Adhesion of Graphite Fibers to Epoxy Matrices: II. The Effect of Fiber Finish

Reinforcing fibers are available from various manufacturers with matrix compatible “finishes” applied to them. Usually these finishes or coatings are 100-200 nm thick resin layers applied after surface treatment. Their function has been hypothesized as being to enhance adhesion through either protecting the fiber from handling damage, protecting the fiber surface reactivity, or improving fiber wettability. This study of finished and unfinished graphite fibers concludes that the mechanism by which an epoxy compatible finish operates is different from what has been hypothesized to date. The finish layer creates a brittle interphase layer between the fiber and matrix which increases the interfacial shear strength but at the expense of changing the failure mode from interfacial to matrix.     

FT-IR Microscopy Studies of Water Ingress into Aluminum-Adhesive Joints

FT-IR microscopy of the effect of humidity on epoxy thin films on anodized aluminum surfaces was performed in the absence of external stress. The oxide transformation was observed in the anodized samples. Moisture damage was greater in the untreated aluminum samples indicating that interfacial debonding occurs faster in these samples. Water damage was localized spatially. The only organic reaction seen was at the epoxy/air interface giving carboxylates at the surface.     

Puzzle - an efficient,compression independent video encryption algorithm

Real-time video streams require an efficient encryption method to ensure their confidentiality. One of the major challenges in designing a video encryption algorithm is to encrypt the vast amount of video data in real-time to satisfy the stringent time requirements. Video encryption algorithms can be classified according to their association with video compression into joint compression and encryption algorithms and compression-independent encryption algorithms. The latter have a clear advantage over the former regarding the incorporation into existing multimedia systems due to their independence of the video compression. In this paper we present the compression-independent video encryption algorithm Puzzle, which was inspired by the children game jigsaw puzzle. It comprises two simple encryption operations with low computational complexity: puzzling and obscuring. The scheme thereby dramatically reduces the encryption overhead compared to conventional encryption algorithms, such as AES, especially for high resolution video. Further outstanding features of Puzzle are a good trade-off between security demands and encryption efficiency, no impairment on video compression efficiency, and an easy integration into existing multimedia systems. This makes Puzzle particularly well-suited for these security-sensitive multimedia applications, such as videoconferencing, where maximal security and minimal encryption overhead are desired simultaneously.     

An emotion understanding framework for intelligent agents based on episodic and semantic memories

Emotional intelligence is the ability to process information about one’s own emotions and the emotions of others. It involves perceiving emotions, understanding emotions, managing emotions and using emotions in thought processes and in other activities. Emotion understanding is the cognitive activity of using emotions to infer why an agent is in an emotional state and which actions are associated with the emotional state. For humans, knowledge about emotions includes, in part, emotional experiences (episodic memory) and abstract knowledge about emotions (semantic memory). In accordance with the need for more sophisticated agents, the current research aims to increase the emotional intelligence of software agents by introducing and evaluating an emotion understanding framework for intelligent agents. The framework organizes the knowledge about emotions using episodic memory and semantic memory. Its episodic memory learns by storing specific details of emotional events experienced firsthand or observed. Its semantic memory is a lookup table of emotion-related facts combined with semantic graphs that learn through abstraction of additional relationships among emotions and actions from episodic memory. The framework is simulated in a multi-agent system in which agents attempt to elicit target emotions in other agents. They learn what events elicit emotions in other agents through interaction and observation. To evaluate the importance of different memory components, we run simulations with components “lesioned”. We show that our framework outperformed Q-learning, a standard method for machine learning.     

VEGF‐Functionalized Polyelectrolyte Multilayers as Proangiogenic Prosthetic Coatings

Stimulation of transprosthetic vascularization represents an interesting strategy in implantology to allow rapid tissue integration and finally to avoid prosthetic rejection. To achieve this goal, we modified the surface of porous titanium implants with polyelectrolyte multilayer (PEM) films functionalized with vascular endothelial growth factor (VEGF). Among the two PEM systems investigated, poly(L‐lysine)/poly(L‐glutamic acid) (PLL/PGA) and poly(allylamine hydrochloride)/poly(sodium 4‐styrenesulfonate) (PAH/PSS), the (PAH/PSS)₄ architecture was selected to functionalize porous titanium, both for its high efficiency to adsorb VEGF and for its biocompatibility toward endothelial cells. In an original way, we unambiguously demonstrated that VEGF adsorbed on (PAH/PSS)₄ maintains its bioactivity in vitro and stimulates endothelial cells proliferation. This effect was correlated with specific activation of intracellular signaling pathways induced by successive phosphorylation of the endothelial VEGF receptor VEGFR2 and mitogen‐activated protein kinases (MAPK) ERK1/2. By clearly demonstrating the proangiogenic activity of the VEGF‐PEM coating in vitro, the present study constitutes a first step toward in vivo application.     

