A micromechanics-inspired constitutive model for shape-memory alloys that accounts for initiation and saturation of phase transformation

A constitutive model to describe macroscopic elastic and transformation behaviors of polycrystalline shape-memory alloys is formulated using an internal variable thermodynamic framework. In a departure from prior phenomenological models, the proposed model treats initiation, growth kinetics, and saturation of transformation distinctly, consistent with physics revealed by recent multi-scale experiments and theoretical studies. Specifically, the proposed approach captures the macroscopic manifestations of three micromechanial facts, even though microstructures are not explicitly modeled: (1) Individual grains with favorable orientations and stresses for transformation are the first to nucleate martensite, and the local nucleation strain is relatively large. (2) Then, transformation interfaces propagate according to growth kinetics to traverse networks of grains, while previously formed martensite may reorient. (3) Ultimately, transformation saturates prior to 100% completion as some unfavorably-oriented grains do not transform; thus the total transformation strain of a polycrystal is modest relative to the initial, local nucleation strain. The proposed formulation also accounts for tension–compression asymmetry, processing anisotropy, and the distinction between stress-induced and temperature-induced transformations. Consequently, the model describes thermoelastic responses of shape-memory alloys subject to complex, multi-axial thermo-mechanical loadings. These abilities are demonstrated through detailed comparisons of simulations with experiments

Managing Extension’s Internal Brand: Employees’ Perceptions of the Functions and Descriptors of Extension

Employees of UF/IFAS Extension were surveyed to determine their perceptions of the brand’s core identity. More specifically, they evaluated the importance of various functions the organization provides and the effectiveness of various terms for describing Extension work. Respondents included county faculty, county non-faculty, state faculty, and state non-faculty to gain perspectives of groups representing Extension’s brand in Florida. Results indicated employees perceived the core functions were providing research-based information, helping solve problems, providing training for clientele, and providing expertise. Education, training, and providing solutions were perceived to be the most effective terms for describing Extension work to the public. Given that these terms are viewed as most effective internally, these terms should also be used in external communications to provide consistency. “Extension” as a term was not viewed as particularly effective for representing to the public what Extension does. When comparing groups of Extension personnel, there were statistically significant differences, indicating Extension lacks a shared identity across the organization, which could be harmful. State-level faculty, in particular, had less positive viewpoints compared to other respondent groups. It was recommended that interactions be increased between state-level and county-level employees to help mitigate potential issues that would arise because of the organization being geographically distributed in the state and to help build shared identity. Future research was recommended to address the public’s views of functions and descriptors of Extension

Totally Transparent: A Qualitative Study About the Impact of Farm Tours on Bloggers

Producers and agricultural organizations often struggle to effectively and efficiently communicate agricultural practices and values across the green divide. Additionally, producers and agricultural communication professionals must compete with inflammatory or misleading statements communicated to uninformed consumers via the blogosphere and rapidly disseminated on social media. Many organizations are beginning to implement agritourism events as a way of educating the consumer and influential bloggers. This study utilized semi-structured interviews to explore the perceptions, attitudes, and experiences of four bloggers who were invited to a three-day agritourism event. Results showed participants identified personal exposure to transparent farmers yielded an increase in knowledge and appreciation of farming practices that positively impacted their trust in the American farmer and food system. This study expands upon current research being conducted on agritourism events, transparency, and expectancy violations theory and suggests organizations structure agritourism events in such a way as to demonstrate transparency and positively violate the expectations bloggers may have regarding agricultural producers

