Pattern formation during the evaporation of a colloidal nanoliter drop: a numerical and experimental study

An efficient way to precisely pattern particles on solid surfaces is to dispense and evaporate colloidal drops, as for bioassays. The dried deposits often exhibit complex structures exemplified by the coffee ring pattern, where most particles have accumulated at the periphery of the deposit. In this work, the formation of deposits during the drying of nanoliter colloidal drops on a flat substrate is investigated numerically and experimentally. A finite-element numerical model is developed that solves the Navier-Stokes, heat and mass transport equations in a Lagrangian framework. The diffusion of vapor in the atmosphere is solved numerically, providing an exact boundary condition for the evaporative flux at the droplet-air interface. Laplace stresses and thermal Marangoni stresses are accounted for. The particle concentration is tracked by solving a continuum advection-diffusion equation. Wetting line motion and the interaction of the free surface of the drop with the growing deposit are modeled based on criteria on wetting angles. Numerical results for evaporation times and flow field are in very good agreement with published experimental and theoretical results. We also performed transient visualization experiments of water and isopropanol drops loaded with polystyrene microsphere evaporating on respectively glass and polydimethylsiloxane substrates. Measured evaporation times, deposit shape and sizes, and flow fields are in very good agreement with the numerical results. Different flow patterns caused by the competition of Marangoni loops and radial flow are shown to determine the deposit shape to be either a ring-like pattern or a homogeneous bump

IMECE2002-33859 MANUFACTURING OF ELECTRICALLY CONDUCTIVE MICROSTRUCTURES BY DROPWISE PRINTING AND LASER CURING OF NANOPARTICLE-SUSPENSIONS

ABSTRACT A novel method for the manufacturing of electric microconductors for semiconductor and other devices is presented. The method brings together three technologies: controlled (on demand) printing, laser curing, and the employment of nanoparticles of matter, possessing markedly different properties (here, melting point) than their bulk counterparts. A suspension of gold particles in toluene solvent is employed to print electrically conducting line patterns utilizing a modified on demand ink jet printing process. To this end, microdroplets of 80-100 µm diameters are deposited on a moving substrate such that the droplets form continuous lines. Focused laser irradiation is utilized in order to evaporate the solvent, melt the metal nanoparticles in the suspension, and sinter the suspended particles to form continuous, electrically conducting gold microlines on a substrate. The ultra fine particles in the suspension have a diameter size range of 2 -5 nm. Due to curvature effects of such small particles, the melting point is markedly lower (400°C) than that of bulk gold (1063°C). Thermodynamic aspects of the effect of particle size on the melting and evaporation temperatures of gold and toluene, respectively, are discussed in the paper. The structure and line width of the cured line as a function of the laser irradiation power and stage velocity are reported in detail. Preliminary measurements of the electrical conductivity are represented

Fahrgastanforderungen und -verhalten im U-Bahn-Verkehr

This thesis explores passenger requirements and behaviour on key aspects of metro travel, with focus on future-oriented developments such as metro automation, platform distribution control, positioning of (real-time) information screens on the platform and preferred seating and sitting positions in the vehicle. Combining quantitative and qualitative methods, the study aims to understand both the requirement of passengers and their actual behaviour in the public transport.A structured survey (n=899) was conducted among passengers researching acceptance of automatic metros, influence of real-time information systems on the travel habits, sense of security on the platforms and the positioning behaviour inside the carriage. Additionally, qualitative insights were gathered through expert interviews with professionals from transport operators and research institutions in German-speaking countries. The analysis included descriptive and inferential statistics, such as ANOVA and Chi-Squared tests, as well as thematic interpretation of open responses and interview data. The findings indicate a strong demand for clear and situationally relevant information, particularly in unfamiliar or disrupted travel context. Passengers expressed a desire for communication that goes beyond standard announcements, favouring context sensitive updates that support real-time decision-making, such as crowding levels and delays. Platform distributions and crowding were identified as key factors influencing perceived safety and comfort. Respondents emphasized the importance of even passenger flow across the platform and within trains, noting that crowded entrance areas and unclear boarding procedures can lead to discomfort, longer dwell times and safety concerns. While automation is generally accept-ed, it is often met with scepticism when they lack clear information about the safety systems and operational procedures of automated metros. Preferences and expectations vary significantly across demographic groups, highlighting the importance of inclusive communication and design strategies. This thesis concludes with recommendations for user-centred transport planning and points several areas for future research, including behavioural studies and international comparison. Ultimately, the results underline the value of integrating passenger feedback in the ongoing evolution of metro systems

Disseny i anàlisi de l'actuador de direcció d'un Formula Student

Els cotxes autònoms són el futur. Com a component de l’equip de competició BCN eMotorsport, que sempre treballa per innovar i estar en la Vanguardia, tenim un cotxe elèctric autònom que participa en les competicions internacionals de Formula Student. L'objectiu del treball és determinar l’actuador de direcció més adient pel nou cotxe de competició autònom de l’equip, anomenat Cat14. Primer s’ha fet una breu introducció en les competicions de Formula Student i la seva normativa. S’ha partit de l’anterior cotxe autònom, el “Xaloc”, i s’han analitzat les prestacions i les possibles millores. A continuació s’ha impartit un model simulat de Matlab amb la nova dinàmica del vehicle i s’han assimilat els paràmetres de conducció d’un pilot al funcionament d’un motor. A partir d’aquestes dades s’ha cercat el motor del mercat que millor complís els requeriments. El resultat de l’estudi és l’elecció del motor EC 60 flat de 200 W juntament amb la reductora GP 52C (3,5:1) de la marca Maxon. Un cop escollit l’actuador s’ha dissenyat un suport que compleix els requeriments de funcionament. Finalment, s’han especificat els costos del project

From model intercomparison toward benchmark UV spectra for six real atmospheric cases

The validity of a radiative transfer model can be checked either by comparing its results with measurements or with solutions for artificial cases. Unfortunately, neither type of comparison can guarantee that the spectral UV surface irradiance is accurately calculated for real atmospheric cases. There is a need therefore for benchmarks, i.e., standard results that can be used as a validation tool for UV radiation models. In this paper we give such benchmarks for six cloud-free situations. The chosen cases are characterized by different values of solar zenith angle, ozone column, aerosol loading, and surface albedo. Observations are also available for these cases to allow a further comparison between model results and measurements. An intercomparison of 12 numerical models is used to construct the benchmarks. Each model is supplied with identical input data, and a distinction is made between models that assume a planeparallel geometry and those that use a pseudospherical approximation. Differences remain between the model results, because of different treatments of the input data set. Calculations of direct and global transmission and direct and global irradiance are within 3% for wavelengths longer than 320 nm. For the low-Sun cases the calculations are within 10% for wavelengths longer than 300 nm. On the basis of these calculations, six benchmark UV spectra (295–400 nm) are established with a standard deviation of 2%. Relative standard deviations are higher for the lowest absolute intensities at low Sun (5% at 300 nm). The variation between models is typically less than the variation seen between model and measurement. Differences between the benchmarks and the observed spectra are mainly due to the uncertainty in the input parameters. In four of the six cases the benchmarks agree with the observed spectra within 13% over the whole UV spectral region

MAGNETIC FIELD DEPENDENCE OF THE 57Fe HYPERFINE INTERACTION IN Y(Fe0.1Co0.9)2 AND (Ho0.1Y0.9) (Fe0.1Co0.9)2

No abstract availabl

MÖSSBAUER AND MAGNETIC INVESTIGATIONS OF Y(FexAl1-x)2

No abstract availabl