This dissertation presents algorithms for data structures called distributed hash tables (DHT) or structured overlay networks, which are used to build scalable self-managing distributed systems. The provided algorithms guarantee lookup consistency in the presence of dynamism: they guarantee consistent lookup results in the presence of nodes joining and leaving. Similarly, the algorithms guarantee that routing never fails while nodes join and leave. Previous algorithms for lookup consistency either suffer from starvation, do not work in the presence of failures, or lack proof of correctness. Several group communication algorithms for structured overlay networks are presented. We provide an overlay broadcast algorithm, which unlike previous algorithms avoids redundant messages, reaching all nodes in O(log n) time, while using O(n) messages, where n is the number of nodes in the system. The broadcast algorithm is used to build overlay multicast. We introduce bulk operation, which enables a node to efficiently make multiple lookups or send a message to all nodes in a specified set of identifiers. The algorithm ensures that all specified nodes are reached in O(log n) time, sending maximum O(log n) messages per node, regardless of the input size of the bulk operation. Moreover, the algorithm avoids sending redundant messages. Previous approaches required multiple lookups, which consume more messages and can render the initiator a bottleneck. Our algorithms are used in DHT-based storage systems, where nodes can do thousands of lookups to fetch large files. We use the bulk operation algorithm to construct a pseudo-reliable broadcast algorithm. Bulk operations can also be used to implement efficient range queries. Finally, we describe a novel way to place replicas in a DHT, called symmetric replication, that enables parallel recursive lookups. Parallel lookups are known to reduce latencies. However, costly iterative lookups have previously been used to do parallel lookups. Moreover, joins or leaves only require exchanging O(1) messages, while other schemes require at least log(f) messages for a replication degree of f. The algorithms have been implemented in a middleware called the Distributed k-ary System (DKS), which is briefly described. / QC 20100824

The American Cancer Society estimates nearly 1.5 million Americans will be diagnosed with cancer this year. Existing on cancer and its effects on family communication indicate there are few things that have the potential to shake a family to its core like a serious illness (Anderson & Geist Martin, 2003; Gotcher, 1993; Northouse, 2005; Sherman & Simonton, 2001). Communication is one of the most important elements in determining and influencing families' emotions, patients' quality of life, patient care, family relationships and caregiver stress (Beach, 2001). The mother-daughter dyad represents one of the most significant relationships to analyze with respect to the impact cancer has within the family since mothers are typically the primary role models for their daughters (Miller, 1995). Using interviews with mother/daughter dyads, this study seeks to examine changes in communication between mothers and daughters following the mother's cancer diagnosis. The mother-daughter dyad is of most interest in this study for several reasons, most notably that this relationship is the “first dyadic relationship a female child has” (Bishop, 1992, p. 58); additionally, mothers are typically the primary role models for their daughters (Miller, 1995). This study aims to shed light on the relational changes that occur following a cancer diagnosis.

In this thesis, we propose an adaptive multicast key management scheme for secure group communications. In a secure communication session, group members could dynamically join and leave the group. Therefore, a multicast key management scheme is required to ensure that only legitimate users will continue to receive the latest information. In the literature, star-based key management schemes and tree-based key management schemes were proposed for secure group communications. In this thesis, we propose a novel canonical-tree-based key management scheme. We evaluate the average rekeying costs of the canonical-tree-based scheme as well as two well-known key management schemes. We find that the leaving probability of group members dominates the relative performance between the star-based scheme and the tree-based scheme. Based on the above observations, we propose an adaptive key management scheme that is superior to both the star-based scheme and the tree-based scheme in a dynamic environment.

This study developed and tested a contingency model of group communication in Korean workgroups that posited that the communication effectiveness and group performance of workgroups is determined by the “fit” of communication practices with organization structure and group relational climate. A contingency model incorporates three variables: contingency variables, response variables, and performance variables. Based on a review of the literature on Korean organizations and groups, the model incorporated two contingency variables: organizational structure and group relational climate. Organizational structure was indexed by the level of centralization and formalizations in the organization. Group relational climate was indexed by the level of closeness and group conformity among members. The response variables, communication practices of Korean workgroups, was measured in terms of the frequency of formal and informal meetings held by the workgroups. Two types of performance were measured: communication effectiveness and performance level. The contingency model hypothesized that the level of communication effectiveness and group performance of a workgroup that engages in communication practices which fit the requirements of organizational structure and group relational climate will be higher than that of a group whose communication practices do not fit the requirements of organizational structure and group relational climate. It also hypothesized the communication effectiveness group performance would be lower in groups which faced conflicting contingencies than in groups that faced consistent contingencies. A survey of 409 members of 84 workgroups in 37 Korean organizations was conducted. Results of this study supported the predictions of the contingency model. In particular, centralization, formalization, and closeness were significant contingency variables. The hypothesis regarding conflicting contingency was not supported. Implications of the study regarding the contingency theory, group communication and group effectiveness, and the nature of Korean groups and organizations are discussed.