Hybrid modeling and identification of dry friction systems,application to a clutch actuator

This paper proposes a new general framework, i.e. hybrid modeling, to model dry friction systems. The proposed hybrid model has two modes (states): one models the system sliding, the second the system sticking. The model's main advantage is the adaptation capability to observable phenomena. It is shown for the most common behaviors encountered experimentally and comparisons with other models presented in the literature are carried out. The models and methods of parameters identification of the literature are generally validated experimentally on system with sensors and actuators of high precision. This paper focuses on modeling and identifying complex mechanical system with low resolution sensors. The presented theoretical work is validated experimentally on a clutch-by-wire.     

Messung des transienten Massenaustrages und der kurzzeitigen thermofluiddynamischen Vorgänge während der Reaktorentlastung

On the basis of a differential measurement of the reactor reaction force change as a function of the relief time and elimination of the inert reactor mass the integral discharged mass can be reproduced with an accuracy of about 2%. In combination with a parallel highly in time solvable measurement of the swelling mixture conductance ahead of the discharge nozzle on the reactor top a relationship between the intensive fluctuations of the reaction force and the corresponding changes of the discharged mass as well as the periodically repeating intermittent swelling of the mixture due to bubble production, resp., evaporation could be established.     

Phase and Curing Behavior of Polybutadiene/Diallyl Phthalate Blends Monitored by FT-IR Imaging Using Focal-Plane Array Detection

The phase morphology and interfacial regions of cured and uncured polybutadiene/diallyl phthalate (PBD/DAP) blends that exhibit upper critical solution temperature (UCST) behavior have been characterized using an FT-IR microscopic imaging technique with focal-plane array detection. The observations of domain size and structure were based on monitoring characteristic infrared C-H, C [Formula: see text] O, and C-O modes of the blend components. The basic phase morphology of the uncured blend was monitored immediately after sample preparation and after 24 h. The average domain sizes of the uncured blend increased with aging by coalescence of smaller particles. The chemical compositions of the separated domains were determined by measuring ratios of integrated intensities and analyzed using a calibration curve. Finally, the blends were cured above the UCST and an apparently homogeneous network was obtained.     

Efficient and inefficient ant coverage methods

Ant robots are simple creatures with limited sensing and computational capabilities. They have the advantage that they are easy to program and cheap to build. This makes it feasible to deploy groups of ant robots and take advantage of the resulting fault tolerance and parallelism. We study, both theoretically and in simulation, the behavior of ant robots for one-time or repeated coverage of terrain, as required for lawn mowing, mine sweeping, and surveillance. Ant robots cannot use conventional planning methods due to their limited sensing and computational capabilities. To overcome these limitations, we study navigation methods that are based on real-time (heuristic) search and leave markings in the terrain, similar to what real ants do. These markings can be sensed by all ant robots and allow them to cover terrain even if they do not communicate with each other except via the markings, do not have any kind of memory, do not know the terrain, cannot maintain maps of the terrain, nor plan complete paths. The ant robots do not even need to be localized, which completely eliminates solving difficult and time-consuming localization problems. We study two simple real-time search methods that differ only in how the markings are updated. We show experimentally that both real-time search methods robustly cover terrain even if the ant robots are moved without realizing this (say, by people running into them), some ant robots fail, and some markings get destroyed. Both real-time search methods are algorithmically similar, and our experimental results indicate that their cover time is similar in some terrains. Our analysis is therefore surprising. We show that the cover time of ant robots that use one of the real-time search methods is guaranteed to be polynomial in the number of locations, whereas the cover time of ant robots that use the other real-time search method can be exponential in (the square root of) the number of locations even in simple terrains that correspond to (planar) undirected trees. This revised version was published online in August 2006 with corrections to the Cover Date.