An Investigation of Microstructure and Phase Transformation Behavior of Cu40Zn-1.0 wt.% Ti Brass Via Powder Metallurgy

The effects of Ti addition on phase transformation, precipitation behavior, and microhardness response of Cu40Zn brass were investigated at elevated heat treatment (HT) temperatures using the powder metallurgy method. The volume fraction of the α phase increased with the elevated temperatures, which showed an equal value as that of the β phase at 400 °C, and reached a maximum value of 55.9% at 500 °C. The solid solubility of Ti in Cu40Zn brass matrix decreased as the HT temperature increased. Supersaturated Ti showed high chemical potential for precipitates' reaction in Cu40Zn brass. Lower HT temperature retained higher Ti solid solubility and fine precipitates. The precipitates presented in form of Cu₂TiZn intermetallic compound, distributing uniformly in brass matrix which suppressed the phase and grain growth. After HT at elevated temperature, the precipitates coalesced, grew coarser, and segregated at the primary particle boundaries. The microhardness of the BS40-1.0Ti compact was primarily not only dependent on the solid solubility of Ti, but also dependent on the phase volume fraction of the α and β phases.     

Reduction of cyclic speed change using a bandpass filter for compressor PMSM sine‐wave position sensorless drives

Position sensorless vector control has been applied to compressor drive systems using an IPMSM to realize higher efficiency. In this paper, reduction control of cyclic speed change is proposed in order to achieve improved performance, including low vibration and low acoustic noise. Designing a speed estimator by using an adaptive observer with a wide frequency band, the fundamental frequency component of the cyclic speed change is calculated by a bandpass filter. The proposed compensation method recognizing the fundamental component can reduce the cyclic speed change to an acceptable level. The principle of the compensation method is presented along with experimental results. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(4): 75–84, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20765     

Experimental proof of voltage‐current waveform sensor output of resin molded type for measurement of power factor and harmonics in general power distribution system

We have proposed a voltage‐current sensor of resin molded type for measurement of the power factor and harmonics. To understand the characteristics of the conventional prototype sensor and the problems of its practical use, we conducted a finite element analysis. Problems involving the cost and practical usage of the sensor were identified. Therefore, we have redesigned the prototype sensor, incorporating the current sensor designed on the basis of the FEM and a ready‐made voltage sensor. In this paper, we describe feasibility field experiments with the present sensor in a practical 6.6‐kV distribution system and show that the sensor can measure the power factor and harmonics of horizontal and vertical power line systems successfully. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(3): 1–10, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21213     

Size and surface modification of amorphous silica particles determine their effects on the activity of human CYP3A4 in vitro

Because of their useful chemical and physical properties, nanomaterials are widely used around the world - for example, as additives in food and medicines - and such uses are expected to become more prevalent in the future. Therefore, collecting information about the effects of nanomaterials on metabolic enzymes is important. Here, we examined the effects of amorphous silica particles with various sizes and surface modifications on cytochrome P450 3A4 (CYP3A4) activity by means of two different in vitro assays. Silica nanoparticles with diameters of 30 and 70 nm (nSP30 and nSP70, respectively) tended to inhibit CYP3A4 activity in human liver microsomes (HLMs), but the inhibitory activity of both types of nanoparticles was decreased by carboxyl modification. In contrast, amine-modified nSP70 activated CYP3A4 activity. In HepG2 cells, nSP30 inhibited CYP3A4 activity more strongly than the larger silica particles did. Taken together, these results suggest that the size and surface characteristics of the silica particles determined their effects on CYP3A4 activity and that it may be possible to develop silica particles that do not have undesirable effects on metabolic enzymes by altering their size and surface characteristics.     

Fundamental experiments for the development of high-performance cold plates in a feasability study on space solar power system

To realize a concept of solar power satellite with high power generation, it is a promising method to transfer the power by laser beam using active mirror type amplifiers where cooling of the laser material accepting highly condensed sunray is inevitable. To remove high heat flux density from a large area, a structure of cold plate consisted of two parallel plates is devised and the effective liquid supply directly to the bottom of flattened bubbles due to nucleate boiling is realized by the auxiliary liquid feeder. The critical heat flux is increased by more than 1.5 times from that without the additional liquid supply. The technology can be applied not only to space but widely to the development of high-performance cold plates employed on ground.     

