The aim of this study was to investigate the influence of light source, LED unit and halogen lamp (HL), on the effectiveness of Enforce dual-cured cement cured under a ceramic disc. Three exposure times (60, 80 and 120 s) were also evaluated. Two experimental groups, in which the polymerization of the dual-cured cement was performed through a ceramic disc, and two control groups, in which the polymerization of the dual-cured cement was performed directly without presence of ceramic disc were subdivided into three subgroups (three different exposure times), with five specimens each: G1A- HL 60s; G1B- HL 80s; G1C- HL 120s; G2A- LED 60s; G2B- LED 80s; G2C- LED 120s; and control groups: G3A- HL 60s; G3B- HL 80s; G3C- HL 120s; G4A- LED 60s; G4B- LED 80s and G4C- LED 120s. Cement was applied in a steel matrix (4mm diameter, 1.2mm thickness). In the experimental groups, a ceramic disc was placed on top. The cement was light-cured through the ceramic by a HL and LED, however, the control groups were cured without the ceramic disc. The specimens were stored in a light-proof container at 37ºC for 24 hours, then Vickers hardness was determined. A four-way ANOVA and Tukey test (p£ 0.05) were performed. All specimens cured by LED for 60s showed inferior values compared with the halogen groups. In general, light-curing by LED for 80s and 120s was comparable to halogen groups (60s and 80s) and their control groups. LED technology can be viable for light-curing through conventional ceramic indirect restorations, when curing time is increased in relation to HL curing time.

The aim of this study was to evaluate the polymerization shrinkage and shrinkage stress of composites polymerized with a LED and a quartz tungsten halogen (QTH) light sources. The LED was used in a conventional mode (CM) and the QTH was used in both conventional and pulse-delay modes (PD). The composite resins used were Z100, A110, SureFil and Bisfil 2B (chemical-cured). Composite deformation upon polymerization was measured by the strain gauge method. The shrinkage stress was measured by photoelastic analysis. The polymerization shrinkage data were analyzed statistically using two-way ANOVA and Tukey test (p

In contemporary society, secure communications employing chaotic communication schemes have opened new challenges. Chaotic communication schemes in which signals are spectrally spread, with low power spectral density, become useful to improve resilience against multipath fading, making them increasingly important for indoor applications in the framework of visible light communication (VLC). Here, we will explore the 16-QAM orthogonal shift key in combination with Walsh coded chaotic basis for application of a secure VLC link, used simultaneously for illumination and security-enhanced data transmission. The experimental results are carried out for a 12 Baud symbol rate, indicating a symbol error rate below the FEC hard threshold limit for an optical irradiance higher than 25 mW/cm 2, covering a 1.4 m2 operating area.

Optical domain digital to analog conversion (ODAC) has been proposed recently as a suitable technique able to cope with LED driving requirements and evolved modulation schemes (such as OFDM) in visible light communication systems (VLC). ODAC's concept is based on using groups of LEDs arranged in an array to transmit digital signals. The radiation pattern of these LED groups adds together on the optical domain enabling the transmission of complex signals. Since the LED driving signals are digital signals, both constant current and PWM dimming requirements can be adequately met. This paper addresses the analysis of ODAC error performance over a predefined area. The analysis framework consisted of a multipath communication scenario with a single reflection. In order to better understand the effects due to reflections, the analysis considered low data rate communication systems, thus enabling to neglect the channel input response. Major conclusions ascertain that the effects of LED array arrangement are apparent under near field conditions and that the root mean square error approaches its ideal value, given by LSB/2 as the distance from the source increases.

In this work, we propose a method that employed a smartphone to capture images obtained from a colorimetric spot test to determine ascorbic acid (AA) in Brazilian Amazon native and exotic fruits. The spot test reaction was based on reduction of Fe(III) by AA and further complexation with 1,10-phenanthroline. After optimization, the limit of detection was 8.5 × 10−7 mol L−1. Brazilian Amazon native fruits such as bacuri, cupuaçu, muruci, yellow mombin, as well as others as cashew, mango, orange and passion fruit, were analyzed. In order to determine the accuracy of this method, iodometric titration was used; results were in close agreement with a confidence level of 95% (paired t-test). Moreover, recoveries ranged from 87.1 to 116%. The method is economic, environmentally friendly, and portable, and might useful for small producers and family agriculture businesses unable to afford specialized laboratory analysis in the north region of Brazilian Amazon.

