Preparation of poly(2-pyridone-3,5-diyl)s with –(CH2)4–SO3M (M = H or Na) side chains

Poly(2-pyridone-3,5-diyl)s with –(CH₂)₄–SO₃M (M = H or Na) side chains have been prepared by nickel-complex promoted dehalogenative polycondensation. A composite film of the polymer with –(CH₂)₄–SO₃H side chains and poly(vinyl alcohol) showed a proton conductivity of 1.5 × 10^?1 S cm^?1 at 80 °C and 95% humidity. A copolymer with pyridine showed a high stability against oxidation by a Fenton reagent.     

Antimutagenic and α-glucosidase inhibitory effects of constituents from Kaempferia parviflora

The dichloromethane extract and ethyl acetate soluble fraction of Kaempferia parviflora showed antimutagenicity and α-glucosidase inhibitory activity. 7-Methoxyflavones were the major constituents of both extracts and demonstrated antimutagenic activity. In particular, 5,7-dimethoxyflavone (IC₅₀ = 0.40 nmol/plate), 5,3′-dihydroxy-3,7,4′-trimethoxyflavone (0.40 nmol/plate), 3,5,7-trimethoxyflavone (0.42 nmol/plate) and 5-hydroxy-7-methoxyflavone (0.47 nmol/plate) showed potent antimutagenic activity. The results of structure–activity relationship studies suggest that methylation of the 5-hydroxy group enhanced activity. On the other hand, increasing the number of methoxy groups on the B ring caused a reduction in activity. In the case of an α-glucosidase inhibitory effect, 5,7,3′,4′-tetramethoxyflavone exhibited the highest activity (IC₅₀ = 20.4 μM), followed by 5,7,4′-trimethoxyflavone (54.3 μM) and 3,5,7,3′,4′-pentamethoxyflavone (64.3 μM). The results suggest that the α-glucosidase inhibitory activity was enhanced by the methoxy groups at the 5-, 3′- and 4′-position and was reduced by the methoxy group at the 3-position.     

Anti‐windup algorithm with priority to proportional control output of speed PI controller for precision servo system

A robust servo system is important for performance improvement of motion control systems in several industry applications. Generally, a high‐speed positioning servo system consists of robust control systems with integrator, such as PI controller. The industrial servo system always has the limitation for the capacity of the actuator and power amplifier. An ordinary industrial position servo system often has to deal with the saturation of motor current and motor speed. It is difficult for the high‐speed positioning servo system to keep the robust position control against the saturation of motor current and motor speed. This is the case because an ordinary position servo system has a complicated control structure with many control loops. Hence, it sometimes has a large overshoot and an oscillated response due to the limitation of motor current and motor speed. In order to overcome this problem, this paper proposes a new robust high‐speed positioning servo system considering the saturation of torque current and motor speed. The experimental results show that the proposed robust high‐speed positioning servo system has quick and stable position response for the saturation of motor current and motor speed. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(3): 57–64, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20904     

A servo system of AC motor based on voltage modulation fitting for FPGA and consideration of voltage saturation

This paper proposes a space voltage vector modulation (SVM) method for a speed servo system to obtain a quick current response. The proposed SVM method shortens the control lag time of the conventional SVM inverter. In addition, this proposed method is easily implemented in hardware using an FPGA (Field Programmable Gate Array) because the proposed SVM equations are transformed into expressions that hardly need multiplication. By using the proposed SVM method, the servo system realizes quick and stable current control with wide bandwidth. Moreover, by using PI controllers considering the voltage saturation and the torque limiter to the speed servo system, the servo system carries out stable speed control on voltage saturation. Both the proposed SVM method and the PI controllers considering voltage saturation are applied to the speed servo system of a vector controlled induction motor. The effectiveness of both the proposed SVM method and the PI controllers considering voltage saturation is verified by the experimental results. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(1): 60–68, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20989     

Electronic structures at organic heterojunctions of N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamin (NPB)-based organic light emitting diodes

