Fiberglass Stacks - Analysis Concepts

The world's tallest free-standing glass, reinforced plastic (GRP) exhaust stack- scrubber system with a total height of 170 ft (51.8 m) has been manufactured for a sugar processing plant in Moses Lake, Washington, by Century Fiberglass, Anaheim, California. The GRI' stack and scrubber are used to control solid and gaseous emissions from a coal-fired boiler. This GRP stack replaces a 200 ft (61 m) high concrete stack which had been in service for over 20 years (Fig. 1). Vertical and lateral supports for the GRP stack are provided only at the base of the stack to resist dead loads, wind, and seismic forces. The 10 ft (3.05 m) diameter exhaust stack weighs 21,000 lb (93.4 kN) and has a tapered wall thickness varying from 0.25 in. (0.64 cm) at the top to 0.87 in. (2.21 cm) near the bottom. All previous GRP stack-scrubber systems more than 80 ft (24.4 m) in height have been laterally supported with guy wires or caged within a steel frame. Reference 1 provides a general summary of the design concepts in composites and their advantages and disadvantages.     

Sex Pheromones of Three Citrus Leafrollers, Archips atrolucens, Adoxophyes privatana, and Homona sp., Inhabiting the Mekong Delta of Vietnam

Archips atrolucens, Adoxophyes privatana, and Homona sp. are serious defoliators of citrus trees in the Mekong Delta of Vietnam. In order to establish a sustainable pest-management program for the three species, their female-produced sex pheromones were investigated by GC-EAD and GC-MS analyses, and the following multi-component pheromones were identified: (Z)-11-tetradecenyl acetate (Z11-14:OAc), (E)-11-tetradecenyl acetate (E11-14:OAc), and tetradecyl acetate (14:OAc) in a ratio of 64:32:4 for A. atrolucens; Z11-14:OAc and (Z)-9-tetradecenyl acetate (Z9-14:OAc) in a ratio of 92:8 for A. privatana; and Z11-14:OAc and (Z)-9-dodecenyl acetate (Z9-12:OAc) in a ratio of 96:4 for Homona sp. Each lure baited with synthetic components as a mimic of the natural pheromone attracted males of the target species specifically, indicating that each monounsaturated minor component plays a significant role for mating communication and reproductive isolation of the three species inhabiting the same citrus orchards. In an extract of the pheromone glands of A. atrolucens females, the content of 14:OAc was very low, but a synergistic effect was observed clearly when the saturated compound was mixed at the same level as the E11-14:OAc. The synthetic lures will provide useful tools for monitoring flights of adults of the three species.     

Robust control synthesis for CNC machine spindle

Abstract

This paper aims to analyze the dynamic stability and build the robust controller for motorized spindle system under parametric variations, external disturbances and measurement noises. A nonlinear model has been established for the machine tool spindles. The phase portrait and bifurcation analyses are provided to show dynamical behaviors for spindle machining. The spindle operations can be dynamically stables or unstable under parameter variations and disturbances. By using the robust control synthesis, the system designers can shape the frequency responses of the desired model which satisfies both transient response and robustness against various uncertainties. In fact, the robust controller can effectively attenuate exogenous disturbances and sensor noises during machining process. Finally, the simulations results demonstrate that the presented controller provides robust stability for the spindle speeds, along with excellent abilities of noise as well as disturbance attenuations.     

Analysis of Multicomponent Polynomial Phase Signals

While the theory of estimation of monocomponent polynomial phase signals is well established, the theoretical and methodical treatment of multicomponent polynomial phase signals (mc-PPSs) is limited. In this paper, we investigate several aspects of parameter estimation for mc-PPSs and derive the Crameacuter-Rao bound. We show the limits of existing techniques and then propose a nonlinear least squares (NLS) approach. We also motivate the use the Nelder-Mead simplex algorithm for minimizing the nonlinear cost function. The slight increase in computational complexity is a tradeoff for improved mean square error performance, which is evidenced by simulation results     

Continuous electricity generation at high voltages and currents using stacked microbial fuel cells

Connecting several microbial fuel cell (MFC) units in series or parallel can increase voltage and current; the effect on the microbial electricity generation was as yet unknown. Six individual continuous MFC units in a stacked configuration produced a maximum hourly averaged power output of 258 W m(-3) using a hexacyanoferrate cathode. The connection of the 6 MFC units in series and parallel enabled an increase of the voltages (2.02 V at 228 W m(-3)) and the currents (255 mA at 248 W m(-3)), while retaining high power outputs. During the connection in series, the individual MFC voltages diverged due to microbial limitations at increasing currents. With time, the initial microbial community decreased in diversity and Gram-positive species became dominant. The shift of the microbial community accompanied a tripling of the short time power output of the individual MFCs from 73 W m(-3) to 275 W m(-3), a decrease of the mass transfer limitations and a lowering of the MFC internal resistance from 6.5 +/- 1.0 to 3.9 +/- 0.5 omega. This study demonstrates a clear relation between the electrochemical performance and the microbial composition of MFCs and further substantiates the potential to generate useful energy by means of MFCs.     

