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[en] Photoacoustic microscopy is capable of providing high-resolution molecular images, and its spatial resolution is typically determined by ultrasonic transducers used to receive the photoacoustic signals. Therefore, ultrasonic transducers for photoacoustic microscopy (PAM) should have a high operating frequency, broad bandwidth, and high signal-reception efficiency. Polyvinylidene fluoride (PVDF) is a suitable material. To take full advantage of this material, the selection of the backing material is crucial, as it influences the center frequency and bandwidth of the transducer. Therefore, we experimentally determined the most suitable backing material among EPO-TEK 301, E-Solder 3022, and RTV. For this, three PVDF high-frequency single-element transducers were fabricated with each backing material. The center frequency and -6 dB bandwidth of each transducer were ascertained by a pulse-echo test. The spatial resolution of each transducer was examined using wire-target images. The experimental results indicated that EPO-TEK 301 is the most suitable backing material for a PAM transducer. This material provides the highest signal magnitude and a reasonable bandwidth because a large portion of the energy propagates toward the front medium, and the PVDF resonates in the half-wave mode.
[en] This paper begins by describing some commonly used photonic packages. The requirements for optical connections to these packages are then discussed. Photonic packages are different to most electronic packages in that the thermal management requirements usually include maintaining the Photonic Integrated Circuit (PIC) at a fixed, sometimes below ambient, operating temperature rather than with keeping the temperature of a package below an upper limit as with most electronic packages. This means that an active Thermoelectric Module (TEM) based cooling system is required. A thermistor is fitted within the package to provide thermal feedback to the TEM controller. This paper uses finite element modelling to investigate whether there is a good match between the target temperature for the PIC and the temperature registered by the thermistor. The results of the modelling show that the model results are quite stable even with large variations in convection and thermistor thermal properties. The thermistor location influences the temperature measured from the package and its thermal response time, but follows the device temperature well enough to provide the TEM controller with adequate feedback to maintain the PIC at a steady temperature in steady state running conditions.
[en] The materials composed of the 3d series transition metals are introduced into the hydrocarbon steam-reforming reaction in order to enhance the H2 production and abruptly depress the catalytic deactivation resulting from the strong sintering between the Ni component and the γ-Al2O3 support. The conventional impregnation method is used to synthesize the Ni/3d series metal/γ-Al2O3 materials through the sequentially loading Ni source and the 3d series metal (Ti, V, Cr, Mn, Fe, Co, Cu, and Zn) sources onto the γ-Al2O3 support. The Mnloaded material exhibits a significantly higher reforming reactivity than the conventional Ni/γ-Al2O3 and the other Ni/3d series metal/γ-Al2O3 materials. Particularly the addition of Mn selectively improves the H2 product selectivity by eliminating the formation of CH4 and CO. The H2 production is maximized at a value of 95% over Ni(0.3)/Mn(0.3)/γ-Al2O4(1.0) with a butane conversion of 100% above 750 .deg. C for up to 55 h
[en] In this review work, energy harvesting methods for waste heat with small temperature differences between heat source and sink are discussed. At present, many methods are tried and employed to utilize this type of waste heat. A typical example is found in a conventional power generation system. By utilizing this type of waste heat, additional energy can be produced in regular power generation systems. Up to this point, two energy harvesting methods have been introduced and applied for the use with this type of waste heat. One is a method using an organic Rankine cycle (ORC) while the other is a method using a thermoelectric generation (TEG). An ORC is a Rankine cycle that can be applied to this type of waste heat using organic fluids such as refrigerants as working fluids instead of water used in a typical Ranking cycle. On the other hand, a TEG utilizes Peltier, Seebeck, and Thomson effects caused by the temperature difference between the heat source and sink for energy harvesting. In this work, various aspects associated with the use ORC and TEG for waste heat harvesting with small temperature differences between the heat source and sink.
[en] This work investigates the hydrogen generation via methanol thermal decomposition (TD) over the three group IA alkali metals, Na, K, and Cs, incorporated into aluminosilicate catalysts (IA-AlxSiyOz). The scanning electron microscopy (SEM) images of the IA-AlxSiyOz catalysts revealed various and regular morphologies such as cube (Na), bouquet (K), and spherical (Cs), but the other two catalysts, K-alumina and silica, were irregular and non-uniform. The catalytic performances differed according to the alkali elements. The K-AlxSiyOz catalyst provided a significantly higher methanol decomposition and hydrogen production than the other catalysts: the H2 production was maximized at 78% at a reaction temperature of 550 oC, CH3OH concentration of 30 vol-%, and gas hourly space velocity (GHSV) of 1800 h-1. In an unusual result, carbon nano filaments were created over the K-AlxSiyOz catalyst after the reaction even though CO2 and ethanol were not used. In the proposed mechanism, the group IA metals played an important role in depressing the strong acidities at the Al sites, and K was determined to be the most effective in increasing the hydrogen yield and suppressing the generation of CO and CO2. -- Highlights: → The K-AlxSiyOz catalyst provided a significantly higher methanol decomposition and hydrogen production than the other catalysts. → The H2 production in K-AlxSiyOz catalyst was maximized at 78% at a reaction temperature of 550 oC. → Carbon nano filaments were created over the K-AlxSiyOz catalyst after the reaction. → K was determined to be the most effective in increasing the hydrogen yield and suppressing the generation of CO and CO2.