This paper examines the impact of retail e-commerce on pricing behavior and welfare. Using Japanese data, we find that e-commerce lowered relative inflation rates for goods sold intensively online. We use long time series and historical catalog sales as an instrument for e-commerce sales intensity. The entry of e-commerce firms raised the rate of intercity price convergence in physical stores for goods sold intensively online, but not for other goods, which suggests e-commerce enhances price arbitrage. We estimate that e-commerce lowered variety-adjusted prices on average by 0.9 percent between 1996 and 2014, and more in cities with highly educated populations.
The demand for hydrogen energy is rapidly increasing because of its clean, abundant, and efficient nature. To utilize hydrogen gas as a fuel for fuel‐cell vehicles, several types of hydrogen sensors are needed to address cost and safety issues. Precise monitoring of hydrogen gas concentration is critical in optimizing vehicle fuel‐cell efficiency. Herein, a fully packaged hydrogen sensor to continuously measure a hydrogen concentration of 20–100% with environmental variations is fabricated, including temperature (from −40 to 105 °C), humidity (from 10 to 98 RH%), and pressure (from 30 to 350 kPa). A signal‐processing circuit is designed to reduce the error rate, and a sensor chip and printed circuit board are assembled in a module using a packaging process with robust materials for harsh vehicle environments. The result herein suggests direct application of the sensor to monitor hydrogen concentration in the hydrogen recirculation unit in a fuel‐cell vehicle.
This article describes the preparation of GeTe-based alloy films using a solution-based technique. The dissolution behavior of GeTe was initially examined by comparing the weight loss of GeTe powder in different solvents, and it was found that, unlike in the cases of n-butylamine
and NH4OH, KOH fully dissolved GeTe to form an agglomerate-free solution. X-ray diffraction analysis revealed that the reaction between GeTe and KOH resulted in the formation of rhombohedral GeTe, cubic GeTe4, and hexagonal Te structures after drying. GeTe-based alloy
films were then prepared by the spin coating of the GeTe-containing solutions on a silicon substrate. The surface morphology and reflectance properties of the prepared films were found to be highly dependent on the spin speed, with optimization of the spin coating parameter resulting in the
deposition of a continuous and smooth film.
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