Inspection interval optimization for complex equipment in automotive manufacturing under dependent failures

Forschung im Ingenieurwesen - Inspection activities in automotive manufacturing play a crucial role in diagnosing and preventing unexpected failures by adopting the well-planned intervals....     

Effects of hot water pre-extraction on surface properties of bagasse soda pulp

In this work, the effects of hot water pre-extraction of depithed bagasse on the soda pulping and surface properties were studied. The conditions of hot water pre-extraction were: maximum temperature 170 °C, heat-up time 90 min, time at maximum temperature 10 min, and solid to liquor ratio (S:L) 1:8. Consequently, the pre-extracted and un-extracted bagasse chips were subjected to soda pulping at 160 °C for 1 h with 11, 14 and 17% active alkali charge and an S:L of 1:5. The results showed that the hot water pre-extraction increased bagasse surface texture porosity by hemicellulose degradation. Therefore, the delignification was faster for pulping of pre-extracted samples. At a certain charge of alkali, pre-extracted samples showed higher screened yield and lower Kappa number. For instance, at 17% alkali charge, pre-extracted bagasse gave 11.3% higher pulp yield compared with the un-extracted ones. Inverse gas chromatography (IGC) results showed that the hot water pre-extraction changed the active sites on the bagasse surface, decreasing the dispersive energy and the basicity character, and affected the particle morphology. The pulping process decreased the hydrophobicity and the basicity of the bagasse surface. The surfaces of un-extracted and pre-extracted bagasse pulps had similar properties but different morphology. The pulps present higher surface area and permeability with more reactive capacity.     

A comparative study on the effects of Coriolus versicolor on properties of HDPE/wood flour/paper sludge composites

In this study, the effects of white-rot fungus (Coriolus versicolor) on the properties of high density polyethylene (HDPE)/wood flour/paper sludge composites were examined. In addition, the effectiveness of using coupling agent on the durability of decayed and undecayed WPCs was investigated. Two different types of sludge materials, namely paper making waste water sludge (PS) and ink-eliminated sludge (IES) were used. The mechanical properties, morphology, and water absorption of fabricated composites were investigated. At a similar wood flour loading, except for modulus of elasticity, the fungi treated composites showed lower mechanical properties (such as modulus of rupture and unnotched Izod impact strength), and higher water absorption compared to untreated composites. According to the results, addition of wood flour decreased the resistance of the composites to moisture and fungal environment. The exposure of the composites to a 4-cycle (2, 24, 48 and 72 h) water immersion caused serious damage to the interfacial adhesion between wood flour and polymer matrix due to contraction and swelling stresses developed during the cyclic exposure. The detrimental effect of fungal treatment on the water uptake of the composites could be explained by the degradation of lignin which made the cellulose content more accessible. Further, it makes chains of cavities that accelerate water absorption. However, the weight losses of all cases of treated composites were low (less than 2.5%), while PS filled composites were more susceptible to white-rot fungi. The addition of coupling agent during the compounding of wood flour and HDPE prevented the colonization and proliferation of fungus on the surface of the composites, and had an advantageous effect on the water uptake and mechanical properties of both treated and untreated composites.     

Using the mixture-tuned matched filtering method for lithological mapping with Landsat TM5 images

Hyperspectral images are widely employed for geological mapping because of their high spectral resolution. In this article, we develop the mixture-tuned matched filtering (MTMF) method, which can provide highly accurate mapping using the minimum ground-based data. This method is applied in the Malayer region of western Iran, which is composed of various lithological units. MTMF and minimum noise fraction (MNF) methods were applied to a Thematic Mapper 5 (TM5) image, and minimum number of training data based on field observation were used to produce a suitable false-colour image in which locations of lithological units were given. Finally, classification of six desired lithological units was done by the maximum likelihood classification (MLC) method. Results of lithological mapping show that although minimum ground-based data were used, the accuracy of classification is 82.3%. In addition, evaluation of the above-mentioned false-colour image reveals that the algorithm presented enhances the separability of units in the image by 7.3%, which can partially compensate for the low spectral resolution of the image used.     

