Search results

Metamaterials have been utilised in several exciting configurations such as tuneable reflectors, reconfigurable absorbers, and programmable modulators, triggering intense research efforts. Among them, the ability to steer the radiation pattern of a single antenna component by employing a metamaterial-based superstrate is considered crucial for the development of advanced beam forming applications. The purpose of this paper is to introduce an adjustable omega-inspired metamaterial module to facilitate the design of beam steering implementations, involving beam forming capabilities, as well.

A variable capacitive diode is properly positioned at the novel omega element, hence advancing the controllability of its electromagnetic performance and circumventing the requirement of extra bias networks. When an array of these particles is placed in front of an antenna, several negative refractive index profiles can be realised, allowing the manipulation of the beam direction. Furthermore, a pyramidal horn antenna, loaded with this complex medium superstrate, is thoroughly investigated in terms of programmable beam steering and beam forming attributes. Several numerical data derived via the finite element method unveil the merits of the featured configuration.

The proposed structure allows programmability of the electromagnetic behaviour, but also circumvents the necessity of complicated bias networks, while minimising interference. The numerical assessment of a standard gain pyramidal horn antenna, associated to the featured metamaterial superstrate, sufficiently proves the controllable beam steering and beam forming attributes. Several parametric studies clarify the principal characteristics of the proposed setup, facilitating the design of high-end systems.

Development of tuneable metamaterial, which utilises variable capacitive diodes to enable controllability. Incorporation of reconfigurable metamaterials into antenna technology. Design of a pyramidal horn antenna, loaded with a complex medium superstrate exhibiting programmable beam steering and beam forming attributes. The proposed device circumvents the necessity of complicated bias networks, while minimising interference.

Despite numerous studies on the separate health consequences of economic crises and post-migration difficulties, very little is known about the processes through which the intersection of economic crisis and post-migration adversity contribute to migrants’ health vulnerabilities. The purpose of this paper is to examine existing literature about how newly arrived and long-term migrants’ health and well-being are affected by the economic crisis in Greece.

The ongoing economic recession in Greece, combined with the recent migration crisis, provided an adequate context for investigating migrants’ health and well-being. A narrative literature review was performed on whether and how migrants’ health and well-being are affected by the economic and the migration crises in the particular case of Greece. Papers published between January 2010 and December 2017 were selected based on review of titles and abstracts, followed by a full text review.

The review identified a surprisingly limited number of relevant studies. Ultimately five studies were selected and their findings summarised. There was only one study attempting to unravel the specific processes through which the crisis and the post-migration problems impact cumulatively on migrants’ health and well-being and to suggest healthcare improvements. Further research on this topic is urgently needed.

This paper explores existing research looking at how migrants’ health and well-being are affected by the economic and the migration crises in Greece. The emerging dearth of research evidence on the above topic is also critically discussed from a socio-political point of view and recommendations are made related to healthcare practice and services set up for migrants’ health and care.

This study aims to investigate the factors associated with the implementation of risk-based internal audit (RBIA).

As a first step, a literature review of the relevant literature is performed and five potential factors related to the implementation of RBIA are identified. Based on that, this paper constructs a questionnaire survey sent out to 185 internal auditors, executives and accountants in Greece to receive 90 responses during the period of November 2019–January 2020. Multiple regression analysis is conducted to identify the factors related to the implementation of RBIA.

This paper shows that there is a statistically significant positive relationship between the implementation of RBIA and: the provision of risk management training, an active audit committee role and the establishment of a formalized risk management system.

The results have important implications for internal auditors, chief executive officers and accountants who wish to enhance internal audit effectiveness and the accuracy and quality of financial information.

Empirical studies on the factors related to the implementation of RBIA are rare. This is the first study to create empirical variables based on a thorough review of the relevant literature to empirically investigate the factors that are related to the implementation of RBIA in an emerging economy. By focusing on the Greek context, this study also sheds light to other countries with similar corporate governance systems, thus providing insights to settings where the Type II agency problem exists (La Porta et al., 1999).

The purpose of this paper is to examine the evidence of long-range dependence behaviour in both house price returns and volatility for fifteen main regions in Finland over the period of 1988:Q1 to 2018:Q4. These regions are divided geographically into 45 cities and sub-areas according to their postcode numbers. The studied type of dwellings is apartments (block of flats) divided into one-room, two-rooms, and more than three rooms apartments types.

For each house price return series, both parametric and semiparametric long memory approaches are used to estimate the fractional differencing parameter d in an autoregressive fractional integrated moving average [ARFIMA (p, d, q)] process. Moreover, for cities and sub-areas with significant clustering effects (autoregressive conditional heteroscedasticity [ARCH] effects), the semiparametric long memory method is used to analyse the degree of persistence in the volatility by estimating the fractional differencing parameter d in both squared and absolute price returns.

A higher degree of predictability was found in all three apartments types price returns with the estimates of the long memory parameter constrained in the stationary and invertible interval, implying that the returns of the studied types of dwellings are long-term dependent. This high level of persistence in the house price indices differs from other assets, such as stocks and commodities. Furthermore, the evidence of long-range dependence was discovered in the house price volatility with more than half of the studied samples exhibiting long memory behaviour.

Investigating the long memory behaviour in both returns and volatility of the house prices is crucial for investment, risk and portfolio management. One reason is that the evidence of long-range dependence in the housing market returns suggests a high degree of predictability of the asset. The other reason is that the presence of long memory in the housing market volatility aids in the development of appropriate time series volatility forecasting models in this market. The study outcomes will be used in modelling and forecasting the volatility dynamics of the studied types of dwellings. The quality of the data limits the analysis and the results of the study.

To the best of the authors’ knowledge, this is the first research that assesses the long memory behaviour in the Finnish housing market. Also, it is the first study that evaluates the volatility of the Finnish housing market using data on both municipal and geographical level.