17 resultados para peer-to-peer (P2P) computing

em Digital Commons at Florida International University


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Since the Morris worm was released in 1988, Internet worms continue to be one of top security threats. For example, the Conficker worm infected 9 to 15 million machines in early 2009 and shut down the service of some critical government and medical networks. Moreover, it constructed a massive peer-to-peer (P2P) botnet. Botnets are zombie networks controlled by attackers setting out coordinated attacks. In recent years, botnets have become the number one threat to the Internet. The objective of this research is to characterize spatial-temporal infection structures of Internet worms, and apply the observations to study P2P-based botnets formed by worm infection. First, we infer temporal characteristics of the Internet worm infection structure, i.e., the host infection time and the worm infection sequence, and thus pinpoint patient zero or initially infected hosts. Specifically, we apply statistical estimation techniques on Darknet observations. We show analytically and empirically that our proposed estimators can significantly improve the inference accuracy. Second, we reveal two key spatial characteristics of the Internet worm infection structure, i.e., the number of children and the generation of the underlying tree topology formed by worm infection. Specifically, we apply probabilistic modeling methods and a sequential growth model. We show analytically and empirically that the number of children has asymptotically a geometric distribution with parameter 0.5, and the generation follows closely a Poisson distribution. Finally, we evaluate bot detection strategies and effects of user defenses in P2P-based botnets formed by worm infection. Specifically, we apply the observations of the number of children and demonstrate analytically and empirically that targeted detection that focuses on the nodes with the largest number of children is an efficient way to expose bots. However, we also point out that future botnets may self-stop scanning to weaken targeted detection, without greatly slowing down the speed of worm infection. We then extend the worm spatial infection structure and show empirically that user defenses, e.g. , patching or cleaning, can significantly mitigate the robustness and the effectiveness of P2P-based botnets. To counterattack, we evaluate a simple measure by future botnets that enhances topology robustness through worm re-infection.

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The phenomenonal growth of the Internet has connected us to a vast amount of computation and information resources around the world. However, making use of these resources is difficult due to the unparalleled massiveness, high communication latency, share-nothing architecture and unreliable connection of the Internet. In this dissertation, we present a distributed software agent approach, which brings a new distributed problem-solving paradigm to the Internet computing researches with enhanced client-server scheme, inherent scalability and heterogeneity. Our study discusses the role of a distributed software agent in Internet computing and classifies it into three major categories by the objects it interacts with: computation agent, information agent and interface agent. The discussion of the problem domain and the deployment of the computation agent and the information agent are presented with the analysis, design and implementation of the experimental systems in high performance Internet computing and in scalable Web searching. ^ In the computation agent study, high performance Internet computing can be achieved with our proposed Java massive computation agent (JAM) model. We analyzed the JAM computing scheme and built a brutal force cipher text decryption prototype. In the information agent study, we discuss the scalability problem of the existing Web search engines and designed the approach of Web searching with distributed collaborative index agent. This approach can be used for constructing a more accurate, reusable and scalable solution to deal with the growth of the Web and of the information on the Web. ^ Our research reveals that with the deployment of the distributed software agent in Internet computing, we can have a more cost effective approach to make better use of the gigantic scale network of computation and information resources on the Internet. The case studies in our research show that we are now able to solve many practically hard or previously unsolvable problems caused by the inherent difficulties of Internet computing. ^

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This research presents several components encompassing the scope of the objective of Data Partitioning and Replication Management in Distributed GIS Database. Modern Geographic Information Systems (GIS) databases are often large and complicated. Therefore data partitioning and replication management problems need to be addresses in development of an efficient and scalable solution. ^ Part of the research is to study the patterns of geographical raster data processing and to propose the algorithms to improve availability of such data. These algorithms and approaches are targeting granularity of geographic data objects as well as data partitioning in geographic databases to achieve high data availability and Quality of Service(QoS) considering distributed data delivery and processing. To achieve this goal a dynamic, real-time approach for mosaicking digital images of different temporal and spatial characteristics into tiles is proposed. This dynamic approach reuses digital images upon demand and generates mosaicked tiles only for the required region according to user's requirements such as resolution, temporal range, and target bands to reduce redundancy in storage and to utilize available computing and storage resources more efficiently. ^ Another part of the research pursued methods for efficient acquiring of GIS data from external heterogeneous databases and Web services as well as end-user GIS data delivery enhancements, automation and 3D virtual reality presentation. ^ There are vast numbers of computing, network, and storage resources idling or not fully utilized available on the Internet. Proposed "Crawling Distributed Operating System "(CDOS) approach employs such resources and creates benefits for the hosts that lend their CPU, network, and storage resources to be used in GIS database context. ^ The results of this dissertation demonstrate effective ways to develop a highly scalable GIS database. The approach developed in this dissertation has resulted in creation of TerraFly GIS database that is used by US government, researchers, and general public to facilitate Web access to remotely-sensed imagery and GIS vector information. ^

