Rate of Homogeneous Crystal Nucleation in molten NaCl

We report a numerical simulation of the rate of crystal nucleation of sodium chloride from its melt at moderate supercooling. In this regime nucleation is too slow to be studied with "brute-force" Molecular Dynamics simulations. The melting temperature of ("Tosi-Fumi") NaCl is $\sim 1060$K. We studied crystal nucleation at $T$=800K and 825K. We observe that the critical nucleus formed during the nucleation process has the crystal structure of bulk NaCl. Interestingly, the critical nucleus is clearly faceted: the nuclei have a cubical shape. We have computed the crystal-nucleation rate using two completely different approaches, one based on an estimate of the rate of diffusive crossing of the nucleation barrier, the other based on the Forward Flux Sampling and Transition Interface Sampling (FFS-TIS) methods. We find that the two methods yield the same result to within an order of magnitude. However, when we compare the extrapolated simulation data with the only available experimental results for NaCl nucleation, we observe a discrepancy of nearly 5 orders of magnitude. We discuss the possible causes for this discrepancy

Non-equilibrium dynamics of an active colloidal "chucker"

We report Monte Carlo simulations of the dynamics of a "chucker": a colloidal particle which emits smaller solute particles from its surface, isotropically and at a constant rate k_c. We find that the diffusion constant of the chucker increases for small k_c, as recently predicted theoretically. At large k_c the chucker diffuses more slowly due to crowding effects. We compare our simulation results to those of a "point particle" Langevin dynamics scheme in which the solute concentration field is calculated analytically, and in which hydrodynamic effects can be included albeit in an approximate way. By simulating the dragging of a chucker, we obtain an estimate of its apparent mobility coefficient which violates the fluctuation-dissipation theorem. We also characterise the probability density profile for a chucker which sediments onto a surface which either repels or absorbs the solute particles, and find that the steady state distributions are very different in the two cases. Our simulations are inspired by the biological example of exopolysaccharide-producing bacteria, as well as by recent experimental, simulation and theoretical work on phoretic colloidal "swimmers".Comment: re-submission after referee's comment

Explicit and tacit knowledge in construction of passive housing, knowledge models in Lithuania / Išreikštinės ir neišreikštinės žinios pasyviųjų namų statyboje, žinių modeliai pasaulyje ir Lietuvoje

Optimization of building maintenance expenditure becomes really an urgent issue in Lithuania. People prefer a warmer housing and show interest in recent decisions of engineering systems. They are looking for the best decision of heating costs optimization to price down heating costs not 10-20%, but a number of times. The results of passive houses scientific research as well as models of passive housing are discussed in the article. They ascertain and compare features of passive housing construction in different countries which depends on climatic conditions. Most countries support traditional housing. Remarkable thermal resistance and cost efficient maintenance of passive housing may be reached through an integrated approach of using proper architectural, constructional and engineering resolution, as well as applying the most relevant material usage and elaborating and accumulating practical knowledge. Lithuania, as well as other countries in the world, reveals that the concept of tacit knowledge still lacks sufficient attention within the construction industry, despite the fact that proper understanding and management of this resource is of immense importance for the achievement of better organizational performance. As the initial step towards the management of tacit knowledge, this paper examines the factors affecting tacit knowledge generation and utilization in the construction industry. Santrauka Lietuvoje ypač aktualus tampa pastato eksploatacinių išlaidų optimizavimas. Žmonės renkasi šiltesnį būstą, domisi naujausiais inžinerinių sistemų sprendimais. Išlaidų šildymui sumažinti ne 10–20 %, bet bent kelis kartus, ieškomas geriausias šildymo išlaidų optimizavimo būdas. Straipsnyje aptarti pasaulyje atlikti pasyvaus būsto moksliniai tyrimai, bei pasyvaus namo modeliai. Išaiškinti ir palyginti įvairių šalių pasyvių namų statybos ypatumai, priklausomai nuo klimato sąlygų. Daugelyje šalių yra palaikomos ankstesnės statybų tradicijos. Puikių pasyviojo namo šiluminės varžos ir ekonomiškumo rezultatų galima pasiekti kompleksiškai taikant optimalius architektūrinius, statybinius ir inžinerinius sprendimus, siekti geresnių medžiagų panaudojimo, tobulinti ir kaupti praktikos įgūdžius statyboje. Jei rinkos sąlygos leidžia, turimas žinias reikia struktūrinti. Pastebima, kad Lietuvoje ir pasaulyje statybos pramonės viduje išreikštinių ir neišreikštinių žinių sąvokos vis dar stokoja pakankamo dėmesio, neatsižvelgiant į tai, kad tinkamas supratimas ir turimų išteklių vadyba turi didžiulę reikšmę siekiant geresnių tendencijų projektavime, o taip pat neišreikštų žinių generavime ir panaudojime statyboje. Raktiniai žodžiai: pasyvusis būstas, išreikštinės žinios, neišreikštinės žinios, energijos taupyma

Augmenting Group Performance in Target-Face Recognition via Collaborative Brain-Computer Interfaces for Surveillance Applications

This paper presents a hybrid collaborative brain- computer interface (cBCI) to improve group-based recognition of target faces in crowded scenes recorded from surveillance cameras. The cBCI uses a combination of neural features extracted from EEG and response times to estimate the decision confidence of the users. Group decisions are then obtained by weighing individual responses according to these confidence estimates. Results obtained with 10 participants indicate that the proposed cBCI improves decision errors by up to 7% over traditional group decisions based on majority. Moreover, the confidence estimates obtained by the cBCI are more accurate and robust than the confidence reported by the participants after each decision. These results show that cBCIs can be an effective means of human augmentation in realistic scenarios

CES-530: Collaborative Brain-Computer Interface for Aiding Decision-making

We look at the possibility of integrating the percepts from multiple non-communicating observers as a means of achieving better joint perception and better group decisions. Our approach involves the combination of a brain-computer interface with human behavioural responses. To test ideas in controlled conditions, we asked observers to perform a simple matching task involving the rapid sequential presentation of pairs of visual patterns and the subsequent decision as whether the two patterns in a pair were the same or different. We recorded the response times of observers as well as a neural feature which predicts incorrect decisions and, thus, indirectly indicates the confidence of the decisions made by the observers. We then built a composite neuro-behavioural feature which optimally combines the two measures. For group decisions, we uses a majority rule and three rules which weigh the decisions of each observer based on response times and our neural and neuro-behavioural features. Results indicate that the integration of behavioural responses and neural features can significantly improve accuracy when compared with the majority rule. An analysis of event-related potentials indicates that substantial differences are present in the proximity of the response for correct and incorrect trials, further corroborating the idea of using hybrids of brain-computer interfaces and traditional strategies for improving decision making