CoFe_2O_4 ferrite nanowire arrays are fabricated in porous silicon templates. The porous silicon templates are prepared via metal-assisted chemical etching with gold（Au） nanoparticles as the ...catalyst. Subsequently, CoFe_2O_4 ferrite nanowires are successfully synthesized into porous silicon templates by the sol–gel method. The magnetic hysteresis loop of nanowire array shows an isotropic feature of magnetic properties. The coercivity and squareness ratio（M_r/M_s） of ensemble nanowires are found to be 630 Oe（1 Oe = 79.5775 A·m~（-1） and 0.4 respectively. However, the first-order reversal curve（FORC） is adopted to reveal the probability density function of local magnetostatic properties（i.e., interwire interaction field and coercivity）. The FORC diagram shows an obvious distribution feature for interaction field and coercivity. The local coercivity with a value of about 1000 Oe is found to have the highest probability.
碩士
國立中山大學
海洋科學系研究所
103
Intertidal sediment has been increasingly acknowledged as a biogeochemical hotspot for element cycling. However, the tide-driven dynamics of carbon and nitrogen in the ...expansive tidal flats of the Changjiang (Yangtze River) Estuary, the largest estuary of China, was barely addressed. This study investigated the short-term variations of carbon and nitrogen in the intertidal sediment of Dongtan by the use of multiple approaches including monitoring hydrodynamics of the tides and pore fluid flow, sequential sampling of estuarine waters and intertidal sediment, and parallel whole-core incubation experiments. During tidal inundation, intensive resuspension and interfacial exchange of matter down to 8–9 cm depth have been observed for the silty sediment. We estimated that at the onset of exposure, the sediment received an input of labile organic matter at least 240 mmol C m–2, ~86% of which was deposited in the top layer. Biogeochemical processes, promoted by the slow but persistent vertical pore fluid flow that transported matter across the redox boundaries, exhibited an uneven temporal distribution over the course of exposure: reactions in the first one hour accounted for >61 % of NO3– removal and accumulation of biodegradation end products (dissolved inorganic carbon (DIC) and NH4+). These solutes were then replenished (NO3–) or flushed out (DIC, NH4+) in the next round of inundation. In contrast, the concentrations of dissolved organic carbon remained relatively stable over the tidal cycle, implying a dynamic equilibrium maintained by swift decomposition of particulate organic matter and remineralization into DIC. The daily rates of remineralization, NO3–removal and NH4+ release were comparable to those reported for sandflats. A conceptual model was constructed to summarize the input, transformation, and export of carbon and nitrogen in the silty sediment within tidal cycles.
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