Optical demultiplexer device operating in the visible spectrum

In this paper, we present results on the use of multilayered a-SiC:H heterostructures as a device for wavelength-division demultiplexing of optical signals. These devices are useful in optical communications applications that use the wavelength division multiplexing technique to encode multiple signals into the same transmission medium. The device is composed of two stacked p-i-n photodiodes, both optimized for the selective collection of photo generated carriers. Band gap engineering was used to adjust the photogeneration and recombination rate profiles of the intrinsic absorber regions of each photodiode to short and long wavelength absorption in the visible spectrum. The photocurrent signal using different input optical channels was analyzed at reverse and forward bias and under steady state illumination. A demux algorithm based on the voltage controlled sensitivity of the device was proposed and tested. An electrical model of the WDM device is presented and supported by the solution of the respective circuit equations

Preparation and Characterization of a-SiC:H Absorber Layer for Semi-transparent Solar Cells

AbstractThis paper reports on device-quality silicon-carbon alloy (a-SiC:H) application as an absorber material in semi-transparent solar cells. Films with an optical bandgap ranging from 2 to 2.3 eV were prepared by plasma enhanced chemical vapour deposition (PECVD). The n-i-p structures with undoped SiC:H layers deposited under the same experimental conditions were also fabricated and characterized. The optimized devices showed forward current-voltage characteristics with a diode ideality factor in the range from 1.4 to 1.8, and an open circuit voltage up to 0.92 V. The density of deep defect states in a SiC:H was estimated from the transient current measurements and correlated with the optical bandgap

Effects of alkaline and acid solutions on glass/epoxy composites

Composite structures can be exposed to a range of corrosive environments during their in-service life, which causes degradation in terms of material properties. The effect of alkaline and acid solutions on the GRP mechanical properties can be found in open literature, but the studies presented are not sufficient to establish a full knowledge of this subject. In this paper the flexural properties and the impact strength of a glass fibre/epoxy composite after immersion in hydrochloric acid (HCl) and sodium hydroxide (NaOH) were analysed. Independently of the solution, the flexural strength and the flexural modulus decrease with the exposure time. However, alkaline solution promotes higher decrease of the flexural properties than the acid solution. The same tendency was observed for impact strength

Stationary roller versus velodrome for maximal cycling test: a comparison

The present study aimed to compare the acute cardio-respiratory responses of elite cyclists to a maximal progressive exercise carried out in two different conditions: in a laboratory (using a braked roller) and in an uncovered velodrome. In both testing conditions, ten elite male cyclists (age, 22.3 ± 3.9 years) performed a maximal discontinuous progressive test of 6 minutes per level with 150 W of initial load and increasing 50 W at each level until exhaustion. The heart rate and the ventilation parameters were measured breath-by-breath using a portable metabolic cart gas analysis system with telemetry data transmission. In the first 4 levels of effort, no significant differences were found between the two test conditions regarding VO2, (p=0.193), heart rate (p=0.973) and pedaling cadence (p=0.116). Comparing the maximum values achieved by each athlete in both exercise conditions, significant differences were found for heart rate (p=0.008) and pedaling cadence (p=0.005) but not for VO2max and peak power. Each variable showed a strong correlation between both assessments (VO2, r=0.984, p=0,000; heart rate, r=0.944, p=0.005; pedaling cadence, r=0.900, p=0.014). The amount of variability explained by the linear regression model for both cardio-respiratory parameters also showed a good fit value close to one (VO2max, r2=0.968; heart rate, r2=0.892). Our results suggest that identical cycling protocols conducted in different testing conditions with the same bike leads to equivalent performance but significantly different pedaling cadence and heart rate responses

Automated Guidance Vehicles Controlled by Visible ​Light Communication

The advent of devices with wireless communication capabilities has generated increased interest in indoor navigation. Several wireless technologies have been proposed for indoor location, as the traditional Global Positioning System has a poor performance in a closed space. This research proposes the use of an indoor localization system based on Visible Light Communication (VLC) to support guidance and operational tasks of Autonomous Guided Vehicles (AVG). The research is focused on the development of the guidance VLC system, transmission of control data information and decoding techniques. Trichromatic white LEDs are used as transmitters and photodiodes with selective spectral sensitivity are used as receivers. The downlink channel establishes an infrastructure-to-vehicle link (I2V) and provides position information to the vehicle. The decoding strategy is based on accurate calibration of the output signal. Characterization of the transmitters and receivers, description of the coding schemes and the use of different modulations will be discussed

