The effect of air preheating in a biomass CFB gasifier using ASPEN Plus simulation

In the context of climate change, efficiency and energy security, biomass gasification is likely to play an important role. Circulating fluidised bed (CFB) technology was selected for the current study. The objective of this research is to develop a computer model of a CFB biomass gasifier that can predict gasifier performance under various operating conditions. An original model was developed using ASPEN Plus. The model is based on Gibbs free energy minimisation. The restricted equilibrium method was used to calibrate it against experimental data. This was achieved by specifying the temperature approach for the gasification reactions. The model predicts syn-gas composition, conversion efficiency and heating values in good agreement with experimental data. Operating parameters were varied over a wide range. Parameters such as equivalence ratio (ER), temperature, air preheating, biomass moisture and steam injection were found to influence syn-gas composition, heating value, and conversion efficiency. The results indicate an ER and temperature range over which hydrogen (H₂) and carbon monoxide (CO) are maximised, which in turn ensures a high heating value and cold gas efficiency (CGE). Gas heating value was found to decrease with ER. Air preheating increases H₂ and CO production, which increases gas heating value and CGE. Air preheating is more effective at low ERs. A critical air temperature exists after which additional preheating has little influence. Steam has better reactivity than fuel bound moisture. Increasing moisture degrades performance therefore the input fuel should be pre-dried. Steam injection should be employed if a H₂ rich syn-gas is desired.     

Opportunity for interaction? A naturalistic observation study of dual-earner families after work and school.

Everyday patterns of interaction can strengthen or undermine bonds between family members. This naturalistic observation study focused on an understudied facet of family life: opportunities for interaction among dual-earner family members after work and family members’ responses to these opportunities. Thirty dual-earner couples and their children were observed and video-recorded in their homes throughout two weekday afternoons and evenings. Two interaction opportunities were analyzed: (1) the behavior of family members toward a parent returning home from work and (2) the physical proximity of family members throughout the evening. Three main findings emerged. Women, who tended to return home before men, were greeted with positive behavior and reports of the day’s information from family members. Men, in contrast, returned home later in the day and received positive behavior or no acknowledgment from family members distracted by other activities. Throughout the evening, mothers spent more time with children whereas fathers spent more time alone. Couples were seldom together without their children. The implications of observed interaction patterns and the contribution of naturalistic observation methods to the study of family relationships are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integration testing of object‐oriented components using finite state machines

In object‐oriented terms, one of the goals of integration testing is to ensure that messages from objects in one class or component are sent and received in the proper order and have the intended effect on the state of the objects that receive the messages. This research extends an existing single‐class testing technique to integration testing of multiple classes. The single‐class technique models the behaviour of a single class as a finite state machine, transforms the representation into a data flow graph that explicitly identifies the definitions and uses of each state variable of the class, and then applies conventional data flow testing to produce test case specifications that can be used to test the class. This paper extends those ideas to inter‐class testing by developing flow graphs, finding paths between pairs of definitions and uses, detecting some infeasible paths and automatically generating tests for an arbitrary number of classes and components. It introduces flexible representations for message sending and receiving among objects and allows concurrency among any or all classes and components. Data flow graphs are stored in a relational database and database queries are used to gather def‐use information. This approach is conceptually simple, mathematically precise, quite powerful and general enough to be used for traditional data flow analysis. This testing approach relies on finite state machines, database modelling and processing techniques and algorithms for analysis and traversal of directed graphs. The paper presents empirical results of the approach applied to an automotive system. This work was prepared by U.S. Government employees as part of their official duties and is, therefore, a work of the U.S. Government and not subject to copyright. Published in 2006 by John Wiley & Sons, Ltd.     

Comparative Investigation of Hoveyda–Grubbs Catalysts bearing Modified N‐Heterocyclic Carbene Ligands

This paper reports the structural modification of Hoveyda–Grubbs complexes through the introduction of either an N‐alkyl‐N′‐mesityl heterocyclic carbene, an N‐alkyl‐N′‐(2,6‐diisopropylphenyl) heterocyclic carbene, or an N‐alkyl‐N′‐alkyl heterocyclic carbene. The effect of the modified N‐heterocyclic carbene (NHC) ligand was investigated in representative ring‐opening metathesis polymerization (ROMP), ring‐closing metathesis (RCM) and cross metathesis (CM) reactions. A pronounced influence on both catalyst activity and selectivity was found to be exerted by the NHC amino substituents, which emphasizes that a rigorously selected steric environment is critical in olefin metathesis catalyst design.     

Current and future sources of raw materials for the long‐chain omega‐3 fatty acid market

Much is being written in the popular and scientific press about the impending shortage of fish oil in its key markets. While most of the concerns are aimed at the aquaculture industry where fish oil and fishmeal are highly desired products, questions have also been raised from groups within the nutritional oils and nutraceutical industry. The concerns have been fueled by ominous predictions of impending doom because ocean fish are being pursued to extinction. While the questions related to aquaculture have and continue to receive responses (1, 2, 3), the issue of raw materials for the long‐chain ω‐3, nutritional oils or nutraceutical market has not been specifically addressed. This paper attempts to put the ω‐3 fish oil situation regarding the nutritional oils industry into perspective.     

