Impact of Brownian motion on the particle settling in molten metals

Understanding the settling behavior of nanoparticles in molten metals/alloys is important as it will aid in achieving uniform dispersions of reinforcement particles in metal matrix nanocomposites. Uniform dispersions are necessary to activate the Orowan strengthening mechanism, which can increase yield strength without significant diminishment of ductility. In this work, an analytical model of particle size effects on settling is described that takes into account both deterministic Stokes’ law and stochastic Brownian motion. The model shows a clear transitional behavior where settling velocity follows Stokes’ law for large particles and then drops to zero for small particles implying that Brownian motion predominates. It indicated that, in the Brownian motion regime, where the discrete nature of the liquid must be considered, the random motion imparted by unbalanced collisions can overwhelm the motions normally imposed by forces such as gravity, viscous drag, and thermal/concentration gradients.     

A Multiplexed Four Channel On-Line Iodine Monitor

Abstract

A robust autonomous system is described for the spectrophotometric determination of aqueous elemental iodine in multiple flowing process streams. The quantitative methodology uses characteristic absorbance at 460 nm, corrected for baseline drift using absorbance at 600 nm. Linear dynamic ranges of 0.2 - 25 mg/L, 0.4 - 45 mg/L, and 2 - 250 mg/L have been attained using path lengths of 1 cm, 5 cm, and 10 cm respectively. The multiplexed iodine monitor has proven capable of continuous operation for periods of up to eighteen months.     

Multilevel surrogate modeling of an amine scrubbing process for CO2capture

Surrogate models provide a powerful method for simplifying calculations within complex simulations. While surrogate models are broadly applied within chemical engineering, little research exists investigating the level of surrogacy's impact on a simplified process model. In this work, artificial neural networks (ANN) and Kriging models are used as surrogate models at the process, process unit, and thermodynamic levels for a CO₂ amine scrubbing process. The surrogated models are evaluated against an Aspen Plus simulation for accuracy, convergence behavior, computational cost, and ability to extrapolate. The thermodynamic and process unit models can better handle discontinuous, non-smooth behavior, and convergence issues in the surrogated truth model, but poor conditioning in the final system of equations results in a lower accuracy and convergence rate than the process level surrogate. Beyond model accuracy, availability of diverse data, intended re-usability, and the desired outputs must be considered when selecting a level of abstraction.     

Hydrodesulfurization of Diesel Feeds by Association of a Catalytic Process and a Separation Process Using Charge-Transfer Complexes

While deep hydrodesulfurization of gas oil is more and more important, elimination of sulfur compounds such as 4,6-dialkyldibenzothio-phenes still attracts considerable attention. A new process based on the association of a separation process by charge-transfer complex (CTC) formation and classical catalytic hydrotreating (HDT) was evaluated. The results indicated that a CTC pretreatment allows the rate of hydrodesulfurization (HDS) to increase and the final sulfur level to decrease. This process is even more efficient for feeds difficult to desulfurize.     

Dietary Fatty‐Acid Compositions Are more Strongly Reflected in Fatty than Lean Dorsal Fillets of Common Carp (Cyprinus carpio L.)

In this fish‐feeding study, we tested similarity patterns between fatty acids (FA) in diets and common carp (Cyprinus carpio) of fish ponds used for semi‐intensive aquaculture, containing naturally occurring pond zooplankton and different feeds (marine or terrestrial feeds) until carp reached market size. We evaluated if and how total lipid contents in dorsal fillets can reflect dietary FA compositions in farm‐raised common carp and hypothesized that increasing total lipid contents in dorsal fillets significantly increase the similarity between dietary and dorsal fillets’ FA compositions. Results of this study showed that carps had higher total lipids when supplied with marine feeds and dietary FA compositions were indeed more strongly reflected in fatty (i.e. high total lipid contents) than in leaner dorsal fillets (low total lipid contents). Increasing total lipid contents in dorsal fillets significantly increased the similarity between the dietary and dorsal fillets’ FA compositions. In contrast, leaner dorsal fillets had FA patterns that were more distinct from dietary FA. Total lipid contents higher than ~60 mg/g dry weight in dorsal fillets had only limited effects on increasing the similarity between FA compositions of diets and dorsal fillets, and were independent of feed sources. It is thus suggested that higher total lipid contents in dorsal fillets can be used as a proxy to predict dietary FA profiles in common carps, or perhaps even in farm‐raised fish in general.     

