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The shape of me and other stuff
Rhyme and silhouette drawings introduce the shape of bugs, balloons, peanuts, camels, spider webs, and many other familiar objects.
Book
Characterization of Polyurethane Shape Memory Polymer and Determination of Shape Fixity and Shape Recovery in Subsequent Thermomechanical Cycles
Multifunctional polyurethane shape memory polymers (PU-SMPs) have been of increasing interest in various applications. Here we report structure characterization, detailed methodology, and obtained results on the identification of functional properties of a thermoset PU-SMP (MP4510) with glass transition temperature of 45 °C. The stable, chemically crosslinked network of this thermoset PU-SMP results in excellent shape memory behavior. Moreover, the proximity of the activation temperature range of this smart polymer to room and body temperature enables the PU-SMP to be used in more critical industrial applications, namely fast-response actuators. The thermomechanical behavior of a shape memory polymer determines the engineering applications of the material. Therefore, investigation of the shape memory behavior of this class of commercial PU-SMP is of particular importance. The conducted structural characterization confirms its shape memory properties. The shape fixity and shape recovery properties were determined by a modified experimental approach, considering the polymer’s sensitivity to external conditions, i.e., the temperature and humidity variations. Three thermomechanical cycles were considered and the methodology used is described in detail. The obtained shape fixity ratio of the PU-SMP was approximately 98% and did not change significantly in the subsequent cycles of the thermomechanical loading due to the stability of chemical crosslinks in the thermoset materials structure. The shape recovery was found to be approximately 90% in the first cycle and reached a value higher than 99% in the third cycle. The results confirm the effect of the thermomechanical training on the improvement of the PU-SMP shape recovery after the first thermomechanical cycle as well as the effect of thermoset material stability on the repeatability of the shape memory parameters quantities.
Journal Article
Thinking about U: Theorizing and testing U- and inverted U-shaped relationships in strategy research
Research summary: U- and inverted U-shaped relationships are increasingly explored in strategy research, with 11 percent of all articles published in Strategic Management Journal (SMJ) in 2008-2012 investigating such quadratic relationships. Moreover, a movement towards introducing moderation to quadratic relationships has emerged. By reviewing 110 articles published in SMJ from 1980 to 2012, we identify several critical issues in theorizing and testing of these relationships for which current practice falls short. These include insufficient causal argumentation, incorrect testing, mixing up two different types of moderation, and not realizing that the curve can flip completely. For these and other issues, a guideline is provided which, when followed, may bring clarity to theoretical motivation and rigor to empirical testing. Managerial summary: Too much can be as bad as too little. Many relationships in strategic management follow an inverted U-shaped pattern, where moderate levels of a strategy lead to optimal performance. To gain deeper insights into the conventional wisdom that too much of a good thing can be harmful to performance, we discuss how such relationships can be better theorized and tested based on a review of articles exploring U-shaped relationships in Strategic Management Journal during 1980-2012. We identify several critical issues that require close attention and provide a guideline to further develop and validate this important managerial intuition.
Journal Article
The shape of me and other stuff : Dr. Seuss's surprising word book
Rhyme and silhouette drawings introduce the shape of bugs, balloons, peanuts, camels, spider webs, and many other familiar objects.
Book
Shape Memory Polymers as Smart Materials: A Review
Polymer smart materials are a broad class of polymeric materials that can change their shapes, mechanical responses, light transmissions, controlled releases, and other functional properties under external stimuli. A good understanding of the aspects controlling various types of shape memory phenomena in shape memory polymers (SMPs), such as polymer structure, stimulus effect and many others, is not only important for the preparation of new SMPs with improved performance, but is also useful for the optimization of the current ones to expand their application field. In the present era, simple understanding of the activation mechanisms, the polymer structure, the effect of the modification of the polymer structure on the activation process using fillers or solvents to develop new reliable SMPs with improved properties, long lifetime, fast response, and the ability to apply them under hard conditions in any environment, is considered to be an important topic. Moreover, good understanding of the activation mechanism of the two-way shape memory effect in SMPs for semi-crystalline polymers and liquid crystalline elastomers is the main key required for future investigations. In this article, the principles of the three basic types of external stimuli (heat, chemicals, light) and their key parameters that affect the efficiency of the SMPs are reviewed in addition to several prospective applications.
Journal Article
A circle in the sky
A child puts together various simple shapes to build a rocket that will fly to the moon. Includes suggested learning activities.
Book
A Review of Particle Shape Effects on Material Properties for Various Engineering Applications: From Macro to Nanoscale
It is well known that most particle technology studies attempting to predict secondary properties based on primary properties such as size and shape begin with particle characterization, which means the process of determining the primary properties of particles in a wide spectrum from macro to nanoscale. It is a fact that the actual shape of engineering particles used in many industrial applications or processes is neglected, as they are assumed to be “homogeneous spheres” with easily understood behavior in any application or process. In addition, it is vital to control the granular materials used in various industries or to prepare them in desired shapes, to develop better processes or final products, and to make the processes practical and economical. Therefore, this review not only covers basic shape definitions, shape characterization methods, and the effect of particle shape on industrial material properties, but also provides insight into the development of the most suitably shaped materials for specific applications or processes (from nanomaterials used in pharmaceuticals to proppant particles used in hydrocarbon production) by understanding the behavior of particles.
Journal Article
Shapes!
Introduces shapes, including circles, squares, rectangles, triangles, and stars, with colorful illustrations.
Book
Review of Progress in Shape Memory Epoxies and Their Composites
Shape memory polymer (SMP) is capable of memorizing one or more temporary shapes and recovering successively to the permanent shape upon various external stimuli. Beside of the above mentioned one-way variants, also two-way shape memory polymers (SMPs) and shape memory (SM) systems exist which feature a reversible shape change on the basis of “on-off switching” of the external stimulus. The preparation, properties and modelling of shape memory epoxy resins (SMEP), SMEP foams and composites have been surveyed in this exhaustive review article. The underlying mechanisms and characteristics of SM were introduced. Emphasis was put to show new strategies on how to tailor the network architecture and morphology of EPs to improve their SM performance. To produce SMEPs novel preparation techniques, such as electrospinning, ink printing, solid-state foaming, were tried. The potential of SMEPs and related systems as multifunctional materials has been underlined. Added functionality may include, among others, self-healing, sensing, actuation, porosity control, recycling. Recent developments in the modelling of SMEPs were also highlighted. Based on the recent developments some open topics were deduced which are merit of investigations in future works.
Journal Article