Dynamic in situ observation of automotive catalysts for emission control using X-ray absorption fine structure

Two main pivotal subjects of research in automotive catalysts were studied by modern X-ray absorption analysis techniques. One is oxygen storage/release behaviour, and the other is sintering inhibition of Pt particles. First, three types of CeO₂–ZrO₂ (Ce:Zr = 1:1 molar ratio) compounds with different oxygen storage/release capacities and different structural properties were prepared, and the valence change of Ce as a function of temperature during oxygen release/storage processes was investigated. The reduction of surface Ce mainly occurred in the range 100–170 °C, and the reduction of bulk Ce progressed at high temperatures of 170 °C and above. The Ce reduction behaviour depended not only on the homogeneity of the Ce and Zr for bulk reduction at high temperatures but also on the particle size of the CeO₂–ZrO₂ samples for surface reduction at low temperatures. Secondly, sintering inhibition of Pt in Pt/Al₂O₃, Pt/MgO and Pt/ceria-based catalysts after 800 °C ageing in air was studied. We found that the Pt–O–M (M = Mg, Ce) bond acted as an anchor and inhibited the sintering of Pt particles on MgO or ceria-based oxide. Especially, it was noteworthy that the Pt–O–Ce⁴⁺ bond on the ceria-based support breaks easily through the reduction of Ce (Ce⁴⁺ → Ce³⁺) during the usual stoichiometric and reducing conditions.     

On-chip cell sorting system using laser-induced heating of a thermoreversible gelation polymer to control flow

We have developed a microfabricated fluorescence-activated cell sorter system using a thermoreversible gelation polymer (TGP) as a switching valve. The glass sorter chip has Y-shaped microchannels with one inlet and two outlets. A biological specimen containing fluorescently labeled cells is mixed with a solution containing a thermoreversible sol-gel polymer. The mixed solution is then introduced into the sorter chip through the inlet. The sol-gel transformation was locally induced by site-directed infrared laser irradiation to plug one of the outlets. The fluorescently labeled target cells were detected with sensitive fluorescence microscopy. In the absence of a fluorescence signal, the collection channel is plugged through laser irradiation of the TGP and the specimens are directed to the waste channel. Upon detection of a fluorescence signal from the target cells, the laser beam is then used to plug the waste channel, allowing the fluorescent cells to be channeled into the collection reservoir. The response time of the sol-gel transformation was 3 ms, and a flow switching time of 120 ms was achieved. Using this system, we have demonstrated the sorting of fluorescent microspheres and Escherichia coli cells expressing fluorescent proteins. These cells were found to be viable after extraction from the sorting system, indicating no damage to the cells.     

Radiochemical analysis of rubble and trees collected from Fukushima Daiichi Nuclear Power Station

To characterize the rubble and trees contaminated by radionuclides released by the recent accident at the Fukushima Daiichi Nuclear Power Station, the radiochemical analysis protocols were modified using those developed by the Japan Atomic Energy Agency for the waste generated by research, industrial, and medical facilities. The radioactivity concentrations of gamma-ray-emitting nuclides ⁶⁰Co, ⁹⁴Nb, ¹⁵²Eu, and ¹⁵⁴Eu, and beta-particle-emitting nuclides ¹⁴C, ¹²⁹I, ³⁶Cl, ⁷⁹Se, and ⁹⁹Tc were successfully applied by the modified analytical method. In contrast, the radioactivity concentrations of ³H, ⁹⁰Sr, ¹³⁷Cs, and alpha-particle-emitting nuclides were applied by the conventional method. Unfortunately, ³⁶Cl, ⁹⁴Nb, ¹²⁹I, ¹⁵²Eu, ¹⁵⁴Eu, and alpha-particle-emitting nuclides were below the detection limit of the conventional method. The measured radioactivity concentrations, except for that of ³H, were not uniform in the area but depended on the reactor unit. Although the radioactivity concentrations were varied widely, this analysis successfully clarified the characteristics of the radioactivity concentrations of the rubble and trees.     

