481 |
Reliable on-demand routing protocols for mobile ad-hoc networksKhan, Shariq Mahmood January 2015 (has links)
Mobile Ad-Hoc Network (MANET) facilitates the creation of dynamic reconfigurable networks, without centralized infrastructure. MANET routing protocols have to face high challenges like link instability, node mobility, frequently changing topologies and energy consumption of node, due to these challenges routing becomes one of the core issues in MANETs. This Thesis mainly focuses on the reactive routing protocol such as Ad-Hoc On-Demand Distance Vector (AODV) routing protocol. Reliable and Efficient Reactive Routing Protocol (RERRP) for MANET has been proposed to reduce the link breakages between the moving nodes. This scheme selects a reliable route using Reliability Factor (RF); the RF considers Route Expiration Time and Hop Count to select a routing path with high reliability and have less number of hops. The simulation result shows that RERRP outperforms AODV and enhance the packet delivery fraction (PDF) by around 6% and reduces the network routing load (NRL) by around 30%. Broadcasting in MANET could cause serious redundancy, contention, and collision of the packets. A scheme, Effective Broadcast Control Routing Protocol (EBCRP) has been proposed for the controlling of broadcast storm problem in a MANET. The EBCRP is mainly selects the reliable node while controlling the redundant re-broadcast of the route request packet. The proposed algorithm EBCRP is an on-demand routing protocol, therefore AODV route discovery mechanism was selected as the base of this scheme. The analysis of the performance of EBCRP has revealed that the EBCRP have controlled the routing overhead significantly, reduces it around 70% and enhance the packet delivery by 13% as compared to AODV. An Energy Sensible and Route Stability Based Routing Protocol (ESRSBR) have also been proposed that mainly focuses on increasing the network lifetime with better packet delivery. The ESRSBR supports those nodes to participate in the data transfer that have more residual energy related to their neighbour nodes. The proposed protocol also keeps track of the stability of the links between the nodes. Finally, the ESRSBR selects those routes which consist of nodes that have more residual energy and have stable links. The comparative analysis of ESRSBR with AODV and recently proposed routing protocol called Link Stability and Energy Aware (LSEA) routing protocol revealed that the proposed protocol ESRSBR has a significantly affect the network lifetime, increases it around 10% and 13% as compared to LSEA and AODV protocols respectively. The ESRSBR also decreases the routing overhead by 22% over LSEA and by 38% over AODV.
|
482 |
Acoustic performance of dissipative and hybrid silencers in ducts with large transverse dimensionsWilliams, Paul Timothy January 2015 (has links)
Numerical models will be developed for the prediction of silencer transmission loss under the operating conditions present in gas turbine exhausts. In these systems the large diameter ducts and high operating temperatures produce a challenging acoustic environment due to the unverified behaviour of fibrous materials at high temperatures and the existence of complex sound fields. To understand the behaviour of fibrous materials at high temperatures their bulk acoustic properties are measured using a modified impedance tube which can heat material samples up to a temperature of 500 C. It will be demonstrated that the high temperature material properties can be extrapolated from room temperature measurements given knowledge of the temperature dependant flow resistivity. Finite element numerical models using point collocation and mode matching techniques to predict the transmission loss of silencers are developed and successfully validated. Dissipative silencer designs with various cross-sectional designs are explored numerically and experimentally according to common industry standards. It is demonstrated that transmission loss may be optimised by the arrangement of the fibrous material across the cross-section. The accurate numerical models allow for effe cient silencers to be designed reducing silencer size and cost. A new hybrid silencer is presented combining dissipative and reactive elements with the aim of increasing the low frequency attenuation of large silencers while maintaining an effective broadband spectrum. Measurements and predictions show this innovative design to be successfull. Application of the hybrid silencer allows for more flexible noise control solutions when design is limited by low frequency noise.