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This is a study of a peer support program to aid students in secondary school struggling to learn a second language (for college entrance requirements) who have Asperger Syndrone and primary language deficits.

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The purpose of this study was to examine the effectiveness of peer counseling on high school students who have previously failed two or more classes in a nine week quarter.^ This study was constructed by comparing students who previously failed and were subsequently given peer counseling with a matched group of students who failed and did not receive peer counseling.^ To test the proposed research question, 324 students from a large urban school system were randomly chosen from a computer generated list of students who failed courses, matched on variables of number of classes failed, grade level and gender. One student from each matched pair was randomly placed in either the experimental or control group. 162 students from Group 1 (experimental) were assigned a peer counselor with their pair assigned to Group 2 (control). Group 1 received peer counseling at least 4 times during the third nine week academic quarter (Quarter 3) while Group 2 did not.^ The Grade Point Averages (GPA) for all students were collected both at the end of Quarter 2 and Quarter 3, at which time peer counseling was terminated. GPA's were also collected nine weeks after counseling was terminated.^ Results were determined by multiple regression, analysis of covariance and t-test. A level of significance was set at.05. There was significant increase in the GPA's of those counseled students immediately after peer counseling and also nine weeks after counseling was terminated, while the group not receiving peer counseling showed no increase. It was noted that there were significantly more school drop-outs from the non-counseled group than the counseled group. The number of classes failed, high school attended, grade level and gender were not found to be significant.^ The conclusion from this study was that peer counseling does impact significantly on the GPA's of students experiencing academic failure. Recommendations from this study were to implement and expand peer counseling programs with more failing students, continue counseling for longer than one quarter, include students in drop-out programs and students from different socio-economic and racial backgrounds, and conduct subsequent evaluation. ^

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The current study examined the influence of weak parental and peer attachment on academic achievement among late adolescent college students. In previous research, weak attachment to parents and/or peers had been found to have an adverse influence on the academic success of college students. This study also examined the potential moderating influence of several cognitive and non-cognitive psychosocial variables that might act as protective factors for weakly attached students and, therefore, enhance their academic competence. Data regarding attachment, cognitive variables, and non-cognitive variables were collected using several self-report measures. The multi-ethnic sample of students in this study (n = 357) attended an urban university. Students were classified into one of nine parental-peer attachment groups (e.g., Low-Low, Medium-Medium, High-High). Attachment groups were compared in terms of cognitive and non-cognitive variables. Contrary to the hypothesis, no statistically significant academic achievement differences were revealed for the group of college students who perceived themselves to be weakly attached to both parents and peers. Analysis of variance (ANOVA) identified the High-High group to be significantly different in terms of academic outcome variables from the other eight groups while the Low-Low group had significantly lower levels of non-cognitive variables than several of the other attachment groups. Hierarchical multiple regression analyses revealed that cognitive variables accounted for significant amounts of variance in academic outcomes and that several non-cognitive variables were significant predictors of scholastic competence. Correlational analyses revealed that parental and peer attachment were positively correlated with several cognitive and non-cognitive variables but neither was significantly correlated with self-reported college GPA. In general, the findings do not provide support for a main effect of weak attachment to parents and peers upon academic adversity among college students. Results suggest that both cognitive variables and non-cognitive variables may moderate academic risk due to weak attachment to parents and peers. Descriptive within group analyses of the Low-Low group revealed a heterogeneous group of students with regards to academic outcomes and scores on non-cognitive measures. Gender and ethnic differences were found for attachment status but not for cognitive or non-cognitive variables. Implications for interventions and suggestions for future research are presented. ^

