High Rate Systems Research Articles

Performance analysis of the OFDM-based systems with nonlinear distortion and imperfect parameters estimation

As an effective technique for combating multipath fading and for high data rate transmission over wireless channels, orthogonal frequency division multiplexing (OFDM) is extensively used in high-rate wireless communication systems, such as, the wireless local area network (WLAN) and the digital television terrestrial broadcasting (DTTB) to support high performance bandwidth-efficient multimedia services. OFDM-based multi-carrier systems are much more sensitive to the nonlinear distortion at the transmitter and the imperfect parameters estimation at the receiver than the single carrier systems. In this paper, the compositive performance effects induced on the OFDM signal by the nonlinear distortion and the imperfect parameters estimation are investigated, a closed form of symbol error probability of the OFDM-based system with nonlinear distortion and imperfect parameters estimation is derived. Theoretical results show closely matching with those obtained by simulations for the OFDM-based system with QPSK, 16QAM, 64QAM modulations.

Novel Sputtering Technology for Grain-Size Control

In this paper, we present a description of a novel high-rate plasma sputtering system that allows the control of grain size in sputtered films. Additionally, the system has the advantage of a better utilization of the target material (around 80% to 90%) by eliminating the race track at the target as in conventional plasma magnetron sputtering systems. The potential and capabilities of this novel plasma sputtering device are demonstrated in this paper by the deposition of a number of different Cr thin films suitable for underlayers in thin-film media and for which we have performed a systematic X-ray and TEM analysis to determine the grain-size histograms, mean grain diameters, and their relationship to the sputtering processes.

A pedagogical example of the application of transmission-line theory to study conductor grounding effects

Grounding effects and transmission-line theory are very important topics in applied electromagnetics courses in electrical engineering curricula. A pedagogical example, dealing with a coaxial cable above ground, is developed in this paper. The purpose of this example is to underline the necessity of using the correct tools in analyzing the effects of ground connections, to help realize and prevent the possibility of ill-defined grounding problems, and to show how transmission-line theory results can be used simply to solve conductor-grounding problems in high-rate communication systems.

Asynchronous sampled amplitude histogram models for optical performance monitoring in high-speed networks

Feature Issue on Optical Performance Monitoring (OPM). A methodology that allows us to characterize the main performance parameters of high-rate (up to 40 Gbit/s) systems based on slow, bit-rate-independent sampling is presented taking into consideration all the information present in the histogram. The theory and validating simulation and experimental results are presented, showing that this technique is suitable for future transparent optical networks.

A High-Rate Secondary Treatment Based on a Moving Bed Bioreactor and Multimedia Filters for Small Wastewater Treatment Plants

For small wastewater treatment plants (WWPTs), high-rate secondary treatment systems with good treatment efficiency and easy, stable, and robust operation are called for. In this paper an experimental study on a high rate secondary treatment based on moving bed biofilm reactor (MBBR) and multimedia filters is presented. A high rate MBBR converts easily biodegradable SCOD in short HRT (0.5 h) directly after screening, then a Kaldnes-Filtralite-Sand (KFS) filter removes the particulate COD and detached biofilms at filtration rates of 10–20 m/h. The whole system gave effluent SS and COD less than 30 mg/L and 100 mg/L when total detention time is less than 1 h and small dosage of chemicals (iron and/or cationic polymer) is used. A new scenario of high rate secondary system with a primary Kaldnes coarse media filter in front of high rate MBBR and the KFS filter is proposed and discussed. This scenario with total HRT less than 2 h is more suitable for high influent SS concentrations and may also be extended for nitrogen and phosphorous removal. Compared to conventional secondary treatment, the high rate secondary treatment will be using only 1/5–1/10 of the space, resulting in considerable savings for construction, energy and operation.

