1,387 research outputs found
Multiphase modeling and qualitative analysis of the growth of tumor cords
In this paper a macroscopic model of tumor cord growth is developed, relying
on the mathematical theory of deformable porous media. Tumor is modeled as a
saturated mixture of proliferating cells, extracellular fluid and extracellular
matrix, that occupies a spatial region close to a blood vessel whence cells get
the nutrient needed for their vital functions. Growth of tumor cells takes
place within a healthy host tissue, which is in turn modeled as a saturated
mixture of non-proliferating cells. Interactions between these two regions are
accounted for as an essential mechanism for the growth of the tumor mass. By
weakening the role of the extracellular matrix, which is regarded as a rigid
non-remodeling scaffold, a system of two partial differential equations is
derived, describing the evolution of the cell volume ratio coupled to the
dynamics of the nutrient, whose higher and lower concentration levels determine
proliferation or death of tumor cells, respectively. Numerical simulations of a
reference two-dimensional problem are shown and commented, and a qualitative
mathematical analysis of some of its key issues is proposed.Comment: 34 pages, 18 figure
Perancangan dan Implementasi Komunikasi RS-485 Menggunakan Protokol Modbus RTU dan Modbus TCP Pada Sistem Pick-By-Light
The industrial process requires high productivity in every activity. An example is a process of taking items in the storage area. The current system is that the operator takes the items by manually searching in the storage. It will cause problems, namely, the process of taking items takes a long time or occurred a mistake in taking items. The purpose of this research is to design a pick-by-light system with RS-485 serial communication and TCP/IP using the Modbus protocol to support efficient production activities. Pick-by-light is a system consisting of a lightweight device as a sign that an item must be taken, a button to confirm that an item has been taken, and a processing device to process data. The result of this research shows that the pick-by-light system can work properly by implementing RS-485 serial communication with the Modbus Protocol and TCP/IP communication with the Modbus TCP protocol. These results are obtained from tests that have been carried out with different communications using RS-485 serial communication and TCP/IP. It can be applied to manufacturing and warehousing industries to increasing the productivity of items taking.Proses di industri membutuhkan produktivitas yang tinggi dalam setiap aktivitasnya. Salah satu contohnya adalah proses pengambilan barang di tempat penyimpanan. Sistem yang ada sekarang adalah operator mengambil barang dengan mencari secara manual ke tempat penyimpanan. Hal tersebut akan menimbulkan masalah yaitu proses pengambilan barang membutuhkan waktu yang lama atau terjadi kesalahan dalam pengambilan barang. Tujuan dari penelitian ini adalah merancang sistem pick-by-light dengan komunikasi serial RS-485 dan TCP/IP menggunakan protokol Modbus untuk mendukung aktivitas produksi yang efisien. Pick-by-light adalah sistem yang terdiri dari perangkat lampu sebagai tanda barang tersebut harus diambil, tombol sebagai konfirmasi bahwa barang sudah diambil, dan perangkat pemroses untuk memproses data. Hasil dari pengujian menunjukkan bahwa sistem pick-by-light dapat berjalan dengan baik dengan menerapkan komunikasi serial RS-485 dengan protokol Modbus RTU dan komunikasi TCP/IP dengan protokol Modbus TCP. Hasil ini didapat dari pengujian yang telah dilakukan dengan komunikasi yang berbeda, yaitu menggunakan komunikasi serial RS-485 dan TCP/IP. Dengan demikian, sistem ini dapat diterapkan pada industri manufaktur maupun pergudangan dalam meningkatkan produktivitas pengambilan barang
A fully-discrete-state kinetic theory approach to traffic flow on road networks
This paper presents a new approach to the modeling of vehicular traffic flows
on road networks based on kinetic equations. While in the literature the
problem has been extensively studied by means of macroscopic hydrodynamic
models, to date there are still not, to the authors' knowledge, contributions
tackling it from a genuine statistical mechanics point of view. Probably one of
the reasons is the higher technical complexity of kinetic traffic models,
further increased in case of several interconnected roads. Here such
difficulties of the theory are overcome by taking advantage of a discrete
structure of the space of microscopic states of the vehicles, which is also
significant in view of including the intrinsic microscopic granularity of the
system in the mesoscopic representation.Comment: 36 pages, 10 figure
Proposal of a risk model for vehicular traffic: A Boltzmann-type kinetic approach
This paper deals with a Boltzmann-type kinetic model describing the interplay
between vehicle dynamics and safety aspects in vehicular traffic. Sticking to
the idea that the macroscopic characteristics of traffic flow, including the
distribution of the driving risk along a road, are ultimately generated by
one-to-one interactions among drivers, the model links the personal (i.e.,
individual) risk to the changes of speeds of single vehicles and implements a
probabilistic description of such microscopic interactions in a Boltzmann-type
collisional operator. By means of suitable statistical moments of the kinetic
distribution function, it is finally possible to recover macroscopic
relationships between the average risk and the road congestion, which show an
interesting and reasonable correlation with the well-known free and congested
