Practical aspects of a condition monitoring system for a wind turbine with emphasis on its design,system architecture,testing and installation

A condition monitoring system (CMS) plays a critical role in tapping the maximum potential of wind energy through wind turbine by minimizing the downtime. It has been proved that the CMS-based maintenance, compared to scheduled and corrective maintenance, is more suitable in many aspects with few disadvantages. The cost of CMS design and installation is substantial in comparison to other maintenance approaches but in the longer run CMS provides benefits surpassing the costs. There are such important parameters as the identification of most sensitive, less sensitive components, replacement costs accompanied with certain components that should be taken into consideration when designing the CMS. In this paper, we have made an attempt to evaluate the viability of CMS, and important parameters in its design, system architecture and installation. The sole purpose is to highlight the overwhelming role of CMS as a better and viable option for increasing the production rate and lowering the downtime in the wind energy converter.     

CHANGES IN ASPHALT CHEMISTRY AND DURABILITY DURING OXIDATION AND POLYMER MODIFICATION

The Gulf Countries' environmental conditions are very severe. The temperature zoning study indicate that more than half of Gulf areas experience a maximum seven consecutive days pavement temperature of 76°C (Al-Abdul Wahhab et al., 1997). This has resulted in damage to the road networks in the form of cracking, rutting and deformation. Polymer modification of asphalt is required to increase the resistance to permanent deformation at relatively high temperatures without adversely affecting the properties of the asphalts at low temperature. In this work chemical and performance-related properties of fresh, oxidized, and polymer modified asphalts were evaluated. The physical properties and performance characteristics of asphalts were found to depend on the chemical composition of asphalt. The interactions of polar functionalities actually present or formed during oxidative aging or due to polymer modification, influence the viscosity and related flow properties. The changes in composition of fresh, oxidized and polymer-modified asphalts can be clearly identified from Infrared spectroscopy. NMR spectroscopy enables detailed information about the Carbon-and-hydrogen-types and average molecular/structural parameters of asphalt without separating it into different components.     

Synthesis of substituted fatty oxathiolanes and thioethers from an allylic oxo fatty acid ester

Substituted oxathiolane and thioether derivatives have been synthesized from an allylic oxo fatty acid ester. The reaction of methyl 4-oxo-trans-2-octadecenoate with 3-mercaptopropan-1,2-diol (1-thioglycerol) affords methyl 4-(3′-hydroxymethyl-1′,4′-oxathiolane)-2(3)-(O-mercaptopropan-1″,2″-diol)-octadecanoate (II), methyl 4-oxo-2(3)-(O-mercaptopropan-1′,2′-diol)-octadecanoate (III), methyl 4-(3′-hydroxy-l′,5′-oxathiane)-2 (3)-(S-mercaptopropan-1″,2″-diol)-octadecanoate (IV), methyl 4-oxo-2(3)-(S-mercaptopropan-1′, 2′diol)-octadecanoate (V) and methyl 4-(3′-hydroxymethyl-1′, 4′-oxathiolane)-2(3)-(S-mercaptopropan-1″, 2″-diol)-octadecanoate (VI). Structures of the individual reaction products have been established on the basis of spectral data and microanalyses.     

Enantioselective dehydration of butan-2-ol using zeolite Y modified with dithiane oxides: comments on the nature of the active site

Modification of zeolite H-Y by dithiane oxides (2-R-1,3-dithiane 1-oxide, R = H, CH₃, C₆H₅) is shown to enhance significantly its activity for the acid-catalysed gas phase dehydration of butan-2-ol. The rate enhancement is observed for catalysts that are prepared using two commercial samples of zeolite H-Y. The origin of this effect is examined using in situ FTIR spectroscopy and ²⁷Al and ²⁹Si MAS NMR spectroscopy studies of the modified zeolite. The rate enhancement is considered to result from a specific interaction between the dithiane oxide modifier with both the extra-framework and framework aluminium in the zeolite. This revised version was published online in July 2006 with corrections to the Cover Date.     

A comparison of the random-effects pattern mixture model with last-observation-carried-forward (LOCF) analysis in longitudinal clinical trials with dropouts

The last-observation-carried-forward imputation method is commonly used for imputting data missing due to dropouts in longitudinal clinical trials. The method assumes that outcome remains constant at the last observed value after dropout, which is unlikely in many clinical trials. Recently, random-effects regression models have become popular for analysis of longitudinal clinical trial data with dropouts. However, inference obtained from random-effects regression models is valid when the missing-at-random dropout process is present. The random-effects pattern-mixture model, on the other hand, provides an approach that is valid under more general missingness mechanisms. In this article we describe the use of random-effects pattern-mixture models under different patterns for dropouts. First, subjects are divided into groups depending on their missing-data patterns, and then model parameters are estimated for each pattern. Finally, overall estimates are obtained by averaging over the missing-data patterns and corresponding standard errors are obtained using the delta method. A typical longitudinal clinical trial data set is used to illustrate and compare the above methods of data analyses in the presence of missing data due to dropouts.     

