Icosahedron designs

It is known from the work of Adams and Bryant that icosahedron designs of order v exist for v ≡ 1 (mod 60) as well as for v = 16. Here we prove that icosahedron designs exist if and only if v ≡ 1, 16, 21 or 36 (mod 60), wit

Designs for graphs with six vertices and nine edges

The design spectrum has been determined for eleven of the 21 graphs with six vertices and nine edges. In this paper we completely solve the design spectrum problem for the remaining ten graphs

Completing the design spectra for graphs with six vertices and eight edges

Apart from two possible exceptions, the design spectrum has been determined for every graph with six vertices and at most eight edges. The purpose of this note is to establish the existence of the two missing designs, both of order 32

Theta Graph Designs

We solve the design spectrum problem for all theta graphs with 10, 11, 12, 13, 14 and 15 edges

Spontaneous thermal runaway as an ultimate failure mechanism of materials

The first theoretical estimate of the shear strength of a perfect crystal was given by Frenkel [Z. Phys. 37, 572 (1926)]. He assumed that as slip occurred, two rigid atomic rows in the crystal would move over each other along a slip plane. Based on this simple model, Frenkel derived the ultimate shear strength to be about one tenth of the shear modulus. Here we present a theoretical study showing that catastrophic material failure may occur below Frenkel's ultimate limit as a result of thermal runaway. We demonstrate that the condition for thermal runaway to occur is controlled by only two dimensionless variables and, based on the thermal runaway failure mechanism, we calculate the maximum shear strength $\sigma_c$ of viscoelastic materials. Moreover, during the thermal runaway process, the magnitude of strain and temperature progressively localize in space producing a narrow region of highly deformed material, i.e. a shear band. We then demonstrate the relevance of this new concept for material failure known to occur at scales ranging from nanometers to kilometers.Comment: 4 pages, 3 figures. Eq. (6) and Fig. 2a corrected; added references; improved quality of figure

Rate dependent shear bands in a shear transformation zone model of amorphous solids

We use Shear Transformation Zone (STZ) theory to develop a deformation map for amorphous solids as a function of the imposed shear rate and initial material preparation. The STZ formulation incorporates recent simulation results [Haxton and Liu, PRL 99 195701 (2007)] showing that the steady state effective temperature is rate dependent. The resulting model predicts a wide range of deformation behavior as a function of the initial conditions, including homogeneous deformation, broad shear bands, extremely thin shear bands, and the onset of material failure. In particular, the STZ model predicts homogeneous deformation for shorter quench times and lower strain rates, and inhomogeneous deformation for longer quench times and higher strain rates. The location of the transition between homogeneous and inhomogeneous flow on the deformation map is determined in part by the steady state effective temperature, which is likely material dependent. This model also suggests that material failure occurs due to a runaway feedback between shear heating and the local disorder, and provides an explanation for the thickness of shear bands near the onset of material failure. We find that this model, which resolves dynamics within a sheared material interface, predicts that the stress weakens with strain much more rapidly than a similar model which uses a single state variable to specify internal dynamics on the interface.Comment: 10 pages, 13 figures, corrected typos, added section on rate strengthening vs. rate weakening material

Use of reflection in medical education

Title from PDF of title page (University of Missouri--Columbia, viewed on Sept 10, 2010).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Joe F. Donaldson.Vita.Ph. D. University of Missouri--Columbia 2009.Physicians deal with complex and ill-structured problems and must reflect in order to function professionally while adapting to their patients' needs. This qualitative single case study explores the meaning and use of reflection in the professional preparation of physicians within the medical school of a Midwestern University. Along with a review of the types of reflection assessed (Aukes et al., 2007) and an analysis of Epstein's (1999) Levels of Mindfulness in guided student reflections, faculty and administrators were interviewed to learn more about their perspectives related to reflection. Assessing reflection in medical education is complicated by a lack of agreement about definitions and goals. Although scientific reflection and clinical reflection are more heavily assessed in written evaluations, faculty tended to discuss personal reflection (learning from experience) more during interviews. Most interviewees focused on one aspect of the phases of reflection (trigger, critical analysis, or outcome) rather than the entire process. Some were particularly uncomfortable with the idea of assessing an internal process. The use of Epstein's (1999) Level of Mindfulness was useful in assessing quality and focus of students' written narratives, however the levels do not work well as a continuum for this purpose and proved to be too broad to detect more subtle shifts in thinking across time. In addition, encouraging students to tell stories seems to stimulate deeper reflection. Using common definitions can help facilitate meaningful opportunities for reflection into the curriculum.Includes bibliographical reference

Placing the transfer of learning at the heart of HRD Practice

Training evaluation is a key area of Human Resource Development, however, measuring the effectiveness of training and the transfer of learning from a training programme to the workplace can be a challenging activity. This is even more problematic for a training provider who does not have the continuous relationship or access to performance measures of an in-house training department. This paper reports on the evaluation of a training model, assessing the impact from introduction to completion of the cycle. There are three partners in this research project: the training company, the client organisation and the university researchers. Synaptic Change Ltd is a training consultancy delivering bespoke training to organisations. Utilising a case study approach, this project reports on the evaluation of their training model through its introduction at Connect Housing, a charitable housing and support provider. This presents an interesting context for the study as researchers have suggested the distinctive value led culture of the Voluntary Sector can support a strong learning culture within the organisation. The project seeks to assess the value of learning to the organisation derived from the introduction of the model. The paper explores theoretical and empirical research concerning the evaluation of training and discusses the context of the case study organisation. It then positions the methodology employed and how data will be collected. As a working paper, the findings are not available at this time but will be presented and discussed at the UFHRD conference

Development of a three-dimensional two-fluid code with transient neutronic feedback for LWR applications

The development of a three-dimensional coupled neutronics/thermalhydraulics code for LWR safety analysis has been initiated. The transient neutronics code QUANDRY has been joined to the two-fluid thermal-hydraulics code THERMIT with the appropriate feedback mechanisms modeled. A literature review of the existing coupled neutronics/thermal-hydraulics codes is presented. It indicates that all of the known codes have limitations in their neutronic and/or thermal-hydraulic models which limit their generality of application and accuracy. It was also found that a tandem coupling scheme was most often employed and generally performed well. A detailed steady-state and transient coupling scheme based on the tandem technique was devised, taking into account the important operational characteristics of QUANDRY and THERMIT. The two codes were combined and the necessary programming modifications were performed to allow steady-state calculations with feedback. A simple steady-state sample problem was produced for the purpose of testing and debugging the coupled code

Strain localization in a shear transformation zone model for amorphous solids

We model a sheared disordered solid using the theory of Shear Transformation Zones (STZs). In this mean-field continuum model the density of zones is governed by an effective temperature that approaches a steady state value as energy is dissipated. We compare the STZ model to simulations by Shi, et al.(Phys. Rev. Lett. 98 185505 2007), finding that the model generates solutions that fit the data,exhibit strain localization, and capture important features of the localization process. We show that perturbations to the effective temperature grow due to an instability in the transient dynamics, but unstable systems do not always develop shear bands. Nonlinear energy dissipation processes interact with perturbation growth to determine whether a material exhibits strain localization. By estimating the effects of these interactions, we derive a criterion that determines which materials exhibit shear bands based on the initial conditions alone. We also show that the shear band width is not set by an inherent diffusion length scale but instead by a dynamical scale that depends on the imposed strain rate.Comment: 8 figures, references added, typos correcte