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This dissertation investigated the effects of a peer coaching relationship between a special education teacher and two general education teachers. More specifically, a two-tier multiple baseline design across subjects was used to evaluate the effects of peer coaching on the general education teachers' use of effective instructional practices (EIPs) and subsequent effects on the engagement rate and academic performance of students with and without disabilities. The peer coaching process included modeling, direct support, and feedback on the use of effective instructional practices including getting student attention, giving specific directions, asking specific questions with wait time, contingent positive reinforcement, positive error correction, precorrection, prompting, and proximity control. A 30-second partial interval recording procedure was used to observe the general education teachers' use of effective instructional practices and student engagement rates. Student participants' academic performance was measured using weekly quizzes. ^ Peer coaching resulted in an overall increase in the teachers' use of EIPs. One general education teacher had a 30% increase in average EIP use from 46% during the baseline phase to 76% during intervention. Student engagement for her two student participants with and without disabilities indicated an increase from 54% to 69% and from 47% to 65% respectively. Results for the second general education teacher indicated a 34% increase in average EIP use from 55% during the baseline to 89% during intervention. Student engagement for the two student participants with and without disabilities in her class increased from 48% to 83% and from 29% to 71% respectively. Student academic performance showed a small increase. In follow-up observations, the effects of peer coaching on teacher use of EIPs and student engagement and academic performance were maintained. ^ The results of this study suggest that using peer coaching to support general education teachers can be an effective method to improve the educational outcomes of students with and without disabilities in general education. Further research is needed to investigate the effects of peer coaching with other special and general educator partnerships and other student participants. ^

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Despite a long history of prevention efforts and federal laws prohibiting the consumption of alcohol for those below the age of 21 years, underage drinking continues at both a high prevalence rate and high incidence rate. The purpose of this research study is to explain underage drinking of alcohol conditioned by perception of peer drinking. An acquisition model is conjectured and then a relationship within the model is explained with a national sample of students. From a developmental perspective, drinking alcohol is acquired in a reasonably ordered fashion that reflects the influences over time of the culture, family, and peers. The study measures perceptions of alcohol drinking during early adolescence when alcohol use begins the maintenance phase of the behavior. The correlation between drinking alcohol and perception of classmate drinking can be described via social learning theory. Simultaneously the moderating effects of grade level, gender, and race/ethnicity are used to explain differences between groups. Multilevel logistic regression was used to analyze the relations. The researcher found support for an association between adolescent drinking and perceptions of classmate drinking. Gender and grade level moderated the relation. African-Americans consistently demonstrated less drinking and less perception of classmate drinking than either whites or other students not white nor African-American. The importance of a better understanding of the process of acquiring drinking behaviors is discussed in relation to future research models with longitudinal data. ^

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Approximately 200 million people, 5% aged 15-64 worldwide are illicit drug or substance abusers (World Drug Report, 2006). Between 2002 and 2005, an average of 8.2% of 12 year olds and older in the Miami, Fort Lauderdale metropolitan areas used illicit drugs (SAMHSA, 2007). Eight percent of pregnant women, aged 15 to 25, were more likely to have used illicit drugs during pregnancy than pregnant women aged 26 to 44. Alcohol use was 9.8% and cigarette use was 18% for pregnant women aged 15 to 44 (SAMHSA, 2005). Approximately a quarter of annual birth defects are attributed to the exposure of drugs or substance abuse in utero (General Accounting Office, 1991). Physical, psychological and emotional challenges may be present for the illicit drug/substance abuse (ID/SA) mother and infant placing them at a disadvantage early in their relationship (Shonkoff & Marshall, 1990). Mothers with low self efficacy have insecurely attached infants (Donovan, Leavitt, & Walsh, 1987). As the ID/SA mother struggles with wanting to be a good parent, education is needed to help her care for her infant. In this experimental study residential rehabilitating ID/SA mothers peer taught infant massage. Massage builds bonding/attachment between mother and infant (Reese & Storm, 2008) and peer teaching is effective because participants have faced similar challenges and speak the same language (Boud, Cohen, & Sampson 2001). Quantitative data were collected using the General Self-Efficacy and Maternal Attachment Inventory-Revised Scale before and after the 4-week intervention program. A reported result of this study was that empowering ID/SA mothers increased their self-efficacy, which in turn allowed the mothers to tackle challenges encountered and created feelings of being a fit mother to their infants. This research contributes to the existing database promoting evidence-based practice in drug rehabilitation centers. Healthcare personnel, such as nurse educators and maternal-child health practitioners, can develop programs in drug rehabilitation centers that cultivate an environment where the ID/SA rehabilitating mothers can peer teach each other, while creating a support system. Using infant massage as a therapeutic tool can develop a healthy infant and nurture a more positive relationship between mother and infant.