Enhancing Building Guidance: A Visible Light Communication-based Identifier (ID) System

This paper introduces an innovative approach employing Visible Light Communication (VLC) to generate landmark-based routes and alert instructions, enhancing support for individuals during wayfinding activities. The system utilizes ceiling luminaries as transmitters, broadcasting map information, alerts, and path messages. Through real-time data collection by optical receivers, users are provided with the most efficient routes to navigate around congestion. Tetrachromatic identifier white sources are employed for lighting, featuring various data channels. Data is encoded, modulated, and transformed into light signals, with mobile optical receivers capturing and interpreting this information, allowing users to interact bidirectionally. The system calculates optimal routes for static or dynamic destinations, including buddy wayfinding services. Results demonstrate the system's capability to enable self-location, deduce travel direction, and facilitate efficient navigation towards both static and dynamic locations

Development of new decorative coatings based on gold nanoparticles dispersed in an amorphous TiO2 dielectric matrix

The present work is devoted to the optical properties of Au:TiO2 thin films in order to clarify the role of the Au clusters inclusions in the TiO2 dielectric matrix. Three series of films containing about 30 at.% (29.2), 20 at. % (19.8) and 10 at.% (9.3) Au were deposited by dc reactive magnetron sputtering. On thermal annealing in the range from 300 to 800 °C in protective atmosphere, significant changes on the crystalline phases and clusters dimensions were detected. The most promising optical behavior was found for the film 20% Au:TiO2, where the films revealed some colour changes, evolving from several shades of grey to different tones of red. This change in the optical behaviour of the films was found to be correlated with a cluster size increase from 2 to 17 nm. For higher size values (>20 nm) the films, independently of the Au content, showed a golden appearance colour. The optical changes were confirmed by reflectivity and CIELab colour measurements. Regarding the films with 10 and 30 at.% Au, the results confirmed that there is an evident range of compositions and clusters size where the SPR is more evident. Sample A (10 at.% Au) it seems to be in the lower limit of the SPR showing a typical interferometric behavior on the reflectivity measurements, similar to the TiO2 optical behavior. Regarding the 30 at.% Au one, the results seems to indicate that the amount of gold particles and their grain size is in the upper limit to show a SPR activity.Fundação para a Ciência e Tecnologia (FCT) - PTDC/CTM/70037/200

Palliative splenic irradiation for symptomatic splenomegaly in non-Hodgkin lymphoma

INTRODUCTION AND AIMS: Splenic marginal zone lymphoma, an uncommon subtype of non-Hodgkin lymphoma (NHL), is usually present with symptomatic splenomegaly. Although splenectomy has long been considered the first-line therapy in symptomatic or cytopenic patients, it can lead to significant morbidity and mortality. Splenic irradiation is an option for patients who have a poor response to systemic therapy and/or are not surgical candidates. In this paper, we present a case report of a patient who received splenic radiotherapy for symptomatic splenomegaly. METHODS: An 85-year-old Caucasian man with a 4 year history of low-grade NHL presented with progressive pancytopenia, significant weight loss and symptomatic splenomegaly (abdominal discomfort, sense of fullness and limitation of mobility due to spleen size). The patient refused splenectomy and, in December 2017, was referred to palliative splenic radiotherapy. He was initially treated with five fractions of one Grey (Gy) in order to evaluate clinical and haematology response. After that, 1.5 Gy daily, 5 days a week for 3 weeks. 3D conformal radiotherapy, multiple fields and mixed energy (6 and 15 Mv) were used. RESULTS: Radiotherapy allowed significant splenic reduction to almost half the size, resolving abdominal discomfort and improving quality of life. There was no decline of haemoglobin, leukocytes and platelet counts; in fact, there was a marginal increase. CONCLUSION: Palliative splenic irradiation was well tolerated confirming that it is a safe treatment option for palliation of symptomatic splenomegaly. Thereby, splenic irradiation should be strongly considered in the management of symptomatic splenomegaly, for selected patients who are refractory to or unsuitable for other options or when the patient refuses other treatments.info:eu-repo/semantics/publishedVersio