Attachment of composite porous supra-particles to air–water and oil–water interfaces: theory and experiment

We developed and tested a theoretical model for the attachment of fluid-infused porous supra-particles to a fluid–liquid interface. We considered the wetting behaviour of agglomerated clusters of particles, typical of powdered materials dispersed in a liquid, as well as of the adsorption of liquid-infused colloidosomes at the liquid–fluid interface. The free energy of attachment of a composite spherical porous supra-particle made from much smaller aggregated spherical particles to the oil–water interface was calculated. Two cases were considered: (i) a water-filled porous supra-particle adsorbed at the oil–water interface from the water phase, and, (ii) an oil-filled porous supra-particle adsorbed at the oil–water interface from the oil-phase. We derived equations relating the three-phase contact angle of the smaller “building block” particles and the contact angle of the liquid-infused porous supra-particles. The theory predicts that the porous supra-particle contact angle attached at the liquid interface strongly depends on the type of fluid infused in the particle pores and the fluid phase from which it approaches the liquid interface. We tested the theory by using millimetre-sized porous supra-particles fabricated by evaporation of droplets of polystyrene latex suspension on a pre-heated super-hydrophobic surface, followed by thermal annealing at the glass transition temperature. Such porous particles were initially infused with water or oil and approached to the oil–water interface from the infusing phase. The experiment showed that when attaching at the hexadecane–water interface, the porous supra-particles behaved as hydrophilic when they were pre-filled with water and hydrophobic when they were pre-filled with hexadecane. The results agree with the theoretically predicted contact angles for the porous composite supra-particles based on the values of the contact angles of their building block latex particles measured with the Gel Trapping Technique. The experimental data for the attachment of porous supra particles to the air–water interface from both air and water also agree with the theoretical model. This study gives important insights about how porous particles and particle aggregates attach to the oil–water interface in Pickering emulsions and the air–water surface in particle-stabilised aqueous foams relevant in ore flotation and a range of cosmetic, pharmaceutical, food, home and personal care formulations

Preparation and attachment of liquid-infused porous supra-particles to liquid interfaces

© 2016 The Royal Society of Chemistry. We prepared model porous composite supra-particles and investigated the effect of the initial infused fluid phase on their attachment at the liquid-fluid interface. We used a simple method for fabrication of millimetre-sized spherical porous supra-particles from much smaller monodisperse latex microparticles as building blocks by evaporation of a polystyrene sulphate latex suspension on a hot super-hydrophobic surface. We annealed the dried supra-particles at the polymer's glass transition temperature to fuse partially their latex particle building blocks. Spherical porous supra-particles were produced above 40 wt% initial concentration of the latex particles in the suspension, which had a rough surface, with a porous and amorphous structure. We controlled the supra-particle size by varying the initial volume of the latex suspension drop, the latex particle concentration and the drop evaporation temperature. This preparation technique allowed limited control over the porosity of the supra-particles by varying the initial concentration of the latex particle suspension, the rate of evaporation and the annealing temperature. We characterised the surface morphology and the inner structure of supra-particles by SEM imaging. We report for the first time results of an MRI study of supra-particles attached to an air-water or an oil-water interface, which indicated that only the surface layer of the building block particles attaches to the liquid interface while the pore fluid was not displaced by the outer fluid. We observed that supra-particles infused with water had different wettability and attachment positions at the oil-water interface compared with the same particles infused with oil. Similarly, the infusion of the porous supra-particles with water led to a different attachment at the air-water interface compared to the attachment of the same supra-particle when dry. The fundamental importance of this result is that the porous particles (or colloid particle agglomerates) may give an oil-in-water or water-in-oil Pickering emulsion depending on whether they are initially impregnated with oil or water. The results of this study are relevant for particle-stabilised emulsions and foams in a range of pharmaceutical, food and cosmetic formulations as well as ore flotation

Adsorption of carboxylic modified latex particles at liquid interfaces studied by the gel trapping technique

