Ranking proposed models for attaining surface free energy of powders using contact angle measurements

This study is an attempt to evaluate the applicability of various proposed mathematical models to calculate the surface free energy of commercially available powders. The capillary rise experiments were employed to achieve the contact angle between 15 powders and seven corresponding liquids by means of the modified Lucas–Washburn's equation. The surface free energy of powders was then calculated using different models inclusive of Owens/Wendt, harmonic mean, van Oss et al., combined mean (i.e. the combination of Owens/Wendt and harmonic mean models) and Li/Neumann models. Mathematical approaches were used to assess the accuracy of the calculated surface free energy and its components for different powders. A series of first-, second- and third-order functions as well as an exponential one were developed and put to test for one-, two- and three-parameter variables of liquid surface tension. Unfortunately, all such functions did not perform well in correctly estimating the contact angles of the liquid/powder systems (i.e. r² range being 0.48–0.68 and PF/3 range being 114–312). On the other hand, a series of trained artificial neural networks (ANNs) comparatively gave good correlations, predicting with unsurpassed accuracy the contact angles of the same corresponding liquid/powder systems (i.e. r² range being 0.93–0.94 and PF/3 range being 30–55). Therefore, the attained and tested ANNs were used further to provide the surface free energy of the 15 powders. In addition, the ANNs were also employed to rank the surface free energies of powders as well as their corresponding components as calculated by other models. The results showed that the geometric mean model was able to calculate the surface free energy of powders with more accuracy than all the other models.     

A new fuzzy network data envelopment analysis model for measuring the performance of agility in supply chains

Data envelopment analysis (DEA) is a linear programming method for assessing the efficiency and productivity of organizational units called decision-making units (DMUs). We propose a new network DEA (NDEA) model for measuring the performance of agility in supply chains. The uncertainty of the input and output data is modeled with linguistic terms parameterized with fuzzy sets. The proposed fuzzy NDEA model is linear and independent of the α-cut variables. The linear feature allows for a quick identification of the global optimum solution and the α-cut independency feature allows for a significant reduction in the computational efforts. We show that our model always generate solutions within a bounded feasible region. Our model also eliminates the potential for conflict by producing unique interval efficiency scores for each DMU. The proposed model is used to measure the performance of agility in a real-life case study in the dairy industry.     

Droplet heat and mass transfer in a turbulent hot airstream

A three-dimensional numerical model is developed to investigate the effect of turbulence on heat and mass transfer rates of a droplet exposed to a hot airstream. The airstream turbulence, temperature and mean Reynolds number are varied to provide a wide range of test conditions. The ambient pressure is kept atmospheric. In addition, variable thermophysical properties, transient gas and liquid phases, and the effect of radiation are all considered in the numerical study. The turbulence terms in the conservation equations of the gas-phase are modelled by using the shear-stress transport (SST) model. A Cartesian grid based blocked-off technique is used in conjunction with the finite-volume method to solve numerically the governing equations of the gas and liquid phases. The numerical results indicate that the effect of freestream turbulence is persistent although it weakens as the airstream temperature increases. The effect of radiation becomes significantly important at elevated airstream temperatures. Comprehensive droplet heat and mass transfer correlations are proposed, which take into consideration all the aforementioned variables.     

Influence of oxygen ingress on fine scale precipitation of α-Ti during oxidation of Beta21S β-Ti alloy

The formation of a surface oxide layer along with α precipitation in the subsurface oxygen-enriched zone, during the oxidation of a β-Ti alloy, has been investigated using scanning electron microscopy, electron probe micro analysis, X-ray diffraction, (Scanning) transmission electron microscopy, 3D-Atom Probe studies, and nano-indentation. Immediately below the nanocrystalline oxide layer, a two-phase mixture consisting of nanoscale equiaxed α grains and rutile grains are formed. With increasing depth, the α morphology below the oxide layer varied from nanoscale equiaxed to lathlike, coupled with substantial changes in size-scale and nucleation density of α precipitates. A distinct change in the lattice parameters of α and β phases below the oxide layer and the overall micro hardness of the material is also noted. The role of oxygen ingress on the scale and morphology of α precipitation has been discussed.     

Die Fähigkeit eines detaillierten Modells zur Diagnose axialer Verschiebungen in Transformatorwicklungen mit Hilfe von Übertragungsfunktionen

übersicht  Im Rahmen einer Forschungsarbeit wurde mit Hilfe einer Versuchsanordnung bestehend aus einer unverschachtelten Doppelscheibenspulenwicklung (ca. 1.3 MVA, 10 kV) und einer Vierfach-Lagenwicklung der Einfluss axialer Wicklungsverschiebungen auf die übertragungsfunktion n?her untersucht. Ein detailliertes mathematisches Modell wurde auf der Grundlage der Versuchsanordnung erstellt und ein Vergleich zwischen gemessenem und errechnetem Frequenzverhalten vollzogen. Neben einer zufriedenstellenden übereinstimmung zwischen Messung und Rechnung bei der Beschreibung des Frequenzverhaltens ist das Modell au?erdem in der Lage die Auswirkungen einer axialen Verschiebung korrekt wiederzugeben.

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Contents  Axial displacement of transformer windings has been studied in this research work using a test transformer. The transformer primary winding has 31 double disk coils (approx. 1.3 MVA, 10 kV) and the secondary is a four layer concentric winding. A detailed mathematical model was developed for the test object and a comparison was carried out between measured and calculated results. It is shown that this model can present the behavior of the transformer windings in the frequency domain in case of sound and displaced conditions.

