The build up of the correlation between halo spin and the large scale structure

Both simulations and observations have confirmed that the spin of haloes/galaxies is correlated with the large scale structure (LSS) with a mass dependence such that the spin of low-mass haloes/galaxies tend to be parallel with the LSS, while that of massive haloes/galaxies tend to be perpendicular with the LSS. It is still unclear how this mass dependence is built up over time. We use N-body simulations to trace the evolution of the halo spin-LSS correlation and find that at early times the spin of all halo progenitors is parallel with the LSS. As time goes on, mass collapsing around massive halo is more isotropic, especially the recent mass accretion along the slowest collapsing direction is significant and it brings the halo spin to be perpendicular with the LSS. Adopting the $fractional$ $anisotropy$ (FA) parameter to describe the degree of anisotropy of the large-scale environment, we find that the spin-LSS correlation is a strong function of the environment such that a higher FA (more anisotropic environment) leads to an aligned signal, and a lower anisotropy leads to a misaligned signal. In general, our results show that the spin-LSS correlation is a combined consequence of mass flow and halo growth within the cosmic web. Our predicted environmental dependence between spin and large-scale structure can be further tested using galaxy surveys.Comment: 9 pages, 7 figures, 2 tables, Accepted for publication in MNRA

Maximizing spectral radii of uniform hypergraphs with few edges

In this paper we investigate the hypergraphs whose spectral radii attain the maximum among all uniform hypergraphs with given number of edges. In particular we characterize the hypergraph(s) with maximum spectral radius over all unicyclic hypergraphs, linear or power unicyclic hypergraphs with given girth, linear or power bicyclic hypergraphs, respectively

Optimization of a Chemical Production Facility: A study of operating conditions, equipment sizing, and economics of an ethylbenzene production plant.

Economics of a chemical plant depend on multiple factors: grade of a feed, types of catalyst, operating temperature and pressure, cost of equipment, and many other factors could have influences on economics of the plant. In a previous study about an ethylbenzene facility, our team scrutinize two proposed changes. An optimization plan is recommended by our team in order to maximize the net present value (NPV) of the plant. This report focuses on demonstrating rationales of setting certain operating conditions, showcasing the details of optimization, and elucidating the reasons behind applying these modifications. The team used simulating software PRO/-II to investigate various changes applied, and used CAPCOST for economic estimation. Even though any plant in the real world cannot be perfect, our result is a good starting point for more comprehensive and precise design. After the investigation, we conclude that reaction section, cooling section, recycle, and separating section can be optimized in order to keep the plant working in a highly efficient and effective manner. By manipulating operating conditions and equipment sizing, the entire plant is simplified and the ethylbenzene production process becomes more efficient than the original process. Furthermore, the net present value of the plant is increased dramatically, post-optimization