Інтерактивний контроль при формоутворенні багатогабаритних деталей

Physical phenomenon of warping (springing) can be observed as a technological heritage after large-dimensional articles forming or curing and consequent cooling of composite articles. This phenomenon can be seen as gaps between ready article contour and forming jig contour. Deviation degree of ready article surface from theoretical contour and article dimensions has to be controlled during manufacturing. Application of auxiliary controlling jig leads to expenses and labor-manufacturability increasing. Possibility of application forming jig with inserted jet gages is considered for articles shape controlling. Such gages and realization of acoustic methods allow to control not only final article shape but also geometry on intermediate stages of manufacturing.Після формоутворення багатогабаритних листових деталей з листових механічних заготовок або полімеризації і охолодження деталей з композитних матеріалів проявляється технологічна спадковість у вигляді викривлення (пружнення). Це спостерігається у вигляді неприлягання готової деталі до формозадаючої поверхні технологічного оснащення. При контролі якості формозміни необхідно вимірювати ступінь порушення форми і розмірів. Застосування контрольної оснастки дорого і складно. Розглянуто можливість використання для контролю формозадаючої оснастки з встановленими в ній повітряними струминними датчиками. Такі датчики і застосування акустичних методів дозволяють контролювати не тільки кінцеву форму заготовки, а й форму заготовки на попередваріантних етапах формозміни

Polydisperse spray flames in vortex flows

[EN] A new mathematical analysis of the dynamics of laminar spray diffusion flames in the vicinity of a vortex flow field is presented. The governing equations for a spray evaporating in an unsteady vortex are studied. New similarity solutions are found for the dynamics of the spray and the flame it supports. Analytical solutions for the spray flames are derived using Schvab-Zeldovich parameters, through which the radial evolution of the flames is found. The results based on the solution reveal the significant influence the droplets size has on the diffusion flame dynamics in the vicinity of vortical flows.Dagan, Y.; Katoshevski, D.; Greenberg, BJ. (2017). Polydisperse spray flames in vortex flows. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 702-708. https://doi.org/10.4995/ILASS2017.2017.4716OCS70270

Integrating activity-based travel-demand models with land-use and other long-term lifestyle decisions

This paper extends and integrates the general activity-based model framework to present the complex relationship between long-term individual decisions, such as residential location, and daily activity and travel-behavior decisions. More specifically, it demonstrates the use of an activity-based accessibility (ABA) measure as an important variable in residential zone choice, thus serving as the link between short-term activity and travel decisions and long-term residential choice decisions. We develop a partial activity-based model accounting for the interrelationship of the main activity type, travel destination and mode choice. The log-sum at the top of the hierarchy of this model is the ABA measure capturing the overall utility of all travel alternatives. The results show that this measure is a highly significant variable in the residential-choice model, clearly indicating the great influence of activity accessibility, short-term opportunities, and travel decisions on residential area choice. All other log-sums were also significant, showing the interrelationships of all choices. Specifically, the destination-choice log-sum in the main activity-choice model demonstrates that as accessibility increases, people are more likely to participate in out-of-home activities

An analytical study on the mechanism of grouping of droplets

The condition for the formation of droplet groups in liquid sprays is poorly understood. This study looks at a simplified model system consisting of two iso-propanol droplets of equal diameter, Dd0, in tandem, separated initially by a center-to-center distance, a20, and moving in the direction of gravity with an initial velocity, Vd0>Vt, where Vt is the terminal velocity of an isolated droplet from Stokes flow analysis. A theoretical analysis based on Stokes flow around this double-droplet system is presented, including an inertial correction factor in terms of drag coefficient to account for large Reynolds numbers (≫1). From this analysis, it is observed that the drag force experienced by the leading droplet is higher than that experienced by the trailing droplet. The temporal evolutions of the velocity, Vd(t), of the droplets, as well as their separation distance, a2(t), are presented, and the time to at which the droplets come in contact with each other and their approach velocity at this time, ΔVd0, are calculated. The effects of the droplet diameter, Dd0, the initial droplet velocity, Vd0, and the initial separation, a20 on to and ΔVd0 are reported. The agreement between the theoretical predictions and experimental data in the literature is good.Deutsche Forschungsgemeinschaft (DFG)Stuttgart Center for Simulation Science (SimTech) EXC 207

Chemical characterization of ambient aerosol collected during the northeast monsoon season over the Arabian Sea: Anions and cations

Ambient aerosol samples were collected over the Arabian Sea during the month of March 1997, aboard the German R/V Sonne, as part of the German JGOFS project (Joint Global Ocean Flux Study). This is the third study in a series of analogous measurements taken over the Arabian Sea during different seasons of the monsoon. Dichotomous high volume collector samples were analyzed for anions and cations upon return to the laboratory. Anthropogenic pollutant concentrations were larger during the first part of the cruise, when air masses originated over the Indian subcontinent. Total NSS‐SO42− concentrations amounted to 2.94 ± 1.06 μg m−3 of which 92.1 ± 4.5% was present in the fine fraction. NSS‐SO42− source apportionment analysis with multivariate linear regression models revealed that in the coarse fraction half is biogenically and half anthropogenically derived, while in the fine fraction only 6% seemed of biogenic origin and 84% anthropogenic and 10% crustal in nature. Chloride deficits up to 99.1% in the fine fraction were observed. The average Cl− deficit in the fine fraction was 89.0 ± 9.4%, potentially related to NSS‐SO42− acid displacement and Cl reactive species formation, while in the coarse fraction it was 25.6 ± 21.3%, with NO3− being the preferred species for acid displacement

The hemispheric contrast in cloud microphysical properties constrains aerosol forcing

The change in planetary albedo due to aerosol−cloud interactions during the industrial era is the leading source of uncertainty in inferring Earth’s climate sensitivity to increased greenhouse gases from the historical record. The variable that controls aerosol−cloud interactions in warm clouds is droplet number concentration. Global climate models demonstrate that the present-day hemispheric contrast in cloud droplet number concentration between the pristine Southern Hemisphere and the polluted Northern Hemisphere oceans can be used as a proxy for anthropogenically driven change in cloud droplet number concentration. Remotely sensed estimates constrain this change in droplet number concentration to be between 8 cm−3 and 24 cm−3. By extension, the radiative forcing since 1850 from aerosol−cloud interactions is constrained to be −1.2 W⋅m−2 to −0.6 W⋅m−2. The robustness of this constraint depends upon the assumption that pristine Southern Ocean droplet number concentration is a suitable proxy for preindustrial concentrations. Droplet number concentrations calculated from satellite data over the Southern Ocean are high in austral summer. Near Antarctica, they reach values typical of Northern Hemisphere polluted outflows. These concentrations are found to agree with several in situ datasets. In contrast, climate models show systematic underpredictions of cloud droplet number concentration across the Southern Ocean. Near Antarctica, where precipitation sinks of aerosol are small, the underestimation by climate models is particularly large. This motivates the need for detailed process studies of aerosol production and aerosol−cloud interactions in pristine environments. The hemispheric difference in satellite estimated cloud droplet number concentration implies preindustrial aerosol concentrations were higher than estimated by most models