Horizontal distribution of tintinnids (Ciliophora) in surface waters of the Ross Sea and polynya in the Amundsen Sea (Antarctica) during summer 2019/2020

Information on tintinnid horizontal distribution in the Antarctic Continental Zone is scarce. During the summer of 2019/2020, tintinnid diversity and horizontal distribution in surface waters were investigated in the Ross Sea and Amundsen Sea polynya. Eight tintinnid species were found and the dominant species showed obvious horizontal distribution characteristics. In the Ross Sea, three tintinnid community groups were identified. Cymatocylis cristallina and Laackmanniella prolongata (group I) were dominant species and were mainly distributed in stations closer to the coast than were species in the other two groups. Codonellopsis gaussi (group II) and Cy. convallaria (group III) were mainly distributed in nearshore and offshore stations, respectively. In the Amundsen Sea polynya, the dominant species Cy. cristallina, L. prolongata and Salpingella faurei (group I) were mainly distributed in stations closer to the coast than were species in the other two groups. Cy. convallaria (group III) was mainly distributed in offshore stations. The distribution area where C. gaussi and C. cristallina were found in high abundance and abundance proportion of loricae with protoplasts was divided by the approximate boundary of the Antarctic Slope Front Current and Coastal Current in the Ross Sea. The highest abundance proportion in the Ross Sea was the 32–36 μm lorica oral diameter (LOD) size class (75.7%), and the 36–40 μm LOD size class (56.0%) was found in the Amundsen Sea polynya. Temperature– salinity–plankton diagrams of the two seas revealed that temperature may be the main reason for species distribution. Our results contribute to a better understanding of horizontal distribution of the microbial food web, and serve as a baseline for future studies of pelagic community change in the Antarctic Continental Zone

Spatial distribution of aloricate ciliates in the stratified water of the Cosmonaut and Cooperation Seas in the Southern Ocean

Aloricate ciliates are the main component of microzooplankton. They play important roles in the circulation of materials and flow of energy in marine pelagic ecosystems. To determine the distribution pattern and structure of the aloricate ciliate community in vertically stratified waters of the Southern Ocean, we collected data on aloricate ciliates in the Cosmonaut and Cooperation Seas during the 36th Chinese National Antarctic Research Expedition. The ranges of aloricate ciliate abundance and biomass were 5–3097 ind·L−1 and 0.01–11.40 μg C·L−1, respectively. Vertically, the average abundance of aloricate ciliates decreased from the surface to 200 m, while biomass was highest in the 50-m layer. The importance of aloricate ciliates <20 μm increased along the depth gradient. Their contribution to total abundance increased from 13.04% in the surface layer to 73.71% in the 200-m layer. This is the first study to explore the distribution characteristics of the aloricate ciliate community in a stratified water column of the Southern Ocean. Our results will be helpful for understanding the variation in the pelagic community in waters of the Southern Ocean with intensified stratification

Investigation of hydrate slurry flow behaviors in deep-sea pipes with different inclination angles

The marine area is the main direction of the development of oil and gas resources in the world. The pipeline transportation technology of natural gas hydrate slurry plays an important role in the exploitation of marine oil and gas and the exploitation of marine gas hydrate resources. In order to study the influence of pipe inclination on pipeline transportation, population balance model based on hydrate particle aggregation dynamics was coupled with the Eulerian–Eulerian two-fluid multiphase flow model to simulate the flow behaviors of hydrate slurry flow in pipes with different inclination angles. In the study, three variables of inclination, flow rate and initial particle size were considered. The results show that tilted pipes are beneficial to hydrate slurry transport rather than harmful. Meanwhile, higher flow rates and lower initial particle sizes are beneficial for promoting the flow safety of hydrate slurry transport. However, the flow pressure drop of the hydrate slurry increases with the increase of the flow rate and the decrease of the initial particle size, which is not conducive to the economics of mining. The research results in this paper can provide reference for the research of hydrate slurry flow safety and parameter guidance for hydrate solid fluidized mining

Colloidal organic carbon and trace metal (Cd, Fe, and Zn) releases by diatom exudation and copepod grazing

Colloidal macromolecular organic compounds are important intermediaries between solution and particle phases and play a critical role in the biogeochemistry of trace metals and organic carbon. The releases of colloidal organic carbon and trace metals (Cd, Fe, and Zn) mediated by copepod grazing and decomposition, and direct diatom exudation, were examined using a radiotracer approach. The colloidal phase was operationally defined in this study as the size fraction between 5 kDa and 0.2 mum and the dissolved phase as the :0.2 pm filter passing phase. About 13-60\% of dissolved carbon exuded by the diatom Thalassiosira pseudonana was partitioned into the colloidal phase, and this fraction increased considerably as the diatom cells grew older. A lower fraction of dissolved C-14 (12-23\%) excreted by the copepods Acartia erythraea was detected in the colloidal phase compared to carcass (13-35\%) and feces decomposition (21-34\%). In contrast to carbon, a lower fraction of regenerated dissolved Cd (1-11\%) and Zn (0-20\%) from copepods and diatoms was consistently detected in the colloidal phases. Copepod excretion and carcass decomposition resulted in more colloidal Fe (51-91\%) than diatom exudation (46-62\% for Thalassiosira weissflogii, and 3-33\% for T pseudonana) and copepod feces decomposition (16-30\%). Copepod (Calanus sinicus) grazing reduced the colloidal fraction of dissolved C-14, although a higher concentration of the diatom's (T. weissflogii) carbon was regenerated into the dissolved phase. The grazing of these copepods did not have any influence on the colloidal metal partitioning. The release of trace metals and carbon was enhanced by a higher density of copepod's grazing. Thus, different biological processes (grazing, excretion, exudation, and decomposition) may contribute differently to the production and dynamics of colloidal carbon and metals in planktonic systems. (C) 2004 Elsevier B.V. All rights reserved

