Capacity Performance Analysis of M-ary PPM TH-UWB Systems in the Presence of Narrowband Interference

Nikos V. Kokkalis,P. Takis Mathiopoulos,George K. Karagiannidis,Christos S. Koukourlis 한국통신학회 2008 Journal of communications and networks Vol.10 No.3

The capacity of ultra-wideband (UWB) systems in presence of narrowband interference (NBI) is studied. By appropriately modifying the Shannon capacity formula, an analytical expression for the capacity ofM-ary pulse position modulation (PPM) signals in the presence of NBI is obtained. Performance evaluation results for the capacity of such signals as a function of the NBI carrier frequency and power are also presented.

The effects of construction practices on the seismic performance of RC frames with masonry infills

Nikos D. Lagaros,Martha A. Geraki 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.1

A number of construction practices, implemented during the design process of a reinforced concrete (RC) structural system, may have significant consequences on the behaviour of the structural system in the case of earthquake loading. Although a number of provisions are imposed by the contemporary Greek national design codes for the seismic design of RC structures, in order to reduce the consequences, the influence of the construction practices on the seismic behaviour of the structural system remains significant. The objective of this work is to perform a comparative study in order to examine the influence of three, often encountered, construction practices namely weak ground storey, short and floating columns and two combinations on the seismic performance of the structural system with respect to the structural capacity and the maximum interstorey drifts in three earthquake hazard levels.

Influence of time delay and saturation capacity to the response of controlled structures under earthquake excitations

Nikos G. Pnevmatikos,Charis J. Gantes 국제구조공학회 2011 Smart Structures and Systems, An International Jou Vol.8 No.5

During the last thirty years many structural control concepts have been proposed for the reduction of the structural response caused by earthquake excitations. Their research and implementation in practice have shown that seismic control of structures has a lot of potential but also many limitations. In this paper the importance of two practical issues, time delay and saturation effect, on the performance of controlled structures, is discussed. Their influence, both separately and in interaction, on the response of structures controlled by a modified pole placement algorithm is investigated. Characteristic buildings controlled by this algorithm and subjected to dynamic loads, such as harmonic signals and actual seismic events, are analyzed for a range of levels of time delay and saturation capacity of the control devices. The response reduction surfaces for the combined influence of time delay and force saturation of the controlled buildings are obtained. Conclusions regarding the choice of the control system and the desired properties of the control devices are drawn.

Photocatalytic and Filtration Elimination of Methylene Blue by NanofibrousPolystyrene Membrane Containing TiO2 Nanotubes

Niko Faraji,Mehdi Mahmoudian,Asghar Zamani 한국고분자학회 2024 폴리머 Vol.48 No.1

In this research, the nanofibrous polystyrene /titanium dioxide nanotube (PS/TiO2 nanotubes) membrane was prepared by the electrospinning method. Titanium dioxide nanotubes were synthesized by the anodizing method and stabilized on the fibrous polystyrene membrane. Then, the effect of different weight percentages of titanium dioxide nanotubes on the performance of the resulting membranes was investigated. The nanoparticles and nano-composites prepared in this research were analyzed using several analyses, including Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM), along with X-ray energy diffraction spectroscopy (EDS). The thermal behavior and crystal structure of prepared nano-composite membranes were investigated using (TGA) analysis and X-ray diffraction (XRD), respectively. Afterward, to investigate the prepared structures, analyses such as porosity measurement, water contact angle, swelling, and water flux of the membranes were performed. The photocatalytic property of the prepared membranes in the decomposition of methylene blue was investigated by two methods (static and dynamic). The obtained results demonstrated that the dye removal was accomplished in the best way in the static method (using the membrane as an absorbent) for 48 h. The prepared nano-composite membranes were also used in the dye filtration removal process, and the best result was obtained by using the membrane containing titanium dioxide nanotubes with a concentration, of 0.05 gr/V(50). The swelling degree in the fibrous polystyrene membrane was 135%, while in the membrane containing 0.1% titanium dioxide nanotubes, which is the optimal membrane, was 66%. Hydrophilicity measurements by water contact angle revealed that the presence of TiO2 nanotubes improved by about 10%.