Liapunov‐type inequality for universal integral

The Choquet integral and the Sugeno integral provide a useful tool in many problems in engineering and social choice where the aggregation of data is required. In this paper, previous results of Hong (Nonlinear Analysis 2011 74:7296–7303) are improved by relaxing some of their requirements. Carlson's, Sandor's, Bushell–Okrasinski's type inequalities and Fatou's lemma for universal integral are studied in a rather general form, thus generalizing some recent results. © 2012 Wiley Periodicals, Inc.     

Forced convection heat transfer of Williamson fluid flow in porous media over horizontal plate with constant heat flux

Forced convection of Williamson fluid flow in porous media under constant surface heat flux conditions is investigated numerically. A model of Darcy–Forchheimer–Brinkman is used and the corresponding governing equations are expressed in dimensionless forms and solved numerically using bvp4c with MATLAB package. Boundary layer velocity, shear stress, and temperature profiles, in addition to the local Nusselt number parameter over a horizontal plate, are found. The effects of the Forchheimer parameter, Nusselt number, Darcy parameter, porous inertia, and Williamson parameter on the velocity profiles, temperature profiles, coefficient of friction, and coefficient of heat transfer are investigated. The results showed that as the Darcy parameter increases, boundary layer velocity and shear stress increase, while the temperature and Nusselt number decrease. In addition, as Williamson's parameter increases, velocity within the boundary layer, shear stress, and Nusselt number decrease while the temperature profile increases. Also, with larger values of the Forchheimer parameter, the velocity of the boundary layer, shear stress, temperature, and Nusselt number increase. Furthermore, the Nusselt number and the coefficient of friction are obtained on the surface of the horizontal plate.     

Selective Degradation of Lignin Polymer by Chlorine Dioxide During Chemical Pulp Delignification in Flow Through Reactor

The delignification of pulp in a conventional batch reactor provides convenient conditions for inutile secondary reactions in which ClO₂ reacts with oxidized aromatic units of lignin. In this study the flow-through reactor was applied to minimize secondary reactions. The obtained results showed that the removal of oxidized lignin from the reaction zone significantly enhanced the ClO₂ reaction toward non-oxidized units of lignin. Application of an organic solvent-water solution, bleaching liquor, significantly increased the removal of oxidized lignin and decreased considerably the secondary reactions. Although this technique considerably improved ClO₂ effective efficiency, large amounts of chlorate formation decreased the overall effect of improved ClO₂ global efficiency.     

The effect of variable stator on performance of a highly loaded tandem axial flow compressor stage

Increasing the aerodynamic load on compressor blades helps to obtain a higher pressure ratio in lower rotational speeds.Considering the high aerodynamic load effects and structural concerns in the design process,it is possible to obtain higher pressure ratios compared to conventional compressors.However,it must be noted that imposing higher aerodynamic loads results in higher loss coefficients and deteriorates the overall performance.To avoid the loss increase,the boundary layer quality must be studied carefully over the blade suction surface.Employment of advanced shaped airfoils (like CDAs),slotted blades or other boundary layer control methods has helped the designers to use higher aerodynamic loads on compressor blades.Tandem cascade is a passive boundary layer control method,which is based on using the flow momentum to control the boundary layer on the suction surface and also to avoid the probable separation caused by higher aerodynamic loads.In fact,the front pressure side flow momentum helps to compensate the positive pressure gradient over the aft blade's suction side.Also,in comparison to the single blade stators,tandem variable stators have more degrees of freedom,and this issue increases the possibility of finding enhanced conditions in the compressor off-design performance.In the current study,a 3D design procedure for an axial flow tandem compressor stage has been applied to design a highly loaded stage.Following,this design is numerically investigated using a CFD code and the stage characteristic map is reported.Also,the effect of various stator stagger angles on the compressor performance and especially on the compressor surge margin has been discussed.To validate the CFD method,another known compressor stage is presented and its performance is numerically investigated and the results are compared with available experimental results.