Performance comparison of point and spatial access methods

In the past few years a large number of multidimensional point access methods, also called multiattribute index structures, has been suggested, all of them claiming good performance. Since no performance comparison of these structures under arbitrary (strongly correlated nonuniform, short "ugly") data distributions and under various types of queries has been performed, database researchers and designers were hesitant to use any of these new point access methods. As shown in a recent paper, such point access methods are not only important in traditional database applications. In new applications such as CAD/CIM and geographic or environmental information systems, access methods for spatial objects are needed. As recently shown such access methods are based on point access methods in terms of functionality and performance. Our performance comparison naturally consists of two parts. In part I we w i l l compare multidimensional point access methods, whereas in part I I spatial access methods for rectangles will be compared. In part I we present a survey and classification of existing point access methods. Then we carefully select the following four methods for implementation and performance comparison under seven different data files (distributions) and various types of queries: the 2-level grid file, the BANG file, the hB-tree and a new scheme, called the BUDDY hash tree. We were surprised to see one method to be the clear winner which was the BUDDY hash tree. It exhibits an at least 20 % better average performance than its competitors and is robust under ugly data and queries. In part I I we compare spatial access methods for rectangles. After presenting a survey and classification of existing spatial access methods we carefully selected the following four methods for implementation and performance comparison under six different data files (distributions) and various types of queries: the R-tree, the BANG file, PLOP hashing and the BUDDY hash tree. The result presented two winners: the BANG file and the BUDDY hash tree. This comparison is a first step towards a standardized testbed or benchmark. We offer our data and query files to each designer of a new point or spatial access method such that he can run his implementation in our testbed

Effects of Military-Based Relationships on Spousal Intimacy: An Analysis of PTSD Symptomology

Past research of military families has focused on the effects of war on the domicile unit rather than asking why such effects are present. One of the social support systems that potentially influences the development and course of PTSD is the “Battle Buddy;” a comrade during phases of training and combat. The research question that is most interesting is “How does the presence of a Battle Buddy affect the marital intimacy and support?” The present study asked returning veterans enrolled in central Minnesota college courses to respond to a plethora of surveys inquiring about their Battle Buddy relationships and their intimate relationships. A milieu of statistical tests was used to determine their relationships and to better understand this population and their relationships. The statistical findings did not confirm the author’s original hypotheses. As it pertains to the research question of the present study, it appears that the presence of a Battle Buddy in the life of a veteran as indicated by the results of the multiple-regression models increases a veteran’s intimacy with their partner. The greatest limitation of this study is the small sample size. Future studies should replicate this study with a larger sample size to include more variables in order to further explain the connection between a Battle Buddy and spousal intimacy in the life of a returning veteran

THE KINDERGARTEN BUDDY PROGRAM AND ITS EFFECT ON READING ACHIEVEMENT FOR AT-RISK KINDERGARTEN STUDENTS

Research states that more time and attention is needed for some students to acquire the necessary skills which allow them to become successful learners. Full-day kindergarten programs are desirable to ensure that all students have the necessary time to be successful. Due to lack of funds many school districts are unable to offer full-day kindergarten programs. The Kindergarten Buddy Program is a viable alternative for school systems seeking ways to provide opportunities for students who require extra support. The effectiveness of providing additional instruction in phonological awareness for at-risk learners needs to be explored to determine its impact on reading achievement. This information will be beneficial to school districts as they struggle to meet the needs of at-risk students in a fiscally responsible manner. The purpose of this study was to determine if additional instruction in phonological awareness, the Kindergarten Buddy Program, had an effect on reading achievement for at-risk kindergarten students. Students’ reading achievement was analyzed to see if participation in the Kindergarten Buddy Program enabled them to reach grade level expectations. Using a convenience sample (N = 92), scores on the Gates MacGinitie Reading Test and the Kindergarten Inventory of Skills in the half-day extended Kindergarten Buddy Program were compared to students scores in half-day kindergarten without an extended program and in a ii full-day kindergarten without an extended program. An ANOVA was conducted to determine if there were differences in the post-test scores of the different groups. Differences over time were also analyzed using a repeated measures ANOVA to determine if there was a significant difference in the means of the scores of the three groups as measured by the Inventory of Skills. The study revealed that half-day Buddy students scored significantly higher than half-day kindergarten students on the letter and letter/sound subscores on the Gates MacGinitie. Scores comparing the Buddy Program to a full-day program were similar as were the half-day kindergarten and full-day programs. This suggested the Kindergarten Buddy Program made significant strides in improving letter and letter/sound abilities of the at-risk students and therefore, it was as effective as the full-day program in assisting at-risk students in reaching grade level expectations

Hang With Your Buddies to Resist Intersection Attacks

Some anonymity schemes might in principle protect users from pervasive network surveillance - but only if all messages are independent and unlinkable. Users in practice often need pseudonymity - sending messages intentionally linkable to each other but not to the sender - but pseudonymity in dynamic networks exposes users to intersection attacks. We present Buddies, the first systematic design for intersection attack resistance in practical anonymity systems. Buddies groups users dynamically into buddy sets, controlling message transmission to make buddies within a set behaviorally indistinguishable under traffic analysis. To manage the inevitable tradeoffs between anonymity guarantees and communication responsiveness, Buddies enables users to select independent attack mitigation policies for each pseudonym. Using trace-based simulations and a working prototype, we find that Buddies can guarantee non-trivial anonymity set sizes in realistic chat/microblogging scenarios, for both short-lived and long-lived pseudonyms.Comment: 15 pages, 8 figure

Guarded Motion and Reflexive Behaviors for the Survivor Buddy Robot

This paper summarizes hardware and software changes made to the latest version of the Survivor Buddy, specifically regarding the addition of motor burnout prevention systems and the implementation of behavior tracking and mimicking functionality. The Survivor Buddy is an inexpensive and compact robot platform designed to interact with people as a social actor. Its main applications include search and rescue operations and telemedicine, with potential applications in other areas. Currently, robots in these areas are either very expensive, very large, or do not engage with people as social actors. The updates made to the Survivor Buddy outlined in this paper are designed to increase its ability to accurately model human behavior while allowing it to detect when its behavior-based movements are blocked. To create these changes, functionality from existing libraries was combined with data processing and classification algorithms. The implementation of the reflexive system created a system response time range of 0.5-1 seconds, allowing the robot to quickly detect obstacles. These changes demonstrate the efficacy of techniques designed to support inexpensive hardware, thereby providing proof of the practical feasibility of low-cost and functional social robot platforms