The aim of this study was to investigate the influence of light source, LED unit and halogen lamp (HL), on the effectiveness of Enforce dual-cured cement cured under a ceramic disc. Three exposure times (60, 80 and 120 s) were also evaluated. Two experimental groups, in which the polymerization of the dual-cured cement was performed through a ceramic disc, and two control groups, in which the polymerization of the dual-cured cement was performed directly without presence of ceramic disc were subdivided into three subgroups (three different exposure times), with five specimens each: G1A- HL 60s; G1B- HL 80s; G1C- HL 120s; G2A- LED 60s; G2B- LED 80s; G2C- LED 120s; and control groups: G3A- HL 60s; G3B- HL 80s; G3C- HL 120s; G4A- LED 60s; G4B- LED 80s and G4C- LED 120s. Cement was applied in a steel matrix (4mm diameter, 1.2mm thickness). In the experimental groups, a ceramic disc was placed on top. The cement was light-cured through the ceramic by a HL and LED, however, the control groups were cured without the ceramic disc. The specimens were stored in a light-proof container at 37ºC for 24 hours, then Vickers hardness was determined. A four-way ANOVA and Tukey test (p£ 0.05) were performed. All specimens cured by LED for 60s showed inferior values compared with the halogen groups. In general, light-curing by LED for 80s and 120s was comparable to halogen groups (60s and 80s) and their control groups. LED technology can be viable for light-curing through conventional ceramic indirect restorations, when curing time is increased in relation to HL curing time.

The aim of this study was to evaluate the polymerization shrinkage and shrinkage stress of composites polymerized with a LED and a quartz tungsten halogen (QTH) light sources. The LED was used in a conventional mode (CM) and the QTH was used in both conventional and pulse-delay modes (PD). The composite resins used were Z100, A110, SureFil and Bisfil 2B (chemical-cured). Composite deformation upon polymerization was measured by the strain gauge method. The shrinkage stress was measured by photoelastic analysis. The polymerization shrinkage data were analyzed statistically using two-way ANOVA and Tukey test (p<0.05), and the stress data were analyzed by one-way ANOVA and Tukey's test (p<0.05). Shrinkage and stress means of Bisfil 2B were statistically significant lower than those of Z100, A110 and SureFil. In general, the PD mode reduced the contraction and the stress values when compared to CM. LED generated the same stress as QTH in conventional mode. Regardless of the activation mode, SureFil produced lower contraction and stress values than the other light-cured resins. Conversely, Z100 and A110 produced the greatest contraction and stress values. As expected, the chemically cured resin generated lower shrinkage and stress than the light-cured resins. In conclusion, The PD mode effectively decreased contraction stress for Z100 and A110. Development of stress in light-cured resins depended on the shrinkage value.

The aim of this study was to evaluate the diametrical tensile strength (DTS) of three light-curing photo-activated composites with two different light curing units (LCU). Three types of dental restorative composites were used in this study: micro filled A110 (3M Espe); P60 (3M Espe) for posterior restorations, and micro-hybrid Charisma (Heraeus-Kulzer). The two LCUs were: halogen light (HAL) (Degulux, Degussa) and blue light emitting diode (LED) (Ultrablue, DMC). Resin composite specimens were inserted incrementally into a Teflon split mold meas-uring 3 mm in depth and 6 mm in internal diameter, and cured using either LCU (n = 10). Specimens were placed into a dark bottle containing distilled water at 37°C for 7 days. DTS tests were performed in a Universal Testing Machine (0.5 mm/min). Data were submitted to two-way ANOVA and Tukey's test. Results were (MPa): A110/HAL: 276.50 ± 62.94ª; A110/LED: 306.01 ± 65.16ª; P60/HAL: 568.29 ± 60.77b and P60/LED: 543.01 ± 83.65b; Charisma/HAL: 430.94 ± 67.28c; Charisma/LED: 435.52 ± 105.12c. Results suggested that no significant difference in DTS was obtained with LCUs for the same composite. However, resin composite restorative materials presented different DTS.

This research suggests the preparation of an efficient street lighting (IP) project, taking into account the technical-financial feasibility of the luminaires that make up the IP system in Rosana city. the study is presented to raise the saving potential in the consumption of electrical energy and in the amount paid monthly with ip. the work's purpose is to replace conventional luminaires (sodium steam), which has a short median life and greater energy consumption, by led luminaires (Light Emitting Diode) which have a longer average lifespan and are more efficient. The economic analysis was done based on standard indicators of investment feasibility, such as net present value (VPL), discounted payback and internal rate of return (TIR). Finally, presents data analysis with the purpose of optimizing the sl system and reducing electric energy consumption in the Rosana city.