Research is necessary to uncover ways to improve adolescent nutrition and reduce obesity rates, particularly in the Appalachian region, which has high rates of food insecurity and adolescent obesity. The current study examines rural cultural norms about food, memorable messages adolescents received about nutrition, and the sources of identified memorable messages. Adolescents shared memorable messages during comprehensive, semi-structured, small group interviews in which participants revealed their individual experiences. Thematic framework analysis is used to present the range and nature of memorable messages about nutrition and to develop strategies for future health campaigns and interventions. This qualitative method of sequential inductive analysis provides transparency of data and resulting interpretations through thematic identification and indexing. Analysis revealed themes of messages that featured critical pieces of the rule-structure of memorable messages – specifically, adherence and consequence regarding nutritional behaviors. Prominent memorable messages of adherence included topics of balance (e.g., MyPlate), type (e.g., junk food), and timing (e.g., “don’t eat after 7 p.m.”). Messages with elements of consequence included communication of short-term (e.g., “breakfast gets your blood flowing) and long-term consequence (e.g., obesity, etc.). Adolescents identified family members, educators, and media as salient sources of memorable messages.

In dynamic peer group communications, security has been in high demand by many applications in recent years. One of the more popular mechanisms to satisfy these security requirements is the group key scheme in which the group key is to be shared by each group communication participant. However, how to establish and manage the group key efficiently in order to protect such communications imposes new challenges - especially when such schemes are to be deployed on resource-limited networks such as Mobile Ad hoc Networks (MANETs). The basic needs of such network settings require that the group key schemes must demonstrate not only high performance but also fault-tolerance. Furthermore, to encrypt group communication messages efficiently is essential. Therefore, it is anticipated that the contributions of this thesis will address the development of lightweight and high performance key management protocols for group communications while guaranteeing the same level of security as other approaches. These contributions are listed below: First, two efficient individual rekey schemes, in which most group members process one-way hash functions and other members perform Diffie-Hellman operations, are proposed to obtain performance efficiency. Second, a periodic batch rekey scheme is proposed to handle the out-of-sync problem resulting from individual rekeying schemes in cases where there is a high rate of group member requests for joining/leaving. Third, scalable maximum matching algorithms (M2) are designed to incorporate a tree-based group key generation scheme to forward the partial keys to other group members. Fourth, a hybrid group key management architecture is proposed as well to combine the advantages of centralized and contributory group key schemes. Fifth, a Fast Encryption Algorithm for Multimedia (FEA-M) is enhanced to overcome the vulnerabilities of its original solution and its former improved variant. Performance analyses and experimental results indicate that the proposed approaches reduce computational costs and communication overhead as compared to other popular protocols.

Communication processes can be affected by stigma – a negative evaluation of an individual’s attributes that discredits or identifies the individual as not normal (Goffman, 1963). One such communicative process that is affected by stigma is disclosure. Disclosure is when individuals share personal information that reveals something not previously known (Charmaz, 1991). One such group of individuals who may be forced to choose between disclosing (to get accommodations or social support) and avoiding stigma (by not disclosing) is individuals with disabilities (Braithwaite, 1991; Charmaz, 1991). This study focuses on one particular population of individuals with disabilities – those with a hearing loss. Through the use of interactive interviewing and Communication Privacy Management (CPM) theory, this study examines hard of hearing and deaf individuals’ perceptions of both the disclosure process and stigma. CPM examines how and why people conceal or reveal private information, such as hearing loss (Petronio, 1991, 2002). Using CPM, this study poses research questions surrounding how hard of hearing individuals disclose and manage turbulence surrounding their hearing loss. Further, participants’ perceptions and responses to stigma surrounding hearing loss are also examined. Based on the participants’ responses, managing the boundaries surrounding their hearing loss includes considerations of identity, the other person/people in the interaction, risks of not disclosing, timing, and how much to disclose. Further, participants viewed boundary turbulence as positive only when it was helpful; otherwise, they reported a feeling of a loss of control. In examining stigma and other consequences of disclosure, participants talked about being labeled, not being worth others’ time, and being seen as incapable. Finally, participants reported a wide variety of responses to stigma surrounding their hearing loss. In this study, I also discuss the implications of these findings, both theoretical and practical implications, and how they reflect the lives of the deaf and hard of hearing. Finally, I address the directions for future research on this topic as well as the limitations to this study.