Citation delay in interdisciplinary knowledge exchange

As part of a larger project to investigate knowledge flows between fields of science, westudied the differences in speed of knowledge transfer within and across disciplines. The agedistribution of references in three selections of articles was analysed, including almost 800.000references in journal publications of the United Kingdom in 1992, 700.000 references inpublications of Germany in 1992, and more than 11 million references in the world total ofpublications in 1998.The rate of citing documented knowledge from other disciplines appears to differ sharplyamong disciplines. For most of the disciplines the same ratio's are found in the three data sets.Exceptions show interesting differences in the interdisciplinary nature of a field in a country. Wefind a general tendency of a citation delay in case of knowledge transfer between different fieldsof science: citations to work of the own discipline show less of a time lag than citations to work ina foreign discipline. Between disciplines typical differences in the speed of incorporatingknowledge from other disciplines are observed, which appear to be relatively independent of timeand place: for each discipline the same pattern is found in the three data sets. The disciplinespecific characteristics found in the speed of interdisciplinary knowledge transfer may be point ofdeparture for further investigations. Results may contribute to explanations of differences incitation rates of interdisciplinary research.     

Silicone emulsions and surfactants

This review is intended to supply the practicing chemist with a working knowledge of the chemistry of silicone compounds. It has been divided into two parts, the first dealing with basic chemistry of silicones [O'Lenic, A.J., JSD 2, 229 (2000)] and the second with silicone-based surfactants, specifically dimethicone copolyols and their derivatives. This is the second part of the review. Although silicone compounds have been known for over 50 yr, the chemistry of these materials remains elusive to the average formulating chemist. This is indeed unfortunate, since the chemistry of the silicon atom and silicone compounds is every bit as wide in scope and rich in content as the chemistry of the carbon atom and the surfactant chemistry upon which it is based. This article will deal with the various methods of delivering silicone from aqueous systems. The two approaches are (i) to make emultions that contain silicone oil and a surfactant pair and the (ii) to make modify the molecule chemically to make the product more water-compatible. Both approaches find applications in a variety of industrial applications, with different challenges to the formulator.     

Theoretical and Experimental Insight into the Mechanism for Spontaneous Vertical Growth of ReS2 Nanosheets

Rhenium disulfide (ReS₂) differs fundamentally from other group‐VI transition metal dichalcogenides (TMDs) due to its low structural symmetry, which results in its optical and electrical anisotropy. Although vertical growth is observed in some TMDs under special growth conditions, vertical growth in ReS₂ is very different in that it is highly spontaneous and substrate‐independent. In this study, the mechanism that underpins the thermodynamically favorable vertical growth mode of ReS₂ is uncovered. It is found that the governing mechanism for ReS₂ growth involves two distinct stages. In the first stage, ReS₂ grows parallel to the growth substrate, consistent with conventional TMD growth. However, subsequent vertical growth is nucleated at points on the lattice where Re atoms are “pinched” together. At such sites, an additional Re atom binds with the cluster of pinched Re atoms, leaving an under‐coordinated S atom protruding out of the ReS₂ plane. This under‐coordinated S is “reactive” and binds to free Re and S atoms, initiating growth in a direction perpendicular to the ReS₂ surface. The utility of such vertical ReS₂ arrays in applications where high surface‐to‐volume ratio and electric‐field enhancement are essential, such as surface enhanced Raman spectroscopy, field emission, and solar‐based disinfection of bacteria, is demonstrated.     

A 3D Hybrid of Chemically Coupled Nickel Sulfide and Hollow Carbon Spheres for High Performance Lithium–Sulfur Batteries

Lithium–sulfur batteries are a promising next‐generation energy storage device owing to their high theoretical capacity and the low cost and abundance of sulfur. However, the low conductivity and loss of active sulfur material during operation greatly limit the rating capabilities and cycling stability of lithium–sulfur batteries. In this work, a unique sulfur host hybrid material comprising nanosized nickel sulfide (NiS) uniformly distributed on 3D carbon hollow spheres (C‐HS) is fabricated using an in situ thermal reduction and sulfidation method. In the hybrid material, the nanosized NiS provides a high adsorption capability for polysulfides and the C‐HS serves as a physical confinement for polysulfides and also a 3D electron transfer pathway. Moreover, NiS has strong chemical coupling with the C‐HS, favoring fast charge transfer and redox kinetics of the sulfur electrode. With a sulfur loading of up to 2.3 mg cm^?2, the hybrid material‐based lithium–sulfur batteries offer a capacity decay as low as 0.013% per cycle and a capacity of 695 mA h g^?1 at 0.5 C after 300 cycles. This unique 3D hybrid material with strong chemical coupling provides a promising sulfur host for high performance lithium–sulfur batteries.