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Eingegangen an 10. Oktober 2000     

Organic geochemistry of Gadvan and Kazhdumi formations (Cretaceous) in South Pars field,Persian Gulf,Iran

In Southern Iran, Gadvan (Barremian-early Aptian) and Kazhdumi (Albian) formations are the most effective source rocks and have produced the majority of hydrocarbons reserved in the Zagros Basin especially in Dezful Embayment and Persian Gulf area. In this article, hydrocarbon potential of Gadvan and Kazhdumi formations is investigated in the South Pars field which is southern extension of the North field of Qatar Country. This field is located in Persian Gulf waters and is actually the northern extension of Qatar Arc Paleohigh where geological history of Gadvan and Kazhdumi formations is different from nearby area regarding depositional setting, burial history and source rock maturity.In this study, Gadvan and Kazhdumi formations as source rock candidates, which underlay Upper Dariyan and Mauddud members, respectively, were sampled in two drilled wells of the South Pars field for routine geochemical analysis to investigate hydrocarbon potential of these formations and source rock identification of trapped oil in the Upper Dariyan and Mauddud members. Several samples from top to the bottom of the formations were taken and analyzed by Rock-Eval pyrolysis. The average TOC content of Gadvan and Kazhdumi formations is 0.79 wt. % and 0.49 wt. %, respectively. Rock-Eval results (e.g. HI vs. Tmax) represent that TOC content of these formations contains type II-III kerogens which haven't suffered sufficient thermal maturity (Ro < 0.5%) in this study area. Moreover calculated S2/S3 ratio implies that these formations in central part of Qatar Arc, South Pars field couldn't produce noticeable liquid hydrocarbon.As it is believed, Gadvan and Kazhdumi formations to be source of trapped oil in the system, therefore, in the South Pars field reserved hydrocarbon in Upper Dariyan (Aptian) and Mauddud (late Albian) members which overlie Gadvan and Kazhdumi formations, respectively, are probably generated from Gadvan and Kazhdumi formations of the nearby through and flanks of the Qatar Arc where the burial depth and temperature increase then generated hydrocarbons in downdip area are migrated to the upper carbonate reservoirs in the crest part of the Qatar Arc. Long path migration of the hydrocarbon and source rock with lower organic matter are caused hydrocarbon accumulation in the South Pars Oil Layer (Al-Shaheen) which is approved by professional petrophysical and geological studies of the field.     

Investigating the antigraffiti properties of a polyurethane clearcoat containing a silicone polyacrylate additive

In this study, a polyurethane clearcoat was modified using a silicone polyacrylate antigraffiti additive and its surface free energy and mechanical properties were evaluated by various analytical techniques. The results showed that surface free energy decreased by replacing the polyol resin with the additive up to 10 mol%. Dynamic mechanical thermal analysis (DMTA) showed that the presence of the additive increased the storage modulus of the samples at ambient temperature. Evaluation of stainability of the coatings containing the additive revealed that a spray paint would be repelled from the surface showing a proper antigraffiti behavior. The additive did not affect the surface roughness of the films, indicating that the antigraffiti properties resulted from changes in surface chemistry due to migration of the additive to the surface.     

Exploiting linked data to create rich human digital memories

Memories are an important aspect of a person’s life and experiences. The area of human digital memories focuses on encapsulating this phenomenon, in a digital format, over a lifetime. Through the proliferation of ubiquitous devices, both people and the surrounding environment are generating a phenomenal amount of data. With all of this disjointed information available, successfully searching it and bringing it together, to form a human digital memory, is a challenge. This is especially true when a lifetime of data is being examined. Linked Data provides an ideal, and novel, solution for overcoming this challenge, where a variety of data sources can be drawn upon to capture detailed information surrounding a given event. Memories, created in this way, contain vivid structures and varied data sources, which emerge through the semantic clustering of content and other memories. This paper presents DigMem, a platform for creating human digital memories, based on device-specific services and the user’s current environment. In this way, information is semantically structured to create temporal “memory boxes” for human experiences. A working prototype has been successfully developed, which demonstrates the approach. In order to evaluate the applicability of the system a number of experiments have been undertaken. These have been successful in creating human digital memories and illustrating how a user can be monitored in both indoor and outdoor environments. Furthermore, the user’s heartbeat information is analysed to determine his or her heart rate. This has been achieved with the development of a QRS Complex detection algorithm and heart rate calculation method. These methods process collected electrocardiography (ECG) information to discern the heart rate of the user. This information is essential in illustrating how certain situations can make the user feel.     

CFD modeling of the effect of absorbent size on absorption performance of a packed bed column

This paper reports a study on the ability of the computational fluid dynamics (CFD) modeling for analyzing the fluid flow hydrodynamics and absorption in a packed bed column. The water absorption by silica gel absorbents in an experimental packed bed was investigated, and the absorption performance of two different sizes of absorbent was studied. A series of experiments were carried out for five setups which are different in the weight ratio of the employed big to small absorbents. The CFD modeling was carried out for all five experimental setups. The predicted results show that by more replacing of the big absorbents with the small ones the water absorption increased. On the other hand, a greater pressure drop was observed as more small absorbents were used. The predicted absorption rates were compared with the measured values and on average a consistency within 11.6% was observed.