THE MAGNIFICATION FACTOR IN SPINNING DROP INTERFACIAL TENSIOMETRY

The accuracy with which the interfacial tension between two immiscible fluid phases can be determined by the spinning drop method is limited by the accuracy with which the spinning drop diameter can be found. Thus, it is important to know the factor by which the cylindrical sample tube and its content magnifies the on-axis drop or bubble. Here, we analyze the image formation and magnification factor of the spinning drop by a non-paraxial ray tracing method of geometric optics. Our analysis shows that when the drop and the walls of the lube are concentric, the magnification factor is exactly the refractive index of the denser fluid surrounding the drop and is independent of the refractive index and wall thickness of the sample tube. Our analysis also reveals that the image, a virtual one, is formed concentric with the drop.     

Environmental optimization of chromium recovery from tannery sludge using a life cycle assessment approach

Life cycle assessment (LCA) was used to evaluate the environmental impact of an oxidative chromium recovery method from tannery sludge, in comparison with the usual landfilling process. Three improvement options (water reduction, byproduct use and anaerobic sludge digestion) were considered. The results showed that the proposed chromium recovery process would be better environmentally than conventional landfilling in all the evaluated impact categories if the amount of chromium recovered was 43 kg per ton of sludge. This amount could be recovered if the chromium concentration was about 20 times higher than that considered in this study. Alternatively, a lower chromium concentration would produce a better result if the recovery method was optimized and implemented at industrial rather than laboratory scale, and if more accurate data were provided on environmental credits for avoiding the chromium production process. Thus, the recovery method is environmentally beneficial when tannery sludge contains a chromium concentration of about 100,000 ppm. According to the literature, such concentrations are not unusual. The results could serve as the basis for further environmental improvements in chromium recovery and tannery sludge management and should be used in decision-making processes, especially for end-of-pipe treatments.     

Flux confinement by artificial arrays and clusters in superconducting films

We have studied the superconducting properties of antidot arrays and mesoscopic antidot clusters near the superconducting-normal phase boundary. Characteristic minima and maxima have been observed in the magnetore-sistance, critical current and phase boundary caused by the formation of stable vortex configurations at the antidots. A comparison with a simple theoretical model has shown that the effects in the arrays as well as in the clusters originate from quantization of the fluxoid at the antidots. This model has enabled an identification of all vortex configurations.     

Boolean operations for 3D simulation of CNC machining of drilling tools

This paper addresses the simulation of drilling tools CNC machining. It describes a novel approach for the computation of the boundary representation of the machined tools. Machining consists of a sequence of boolean operations of difference between the tool and the grinding wheels through time. The proposed method performs the dynamic boolean operations on cross sections of the tool and it reconstructs the 3Dmodel by tiling between the cross sections. The method is based on classical computational geometry algorithms such as intersection tests, hull computations, 2D boolean operations and surface tiling. This approach is efficient and it provides user control on the resolution of the operations.     

Polymerization of methyl methacrylate in 3-component cationic microemulsion

Methyl methacrylate has been polymerized in three-component o/w microemulsions made with the cationic surfactant dodecyltrimethylammonium bromide (DTAB). The effects of temperature type and concentration of initiator (AIBN or potassium persulfate), and surfactant and monomer concentration on polymerization kinetics are investigated. Final conversions and reaction rates increase with increasing monomer and initiator concentrations and with higher reaction temperatures. The rate of polymerization shows initiation and termination intervals, but no constant rate interval is observed. Both molecular weight and particle size decrease as the concentration of initiator increases, regardless of type of initiator. Latexes with small particle size (< 70 nm) and high molecular weights (>10⁶) were obtained in all cases. Activation energies for the microemulsion polymerization of MMA with AIBN (10.3 kcal/mol) and KPS (13.4 kcal/mol) are smaller than that of bulk polymerization using AIBN (20 kcal/mol). © 1993 John Wiley & Sons, Inc.     

Robust economic model predictive control based on a periodicity constraint

This paper proposes robust economic model predictive control based on a periodicity constraint for linear systems subject to unknown‐but‐bounded additive disturbances. In this economic MPC design, a periodic steady‐state trajectory is not required and thus assumed unknown, which precludes the use of enforcing terminal state constraints as in other standard economic formulations. Instead, based on the desired periodicity of system operation, we optimize the economic performance over a set of periodic trajectories that include the current state. To achieve robust constraint satisfaction, we use a tube‐based technique in the economic MPC formulation. The mismatches between the nominal model and the closed‐loop system with perturbations are limited using a local control law. With the proposed robust tube‐based strategy, recursive feasibility is guaranteed. Moreover, under a convexity assumption, the closed‐loop convergence of the closed‐loop system is analyzed, and an optimality certificate is provided to check if the closed‐loop trajectory reaches a neighborhood of the optimal nominal periodic steady trajectory using Karush‐Kuhn‐Tucker optimality conditions. Finally, through numerical examples, we show the effectiveness of the proposed approach.     

Spatial Dependence of the FDI Entry Mode Decision: Empirical Evidence From Emerging Market Enterprises

The entry mode and location choices are two fundamental decisions made by firms after they decide to proceed with foreign direct investment (FDI). In previous studies, these two strategic concerns have usually been studied separately as independent decisions. Following recent claims, we extend beyond the macro-environment of the host country or geographical space to study the interdependence between these two decisions by comparing the effects of two different colocation strategies on the establishment mode and ownership structure of investors in FDI. We tested our hypotheses based on a sample of 162 Chinese-owned subsidiaries in Germany and found spatial dependence in the entry mode strategies, where the existing theories regarding ownership structure prediction for the sampled firms had limited explanatory power. We also observed that the experience of investors had a negative moderating effect on these interactions. Our results suggest the following: (1) the FDI strategies of foreign investors consider conditions that vary among countries as well as within the host economy and place; (2) the entry mode and location choices can be alternative strategies for overcoming barriers to entry in FDIs where a trade-off between both is required; and (3) more efforts are still needed to interpret the FDI behaviors of investors from emerging economies.     

Design and implementation of a secure and trustworthy platform for privacy-aware video surveillance

Worldwide, thousands of video surveillance cameras record our daily activities. People are aware that video surveillance is deployed for the sake of security. However, the privacy of individuals would be endangered if the proper measures were not considered. Privacy-aware video surveillance has historically been addressed by proposals based on detecting individuals and other sensitive parts of the video and hiding them using a variety of techniques. In this paper, we present a comprehensive solution tackling video processing, video protection and management of the Information System. We claim that a video surveillance system can protect our safety and, at the same time, guarantee our privacy. We describe the design and implementation of a privacy-aware video surveillance platform that, in order to be trustworthy, accomplishes with the properties of high detection accuracy, real-time performance and protected video utility. We have tested the proposed platform, and we demonstrate the feasibility of our approach for privacy protection.