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The existing models of technical systems maintenance management provide required reliability and availability of systems, preferably with as litlle cost as possible. New concepts, increasingly applied in all areas of life, are based on risk. Such an approach is possible and desirable in the field of theory and engineering of maintenance of technical systems and military technical systems. In this paper, the conceptual definitions of technical systems maintenance, maintenance management models and strategies are given, followed by an overview of strategies and models of maintenance of technical systems, their shematic views and mutual comparisons and trends in the management of maintenance of technical systems, the application of which could lead to savings in the maintenance of both technical and military technical systems. [ABSTRACT FROM AUTHOR]

Application of compost in horticultural crops has the potential to provide many benefits and yet there are concerns regarding accumulation of heavy metals in the crop and on human health. Effects of amending soil with compost made from mixed municipal solid waste (MSW) on yield of okra (Abelmoschus esculentus L.) and watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] and on heavy metal concentrations (Cd, Cu, Cr, Ni, Pb, and Zn) in pods of okra and pulp and juice of watermelon were investigated. Four MSW compost rates were applied, 25, 50, 75, and 100 Mg·ha-1, and compared to a non-amended control with no compost application. Addition of MSWC increased yield of okra and weight of watermelons over the control. There were no differences among treatments in heavy metal concentrations in okra pods, watermelon pulp, or juice. [ABSTRACT FROM AUTHOR]

Effectiveness of maintenance management is directly related to critical parameters of technical systems such as efficiency, reliability, and economic life. In practice, this process is executed via procedures on selected adequate maintenance method among which the alternatives such as Total Productive Maintenance, Planned Maintenance, Preventive Maintenance, Predictive Maintenance, Reactive Maintenance, or Reliability Centered Maintenance. However, increasing system complexity due to the contributions of technological developments requires implementing more advance maintenance planning techniques. In this study, an integrated maintenance management system is presented based on Fuzzy Information Axioms methodology for shipboard systems under various characteristics and functional attributes. An extended and more effective maintenance management systematic is developed for merchant ships using applied decision model outcomes. [ABSTRACT FROM AUTHOR]

Abstract: The co-composting of olive oil mill wastes and household refuse was followed for 5 months. During the thermophilic phase of composting, the aerobic heterotrophic bacteria (AHB) count, showed a significant rise with a slight regression of fungal biomass. In the same way, phospholipid fatty acids PLFAs common in bacteria, showed a significant increase of hydroxyl and branched PLFAs. The evaluation of the ratio of octadecenoic PLFAs to stearic acid (C18:1ω/C18:0) revealed a significant reduction while a significant rise in the length of aliphatic chains evaluated by the stearic acid to palmitic acid ratio (C18:0/C16:0) was noted during the stabilization phase. The follow-up of PLFAs, indicates the degree of biodegradation that occurs during composting, it can be regarded an indicator of the stability and maturity of the end product. [Copyright &y& Elsevier]

Abstract: This study is aimed to evaluate the performance of pilot-scale in-vessel composting for food wastes treatment. The composting plant was installed with 324m3 of the composting bay volume and 14,000kg/day of the composting material flow rate. The evaluations studied included the operational indices, the compost maturity indices, and the quality of the final compost. Blowers of this system were useful in maintaining aerobic condition (over 6% oxygen concentration in off-gas) through the entire compost bay. The levels of indices evaluated remained constant in the final part of composting. The final compost was satisfactory for its agricultural application. It was revealed in this study that bulk density bore a linear relation to moisture content during composting, and the final compost without bulking agent showed negative correlation between heavy metal and organic matters content. [Copyright &y& Elsevier]

Abstract: Composting of dead birds with caged layer manure (CLM) and farm yard manure (FYM) was carried out to study the feasibility of composting as an alternative for disposal in Tamil Nadu State, India. The dead birds were sequentially layered with manure substrate and carbon source as per recipes formulated in mini-compost bins (4×4×4 feet). The temperature profile of both CLM and FYM group reached the peak by second week of composting and started declining steadily. The temperature profile was better during summer and monsoon and bins were able to maintain temperature above 60°C (thermophilic) for 3–4 weeks. Season had no influence on attainment of peak temperature and it ranged between 51.8 and 70.4°C. The persistency of thermophilic temperature (above 55°C) was prolonged during summer (17.5–65 days) followed by monsoon (24–39 days) and winter (15.5–21.5 days). No putrefied or obnoxious odour or fly menace was observed during all the seasons of composting. The composting process took 107–127.5 days to finish during summer, 84.5–91 days in monsoon and 61.5–73.5 days in winter. The FYM was able to retain moisture higher (41–54% at the end of primary stage and 27.5–48.2% at the end of secondary stage) than CLM group (17.5–39.3% at primary stage and 20.4–33.5% in secondary stage). Weight reduction was more in FYM group (31.8–58.7%) than CLM group (19.3–48.6%). The volume reduction was uniform in all the seasons, it ranged between 39% and 59.3%. [Copyright &y& Elsevier]