We have studied how carboxylic modified latex (CML) microparticles adsorb at liquid surfaces and the preferred type of emulsion they can stabilise depending on the particle size and the surface density of carboxylic groups. We measured the particle contact angle by using the gel trapping technique (GTT) for CML particles adsorbed at air–water and oil–water interfaces. Using this method we obtained scanning electron microscopy (SEM) micrographs of polydimethylsiloxane (PDMS) replicas of the liquid interface with the particles, where the PDMS replicates the non-polar phase and measured the particle contact angle. We discovered that the particle wettability correlates well with the surface density of the carboxylic groups but is not very sensitive to the presence of electrolyte in the aqueous phase and the value of the particle zeta potential. We demonstrated that CML microparticles with a high surface density of COOH groups stabilise oil-in-water (O/W) emulsions while those with the lowest coverage of COOH groups favour the formation of water-in-oil (W/O) emulsions. We found that this corresponds to a change of the CML particle contact angle from lower than 90° to higher than 90° upon decrease of the surface density of COOH groups. The findings confirm that the surface density of polar groups has a much bigger effect on the particle wettability and the preferred emulsion than the particle surface charge and zeta potential. Our results on the type of stabilised Pickering emulsion agree with other experimental studies with different particle materials. We propose an alternative explanation for the link between the particle contact angle and the type of stabilised Pickering emulsion

TimeTrader: Exploiting Latency Tail to Save Datacenter Energy for On-line Data-Intensive Applications

Datacenters running on-line, data-intensive applications (OLDIs) consume significant amounts of energy. However, reducing their energy is challenging due to their tight response time requirements. A key aspect of OLDIs is that each user query goes to all or many of the nodes in the cluster, so that the overall time budget is dictated by the tail of the replies' latency distribution; replies see latency variations both in the network and compute. Previous work proposes to achieve load-proportional energy by slowing down the computation at lower datacenter loads based directly on response times (i.e., at lower loads, the proposal exploits the average slack in the time budget provisioned for the peak load). In contrast, we propose TimeTrader to reduce energy by exploiting the latency slack in the sub- critical replies which arrive before the deadline (e.g., 80% of replies are 3-4x faster than the tail). This slack is present at all loads and subsumes the previous work's load-related slack. While the previous work shifts the leaves' response time distribution to consume the slack at lower loads, TimeTrader reshapes the distribution at all loads by slowing down individual sub-critical nodes without increasing missed deadlines. TimeTrader exploits slack in both the network and compute budgets. Further, TimeTrader leverages Earliest Deadline First scheduling to largely decouple critical requests from the queuing delays of sub- critical requests which can then be slowed down without hurting critical requests. A combination of real-system measurements and at-scale simulations shows that without adding to missed deadlines, TimeTrader saves 15-19% and 41-49% energy at 90% and 30% loading, respectively, in a datacenter with 512 nodes, whereas previous work saves 0% and 31-37%.Comment: 13 page

Assessment of Daylight in Relation to the Agitation Levels of People with Dementia

This research aims to develop the design guidelines for designing daylight levels that may positively impact on reducing agitation behaviour in people with dementia based on principles of behavioural and psychological symptoms. The research methodology was based on the literature review, fieldwork and building performance simulation (BPS). Quantitative and qualitative approach was conducted by assessing indoor daylight quality and agitation levels. In addition, evaluation of daylight parameters (i.e. daylight factor and relation to the agitation level) was also carried out during the observation. The results suggest that agitation level is indeed higher in the top floor of the nursing house, mostly in the most occupied areas such as: communal area and dining room. According to the carers, the main reason to such phenomenon might be due to the sundown syndrome that usually happens after tea time. Moreover, the daylight strategies were carried out to increase the effectiveness of daylight illuminance levels for indoor environment

Review on Gaps and Challenges in Prediction Outdoor Thermal Comfort Indices: Leveraging Industry 4.0 and ‘Knowledge Translation’

