Ground-penetrating radar profiles of the McMurdo shear zone, Antarctica, acquired with an unmanned rover : interpretation of crevasses, fractures, and folds within firn and marine ice

The crevassed firn of the McMurdo shear zone (SZ) within the Ross Ice Shelf may also contain crevasses deep within its meteoric and marine ice, but the surface crevassing prevents ordinary vehicle access to investigate its structure geophysically. We used a lightweight robotic vehicle to tow 200- and 40 MHz ground-penetrating radar antennas simultaneously along 10 parallel transects over a 28 km² grid spanning the SZ width. Transects were generally orthogonal to the ice flow. Total firn and meteoric ice thickness was approximately 160 m. Firn crevasses profiled at 400 MHz were up to 16 m wide, under snow bridges up to 10 m thick, and with strikes near 35°–40° to the transect direction. From the top down, 200- MHz profiles revealed firn diffractions originating to a depth of approximately 40 m, no discernible structure within the meteoric ice, a discontinuous transitional horizon, and at least 20 m of stratified marine ice; 28–31 m of freeboard found more marine ice exists. Based on 10 consecutive transects covering approximately 2.5 km², we preliminarily interpreted the transitional horizon to be a thin saline layer, and marine ice hyperbolic diffractions and reflections to be responses to localized fractures, and crevasses filled with unstratified marine ice, all at strikes from 27° to 50°. We preliminarily interpreted off nadir, marine ice horizons to be responses to linear and folded faults, similar to some in firn. The coinciding and synchronously folded areas of fractured firn and marine ice suggested that the visibly unstructured meteoric ice beneath our grid was also fractured, but either never crevassed, crevassed and sutured without marine ice inclusions, or that any ice containing crevasses might have eroded before marine ice accretion. We will test these interpretations with analysis of all transects and by extending our grid and increasing our depth ranges.

Modern Weather Surveillance Radars: Hygienic Aspects of Monitoring Electromagnetic Fields at Operators’ Workplaces and in the Environment

Summary. Introduction: Location of weather surveillance radars near settlements, in residential areas and on airport premises makes it important to ensure safe levels of electromagnetic fields (EMF) when operating these radio transmitters. EMF maximum permissible levels for weather radars developed in the 1980s are outdated. Our objective was to analyze modern weather surveillance radars to develop proposals for improvement of radar-generated radiofrequency field monitoring. Materials and methods: We studied trends in meteorological radiolocation and technical characteristics of modern weather radars for atmospheric sensing and weather alerts, analyzed regulations for EMF measurements and hygienic assessment, and measured radiofrequency fields produced by weather radar antennas in open areas and at workplaces of operators. Results: We established that modern types of weather radars used in upper-air sensing systems and storm warning networks differ significantly in terms of technical characteristics and operating modes from previous generations. Developed in the 1980s, current hygienic standards for human exposures to radiofrequency fields from weather radar antennas are obsolete. Conclusions: It is essential to develop an up-to-date regulatory and method document specifying estimation and instrumental monitoring of EMF levels generated by weather radars and measuring instruments for monitoring of pulse-modulated electromagnetic radiation.

The vibration characteristic and impact analysis of the tunnel lining detection device based on arc rotating multi-section mechanism

In order to overcome the great interference of many ancillary facilities in the process of tunnel lining detection, a vehicle-borne high-speed railway tunnel lining detection device was designed based on the arc rotation mechanism to improve the detection efficiency and quality. The device could automatically maintain the antenna–lining distance and carry three radar antennas at one time, which detected the tunnel from the side of the catenary frame without stopping. Through the establishment of the mechanism three-dimensional finite element model, the simulation and analysis of natural frequency and vibration characteristics were carried out, and the results were confirmed by the field dynamic test. It is concluded that the dynamic characteristics can meet the technical requirements under the radial and the longitudinal vibration at 5 km h−1, but the detection data quality of the three radar antennas under the radial vibration is quite different. After optimizing the bent arm material to carbon fiber, the dynamic stability of the mechanism is significantly improved through simulation analysis and the detection speed can be increased to 10 km h−1 with a substantial leap.

