Austempered ductile iron (ADI) has a good combination of mechanical properties and castability allowing it to replace forged steels while offering lower costs. CADI is thought to improve ADI's ...abrasion resistance by the reinforcement with carbides. However, there are other potential applications where different wear mechanisms are present.
This study is a continuation of a previous work on CADI in which the influence of the microstructure on the RCF performance was evaluated. Hence provides tools for microstructural design to obtain an optimal performing CADI for each application.
Four CADI microstructures were evaluated in a flat washer rolling contact fatigue testing rig with parameters leading to interaction of asperities.
It was found that the RCF performance of CADI can be improved by microstructure control.
•Addition of carbides to ADI improves its RCF life and load carrying capacity.•Lowering graphite volume fraction of CADI improves its RCF life.•RCF life suddenly falls when a certain level of carbide is reached.•Lower nodule count with similar graphite volume fraction improves RCF life.•Carbide addition to ADI reduces nodule count but further additions do not.
The use of green-soluble inhibitors in the corrosive medium as alternatives to traditional inhibitors has increased due to the toxicity of the commonly used substances. These novel substances are ...selected owing to their low cost, ease of application as well as maintenance, and low environmental risk. This work aims to evaluate ethanolic-water extracts from post-harvest soybean (Glycine max) by-products as corrosion inhibitors for mild steel in an aggressive medium of sodium chloride. Soybean extracts were obtained by percolation at a controlled flow rate and temperature. To evaluate the anticorrosive efficiency, polarization curves of AISI 1030 steel were carried out at 1 and 7 days of immersion with different concentrations of the soybean extract. Weight loss measurements were carried out alongside potentiodynamic measurements. The steel samples were analyzed by scanning electron microscopy. The soybean extracts obtained reduced the corrosion rate of the steel, showing an efficiency of 30% at day 1. The inhibition efficiency increased up to 80% after 7 days of incubation with 2000 ppm of the extract. A Langmuir adsorption model was fitted to weight loss measurements. K
ads
and ΔG
ads
obtained from the model were characteristic of physisorption. The corrosion potential was shifted toward more negative values, classifying the ethanolic-water soybean extract as a cathodic inhibitor. The steel surface for the samples incubated with 2000 ppm of soybean extract was greatly improved showing significantly fewer agglomeration of corrosion products. Soybean leaves are a promising by-product useful to produce ethanolic-water extracts to be used as green corrosion inhibitors.
This work aims at developing a dynamic layer crystallizer operated batchwise, for freezing desalination of sea water. The experiments were performed with water/NaCl solutions and with samples of sea ...water from Nice, Rabat and Marseille. The pilot crystallizer consists of a cooled tube immersed in a cylindrical double jacketed tank. The solution is poured into the tank and the crystallization takes place on the external surface of the tube, by applying a cooling ramp in the tube. The solution is agitated by air bubbling. The whole process involves the freezing step, leading to the crystallization of the ice layer and the sweating step, which consists of purifying in depth the ice layer by melting the impure zones. A parametric study on the effect of the operating parameters has allowed quantifying the role of the different key parameters of the freezing and sweating steps. Three experiments allowed reaching salinities lower than 0.5g/kg, satisfying the standards of drinking water. The duration of the whole process dropped to only 8h (5h for freezing and 3h for sweating), with a yield of sweating equal to about 50%, provided severe conditions were applied for sweating. Higher yields required longer times. Overall, the results show the feasibility of the technique.
► Initial temperature, ice growth rate and solution salinity are the parameters affecting ice purity. ► The sweating step is able to efficiently complete the purification. ► The duration of the whole process dropped to only 8h (5h for freezing and 3h for sweating).