phases of the flow of vehicles.Comment: 23 pages, 3 figures, Commun. Math. Sci., 201
Fundamental diagrams for kinetic equations of traffic flow
In this paper we investigate the ability of some recently introduced discrete
kinetic models of vehicular traffic to catch, in their large time behavior,
typical features of theoretical fundamental diagrams. Specifically, we address
the so-called "spatially homogeneous problem" and, in the representative case
of an exploratory model, we study the qualitative properties of its solutions
for a generic number of discrete microstates. This includes, in particular,
asymptotic trends and equilibria, whence fundamental diagrams originate.Comment: 14 page
Comparing first order microscopic and macroscopic crowd models for an increasing number of massive agents
In this paper a comparison between first order microscopic and macroscopic
differential models of crowd dynamics is established for an increasing number
of pedestrians. The novelty is the fact of considering massive agents,
namely particles whose individual mass does not become infinitesimal when
grows. This implies that the total mass of the system is not constant but grows
with . The main result is that the two types of models approach one another
in the limit , provided the strength and/or the domain of
pedestrian interactions are properly modulated by at either scale. This is
consistent with the idea that pedestrians may adapt their interpersonal
attitudes according to the overall level of congestion.Comment: 26 pages, 8 figure
A fully-discrete-state kinetic theory approach to modeling vehicular traffic
This paper presents a new mathematical model of vehicular traffic, based on
the methods of the generalized kinetic theory, in which the space of
microscopic states (position and velocity) of the vehicles is genuinely
discrete. While in the recent literature discrete-velocity kinetic models of
car traffic have already been successfully proposed, this is, to our knowledge,
the first attempt to account for all aspects of the physical granularity of car
flow within the formalism of the aforesaid mathematical theory. Thanks to a
rich but handy structure, the resulting model allows one to easily implement
and simulate various realistic scenarios giving rise to characteristic traffic
phenomena of practical interest (e.g., queue formation due to roadworks or to a
traffic light). Moreover, it is analytically tractable under quite general
assumptions, whereby fundamental properties of the solutions can be rigorously
proved.Comment: 22 pages, 3 figure
Boltzmann-type models with uncertain binary interactions
In this paper we study binary interaction schemes with uncertain parameters
for a general class of Boltzmann-type equations with applications in classical
gas and aggregation dynamics. We consider deterministic (i.e., a priori
averaged) and stochastic kinetic models, corresponding to different ways of
understanding the role of uncertainty in the system dynamics, and compare some
thermodynamic quantities of interest, such as the mean and the energy, which
characterise the asymptotic trends. Furthermore, via suitable scaling
techniques we derive the corresponding deterministic and stochastic
Fokker-Planck equations in order to gain more detailed insights into the
respective asymptotic distributions. We also provide numerical evidences of the
trends estimated theoretically by resorting to recently introduced structure
preserving uncertainty quantification methods
Uncertainty damping in kinetic traffic models by driver-assist controls
In this paper, we propose a kinetic model of traffic flow with uncertain
binary interactions, which explains the scattering of the fundamental diagram
in terms of the macroscopic variability of aggregate quantities, such as the
mean speed and the flux of the vehicles, produced by the microscopic
uncertainty. Moreover, we design control strategies at the level of the
microscopic interactions among the vehicles, by which we prove that it is
possible to dampen the propagation of such an uncertainty across the scales.
Our analytical and numerical results suggest that the aggregate traffic flow
may be made more ordered, hence predictable, by implementing such control
protocols in driver-assist vehicles. Remarkably, they also provide a precise
relationship between a measure of the macroscopic damping of the uncertainty
and the penetration rate of the driver-assist technology in the traffic stream
Reducing complexity of multiagent systems with symmetry breaking: an application to opinion dynamics with polls
In this paper we investigate the possibility of reducing the complexity of a
system composed of a large number of interacting agents, whose dynamics feature
a symmetry breaking. We consider first order stochastic differential equations
describing the behavior of the system at the particle (i.e., Lagrangian) level
and we get its continuous (i.e., Eulerian) counterpart via a kinetic
description. However, the resulting continuous model alone fails to describe
adequately the evolution of the system, due to the loss of granularity which
prevents it from reproducing the symmetry breaking of the particle system. By
suitably coupling the two models we are able to reduce considerably the
necessary number of particles while still keeping the symmetry breaking and
some of its large-scale statistical properties. We describe such a multiscale
technique in the context of opinion dynamics, where the symmetry breaking is
induced by the results of some opinion polls reported by the media
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