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In this article, a D-shaped photonic crystal fiber based surface plasmon resonance sensor is proposed for refractive index sensing. Surface plasmon resonance effect between surface plasmon polariton modes and fiber core modes of the designed D-shaped photonic crystal fiber is used to measure the refractive index of the analyte. By using finite element method, the sensing properties of the proposed sensor are investigated, and a very high average sensitivity of 7700 nm/RIU with the resolution of 1.30 × 10-5 RIU is obtained for the analyte of different refractive indices varies from 1.43 to 1.46. In the proposed sensor, the analyte and coating of gold are placed on the plane surface of the photonic crystal fiber, hence there is no necessity of the filling of voids, thus it is gentle to apply and easy to use. © 2016, Springer Science+Business Media New York.

Abstract
This work addresses the short-term variability of gamma radiation measured continuously at the Eastern North Atlantic (ENA) facility located in the Graciosa island (Azores, 39N; 28W), a fixed site of the Atmospheric Radiation Measurement programme (ARM). The temporal variability of gamma radiation is characterized by occasional anomalies over a slowly-varying signal. Sharp peaks lasting typically 2-4 h are coincident with heavy precipitation and result from the scavenging effect of precipitation bringing radon progeny from the upper levels to the ground surface. However the connection between gamma variability and precipitation is not straightforward as a result of the complex interplay of factors such as the precipitation intensity, the PBL height, the cloud's base height and thickness, or the air mass origin and atmospheric concentration of sub-micron aerosols, which influence the scavenging processes and therefore the concentration of radon progeny. Convective precipitation associated with cumuliform clouds forming under conditions of warming of the ground relative to the air does not produce enhancements in gamma radiation, since the drop growing process is dominated by the fast accretion of liquid water, resulting in the reduction of the concentration of radionuclides by dilution. Events of convective precipitation further contribute to a reduction in gamma counts by inhibiting radon release from the soil surface and by attenuating gamma rays from all gamma-emitting elements on the ground. Anomalies occurring in the absence of precipitation are found to be associated with a diurnal cycle of maximum gamma counts before sunrise decreasing to a minimum in the evening, which are observed in conditions of thermal stability and very weak winds enabling the build-up of near surface radon progeny during the night.

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Current Learning Management Systems (LMS) generically provide virtual places to conduct interactions between students and educators. Chats, forums and other communication mechanisms usually are present in any LMS. In this paper, we propose a tool that can be embedded in any LMS that features some sort of hierarchical communication mechanisms. The proposed system is capable of depicting and analyzing online interactions in an easy to understand social graph. The vertex positioning algorithm is based on social network analysis statistics, taken from the collected interactions, and is able to smoothly present the temporal evolution in order to find communicational patterns and report them to the educator and the students.

Abstract
The increase in life expectancy and the consequent aging of the general population pose, nowadays, major challenges to modern societies. Most elderly people have the usual problems related to old age, like health chronic problems and sensory and cognitive impairments. Besides that, in today’s modern societies, where families have less and less time to look after for their old relatives, the isolation of the elderly is a real concern and a very current problem, which is enhanced if the elders live alone. To solve or, at least, mitigate that problem, it was developed a smart home for elders that is presented and described in this paper. The developed assistive home system, which is based on available technology, can ensure the quality of life, safety and well-being of all older adults that want or desire to live in the comfort of their home, near to their friends and in their neighborhood, instead of living in elder care centers. The proposed solution can record and analyze the elders’ daily routines in order to alert (e.g., e-mails or text messages) the family members and/or social agents (e.g., doctors and caregivers) whenever an unusual situation occurs or when the elder is in danger, provide real-time audio and video when necessary and some comfort features, such as, automatic lighting and temperature control. The relevant events are recorded and maintained in a cloud database, which can be accessed through a dedicated website or by an Internet of Things (IoT) Application Programming Interface (API). Although this type of solution/service is focused in the elderly population, anybody can use it. The developed solution provides comfort and safety to elders and, at the same time, an easier way of monitoring all important events. © Springer International Publishing AG 2017.

Abstract