Characterisation of oxygen dynamics within a high-rate algal pond system used to treat abattoir wastewater

As part of a study examining the efficacy of high-rate algal pond treatment of high-strength abattoir wastewater, the oxygen dynamics of a pilot scale system were characterised. The relationship between photosynthesis and irradiance was investigated using online data collected throughout a year of operation under varying conditions of climate and wastewater quality. Changes in climate were reflected in changes in the net rate of photosynthesis in deep ponds, consistent with adaptation of algal populations to changing light intensity, whilst the response of shallow ponds was more varied. The use of online monitoring and the calculation in real time of photosynthetic rates should allow for improved design and management of full scale treatment systems and further the understanding of factors driving biological reactions within these systems.

Multi-phased VSG CDMA with level clipping for high-rate transmission systems

In this letter, a multi-phased CDMA system employing a variable spreading gain (VSG) approach is proposed for high-rate applications, based on four algorithms for selecting a multi-code set. From simulation results, in addition to simple receiver structure thanks to level clipping, the multi-phased VSG CDMA system provides an high bit rate transmission, while maintaining an acceptable performance degradation.

A Market Study on the Anaerobic Waste-water Treatment Systems

This study analyzed global trends in the industrial use ofanaerobic wastewater treatment systems. Information on over 750anaerobic systems installed over the last two decades by three leading suppliers of anaerobic systems, namely ADI SystemsInc., Biothane Corporation, and Paques, showed exponential growthin the use of industrial anaerobic wastewater systemsinternationally up to the mid-1990s. After 1994, the number ofannual installations declined, and has been relatively constantover the last three years. The North American market was shown tobe relatively volatile, with no clear indication of futuregrowth, while the European market was found to be relativelymature. In North America, most of the anaerobic wastewatertreatment systems are serving breweries (26%), potato processingindustries (11%), or pulp and paper industries (9%). Ananalysis of the market history of the commercial anaerobic modelssuggests the phasing out of traditional UASB and fermentormodels, and the potential for growth of high-capacity and high-rate systems (>20 kg m-3 d-1) such as the BiothaneEGSB and the Paques Internal Circulation (IC) systems. Future efforts should focus on research into new designs for high-rate and high-capacity systems, and on the encouragement of economic incentivesfor industries implementing anaerobic wastewater treatmentsystems. A market study on other methods of wastewater treatment(e.g. aerobic treatment) is also recommended, to provide insightinto current economic trends in the area of environmental biotechnology.

Anaerobic granular sludge and biofilm reactors.

The long retention time of the active biomass in the high-rate anaerobic digesters is the key factor for the successful application of the high rate anaerobic wastewater treatment. The long solids retention time is achieved due to the specific reactor configuration and it is enhanced by the immobilization of the biomass, which forms static biofilms, particle-supported biofilms, or granules depending on the reactor's operational conditions. The advantages of the high-rate anaerobic digestion over the conventional aerobic wastewater treatment methods has created a clear trend for the change of the role of the anaerobic digestion in the wastewater treatment plants from a pre-treatment method to the main biological treatment method. The application of staged high-rate anaerobic digesters has shown the larger potential among the recent developments in this direction. The most common high-rate anaerobic treatment systems based on anaerobic granular sludge and biofilm are described in this chapter. Emphasis is given to a) the Up-flow Anaerobic Sludge Blanket (UASB) systems, b) the main characteristics of the anaerobic granular sludge, and c) the factors that control the granulation process. Finally, the most innovative staged anaerobic digesters are also presented.

Time synchronisation for OFDM-based WLAN systems

Orthogonal frequency division multiplexing (OFDM) is the key modulation scheme utilised to enable the IEEE 802.11a standard for high-rate WLAN systems. A novel time synchronisation method for the OFDM-based WLAN is presented. The approach utilises coarse and fine estimation. Simulation results exhibit that the algorithm is robust to harsh channel environments.

