Flip-OFDM for Optical Wireless Communications

We consider two uniploar OFDM techniques for optical wireless communications: asymmetric clipped optical OFDM (ACO-OFDM) and Flip-OFDM. Both techniques can be used to compensate multipath distortion effects in optical wireless channels. However, ACO-OFDM has been widely studied in the literature, while the performance of Flip-OFDM has never been investigated. In this paper, we conduct the performance analysis of Flip-OFDM and propose additional modification to the original scheme in order to compare the performance of both techniques. Finally, it is shown by simulation that both techniques have the same performance but different hardware complexities. In particular, for slow fading channels, Flip-OFDM offers 50% saving in hardware complexity over ACO-OFDM at the receiver.Comment: published in IEEE Information Theory Workshop, Paraty Brazil, Sept 201

Optical properties of borotellurite glasses containing metal oxides

Glass samples of the system: 5MxOy-20B2O3-75TeO2 : MxOy = WO3, Nb 2O5, PbO, Nd2O3, Y2O3, Eu2O3 were prepared by melt quenching and characterized by X-ray diffraction, density, Differential Scanning Calorimetry, UV-visible and FTIR spectroscopy. XRD patterns confirmed the amorphous structure of all samples. Glass transition temperature was maximum in borotellurite glass containing Y2O3. Refractive index, atomic polarizability and basicity increased in the following order of ions: Y3+ < Eu3+ < Pb2+ < Nd3+ < Nb 3+ < W6+. FTIR studies showed that PbO is outstanding in enhancing the concentration of tetrahedral borons in the borotellurite network

Structural transitions in alumina nanoparticles by heat treatment

γ-alumina nanoparticles were annealed sequentially at 800°C, 950°C and 1100°C and structural transitions as a function of heat treatment were studied by X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) methods.. XRD studies found that γ-Al2O3 is stable upto a temperature of at least 950°C and transforms to the thermodynamically stable α-phase after annealing at 1100°C. MAS-NMR revealed that γ-alumina contains AlO4 and AlO6 structural units in the ratio 1: 2, while α-phase contains only AlO6 units. DSC confirmed that γ → α transition initiates at 1060°C

An Empirical Comparison of Consumer Innovation Adoption Models: Implications for Subsistence Marketplaces

So called “pro-poor” innovations may improve consumer wellbeing in subsistence marketplaces. However, there is little research that integrates the area with the vast literature on innovation adoption. Using a questionnaire where respondents were asked to provide their evaluations about a mobile banking innovation, this research fills this gap by providing empirical evidence of the applicability of existing innovation adoption models in subsistence marketplaces. The study was conducted in Bangladesh among a geographically dispersed sample. The data collected allowed an empirical comparison of models in a subsistence context. The research reveals the most useful models in this context to be the Value Based Adoption Model and the Consumer Acceptance of Technology model. In light of these findings and further examination of the model comparison results the research also shows that consumers in subsistence marketplaces are not just motivated by functionality and economic needs. If organizations cannot enhance the hedonic attributes of a pro-poor innovation, and reduce the internal/external constraints related to adoption of that pro-poor innovation, then adoption intention by consumers will be lower

Global assessment of marine plastic exposure risk for oceanic birds

Plastic pollution is distributed patchily around the world’s oceans. Likewise, marine organisms that are vulnerable to plastic ingestion or entanglement have uneven distributions. Understanding where wildlife encounters plastic is crucial for targeting research and mitigation. Oceanic seabirds, particularly petrels, frequently ingest plastic, are highly threatened, and cover vast distances during foraging and migration. However, the spatial overlap between petrels and plastics is poorly understood. Here we combine marine plastic density estimates with individual movement data for 7137 birds of 77 petrel species to estimate relative exposure risk. We identify high exposure risk areas in the Mediterranean and Black seas, and the northeast Pacific, northwest Pacific, South Atlantic and southwest Indian oceans. Plastic exposure risk varies greatly among species and populations, and between breeding and non-breeding seasons. Exposure risk is disproportionately high for Threatened species. Outside the Mediterranean and Black seas, exposure risk is highest in the high seas and Exclusive Economic Zones (EEZs) of the USA, Japan, and the UK. Birds generally had higher plastic exposure risk outside the EEZ of the country where they breed. We identify conservation and research priorities, and highlight that international collaboration is key to addressing the impacts of marine plastic on wide-ranging species