Electric double‐layer capacitor module with series‐parallel reconfigurable cell voltage equalizers

When electric double‐layer capacitors (EDLCs) are connected in series, a cell voltage imbalance occurs due to nonuniform cell properties. Cell voltage imbalance should be minimized to prolong cycle lives and maximize the available energy of cells. In this study, we propose a series‐parallel reconfigurable cell voltage equalizer that is considered suitable for energy storage systems using EDLCs instead of traditional secondary batteries as the main energy storage sources. The proposed equalizer requires only EDLCs and switches as its main circuit elements, and it utilizes EDLCs not only for energy storage but also for equalization. An equivalent circuit model using equivalent resistors that can be regarded as an index of equalization speed is developed. Current distribution and cell voltage imbalancing during operation are quantitatively generalized. Experimental charge–discharge tests were performed on the EDLC modules to demonstrate the performance of the cell voltage equalizer. All the cells in the modules could be charged/discharged uniformly even when a degradation‐mimicking cell was intentionally included in the module. The resultant cell voltage imbalances and current distributions were in good agreement with those predicted by mathematical analyses. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(4): 38–50, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21287     

Active device‐less voltage equalization charger using capacitors,diodes, and an AC power source

Conventional cell/module voltage equalizers or equalization chargers based on traditional DC‐DC converters require numerous switches or transformers as the number of series connections increases; therefore, their cost and complexity tend to increase and their reliability decreases as the number of connections increases. This paper proposes a novel voltage equalization charger that consists only of passive components such as capacitors, diodes, and a transformer. The fundamental operating principle, major features, and derivation of equivalent DC circuits are presented. A symmetrical configuration is also proposed to mitigate the RMS current flowing through energy storage cells in the charging process. Simulations and experimental charging and cycle tests were performed on series‐connected electric double‐layer capacitor modules to demonstrate the equalization performance. The experimental and simulation results were in good agreement, and the voltage imbalances were gradually eliminated as time elapsed even during charge‐discharge cycling. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(3): 39‐48, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21288     

Role of Cooper pairs for the generation of entangled photon pairs from single quantum dots

Generation of entangled photon pairs from semiconductor quantum dots (QDs) is highly desirable for realizing practical solid-state photon sources for quantum information processing and quantum cryptography. However, the energy splitting of exciton states in QDs almost prevent the generation of entangled photon pairs. This paper discusses the new possibility with the injection of electron as well as hole Cooper pairs into QDs.     

Uncooled 25 Gbit/s direct modulation of semi-insulating buried-heterostructure 1.3 μm AlGaInAs quantum-well DFB lasers

Uncooled 25 Gbit/s direct modulation of 1.3 mum DFB lasers is demonstrated. The 150 mum-long semi-insulating buried-heterostructure AIGalnAs quantum-well DFB lasers show clear eye-openings with dynamic extinction ratio of 5 dB up to 70degC. 13 km singlemode-fibre transmission experiments using the devices show low power penalty within 1.3 dB between 25 and 70degC. These characteristics are the first achievement by 1.3 mum directly modulated lasers.     

Coherent Optical 25.8-Gb/s OFDM Transmission Over 4160-km SSMF

We discuss coherent optical orthogonal frequency division multiplexing (CO-OFDM) as a suitable modulation technique for long-haul transmission systems. Several design and implementation aspects of a CO-OFDM system are reviewed, but we especially focus on phase noise compensation. As conventional CO-OFDM transmission systems are very sensitive to laser phase noise a novel method to compensate for phase noise is introduced. With the help of this phase noise compensation method we show continuously detectable OFDM transmission at 25.8 Gb/s data rate (20 Gb/s after coding) over 4160-km SSMF without dispersion compensation.     

Rainfall propagation impairments for medium elevation angle satellite‐to‐earth 12 GHz in the tropics

Rain attenuation is the dominant propagation impairment for satellite communication systems operating at frequencies above about 10 GHz. The rainfall path attenuation at 12.255 GHz measured at Universiti Sains Malaysia (USM) for 4 years (2 January to 5 December) is presented. This paper presents an empirical analysis of rain rate and rain attenuation cumulative distribution functions obtained using 1‐min integrated rainfall data and comparison of the measured data with data obtained from well‐established rain model attenuation predictions. Copyright © 2008 John Wiley & Sons, Ltd.     

Bending fatigue strength of case-carburized helical gears with large helix angles up to 40 degrees

Case-carburizing of helical gears with large helix angles may form too large hardened layers near the tooth width end on the acute angle side (ACUTE-END), and adversely affect the bending fatigue strength. We investigated the bending fatigue strength of casecarburized helical gears with large helix angles up to approximately 40° through a bending fatigue test, hardness test, and residual stress measurement. We found that the case-carburizing formed large hardened layers near ACUTE-END, reduced the compressive residual stress near ACUTE-END, and restricted the improvement of the bending fatigue strength in a meshing state where tooth root stress became large near ACUTE-END. Based on the obtained bending fatigue limits, we revealed that ISO 6336-3:2006 overestimated the rate of increase of the permissible circumferential loads for helix angles exceeding approximately 30°, and ISO/DIS 6336-3:2018 underestimated this rate for helix angles near 30°.