Kinetic modeling of pyrolysis of three Iranian waste oils in a micro-fluidized bed

Different approaches have been used to convert the waste materials into a clean syngas or other chemicals such as methanol. Among them, pyrolysis is a good candidate to produce the synthesis gas and volatile matters for industrial and refinery applications. In this work, we studied the kinetic and chemical behavior of three Iranian waste oils through a kinetic model and an experimental study. The experiments carried out in a micro-FB reactor, which is a good option for low emissions. Results showed that the reaction temperature and reaction rate are two of the most important factors for maximum conversion level of fuel. Results also showed an optimum value for reaction rate. The modeling results validated against the experimental measurements and found to be in good agreements.     

In Vitro Antiamoebic Activity Evaluation and Docking Studies of Metronidazole–Triazole Hybrids

An in‐house database of 520 compounds was docked against Entamoeba histolytica thioredoxin reductase (EhTrR), a promising target for the treatment of amoebiasis. Amongst these, some metronidazole (MTZ)–triazole hybrids were ranked high, with docking scores from ?10.23 to ?7.56. Studies of the binding orientations and conformations show that the head groups of MTZ–triazole hybrids interact with the arginine residues within the binding pocket of EhTrR, making it clear that such is the optimal and most reliable orientation for this class of compounds. The top‐ten MTZ–triazole hybrids were then selected for evaluation of their activity against the HM1:IMSS strain of amoeba. The most active compound, 2‐pyridyl‐(1,2,3‐triazolyl)metronidazole 10 , with an IC₅₀ value of 8.4 nM , was significantly more active than the standard drug MTZ alone. Docking studies revealed that compound 10 may act as an EhTrR inhibitor with activity in the nanomolar range and satisfactory ADME properties; it is a suitable candidate to be carried forward as a potential lead in the discovery of drugs to combat amoebiasis.     

Optimising the production of energy from coblended food waste and biosolids using batch reactor studies

Energy production from a coblended mixture of biosolids and food waste was optimised for hydrogen and methane production. Four different blends were prepared by varying the carbohydrate : protein (carb : pro) ratios. The biosolids contained a low carbohydrate fraction and so was not suitable for hydrogen production when used alone. However coblending this waste with a carbohydrate‐enriched food waste produced a greater hydrogen yield, making this option viable. Batch studies showed that the optimised mix had a biosolids concentration of 25.7% (w/w). The largest hydrogen yield of 198.5 mL/gVS_removed was observed when the carb : pro was 2.78, and this was threefold higher than the other carb : pro ratios evaluated in this study. The digestate recovered after hydrogen recovery had a C : N of 17.5, which is in the ideal range for methane production. The biochemical methane potential test showed a methane yield of 239 mL/gVS_removed, and the total volatile solids destruction following two‐phase hydrogen and methane production was 93%.     

Assessment of reservoir temperatures of thermal springs of the northern areas of Pakistan by chemical and isotope geothermometry

Chemical and isotope geothermometers, i.e. the Na–K, K–Mg, quartz and δ¹⁸O(SO₄–H₂O), have been applied to estimate the reservoir temperature of the thermal springs in the northern areas of Pakistan. The chemical types of the thermal waters and the effects of mixing of shallow cold water with the thermal end-members are discussed. These waters are neutral to slightly alkaline and have low dissolved contents. Sodium is the dominant cation in almost all the cases. In terms of anions, the hot waters of Budelas are of the SO₄ type, those of Tatta Pani are of mixed character (SO₄ and HCO₃), and the waters from the remaining areas show HCO₃ domination. An absence of tritium in Tatta Pani and Tato thermal springs indicates that they do not have any contribution of shallow young water. In the case of the Murtazabad springs, the wide range of tritium concentrations, negative correlations with surface temperature and Cl, and positive correlation between Na and Cl show that the shallow cold groundwater is mixing with thermal water in different proportions. For the mixed water of Murtazabad thermal springs, ‘isochemical modelling’ using the Na–K, K–Mg and quartz geothermometers indicates an equilibrium temperature in the range 185–200 °C. The δ¹⁸O(SO₄–H₂O) geothermometer gives relatively low temperatures for three springs, whereas two samples are close to the 185–200 °C temperature interval. The reservoir temperatures of Tatta Pani springs (100–120 °C), determined by Na–K and quartz geothermometers, are in good agreement. The δ¹⁸O(SO₄–H₂O) geothermometer gives a relatively higher range (140–150 °C) for most of the Tatta Pani springs. For Tato spring, the isotope and chemical geothermometers (except for the K–Mg) agree on an equilibrium temperature of about 170 °C. Reservoir temperatures of the remaining minor fields are not conclusive due to the lack of sufficient data.