Evaluation of Thermoplastic Vulcanizates in Radomes

The present paper evaluates a thermoplastic vulcanizate (TPV) of polypropylene (PP) and nitrile rubber (NBR), with and without carbon nanotube (CNT), with a potential application in structures that protect radar antennas, radomes. Morphological analysis, izod impact test, electromagnetic properties measurement and S-parameters were performed in order to verify its operational functioning. The presence of CNT affected the morphology of TPV, reducing the size of NBR particles. This enhanced impact strength results, besides the already known reinforcing effect of CNT on polymeric matrices. Electromagnetic parameters showed that both filled and unfilled TPV are low-loss materials. However, better impact result makes the filled TPV the most indicated material for radome application.

Calibration of a Ground-Based Array Radar for Tomographic Imaging of Natural Media

Ground-based tomographic radar measurements provide valuable knowledge about the electromagnetic scattering mechanisms and temporal variations of an observed scene and are essential in preparation for space-borne tomographic synthetic aperture radar (SAR) missions. Due to the short range between the radar antennas and a scene being observed, the tomographic radar observations are affected by several systematic errors. This article deals with the modelling and calibration of three systematic errors: mutual antenna coupling, magnitude and phase errors and the pixel-variant impulse response of the tomographic image. These errors must be compensated for so that the tomographic images represent an undistorted rendering of the scene reflectivity. New calibration methods were described, modelled and validated using experimental data. The proposed methods will be useful for future ground-based tomographic radar experiments in preparation for space-borne SAR missions.

A Review on Methods for Random Motion Detection and Compensation in Bio-Radar Systems

The bio-radar system can measure vital signals accurately, by using the Doppler effect principle, which relates the received signal properties to the distance change between the radar antennas and the subject chest-wall. These systems have countless applications, from short range detection to assist in rescue missions, to long-term applications as for the continuous sleeping monitoring. Once the main applications of these systems intend to monitor subjects during long periods of time and under noisy environments, it is impossible to guarantee the patient immobilization, hence its random motion, as well as other clutter sources, will interfere in the acquired signals. Therefore, the signal processing algorithms developed for these applications have been facing several challenges regarding the random motion detection and mitigation. In this paper, an extended review on the already implemented methods is done, considering continuous wave radars. Several sources of random motion are considered, along with different approaches to compensate the distortions caused by them.

ANALYSIS OF THE STATE OF THE CURRENT ELECTROMAGNETIC SAFETY FOR CREWS OF THE ICEBREAKING FLEET VESSEL

Introduction. The article presents results of a study on the hygienic evaluation of the impact of levels of electromagnetic fields (EMF) from electrical equipment, communications and navigational aids on modern automated ice-breaking vessels to the electromagnetic safety of the crew. Material and methods. The instrumental measurement of EMF levels from power equipment, electronic equipment, computers, were conducted in places of a permanent and temporary stay of the crew watches in parked icebreakers in the port and during sea trials. The assessment of the levels of electromagnetic radiation from the antennas of radio relay stations (radar) was conducted using the forecasting parameters of the EMF. Results. Onboard computers, marine electrical, communications and radar transmitters do not create electromagnetic fields exceeding the RC in crew workplaces of ship premises. Levels of EMF SHF range generated by RADAR antennas on the open deck, also do not exceed RC. Electromagnetic fields exceeding the RC are registered at work communications transmitters VHF, MF/HF on the decks of the installation of antennas transmitting devices. Discussion. There is a relevant matter of the protection of the crew from the EMF generated by the antennas of modern radars. Evaluation of the EMF RADAR intensity is only possible on the basis of data on forecasting levels of the electromagnetic radiation. To protect the crew from the EMF generated by antennas means the marine radio and RADAR on open decks should implement measures to limit exposure time to install warning signs and placards. Conclusions. There is required the improvement of normative-methodical documents in the field of the protection of the crew from the EMF. You must create a measurement technique for recording the intensity of electromagnetic radiation from the radar. Research data can be used for the development of science-based sanitary-epidemiological requirements for electromagnetic safety of the crew.