4,949 research outputs found
Refractive index evaluation of porous silicon using Bragg reflectors
There are two main physical properties needed to fabricate 1D photonic
structures and form perfect photonic bandgaps: the quality of the thickness
periodicity and the refractive index of their components. Porous silicon (PS)
is a nano-structured material widely used to prepare 1D photonic crystals due
to the ease of tuning its porosity and its refractive index by changing the
fabrication conditions. Since the morphology of PS changes with porosity, the
determination of PS's refractive index is no easy task. To find the optical
properties of PS we can use different effective medium approximations (EMA). In
this work we propose a method to evaluate the performance of the refractive
index of PS layers to build photonic Bragg reflectors. Through a quality factor
we measure the agreement between theory and experiment and therein propose a
simple procedure to determine the usability of the refractive indices. We test
the obtained refractive indices in more complicated structures, such as a
broadband Vis-NIR mirror, and by means of a Merit function we find a good
agreement between theory and experiment. With this study we have proposed
quantitative parameters to evaluate the refractive index for PS Bragg
reflectors. This procedure could have an impact on the design and fabrication
of 1D photonic structures for different applications
Transient situations in traffic flow: Modelling the Mexico City Cuernavaca Highway
In this paper a recent variable anticipation cellular automata model for
single-lane traffic flow is extended to analyze the situation of free and
congested flow in the Highway from Mexico City to Cuernavaca. This highway
presents free flow in standard days; but in the returning day of long weekends
or holidays it exhibits congested flow and in rush hours jamming appears. We
illustrate how our CA model for traffic flow can deal appropriately with
transient situations and can be used to search new alternatives that allow to
improve the traffic flow in Mexican highways.Comment: Paper accepted to be published in the Proceedings of Second Mexican
Meeting on Mathematical and Experimental Physics (September 2004), El Colegio
Nacional, Mexico City, Mexic
Electromiograph Study of Patients Treated with Overdentures Retined with Implants
INTRODUCTION: Long Term edentulous patients present severe bone loss in their alveolar ridges, as a consequence there is serious compromise in esthetics and function. A therapeutic alternative which we can offer to these patients is an overdenture retined with dental implants, in order to improve retention and stability.
AIM OF THE WORK: The aim of the study was to determine by electromiography whether the muscular groups involved in masticatory function present any special activity in patients treated with overdentures retined with dental implants.
MATERIAL AND METHODS: We selected ten complete edentulous patients with inferior overdentures retined with two implants and a bar.Myotronics K6-I with eight channels, and registration of anterior and posterior temporalis muscle maseter and dygastric muscles.
We performed recordings in rest positions and maximum force bite.
RESULTS AND CONCLUSION: The results obtained indicate an increase in activity in the rest position of the posterior temporalis group
- ā¦