the surface of a polytetrafluoroethylene porous film (p-PTFE), in which the film is dipped in an ethanol solution containing RB and dried. This phenomenon was not observed on polyethylene film and cellulose filter paper in RB solutions. Furthermore, a chemical stability test for colourless RB/p-PTFE samples was conducted by exposing these samples to a humid environment. The test result indicated that, with an increase in the environmental humidity, the equilibrium shifted from the L-form to the Z-form of RB immobilised on the p-PTFE film.     

Improvement of steady-state performance for discrete-valued input control with an integrator utilizing feedback control of integrated value of input

In this study, we considered the regulator problem for discrete-valued input control with an integrator. In some cases, the state does not converge to the origin in the discrete-valued input control when the plant possesses an integrator. Therefore, a method that adds minor feedback control to the integrated value of the input was proposed. However, the effect of the feedback control of the integrated value of the input was not theoretically interpreted, and the feedback gain for the state of the integrated value of the input was designed with trial and error. Herein, we clarify the effect of feedback control on the integrated value of the input. Furthermore, we reveal that the trade-off between the steady-state and transient performances is controlled by one parameter, that is, the feedback gain for the integrated value of the input.