16,576 research outputs found
Nonlinear Blend Scheduling via Inventory Pinch-based Algorithm using Discrete- and Continuous-time Models
This work uses multi-period, inventory pinch-based algorithm with continuous-time model (MPIP-C algorithm1) for scheduling linear or nonlinear blending processes. MPIP-C decomposes the scheduling problem into (i) approximate scheduling and (ii) detailed scheduling. Approximate scheduling model is further decomposed into two parts: a 1st level model which optimizes nonlinear blend models (with time periods delineated by inventory pinch points), and a 2nd level multi-period mixed-integer linear programming model (which uses fixed blend recipes from the 1st level solution) to determine optimal production plan and swing storage allocation, while minimizing the number of blend instances and product changeovers in the swing tanks. The 3rd level computes schedules using a continuous-time model including constraints based on the short-term plan solution. Nonlinear constraints are used for the Reid vapor pressure in our case studies. Excellent computational performance is illustrated by comparisons with previous approach with discrete-time scheduling model
Dynamics and bifurcations in a simple quasispecies model of tumorigenesis
Cancer is a complex disease and thus is complicated to model. However, simple
models that describe the main processes involved in tumoral dynamics, e.g.,
competition and mutation, can give us clues about cancer behaviour, at least
qualitatively, also allowing us to make predictions. Here we analyze a
simplified quasispecies mathematical model given by differential equations
describing the time behaviour of tumor cells populations with different levels
of genomic instability. We find the equilibrium points, also characterizing
their stability and bifurcations focusing on replication and mutation rates. We
identify a transcritical bifurcation at increasing mutation rates of the tumor
cells population. Such a bifurcation involves an scenario with dominance of
healthy cells and impairment of tumor populations. Finally, we characterize the
transient times for this scenario, showing that a slight increase beyond the
critical mutation rate may be enough to have a fast response towards the
desired state (i.e., low tumor populations) during directed mutagenic
therapies
They Have Names, Too: A Case Study on the First Five Victims of the Green River Killer: Examining the Construction of Society and Its Creation of Victim Availability
This case study follows the example of Rubenhold (2019) to examine the lives of the first five women killed by the Green River Killer, to give the victims a voice to tell their stories that Ridgway robbed from them, and to identify the social constructs that influence victim availability. To explore this issue, the study analyzed multiple sources of information: archival sources, monographs, articles, websites, and newspapers. In analyzing the effects of their upbringing—family history, educational backgrounds, and personal lives—this research will clarify the role that these factors played regarding where they spent their last day alive.
Using an intersectional lens helps interpret how these young women’s race, class, and gender were affected by the social system and their vulnerability in society. The qualitative data was beneficial as an explanatory means of the theoretical social constructs and to understand the themes that emerged from this data. This interpretation of these sources helped recognize the constructs that make up for the vulnerability of marginalized populations and why they are high-risk victims.Analyzing individual bodies, experiences, and lives will answer many questions regarding how identity is crucial for how one experiences life
Non-diffusive transport in plasma turbulence: a fractional diffusion approach
Numerical evidence of non-diffusive transport in three-dimensional, resistive
pressure-gradient-driven plasma turbulence is presented. It is shown that the
probability density function (pdf) of test particles' radial displacements is
strongly non-Gaussian and exhibits algebraic decaying tails. To model these
results we propose a macroscopic transport model for the pdf based on the use
of fractional derivatives in space and time, that incorporate in a unified way
space-time non-locality (non-Fickian transport), non-Gaussianity, and
non-diffusive scaling. The fractional diffusion model reproduces the shape, and
space-time scaling of the non-Gaussian pdf of turbulent transport calculations.
The model also reproduces the observed super-diffusive scaling
Chaotic dynamics and superdiffusion in a Hamiltonian system with many degrees of freedom
We discuss recent results obtained for the Hamiltonian Mean Field model. The
model describes a system of N fully-coupled particles in one dimension and
shows a second-order phase transition from a clustered phase to a homogeneous
one when the energy is increased. Strong chaos is found in correspondence to
the critical point on top of a weak chaotic regime which characterizes the
motion at low energies. For a small region around the critical point, we find
anomalous (enhanced) diffusion and L\'evy walks in a transient temporal regime
before the system relaxes to equilibrium.Comment: 7 pages, Latex, 6 figures included, Contributed paper to the Int.
Conf. on "Statistical Mechanics and Strongly Correlated System", 2nd Giovanni
Paladin Memorial, Rome 27-29 September 1999, submitted to Physica
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