Review and simplification of calculations in15N tracer studies

Calculations in nitrogen (N) balance research using¹⁵N involve several steps that require care to avoid errors. The objective of this paper is to provide examples of these calculations using established procedures and to present shortened alternative calculations that give the same result. The calculations examined include determination of the amount of N to apply, determination of the atom %¹⁵N abundance needed in the labeled fertilizer, preparation of the labeled fertilizer, and calculation of the fertilizer N recovered. Calculations needed in the preparation of the labeled fertilizer using established procedures include the determination of the mean atomic weight of the enriched source from which the labeled fertilizer is prepared. This determination is not needed in the shortened alternative calculations, because the procedure places the calculations on a mole basis rather than a mass basis.     

Producing High-Quality Titanium Alloy by a Cost-Effective Route Combining Fast Heating and Hot Processing

Powder metallurgy is a very attractive method for producing titanium alloys, which can be near-net-shape formed and have freedom in composition selection. However, applications are still limited due to product affordability. In this paper, we will discuss a possible cost-effective route, combining fast heating and hot processing, to produce titanium alloys with similar or even better mechanical properties than that of ingot metallurgy titanium alloys. Two titanium alloys, Ti-5Al-5V-5Mo-3Cr (Ti-5553) and Ti-5Fe, were successfully produced from HDH titanium powder and other master alloy powders using the proposed processing route. The effect of the processing route on microstructural variation and mechanical properties have been discussed.     

Graphene coating assisted injection molding of ultra‐thin thermoplastics

High strength light weight parts are critical for the development of new technologies, particularly electronic devices, such as laptop computers, smart phones, and tablet devices. Injection molded plastics and composites are excellent choices for mass producing such parts. As the part thickness decreases from traditional injection molding (>2 mm thickness) to thin wall molding (～1 mm thickness), and lastly, to ultra‐thin wall molding (<0.5 mm thickness), avoiding incomplete filling (short shots) becomes more challenging. Even though, methods exist today for molding thin‐wall plastic parts (i.e., fast heating/fast cooling injection molding), they require multiple steps resulting in a noncost efficient process. In this article, we demonstrate the technical feasibility of using graphene coating to facilitate flow, by promoting slip at the mold walls. We evaluate the influence of coated and uncoated mold inserts on fiber orientation. We present experimental results using un‐reinforced polypropylene and a 40% by weight carbon fiber reinforced polycarbonate/acrylonitrile butadiene styrene. POLYM. ENG. SCI., 55:1374–1381, 2015. © 2015 Society of Plastics Engineers     

Use of fluoropolymer permanent release coatings for molded polyurethane foam production

The problem of adhesion of polyurethane foams to fluoropolymer permanent release mold coatings was studied. Two coatings, based on polytetrafluoroethylene (PTFE) and perfluoroalkoxy polymer (PFA) aqueous dispersions, respectively, were applied on aluminum plates, and the foam release performance evaluated. The PTFE coating displayed gradual loss of antiadhesion properties with consecutive exposure to the reactive mixture, which was associated with isocyanate surface penetration. Penetrant mass uptake experiments, performed on free films, indicated that PTFE retains about 10 times more isocyanate than PFA, probably because of its porous surface morphology. A synergistic effect was found by applying a very small quantity of a waterborne release agent on the PTFE coating, before every foam molding cycle. The release agent formed a protective barrier that minimized contact of the coating with the reactive mixture, allowing for stable and robust foam release performance. The problem of polyurea build-up, associated with the use of aqueous release agents, was not observed because of the small amounts of compound used.     