Optical properties of nanophase films measured by variable-angle spectroscopic ellipsometry

While interest in nanophase films deposited in vacuum from nanoparticle beams dates back to the early 1970s, difficulties in producing such films has delayed their development and investigation of their interesting, new properties predicted. A new type of high-rate deposition system here and at a few other laboratories has overcome these impediments. It is becoming clear that extremely high surface area/volume nanophase thin films of different materials can be deposited. Flowing argon and helium gas are used to sputter and assist condensation in a cooled-wall chamber. Particle size and numbers depend on the nucleation rate, condensation rate and time available for these processes. To date, films have been deposited using targets made of copper, cobalt, molybdenum, silicon, composite copper–cobalt, tantalum, iron, nickel, chromium, zirconium, aluminum, platinum, gold, tin and niobium. The work reported here is a study of the optical properties of soft-landed nanoparticle films using no acceleration. The soft-landed films are porous with a nanocrystalline structure of ∼5–10-nm crystallites, as shown by both transmission electron microscopy and atomic force microscopy. Optical properties were measured using variable-angle spectroscopic ellipsometry. The optical properties of these films do not match bulk or thin film properties of either the ‘pure’ metals or their oxides. Instead, the properties are suggestive of a mixture of void, metal, and metal oxide. It is hoped that such materials may be useful in nanostructured optical devices requiring tailored optical properties over nanometer dimensions.

Iterative Viterbi decoding, trellis shaping, and multilevel structure for high-rate parity-concatenated TCM

We define and apply a new algorithm called the iterative Viterbi decoding algorithm (IVA) to decode a high-rate parity-concatenated TCM system in which a trellis code is used as the inner code and a simple parity-check code is used as the outer code. With trellis shaping, the IVA can achieve a performance 1.25 dB away from the Shannon limit at a BER of 3/spl times/10/sup -5/ with low complexity. By augmenting the system with a binary BCH code, the error floor can be reduced to 10/sup -9/ with very little additional cost.

SE—Structures and Environment: A Dual-reactor Anaerobic System for Complete Treatment of a Food Processing Waste

Anaerobic technologies are commonly employed for the initial treatment of food processing wastewater; however, they are not typically considered capable of treating wastewater to meet final discharge requirements. To assess the potential of anaerobic technologies to meet discharge requirements, the performance of two dual-reactor high-rate anaerobic systems fed with confectionery wastewater was investigated. The primary reactors in the system were operated at constant hydraulic retention times of 1·6 d. The secondary reactors were operated with hydraulic retention times of 0·8, 1·6, and 3·2 d. The secondary reactors, which were both downflow anaerobic filters, achieved maximum chemical oxygen demand (COD) removal rates when operated at a hydraulic retention time of 1·6 d. The brick-filled downflow anaerobic filter and the plastic-ring-filled downflow anaerobic filter produced average effluent five-day biochemical oxygen demand concentrations of 26 mgl−1 (COD=80 mg l−1) and 36 mg l−(COD=112 mg l−1), respectively. To examine the enhanced stability provided by the sequential reactor approach, the dual-reactor system was overloaded at 3·5 times the normal COD concentration (8000 mg l−1) for an 8 h period. The secondary reactors were able to accommodate the increased organic loading emitted from the primary reactors, maintaining an overall removal efficiency of >994%. The results suggest that full anaerobic treatment of readily degradable food waste streams may be realistic, and that a sequential reactor approach significantly enhances overall process stability.

Advances in high rate anaerobic treatment: staging of reactor systems

Anaerobic wastewater treatment (AnWT) is considered as the most cost-effective solution for organically polluted industrial waste streams. Particularly the development of high-rate systems, in which hydraulic retention times are uncoupled from solids retention times, has led to a world-wide acceptance of AnWT. In the last decade up to the present, the application potentials of AnWT are further explored. Research shows the feasibility of anaerobic reactors under extreme conditions, such as low and high temperatures. Also toxic and/or recalcitrant wastewaters, that were previously believed not to be suitable for anaerobic processes, are now effectively treated. The recent advances are made possible by adapting the conventional anaerobic high-rate concept to the more extreme conditions. Staged anaerobic reactor concepts show advantages under non-optimal temperature conditions as well as during the treatment of chemical wastewater. In other situations, a staged anaerobic-aerobic approach is required for biodegradation of specific pollutants, e.g. the removal of dyes from textile processing wastewaters. The current paper illustrates the benefits of reactor staging and the yet un-exploited potentials of high-rate AnWT.

