Development of mathematical model for multi-user coded-cooperation based cognitive radio system and its outage probability analysis

In this paper, single and multi-user coded-cooperation based cognitive radio system is developed by designing its mathematical model where both source and relay will communicate to a single destination with the help of each other. Then all possible multi-user scenarios are developed and their end-to-end outage probability (Pout) is calculated for underlay mode of cognitive radio. The performance of the system is analyzed in the form of channel gain and interference temperature constraint for Rayleigh fading channel. The proposed system concludes that the coded cooperation with cognitive radio outperform the available techniques in the form of bandwidth, diversity, spectrum utilization efficiency and also improves the quality of communication. Furthermore, the theoretical analysis of the outage probability for both system models is validated by asymptotic analysis. The proposed system can set as a standard for all those cognitive radio applications which requires better spectrum efficiency even if there is a scarcity of multiple physical antennas.

A design concept of active cooling for tailored forming workpieces during induction heating

The demand for lightweight construction is constantly increasing. One approach to meet this challenge is the development of hybrid components made of dissimilar materials. The use of the hybrid construction method for bulk components has a high potential for weight reduction and increased functionality. However, forming workpieces consisting of dissimilar materials requires specific temperature profiles for achieving sufficient formability. This paper deals with the development of a specific heating and cooling strategy to generate an inhomogeneous temperature distribution in hybrid workpieces. Firstly, the heating process boundaries with regard to temperature parameters required for a successful forming are experimentally defined. Secondly, a design based on the obtained cooling strategy is developed. Next a modelling embedded within an electro-thermal framework provides the basis for a numerical determination of admissible cooling rates to fulfil the temperature constraint. Here, the authors illustrate an algorithmic approach for the optimisation of cooling parameters towards an effective minimum, required for applicable forming processes of tailored forming.

Female fiddler crabs, Austruca lactea (Decapoda: Ocypodidae), adjust their rate of mate sampling based on remaining days until oviposition under a size-dependent temperature constraint

Rate of mate sampling is one of the critical components associated with sampling costs in female mate choice. In ectotherms, environmental temperature generally constrains locomotion performance. In addition, females will adjust the mate sampling rate depending on their breeding schedule because of the risk of remaining unfertilized eggs or a loss of benefits related to mating, if they lose the opportunity to copulate. This study investigated how these effects influence the rate of female mate sampling in the temperate fiddler crab (Austruca lactea) in the field. The number of sampled males per searching duration formed a convex curve against environmental temperature. The optimal environmental temperature increased with the female body size. These results suggest that mate sampling rate is under a size-dependent temperature constraint, and sampling costs are lower for larger females than smaller individuals under high-temperature conditions. Furthermore, when there were fewer remaining days, the mate sampling rate increased. Females would hasten the sampling rate to ensure a suitable burrow for breeding. Mate sampling rate in female A. lactea is therefore associated with environmental temperature, female body size and remaining days until oviposition.

CFD Preliminary Assessment of the ALFRED FA Thermal-Hydraulics

In the context of GEN-IV heavy liquid metal-cooled reactors safety studies, the coolability of the Fuel Assembly in nominal condition is of central interest. The Advanced Lead-cooled Fast Reactor European Demonstrator (ALFRED) is a 300 MWth pool-type reactor aimed at demonstrating the safe deployment of the Generation IV LFR technology. The ALFRED design, currently being developed by the Fostering ALFRED Construction international consortium, is based on prototypical solutions intended to be used in the next generation of lead-cooled Small Modular Reactors. Within the scope of FALCON and in the frame of investigating the thermal-hydraulics of the ALFRED core, a CFD computational model of the general Fuel Assembly (FA) is built looking for the assessment of its thermal field in nominal flow conditions both for the average FA and the hottest one. Starting from the experience in this kind of simulations and in experimental work, the whole model of the ALFRED Fuel Assembly is first presented and calculation of flow and temperature field in nominal conditions is carried out. Results showed that the thermal hydraulic field predicted in the average FA by the code is in good agreement with analytical correlations and the temperature field on the pin clad is acceptable for clad material temperature constraint. About the results on the hot FA test case, the CFD results highlighted a peak temperature on the clad close to the clad temperature constraint. This result led to an upgrade of the mass flow distribution among the FA for achieving a 20% mass flow increase in the hottest one that guarantees higher temperature margin on the clad.

Robust proactive eavesdropping in UAV-enabled wireless communication networking

In this paper, we considered a robust beamforming design problem for a proactive eavesdropping via jamming, in which a full-duplex legitimate monitor tries to eavesdrop on a suspicious communication link between the secondary pairs in an unmanned aerial vehicle (UAV)-enabled cognitive radio network. Due to the channel estimation errors, we assume that the channel state information is not perfectly known. To ensure the successful eavesdropping, jamming signals are designed to disrupt the suspicious receivers and the primary receiver at the same time, which should have the good tradeoff between those two effects. We aimed to maximize the achievable eavesdropping rate under the transmitting power constraint at the legitimate monitor and the interference temperature constraint at the primary receiver, which was formulated as a non-convex problem with infinite constraints. We firstly transform the original problem into a simplified one with finite constraints. Then, an analytical solution in significant low-complexity is proposed by decomposing the simplified problem. Numerical results are finally presented to evaluate the performance of our proposed schemes in UAV-enabled wireless communication networking.

On the Performance of Random Cognitive mmWave Sensor Networks

This paper investigates the secrecy performance of a cognitive millimeter wave (mmWave) wiretap sensor network, where the secondary transmitter (SU-Tx) intends to communicate with a secondary sensor node under the interference temperature constraint of the primary sensor node. We consider that the random-location eavesdroppers may reside in the signal beam of the secondary network, so that confidential information can still be intercepted. Also, the interference to the primary network is one of the critical issues when the signal beam of the secondary network is aligned with the primary sensor node. Key features of mmWave networks, such as large number of antennas, variable propagation law and sensitivity to blockages, are taken into consideration. Moreover, an eavesdropper-exclusion sector guard zone around SU-Tx is introduced to improve the secrecy performance of the secondary network. By using stochastic geometry, closed-form expression for secrecy throughput (ST) achieved by the secondary sensor node is obtained to investigate secrecy performance. We also carry out the asymptotic analysis to facilitate the performance evaluation in the high transmit power region. Numerical results demonstrate that the interference temperature constraint of the primary sensor node enables us to balance secrecy performance of the secondary network, and provides interesting insights into how the system performance of the secondary network that is influenced by various system parameters: eavesdropper density, antenna gain and sector guard zone radius. Furthermore, blockages are beneficial to improve ST of the secondary sensor node under certain conditions.