Influence of ionospheric perturbations in GPS time and frequency transfer

The stability of GPS time and frequency transfer is limited by the fact that GPS signals travel through the ionosphere. In high precision geodetic time transfer (i.e. based on precise modeling of code and carrier phase GPS data), the so-called ionosphere-free combination of the code and carrier phase measurements made on the two frequencies is used to remove the first-order ionospheric effect. In this paper, we investigate the impact of residual second- and third-order ionospheric effects on geodetic time transfer solutions i.e. remote atomic clock comparisons based on GPS measurements, using the ATOMIUM software developed at the Royal Observatory of Belgium (ROB). The impact of third-order ionospheric effects was shown to be negligible, while for second-order effects, the tests performed on different time links and at different epochs show a small impact of the order of some picoseconds, on a quiet day, and up to more than 10 picoseconds in case of high ionospheric activity. The geomagnetic storm of the 30th October 2003 is used to illustrate how space weather products are relevant to understand perturbations in geodetic time and frequency transfer.Comment: 25 pages, 10 eps figures, 1 table, accepted in Journal of Advances in Space Research, Special Issue "Recent advances in space weather monitoring, modelling and forecasting

WSN hardware for automotive applications: Preliminary results for the case of public transportation

The ubiquitous nature and great potential of Wireless Sensors Network has not yet been fully exploited in automotive applications. This work deals with the choice of the cost-effective hardware required to face the challenges and issues proposed by the new trend in the development of intelligent transportation systems. With this aim, a preliminary WSN architecture is proposed. Several commercially available open-source platforms are compared and the Raspberry Pi stood out as a suitable and viable solution. The sensing layer is designed with two goals. Firstly, accelerometric, temperature, and relative humidity sensors were integrated on a dedicated PCB to test if mechanical or environmental stresses during bus rides could be harmful to the device or to its performances. The physical quantities are monitored automatically to alert the driver, thus improving the quality of service. Then, the rationale and functioning of the management and service layer is presented. The proposed cost-effective WSN node was employed and tested to transmit messages and videos, while investigating if any quantitative relationship exists between these operations and the environmental and operative conditions experienced by the hardware

L1\mathcal{L}^1 limit solutions for control systems

For a control Cauchy problem $$\dot x= {f}(t,x,u,v) +\sum_{\alpha=1}^m g_\alpha(x) \dot u_\alpha,\quad x(a)=\bar x,$$ on an interval $[a,b]$, we propose a notion of limit solution $x,$ verifying the following properties: i) $x$ is defined for $\mathcal{L}^1$ (impulsive) inputs $u$ and for standard, bounded measurable, controls $v$; ii) in the commutative case (i.e. when $[g_{\alpha},g_{\beta}]\equiv 0,$ for all $\alpha,\beta=1,...,m$), $x$ coincides with the solution one can obtain via the change of coordinates that makes the $g_\alpha$ simultaneously constant; iii) $x$ subsumes former concepts of solution valid for the generic, noncommutative case. In particular, when $u$ has bounded variation, we investigate the relation between limit solutions and (single-valued) graph completion solutions. Furthermore, we prove consistency with the classical Carath\'eodory solution when $u$ and $x$ are absolutely continuous. Even though some specific problems are better addressed by means of special representations of the solutions, we believe that various theoretical issues call for a unified notion of trajectory. For instance, this is the case of optimal control problems, possibly with state and endpoint constraints, for which no extra assumptions (like e.g. coercivity, bounded variation, commutativity) are made in advance

A Robust SVM Color-Based Food Segmentation Algorithm for the Production Process of a Traditional Carasau Bread

In this paper, we address the problem of automatic image segmentation methods applied to the partial automation of the production process of a traditional Sardinian flatbread called pane Carasau for assuring quality control. The study focuses on one of the most critical activities for obtaining an efficient degree of automation: the estimation of the size and shape of the bread sheets during the production phase, to study the shape variations undergone by the sheet depending on some environmental and production variables. The knowledge can thus be used to create a system capable of predicting the quality of the shape of the dough produced and empower the production process. We implemented an image acquisition system and created an efficient machine learning algorithm, based on support vector machines, for the segmentation and estimation of image measurements for Carasau bread. Experiments demonstrated that the method can successfully achieve accurate segmentation of bread sheets images, ensuring that the dimensions extracted are representative of the sheets coming from the production process. The algorithm proved to be fast and accurate in estimating the size of the bread sheets in various scenarios that occurred over a year of acquisitions. The maximum error committed by the algorithm is equal to the 2.2% of the pixel size in the worst scenario and to 1.2% elsewhere

A wireless sensors network for monitoring the Carasau bread manufacturing process

