The role of synchronization in digital communications using chaos - Part II: Chaotic modulation and chaotic synchronization.

For pt. I see ibid., vol. 44, p. 927-36 (1997). In a digital communications system, data are transmitted from one location to another by mapping bit sequences to symbols, and symbols to sample functions of analog waveforms. The analog waveform passes through a bandlimited (possibly time-varying) analog channel, where the signal is distorted and noise is added. In a conventional system the analog sample functions sent through the channel are weighted sums of one or more sinusoids; in a chaotic communications system the sample functions are segments of chaotic waveforms. At the receiver, the symbol may be recovered by means of coherent detection, where all possible sample functions are known, or by noncoherent detection, where one or more characteristics of the sample functions are estimated. In a coherent receiver, synchronization is the most commonly used technique for recovering the sample functions from the received waveform. These sample functions are then used as reference signals for a correlator. Synchronization-based coherent receivers have advantages over noncoherent receivers in terms of noise performance, bandwidth efficiency (in narrow-band systems) and/or data rate (in chaotic systems). These advantages are lost if synchronization cannot be maintained, for example, under poor propagation conditions. In these circumstances, communication without synchronization may be preferable. The theory of conventional telecommunications is extended to chaotic communications, chaotic modulation techniques and receiver configurations are surveyed, and chaotic synchronization schemes are described

Market-oriented new product development of functional beverages

Strategic reviews of the Irish Food and Beverage Industry have consistently emphasised the need for food and beverage firms to improve their innovation and marketing capabilities, in order to maintain competitiveness in both domestic and overseas markets. In particular, the functional food and beverages market has been singled out as an extremely important emerging market, which Irish firms could benefit from through an increased technological and market orientation. Although health and wellness have been the most significant drivers of new product development (NPD) in recent years, failure rates for new functional foods and beverages have been reportedly high. In that context, researchers in the US, UK, Denmark and Ireland have reported a marked divergence between NPD practices within food and beverage firms and normative advice for successful product development. The high reported failure rates for new functional foods and beverages suggest a failure to manage customer knowledge effectively, as well as a lack of knowledge management between functional disciplines involved in the NPD process. This research explored the concept of managing customer knowledge at the early stages of the NPD process, and applied it to the development of a range of functional beverages, through the use of advanced concept optimisation research techniques, which provided for a more market-oriented approach to new food product development. A sequential exploratory research design strategy using mixed research methods was chosen for this study. First, the qualitative element of this research investigated customers’ choice motives for orange juice and soft drinks, and explored their attitudes and perceptions towards a range of new functional beverage concepts through a combination of 15 in-depth interviews and 3 focus groups. Second, the quantitative element of this research consisted of 3 conjoint-based questionnaires administered to 400 different customers in each study in order to model their purchase preferences for chilled nutrient-enriched and probiotic orange juices, and stimulant soft drinks. The in-depth interviews identified the key product design attributes that influenced customers’ choice motives for orange juice. The focus group discussions revealed that groups of customers were negative towards the addition of certain functional ingredients to natural foods and beverages. K-means cluster analysis was used to quantitatively identify segments of customers with similar preferences for chilled nutrient-enriched and probiotic orange juices, and stimulant soft drinks. Overall, advanced concept optimisation research methods facilitate the integration of the customer at the early stages of the NPD process, which promotes a multi-disciplinary approach to new food product design. This research illustrated how advanced concept optimisation research methods could contribute towards effective and efficient knowledge management in the new food product development process.

Synthesis & characterisation of group IV semiconducting nanowires

Semiconductor nanowires, particularly group 14 semiconductor nanowires, have been the subject of intensive research in the recent past. They have been demonstrated to provide an effective, versatile route towards the continued miniaturisation and improvement of microelectronics. This thesis aims to highlight some novel ways of fabricating and controlling various aspects of the growth of Si and Ge nanowires. Chapter 1 highlights the primary technique used for the growth of nanowires in this study, namely, supercritical fluid (SCF) growth reactions. The advantages (and disadvantages) of this technique for the growth of Si and Ge nanowires are highlighted, citing numerous examples from the past ten years. The many variables involved in this technique are discussed along with the resultant characteristics of nanowires produced (diameter, doping, orientation etc.). Chapter 2 outlines the experimental methodologies used in this thesis. The analytical techniques used for the structural characterisation of nanowires produced are also described as well as the techniques used for the chemical analysis of various surface terminations. Chapter 3 describes the controlled self-seeded growth of highly crystalline Ge nanowires, in the absence of conventional metal seed catalysts, using a variety of oligosilylgermane precursors and mixtures of germane and silane compounds. A model is presented which describes the main stages of self-seeded Ge nanowire growth (nucleation, coalescence and Ostwald ripening) from the oligosilylgermane precursors and in conjunction with TEM analysis, a mechanism of growth is proposed. Chapter 4 introduces the metal assisted etching (MAE) of Si substrates to produce Si nanowires. A single step metal-assisted etch (MAE) process, utilising metal ion-containing HF solutions in the absence of an external oxidant, was developed to generate heterostructured Si nanowires with controllable porous (isotropically etched) and non-porous (anisotropically etched) segments. In Chapter 5 the bottom-up growth of Ge nanowires, similar to that described in Chapter 3, and the top down etching of Si, described in Chapter 4, are combined. The introduction of a MAE processing step in order to “sink” the Ag seeds into the growth substrate, prior to nanowire growth, is shown to dramatically decrease the mean nanowire diameters and to narrow the diameter distributions. Finally, in Chapter 6, the biotin – streptavidin interaction was explored for the purposes of developing a novel Si junctionless nanowire transistor (JNT) sensor.