L^2-Theory for non-symmetric Ornstein-Uhlenbeck semigroups on domains

We present some new results on analytic Ornstein-Uhlenbeck semigroups and use them to extend recent work of Da Prato and Lunardi for Ornstein-Uhlenbeck semigroups on open domains O to the non-symmetric case. Denoting the generator of the semigroup by L_O, we obtain sufficient conditions in order that the domain Dom(\sqrt{-L_O}) be a first order Sobolev space.Comment: 23 pages, revised version, to appear in J. Evol. Eq. The main change is a correction in Theorem 5.5: the second assertion has been withdrawn due to a gap in the original proo

On the Complexity of the Highway Pricing Problem

The highway pricing problem asks for prices to be determined for segments of a single highway such as to maximize the revenue obtainable from a given set of customers with known valuations. The problem is (weakly) NP-hard and a recent quasi-PTAS suggests that a PTAS might be in reach. Yet, so far it has resisted any attempt for constant-factor approximation algorithms. We relate the tractability of the problem to structural properties of customers' valuations. We show that the problem becomes NP-hard as soon as the average valuations of customers are not homogeneous, even under further restrictions such as monotonicity. Moreover, we derive an efficient approximation algorithm, parameterized along the inhomogeneity of customers' valuations. Finally, we discuss extensions of our results that go beyond the highway pricing problem.\u

The effect of income on commuting time - an analysis based on panel data

Although urban economics theory predicts that households with higher incomes have different commuting time patterns than low income households, the direction of the effect is ambiguous. From a “value of time” perspective, one can argue that high income households may have shorter commuting times because their time is more precious; thus they choose to live closer to the job and are willing to pay for faster modes of travel. However, it can alternatively be argued that they may have longer commuting times, because they desire and can afford more living space and a higher quality of housing than is available or affordable in closer proximity to employment centres. Empirical testing of these alternative hypotheses is not straight forward because income, itself, is determined by commuting time as workers are willing to travel further for higher wages. This reverse causation must be taken into account in the estimation, but this is often problematic due to a lack of good control variables. In the current paper, we employ panel data to overcome these problems. To deal with reversed causation we only select workers who did not change workplace location during the period. For these workers, changes in commuting time resulting from an income change come about either through a change in residential location or a change in travel mode. In addition, by estimating the effect of annual income changes on commuting time changes, the necessity of good control variables is avoided.

Biofeedback systems for stress reduction: Towards a Bright Future for a Revitalized Field

Stress has recently been baptized as the black death of the 21st century, which illustrates its threat to current health standards. This article proposes biofeedback systems as a means to reduce stress. A concise state-ofthe-art introduction on biofeedback systems is given. The field of mental health informatics is introduced. A compact state-of-the-art introduction on stress (reduction) is provided. A pragmatic solution for the pressing societal problem of illness due to chronic stress is provided in terms of closed loop biofeedback systems. A concise set of such biofeedback systems for stress reduction is presented. We end with the identification of several development phases and ethical concerns

Watch out for the preview: The effects of a preview on the usability of a Content Management System and on the user's confidence level

As time moves on, a trend crystallizes that sets new requirements on content management systems. The circle of users shifts from a small technically experienced group to a large network of inexperienced editors. Literature stresses that a higher need for usability is present if personnel with a low grade of human computer interaction expertise is using a system. But how can system designers accomplish a high level of usability? This study suggests a preview as an important factor for strengthening the usability (effectiveness, efficiency and satisfaction) of a content management system. The findings of this study support the hypothesis: the results showed that a preview enhances the userspsila satisfaction with the system. Moreover, the study shows that the userspsila confidence to be able to work with the system is an important factor; the results showed positive correlations between confidence and satisfaction and between confidence and effectiveness

Accessible Website Content Guidelines for Users with Intellectual Disabilities

Background: The W3C Web Accessibility Initiative has issued guidelines for making websites better and easier to access for people with various disabilities (W3C Web Accessibility Initiative guidelines 1999). - \ud Method: The usability of two versions of a website (a non-adapted site and a site that was adapted on the basis of easy-to-read guidelines) was tested with two groups of 20 participants. One group had intellectual disabilities but could read, the other group had no identified intellectual disabilities. In a 2 × 2 experimental design, it was investigated whether the easy-to-read website was indeed better accessible and usable for the participants with intellectual disabilities. - \ud Results: The adaptation of the website worked well for participants with intellectual disabilities. Users without identified intellectual disabilities were as effective with the adapted site as they were with the non-adapted site. - \ud Conclusion: The results form an empirical basis for recommendations about applying guidelines for easy-to-read text on websites for people with intellectual disabilities

Price Strategy Implementation

Consider a situation in which a company sells several different items to a set of customers. However, the company is not satisfied with the current pricing strategy and wishes to implement new prices for the items. Implementing these new prices in one single step mightnot be desirable, for example, because of the change in contract prices for the customers. Therefore, the company changes the prices gradually, such that the prices charged to a subset of the customers, the target market, do not differ too much from one period to the next. We propose a polynomial time algorithm to implement the new prices in the minimum number of time periods needed, given that the prices charged to the customers in the target market increase by at most a factor 1 + δ, for predetermined δ > 0. Furthermore, we address the problem to maximize the revenue when also a maximum number of time periods is predetermined. For this problem, we describe a dynamic program if the numberof possible prices is limited, and a local search algorithm if all prices are allowed. Also, we present the integer program that models this problem. Finally, we apply the obtained algorithms in a practical study.operations research and management science;

On the Complexity of the Highway Pricing Problem

The highway pricing problem asks for prices to be determined for segments of a single highway such as to maximize the revenue obtainable from a given set of customers with known valuations. The problem is (weakly) NP-hard and a recent quasi-PTAS suggests that a PTAS might be in reach. Yet, so far it has resisted any attempt for constant-factor approximation algorithms. We relate the tractability of the problem to structural properties of customers'' valuations. We show that the problem becomes NP-hard as soon as the average valuations of customers are not homogeneous, even under further restrictions such as monotonicity. Moreover, we derive an efficient approximation algorithm, parameterized along the inhomogeneity of customers'' valuations. Finally, we discuss extensions of our results that go beyond the highway pricing problem.operations research and management science;

Elevated central serotonin levels inhibit emotional crying

Previous research has suggested a possible role of serotonin in emotional expressions, such as crying. We have found that a transient increase of central serotonin levels by means of oral administration of paroxetine reduces crying in response to emotional movies in healthy female volunteers. This is the first direct evidence of an important role of serotonin in this uniquely human emotional response

Come, see and experience affective interactive art

The progress in the field of affective computing enables the realization of affective consumer products, affective games, and affective art. This paper describes the affective interactive art system Mood Swings, which interprets and visualizes affect expressed by a person. Mood Swings is founded on the integration of a framework for affective movements and a color model. This enables Mood Swings to recognize affective movement characteristics as expressed by a person and display a color that matches the expressed emotion. With that, a unique interactive system is introduced, which can be considered as art, a game, or a combination of both