This work copes with the design and implementation of a wireless sensors network architecture to automatically and continuously monitor, for the first time, the manufacturing process of Sardinian Carasau bread. The case of a traditional bakery company facing the challenge of the Food-Industry 4.0 competitiveness is investigated. The process was analyzed to identify the most relevant variables to be monitored during the product manufacturing. Then, a heterogeneous, multi-tier wireless sensors network was designed and realized to allow the real-time control and the data collection during the critical steps of dough production, sheeting, cutting and leavening. Commercial on-the-shelf and cost-effective integrated electronics were employed, making the proposed approach of interest for many practical cases. Finally, a user-friendly interface was provided to enhance the understanding, control and to favor the process monitoring. With the wireless senors network (WSN) we designed, it is possible to monitor environmental parameters (temperature, relative humidity, gas concentrations); cinematic quantities of the belts; and, through a dedicated image processing system, the morphological characteristics of the bread before the baking. The functioning of the WSN was demonstrated and a statistical analysis was performed on the variables monitored during different seasons

Osiguravanje međuoperabilnosti za Internet stvari: iskustvo s testiranjem CoAP protokola

Constrained Application Protocol (CoAP) is a specialized web transfer protocol, designed for realizing interoperation with constrained networks and nodes for machine to machine applications like smart energy, building automation, etc. As an important ubiquitous application protocol for the future Internet of Things, CoAP will be potentially implemented by a wide range of smart devices to achieve cooperative services. Therefore, a high level of interoperability of CoAP implementations is crucial. In this context, CoAP Plugtest – the first formal CoAP interoperability testing event was held in Paris, March 2012 to motivate vendors to verify the interoperability of their equipments. The event turned to be successful due to our contribution, including the test method and tool. This paper presents the testing method and procedure for the CoAP Plugtest event. To carry out the tests, a set of test objectives concerning the most important properties of CoAP have been selected and used to measure the interoperability of CoAP implementations. The process of verification has been automated by implementing a test validation tool based on the technique of passive testing. By using the test tool, a number of devices were successfully tested.Constrained Application Protocol (CoAP) je specijalizirani prijenosni protokol, dizajniran za realizaciju međuoperabilnosti uz ograničene mrežame i čvorove za primjene poput pametne energije, automatizacije u zgradarstvu itd. Kao važan i sveprisutan protokol za Internet stvari CoAP bi mogao biti implementiran kod velikog broja pametnih uređaja kako bi se ostvarile kooperativne usluge. Zbog toga je od velike važnosti postic´i visoku razinu međuoperabilnosti CoAP implementacija. U tom kontekstu, CoAP Pluqtest - prvo formalno testiranje CoAP međuoperabilnosti je održano u Parizu u ožujku 2012. kako bi se motivirali prodavači da provjere međuoperabilnost svoje opreme. Testiranje je bilo uspješno zahvaljujući našem doprinosu koji uključuje metodu i alate za testiranje. U ovom radu prikazana je metoda i procedura testiranja za CoAP Pluqtest. Kako bi se proveli testovi odabran je skup ciljeva koji se odnose na najvažnija svojstva CoAP protokola i oni su korišteni za mjerenje međuoperabilnosti CoAP implementacija. Proces verifikacije je automatiziran implementacijom alata za provjeru testa koji se temelji na tehnici pasivnog testiranja. Korištenjem alata za testiranje uspješno su testirani brojni uređaji

Calibration Uncertainty of Non-Catching Precipitation Gauges

Precipitation is among the most important meteorological variables for, e.g., meteorological, hydrological, water management and climate studies. In recent years, non-catching precipitation gauges are increasingly adopted in meteorological networks. Despite such growing diffusion, calibration procedures and associated uncertainty budget are not yet standardized or prescribed in best practice documents and standards. This paper reports a metrological study aimed at proposing calibration procedures and completing the uncertainty budgets, to make non-catching precipitation gauge measurements traceable to primary standards. The study is based on the preliminary characterization of different rain drop generators, specifically developed for the investigation. Characterization of different models of non-catching rain gauges is also included

WSN Hardware for Automotive Applications: Preliminary Results for the Case of Public Transportation

The ubiquitous nature and great potential ofWireless Sensors Network has not yet been fully exploited in automotive applications. This work deals with the choice of the cost-effective hardware required to face the challenges and issues proposed by the new trend in the development of intelligent transportation systems. With this aim, a preliminary WSN architecture is proposed. Several commercially available open-source platforms are compared and the Raspberry Pi stood out as a suitable and viable solution. The sensing layer is designed with two goals. Firstly, accelerometric, temperature and relative humidity sensors were integrated on a dedicated PCB to test if mechanical or environmental stresses during bus rides could be harmful to the device. The monitored physical quantities could be used to improve the quality of service. Then, the rationale and functioning of the management and service layer is presented. The proposed cost-effective WSN node is employed and tested to transmit messages and videos