|
483 |
Testing the instrumental and reactive motivations of romantic relational aggressionClifford, Charity E. January 1900 (has links)
Doctor of Philosophy / School of Family Studies and Human Services / Amber Vennum / The literature suggests that aggressive behaviors occur in response to provocation (i.e., reactive aggression) or to achieve a goal (i.e., instrumental aggression). Relational aggression –when an individual harms another’s interpersonal relationships – has been studied from the reactive and instrumental framework in peer-directed contexts, usually with children. However, relational aggression in romantic relationships is yet to be studied from this framework. This dissertation includes a series of studies investigating whether two specific relationally aggressive behaviors found in romantic relationships (i.e., social sabotage and love withdrawal) are 1) motivated by instrumental and reactive aggression, 2) associated with differential characteristics, and 3) predictive of negative outcomes. The Romantic Relational Aggression Motivation (RRAM) scale, which included social sabotage and love withdrawal items with both instrumental and reactive motivations, was created to explore the above research questions. During Study 1a, an exploratory factor analysis using a sample of 170 emerging adults tested the factor structure of the RRAM. This resulted in love withdrawal, but not social sabotage, factoring into instrumental and reactive subscales. Using the same sample at a later wave, Study 1b refined the RRAM from Study 1a; the findings confirmed the results of Study 1a. In Study 2, using a sample of 118 emerging adults, the factor structure found in Study 1b was corroborated using a confirmatory factor analysis. Study 2 found that social sabotage was more closely related to instrumental than reactive love withdrawal. Reactive and instrumental love withdrawal were clearly differentiated based on their associations with constructs that were emotionally driven (e.g. neuroticism and hostile attribution bias) but not by their associations with constructs that dealt with power (e.g. self-relationship power and trait dominance). None of the romantic relational aggression scales were predictive of the negative outcomes in the study, possibly due to the small sample size (85 emerging adults) in the longitudinal portion of Study 2. As instrumental and reactive love withdrawal were associated with different constructs and combining the two together may cause substantial differences to be lost, the RRAM may be a useful tool for researchers of romantic relational aggression.
|
484 |
'n Studie van die elektroniese kompensasie van vervormings in kragnetwerke02 March 2015 (has links)
M.Ing. / Please refer to full text to view abstract
|
485 |
Understanding Bullying Participant Roles: Stability across School Years and Personality and Behavioral CorrelatesCrapanzano, Ann 17 December 2010 (has links)
This study investigated the factorial validity, stability, and social, behavioral and emotional correlates of several different roles that students can play in the context of bullying. Data were collected from students at two time points across two school years, April and May of 2006 (n=284) and again in November and December of 2006 (n=185). A confirmatory factor analysis provided evidence for the validity of 4 participant roles (i.e. bully, reinforcer, assistant, and defender). However, further analysis revealed that there was a strong degree of intercorrelation between the three bully factors (i.e., bully, reinforcer, and assistant). Analyses found that participant roles are fairly stable across school years and that the greater the percentage of same raters across the time points, the greater the stability. All of the bullying roles (i.e., bully, reinforcer, and assistant) were significantly related to callous unemotional traits, emotional dysregulation, positive expectations for aggression, conduct problems, reactive relational aggression, proactive relational aggression, reactive overt aggression, and proactive overt aggression, but these relationships were stronger in boys. It was also found that the defender role was associated with less aggression and more prosocial behavior. These associations were stronger in girls. Finally, a linear regression analysis of the interaction between participant roles and victimization revealed that at T1, the association between bullying roles and aggression was moderated by victimization. Specifically, the association was stronger in those low on victimization. At T2, the association between defending and lower aggression and greater prosocial behavior was stronger in those low in victimization.
|
486 |
Iron Citrate Toxicity Causes aco1Δ-induced mtDNA Loss in Saccharomyces cerevisiaeFarooq, Muhammad Ali 01 May 2013 (has links)
Aconitase is an enzyme of the Krebs cycle that catalyzes the isomerization of citrate to isocitrate. In addition to its enzymatic activity, Aco1 has been reported to bind to mitochondrial DNA (mtDNA) and mediate its maintenance in the budding yeast S. cerevisiae. In the absence of Aco1, cells rapidly lose mtDNA and become “petite” mutants. The purpose of this study is to uncover the mechanism behind mtDNA loss due to an aco1 deletion mutation. We found that an aco1 mutation activates the mitochondria-to-nucleus retrograde (RTG) signaling pathway, resulting in increased expression of citrate synthases (CIT) through the activation of two transcription factors Rtg1 and Rtg3. Increased activity of CIT leads to increased iron accumulation in cells, which is known to raise reactive oxygen species (ROS). By deleting RTG1, RTG3, genes encoding citrate synthases, orMRS3 and MRS4, encoding two irontransporters in the mitochondrial inner membranes, mtDNA loss can be prevented in aco1 deletion mutant cells. We further show that the loss of SOD1, encoding the cytoplasmic isoform of superoxide dismutase, but not SOD2, encoding the mitochondrial isoform of superoxide dismutase, prevents mtDNA loss in aco1 mutant cells. Altogether, our data suggest that mtDNA loss in aco1 mutant cells is caused by the activation of the RTG pathway and subsequent iron accumulation and toxicity in the mitochondria.
