High-resolution subglacial topography around Dome Fuji, Antarctica, based on ground-based radar surveys conducted over 30 years

The retrieval of continuous ice core records of more than 1 Myr is an important challenge in palaeo-climatology. For identifying suitable sites for drilling such ice, the knowledge of the subglacial topography and englacial layering is crucial. For this purpose, extensive ground-based ice radar surveys were done over Dome Fuji in the East Antarctic plateau during the 2017–2018 and 2018–2019 austral summers by the Japanese Antarctic Research Expedition, on the basis of ground-based radar surveys conducted over the previous ~ 30 years. High-gain Yagi antennae were used to improve the antenna beam directivity and thus attain a significant decrease in hyperbolic features in the echoes from mountainous ice-bedrock interfaces. We combined the new ice thickness data with the previous ground-based data, recorded since the 1980s, to generate an accurate high-spatial-resolution (up to 0.5 km between survey lines) ice thickness map. This map revealed a complex landscape composed of networks of subglacial valleys and highlands, which sets substantial constraints for identifying possible locations for new drilling. In addition, our map was compared with a few bed maps compiled by earlier independent efforts based on airborne radar data to examine the difference in features between sets of the data.

Investigation of Beam Features of Unidirectional Rayleigh Waves Electromagnetic Acoustic Transducers (EMATs) by a Wholly Analytical Solution

Electromagnetic acoustic transducers (EMATs) are widely used in industries due to its non-contact nature. This paper investigates the beam features of unidirectional Rayleigh waves EMATs, especially the effect of the wire length on beam directivity. A wholly analytical model is developed to calculate the Lorentz force distribution and ultrasound displacement distribution. The modelling results indicate that, compared to the coil consists of shorter wires, the coil consists of longer wires results in a narrower bandwidth of main lobe of unidirectional Rayleigh waves, which means the ultrasound are more concentrated. This study can be used for unidirectional Rayleigh waves EMATs design and optimization.

A Capacitated House Allocation Game for the Energy Efficient Relays Selection in 5G Multicast Context

The upcoming fifth generation (5G) wireless networks making use of higher-frequency spectrum bands suffer from serious propagation issues due to high path loss and beam directivity requirements. This promotes the device-to-device communications to boost the transmission reliability at the network edges, providing remarkable benefits in terms of the energy and spectrum efficiency, essential for a wide class of sensors networks and Internet-of-Things. More in general, applications where devices are usually constrained in computational and transmission range capabilities. In such a context, the selection of the proper number of devices arranged as a relay plays a crucial role. Towards this goal, this paper proposes an efficient relay selection scheme minimizing both the delivery transmission delay and the overall energy consumption, i.e., the overall number of relays to be used. By focusing on a multicast content delivery application scenario the problem of interest is formulated as a one-sided preferences matching game. In addition, the strategy designed takes into account specific information, named reputation coefficient, associated to each device jointly with link propagation conditions for allowing the selection of suitable relays for disseminating the content among the devices. The effectiveness of the proposed solution is underpinned by computer simulations, and the performance is evaluated in terms of power consumption, end-to-end delay, and number of selected relays. As confirmed by results, the proposed approach improves network performance compared to the greedy approach, the random algorithm, a scheme previously proposed in literature, and with two game theory-based strategies.

A Beam Forming Method Based on Amplitude Weighting of Uniform Circular Array

The uniform circular planar array (UCA) has lots of advantages what linear arrays and other surface arrays don't have. However, because of its limitations, such as the high side-lobe level and low zero depth, the application on controlling array space direction by beam forming has been limited. Considering the characteristics of UCA, the receiving UCA's signal model is established in this paper. The influence factors of UCA's beam will be found out on the basis of theoretical derivation. A new method, that can improve the performance of the UCA beam directivity by amplitude weighting, is proposed in this paper. The theoretical derivation results and simulation results improved that the method could have a better ability in side-lobe suppression, and the new method could make the UCA to have a good application prospect.

Focusing Actuating Performance of OPFC Phased Array Transducer Based on DPSM

As a new functional composite material, Orthotropic Piezoelectric Fiber Composite (OPFC) may be developed conveniently actuators and sensors. By constructing multi-element linear array, the phased array transducers can generate special directional strong actuator power and high sensitivity. The advantage of the transducers is that no mechanical movement is needed to scan an object. Focusing beam is obtained simply only by adjusting a parabolic time delay. The DPSM (distributed point source method) is used to model the ultrasonic field by OPFC linear array transducer. Using this approach, beam directivity and pressure distributions are studied to predict the behavior of focusing as compared to current formulation of traditional transducer. The interaction effect of two OPFC phased array transducers is also modeled in the same medium. Which shows the pressure beam produced by the OPFC array transducer is narrower or more collimated than that produced by the conventional transducer at different angles.