Traders, Drivers and the National Health Insurance Scheme in Small Town Ghana

Based on anthropological fieldwork in the central market and taxi station of Koforidua, Ghana, this paper aims to improve our understanding of the social dynamics in the informal economy of a Ghanaian small town in relation to state policies. It strives to describe the way processes of formalization and informalization may coexist and interact during the implementation of the recent National Health Insurance Scheme (NHIS) . The ethnographic approach helps us to better understand how attitudes on NHIS are formed and the way information and values are disseminated. Closely examining the social infrastructure of this setting contributes further to this understanding. In the marketplace, it is important to develop networks of personal relations with fellow traders, customers, and suppliers. At the taxi station, on the other hand, the most important strategy is to join the powerful local union. These strategies are ways for actors to gain security and protection against economic vulnerability in a competitive liberalized economy. In this regard, the NHIS has also provided opportunities for actors. While the NHIS is a way for the state to increase control over the informal economy, and gradually formalizing it, it simultaneously indirectly reinforces and confirms the existing informal strategies of networking.     

Biomass gasification cogeneration – A review of state of the art technology and near future perspectives

Biomass is a renewable resource from which a broad variety of commodities can be produced. However, the resource is scarce and must be used with care to avoid depleting future stock possibilities. Flexibility and efficiency in production are key characteristics for biomass conversion technologies in future energy systems. Thermal gasification of biomass is proved throughout this article to be both highly flexible and efficient if used optimally. Cogeneration processes with production of heat-and-power, heat-power-and-fuel or heat-power-and-fertilizer are described and compared. The following gasification platforms are included in the assessment: The Harboøre up draft gasifier with gas engine, the Güssing FICFB gasifier with gas engine or PDU, the LT-CFB gasifier with steam cycle and nutrient recycling and finally the TwoStage down draft gasifier with gas engine, micro gas turbine (MGT), SOFC, SOFC/MGT or catalytic fuel synthesis.     

Rotary actuators with multipole ring magnets

Rotary actuators are electromagnetic devices developing mechanical torque with limited rotary motion. Because of their simplicity and low cost they are finding more and more applications, especially in the automotive field. This paper describes a novel homopolar rotary actuator with a ring-type radially magnetized multipolar permanent magnet featuring a high force density “transverse flux” configuration which performs a spring action by developing electromagnetic torques with limited angular movement. Because of the magnetically complicated and nonsymmetrical rotary actuator configuration, the analysis of this actuator is based on 3-D finite element software. The analysis, which is well supported by test results, shows that symmetrical magnetic forces in both directions of rotation were achieved with a stable equilibrium position, satisfying all design requirements to enhance the basic hydraulic power steering system of passenger vehicles     

New dendrimer-peptide host-guest complexes: towards dendrimers as peptide carriers

Adamantyl urea and adamantyl thiourea modified poly(propylene imine) dendrimers act as hosts for N-terminal tert-butoxycarbonyl (Boc)-protected peptides and form chloroform-soluble complexes. Investigations with NMR spectroscopy show that the peptide is bound to the dendrimer by ionic interactions between the dendrimer outer shell tertiary amines and the C-terminal carboxylic acid of the peptide, and also through host-urea to peptide-amide hydrogen bonding. The hydrogen-bonding nature of the peptide-dendrimer interactions was further confirmed by using Fourier transform IR spectroscopy, for which the NH- and CO-stretch signals of the peptide amide moieties shift towards lower wavenumbers upon complexation with the dendrimer. Spatial analysis of the complexes with NOESY spectroscopy generally shows close proximity of the N-terminal Boc group of the peptide to the peripheral adamantyl groups on the dendrimer host. The influence of side-chain motif on interactions with the host is analyzed by using seven different N-Boc-protected tripeptides as guests for the dendrimer. Downfield shifts of up to 1.3 ppm were observed for the guest amide NH-proton signals. These shifts decreased with increasing 'bulkiness' of the amino acid side chains. Despite this, the dendrimer was capable of making multiple peptide-dendrimer complexes when presented with a library of seven peptides. The different peptides were all present in the host, which did not show specific preferences, and could be released under mild acidic conditions. These results show the general nature of the peptide-dendrimer interactions in the formation of either single- or multiple-peptide-dendrimer complexes.     

The UCSC Kestrel parallel processor

The architectural landscape of high-performance computing stretches from superscalar uniprocessor to explicitly parallel systems, to dedicated hardware implementations of algorithms. Single-purpose hardware can achieve the highest performance and uniprocessors can be the most programmable. Between these extremes, programmable and reconfigurable architectures provide a wide range of choice in flexibility, programmability, computational density, and performance. The UCSC Kestrel parallel processor strives to attain single-purpose performance while maintaining user programmability. Kestrel is a single-instruction stream, multiple-data stream (SIMD) parallel processor with a 512-element linear array of 8-bit processing elements. The system design focuses on efficient high-throughput DNA and protein sequence analysis, but its programmability enables high performance on computational chemistry, image processing, machine learning, and other applications. The Kestrel system has had unexpected longevity in its utility due to a careful design and analysis process. Experience with the system leads to the conclusion that programmable SIMD architectures can excel in both programmability and performance. This work presents the architecture, implementation, applications, and observations of the Kestrel project at the University of California at Santa Cruz.