Identification of temperature and moisture content fields using a combined neural network and clustering method approach

Studies on the dynamics of temperature and moisture content distributions in porous soils have provided important insight on their effect on the building hygrothermal behavior, where the interaction between both building and soil can contribute to reduce building thermal gains or looses. Hygrothermal aspects can be related to many attributes such as energy consumption, occupants' thermal comfort and health, and material deterioration. Recently, a great variety of mathematical models to predict thermal and moisture content profiles in porous media have been presented in the literature. Most of those models are based on analysis of multilayer measurements or on Fourier analysis. The development and validation of such mathematical models facilitate the understanding of heat and moisture flows at different soil depths. In this research, a radial basis function neural network (RBF-NN) approach, combined with Gath–Geva clustering method in order to predict the temperature and moisture content profiles in soils, has been presented. A set of data obtained from the computation of the coupled heat and moisture transfer in porous soils for the Curitiba city (Paraná State, Brazil) weather data file has been used by the RBF-NN modeling method. Simulation results indicate the potentialities of the RBF-NNs to learn, for the one step ahead identification, the behavior of temperature and moisture content profiles in the media at various depths.     

CONJUGATE HEAT AND MASS TRANSFER IN CONVECTIVE DRYING OF MULTIPARTICLE SYSTEMS. PART I: THEORETICAL CONSIDERATIONS

Abstract

This is the first of two papers concerning conjugate transport in convective drying of multiparticle systems. In this study, a methodology for the solution of conjugate transport problems is proposed. The theoretical aspects and relevant assumptions are briefly discussed and the results for convective heat and mass transfer in assemblages of spheres are presented. It is shown that both heat and mass transfer rates for an assemblage of two spheres in tandem arragement are significantly different from those of a single sphere case, and that care should be taken when modeling multiparticle systems by means of single-particle analysis.     

Recovery of carbon dioxide from sugarcane fermentation broth in the ethanol industry

Ethanol is one alternative to the use of petroleum-based fuels. It is produced on a large scale in Brazil from sugarcane to the magnitude of billions of liters per year. During the ethanol production step, a considerable amount of byproducts is obtained and treated as waste. Carbon dioxide is one of these byproducts and a substance of interest especially for food industries. Because the production of 1000 kg of ethanol generates approximately 950 kg of CO₂, this work intends to analyze a cryogenic distillation process for the production of CO₂ by means of computational simulations. The results obtained were in agreement with real operational conditions, achieving CO₂ concentrations up to 100% (v/v). With an initial CO₂ concentration of 95% (v/v), 7 separation stages were obtained, achieving the limit of 5 stages for higher CO₂ concentrations in the raw gas. The effect of initial CO₂ concentrations on the final product and the concentration profiles along the column are also presented. In order to optimize the process, it was observed that, for a maximum feed flow of 3333 kg/h (CO₂ concentration of 99%), the plant was able to obtain 10.48 kgCO₂/kW, recovering about 2828 kgCO₂/h at a final product concentration of 99.90% (v/v) at ?25 °C.     

CONJUGATE HEAT AND MASS TRANSFER IN CONVECTIVE DRYING OF MULTIPARTICLE SYSTEMS PART II: SOYBEAN DRYING

Abstract

This is the second of two papers concerning conjugate transport in convective drying of multiparticle systems. In the first paper (part 1), a solution methodology for conjugate transport problems was porposed and successfully tested for assemblages of spheres. This paper deals with the application of the proposed methodology to a soybean drying problem. The analysis in this study allowed certain phenomena, that are usually not present in single-kernel and deep-bed drying analyses, to be captured by the drying rate curves. The results presented here reinforce the need to take into account particle interactions when studying the drying mechanisms of multiparticle systems.     

New smooth test statistics of goodness-of-fit for categorized composite null hypotheses

Testing for goodness-of-fit is possible in a parametric setup by using smooth test statistics. This approach relies on embedding the probability model to be selected, in a larger parametric model. This reduces the problem of testing goodness-of-fit to the simpler problem of testing whether a parameter is zero. In this paper, new classes of smooth test statistics are introduced for categorized data and their asymptotic distributions are obtained under composite null hypotheses. Supported by the grants DGES PB-96 0635 and GV99-159-1-01