Interface electronic structures of four-kinds of electron transporting or hole blocking organic materials (n-type) on a widely-used hole transporting material (p-type) in organic light emitting diodes (OLEDs), N,N′-bis (1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamin (NPB), were investigated by means of photoelectron spectroscopy (PES). 1,3-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (OXD-7) and 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) overlayers show continuous energy shift of each overlayer-derived spectral components and the vacuum level proportional to the thickness. This energy shift is ascribed to a spontaneous building up of the electrostatic potential within the organic layers (giant surface potential; GSP). The energy shift of the overlayers induced by GSP as well as the interface vacuum level shift are adequately taken into account to determine the actual energy barrier heights of the hole conduction levels at the heterojunctions. 4,4′-bis(9-carbazolyl)biphenyl (CBP) and p-bis(triphenylsilyl) benzene (UGH2) induce band bending in the NPB film which presumably results from charge transfer (CT) to the n-type materials from NPB. Despite absence of a practical vacuum level shift and thickness dependent shift of the overlayer-derived electronic states, the CT-derived energy shift of NPB reduces the actual energy barrier height with respect to the nominal barrier height being simply interpreted from PES spectra of a thick overlayer of each material. The energy level diagrams across these ‘n-on-p’ organic–organic heterojunctions were finely determined based on the above interpretation of the PES spectra.     

An Efficient Way to Assemble ZnS Nanobelts as Ultraviolet‐Light Sensors with Enhanced Photocurrent and Stability

Although there has been significant progress in the fabrication and performance optimization of one‐dimensional nanostructure‐based photodetectors, it is still a challenge to develop an effective and low‐cost device with high performance characteristics, such as a high photocurrent/dark‐current ratio, photocurrent stability, and fast time response. Herein an efficient and low‐cost method to achieve high‐performance ‘visible‐blind’ microscale ZnS nanobelt‐based ultraviolet (UV)‐light sensors without using a lithography technique, by increasing the nanobelt surface areas exposed to light, is reported. The devices exhibit about 750 times enhancement of a photocurrent compared with individual nanobelt‐based sensors and an ultrafast time response. The photocurrent stability and time response to UV‐light do not change significantly when a channel distance is altered from 2 to 100 µm or the sensor environment changes from air to vacuum and different measurement temperatures (60 and 150 °C). The photoelectrical behaviors can be recovered well after returning the measurement conditions to air and room temperature again. The low cost and high performance of the resultant ZnS nanobelt photodetectors guarantee their highest potential for visible‐blind UV‐light sensors working in the UV‐A band.     

Effect of counter materials on coefficients of friction of TiN coatings with preferred grain orientations

In order to investigate the effect of counter materials on the coefficients of friction of TiN coatings with preferred grain orientations, the coefficients of friction against six counter materials (ball) were measured. The ball materials were aluminum (A1050), stainless steel (SUS304, SUS440C), bearing steel (SUJ2), carburized steel (SWRM10), cemented tungsten carbide (WC-Co) and alumina (Al₂O₃). After tests, the worn flat surfaces of balls and the wear tracks of TiN coatings were analyzed by the electron probe micro analysis (EPMA) and the auger electron spectroscopy (AES) to observe the Ti oxide film on each ball material and the adhesion of ball materials to the TiN coatings. The Ti oxide film was observed on the worn flat surfaces of the ball materials and the ball materials did not adhere to the TiN coatings in case that the low coefficients of friction were obtained.     

Forced convective heat transfer in uniformly heated horizontal tubes (2nd report, theoretical study)

Effects of buoyancy force on forced laminar convective heat transfer in a uniformly heated horizontal tube may not be neglected at large Re Ra. This 2nd report deals with a theoretical investigation of this problem on a fully developed laminar flow and compares the results with experimental results reported in the 1st report.

In order to back up assumptions made in the following analysis, patterns of secondary flow due to buoyancy are observed in flow visualization experiments. An approximate solution for very large Re Ra is obtained. Nusselt numbers are shown as a function of Re Ra and Pr and are shown to be in fairly good agreement with experimental results on air. Resistance coefficients are also obtained as a function of Re Ra and Pr.