(Re)discovering Love Stories

Nikos Manousakis 한국서양고전학회 2018 西洋古典學硏究 Vol.57 No.3

The present paper is an overview and discussion of Byzantine literary criticism concerning the ancient Greek novel from the ninth to the fifteenth century CE. More specifically, I focus here on the opinions and judgments of some of the most prominent Byzantine scholars as regards two fully extant Greek novels: Achilles Tatius’ Leucippe and Clitophon and Heliodorus’ Ethiopian Tale. I review in some detail various aspects of the ‘evaluation practice’ of Patriarch Photios I (ninth century CE) and Michael Psellos (eleventh century CE), and I also – though more briefly – go over the corresponding theories and ideas of (Philip-)Philagathus of Cerami (twelfth century CE) and Ioannis Eugenikos (fifteenth century CE). The main question I attempt to address in this study is how similarly or differently (even idiosyncratically) the Byzantines read and discussed the Greek novels over the centuries.

An ALE Based FE Formulation for the 3D Numerical Simulation of Fineblanking Processes

Niko Manopulo,Longchang Tong,Pavel Hora 한국소성가공학회 2010 기타자료 Vol.2010 No.6

Fineblanking is a manufacturing process which allows the mass production of blanked products with superior surface quality. The 3D numerical simulation of this particularly precise process is however challenging. This is because quality-critical tool features such as the die clearance and the shape of the cutting edges have dimensions up to two orders of magnitude smaller than the average part dimensions. If conventional Updated Lagrange codes are used, a very high FE mesh resolution becomes a must in order to accurately represent the surface evolution along the edge, which in turn makes the computation unfeasible. The methodology presented in this paper makes use of the Arbitrary Lagrangian Eulerian FE Formulation in order to keep control over the mesh region in contact with the tools. This way an optimal FE mesh can be guaranteed throughout the computation. This not only reduces the computational cost considerably, but also avoids mesh distortion along the cutting edge, allowing an accurate representation of the tool features. This approach will be used in conjunction to the stress limit criterion delineated in order to predict material failure in fine blanked products. Numerical results will be validated against the experiments carried out with a specially designed fineblanking tool in use at our institute.

Managing Conflict and Organizational Change

( Nikos Bozionelos ) 한국행정학회 2003 Bulletins et mémoires de la Societe d'Anthropologi Vol.2003 No.-

Wavelet analysis based damage localization in steel frames with bolted connections

Nikos G. Pnevmatikos,Bartlomiej Blachowski,George D. Hatzigeorgiou,Andrzej Swiercz 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.6

This paper describes an application of wavelet analysis for damage detection of a steel frame structure with bolted connections. The wavelet coefficients of the acceleration response for the healthy and loosened connection structure were calculated at each measurement point. The difference of the wavelet coefficients of the response of the healthy and loosened connection structure is selected as an indicator of the damage. At each node of structure the norm of the difference of the wavelet coefficients matrix is then calculated. The point for which the norm has the higher value is a candidate for location of the damage. The above procedure was experimentally verified on a laboratory-scale 2-meter-long steel frame. The structure consists of 11 steel beams forming a four-bay frame, which is subjected to impact loads using a modal hammer. The accelerations are measured at 20 different locations on the frame, including joints and beam elements. Two states of the structure are considered: healthy and damaged one. The damage is introduced by means of loosening two out of three bolts at one of the frame connections. Calculating the norm of the difference of the wavelet coefficients matrix at each node the higher value was found to be at the same location where the bolts were loosened. The presented experiment showed the effectiveness of the wavelet approach to damage detection of frame structures assembled using bolted connections.

핀란드의 점진적 은퇴

Niko Vaananen 한국노동연구원 2020 국제노동브리프 Vol.18 No.1

Internationalization in Tertiary Education: Intra-European Students Mobility

( Nikos P Rachaniotis ),( Filareti Kotsi ),( George M Agiomirgianakis ) 세종대학교 경제통합연구소 2013 Journal of Economic Integration Vol.28 No.3

The enhanced internationalization and mobility of European students reflects an undoubtedly important aspect of human capital investment. This paper examines the internationalization of European students in tertiary education and the factors that determine the probability of a student moving to a European country other than their own. The main goals of the Bologna Process and a framework of definitions of student mobility are presented, as well as factors that may motivate and hamper this process. A linear regression model of the market shares of intra- European students and a linear regression model of the ratios of foreign incoming/outgoing students of European countries are estimated. Finally, a Classification and Regression Tree (CART) algorithm is applied in order to explain the reasoning behind the decisions of students for long-term study abroad. The paper suggests that policy measures towards increasing student mobility flows will extend economic integration of the countries involved via human capital development and are most likely to increase present and future economic flows in a tangible way.