A Predictive Analysis Method of Shafting Vibration for the Hydraulic-Turbine Generator Unit

The shafting vibration for the Hydraulic-Turbine Generator Unit (HGU) inevitably affects the safe and stable operation of the Units. Excessive shafting vibration could cause fatigue damage of materials, which eventually leads to malfunction of HGU and even results in damage accidents in serious cases. Generally speaking, the vibration is mainly generated from the high-speed rotation of the shafting, and mechanical, hydraulic, and electrical factors as the vibration exciting sources may be coupled all to cause a vibration of the HGU, so it is necessary to take the whole shafting as a specific object of study. In recent years, many scholars have conducted much research on them and their results are focused more on how to control the influence of external excitation sources of vibration, but still lack consideration of the shafting&rsquo;s internal mechanism of vibration. In this paper, a predictive analysis method is proposed to reveal the internal mechanism of vibration. Starting from the analysis of natural vibration characteristics of the shafting, this study establishes the finite element calculation model of the shafting of the HGU based on the finite element analysis method. By selecting appropriate research methods and calculation procedures, the modal analysis of the dynamic characteristics of the shafting structure is carried out. Finally, the first ten-order natural vibration characteristics and critical rotational speed of the shafting structure are successfully calculated, and the results conform to the basic laws of shafting vibration. In addition, by comparing the relationship between rotational frequency such as the rated speed, runaway speed, and critical speed of the shafting, the possibility of resonance of the HGU is analyzed and predicted, and then some suggestions for optimization design such as increasing the shafting&rsquo;s stiffness and balancing its mass distribution are proposed. Therefore, this study provides a basis for guiding the structural design and optimization of the shaft system in engineering, and avoids the resonance caused by the excitation source such as rotational frequency, thereby ensuring the safe and stable operation of the HGU

A Predictive Analysis Method of Shafting Vibration for the Hydraulic-Turbine Generator Unit

The shafting vibration for the Hydraulic-Turbine Generator Unit (HGU) inevitably affects the safe and stable operation of the Units. Excessive shafting vibration could cause fatigue damage of materials, which eventually leads to malfunction of HGU and even results in damage accidents in serious cases. Generally speaking, the vibration is mainly generated from the high-speed rotation of the shafting, and mechanical, hydraulic, and electrical factors as the vibration exciting sources may be coupled all to cause a vibration of the HGU, so it is necessary to take the whole shafting as a specific object of study. In recent years, many scholars have conducted much research on them and their results are focused more on how to control the influence of external excitation sources of vibration, but still lack consideration of the shafting’s internal mechanism of vibration. In this paper, a predictive analysis method is proposed to reveal the internal mechanism of vibration. Starting from the analysis of natural vibration characteristics of the shafting, this study establishes the finite element calculation model of the shafting of the HGU based on the finite element analysis method. By selecting appropriate research methods and calculation procedures, the modal analysis of the dynamic characteristics of the shafting structure is carried out. Finally, the first ten-order natural vibration characteristics and critical rotational speed of the shafting structure are successfully calculated, and the results conform to the basic laws of shafting vibration. In addition, by comparing the relationship between rotational frequency such as the rated speed, runaway speed, and critical speed of the shafting, the possibility of resonance of the HGU is analyzed and predicted, and then some suggestions for optimization design such as increasing the shafting’s stiffness and balancing its mass distribution are proposed. Therefore, this study provides a basis for guiding the structural design and optimization of the shaft system in engineering, and avoids the resonance caused by the excitation source such as rotational frequency, thereby ensuring the safe and stable operation of the HGU

Experimental study on flow characters of CH3CCl2F hydrate slurry

The flow behaviors of CH3CCl2F hydrate slurry with volume concentration of 10-70% were studied in a new built flow loop with a diameter of 42.0 mm and length of 30.0 m. Morphologies of the fluids from slurrylike hydrates to slushlike hydrates with increasing of hydrate volume concentration in pipeline were observed. Pressure drops in pipeline also were studied and an exceptional pressure transition zone with hydrate volume concentration between 30% and 40% was found for the first time, which can be used as a notation to judge if the pipeline runs safely or not. Fanning friction factors of the hydrate slurries with all hydrate contents tend to constants between 0.38 and 0.5, which depend on the volume concentration in slurries, when the velocity reaches 1.5 m/s. A simple relation to estimate the pressure drop of hydrate slurry in pipeline was presented and verified. Experimental results were compared to the estimated results, which showed a good agreement. (C) 2007 Elsevier Ltd and IIR. All rights reserved