Trellis-coded complementary code keying for high-rate wireless LAN systems

In high-rate wireless LAN, complementary code keying (CCK) is adopted in the IEEE 802.11b standard to support data rates up to 11 Mbps, much higher than the 2-Mbps data rate in the previous wireless LAN standard. Due to less-than-ideal characteristics of the CCK codewords, the CCK performs quite poorly in large-delay-spread multipath channels. In this paper, a new modulation scheme that combines the trellis coding with the CCK modulation is proposed. This scheme is shown, through simulation, to achieve much better error rate performance in medium-to-large channel delay spread environments.

Development of a High-Rate and High-Resolution Data Acquisition System Based on a Real-Time Operating System

Development of a High-Rate and High-Resolution Data Acquisition System Based on a Real-Time Operating System

Variation of bulk properties of anaerobic granules with wastewater type

Development of a granular sludge with high strength, high biological activity and a narrow settling distribution is necessary for optimal operation of high-rate upflow anaerobic treatment systems. Several studies have compared granules produced from different wastewaters but these have largely been from laboratory-fed reactors or compared granules from full-scale reactors fed similar wastewater types. Though two authors have commented on the inferiority of granules produced by a protein-based feed, the properties of these granules have not been characterised. In this paper, granules from full-scale reactors treating fruit and vegetable cannery effluent, two brewery effluents and a pig abattoir (slaughterhouse) were compared in terms of basic composition, size distribution, density, settling velocity, shear strength, and EPS content. The results supported previous qualitative observations by other researchers that indicate granule properties depend more on wastewater type rather than reactor design or operating conditions such as pre-acidification level. The cannery-fed granules had excellent shear strength, settling distribution and density. Granules from the two brewery-fed reactors had statistically the same bulk properties, which were still acceptable for upflow applications. The protein-grown granule had poor strength and settling velocity.

New perspectives in anaerobic digestion

The IWA specialised group on anaerobic digestion (AD) is one of the oldest working groups of the former IAWQ organisation. Despite the fact that anaerobic technology dates back more than 100 years, the technology is still under development, adapting novel treatment systems to the modern requirements. In fact, most advances were achieved during the last three decades, when high-rate reactor systems were developed and a profound insight was obtained in the microbiology of the anaerobic communities. This insight led to a better understanding of anaerobic treatment and, subsequently, to a broader application potential. The present "state-of-the-art" paper, which has been written by members of the AD management committee, reflects the latest achievements and sets future lines for further development.

Effect of sputtering parameters on Ta coatings for gun bore applications

Tantalum offers a number of attractive properties for gun bore coating applications, including a high melting temperature, high ductility, and an environmentally friendly deposition method. However, vapor-deposited tantalum can appear in both the characteristic bcc phase found in the bulk material, and in a very brittle and less desirable ‘beta’ phase. Presence of the beta phase in bore coatings is considered undesirable because of its brittleness and resulting failure as the coating is stressed. A high-rate triode sputtering system with a cylindrical coating geometry was used to produce thick tantalum coatings on 4340 steel smooth bore cylindrical substrates. A systematic series of tests were performed to evaluate the effects of sputtering gas species (Ar, Kr, Xe) and substrate temperature (100–300°C) during deposition on the phase and microstructure of the coatings. Heavier sputtering gases and higher substrate temperatures were found to promote the formation of bcc-phase tantalum coatings. Use of a movable target assembly was shown to promote the production of dense, single-phase tantalum coatings.

Stability of High-Rate Anaerobic Systems. I: Performance under Shocks

Three laboratory reactors, that is, an anaerobic fluidized bed reactor, an anaerobic filter, and an upflow anaerobic sludge blanket reactor, of identical size and operated under identical conditions, were studied by focusing on the system stability in the presence of various shocks. The results obtained from various shock tests revealed the differences and similarities between the behaviors of different reactors with respect to different system parameters. The stability of the three reactors subjected to various shocks was compared and ranked based on the examination of the responses of some sensitive system parameters. Gas phase parameters should be combined with liquid phase parameters to explicitly characterize an anaerobic system's operating status.