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Turbo Coded OFDM with Large Number of Subcarriers

Journal of Signal and Information Processing 2012年第2期3卷 161-168页

作者： Spyridon K. Chronopoulos Giorgos Tatsis panos Kostarakis Physics Department University of Ioannina Ioannina Greece

Wireless communication systems have greatly advanced during the last years. A significant contributor in these systems’ performance has been Orthogonal Frequency Division Multiplexing (OFDM). Since its invention, it is considered to be a technological leap. This leap in splitting an information stream in multiple frequency carriers has been adapted by various scientists working on the development of wireless systems. Moreover, as OFDM presented excellent tolerance of channel fading and noise signals, the evolvement in terms of speed and reliability was consequent, because only a small stream of information is lost due to noise effects. OFDM along with the knowledge that Turbo codes is another excellent scheme of reducing BER, has triggered us to expand our research. So, we experimented in simulation level not only in joining OFDM with Turbo Codes but even in finding a better Turbo scheme compared to a typical PCCC, SCCC and a Convolutional encoder with Viterbi decoder. As the last goal has already been accomplished, in this paper is presented the new OFDM system consisted of our Turbo scheme. The analysis of the previous system took into consideration the effects of an AWGN channel. Also, this noise analysis was conducted using a simulation platform with specific attributes such as transmitting and receiving fixed number of subcarriers (2048 carriers after IFFT block) while using different types of convolutional concatenated codes, such as PCCC (Parallel), SCCC (Serial) and the new PCCC scheme. The results clearly show not only the improvement in the BER performance of the Turbo Coded OFDM systems (compared to others consisted of Viterbi decoders) but the overall superiority of the proposed design.

关键词： Orthogonal Frequency Division Multiplexing Cyclic Prefix Zero Padding Turbo Codes Parallel Convolutional Concatenated Codes Serial Convolutional Concatenated Codes Iterative Decoding Noise Variance

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Approach to a Fifth-Order Boundary Value Problem, via Sperner's Lemma

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Applied Mathematics 2011年第8期2卷 993-998页

作者： panos K. Palamides Evgenia H. Papageorgiou 不详

We consider the five-point boundary value problem for a fifth-order differential equation, where the nonlinearity is superlinear at both the origin and +infinity. Our method of proof combines the Kneser’s theorem with the well-known from combinatorial topology Sperner’s lemma. We also notice that our geometric approach is strongly based on the associated vector field.

关键词： Fifth-Order Differential Equation Vector Field Kneser’s Theorem Sperner’s Lemma

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网络处理器体系结构、协议与平台

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作者： (美)panos C.·Lekkas

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Special issue:Manufacturing engineering management

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Frontiers of Engineering Management 2018年第4期5卷 417-419页

作者： Shanlin YANG panos M.PARDALOS Xinbao LIU School of Management Hefei University of Technology Department of Industrial and Systems Engineering University of Florida

Numerous manufacturing engineering management problems have emerged and attracted great attention in academia and practice, especially in high-end equipment manufacturing field with the development of the Internet and... 详细信息

关键词： Special issue:Manufacturing engineering management

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Airline Disruption Management:A Review of Models and Solution Methods

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Engineering 2021年第4期7卷 435-447页

作者： Yi Su Kexin Xie Hongjian Wang Zhe Liang Wanpracha Art Chaovalitwongse panos M.Pardalos School of Economics and Management Tongji UniversityShanghai 200092China Xiamen Airlines Xiamen 361006China Department of Industrial Engineering and Institute for Advanced Data Analytics University of ArkansasFayettevilleAR 72701USA Center for Applied Optimization Department of Industrial and Systems EngineeringUniversity of FloridaGainesvilleFL 32611USA

The normal operation of aircraft and flights can be affected by various unpredictable factors,such as severe weather,airport closure,and corrective maintenance,leading to disruption of the planned *** a disruption occurs,the airline operation control center performs various operations to reassign resources(e.g.,flights,aircraft,and crews)and redistribute passengers to restore the schedule while minimizing *** introduce different sources of disruption and corresponding ***,basic models and recently proposed extensions for aircraft recovery,crew recovery,and integrated recovery are reviewed,with the aim of providing models and methods for different disruption scenarios in the practical implementation of *** addition,we provide suggestions for future research directions in these topics.