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Phobic and anxiety disorders are one of the most common, if not the most common and debilitating psychopathological conditions found among children and adolescents. As a result, a treatment research literature has accumulated showing the efficacy of cognitive behavioral treatment (CBT) for reducing anxiety disorders in youth. This dissertation study compared a CBT with parent and child (i.e., PCBT) and child group CBT (i.e., GCBT). These two treatment approaches were compared due to the recognition that a child’s context has an effect on the development, course, and outcome of childhood psychopathology and functional status. The specific aims of this dissertation were to examine treatment specificity and mediation effects of parent and peer contextual variables. The sample consisted of 183 youth and their mothers. Research questions were analyzed using analysis of variance for treatment outcome, and structural equation modeling, accounting for clustering effects, for treatment specificity and mediation effects. Results indicated that both PCBT and GCBT produced positive treatment outcomes across all indices of change (i.e., clinically significant improvement, anxiety symptom reduction) and across all informants (i.e., youths and parents) with no significant differences between treatment conditions. Results also showed partial treatment specific effects of positive peer relationships in GCBT. PCBT also showed partial treatment specific effects of parental psychological control. Mediation effects were only observed in GCBT; positive peer interactions mediated treatment response. The results support the use CBT with parents and peers for treating childhood anxiety. The findings’ implications are further discussed in terms of the need to conduct further meditational treatment outcome designs in order to continue to advance theory and research in child and anxiety treatment.

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This study examined peer relationships and psychosocial functioning as a function of maternal and paternal involvement and nurturance along with the moderating effects of gender, family form, and ethnicity. Prior research has shown the influence of mother’s involvement on peer relationship quality but not of fathers. Further, previous studies did not examine moderation by family form, gender, or ethnicity. The sample consisted of 1359 students who identified their biological mother and father as the most influential parental figures in their lives. Their ages ranged from 18 to 26; Sixty-one percent of the sample was Hispanic, 13% non-Hispanic Black, 25% non-Hispanic White; 76% female and 70% from intact families. The analytical strategy included using bivariate correlations and structural equation modeling to examine these relationships. ^ All dimensions of maternal and paternal nurturing and involvement were positively related to positive characteristics of peer relationships, self-esteem and life satisfaction consistent with the multicultural findings of PARTheory (Rohner, Khalique, & Cournoyer, 2005). A structural model was developed that was able to adequately account for the relationship between parental influence, peer relationships, and psychosocial functioning. These effects of both maternal and paternal influence were strongly moderated by culture, family form, and gender. Finally, a differential effect was found among parental influence with fathers having a greater influence on friendship quality and importance than mothers, despite greater maternal involvement. ^ These findings have theoretical, clinical, and social implications as they call for a socially based theoretical perspective within which to study these relationships. Such a perspective would better inform clinicians when using impaired social functioning as indicative of axial diagnosis, and for the implementation of social policy to encourage paternal involvement. ^

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The purpose of this study was to investigate the effects of cross-age peer writing response groups on the writing and reading achievement of third and fourth grade students. Students' attitudes about writing and their perceptions of themselves as writers were also measured at the end of the study. ^ One hundred and twenty-two third and fourth grade students enrolled in a public school in a middle-class, multi-cultural neighborhood participated in the study. Four existing classes of students were randomly assigned to either the experimental condition (EC) or the control condition (CC). Both groups were pretested and posttested for writing and reading achievement. The intervention, cross-age peer writing groups, met for eleven weeks. ^ Three hypotheses were examined in this study: (a) writing improvement score, (b) reading comprehension improvement score, and (c) students' attitudes toward writing and their perception of themselves as writers based on the five scales measured on the Writer Self-Perception Scale. ^ ANOVAs were done on the pretests and posttests for writing and the Stanford Achievement Test reading comprehension subtest scores for the year of the study and the previous year. ANOVAs were also done for the five areas of the Writer Self-Perception Scale. Cross-tabulations were also used to compare improvement level verses treatment group, and grade level. ^ Analysis of the data revealed that there was no evidence that the tutoring (EC) groups made more progress than the non-tutoring (CC) groups in writing and reading. There was evidence of growth in writing, especially by the fourth graders. Most importantly, the fourth grade tutors, the experimental group, had the most positive feelings about writing and themselves as writers. ^

