The True Origin of Ductile Fracture in Aluminum Alloys

It has generally been assumed that metals usually fail as a result of microvoid nucleation induced by particle fracture. Here, we concentrate on high-density micropores filled with hydrogen in aluminum, existence of which has been largely overlooked until quite recently. These micropores exhibit premature growth under external loading, thereby inducing ductile fracture, whereas the particle fracture mechanism operates only incidentally. Conclusive evidence of a micropore mechanism is provided by the observation of an instantaneous release of gas at failure. We can therefore conclude that the growth of micropores dominates ductile fracture. Since the material we used has a standard pore density, we can assume that an identical fracture mechanism operates in other aluminum alloys. This finding suggests that intense heat treatment, which is generally believed to enhance the mechanical properties through homogenization, may have entirely the opposite effect. This revelation will have a major impact on the engineering design of metals.     

Properties of SiAlON powder phosphors for white LEDs

Three kinds of Eu²⁺-doped oxynitride powder phosphors, including green β-SiAlON, yellow Ca-α-SiAlON and newly developed orange Ca-α-SiAlON were prepared by gas pressure sintering, which emit the fluorescent light with emission peak at 540 nm, 585 nm and 597 nm, respectively. Emission intensity more than 90% can be kept in the range of temperature from 30 °C to 200 °C. Emission characteristics are stable after long-term exposure testing for 6000 h at temperature of 85 °C and in humidity of 85%. A white LED device composed of a blue LED chip, β-SiAlON and orange Ca-α-SiAlON phosphors exhibits a modest colour rendering index of 72.     

Study on high thermal conductivity of mesogenic epoxy resin with spherulite structure

The microstructure of a mesogen-containing epoxy resin that exhibits high thermal conductivity (0.33 W/m K) was investigated by observations of the scanning electron microscope (SEM) and the polarized optical microscope (POM). It was found that there are many spherulite structures formed in the resin. We supposed that the reason for the high heat-conductivity obtained in the resin is ascribed to the existence of the spherulite morphology where highly ordered lamellar structures aggregated. The argument was strongly supported by preparing the resin films with size-changed spherulites which are induced by changing the initial curing temperature. The result revealed that the thermal conductivity increased with the increase in spherulite size. On the other hand, we have developed the spherulite size in the resin from 10 to 80 μm in diameter that resulted in a greatly improved thermal conductivity of up to 1.16 W/m K in the highest value. This study may provide a useful method to improve the thermal conductivities of mesogenic resins themselves by producing spherulite structures.     

An in‐cell capacitive touch sensor integrated in an LTPS WSVGA TFT‐LCD

This paper discusses an In‐cell capacitive touch sensor and its integration in an LTPS TFT‐LCD with 7‐inch screen size and WSVGA resolution. The operation of the newly developed sensor is based on capacitive coupling between user's finger and the detection electrode on the TFT substrate, and is purely capacitive. The sensors and the sensor driver circuits have been integrated in the TFT substrate of the prototype TFT‐LCD using LTPS technology. The prototype having 256x150 sensors shows advantages such as smooth operation with no touch force, high position accuracy, multi‐touch (10 or more), a thin and light LCD module, high display quality, and thus is suitable for various applications such as cell‐phones, smart‐phones, mobile‐PCs, and automotive‐use displays.     

Thermal aging characteristics of insulation paper in mineral oil in overloaded operation of transformers

A sudden capacity increase in demand during the summer peak, or in contingencies such as malfunctioning transformers, may cause an overload in normal transformers. In this paper, on the basis of overloaded transformer operation in distribution substations, thermal aging testing in oil was carried out under various overload patterns, such as short‐term overload and long‐term overload, but with the winding insulation paper's lifespan loss kept constant. From the results, various characteristics, such as the mean degree of polymerization and production of furfural and (CO₂ +CO), and their effects on the lifespan loss of the insulation paper, were obtained. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 182(2): 1–8, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21292     

Charge transfer-induced horizontal orientation of organic molecules near transition metal oxide surfaces

The influence of charge transfer from organic molecules to transition metal oxide on molecular orientation characteristics of N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) was investigated. Absorption peaks originating from neutral and cationic states of α-NPD increased in absorbance when α-NPD was deposited on metal oxides (MoO₂, MoO₃, and WO₃). Photoluminescence from this α-NPD was directional normal to the film plane. These results indicate that α-NPD is horizontally oriented near the metal oxide surfaces so that charge transfer from α-NPD to metal oxide occurs efficiently. Such horizontal orientation of α-NPD enhanced current density of hole-only α-NPD devices because of improvement of wave function overlap and charge transfer degree at the metal oxide/α-NPD interface.     

Reassuring evacuation guidance with mobile terminal communication and RFID system in absence of power supply

In this paper, we propose a method which aims to allow people inside a building to evacuate when a disaster occurs. In particular, it is very difficult for them to evacuate safely in blackout conditions with servers down. In the proposed method, passive RFID tags are placed on the walls of the building and each evacuee carries a mobile terminal that is battery‐powered and equipped with an RFID reader‐writer. This device finds evacuation routes based on the information from passive RFID tags touched by the evacuee. The method identifies safety of evacuation routes from the movement of people who have evacuated safely. Mobile terminal communication and RFID tags achieve sharing of information on safe routes among many evacuees. An experiment was conducted, letting people evacuate by two routes in an actual building, and giving about half of them mobile terminals. We easured the increases in the blood pressure and heart rates of the evacuees before and after the evacuation. In both routes, the rates of increase of these two characteristics in the evacuees with terminals were smaller than those in the evacuees without terminals, demonstrating that the proposed method provides assurance to evacuees. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(2): 19–31, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21165