ON THERMODYNAMICS OF THIN FILMS: THE MECHANICAL EQUILIBRIUM CONDITION AND CONTACT ANGLES

A thermodynamic model for plane parallel thin liquid films applicable to solid-liquid-vapor systems was presented using the detailed method. The film was modeled as a bulk phase bound by two dividing surfaces. The thermodynamic thickness of the film was established as well as excess properties such as film tension. The analysis using this model yielded disjoining pressure definition identical to the literature reports. The effect of definition for contact angle on the resulting mechanical equilibrium condition was also demonstrated. It was concluded that from a theoretical perspective it is important to clearly define contact angles as the angle a sessile drop makes with either the solid phase or the thin film. However, on a practical level for most cases, the difference between using either of the two mechanical equilibrium conditions to determine film tension or contact angle will be minimal (ascertained by an order of magnitude analysis). The attempt was also made to bring about clarity concerning some of the questions in the literature regarding the thermodynamic model for thin films presented by Li and Neumann.     

Drivers’ Performance Examination using a Personalized Adaptive Curve Speed Warning: Driving Simulator Study

ABSTRACT

A great number of traffic accidents occur during curve negotiation maneuvers. Most of these accidents could be avoided if drivers are provided with information that better guide them through the maneuver. Advanced Driver Assistance Systems (ADAS) such as Curve Speed Warning (CSW) have shown to be effective to improve safety on curve maneuvers by warning drivers of the speed required to make a safe curve maneuver. The effectiveness of such warning systems can potentially improve if the warnings are not only adapted to road and traffic condition but also adapted to individual drivers’ behavior. In this study, an Adaptive Curve Speed Warning (ACSW) system is developed that presents drivers a two-level visual and audio warning considering the variation in individual drivers’ perception-reaction time (PRT). The warning timing is adjusted according to a reward/punishment function to reinforce safer actions while providing an individualized in-time warning. Next, within a driving simulator environment, drivers’ performance using ACSW is compared to a CSW that does not consider PRT variation among drivers. Further, variation in drivers’ performance on curve maneuvers is discussed with respect to drivers’ approaching speed, variation in PRT, and braking behavior. Results show that drivers’ interaction with warning systems varies significantly based on their age and gender. In addition, results show how drivers approaching speed to a curve varies significantly based on road characteristics such as curve advisory speed and curve direction. Results from this study contribute to the development of more intelligent ADAS that could improve drivers’ comfort and safety.     

Study of Edge Effect to Stop Liquid Spillage for Microgravity Application

The ability of a micro-groove to prevent the spreading of HFE-7100 fluid (C₄F₉OCH₃) having low surface tension (γ?= 13.6 mN/m) on a surface is studied. In this study, micro-grooves were made around square openings of a plate made of either polycarbonate or 316 stainless steel. To verify effectiveness of micro-grooves to stop the spread of HFE-7100, experiments were done under non-saturated and saturated conditions. Under non-saturated conditions the micro-grooves on both materials confined the liquid up to apparent angle of 55 ± 5° due to the edge effect. Saturated gas-vapor mixture with vapor mass fraction of w _v = 88% and w _v = 97% did not significantly influence the confinement of the liquid by the micro-groove. This result is promising for application of micro-grooved plates in CIMEX experiment planned for ISS.     

ON THERMODYNAMICS OF THIN FILMS: THE MECHANICAL EQUILIBRIUM CONDITION AND CONTACT ANGLES

A thermodynamic model for plane parallel thin liquid films applicable to solid-liquid-vapor systems was presented using the detailed method. The film was modeled as a bulk phase bound by two dividing surfaces. The thermodynamic thickness of the film was established as well as excess properties such as film tension. The analysis using this model yielded disjoining pressure definition identical to the literature reports. The effect of definition for contact angle on the resulting mechanical equilibrium condition was also demonstrated. It was concluded that from a theoretical perspective it is important to clearly define contact angles as the angle a sessile drop makes with either the solid phase or the thin film. However, on a practical level for most cases, the difference between using either of the two mechanical equilibrium conditions to determine film tension or contact angle will be minimal (ascertained by an order of magnitude analysis). The attempt was also made to bring about clarity concerning some of the questions in the literature regarding the thermodynamic model for thin films presented by Li and Neumann.