A Mixed-Methods Investigation of Factors and Scenarios Influencing College Students’ Decision to Complete Surveys at Five Mid-Western Universities

Achieving respectable response rates to surveys on university campuses has become increasingly more difficult, which can increase non-response error and jeopardize the integrity of data. Prior research has focused on investigating the effect of a single or small set of factors on college students’ decision to complete surveys. We used a concurrent mixed-method design to examine (1) college students’ rationales for choosing to complete or not complete a survey presented to them and (2) their perceptions on the importance of multiple factors on their decision to complete or not complete surveys in a higher education setting. A total of 837 undergraduate and graduate students across five institutions in the state of Ohio completed the qualitative survey component, 808 completed the 72-scenario close-ended survey component, and 701 completed the rank- order component. The survey was administered in the classroom either at the beginning or end of the class period. The college students reported that the person administering, topic, incentives, length, and method of administration are the factors most influencing their decision to complete a survey. The undergraduate students were significantly more likely than graduate students to include incentives as one of the top three important factors in deciding to complete a survey. Qualitative results additionally revealed that the students felt day/time and location of survey request plays an important role in their decision. Recommendations are provided to survey administrators regarding potential effective and ineffective survey recruitment strategies

Finite strain Landau theory of high pressure phase transformations

The properties of materials near structural phase transitions are often successfully described in the framework of Landau theory. While the focus is usually on phase transitions, which are induced by temperature changes approaching a critical temperature T-c, here we will discuss structural phase transformations driven by high hydrostatic pressure, as they are of major importance for understanding processes in the interior of the earth. Since at very high pressures the deformations of a material are generally very large, one needs to apply a fully nonlinear description taking physical as well as geometrical nonlinearities (finite strains) into account. In particular it is necessary to retune conventional Landau theory to describe such phase transitions. In Troster et al (2002 Phys. Rev. Lett. 88 55503) we constructed a Landau-type free energy based on an order parameter part, an order parameter-(finite) strain coupling and a nonlinear elastic term. This model provides an excellent and efficient framework for the systematic study of phase transformations for a wide range of materials up to ultrahigh pressures

Dynamic optimization of a gas-liquid reactor

The final publication is available at Springer via http://dx.doi.org/10.1007/s10910-011-9941-1A dynamic gas-liquid transfer model without chemical reaction based on unsteady film theory is considered. In this case, the mathematical model presented for gas-liquid mass-transfer processes is based on mass balances of the transferred substance in both phases. The identificability property of this model is studied in order to confirm the possible identifiable parameters of the model from a given set of experimental data. For that, a different modeled of the system is given. A procedure for the identification is proposed. On the other hand, the aim of this work is to solve the quadratic optimal control problem, using an explicit representation of the model. The problem includes some results on controllability, observability and stability criteria and the relation between these properties and the parameters of the model. Using the optimal control problem we study the stability of the system and show how the choice of the weighting matrices can improve the behavior of the system but with an increase of the energy control cost. © 2011 Springer Science+Business Media, LLC.This work has been partially supported by PAID-05-10-003-295 and by MTM2010-18228.Cantó Colomina, B.; Cardona Navarrete, SC.; Coll, C.; Navarro-Laboulais, J.; Sánchez, E. (2012). Dynamic optimization of a gas-liquid reactor. Journal of Mathematical Chemistry. 50(2):381-393. https://doi.org/10.1007/s10910-011-9941-1S381393502Bayón L., Grau J.M., Ruiz M.M., Suárez P.M.: Initial guess of the solution of dynamic optimization of chemical processes. J. Math. Chem. Model. 48, 28–37 (2010)Ben-Zvi A., McLellan P.J., McAuley K.B.: Ind. Eng. Chem. Res. 42, 6607–6618 (2003)Cantó B., Coll C., Sánchez E.: Structural identifiability of a model of dialysis. Math. Comp. Model. 50, 733–737 (2009)Cantó B., Coll C., Sánchez E.: Identifiability of a class of discretized linear partial differential algebraic equations. Math. Probl. Eng. 2011, 1–12 (2011)Craciun G., Pantea C.: Identifiability of chemical reaction networks. J. Math. Chem. 44, 244–259 (2008)Dai L.: Descriptor Control Systems. Springer, New York (1989)Deckwer W.D.: Bubble Column Reactors. Wiley, Chichester (1992)Kantarci N., Borak F., Ulgen K.O.: Bubble column reactors. Proc. Biochem. 40(7), 2263–2283 (2005)Kawakernaak H., Sivan R.: Linear Optimal Control Systems. Wiley-Interscience, New York (1972)Kuo B.C.: Automatic Control Systems, 6th edn. Prentice-Hall, Englewood Cliffs (1991)Navarro-Laboulais J., Cardona S.C., Torregrosa J.I., Abad A., López F.: Practical identifiability analysis in dynamic gas-liquid reactors. Optimal experimental design for mass-transfer parameters determination. Comp. Chem. Eng. 32, 2382–2394 (2008)Navarro-Laboulais J., López F., Torregrosa J.I., Cardona S.C., Abad A.: Transient response, model structure and systematic errors in hybrid respirometers: structural identifiabilit analysis based on OUR and DO measurements. J. Math. Chem. 44(4), 969–990 (2007)Patel R., Munro N.: Multivariable Systen. Theory and Design. Pergamon Press, New York (1982)Sondergeld K.: A generalization of the Routh–Hurwitz stability criteria and a application to a problem in robust controller design. IEEE Trans. Automat. Contr. AC-28(10), 965–970 (1983

Ultralow-frequency elastic response in

We present novel low-frequency (0.1\un{Hz}–50\un{Hz}) measurements of the complex elastic susceptibility of \chem{KMn} $_{1-x}$ \chem{Ca} x \chem{F_3} (x=0, 0.003, 0.018). An ultraslow relaxational process in pure \chem{KMnF_3} just below T_{\ab{c}}=186 \un{K} is discovered and explained by a refined heat diffusion model. In addition, a giant softening (superelasticity) due to domain wall motion is found. In contrast to the case of \chem{SrTiO_3} and also of pure \chem{KMnF_3}, we find a ferroelastic domain freezing in the mixed crystals with 0.3% \chem{Ca} substitution. The dispersion displays a Cole-Davidson–like behaviour with an additional logarithmic low-frequency contribution in agreement with the theoretical results for weak pinning of elastic interfaces in crystals with randomly distributed impurities

Nonlinear elastic behaviour of

The ultra-low-frequency (Hz region) elastic behaviour of \ab{SrTiO}_3 has been examined over a wide temperature range including the cubic-tetragonal transition at T_{\ab c}=105\un{K} and the quantum paraelectric region (T < 40\un{K}) using a three-point–bending method. A giant elastic softening has been found in the tetragonal phase. It is explained by a model, which takes into account the motion of ferroelastic domain walls in response to the applied dynamic stress. In the quantum paraelectric regime we have detected nonlinear elastic anomalies in the real and imaginary parts of the complex Young's modulus. Our data can be consistently described if we assume that ferroelectric order is induced by the applied strain gradient, which due to flexoelectric coupling is equivalent to a homogeneous electric field. Below 25 K the induced ordered polarization clusters are frozen on the experimental timescale (11 Hz)