Hirosaki University

Passive radon monitors with CR-39s are commonly used in major epidemiological studies. However, the conventional CR-39 track density analysis method makes it difficult to estimate the concentration accurately due to the heterogeneity of tracks on CR-39s and the small track reading area. Track heterogeneity in CR-39 detectors arises from exposure-related and detector-related factors. To improve the accuracy of track density analysis in passive radon monitors, this study implemented a new stochastic approach utilizing Latin Hypercube Sampling (LHS) to compare the performance to the conventional method. Consequently, the stochastic method reduces the root mean square deviation of mean track density by 15.6 % compared to the conventional method. The coefficient of determination of the stochastic method is significantly higher than that of the conventional method in the linear correlation of estimated track density and accumulated exposure. The stochastic method utilizing the LHS for track density analysis decreased the total counting area of CR-39 and performed congruently and effectively, as the large counting area using the conventional strategy. These findings suggest the stochastic approach is a promising method for improving track density determination in passive radon measurements with CR-39 detectors.

In this work, a CuMn-bimetal-based metal-organic framework (MOF) encapsulated Co₃O₄ composite (CuMn-MOF@Co₃O₄) with a three-dimensionmal hierarchical structure formed by interwoven nanosheets was in-situ grown on nickel foam (NF) through a three-step fabrication method for the electrochemical methanol oxidation reaction(MOR). The characterizations revealed the phase transformation of CuMn-MOF during the electrochemical activation generated abundant hydroxides/hydroxyoxides (Cu(OH)₂, Mn(OH)₂, MOOH), which provided optimal architecture and real active sites for MOR. At the same time, the combination of Co₃O₄ with the generated CuMn(OH)_x effectively enhanced the synergistic interactions between them, greatly hindering high-valent hydroxides formation, lowering methanol and intermediate adsorption energy barriers, thereby ensuring highly selective electrooxidation of methanol to formate with high activity. As a result, the electrochemically reconstructable CuMn-MOF@Co₃O₄ composite exhibited excellent performance, achieving a high MOR current density of 500 mA cm^-2 at 1.41 V vs. RHE, with a Faradaic efficiency (FE) of near 100 % and long-term stability. Moreover, in a two-electrode electrolysis system with MeOH-water solution, only 1.60 V of cell voltage was required to maintain a current density of 100 mA cm^-2 for MOR-HER, which significantly reduced energy consumption compared to the conventional OER-HER system. It opens a novel avenue for the design of advanced electrochemically reconstructable MOF-based composites for elecrooxidation process.

In this study, a series of hollow-structured DSx/HZSM-5 zeolites were synthesized through a method of alkaline treatment with sodium hydroxide (NaOH) solution. The size of cavities and amount of acid sites in hollow zeolite can be exactly controlled by adjusting the NaOH concentration. The hollow HZSM-5 zeolites were employed for catalytic deoxygenation of bio-oils from fast pyrolysis of Giant Miscanthus via a dual-furnace-heated fix-bed reactor. Experimental results illustrated that the hollow structure enhanced the formation of deoxygenated aromatic compounds. The best hollow HZSM-5 zeolite named DS2/HZSM-5 exhibited the highest catalytic efficiency with a selectivity toward deoxygenated aromatic compounds of 75.9 ± 0.8 %. Moreover, the formation mechanism of hollow structure and possible pathways for deoxygenated compounds formation were proposed. In addition, the DS2/HZSM-5 catalyst demonstrated higher stability than the parent one. The results confirm that the hollow-structured HZSM-5 zeolite is a promising catalyst for efficient and stable upgrading of bio-oils.