SNOW MICROWAVE REFLECTION AT MOBILE PHONE FREQUENCY BANDS

Snow should be accounted in electromagnetic fields' risk assessment, especially in Nordic countries where in winter months snow precipitation and coverage may significantly affect the propagation of microwaves. The risk assessment should be always carried out under worst case scenario conditions, including the reflective properties of the surfaces surrounding the antenna. In this study fresh snow microwave reflectance properties were investigated at the mobile communication bands from 1700 to 2700 MHz.The investigation revealed that reflection loss from snow is more dependent from the frequency than from the thickness of snow coverage. Amongst mobile communication bands, the strongest microwave reflection (reflection loss only 3.2dB) was registered at WiFi2G band. Averaging all the snow thicknesses, the highest reflection loss occurs at GSM1800UL (1710-1785 MHz) and UMTS2100DL (2110-2170 MHz) bands. The least attenuation of reflection occurs in adjacent DECT band

Cluster approach in organization of transportation in the Baltic Sea Region

The urgency of the issues discussed in this paper stems from the fact that cross-border collaboration is an essential part of commercial transportation today. With the extension of multimodal transportation concept, the efficiency and performance of not only national but also of regional transport systems depend on a synergy which occurs as a result of cooperation between transport enterprises and different modes of transport. The present study analyses the situation of transportation field in the Baltic Sea Region (BSR) in the period 2004–2011. The methodology used is based on Hierarchical Cluster Analysis (HCA), correlation analysis, Bayesian analysis and affinity analysis, which help to identify countries with similar trends in the field of transportation and the common reasons and factors which have led to the emergence of these clusters. First published online: 14 Jan 201

AERATED CONCRETE MICROWAVE REFLECTION AND TRANSMISSION PROPERTIES IN A WET ENVIRONMENT

Excess water content within the building material could greatly alter the interaction of the microwave with the material. In this study aerated concrete (AEROC) block walls (60x60cm) were investigated for their microwave (2.4 GHz) properties under wetting conditions. The spray wetting of the wall was conducted to simulate the environmental processes such as raining or water damage. 50ml/m² water dosage was applied on the surface of the concrete 21 times in 1 min intervals. The results show a noticeable decrease in microwave penetration power through the material after the sample gets enriched with water. As the water content on the surface of the material rises, so does the transmission loss. During the different water content of the aerated concrete, the reflection loss varied from -15.04 dB (dry wall) to -5.03 dB (wet wall’s surface). The transmission loss continues to rise during the entire length of the experiment, from -4.5 dB as a dry sample to -8.3 dB after 441 ml (1035 ml/m² during 23 min) of sprayed water. The variation of reflected microwave power was approximately ten times, which is quite a significant indicator of alteration of microwave propagation. The results demonstrate wetting process as an considerable factor in assessing microwave propagation in near the sources, such as mobile phone base station antennas, industrial microwave heaters and ovens etc

Evaluating Chatbots to Promote Users' Trust -- Practices and Open Problems

Chatbots, the common moniker for collaborative assistants, are Artificial Intelligence (AI) software that enables people to naturally interact with them to get tasks done. Although chatbots have been studied since the dawn of AI, they have particularly caught the imagination of the public and businesses since the launch of easy-to-use and general-purpose Large Language Model-based chatbots like ChatGPT. As businesses look towards chatbots as a potential technology to engage users, who may be end customers, suppliers, or even their own employees, proper testing of chatbots is important to address and mitigate issues of trust related to service or product performance, user satisfaction and long-term unintended consequences for society. This paper reviews current practices for chatbot testing, identifies gaps as open problems in pursuit of user trust, and outlines a path forward

Safety Management of Electromagnetic Fields in the Work Environment. Elektromagnetv\ue4ljade ohutusjuhtimine t\uf6\uf6kohtadel

Doctoral thesis 11/2019 Doktorit\uf6\uf6 11/201

Dynamic Lighting System for Workplaces at Northern Latitudes

In this article the author analyzes quality parameters of the ergonomic lighting systems and forms a model of an ideal indoor lighting. Based on the literature review and author’s measurements of the natural daylight, the model’s principal features are 1) dynamic spectrum and 2) dynamic color temperature. The model prescribes these parameters to follow the characteristics of the natural daylight in the course of a day and throughout the year. The relevance of these parameters and the connection to human wellbeing is argued in support to the model

The Shielding of Inbound Radiofrequency Electromagnetic Fields at Workplaces

The emergence of new technologies and increased use of wireless voice and data transmissions has increased the human exposure to the radiofrequency (RF) electromagnetic fields (EMFs). Effective reduction measures of these fields have become more relevant in risk management at workplaces. Not only occupational health, but also counter-espionage and low electromagnetic interference are important arguments for RF EMF mitigation. This study investigates the most commonly used mitigation materials and methods of RF EMFs. The materials investigated in this study included: a graphite based paint; a wire netting; a foil paper; a metalized fabric; a transparent conductive film and other solutions. The study undertook two kinds of measurements: 1) a semi-controlled environment was created to test the mitigation materials/methods under equal conditions, 2) measurements were conducted before and after the implementation of the intervention measures in the actual living and working environments. The results revealed great differences in various mitigation materials and methods: under semicontrolled conditions the best shielding capability was achieved by metallized fabric, followed by iron wire netting and foil paper. Iron bars produced moderate screening whereas graphite paint and metallic frame proved to have little effect

The Shielding of Inbound Radiofrequency Electromagnetic Fields at Workplaces

The emergence of new technologies and increased use of wireless voice and data transmissions has increased the human exposure to the radiofrequency (RF) electromagnetic fields (EMFs). Effective reduction measures of these fields have become more relevant in risk management at workplaces. Not only occupational health, but also counter-espionage and low electromagnetic interference are important arguments for RF EMF mitigation. This study investigates the most commonly used mitigation materials and methods of RF EMFs. The materials investigated in this study included: a graphite based paint; a wire netting; a foil paper; a metalized fabric; a transparent conductive film and other solutions. The study undertook two kinds of measurements: 1) a semi-controlled environment was created to test the mitigation materials/methods under equal conditions, 2) measurements were conducted before and after the implementation of the intervention measures in the actual living and working environments. The results revealed great differences in various mitigation materials and methods: under semicontrolled conditions the best shielding capability was achieved by metallized fabric, followed by iron wire netting and foil paper. Iron bars produced moderate screening whereas graphite paint and metallic frame proved to have little effect

The New Occupational Electromagnetic Fields' Directive 2013/35/EU Compared to the Existing Estonian National Legislation

The electromagnetic fields are classified as “emerging health risks”. The emergence of new radiofrequency technologies has introduced some of the labor force to new types of electromagnetic fields’ exposure. In 2013 a new European directive (2013/35/EU) was released to provide European Union workers with a comprehensive set of protective principles against the electromagnetic fields. The European Union member states should harmonize their national legislation to the new directive by 2016. The current paper analyses the differences in the Estonian existing occupational electromagnetic fields reference values compared to the ones’ in the new directive. The two sets of reference values differ from each other in most of the given frequency spans. In some frequencies the national regulation is more restrictive, whereas in other frequencies the directive is more restrictive - up to ten times difference. Based on the principles laid down in the directive, the new national regulation should follow the reference values from each frequency span whichever is more favorable towards the workers