A cancer diagnosis often causes biographical disruption in the lives of young adult (i.e., 18-39; YA) survivors and their close social network members (i.e., familial, plutonic, or romantic relational partners with whom the survivor has a salient relationship; SNM). In order to integrate their illness into their lives, normatively regain balance and equilibrium, and achieve a “new normal” following a cancer diagnosis, YA survivors and their close SNMs must work to reconstruct their biographies by engaging in tangible interpersonal communication processes often used to initiate and maintain relationships. However, YA cancer survivors report facing social struggles due to the biographical disruption of their illness across the trajectory of diagnosis, treatment, and survivorship. To learn more about their unique social experience of cancer, I conducted private, open-ended narrative interviews with 20 YA survivor-close SNM dyads, 1 YA survivor-SNM close triad, and 10 individual YA survivors (N = 51). I used thematic narrative analysis to determine how and why YA cancer survivors and their close SNMs communicate social support messages with romantic partners, family, friends, peers, and one another. By examining the narratives of YA survivors, their close SNMs, and the dyad itself, this dissertation explores the interpersonal communication processes used to initiate and maintain relationships across the illness trajectory by focusing on the barriers and facilitators these individuals experience in the communication of social support. Through their individual narrative accounts, YA survivors explained why and how they perceived various support attempts from others to be positive or negative, and their close SNMs detailed their attempts to navigate the YA’s larger support network and assume the duties inherent in their newly-adopted “top supporter” role. In addition, reports from YAs and their SNMs revealed that they often engaged in mutual pretense, a unique and often unsustainable form of support that occurred between YA survivors and their close SNMs involving topic avoidance and emotional management. Implications for the advancement of interpersonal communication theory and for practical intervention targeting YA patients and survivors, their close SNMs, and medical practitioners are also discussed.

Forced by the atrocities of war from their native country, Bosnian families came to United States seeking refuge and a new life. Immigrating to a new country, however, involves the process of acculturation which can dilute many native practices. Like many refugees that immigrated, Bosnians sought to adapt to the American way of life, while keeping their traditional ethnic customs, practices, and religion (Val & Iain-Walker, 2003). Many Bosnian refugee parents worked to keep the Bosnian practices prevalent in their first and second generation Bosnian American children. By doing so, Bosnian parents imbedded into their children the original customs, practices, and traditions of the Bosnian culture. Moreover, they raised their children to have great pride in their native country. Part of keeping the native culture alive, as an adult child of a refugee, involved marrying someone of the same ethnic and religious background (Inman, Howard, Beaumont, &Walker, 2007). Using Communication Acculturation Theory, this study examined the relationship between the degree of acculturation of Bosnian refugees in the United States and their preference and stress level in relational partner selection taking into consideration parental pressure and ethnic group community expectations. Results from this study find that acculturation is negatively correlated with the preference for a Bosnian mate but only the amount of interpersonal intimate communication the Bosnian members has with Bosnians and non-Bosnians is indicative of any mate selection stress experienced. Further, ethnic group community expectations and parental pressure are positively correlated with preference for a Bosnian mate, but only the expectations of the ethnic group and not pressure from parents was correlated with any stress the individual feels to find a Bosnian mate.

This study examined advice interactions following infidelity. Participants (N = 213) completed a survey concerning an instance on infidelity and a subsequent advice interaction. Injured party perceptions of advice interactions were measured by examining advice messages, perceived face threat, and perceived face support, in addition to perceived effectiveness of the advice message. Results from this study showed no significant differences in perceived face threat, perceived face support, or advice effectiveness between different advice messages. Results also indicated both positive and negative face threat as negative predictors of advice effectiveness. While negative face support was a positive predictor of advice effectiveness, positive face support was a negative predictor. When controlling for relational closeness, negative face support was the only significant predictor of advice effectiveness.