Effect of surface alteration of hydride titanium washers on discharge characteristics of plasma gun

Several titanium (Ti) hydride washers containing different amounts of both TiN and an oxide compound (Ox) are tested for the source of hydrogen (H⁺) plasmas. According to the different-looking surfaces of the washers of Ti hydride, considerable change in the required discharge voltage is observed. Slightly larger probe currents are also measured from plasmas produced with the washers having the smallest amounts of TiN and Ox, which suggests the existence of more H⁺ ions in the formed plasmas. Once apparent grain coarsening appears on the surface of Ti hydride washers at the temperature around 950°C, no successful electric discharge occurred.     

Magnetic Susceptibilities of MgCu2O3 and Doped MgCu2O3 with Zn and Co

The magnetic susceptibility of MgCu ₂ O ₃ powder was measured between 0.2 K and 800 K. The results above TN can be fitted by a Curie–Weiss law plus a one-dimensional (1 — d) antiferromagnetic susceptibility and a constant susceptibility. Below TN the magnetic susceptibility has the large contribution from the paramagnetic impurity of free Cu ²⁺ ions in the compound. When we add Zn ²⁺ ions in the compound the Néel temperature decreases. On the other hand the Co doped MgCu ₂ O ₃ enhance the Néel temperature. Only a small number of Co ions changes the magnetic property of MgCu ₂ O ₃ drastically.     

Production and deposition of CN radicals to produce amorphous carbon nitride films with high [N]/([N] + [C]) ratio

The dissociative excitation reaction of BrCN with the microwave discharge flow of Ar was studied on the basis of the laser-induced fluorescence (LIF) spectroscopy and electrostatic-probe analysis. The CN(A²Π_i − X²Σ⁺), 4-0, 5-1, and 7-2 bands were observed by LIF, from which the density of CN(X²Σ⁺) was evaluated as 9.9 × 10¹⁷ m^− 3. The intensities of the LIF spectra of the ³P₁–³P₂ and ³P₂–³P₂ transitions of Ar were negligibly weak under the steady-state condition introducing BrCN. Therefore, the contribution of Ar(³P₂) was negligible to the dissociation process. A kinetic analysis based on the densities of CN(X²Σ⁺) and electrons revealed that the dissociation proceeds almost uniquely via the charge transfer from Ar⁺ followed by the ion–electron recombination and that the dominant quenching process of CN(X²Σ⁺) was reaction with BrCN.     

Experimental investigation of solar-assisted transcritical CO2 Rankine cycle for summer and winter conditions from exergetic point of view

This study deals with energy and exergy analysis of the experimental solar-assisted Rankine cycle working with an environmentally friendly working fluid transcritical CO₂. The experimental system consists of evacuated solar collectors, a heat recovery system, condenser, a pump, and an expansion valve to simulate the realistic turbine operation. The system was designed for electricity production and the heat supply for various applications. The experiments were made funder typical winter and summer days to evaluate seasonal system performance in Kyoto, Japan. According to the obtained results, the turbine capacity was calculated as 0.118 kW and 0.177 kW for winter and summer seasons. From the exergetic point of view, solar collectors were found to be the major contributor to the total exergy destruction with 96.32% for summer and 93.58% for the winter season. Therefore, the efforts should be focused on the collectors. Thus, any attempt for improving the system performance should be focused on solar collectors first. Furthermore, the exergetic efficiency of the overall system was calculated as 7.63% for the winter season and 4.08% for the summer season. As a result, the utilization of CO₂ in the energy conversion cycle can be sustainably developed and extended by providing a glimpse into the carbon-free clean energy future.     

Effects of shutter transients in molecular beam epitaxy

We have studied the effects of shutter transients (STs) in molecular beam epitaxy (MBE). Two series of samples were grown by MBE and evaluated by X-ray diffraction (XRD) and X-ray reflectivity (XRR) measurements. The effects of STs were evaluated by growth rate (GR) analysis using a combination of growth time (GT) and thickness evaluated by XRD and XRR measurements. We revealed two opposite effects of STs: (1) overshoot of GR and (2) increase in GR with GT and subsequent saturation. Each effect was consistent with the previous studies; however, the previous studies showed no relationships between these two effects. By considering closing time of the shutter, the two opposite effects were well understood.