Corrosion resistant films with almost the same film thickness were prepared on the magnesium alloy AZ61 by steam coating at different vapor pressure and treatment times. The effect of the vapor pressure on the structures and the corrosion resistance of the films was investigated by using FE-SEM, SEM-EDX, GAXRD, and potentiodynamic polarization curve measurements in a 3.5 mass percentage NaCl aqueous solution. These studies clarified that the interlayers of Mg-Al Layered Double Hydroxide (LDHs) increased and its structure became non-uniform with an increase in the vapor pressure. The corrosion current density slightly increased with an increase in the vapor pressure during the treatment, but pitting corrosion occurred at both low and high vapor pressures. These results indicate that water molecules were pushed into an interlayer of Mg-Al LDHs by high vapor pressure. Consequently, the interlayer distance of Mg-Al LDH was widened and the cracks were generated in the anti-corrosive film. On the other hand, the Mg-Al LDH with an insufficiently large interlayer distance could not fill the cracks in the Mg(OH)₂ crystallites and caused pitting corrosion when the vapor pressure was low.

This study investigated the corrosion behavior of the corrosion-resistant films steam coated on AZCa612 magnesium alloy. The film samples were corroded by immersing them in 5 wt% NaCl aqueous solution for a predetermined time. The corroded films were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, glancing angle X-ray diffraction, Fourier transform infrared spectroscopy, potentiodynamic polarization measurements, hydrogen generation measurements, and electrochemical impedance spectroscopy. The amount of Mg–Al–CO₃ layered double hydroxides (LDHs) in the film slightly decreased from the beginning of immersion to 120 h after immersion and gradually increased thereafter. Mg–Al–Cl LDHs were formed after 6 h of immersion and rapidly grew as the immersion progressed. In addition, even with the gradual decrease in the corrosion resistance of the film, there was no major damage observed on the substrates. These results indicate that the corrosion protection mechanism varied with the immersion time. The corrosion-resistant property under a short immersion time could be attributed to the high corrosion resistance of Mg(OH)₂ and AlO(OH), whereas it is attributed to the coverage provided by the Mg–Al–Cl and Mg–Al–CO₃ LDHs under a longer immersion duration.

Photoacoustic tomography (PAT), also known as optoacoustic tomography, has been emerging as a biomedical imaging modality that can provide cross-sectional or three-dimensional (3D) visualization of biological tissues such as blood vessels and lymphatic vessels in vivo at high resolution. The principle behind the visualization involves the light being absorbed by the tissues which results in the generation of ultrasound. Depending on the strength of ultrasound and its decay rate, it could be used to visualize the absorber location. In general, pulsed lasers such as the Q-switched Nd-YAG and OPO lasers that provide high-energy widths in the range of a few nanoseconds operating at low repetition rates are commonly used as a light source in photoacoustic imaging. However, such lasers are expensive and occupy ample space. Therefore, PAT systems that use LED as the source instead of lasers, which have the advantage of being obtainable at low cost and portable, are gaining attention. However, LED light sources have significantly low energy, and the photoacoustic signals generated have a low signal-to-noise ratio (SNR). Therefore, in LED-based systems, one way to strengthen the signal and improve the SNR is to significantly increase the repetition rate of LED pulses and use signal processing, which can be achieved using a high-power LED along M-sequence signal decoding. M-sequence signal decoding is effective, especially under high repetition rates, thus improving the SNR. However, power supplies for high-power LEDs have a circuit jitter, resulting in random temporal fluctuations in the emitted light. Such jitters, in turn, would affect the M-sequence-based signal decoding. Therefore, we propose a new decoding algorithm which compensates for LED jitter in the M-sequence signal processing. We show that the proposed new signal processing method can significantly improve the SNR of the photoacoustic signals.

ISO standards exist for evaluating sunscreens, such as those based on visual inspection. This assessment yields subjective results and is thus unreliable. Therefore, to verify the results of the visual assessment of sunscreens, quantitative evaluation methods are necessary. These methods require the measurement of the total radiation energy that is diffusely transmitted in all directions. For the measurements, although an integrating sphere is widely used to measure diffusely transmitted radiation, a simpler measurement would contribute to the easy usage of quantitative and objective evaluation. We propose the use of fluorescent materials as an alternative method to characterize sunscreens. In this method, a layer containing a fluorescent material is placed behind the sunscreen, and when the excitation radiation transmitted through the sunscreen reaches the fluorescent layer, it emits fluorescence. The feasibility of this measurement method was evaluated through numerical analysis and it demonstrated that hemispheric transmittance can be measured when the fluorescent layer is of high concentration or thick. Additionally, a prototype fluorescent layer was fabricated, and also the results were compared with the amount of diffusely transmitted UV from several commercial sunscreens. This pilot evaluation measurement method showed that the UV shielding index shown on the package does not necessarily truly reflect the amount of UV energy transmitted through the sunscreen, thus failing to provide the expected protection.

本研究では，アルミナ基板上の釉薬ベースEr酸化物膜において，石灰釉の熔融やCaEr₄(SiO₄)₃Oの生成に関するプロセスを明らかにした．そして，TPV発電用波長選択エミッターとして適切な焼成条件ならびに散乱を抑制する手法について検討した．その結果，（1）CaEr₄(SiO₄)₃OはEr₂O₃粒子と熔融石灰釉間の固相反応によって生成される，（2）Er₂O₃と石灰釉の重量比は約2：3で焼成温度は1250℃以上が望ましい，（3）緻密なEr₂O₃粒子を用いた微細化の防止やEr³⁺イオンを用いたEr酸化物のナノ粒子化といった粒径の制御が散乱抑制に有効である，ことが明らかとなった．