关键词： Disruption management Aircraft recovery problem Crew recovery problem Integrated recovery problem

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Enhanced PAPR in OFDM without Deteriorating BER Performance

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International Journal of Communications, Network and System Sciences 2011年第3期4卷 164-169页

作者： Spyridon K. Chronopoulos Giorgos Tatsis Vasilis Raptis panos Kostarakis 不详

Orthogonal frequency division multiplexing (OFDM) is vastly used in wireless networks. Its superiority relies on the fact that information can be split in large amount of frequencies. Each frequency is called information subcarrier. OFDM exhibits excellent annotation in channel fades and interferers as only a few subcarriers can be affected and consequently a small part of the original data stream can be lost. Orthogonality between frequencies ensures better spectrum management and obviates the danger of intersymbol interference. However, an essential problem exists. OFDM systems have high peak to average power ratio. This implies large fluctuations in signal power, ending up in increasing complexity of ADCs and DACs. Also, power amplifiers must work in a larger linear dynamic region. In this paper we present two new techniques for reducing Peak to Average Power Ratio (PAPR), that can be added in any OFDM system and we compare them with other existing schemes.

关键词： OFDM Convolutional Encoding QPSK Zero padding IFFT Cyclic Prefix ISI PAPR Soft Reduction μ-Law Algorithm Clipping Ratio (CR) Peak Ratio (PR) BER CCDF μLSR μLaCP

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Reducing Peak-to-Average Power Ratio of a Turbo Coded OFDM

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Wireless Engineering and Technology 2012年第4期3卷 195-202页

作者： Spyridon K. Chronopoulos Vasilis Christofilakis Giorgos Tatsis panos Kostarakis Physics Department University of Ioannina Ioannina Greece

Peak to Average Power Ratio (PAPR) is defined as the instantaneous power (maximum value) to the average power ratio. PAPR is considered to be a major problem in OFDM systems. This problem can cause radical unexpected behavior of the signal fluctuation. This fluctuation is constituted by a large number of power states. The enormous number of these states leads to an additional complexity of ADCs and DACs. This research addresses the previous problem in OFDM systems utilizing Turbo Codes. μLaCP technique is employed for the purpose of decreasing PAPR. Moreover, our OFDM system was simulated in the presence of an AWGN channel with four types of codes (without the presence of ADCs and DACs). These were constituted of PCCC (typical and new), SCCC, and Convolutional Codes. Our Turbo Coded OFDM exhibited unchanged BER performance before and after the use of μLaCP technique. This was accomplished by modifying our previous PAPR reduction technique without sacrificing greatly its attributes.

关键词： Orthogonal Frequency Division Multiplexing Peak to Average Power Ratio μ-Law μLaCP μLaIF Parallel Concatenated Convolutional Codes A Posteriori Probability Cyclic Prefix Zero Padding Peak Ratio Bit Error Rate

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Global analysis of cover management and support practice factors that control soil erosion and conservation

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International Soil and Water Conservation Research 2022年第2期10卷 161-176页

作者： Kindiye Ebabu Atsushi Tsunekawa Nigussie Haregeweyn Mitsuru Tsubo Enyew Adgo Ayele Almaw Fenta Derege Tsegaye Meshesha Mulatu Liyew Berihun Dagnenet Sultan Matthias Vanmaercke panos Panagos Pasquale Borrelli Eddy J.Langendoen Jean Poesen Arid Land Research Center Tottori University1390 HamasakaTottori680-0001Japan College of Agriculture and Environmental Sciences Bahir Dar UniversityP.O.Box 1289Bahir DarEthiopia International Platform for Dryland Research and Education Tottori UniversityTottori680-0001Japan Department of Land Resources Management and Environmental Protection Mekelle UniversityP.O.Box 231MekelleEthiopia Faculty of Civil and Water Resource Engineering Bahir Dar Institute of TechnologyBahir Dar UniversityP.O.Box 26Bahir DarEthiopia Department of Earth and Environmental Sciences KULeuven3001HeverleeBelgium University of Liege Department of Geography(U.R.SPHERES)Clos Mercator 34000LiègeBelgium European Commission Joint Research Centre(JRC)Ispra(VR)21027Italy Environmental Geosciences University of BaselBasel4056Switzerland National Sedimentation Laboratory Agricultural Research ServiceUnited States Department of AgricultureUSA Faculty of Earth Sciences and Spatial Management Maria-Curie Sklodowska UniversityKrasnicka 2D20-718LublinPoland

