Dissolved Organic Carbon in the North Atlantic Meridional Overturning Circulation

The quantitative role of the Atlantic Meridional Overturning Circulation (AMOC) in dissolved organic carbon (DOC) export is evaluated by combining DOC measurements with observed water mass transports. In the eastern subpolar North Atlantic, both upper and lower limbs of the AMOC transport high-DOC waters. Deep water formation that connects the two limbs of the AMOC results in a high downward export of non-refractory DOC (197 Tg-C·yr-1). Subsequent remineralization in the lower limb of the AMOC, between subpolar and subtropical latitudes, consumes 72% of the DOC exported by the whole Atlantic Ocean. The contribution of DOC to the carbon sequestration in the North Atlantic Ocean (62 Tg-C·yr-1) is considerable and represents almost a third of the atmospheric CO 2 uptake in the region

Impacts of past abrupt land change on local biodiversity globally

Abrupt land change, such as deforestation or agricultural intensification, is a key driver of biodiversity change. Following abrupt land change, local biodiversity often continues to be influenced through biotic lag effects. However, current understanding of how terrestrial biodiversity is impacted by past abrupt land changes is incomplete. Here we show that abrupt land change in the past continues to influence present species assemblages globally. We combine geographically and taxonomically broad data on local biodiversity with quantitative estimates of abrupt land change detected within time series of satellite imagery from 1982 to 2015. Species richness and abundance were 4.2% and 2% lower, respectively, and assemblage composition was altered at sites with an abrupt land change compared to unchanged sites, although impacts differed among taxonomic groups. Biodiversity recovered to levels comparable to unchanged sites after >10 years. Ignoring delayed impacts of abrupt land changes likely results in incomplete assessments of biodiversity change

Multi-scale simulation of the 1,3-butadiene extraction separation process with an ionic liquid additive

A multi-scale simulation method is proposed to enable screening of ionic liquids (ILs) as entrainers in extractive distillation. The 1,3-butadiene production process with acetonitrile (ACN) was chosen as a research case to validate the feasibility of the methodology. Ab initio calculations were first carried out to further understand the influence of ionic liquids on the selectivity of ACN and the solubility of C(4) fractions in [C(n)MIM][PF(6)](n = 2-8), [C(2)MIM][X] (X = BF(4)(-), Cl(-), PF(6)(-), Br(-)), by investigating the microstructure and intermolecular interaction in the mixture of C(4) fractions and several selected ionic liquids. It was found that the selectivity of the ionic liquid is determined by both its polarity and hydrogen-bonding ability. Based on the analysis, a suitable ionic liquid was chosen. With the ab initio calculation, a priori prediction of thermophysical data of the IL-containing system was performed with COSMO-RS. The calculation revealed that the selectivity of the extractive solvent was increased by an average of 3.64% after adding [C(2)MIM][PF(6)]. With above calculations, an improved ACN extraction distillation process using ILs as an entrainer was proposed, and a configuration for the new process was constructed. Based on the established thermodynamic models which have considered the properties from the molecular structure of ILs, process simulation was performed to obtain the process parameters which are important for the new process design. The simulation results indicated that the temperatures at the bottom of the extractive distillation column with the ionic liquid as an additive are lowered by an average of 3.1 degrees C, which is significant for inhibition of polymerization. We show that the ACN consumption using this process can be lowered by 24%, and the energy consumption can likewise be lowered by 6.62%

Research on Elastic Deformation Modeling of Collaborative Robots

To improve the positioning accuracy of collaborative robots, an elastic deformation modeling method of manipulator robots is proposed in this paper. This approach is able to consider flexibility of robot modules comprehensively, and can compensate the elastic deformation caused by external wrenches and the deadweight of the robot in addition to possessing advantages of low computational complexity, easy modification as well as high real-time. Firstly, stiffness matrices of each robot module with 36 degrees of freedom (DOFs) are obtained by using the finite element analysis. Then, the kinematic model of a robot is established which is adapted to stiffness modeling of robot modules, and the force condition can be achieved by the robot statics analysis with the deadweight in order to acquire the elastic deformation of module units, which will be used to compensate the positioning error resulted from manipulator compliance. Furthermore, the elastic deformation model is built by the differential transformation method, and can be used to compensate the positioning error. Lastly, the finite element simulation is carried out, and results of the simulation show the proposed modeling method is effective.</p