Gasification of biomass: comparison of fixed bed and fluidized bed gasifier

Gasification as a thermochemical process is defined and limited to combustion and pyrolysis. A systematic overview of reactor designs categorizes fixed bed and fluidized bed reactors. Criteria for a comparison of these reactors are worked out, i.e. technology, use of material, use of energy, environment and economy. A utility analysis for thermochemical processes is suggested. It shows that the advantages of one of the reactor types are marginal. An advantage mainly depends on the physical consistency of the input. As a result there is no significant advantage for the fixed bed or the fluidized bed reactor.     

Relationship problems in the early stages of marriage: A longitudinal investigation.

131 couples (aged 16–35 yrs) were assessed premarriage for relationship problems and adjustment. At each follow-up (12 wks and 1.5, 3, 4, and 5 yrs) a portion of the sample completed an interview, a set of interaction tasks, and the questionnaire. Consistent patterns were found among 3 methods (mean problem intensity, percentage checked in problem areas, and percentage ranked) of assessing couples' problems. Subsequent analyses on problem intensity ratings indicated a moderately strong association between male and female ratings at each stage of family development. Changes in clusters of problems were found between stages consistent with some changes in developmental tasks predicted by stage theories of family development. Support was found for the assumption that men and women confront developmental tasks at different rates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microbial Cell Wall Constituents in Indoor Air and their Relation to Disease

Abstract This presentation reviews the relation between damp buildings, mold growth and symptoms and disease among persons living or working in such buildings. Epidemiological studies on these relationships date back to 1924 and at present there are almost 30 large-scale investigations. There is an almost general concordance between studies on the relation between damp buildings and symptoms of the airways. Most of the studies show also a relation between symptoms and reported or measured mold growth. The symptoms reported are remarkably similar in the different studies: nose or throat irritation, wheezing, dry cough and fatigue. It is suggested that this symptom profile reflects a non-specific airways inflammation and that antigen-mediated allergy is rare. Regarding agents capable of inducing airways inflammation, data on bacterial endotoxin demonstrate a causal relationship, whereas information on another microbial wall agent - (1→3)-β-D-glucan - is suggestive but not conclusive of a causal relationship. From a practical point of view, dampness and previous mold growth represent conditions in buildings where renovation should be undertaken, particularly if there are symptoms of airways inflammation among the occupants.     

Mesh objective continuum damage models for ductile fracture

During machining processes, the work piece material is subjected to high deformation rates, increased temperature, large plastic deformations, damage evolution and fracture. In this context the Johnson‐Cook failure model is often used even though it exhibits pathological mesh size dependence. To remove the mesh size sensitivity, a set of mesh objective damage models is proposed based on a local continuum damage formulation combined with the concept of a scalar damage phase field. The first model represents a mesh objective augmentation of the well‐established element removal model, whereas the second one degrades the continuum stress in a smooth fashion. Plane strain plate and hat specimens are used in the finite element simulations, with the restriction to the temperature and rate independent cases. To investigate the influence of mesh distortion, a structured and an unstructured meshes were used for the respective specimen. For structured meshes, the results clearly show that the pathological mesh size sensitivity is removed for both models. When considering unstructured meshes, the mesh size sensitivity is more complex as revealed by the considered hat‐specimen shear test. Nevertheless, the present work indicates that the proposed models can predict realistic ductile failure behaviors in a mesh objective fashion. Copyright © 2015 John Wiley & Sons, Ltd.     

Isokinetic effects in ethane hydrogenolysis and their relation to the mechanism of the reaction

Literature data on the kinetics of ethane hydrogenolysis over metal catalysts are used to indicate the existence of isokinetic temperatures, . For platinum = 725 K, for Ni is probably in the same temperature range. For Fe and Co on the other hand is found at much lower values, about 330 K for Fe and 320 K for Co. From an analysis of the model of selective energy transfer, these values support the proposition of Sinfelt that the elements of high atomic number in one and the same transition metal series favour the splitting of the carbon-carbon bond as rate determining step, whereas those elements that have lower atomic numbers cause the splitting of the metal-carbon bond to be the rate determining step.     

Über die Benutzung der Wahrscheinlichkeitstheorie für Telephonverkehrsprobleme

Electrical Engineering -     

The influence of stabilizers on the fusion of rigid poly(vinyl chloride)

It is known that the fusion rate of rigid PVC in an extruder partly depends upon the lubricants that are used. In the present study it is shown that different stabilizers have a great influence upon the rate of fusion of rigid PVC. Results from extrusion experiments and the Brabender Plastograph strongly indicate that a correlation exists between rapid melting in the extruder and the melt viscosity-temperature relation of the polymer blend. The reason why certain stabilizers cause a more rapid fusion of the PVC is attributed to the chemical structure of the stabilizers.     

Extensions to “Output prediction under scarce data operation: control applications”

Albertos et al. (Automatica, 35 (1999) 1671–1681), proposed a simple and computationally cheap output estimation algorithm for systems where some output data is missing. In the original paper, a stability analysis of the algorithm is provided for the special case that every Nth sample of the output is observed. We here show how the stability can be analysed for arbitrary periodical missing data patterns.