circulation

摘要： Blockage in water-dominated flow pipelines due to hydrate reformation has been suggested as a potential safety issue during the hydrate production.In this work,flow velocity-dependent hydrate formation features are investigated in a fluid circulation system with a total length of 39 m.A 9-m section pipe is transparent consisted of two complete rectangular loops.By means of pressurization with gas-saturated water,the system can gradually reach the equilibrium conditions.The result shows that the hydrates are delayed to appear as floccules or thin films covering the methane bubbles.When the circulation velocity is below 750 rpm,hydrate is finally deposited as a“hydrate bed”at upmost of inner wall,narrowing the flow channel of the pipeline.Nevertheless,no plugging is observed during all the experimental runs.The five stages of hydrate deposition are proposed based on the experimental results.It is also revealed that a higher driving pressure is needed at a lower flow rate.The driving force of hydrate formation from gas and water obtained by melting hydrate is higher than that from fresh water with no previous hydrate history.The authors hope that this work will be beneficial for the flow assurance of the following oceanic field hydrate recovery trials.

摘要： The Regional Ocean Modeling System(ROMS)is employed to create a three-dimensional numerical model of the summer circulation in the Prydz Bay region,Antarctica.Consistent with the currents measured using an underway acoustic Doppler current profiler during a Chinese cruise,the simulated current field illustrates the major features of the Prydz Bay circulation,including the Antarctic Slope Current(ASC)along the continental shelf break,the cyclonic Prydz Bay Gyre,and the Prydz Bay Eastern Coastal Current(PBECC).The effects of grounding icebergs D15 and B15 on the circulation in Prydz Bay are investigated via numerical simulations.The results indicate that these giant grounding icebergs substantially affect the flows into and within the bay,which may differ with the different grounding locations.As grounding iceberg D15 is located close to the southwestern part of the West Ice Shelf(WIS),it cuts off the coastal current along the outer edge of the WIS,and the ASC can only enter Prydz Bay from the west side of iceberg D15,whereupon it becomes a main source of the PBECC.Iceberg D15 also weakens the circulation in the bay in general.The relatively small iceberg B15 entered Prydz Bay from 2007 to 2009 and grounded on the southwestern section of the Four Ladies Bank.The numerical experiments indicate that iceberg B15 guides the ASC flowing into the bay around its west side and reduces the width of the inflow on the eastern side of the Prydz Bay Channel.The grounding of iceberg B15 has also led to adjustments of the circulation within the bay,among which the most significant is that the outflow along the western flank of Fram Bank has shifted to the west and become more intensive.

摘要： The liver is the site of synthesis of the majority of circulating proteins.Besides initial polypeptide synthesis,sophisticated machinery is involved in the further processing of proteins by removing parts of them and/or adding functional groups and small molecules tailoring the final molecule to suit its physiological purpose.Posttranslational modifications(PTMs)design a network of molecules with the common protein ancestor but with slightly or considerably varying activity/localization/purpose.PTMs can change under pathological conditions,giving rise to aberrant or overmodified proteins.Undesired changes in the structure of proteins most often accompany undesired changes in their function,such as reduced activity or the appearance of new effects.Proper protein processing is essential for the reactions in living beings and crucial for the overall quality control.Modifications that occur on proteins synthesized in the liver whose PTMs are cirrhosis-related are oxidation,nitration,glycosylation,acetylation,and ubiquitination.Some of them predominantly affect proteins that remain in liver cells,whereas others predominantly occur on proteins that leave the liver or originate from other tissues and perform their function in the circulation.Altered PTMs of certain proteins are potential candidates as biomarkers of liver-related diseases,including cirrhosis.This review will focus on PTMs on proteins whose structural changes in cirrhosis exert or are suspected to exert the most serious functional consequences.

摘要： In this paper, the case of Jupiter being found in hydrodynamic equilibrium is for the first time investigated solely by mathematical methods. With the help of the hydrodynamic method, formulas of energy balance for oval and vortex are found, which are summed as permanent kinetic energy and constantly provide equilibrium for the stable rotational movements of Jupiter. To find the total kinetic energy of the oval and vortex in turbulent mode, Green’s function methods with special definitions and flow functions that describe the movement of the vortex are applied. The results are expressed in lemmas and theorems. For the hydrodynamic equilibrium of Jupiter, the necessary and sufficient conditions for the preservation of the cyclone and the anticyclone are mentioned. The relationships between the angular velocity and the gradient of pressure and the Corolias parameter are also given. The Rossby number is given for steady rotational motion. These facts show the existence of necessary and sufficient conditions for maintaining the stability of rotational motion and prove the hydrodynamic equilibrium of Jupiter. In this case using stream function and constructing generalized Green’s function and accordance energy conservation laws, the hydrodynamic equilibrium of Jupiter is proved.