This book aims to help governments and public authorities to establish effective light rail-light metro transit (LRMT) systems, and focuses on use of Public-Private Participation (PPP) arrangements. ...Rather than identify a single approach, authors present options and discuss practical issues related to preparing and implementing new LRMT PPP schemes. The approach is focused on providing information that can be used to make informed decisions, adapted to local policy and objectives. The material presented is intended as a practical guide to developing LRMT PPPs in both developed and developing countries. This work endeavors to provide answers to readers' questions regarding how to successfully incorporate private sector participation in LRMT with a lesser emphasis on why LRMT and the private sector may be beneficial. The primary focus of this text is guiding the reader from design through to project implementation. It starts from the premise that underlying transport policy decisions will have already been made and that LRMT has already been identified as the appropriate transport solution. The authors have included some limited discussion of policy and technical issues where these directly impact the LRMT PPP approach. The approach is presented in nine sections, and in preparing it the author drew on current international LRMT PPP experience, through a series of interviews and case studies. The sections covered are: 1) urban transport and LRMT: an overview of urban transport policy, the characteristics of LRMT schemes and the influences on LRMT policies; 2) technical issues: a brief review of some key technical issues inherent in LRMT schemes and their potential impact on PPP design and implementation; 3) incorporating private sector participation in LRMT initiatives: what PPP has to offer, and an overview of the issues and stages public authorities follow to establish successful LRMT PPP arrangements; 4) understanding and managing risk: analyzing and allocating risks and responsibilities among stakeholders in the LRMT scheme and practical ways of designing risk allocation rules; 5) PPP, design, specifications and performance management: setting service standards and specifications and establishing associated costs; developing of performance and payment indicators and managing compliance; 6) funding and finance: large LRMT capital and system maintenance requirements require strong financing arrangements. The practical use of public and private financing mechanisms under PPP arrangement is reviewed; 7) developing a PPP agreement: looking at the main types of PPP agreements, an outline framework for developing the contractual arrangement is developed through re-view of key issues; 8) procurement: reviewing the approaches that the public authority can use to select the private partner; and 9) conclusions.
Bilayer Ti/TiN and TiAl/TiAlN coatings were deposited onto austempered ductile iron (ADI) substrates by cathodic arc deposition in an industrial device. Structure and mechanical properties of the ...coated samples were comparatively examined. Wear behavior of the coated samples was investigated in comparison with uncoated ADI by means of rolling contact fatigue (RCF) tests, performed in a flat washer type testing rig and using lubricated pure rolling conditions. RCF tests results were analyzed using the two-parameter Weibull distribution and the Weibayes method.
The results indicate that TiN and TiAlN coatings grew with a cubic-NaCl type structure. The arithmetic average roughness of the coated samples is similar for both coating variants. The surface hardness and residual stresses are higher for the TiAl/TiAlN coated samples. The coating hardness and elastic modulus are also higher for TiAl/TIAlN. The critical loads at massive delamination and the evolution of the friction coefficients are quite similar for both coating variants. Regarding RCF, failures in coated samples were characterized by substrate spalling. No massive delamination was observed in Ti/TiN and TiAl/TiAlN coatings. The statistical analysis indicates that the deposition of Ti/TiN improves noticeably the RCF resistance of ADI while the deposition of TiAl/TiAlN does not produce significant changes. The properties mismatch between substrate and coating seems to play an important role in the RCF behavior of coated samples, since Ti/TiN coatings possess a lower mismatch with respect to ADI substrates as compared to TiAl/TiAlN.
•Hardness, elastic modulus and residual stresses are higher for TiAl/TIAlN films.•Critical loads and friction coefficients are quite similar for both coating variants.•Wear was assessed by means of rolling contact fatigue (RCF) tests.•RCF failures in coated samples were characterized exclusively by substrate spalling.•RCF resistance can be ranked as follows: ADI-Ti/TiN>ADI-TiAl/TiAlN≈ADI.
The objective of Public Private Partnerships in the Water Sector: Innovation and Financial Sustainability is to determine, and make recommendations on, means of optimizing the use of Public Private ...Partnerships (PPP) in development of infrastructure whilst ensuring the sustainable long term provision of water and waste water services.