Networks in the spectral induced polarization

Die spektrale induzierte Polarisation (SIP) ist ein geoelektrisches Verfahren, bei dem die komplexe, frequenzabhängige Impedanz des Untergrunds gemessen wird. Im Vergleich zur Gleichstrom-Geoelektrik werden bei der SIP zusätzliche Parameter gemessen, die Hinweise auf hydraulische Parameter des Materials liefern können. Dies geschieht in der Regel mittels empirischer Gleichungen. Um eine hohe Allgemeingültigkeit zu erzielen, ist es notwendig, theoretische Modelle der SIP auf mikroskopischer Skala des Porenraumes zu entwickeln. In dieser Arbeit wird ein existierendes, semi-analytisches Membranpolarisations-Modell auf 2D und 3D Impedanz-Netzwerke erweitert, welche numerisch gelöst werden und eine Gesamt-SIP-Antwort zu erhalten. Das Originalmodell verwendet zwei, mit einem elektrolytischen Fluid gefüllte Zylinder unterschiedlicher Größe, um einen Membranpolarisations-Effekt an deren Übergang zu simulieren. Das Modell ist bereits in der Lage, Grundeigenschaften von SIP-Spektren aus Labormessungen zu reproduzieren. Um eine realistischere Abbildung von porösen Materialien, zu erreichen, werden unterschiedliche Zylinderkombinationen des Originalmodells zu einem Netzwerk vereinigt. Im Vorfeld der Netzwerkerweiterung wird das Originalmodell in mehreren Punkten überarbeitet, um mehrwertige und asymmetrische Elektrolyte sowie konzentrationsabhängige Ionenmobilitäten zu unterstützen. Anschließend wird das Originalmodell einer Sensitivitätsanalyse unterzogen. Die konstruierten Netzwerke werden mit realen Sandsteinen verglichen, für die sowohl die geoelektrischen als auch die petrophysikalischen Eigenschaften gemessen wurden. Die geometrischen Parameter des Netzwerkes (wie die Radien, Längen und ihre Häufigkeitsverteilungen) werden so gewählt, dass sie gemessene makroskopische Parameter, wie spezifische innere Oberfläche und Porosität wiedergeben. Hierzu werden mittels Quecksilberporosimetrie gemessene Radienverteilungen auf drei unterschiedliche Weisen interpretiert, die zunächst eine qualitative und dann eine quantitative Anpassung der simulierten SIP-Spektren an die gemessenen ermöglichen. Die Simulationsergebnisse zeigen, dass das entwickelte Netzwerkmodell grundsätzlich in der Lage ist, gemessene SIP-Daten mit den hydraulischen Eigenschaften des untersuchten Materials in Verbindung zu bringen und zum Verständnis des Polarisationseffektes auf mikroskopischer Skala beizutragen.Spectral induced polarization (SIP) is a geoelectric method in which the complex, frequency-dependent impedance of the soil is measured. Compared to DC geoelectrics, SIP measures additional parameters that can provide information on hydraulic parameters of the material. This is usually done using empirical equations. In order to achieve a high general validity, it is necessary to develop theoretical models of the SIP on a microscopic scale of the pore space. In this thesis, an existing semi-analytical membrane polarization model is extended to 2D and 3D impedance networks, which are solved numerically to obtain a total SIP response. The original model uses two cylinders of different sizes filled with an electrolytic fluid to simulate a membrane polarization effect at their transition. The model is already capable of reproducing basic properties of SIP spectra from laboratory measurements. In order to achieve a more realistic image of porous materials, such as sandstones, different cylinder combinations of the original model are combined into a network. Prior to the network expansion, the original model is revised in several points to support multivalent and asymmetric electrolytes as well as concentration-dependent ion mobilities. The original model is then subjected to a sensitivity analysis in order to examine it for equivalent parameters. The constructed networks are compared with real sandstones, for which both the geoelectric and petrophysical properties have been measured. The geometric parameters of the network (such as pore radii, pore lengths and their frequency distributions) are selected to reflect measured macroscopic parameters such as specific internal surface area and porosity. For this purpose, radius distributions measured by mercury porosimetry are interpreted in three different ways, which make first a qualitative and then a quantitative fit of the simulated SIP spectra to the measured ones possible. The simulation results show that the developed network model is basically able to link measured SIP data with the hydraulic properties of the investigated material and to contribute to understanding the polarization effect on a microscopic scale

Green growth: an exploratory study of metro and non-metro garden centers use of new-media marketing

Master of ScienceDepartment of Communications and Agricultural EducationLauri M. BakerGarden centers are facing increasing market pressure from big-box retail stores that offer similar products at more competitive prices but lack a quality produce and exceptional service. In order to differentiate themselves from big-box stores, garden centers must build relationships with their customers which can increase marketing reach. Marketing ability and reach is limiting the expansion of Kansas garden centers which spend the majority of their advertising dollars on traditional media. However, social media can be an effective method for not only understanding consumers but also developing profitable relationships with customers. The purpose of this qualitative study was to explore the perceptions and experiences of stakeholders of metro and non-metro garden centers as they use new media to market their business. Findings indicate garden center stakeholders prefer to use traditional media channels to market to their customers, lack a clear strategy and objectives related to new-media marketing, and are not effectively implementing relationship marketing principles