Numerical and experimental studies of the base pressures beneath stockpiles

Stockpiles are common for storage of bulk solids in many industrial sectors. One interesting phenomenon is that there is a significant dip of the base pressure beneath the apex of the pile which may have significant implications in the design of stockpile facilities and related support structures. This paper presents a numerical and experimental study of this phenomenon. Experiments have been conducted to measure the base pressure distribution under a stockpile formed with iron ore pellets and significant central stress minimum was revealed. Continuum analysis using the finite element method (FEM) was conducted to simulate the stress distribution in the test pile. It showed the critical importance of progressive pile development and nonlinear constitutive models. To investigate the underlying mechanisms further, simulations using the discrete element method (DEM) were conducted, which related well to the FEM predictions and revealed key aspects of the inter-particle force patterns. Both the FEM and DEM predictions show a dip in the base pressure distribution which is in agreement with test results, and reveal new key features of the mechanics of such piles.     

Combustion of chlorinated VOC on nanostructured chromia aerogel as catalyst and catalyst support

The chromia-based catalysts have been reported to combine the high activity and resistance to deactivation in oxidative removal of chlorinated VOC. However, their activity is limited by the low amount of chromia that can be deposited on supports maintaining the optimal state of surface species and high surface area. The pure nanostructured chromia was used as a catalytically active support for noble metals and transition-metal oxide oxidation catalysts. High efficiency of Pt-promoted CrOOH aerogel with surface area of 500 m2*g(-1) was demonstrated in full combustion of 1,2-dichloroethane (DCE) and chlorobenzene (CB). At gas hour space velocity (GHSV) of 46 000 h(-1), the total conversion to CO2/H2O/HCl was achieved at 330 degrees C (DCE) and 380 degrees C (CB). The combustion rate constants measured at standard conditions with 0.5% Pt/CrOOH catalyst were 1 or 2 orders of magnitude higher than measured with 15%Cr2O3/Al2O3 or 0.5%Pt/Al2O3, respectively. The effects of Pt, Au, Mn, and Ce additives on the performance of CrOOH aerogel in combustion of chlorinated VOC were analyzed related to the materials structure.     

Incorporation of dielectric layers into the processing of III-nitride-based heterostructure field-effect transistors

Dielectric layers within III-nitride transistor technology can act either as passivation layers or as gate-dielectric layers. In this paper, we reflect on both issues and present novel approaches of dielectric schemes. In both cases, the elimination of surface traps or, more generally, of surface states is a key issue in obtaining improved device performance. As gate dielectrics, we introduced and investigated thermally and photoelectrochemically generated Al_xGa_2−xO₃, SiO₂, the combination of Al_xGa_2−xO₃ and SiO₂ (tandem-dielectric stack), and e-beam-deposited Al₂O₃. These dielectric layers serve simultaneously as a passivation layer. In addition, we introduced plasma-enhanced chemical-vapor deposition (PECVD)-deposited SiN_x for passivation. The results highlight the importance of passivation and the introduction of gate dielectrics and emphasize the relationship between surface states and improved direct-current (DC) performance. Backed by additional measurements, we proposed a different gateleakage mechanism for heterostructure field-effect transistor (HFET) and metal-oxide semiconductor heterostructure field-effect transistor (MOSHFET) devices.     

Effectiveness of density segregation and sodium carbonate treatment on the detoxification of Fusarium-contaminated corn fed to growing pigs

The effectiveness of using rinsing, density segregation or 0.1 M sodium carbonate treatments of Fusarium-contaminated corn containing deoxynivalenol (DON) and zearalenone were tested both chemically and by feeding the material to growing pigs. Uninfected and Fusarium graminearum-inoculated corn (containing 40.3 mg DON and 0.94 mg zearalenone kg^?1cor) were subjected to various treatments: no treatment (control), rinsed, rinsed and all floating material removed, soaked in 0.1 M sodium carbonate for 24 h or soaked in 0.1 M sodium carbonate for 24 h after removal of the floating material. All corn samples were analysed for DON and zearalenone. Rinsing the contaminated corn reduced the concentrations of both mycotoxins by 44% while soaking in 0.1 M sodium carbonate reduced the toxin concentrations an additional 35%. In both cases, removal of the floating material decreased concentrations another 8 and 4%, respectively. In the feeding study, 10-week-old barrows were fed diets containing 17.5% of the treated corn samples over a 21 day period. Daily feed consumption and weight gains were significantly improved in pigs fed the rinsed-minus-floating corn and the sodium carbonate-soaked corn with and without floating material compared to the untreated contaminated corn. The chemical and biological data demonstrated that rinsing combined with the removal of floating material or soaking in 0.1 M sodium carbonate with or without removal of floating material were effective in reducing the toxicity of the contaminated corn. Due to a higher energy requirement needed to dry the corn soaked in sodium carbonate, the combination of rinsing and removal of the floating material is recommended as a more general and practical method of detoxification of contaminated grain.     

Imperfection measurement of cylinders using automated scanning with a laser displacement meter

Geometric imperfections, commonly in the form of depressions at the circumferential welds, are present in most metal silo structures and can greatly reduce the structure's buckling strength. These imperfections sure close to axisymmetric in form. This paper describes the measurement system which was developed for an experimental study of this phenomena. Computer controlled steppennotors for both Hie circumferential and longitudinal travel of the measurement carriage provided a precise and repeatable traverse of the specimen. A laser displacement meter, which is capable of high speed, non-contact measurement and has a resolution of 0.5 microns, was controlled synchronously with the steppennotors to provide a very accurate three-dimensional measurement system. Both the initial geometrically imperfect shape and the progressive growth of deformations during loading were accurately measured.     

Elektrophoretisches Isolieren mit Glimmer

Insulating process by electro deposition of mica . Metallic surfaces with anode potential in a dc-circuit can be coated with mica by submersion in aqueous dispersions of mica particles. Such coatings are high quality insulations, which in a number of cases already are used in electrotechnical fabrications. The following applications in the production of rotating machines are described:

• 1 Insulation of commutating poles, wound with rectangular copper wire.
• 2 Electro deposition of mica on the bare ends of wound rotors.
• 3 Insulation of commutator connections of large dc-machines.

     

Generalized expectancies for interpersonal trust.

Describes results of a program of research on interpersonal trust, defined as belief in social communications. Construction of a scale for measuring individual differences, construct validity studies, and investigations of antecedents of trust, correlates of trust, and changes of college student trust are included. The evidence supports the hypothesis of (a) stable individual differences in a generalized expectancy for interpersonal trust, and (b) the feasibility of studying such trust under a variety of conditions. (29 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)