Global assessment of marine plastic exposure risk for oceanic birds

Plastic pollution is distributed patchily around the world’s oceans. Likewise, marine organisms that are vulnerable to plastic ingestion or entanglement have uneven distributions. Understanding where wildlife encounters plastic is crucial for targeting research and mitigation. Oceanic seabirds, particularly petrels, frequently ingest plastic, are highly threatened, and cover vast distances during foraging and migration. However, the spatial overlap between petrels and plastics is poorly understood. Here we combine marine plastic density estimates with individual movement data for 7137 birds of 77 petrel species to estimate relative exposure risk. We identify high exposure risk areas in the Mediterranean and Black seas, and the northeast Pacific, northwest Pacific, South Atlantic and southwest Indian oceans. Plastic exposure risk varies greatly among species and populations, and between breeding and non-breeding seasons. Exposure risk is disproportionately high for Threatened species. Outside the Mediterranean and Black seas, exposure risk is highest in the high seas and Exclusive Economic Zones (EEZs) of the USA, Japan, and the UK. Birds generally had higher plastic exposure risk outside the EEZ of the country where they breed. We identify conservation and research priorities, and highlight that international collaboration is key to addressing the impacts of marine plastic on wide-ranging species

Economic and Social Impacts of Rapid Shale Oil Development in Western North Dakota

This dissertation comprises of five qualitative and exploratory studies. The studies focus on the social and economic impacts of rapid shale oil development, which is colloquially referred to as an “oil boom” on the communities and its members in western North Dakota. The dissertation presents a detailed exploration of the impacts and implications of the boom on community values and attitudes, quality of life, and community development. Impact of the boom on each topic is presented as an independent article or chapter. The data for the dissertation was collected through open-ended, face-to-face interviews. The findings highlight the opportunities created by the boom, barriers inhibiting community development, and the solutions necessary to achieve the community development potential created by the economic activity of the oil boom.North Dakota Humanities CouncilNorthern Plains Ethics Institut

Non-coherent OFDM techniques

Future indoor wireless networks will need alternative RF spectral resources to support the multi-gigabit per second (Gb/s) data speeds demanded by next generation multimedia applications. Although RF spectra in millimeter-wave, terahertz and optical bands are relatively uncongested, the communication systems operating in these frequency bands are difficult to implement, since they often suffer from stability problems due to the very high carrier frequencies. Hence, new physical layer technologies that can offer stable and low-complexity transceivers need to be developed. In this research work, non-coherent orthogonal frequency division multiplexing (OFDM) is studied to meet this demand. Non-coherent OFDMs can mitigate inter-symbol interference caused by channel frequency selectivity and achieve high spectral efficiency. Moreover, compared to conventional OFDMs, non-coherent OFDM uses simple passive direct detection without the need of complex RF frontend components such as mixers and oscillators. In this study, various non-coherent OFDM schemes with new detection enhancements are proposed to improve the performance of millimeter-wave, terahertz, optical, and optical wireless communication systems. It is shown analytically and by simulation that the proposed non-coherent OFDMs offer better bit error rate performance with much lower complexity, when compared to conventional OFDMs. In addition, a simple non-linear pre-distortion technique is explored to further improve the spectral efficiency of non-coherent OFDMs. Finally, space-time block coded (STBC) multiple-input multiple-output (MIMO) transmission schemes are incorporated with the proposed non-coherent OFDMs to offer improved system performance

Analysis of Self-Het OFDM enhancements for 60GHz indoor RF channels

In this paper, we consider two enhancements for self-heterodyne OFDM (Self-Het OFDM): subcarrier pairing and smart carrier positioning (SCP). We analyze their performance over a practical 60 GHz indoor RF channel. This channel deviates from the standard AWGN and Rayleigh fading models for Line of Sight (LoS) and Non LoS. We show that for NLoS channels they can jointly improve the diversity order and performance by 7.7 dB at BER of 10-2, when compared to the standard self-het OFDM. Similar improvements are observed for channels with strong LoS components. © 2013 IEEE.2013 Australian Communications Theory Workshop, AusCTW 201

Non-coherent OFDM techniques

Future indoor wireless networks will need alternative RF spectral resources to support the multi-gigabit per second (Gb/s) data speeds demanded by next generation multimedia applications. Although RF spectra in millimeter-wave, terahertz and optical bands are relatively uncongested, the communication systems operating in these frequency bands are difficult to implement, since they often suffer from stability problems due to the very high carrier frequencies. Hence, new physical layer technologies that can offer stable and low-complexity transceivers need to be developed. In this research work, non-coherent orthogonal frequency division multiplexing (OFDM) is studied to meet this demand. Non-coherent OFDMs can mitigate inter-symbol interference caused by channel frequency selectivity and achieve high spectral efficiency. Moreover, compared to conventional OFDMs, non-coherent OFDM uses simple passive direct detection without the need of complex RF frontend components such as mixers and oscillators. In this study, various non-coherent OFDM schemes with new detection enhancements are proposed to improve the performance of millimeter-wave, terahertz, optical, and optical wireless communication systems. It is shown analytically and by simulation that the proposed non-coherent OFDMs offer better bit error rate performance with much lower complexity, when compared to conventional OFDMs. In addition, a simple non-linear pre-distortion technique is explored to further improve the spectral efficiency of non-coherent OFDMs. Finally, space-time block coded (STBC) multiple-input multiple-output (MIMO) transmission schemes are incorporated with the proposed non-coherent OFDMs to offer improved system performance