The effect of P deficiency on nodulation, nodule P content, nodule O-2 permeability and N fixation rates in Phaseolus vulgaris-rhizobia symbiosis was studied under glasshouse conditions. Four ...recombinant inbred lines (L34, L83, L115 and L147) and one variety cultivated in Morocco (Concesa) were inoculated with Rhizobium tropici CIAT 899 in hydroaeroponic culture. Two P levels i.e. 75 (deficient level) and 250 mu mol plant(-1) week(-1) P (sufficient level) were applied and the trial was assessed 42 days after transplanting that coincide with plant flowering stage. Under P-deficiency, decrease of plant growth (18%) and nodule biomass (19%) was detected and significantly pronounced in the sensitive line L147 compared with the remaining genotypes. Additionally, under P-deficiency, the efficiency in use of rhizobial symbiosis, estimated by the slope of the regression model of shoot biomass as a function of nodule biomass, was significantly increased in the four lines. This constraint did not significantly influence nodule P content in Concesa, but it was 24 and 41% lower in the tolerant and in the sensitive lines, respectively. Nodule P content was positively correlated to nodule biomass, r = 0.75, and shoot N, r = 0.92. These genotypic variations were associated with variability in nodule O-2 permeability that was significantly affected by the P level-bean genotype interaction. Under P-deficiency, nodule O-2 permeability was significantly reduced in the tested genotypes and accompanied with a decrease in shoot N content, especially in the sensitive lines (35%). Moreover, the ratios plant N fixed: nodule P content and plant N fixed: nodule dry weight were affected under P-deficiency in four lines with an exception observed in Concesa. Depending on the observed data we concluded that N-2 fixation efficiency could be influenced by nodulation and level of nodule P requirement which depend on both bean genotypes and P level.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Salinity is an increasing problem in Africa affecting rhizobia-legume symbioses. In Morocco, Phaseolus vulgaris is cultivated in saline soils and its symbiosis with rhizobia depends on the presence ...of osmotolerant strains in these soils. In this study, 32 osmotolerant rhizobial strains nodulating P. vulgaris were identified at the species and symbiovar levels by analysing core and symbiotic genes, respectively. The most abundant strains were closely related to Rhizobium etli and R. phaseoli and belonged to symbiovar phaseoli. A second group of strains was identified as R. gallicum sv gallicum. The remaining strains, identified as R. tropici, belonged to the CIAT 899TnodC group, which has not yet been described as a symbiovar. In representative strains, the otsA gene involved in the accumulation of trehalose and putatively in osmotolerance was analysed. The results showed that the phylogeny of this gene was not completely congruent with those of other core genes, since the genus Ensifer was more closely related to some Rhizobium species than others. Although the role of the otsA gene in osmotolerance is not well established, it can be a useful protein-coding gene for phylogenetic studies in the genus Rhizobium, since the phylogenies of otsA and other core genes are coincident at the species level.
This work aims in developing a static layer crystallizer for freezing desalination of sea water. The experiments were performed with a simple system of H(2)O-NaCl and with samples of sea water from ...Rabat. The pilot crystallizer consists in a tube cooled by means of a thermostatic bath. The tube is immerged in a cylindrical double jacketed tank cooled by means of a second thermostatic bath. The brine is poured into the tank and the crystallization takes place on the external surfacs of the tube. The global process is divided into 4 steps: (i) crystallization of the ice layer by controlling the cooling rate in the tube (ii) draining off the concentrated brine (iii) purification of the layer by sweating and (iv) melting of the ice to recover the fresh water. A parametric study of the effect of the operating parameters has allowed us to quantify the role of the different key parameters of the crystallization step. Within the studied domain, the purity of the crystalline layer was mainly affected by the initial salinity of the brine. The growth rate of the layer, controlled by the cooling rate in the tube, had also a significant effect. Experiments performed with Rabat sea water showed that a fresh water of salinity close to the drinking water standards could be obtained in one stage within 31 h. Desalination operated in two consecutive stages (10 h+11 h) gave salinity below the standards with a comfortable safety margin. If sufficiently severe operating conditions are applied, sweating is able to purify the interior of the ice layer and to reach the drinking water standards, provided the impurity concentration of the ice produced in the crystallization step is low enough. The mass loss induced by sweating is also high when the impurity concentration is high. These first results are promising and show the feasibility of the process which still requires to be optimized.
PDF