Cover management and support practices largely control the magnitude and variability of soil *** soil erosion models account for their importance(particularly by C-and P-factors in the Revised Universal Soil Loss Equation),obtaining spatially explicit quantitative field data on these factors remains ***,also our insight into the effects of soil conservation measures at larger spatial scales remains *** analyzed the variation in C-and P-factors caused by human activities and climatic variables by reviewing 255 published articles reporting measured or calculated C-and P-factor *** found a wide variation in both factor values across climatic zones,land use or cover types,and support *** average C-factor values decreased from arid(0.26)to humid(0.15)climates,whereas the average P-factor values increased(from 0.33 to 0.47,respectively).Thus,support practices reduce soil loss more effectively in drylands and drought-prone *** global average C-factor varies by one order of magnitude from cropland(0.34)to forest(0.03).Among the major crops,the average C-factor was highest for maize(0.42)followed by potato(0.40),among the major orchard crops,it was highest for olive(0.31),followed by vineyards(0.26).The P-factor ranged from 0.62 for contouring in cropland plots to 0.19 for trenches in uncultivated *** C-factor results indicate that cultivated lands requiring intensive site preparation and weeding are most vulnerable to soil loss by sheet and rill *** low P-factor for trenches,reduced tillage cultivation,and terraces suggests that significantly decreased soil loss is possible by implementing more efficient management *** results improve our understanding of the variation in C-and P-factors and support large-scale integrated catchment management interventions by applying soil erosion models where it is difficult to empirically determine the impact of particular land use or cover types and support

关键词： Climate regimes Drought-prone Erosion modeling Land use Soil conservation

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Implementation of Forest Policy in Greece in Relation to Biodiversity and Climate Change

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Open Journal of Ecology 2018年第3期8卷 174-191页

作者： Konstantinos Spanos Dionysios Gaitanis Asimina Skouteri panos Petrakis Ioannis Meliadis Hellenic Agricultural Organization General Directorate of Agricultural Research Forest Research Institute Thessaloniki Greece Hellenic Agricultural Organization General Directorate of Agricultural Research Institute of Mediterranean Forest Ecosys-tems Athens Greece

This is a review article based on literature (national and international) and empirical approach. A general overview on research priority areas on biodiversity and approaches and tools to provide information for forest policy implementation on biodiversity are briefly summarized. Challenges for biodiversity research and related policy in Europe and Greece are depicted. General information on forests, protected areas and forest management in Greece is also presented. Major actions and measures for conservation of forest biodiversity in Greece are described and analysed. The implementation of forest policy in Greece (including the adoption of International constitutional frame) in relation to biodiversity protection and climate change is also analysed. Priorities identified by the Strategic Plan of Rural Development 2007-2013 in Greece in order to adapt to climate change, are also presented. Furthermore, the National institutional framework (Legislation) and strategic targets for biodiversity conservation in Greece are synoptically presented. Finally, major conclusions and future challenges are highlighted.

关键词： Biodiversity Conservation Protected Areas Forest Policy Implementation Strategic Targets

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用拉冬变换消除地震资料中多次波的实例

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国外油气勘探 1994年第1期6卷 90-94页

作者： panos G.Kelamis 刘宝玉

引言像普通线性反演问题一样,正、反拉冬变换为地震反射资料处理提供了新的可能性。基于拉冬变换的多次波抑制以及噪声衰减程序,提供了一种可以代替传统反褶积和f-k滤波的方法。经过正变换得到的'模型空间'分辨能力的提高是消除多次波... 详细信息

引言像普通线性反演问题一样,正、反拉冬变换为地震反射资料处理提供了新的可能性。基于拉冬变换的多次波抑制以及噪声衰减程序,提供了一种可以代替传统反褶积和f-k滤波的方法。经过正变换得到的'模型空间'分辨能力的提高是消除多次波的基础。因此,通过逆映射多次波,然后从原始CMP道集减去它们,从而获得仅有一次波的道集。在本文中,我们提供了在阿拉伯半岛利用拉冬变换成功地消除多次波能量的三个陆地资料实例。我们将采用一种部分叠加与正、反拉冬变换相结合的简单、经济有效的方法。

关键词：多次波 f-k滤波地震资料

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