On dynamic computational subgrid modeling

In this paper we study a subgrid model based on extrapolation of a corrective force, in the case of a linear convection-diffusion problem $Lu=f$ in one dimension. The running average $u^{h}$ of the exact solution $u$ on the finest computational scale $h$ satisfies an equation $L_{h}u^{h}=[f]^{h}+F_{h}$, where $L_{h}$ is the operator used in the computation on the scale $h$, $[f]^{h}$ is the approximation of $f$ on the scale $h$, and $F_{h}$ acts as a corrective force, which needs to be modeled. The subgrid modeling problem is to compute approximations of $F_{h}$ without using finer scales than $h$. In this study we model $F_{h}$ by extrapolation from coarser scales than $h$ where the corrective force is directly computed with the finest scale $h$ as reference. We show in experiments that a corrected solution with subgrid model on scale $h$ corresponds to a non-corrected solution on less than $h/4$

The Nature and Methodological Implications of the Cognitive Representation of Products

A general relationship is proposed wherein more abstract attributes are likely to resemble continuous dimensions while more concrete attributes are likely to resemble dichotomous features. While some methodologies assume dimensional representations, others assume feature-based representations. This suggests that dimensional methods may better capture abstract product representations while feature-based methods may better capture concrete representations. The results of two studies that support both the general relationship and its methodological implications are reported

Explicit Time-Stepping for Stiff ODEs

We present a new strategy for solving stiff ODEs with explicit methods. By adaptively taking a small number of stabilizing small explicit time steps when necessary, a stiff ODE system can be stabilized enough to allow for time steps much larger than what is indicated by classical stability analysis. For many stiff problems the cost of the stabilizing small time steps is small, so the improvement is large. We illustrate the technique on a number of well-known stiff test problems

A framework for comparing customer satisfaction across individuals and product categories

A framework is presented which integrates economic and psychological perspectives in order to compare customer satisfaction across individuals and product categories. The framework lays the foundation for the development of a national index for customer satisfaction that is now in place in Sweden. An important property of any such index is that it allows for comparisons across customers, firms, and industries. A number of propositions are forwarded regarding potentially systematic differences in satisfaction across people and products.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29302/1/0000365.pd

Differentiation as a basis for explaining customer satisfaction across industries

The paper uses the differentiation of offerings as a basis for explaining differences in aggregate, industry level customer satisfaction in the annual Swedish Customer Satisfaction Barometer. The results reveal that differentiated industries have higher aggregate levels of perceived performance and subsequent customer satisfaction, and that a large portion of variance in customer satisfaction across industries can be explained by the impact of differentiation (via perceived performance). These findings suggest that it is indeed possible to make meaningful comparisons of customer satisfaction across different industries.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30423/1/0000044.pd

Computational Modeling of Dynamical Systems

In this short note, we discuss the basic approach to computational modeling of dynamical systems. If a dynamical system contains multiple time scales, ranging from very fast to slow, computational solution of the dynamical system can be very costly. By resolving the fast time scales in a short time simulation, a model for the effect of the small time scale variation on large time scales can be determined, making solution possible on a long time interval. This process of computational modeling can be completely automated. Two examples are presented, including a simple model problem oscillating at a time scale of 1e-9 computed over the time interval [0,100], and a lattice consisting of large and small point masses

The American Customer Satisfaction Index: Nature, Purpose, and Findings

The American Customer Satisfaction Index (ACSI) is a new type of market-based performance measure for firms, industries, economic sectors, and national economies. The authors discuss the nature and purpose of ACSI and explain the theory underlying the ACSI model, the nation-wide survey methodology used to collect the data, and the econometric approach employed to estimate the indices. They also illustrate the use of ACSI in conducting benchmarking studies, both cross-sectionally and over time. The authors find customer satisfaction to be greater for goods than for services and, in turn, greater for services than for government agencies, as well as find cause for concern in the observation that customer satisfaction in the United States is declining, primarily because of decreasing satisfaction with services. The authors estimate the model for the seven major economic sectors for which data are collected. Highlights of the findings include that (1) customization is more important than reliability in determining customer satisfaction, (2) customer expectations play a greater role in sectors in which variance in production and consumption is relatively low, and (3) customer satisfaction is more quality-driven than value- or price-driven. The authors conclude with a discussion of the implications of ACSI for public policymakers, managers, consumers, and marketing in general

An open prospective study evaluating efficacy and safety of a new medical device for rectal application of activated carbon in the treatment of chronic, uncomplicated perianal fistulas

Purpose: It has been proposed that biological/chemical substances in the intestine might play a role in the occurrence and deterioration of perianal fistulas. Elimination of such unidentified factors from the lower gastrointestinal tract might offer a new strategy for the management of anal fistulas. The aim of this study was to evaluate the clinical effects on non-Crohn’s disease perianal fistula healing, and the safety and tolerability of a new medical device that applies high-purity, high-activity granular activated carbon locally into the rectum twice daily of patients with perianal fistulas without any concomitant medication. Methods: An open, single-arm, prospective study with active treatment for 8 weeks and an optional follow-up until week 24 (ClinicalTrial.govidentifier NCT01462747) among patients with chronic, uncomplicated perianal fistulas scheduled for surgery was conducted. Results: Of 28 patients included, 10 patients (35.7%) showed complete fistula healing (closed, no discharge on palpation) after 8 weeks; seven of these patients, corresponding to 25% of the enrolled patients, remained in remission for up to 31 weeks. At week 8, there was a statistically significant reduction in the discharge visual analog scale (p = 0.04), a significant improvement in the patient-perceived quality of life for the category of embarrassment (p = 0.002), and a trend toward improvement in the other assessment categories. Conclusions: The treatment was well tolerated, and patient acceptance was high. The results support the efficacy and safety of locally administered activated carbon for the treatment of patients with chronic uncomplicated perianal fistulas not receiving any other medication for fistula problems

Attribute abstraction, feature-dimensionality, and the scaling of product similarities

This paper examines the attributes that consumers use when making product similarity judgments and their effect on similarity scaling. Previous research suggests that concrete brands are judged using dichotomous features while more abstract product categories are judged using continuous dimensions. This, in turn, suggests that the appropriateness of spatial scaling increases relative to tree scaling as one moves from brands to product categories. The results of two studies support an increase in the fit of spaces relative to trees from brands to categories. However, the abstractness of the judgments appears to be driving the effect, not the use of features or dimensions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30067/1/0000437.pd