Parametric models of local search progression

Algorithms that search for good solutions to optimization problems present a trace of current best objective values over time. We describe an empirical study of parametric models of this progression that are both interesting as ways to characterize the search progression compactly and useful as means of predicting search behavior. In our computational experiments, we give examples of a variety of problems and algorithms where we are able to use the parametric models to make predictions of performance that cross instances and instance sizes.     

Influence of the nanofiber dimensions on the properties of nanocellulose/poly(vinyl alcohol) aerogels

The investigation of aerogels made from cellulose nanofibers and poly(vinyl alcohol) (PVOH) as a polymeric binder is reported. Aerogels based on different nanocellulose types were studied to investigate the influence of the nanocellulose dimensions and their rigidity on the morphology and mechanical properties of the resulting aerogels. Thus, cellulose nanocrystals (CNCs) with low (10), medium (25), and high (80) aspect ratios, isolated from cotton, banana plants, and tunicates, respectively, microfibrillated cellulose (MFC) and microcrystalline cellulose (MCC) were dispersed in aqueous PVOH solutions and aerogels were prepared by freeze‐drying. In addition to the cellulose type, the PVOH‐ and the CNC‐concentration as well as the freeze‐drying conditions were varied, and the materials were optionally cross‐linked by an annealing step or the use of a chemical cross‐linker. The data reveal that at low PVOH content, rigid, high‐aspect ratio CNCs isolated from tunicates afford aerogels that show the least amount of shrinking upon freeze‐drying and display the best mechanical properties. However, with increasing concentration of PVOH or upon introduction of a chemical cross‐linker the differences between materials made from different nanocellulose types decrease. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41740.     

Simulation study of the effect of wall roughness on the dynamics of granular flows in rotating semicylindrical chutes

A discrete element model (DEM) is used to investigate the behavior of spherical particles flowing down a semicylindrical rotating chute. The DEM simulations are validated by comparing with particle tracking velocimetry results of spherical glass particles flowing through a smooth semicylindrical chute at different rotation rates of the chute. The DEM model predictions agree well with experimental results of surface velocity and particle bed height evolution. The validated DEM model is used to investigate the influence of chute roughness on the flow behavior of monodisperse granular particles in rotating chutes. To emulate different base roughnesses, a rough base is constructed out of a square close packing of fixed spherical particles with a diameter equal to, smaller, or larger than the flowing particles. Finally, the DEM model is used to study segregation in a binary density mixture for different degrees of roughness of the chute. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2117–2135, 2015     

Melt processing of polyamide 12 and cellulose nanocrystals nanocomposites

The fabrication of nanocomposites of polyamide 12 (PA12) and cellulose nanocrystals (CNCs) isolated from cotton and tunicates is reported. Through a comparative study that involved solution‐cast (SC) and melt‐processed materials, it was shown that PA12/CNC nanocomposites can be prepared in a process that appears to be readily scalable to an industrial level. The results demonstrate that CNCs isolated from the biomass by phosphoric acid hydrolysis display both a sufficiently high thermal stability to permit melt processing with PA12, and a high compatibility with this polymer to allow the formation of nanocomposites in which the CNCs are well dispersed. Thus, PA12/CNC nanocomposites prepared by melt‐mixing the two components in a co‐rotating roller blade mixer and subsequent compression molding display mechanical properties that are comparable to those of SC reference materials. Young's modulus and maximum stress could be doubled in comparison to the neat PA12 by introduction of 10% (CNCs from tunicates) or 15% w/w (CNCs from cotton) CNCs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42752.     

A Comparison of Leisure Time Spent in a Garden with Leisure Time Spent Indoors: On Measures of Restoration in Residents in Geriatric Care

During the past 20 years, findings have indicated that nature plays an active role in helping people recover from stress and fatigue. Two of the most cited theories in this field are Rachel and Stephen Kaplan's theory of recovery from Directed Attention Fatigue in nature and Roger Ulrich's theory of aesthetic and affective responses to natural environments and stress recovery. One aim of the present study is to test whether being outdoors in a green recreational environment causes people to be more focused, compared to being in a room indoors (in line with hypotheses suggested by the Kaplans). Another aim is to test whether people experience stress reduction, i.e. as evidenced by changes in blood pressure and heart rate, if they are placed in an environment with many green elements (in line with hypotheses suggested by Ulrich). The overall study design is that of an intervention study. Fifteen elderly persons living at a home for very elderly people participated. Their powers of concentration, blood pressure and heart rate were measured before and after an hour of rest in a garden or in an indoor setting. Seven elderly people were randomly chosen to have their first series of tests in a garden, while eight elderly people had their first series of tests indoors. The results indicate that powers of concentration increase for very elderly people after a visit to a garden outside the geriatric home in which they live, compared to that after resting indoors in their favourite room. The results did not show any effects on blood pressure or heart rate. It is suggested that having a one-hour rest outdoors in a garden setting plays a role in elderly people's powers of concentration, and could thereby affect their performance of activities of daily living. One important factor in this study was that both the outdoor environment and the indoor environment at the home were highly valued by participants.     

