Updating and Querying Databases that Track Mobile Units

In this paper, we consider databases representing information about moving objects (e.g., vehicles), particularly their location. We address the problems of updating and querying such databases. Specifically, the update problem is to determine when the location of a moving object in the database (namely its database location) should be updated. We answer this question by proposing an information cost model that captures uncertainty, deviation, and communication. Then we analyze dead-reckoning policies, namely policies that update the database location whenever the distance between the actual location and the database location exceeds a given threshold, x. Dead-reckoning is the prevalent approach in military applications, and our cost model enables us to determine the threshold x. We propose several dead-reckoning policies and we compare their performance by simulation.Then we consider the problem of processing range queries in the database. An example of a range query is 'retrieve the objects that are currently inside a given polygon P. We propose a probabilistic approach to solve the problem. Namely, the DBMS will answer such a query with a set of objects, each of which is associated with a probability that the object is inside P.     

Career development patterns of college women.

Ss were 306 women who had been college students in the mid-thirties and who had been studied 25 yrs later and reported on by D. P. Campbell (1965). They were assigned to 5 vocational pattern groups on the basis of their work histories. Of 29 characteristics that were analyzed statistically, 15 significantly discriminated among the 5 groups. A woman's career pattern could not be predicted from data available at the time she entered college but was predictable from other data known 5 yrs later. The most significant data were related to marital situation and education. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatio-temporal data reduction with deterministic error bounds

A common way of storing spatio-temporal information about mobile devices is in the form of a 3D (2D geography + time) trajectory. We argue that when cellular phones and Personal Digital Assistants become location-aware, the size of the spatio-temporal information generated may prohibit efficient processing. We propose to adopt a technique studied in computer graphics, namely line-simplification, as an approximation technique to solve this problem. Line simplification will reduce the size of the trajectories. Line simplification uses a distance function in producing the trajectory approximation. We postulate the desiderata for such a distance-function: it should be sound, namely the error of the answers to spatio-temporal queries must be bounded. We analyze several distance functions, and prove that some are sound in this sense for some types of queries, while others are not. A distance function that is sound for all common spatio-temporal query types is introduced and analyzed. Then we propose an aging mechanism which gradually shrinks the size of the trajectories as time progresses. We also propose to adopt existing linguistic constructs to manage the uncertainty introduced by the trajectory approximation. Finally, we analyze experimentally the effectiveness of line-simplification in reducing the size of a trajectories database. This research is supported by NSF Grants 0326284, 0330342, ITR-0086144, 0513736, 0209190, and partly supported by the NSF grant IIS-0325144/003 and the Northrop-Grumman Corp. grant PO 8200082518.     

Effects of resistive and balance exercises on isokinetic strength in older persons

OBJECTIVE: To determine the safety and efficacy of 3 months of resistive training of multiple lower extremity muscle groups compared with balance training in persons over 75 years. DESIGN: Randomized 3-month clinical trial. Subjects (n = 110, mean age 80) were randomized to 4 groups in a 2 x 2 design (control, resistive, balance, combined resistive/balance). INTERVENTIONS: Resistive training involved knee extension and flexion, hip abduction and extension, and plantar and dorsiflexion using simple resistive machines and sandbags. Balance training consisted of exercises to improve postural control. The control group attended 5 health-related discussion sessions. MEASUREMENTS: Summed isokinetic moments (N m) of 8 leg movements: hip, knee and ankle flexion/extension, and hip abduction/adduction. Secondary outcomes were gait velocity and chair rise time. MAIN RESULTS: Summed peak moment increased in both resistive exercise-trained groups (13% increase in the resistive group and 21% in the combined training group, P < 0.001). The effect of resistance training was significant (MANOVA F = 21.1, P < 0.001), but balance training did not improve strength, and there was no interaction (positive or negative) between balance and resistive training. Maximal gait velocity and chair rise time did not improve. Eleven subjects (20%) had musculoskeletal complaints related to resistive training, but all were able to complete the program with modifications. CONCLUSION: Resistive training using simple equipment is an effective and acceptable method to increase overall leg strength in older persons. Resistive or balance training did not improve maximal gait velocity or chair rise time in this sample of relatively healthy older persons.     

Some effects of position on opinion survey items.

Tested the effect of putting opinion survey items in different positions in a questionnnaire. Equivalent samples of 284 and 281 employees in an industrial corporation completed similar questionnaires in which the placement of 46 Likert-type items were reversed. Respondents answered with less extreme responses and were slightly more likely to omit replies when items were placed later in the questionnaire. Findings suggest that comparisons of responses to identical items used in different surveys may be misleading if they appeared in different position or context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Helplessness in children of depressed and nondepressed mothers.

Helpless behaviors in 5- to 7-year-old children of depressed and nondepressed mothers were assessed through direct observation, interviews, and teacher ratings. The affective tone the mothers set in a joint puzzle task and their tendency to encourage mastery or become intrusive when their children became frustrated at the task were also assessed. Although depressed mothers set a more negative affective tone than nondepressed mothers during solvable puzzles, there were few significant differences between the 2 groups of mothers and children. Still, mothers who were more negative and hostile and less able to encourage mastery in their children had children who exhibited more helpless behaviors in the puzzle task, who were less likely to endorse active problem-solving approaches to frustrating situations, and whose teachers rated the children as less competent and more prone to helpless behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)