Emerging frustration effects in ferromagnetic Ce_2[Pd_{1-x}Ag_x]_2In alloys

Magnetic and thermal properties of Ferromagnetic (FM) Ce_{2.15}(Pd_{1-x}Ag_x)_{1.95}In_{0.9} alloys were studied in order to determine the Quantum Critical Point (QCP) at T_C => 0. The increase of band electrons produced by Pd/Ag substitution depresses T_C(x) from 4.1K down to T_C(x=0.5)=1.1K, with a QCP extrapolated to x_{QCP}~ 0.6. Magnetic susceptibility from T>30K indicates an effective moment slightly decreasing from \mu_{eff}=2.56\mu_B to 2.4\mu_B at x=0.5. These values and the paramagnetic temperature \theta_P~ -10K exclude significant Kondo screening effects. The T_C(x) reduction is accompanied by a weakening of the FM magnetization and the emergence of a specific heat C_m(T) anomaly at T*~ 1K, without signs of magnetism detected from AC-susceptibility. The magnetic entropy collected around 4K (i.e. the T_C of the x=0 sample) practically does not change with Ag concentration: S_m(4K)~ 0.8 Rln2, suggesting a progressive transfer of FM degrees of freedom to the non-magnetic (NM) component. No antecedent was found concerning any NM anomaly emerging from a FM system at such temperature. The origin of this anomaly is attributed to an 'entropy bottleneck' originated in the nearly divergent power law dependence for T>T*.Comment: 5 pages, 4 figures, Int. Conf. ICM 201

Suppression of Shastry-Sutherland phase driven by electronic concentration reduction in magnetically frustrated Ce2Pd2Sn1−yIny alloys

Exploiting the possibility to switch from antiferromagnetic (AFM) and ferromagnetic (FM) ground states (GSs) in out-stoichiometric branches of Ce2Pd2In alloys, the stability of Shastry-Sutherland (ShSu) phase of Ce2Pd2Sn as a function of Sn/In electron doping was studied. Magnetic and specific-heat measurements show that the Ce-rich compositions stabilize the FM-GS throughout the Sn/In-FM substitution, allowing to extend the formation of the ShSu phase up to its collapse in a tricritical point around ycr=0.5. On the other hand, this behavior is quite different from that reported in a recent investigation on the AFM branch where atomic disorder at intermediate Sn/In-AFM concentrations inhibits the formation of the ShSu phase.Fil: Sereni, Julian Gustavo Renzo. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Roberts, J.. Università degli Studi di Genova; ItaliaFil: Gastaldo, F.. Università degli Studi di Genova; ItaliaFil: Giovannini, M.. Università degli Studi di Genova; Itali

Unsupervised Monitoring System for Predictive Maintenance of High Voltage Apparatus

The online monitoring of a high voltage apparatus is a crucial aspect for a predictive maintenanceprogram. Partialdischarges(PDs)phenomenaaffecttheinsulationsystemofanelectrical machine and\u2014in the long term\u2014can lead to a breakdown, with a consequent, signi\ufb01cant economic loss; wind turbines provide an excellent example. Embedded solutions are therefore required to monitor the insulation status. The paper presents an online system that adopts unsupervised methodologies for assessing the condition of the monitored machine in real time. The monitoring process does not rely on any prior knowledge about the apparatus; nonetheless, the method can identify the relevant drifts in the machine status. In addition, the system is speci\ufb01cally designed to run on low-cost embedded devices

Active haptic perception in robots: a review

In the past few years a new scenario for robot-based applications has emerged. Service and mobile robots have opened new market niches. Also, new frameworks for shop-floor robot applications have been developed. In all these contexts, robots are requested to perform tasks within open-ended conditions, possibly dynamically varying. These new requirements ask also for a change of paradigm in the design of robots: on-line and safe feedback motion control becomes the core of modern robot systems. Future robots will learn autonomously, interact safely and possess qualities like self-maintenance. Attaining these features would have been relatively easy if a complete model of the environment was available, and if the robot actuators could execute motion commands perfectly relative to this model. Unfortunately, a complete world model is not available and robots have to plan and execute the tasks in the presence of environmental uncertainties which makes sensing an important component of new generation robots. For this reason, today\u2019s new generation robots are equipped with more and more sensing components, and consequently they are ready to actively deal with the high complexity of the real world. Complex sensorimotor tasks such as exploration require coordination between the motor system and the sensory feedback. For robot control purposes, sensory feedback should be adequately organized in terms of relevant features and the associated data representation. In this paper, we propose an overall functional picture linking sensing to action in closed-loop sensorimotor control of robots for touch (hands, fingers). Basic qualities of haptic perception in humans inspire the models and categories comprising the proposed classification. The objective is to provide a reasoned, principled perspective on the connections between different taxonomies used in the Robotics and human haptic literature. The specific case of active exploration is chosen to ground interesting use cases. Two reasons motivate this choice. First, in the literature on haptics, exploration has been treated only to a limited extent compared to grasping and manipulation. Second, exploration involves specific robot behaviors that exploit distributed and heterogeneous sensory data

Enhancing Cyber Security of LoRaWAN Gateways under Adversarial Attacks

The Internet of Things (IoT) has disrupted the IT landscape drastically, and Long Range Wide Area Network (LoRaWAN) is one specification that enables these IoT devices to have access to the Internet. Former security analyses have suggested that the gateways in LoRaWAN in their current state are susceptible to a wide variety of malicious attacks, which can be notoriously difficult to mitigate since gateways are seen as obedient relays by design. These attacks, if not addressed, can cause malfunctions and loss of efficiency in the network traffic. As a solution to this unique problem, this paper presents a novel certificate authentication technique that enhances the cyber security of gateways in the LoRaWAN network. The proposed technique considers a public key infrastructure (PKI) solution that considers a two-tier certificate authority (CA) setup, such as a root-CA and intermediate-CA. This solution is promising, as the simulation results validate that about 66.67% of the packets that are arriving from an illegitimate gateway (GW) are discarded in our implemented secure and reliable solution