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The current study was designed to explore the salience of parent and peer support in middle childhood and early adolescence across two time periods as indicated by measures of achievement (grade point average (GPA), Stanford Achievement Test (SAT) scores and teacher rated school adaptation) and well-being (loneliness, depression, self-concept and teacher-rated internalizing behaviors). ^ Participants were part of an initial study on social network relations and school adaptation in middle childhood and early adolescence. Participants at Time 1 (in the spring of 1997) included 782 children in grades 4 and 6 of eight lower and middle income public elementary schools. Participants (N = 694) were reinterviewed two years later in the spring of 1999 (Time 2). ^ Multivariate analyses of variance (MANOVA) were used to investigate the change in salience of parent and peer support from Time 1 to Time 2. In addition, Tukey-HSD (Honestly Significant Difference) post hoc tests were used to test the significance of the differences among the means of four support categories: (1) low parent-low friend, (2) low parent-high friend, (3) high parent-low friend, and (4) high parent-high friend. ^ Compensatory effects were observed for loneliness and self-concept at Time 1, as well as for SAT scores, self-concept and overall achievement at Time 2. Results were consistent with existing findings that suggest a competitive model of parent/peer influence on achievement during adolescence. This study affirms the need for a more contextual approach to research examining competing and compensatory effects on adolescent development. ^

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The current study aims to discover the effects of “Food Dudes” peer modeling videos and positive reinforcement on vegetable consumption using a delayed multiple baseline design across subjects. Results suggest peer modeling and positive reinforcement as effective means to increase vegetable intake.

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Approximately 200 million people, 5% aged 15-64 worldwide are illicit drug or substance abusers (World Drug Report, 2006). Between 2002 and 2005, an average of 8.2% of 12 year olds and older in the Miami, Fort Lauderdale metropolitan areas used illicit drugs (SAMHSA, 2007). Eight percent of pregnant women, aged 15 to 25, were more likely to have used illicit drugs during pregnancy than pregnant women aged 26 to 44. Alcohol use was 9.8% and cigarette use was 18% for pregnant women aged 15 to 44 (SAMHSA, 2005). Approximately a quarter of annual birth defects are attributed to the exposure of drugs or substance abuse in utero (General Accounting Office, 1991). Physical, psychological and emotional challenges may be present for the illicit drug/substance abuse (ID/SA) mother and infant placing them at a disadvantage early in their relationship (Shonkoff & Marshall, 1990). Mothers with low self efficacy have insecurely attached infants (Donovan, Leavitt, & Walsh, 1987). As the ID/SA mother struggles with wanting to be a good parent, education is needed to help her care for her infant. In this experimental study residential rehabilitating ID/SA mothers peer taught infant massage. Massage builds bonding/attachment between mother and infant (Reese & Storm, 2008) and peer teaching is effective because participants have faced similar challenges and speak the same language (Boud, Cohen, & Sampson 2001). Quantitative data were collected using the General Self-Efficacy and Maternal Attachment Inventory-Revised Scale before and after the 4-week intervention program. A reported result of this study was that empowering ID/SA mothers increased their self-efficacy, which in turn allowed the mothers to tackle challenges encountered and created feelings of being a fit mother to their infants. This research contributes to the existing database promoting evidence-based practice in drug rehabilitation centers. Healthcare personnel, such as nurse educators and maternal-child health practitioners, can develop programs in drug rehabilitation centers that cultivate an environment where the ID/SA rehabilitating mothers can peer teach each other, while creating a support system. Using infant massage as a therapeutic tool can develop a healthy infant and nurture a more positive relationship between mother and infant.