Planning Belgian Congo’s network of medical infrastructure: type-plans as tools to construct a medical model-colony, 1949–1959

ABSTRACT

Throughout the 1950s, the Belgian colonial government constructed a vast network of hospital infrastructure as part of its Ten-Year Plan, a colony-wide socio-economic scheme emblematic for the era of ‘welfare colonialism.’ This network played a key role in Belgian colonialism, by providing healthcare, but also by boosting labour productivity, facilitating state presence and control, and by advertising Congo as a medical model-colony. In this article, we unpack the extensive administrative apparatus that was necessary to buttress this ambitious building programme, and we highlight type-plans as crucial government tools to construct such a vast network of healthcare infrastructure. At first glance, the use of type-plans confirms classic characterizations of the Belgian colonial government as an omnipotent and technocratic state apparatus that implemented large, top-down government plans through authoritative methods, often discarding local realities. However, tracing hospital construction on the ground reveals that type-plans did not function as immutable models, but rather as modular blueprints that allowed local administrations to adapt hospitals to local needs and contingencies. As such, our article illustrates how, facilitated by surprisingly flexible type-plans, everyday colonial policymaking in Belgian Congo was, contrary to the still dominant discourse, deeply reliant on the agency and aptitude of local officials.     

Gallium gradients in Cu(In,Ga)Se2 thin‐film solar cells

The gallium gradient in Cu(In,Ga)Se₂ (CIGS) layers, which forms during the two industrially relevant deposition routes, the sequential and co‐evaporation processes, plays a key role in the device performance of CIGS thin‐film modules. In this contribution, we present a comprehensive study on the formation, nature, and consequences of gallium gradients in CIGS solar cells. The formation of gallium gradients is analyzed in real time during a rapid selenization process by in situ X‐ray measurements. In addition, the gallium grading of a CIGS layer grown with an in‐line co‐evaporation process is analyzed by means of depth profiling with mass spectrometry. This gallium gradient of a real solar cell served as input data for device simulations. Depth‐dependent occurrence of lateral inhomogeneities on the µm scale in CIGS deposited by the co‐evaporation process was investigated by highly spatially resolved luminescence measurements on etched CIGS samples, which revealed a dependence of the optical bandgap, the quasi‐Fermi level splitting, transition levels, and the vertical gallium gradient. Transmission electron microscopy analyses of CIGS cross‐sections point to a difference in gallium content in the near surface region of neighboring grains. Migration barriers for a copper‐vacancy‐mediated indium and gallium diffusion in CuInSe₂ and CuGaSe₂ were calculated using density functional theory. The migration barrier for the In_Cu antisite in CuGaSe₂ is significantly lower compared with the Ga_Cu antisite in CuInSe₂, which is in accordance with the experimentally observed Ga gradients in CIGS layers grown by co‐evaporation and selenization processes. Copyright © 2014 John Wiley & Sons, Ltd.     

A Nanochannel Platform for Single DNA Studies: From Crowding,Protein DNA Interaction,to Sequencing of Genomic Information

The study of nanochannel-confined DNA is important from biotechnological and biophysical points of view. We produce nanochannels in elastomer with soft lithography and proton beam writing. Issues concerning DNA confined in such quasi one-dimensional channels are discussed. We describe DNA stretching via the control of channel diameter and buffer conditions and how the extension can be interpreted with theory and computer simulation. We then discuss the conformation of nano-confined DNA crowded by neutral polymers and like-charged proteins. As an example of a protein that has an affinity to DNA, the effect of heat-stable nucleoid-structuring protein, H-NS, on the folding and compaction of DNA is reviewed. Compaction of DNA by eukaryotic protamine and unpacking of pre-compacted DNA through an increase in salt concentration are discussed. We review results obtained with a novel, cross-channel device that allows the monitoring of the dynamic, conformational response of DNA after exposure to a ligand or protein and/or a change in buffer conditions in situ. As a biotechnological application, linearization of DNA by bottlebrush coating with a polypeptide copolymer is discussed. It is demonstrated that large-scale genomic organization can be sequenced using single DNA molecules on an array of elastomeric nanochannels. Overall, our results show that the effects of ligands and proteins on the conformation, folding, and condensation of DNA are not only related to classical controlling factors, such as osmotic pressure, charge, and binding, but that the interplay with confinement in a nanospace is of paramount importance.     

Influence of Ignition Sources on Heat Release Rate in the Furniture Calorimeter

When measuring the production rates of heat and smoke of upholstered furniture the ignition source must not influence the test results. In this paper variations in the strength, application time and geometry of the ignition burner used in the furniture calorimeter are studied. Results from replicate furniture calorimeter chair test show that the burning behaviour is almost independent of the burner intensity in the applied regime. Tests on six different furniture items were performed in the furniture calorimeter. The test objects were exposed to three intensity levels of ignition source. The sources were: a large propane burner giving 30 kW during 120 s and a smaller propane burner used at two levels of heat output, 1.7 and 5.8 kW during 90 s. The results showed that the burning behaviour of the furniture was very similar regardless of which burner was used. This was especially evident when the time regime between 50 and 400 kW was studied. The length of this period is a measurement on how quick untenable conditions are developing in a single, well-ventilated compartment.