The current outdoor thermal comfort index assessment is either based on thermal sensation votes collected through field surveys/questionnaires or using equations fundamentally backed by thermodynamics, such as the widely used UTCI and PET indices. The predictive ability of all methods suffers from discrepancies as multi-sensory attributes, cultural, emotional, and psychological cognition factors are ignored. These factors are proven to influence the thermal sensation and duration people spend outdoors, and are equally prominent factors as air temperature, solar radiation, and relative humidity. The studies that adopted machine learning models, such as Artificial Neural Networks (ANNs), concentrated on improving the predictive capability of PET, thereby making the field of Artificial Intelligence (AI) domain underexplored. Furthermore, universally adopted outdoor thermal comfort indices under-predict a neutral thermal range, for a reason that is linked to the fact that all indices were validated on European/American subjects living in temperate, cold regions. The review highlighted gaps and challenges in outdoor thermal comfort prediction accuracy by comparing traditional methods and Industry 4.0. Additionally, a further recommendation to improve prediction accuracy by exploiting Industry 4.0 (machine learning, artificial reality, brain–computer interface, geo-spatial digital twin) is examined through Knowledge Translatio

The Impact of Occupancy Energy Use Behaviour of High-Rise Dwellings In Southeast China

\ua9 2021 CUE. Reducing building energy use and the associated greenhouse gas emissions is becoming increasingly important. Since occupants’ behaviour has significant impacts on building energy performance and occupant comfort, and it varies with an individual’s age, sex, background, and other personal factors, it is important to understand the critical links between people’s lifestyles and energy consumption. Most studies of the relationship between occupancy behaviour and energy consumption focus on public buildings like office buildings and commercial buildings. Research for dwellings is limited since the information is difficult to collect, and detailed knowledge of individual homes is needed. This paper conducted a detailed survey to gain information on thermal satisfaction levels, occupancy equipment ownership and their using patterns of 112 urban households who lived in a typical booming city in southeast China. Based on the collected data, an energy simulation software program was used to investigate the main factors of occupancy behaviour, which affect energy consumption. The results lead to the internal gains profiles and window-opening profiles, which reflect the lifestyle in the target area who lived in an urban highrise building. The simulation of typical households indicated that occupancy behaviour only occupied a small scale compared to equipment but still significant to improve

Translated Poisson approximation to equilibrium distributions of Markov population processes

The paper is concerned with the equilibrium distributions of continuous-time density dependent Markov processes on the integers. These distributions are known typically to be approximately normal, and the approximation error, as measured in Kolmogorov distance, is of the smallest order that is compatible with their having integer support. Here, an approximation in the much stronger total variation norm is established, without any loss in the asymptotic order of accuracy; the approximating distribution is a translated Poisson distribution having the same variance and (almost) the same mean. Our arguments are based on the Stein-Chen method and Dynkin's formula.Comment: 18 page

L'Inventaire forestier national, outil d'évaluation et de suivi de la gestion forestière.

La notion de "gestion forestière durable" a conduit à l'élaboration d'"indicateurs" quantitatifs et qualitatifs, destinés à évaluer la gestion forestière actuelle et son évolution passée. Trois catégories de données sont disponibles à l'IFN : les données cartographiques, les données dendrométriques et les données écologiques et floristiques. Les données cartographiques permettent une analyse du territoire forestier utile dans différents domaines : récréation, DFCI et faune sauvage notamment. Les indicateurs de production de bois et certains indicateurs de biodiversité peuvent être appréciés à l'aide des données dendrométriques. Quant aux données éco-floristiques, elles devraient à terme permettre une évaluation de l'importance des différentes stations et habitats et de l'adéquation essence/station forestière dans la région

Etat et évolution de la ressource en forêt méditerranéenne, les chiffres de l'Inventaire forestier national

En 1982, Bernard Thibaut avait rassemblé les données de base de la connaissance des forêts méditerranéennes. Nabila Hamza, de l'Inventaire forestier national, montre l'évolution des surfaces et des peuplements depuis lors