Arsenic removal from groundwater by household sand filters: comparative field study, model calculations, and health benefits

Arsenic removal efficiencies of 43 household sand filters were studied in rural areas of the Red River Delta in Vietnam. Simultaneously, raw groundwater from the same households and additional 31 tubewells was sampled to investigate arsenic coprecipitation with hydrous ferric iron from solution, i.e., without contact to sand surfaces. From the groundwaters containing 10-382 microg/L As, < 0.1-48 mg/L Fe, < 0.01-3.7 mg/L P, and 0.05-3.3 mg/L Mn, similar average removal rates of 80% and 76% were found for the sand filter and coprecipitation experiments, respectively. The filtering process requires only a few minutes. Removal efficiencies of Fe, phosphate, and Mn were > 99%, 90%, and 71%, respectively. The concentration of dissolved iron in groundwater was the decisive factor for the removal of arsenic. Residual arsenic levels below 50 microg/L were achieved by 90% of the studied sand filters, and 40% were even below 10 microg/L. Fe/As ratios of > or = 50 or > or = 250 were required to ensure arsenic removal to levels below 50 or 10 microg/L, respectively. Phosphate concentrations > 2.5 mg P/L slightly hampered the sand filter and coprecipitation efficiencies. Interestingly, the overall arsenic elimination was higher than predicted from model calculations based on sorption constants determined from coprecipitation experiments with artificial groundwater. This observation is assumed to result from As(lll) oxidation involving Mn, microorganisms, and possibly dissolved organic matter present in the natural groundwaters. Clear evidence of lowered arsenic burden for people consuming sand-filtered water is demonstrated from hair analyses. The investigated sand filters proved to operate fast and robust for a broad range of groundwater composition and are thus also a viable option for mitigation in other arsenic affected regions. An estimation conducted for Bangladesh indicates that a median residual level of 25 microg/L arsenic could be reached in 84% of the polluted groundwater. The easily observable removal of iron from the pumped water makes the effect of a sand filter immediately recognizable even to people who are not aware of the arsenic problem.     

Results of studying atmospheric corrosion in Vietnam 1995–2005

Vietnam is situated in the wet tropical zone; thus, atmospheric conditions are characterized by high temperatures and a long time of wetness (TOW). In addition, the salt air coming in from the sea causes a high chloride concentration in coastal areas. Furthermore, Vietnam is a developing country, which means that air pollution is increasing with the development of industry. These factors result in significant damage to materials by atmospheric corrosion. In this report, the results of a recent study on the corrosion of carbon steel and zinc-galvanized steel at 6–8 testing sites in Vietnam over 10 recent years (1995–2005) are focused on as well as the effects of environmental factors on atmospheric corrosion. The results showed that the corrosion of carbon steel is dominated by TOW, whereas zinc-galvanized-steel corrosion strongly depends on the chloride ion concentration in the air. The corrosion losses of both carbon- and zinc-galvanized steel fit the power model well with high correlation coefficients. In addition, the characteristics of the Vietnamese climate are introduced in the form of distribution maps of temperature (T), relative humidity (RH), total rainfall and TOW. A relationship between TOW, T and RH was found that enabled the calculation of TOW from T and RH data, which are available at meteorological stations. Finally, atmospheric corrosivity is determined on the basis of data on TOW, Cl^– and SO₂ concentrations, and the carbon steel corrosion rate. It is shown that in Vietnam, TOW is so long that the corrosion rate of carbon steel is in the C₃ category; nevertheless, Cl^– and SO₂ concentrations in the atmosphere are not high.     

Creating resilient and sustainable manufacturing businesses – a conceptual fitness model

Over recent years, UK manufacturing industry has experienced turbulence in its business performance. Lower cost products, and responsive and flexible processes, are now essential in order for a company to capture new markets and to become economically resilient. Business resiliency is a term used frequently to describe a company’s ability to adapt and cope with disturbance. This has led to the generation of many frameworks and models aimed at guiding companies towards improved business performance. However, these frameworks are primarily strategic in nature and do not necessarily focus on creating resilience at an operational level in manufacturing companies. The authors employ a mixed research approach initially undertaking a literature review and then a screening survey in to 25 manufacturing companies in order to identify the key business resiliency techniques employed. Following this, a focus group goes on to detail a new manufacturing resiliency model called the fit operational model. The model’s effectiveness is then assessed and adjusted as a result of being implemented in a subject company.     

Binary Bees Algorithm – bioinspiration from the foraging mechanism of honeybees to optimize a multiobjective multidimensional assignment problem

The simultaneous mission assignment and home allocation for hospital service robots studied is a Multidimensional Assignment Problem (MAP) with multiobjectives and multiconstraints. A population-based metaheuristic, the Binary Bees Algorithm (BBA), is proposed to optimize this NP-hard problem. Inspired by the foraging mechanism of honeybees, the BBA's most important feature is an explicit functional partitioning between global search and local search for exploration and exploitation, respectively. Its key parts consist of adaptive global search, three-step elitism selection (constraint handling, non-dominated solutions selection, and diversity preservation), and elites-centred local search within a Hamming neighbourhood. Two comparative experiments were conducted to investigate its single objective optimization, optimization effectiveness (indexed by the S-metric and C-metric) and optimization efficiency (indexed by computational burden and CPU time) in detail. The BBA outperformed its competitors in almost all the quantitative indices. Hence, the above overall scheme, and particularly the searching history-adapted global search strategy was validated.