Abstract: Differential scanning calorimetry (DSC) was used to describe compost organic matter quality with regard to input materials and humification. Several basic experiments using 10 selected compost samples were performed to find out how material composition and humification affect the heat flow of the sample and the shift of the second exothermic organic peak. Each input material contributes to the specific DSC profile of the whole compost sample. Biowaste composts from the separate collection can be distinguished from sewage sludge composts due to the specific thermal pattern. Despite the influence of the material itself on the thermal behavior, chemical changes of the progressing process effect the heat flow. Humification of biogenic waste materials causes increasing intensities of the second exothermic peak. Principal component analysis (PCA) was applied to reveal the inherent features in the DSC profiles of 24 compost samples (final products). Thermal characteristics enable the assignment of different materials (sewage sludge and biowaste) to their compost class according to the intended use. Based on these specific thermal features quality assessment of compost organic matter can be performed very fast. DSC profiles of humic acids extracted from the 10 selected composts were recorded. Although similarities of the thermal behavior are visible, each DSC profile shows individual properties with regard to peak position and intensity. Different carbon and nitrogen contents confirm the particular composition of compost humic acids. [Copyright &y& Elsevier]

Abstract: Composting is increasingly used to transform biosolids, obtained following wastewater treatment, into a more stable organic product that can be released in the environment. The process must however be closely monitored to assure that the end product meets the regulations set by environmental agencies with regards to the amount of pathogenic microorganisms present. In this study, a TaqMan qPCR approach targeting the invA gene was developed to monitor the presence of Salmonella spp. in composted biosolids. A validation step was first performed to evaluate the effect of compost age on the quantification of various concentrations of seeded Salmonella typhimurium. Secondly, qPCR was used to investigate the effect of composting time, varying from 1 month to 24 months, on the presence of Salmonella spp. naturally present in biosolids samples. Culture media were used in parallel to corroborate the results obtained by qPCR. The detection limit of the invA gene obtained experimentally from composts seeded with S. typhimurium was 5.8 copies or the equivalent of 5.8 CFU per qPCR reaction. Although the results indicated that compost age had a marginal effect on the detection of seeded S. typhimurium, the TaqMan qPCR approach was efficient at detecting and quantifying the amount of Salmonella spp. present in naturally contaminated composted biosolids of different ages. Results showed that there was a significant decrease in the amount of Salmonella DNA present in composted biosolids over time, which was also corroborated by the CFU counts obtained on the BSA culture medium. However, qPCR was more specific, robust and rapid to execute than performing counts on culture media. qPCR shows promise for routine examination of composted biosolids to ascertain that pathogenic microorganisms, including Salmonella spp., are decreased below acceptable limits before their application in the environment. [Copyright &y& Elsevier]

This paper highlights the function and the implications of a strategic maintenance management system in relation to building maintenance performance. The paper examines the technical and management functions in building maintenance and highlights the issues of quality management, contract management, resourcing strategy and the innovation processes required in the organizational drive towards effective and efficient maintenance management systems. The paper concludes that innovative solutions to maintenance issues are essential for continued efficiency and are brought about through the creation of an environment in which creativity is able to thrive. [ABSTRACT FROM AUTHOR]

Abstract: Biological stability was ascertained by using the Dynamic Respiration Index (DRI) on 144 samples of compost during the years 2003 and 2004, as a routine service for private subjects. Data obtained were collected and are critically discussed in this paper by using other parameters registered during tests, i.e., biomass temperature (T), specific airflow rate (Q s) and biomass analytical data (pH). Good linear correlations were obtained for DRI vs. T, DRI vs. Q s and DRI vs. pH, confirming expected results based on the theoretical discussion. Consequently, using the analytical method proposed in this paper means both T and Q can be used as additional parameters for measurement of the biological stability of compost. As a result, T values of 25.8 and 30.5°C, and specific airflow rate of 8.6 and 13.4m3 Mg−1 VS h−1 were found corresponding to 500 and 1000mgO2 kgVS−1 h−1, which, respectively, indicate a high and a medium degree of biological stability. [Copyright &y& Elsevier]

