Development of subsurface chlorophyll maximum layer and its contribution to the primary productivity of water column in a large subtropical reservoir.

The phenomenon of subsurface chlorophyll maximum (SCM) layer emerging at a certain water depth is commonly found in stratified water bodies. Also, it is a crucial contributing region to the primary productivity of the water column. Currently, there is a lack of concern about the occurrence of SCM phenomena in studies targeting inland water bodies such as natural lakes and artificial reservoirs. This led to a significant underestimation of the level of primary productivity in these water bodies and their trophic state. In this study, a subtropical reservoir (the Xinanjiang Reservoir, XAJR) was investigated, to understand the characteristics of SCM layer in deep-large reservoir and its contribution to the primary productivity of the water column. Water sampling were conducted from September 2020 to August 2021, and in September 2022. Buoy station data for this reservoir between 2019 and 2021 were also collected. Based on the detailed observations of the water column profile in riverine area (X1), transitional area (X2), and central area (X3 and X4) of this reservoir, it was found that there was an obvious SCM phenomenon, which was closely related to the characteristics of seasonal thermal stratification. The SCM layer of XAJR appeared at depth around 3-5 m underwater from May to August, and as the thermal stratification strength increased, so did the depth and thickness of the SCM layer. It was estimated that gross primary productivity of euphotic layer of XAJR ranged from 347.9 to 4508.6 mgC·m-2·d-1. The average primary productivity level of the SCM layer reached 1411.7mgC·m-2·d-1, accounting for about 40-90% of the gross primary productivity of euphotic layer. This study contributes to a better understanding of the factors influencing changes in the development of the SCM layer in large reservoirs, as well as its critical role in the inland water carbon cycle.

[Determination of Fe and Ba in BaFe12O19 samples by binary ratio and X-ray fluorescence spectrometry].

A new quantitative analysis method was established for the determination of Fe and Ba in BaFe12O9 samples by binary ratio and X-ray fluorescence spectrometry. The calibration curve was established by a self-made pure Fe powder(AR) and pure BaCO3 powder(AR) standard sample which was prepared by powder pellet method. The standard sample has the content of Fe 75% and the content of Ba is 17.4% for the validation sample to verify the calibration curve fitting. Through the analysis the Fe and Ba content in the validation samples is 75.68% and 16.92%, the relative standard deviation is 0.317% and 1.11% respectively, The working curve has a good linear relationship with high accuracy and good precision. The experiment measured The content of Fe and Ba in BaFe12O19 sample was measured in the experiment to be 57.28% and 13.42%, and the relative standard deviation is 1.05% and 0.73%, respectively.

Optimized thermal design of new reflex LED headlamp.

This paper focuses on the heat dissipation efficiency issues in LED headlamps. The cooling structure is designed and built in Ansys-icepak software based on computational fluid dynamics. During optimized simulation of a single model, geometric parameters, maximum temperature, and thermal resistance are taken as variables, constraint, and objective, respectively. In the case of 85 °C, the optimized model has mass of 0.28 kg, maximum temperature rise of 12.52 °C, and thermal resistance of 1.03 °C/W. During the design of the headlamp, air inlet and outlet are arranged, respectively, taking advantage of airflow generated from the moving auto. The maximum temperature rise is 6.5 °C lower than that in closed case at the speed of 2 m/s.