摘要： An experimental investigation on flow fields within the scour holes upstream and downstream of circular piers positioned in tandem and staggered arrangements is reported and compared with isolated piers on mobile beds with uniform sediment.The instantaneous bed elevations and instantaneous three dimensional(3D)velocities were measured using a 5 MHz Ultrasonic Ranging system and 16 MHz micro down looking acoustic Doppler velocimeter,respectively.The velocity and flow depth were measured at different locations under near equilibrium bed scour conditions.The measured 3D velocities were processed for the computation of flow parameters,such as velocity fields,streamline patterns,vorticity fields,and circulation.Furthermore,turbulence intensities,turbulent kinetic energy,Reynolds shear stresses,and bed shear stresses around the piers for all three pier configurations were computed from the detrended velocity signals to identify significant differences in the flow parameters and turbulence in the tandem and staggered pier arrangements as compared to those for an isolated pier.A recirculation zone was found near the bed in front of the rear pier in the tandem case from the streamline patterns.The vortices in the bi-vortex system were observed to be opposite to each other in the gap between the three piers in the staggered case.A strong secondary vortex also was observed apart from the primary vortex at the foot of the pier(θ=0°)in all the three configurations.The strength of the horseshoe vortex(combination of primary and secondary vortices)was found to be higher at the front piers of the staggered arrangement as compared to those of the tandem piers,followed by the isolated pier.The bed shear stresses were found to be higher for the staggered piers than for the tandem piers in the direction of flow(θ=0°).However,a 50%reduction in the bed shear stresses was observed behind the tandem piers at θ=180°.The study reported in this paper provides the foundation for further investigation of countermeasures against local scour around tandem and staggered bridge piers on a mobile bed with non-uniform sediment.

摘要： Dissolved nutrients are essential to marine productivity and ecosystem structures in the Southern Ocean.The spatial distributions of dissolved nutrients in the Cosmonaut Sea were studied during the 37th Chinese National Antarctic Research Expedition in 2021.The relative standard deviations of the nitrate(NO_(3)-N),nitrite(NO_(2)-N),ammonium(NH_(4)-N),phosphate(PO_(4)-P),and silicate(SiO_(3)-Si)concentrations found in duplicate samples(n=2)were 1.01%,9.04%,6.45%,0.94%,and0.67%,respectively.The mean NO_(3)-N,NO_(2)-N,NH_(4)-N,PO_(4)-P,and SiO_(3)-Si concentrations in the mixed layer were 26.41±4.13,0.15±0.09,0.51±0.22,1.73±0.23,and 41.48±6.94μmol·L^(−1),respectively,and were higher than the relevant limitationconcentrations.The concentrations were generally bounded horizontally by the Southern Boundary(SB)of the Antarctic Circumpolar Current,the NO_(3)-N,NO_(2)-N,NH_(4)-N,and PO_(4)-P concentrations being higher northeast than southwest of the SB but the SiO_(3)-Si concentrations being higher southwest than northeast,indicating that the SB dominates nutrient distributions in themixed layer.The NO_(3)-N,NH_(4)-N,and PO_(4)-P concentrations gradually increased moving vertically down from the mixed layer to 200 m deep and then remained at 33.73±3.51,0.26±0.13,and 2.28±0.10μmol·L^(−1),respectively,to the bottom.The SiO_(3)-Si concentration increased as depth increased and reached a maximum in the bottom layer.The NO_(2)-N concentrationdecreased rapidly as depth increased and was~0μmol·L^(−1)at>150 m deep.Circumpolar Deep Water upwelling may cause high nutrient concentrations in shallower layers up to the 100 m layer between 62.5°S and 64°S.

摘要： This paper proposes and analyzes a novel heating coil bundle with the tubes arranged in a multi-level manner.The bundle generates a heated cargo large-scale circulation that enables a superposition of the circulation-driven forced convection on the buoyancy-driven natural convection,providing a more efficient mixed convection heat transfer mechanism.A simulationbased comparison of the proposed design and the conventional design is provided.The test case comprising an actual tank heating of an RMH 45 residual fuel oil by an 8-bar steam is simulated by a finite volume method and an OpenFOAM computational fluid dynamics software.The simulation results reveal that a 47.1%higher average heat transfer coefficient may be achieved,allowing a 32.0%reduction of the required heating coil area.

摘要： In the context of continued greenhouse gas emissions,the Earth has experienced very rapid warming over the past several decades.As the main reservoir of the Earth’s climate system,the ocean transfers much of the extra heat,which leads to long-term atmospheric warming,from sea surface to the deep oceans(IPCC,2019).Large-scale ocean circulation is one of the basic forms of sea water movement.

摘要： The global economy has been floundering since the outbreak of the COVID-19 pandemic in the beginning of 2020.Facing growing uncertainty,China unveiled a new economic development strategy of“dual circulation”with domestic and international markets reinforcing each other.