Abstract: In this paper mathematical models of the composting process are examined and their performance evaluated. Mathematical models of the composting process have been derived from both energy and mass balance considerations, with solutions typically derived in time, and in some cases, spatially. Both lumped and distributed parameter models have been reported, with lumped parameter models presently predominating in the literature. Biological energy production functions within the models included first-order, Monod-type or empirical expressions, and these have predicted volatile solids degradation, oxygen consumption or carbon dioxide production, with heat generation derived using heat quotient factors. Rate coefficient correction functions for temperature, moisture, oxygen and/or free air space have been incorporated in a number of the first-order and Monod-type expressions. The most successful models in predicting temperature profiles were those which incorporated either empirical kinetic expressions for volatile solids degradation or CO2 production, or which utilised a first-order model for volatile solids degradation, with empirical corrections for temperature and moisture variations. Models incorporating Monod-type kinetic expressions were less successful. No models were able to predict maximum, average and peak temperatures to within criteria of 5, 2 and 2°C, respectively, or to predict the times to reach peak temperatures to within 8h. Limitations included the modelling of forced aeration systems only and the generation of temperature validation data for relatively short time periods in relation to those used in full-scale composting practice. Moisture and solids profiles were well predicted by two models, but oxygen and carbon dioxide profiles were generally poorly modelled. Further research to obtain more extensive substrate degradation data, develop improved first-order biological heat production models, investigate mechanistically-based moisture correction factors, explore the role of moisture tension, investigate model performance over thermophilic composting time periods, provide more information on model sensitivity and incorporate natural ventilation aeration expressions into composting process models, is suggested. [Copyright &y& Elsevier]

Abstract: Isotope fractionation during composting may produce organic materials with a more homogenous δ13C and δ15N signature allowing study of their fate in soil. To verify this, C, N, δ13C and δ15N content were monitored during nine months covered (thermophilic; >40°C) composting of corn silage (CSC). The C concentration reduced from 10.34 to 1.73g C (gash)−1, or 83.3%, during composting. Nitrogen losses comprised 28.4% of initial N content. Compost δ13C values became slightly depleted and increasingly uniform (from −12.8±0.6‰ to −14.1±0.0‰) with composting. Compost δ15N values (0.3±1.3 to 8.2±0.4‰) increased with a similar reduced isotope variability. The fate of C and N of diverse composts in soil was subsequently examined. C, N, δ13C, δ15N content of whole soil (0–5cm), light (<1.7gcm−3) and heavy (>1.7g cm−3) fraction, and (250–2000μm; 53–250μm and <53μm) size separates, were characterized. Measurements took place one and two years following surface application of CSC, dairy manure compost (DMC), sewage sludge compost (SSLC), and liquid dairy manure (DM) to a temperate (C3) grassland soil. The δ13C values and total C applied (MgCha−1) were DM (−27.3‰; 2.9); DMC (−26.6‰; 10.0); SSLC (−25.9‰; 10.9) and CSC (−14.0‰; 4.6 and 9.2). The δ13C of un-amended soil exhibited low spatial (−28.0‰±0.2; n=96) and temporal (±0.1‰) variability. All C4 (CSC) and C3 (DMC; SSLC) composts, except C3 manure (DM), significantly modified bulk soil δ13C and δ15N. Estimates of retention of compost C in soil by carbon balance were less sensitive than those calculated by C isotope techniques. One and two years after application, 95 and 89% (CSC), 75 and 63% (SSLC) and 88 and 42% (DMC) of applied compost C remained in the soil, with the majority (80–90%) found in particulate (>53μm) and light fractions. However, C4 compost (CSC) was readily detectable (12% of compost C remaining) in mineral (<53μm) fractions. The δ15N-enriched N of compost supported interpretation of δ13C data. We can conclude that composts are highly recalcitrant with prolonged C storage in non-mineral soil fractions. The sensitivity of the natural abundance tracer technique to characterize their fate in soil improves during composting, as a more homogeneous C isotope signature develops, in addition to the relatively large amounts of stable C applied in composts. [Copyright &y& Elsevier]

Increasing demands are made on maintenance programmes to provide tools that will support maintenance planning. Among of the most important parameters affecting the efficiency of maintenance management are the precision and the reliability of the predicted service life (PSL) of building components. The main objective of this study was to develop a methodology for the establishment of databases listing deterioration patterns of building components based upon their actual condition. The methodology consists of four steps: (1) identification of failure patterns, (2) determination of the component performance (CP), (3) determination of the life expectancy of deterioration path (LEDP) and (4) evaluation of the predicted service life (PSL). The proposed methodology can be used for planning of maintenance activities, for evaluation of economic implications caused by intensive decay and for maintenance management. [ABSTRACT FROM AUTHOR]

This paper examines the computation of optimal preventive maintenance policies for systems which are viewed over a horizon whose length is modeled as being random. Preventive maintenance is modeled as a new mode of failure which has a different distribution of time required to make repair. For the simple case of a system made up of one component, general conditions are developed which assure optimality of the preventive maintenance policy. Preventive maintenance for a two component-one cold standby system is also analyzed to illustrate the application of our methodology on more complex systems. Computational examples are included to emphasize the generality and tractability of this approach to reliability modeling. [ABSTRACT FROM AUTHOR]