|
487 |
Mechanisms and transients involved in the solar conversion of petroleum films in aquatic systemsRay, Phoebe Z 13 August 2014 (has links)
The behavior of Deepwater Horizon crude oil and other sources of oil were investigated when exposed to sunlight in aquatic systems under environmentally relevant conditions. This research decoupled the abiotic and biotic weathering modifications of oil by focusing solely on the photochemical transformations of oil in aquatic systems. Photochemical rates and mechanisms were measured through the determination of reactive transients. Total hydroxyl radical formation was studied using high benzoic acid concentrations and varying exposure time. Titanium dioxide (TiO2) nanomaterials were added to the system in an effort to determine if the photocatalyst would enhance oil photodegradation. Photochemical production of singlet oxygen from thin oil films over seawater and pure water was measured with furfuryl alcohol as a selective chemical probe. The loss of furfuryl alcohol and the formation of 6-hydroxy(2H)pyran-3(6H)-one were monitored. Photochemical production of organic triplets from 6 different compositions of petroleum was measured through the cis-trans isomerization of 1,3 pentadiene in Gulf water. The data correlate very well with previously measured singlet oxygen concentrations. The energies were measured in the range of 280-300 kJ/mol. Macondo Well Oil from the Deepwater Horizon (DWH) rig was mixed with pure water and seawater and irradiated with simulated sunlight. After irradiation, the water-soluble organics (WSO) from the dark and irradiated samples were extracted and characterized by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Liquid-liquid extraction yielded two fractions from dark and irradiated water/oil mixtures: acidic WSOs (negative-ion electrospray (ESI)), and base/neutral WSOs (positive-ion ESI). These fractions were analyzed by FT-ICR MS to catalogue molecular-level transformations that occurred to oil-derived WSOs after solar irradiation. The increased abundance of higher-order oxygen classes in the irradiated samples relative to the dark samples indicates that photooxidized components of the Macondo crude oil become water-soluble after irradiation. Time series studies were performed to observe the changes in WSO composition. The predominance of higher-order oxygen classes indicates that multiple photochemical pathways exist that result in oxidation of petroleum compounds. More oxygenated compounds were observed in the WSO acid fraction of oils with higher API gravity.
|
488 |
Comparative Analysis of Load Flow Techniques for Steady State Loading Margin and Voltage Stability Improvement of Power SystemsTogiti, Santosh 11 August 2015 (has links)
Installation of reactive compensators is widely used for improving power system voltage stability. Reactive compensation also improves the system loading margin resulting in more stable and reliable operation. The improvements in system performance are highly dependent on the location where the reactive compensation is placed in the system. This paper compares three load flow analysis methods - PV curve analysis, QV sensitivity analysis, and Continuation Load Flow - in identifying system weak buses for placing reactive compensation. The methods are applied to three IEEE test systems, including modified IEEE 14-bus system, IEEE 30-bus system, and IEEE 57-bus system. Locations of reactive compensation and corresponding improvements in loading margin and voltages in each test system obtained by the three methods are compared. The author also analyzes the test systems to locate the optimal placement of reactive compensation that yields the maximum loading margin. The results when compared with brute force placement of reactive compensation show the relationship between effectiveness of the three methods and topology of the test systems.
|
489 |
Profiles of the Forms and Functions of Aggression and Psychosocial Outcomes in Two Distinct Juvenile Offender PopulationsThompson, Kelli R 13 May 2016 (has links)
The current study was designed to explore profiles of reactive and proactive aggression in two distinct juvenile offender populations, in a group of juvenile offenders who have been adjudicated for illegal sexual behavior (n = 138) and in a group of juvenile offenders adjudicated for general delinquent behavior (n = 243). This is the first study of its kind to investigate profiles of aggression in a population of juveniles adjudicated for illegal sexual behavior. Preliminary profile analyses indicated that the two juvenile offender populations had similar profiles of aggression overall. Two step cluster analysis results were generally consistent with previous research (Crapanzano, Frick, & Terranova, 2010; Marsee et al., 2014) with 3 groups emerging for both overt and relational aggression: a combined group high on both reactive and proactive aggression, a group high in reactive aggression alone, and a low overall group. Post hoc comparisons of the clusters revealed that the high combined group consistently demonstrated higher reports of emotional and behavioral dysfunction supporting the hypothesis that the presence of proactive aggression serves more as an indicator of severity rather than as representing a qualitatively distinct group in and of itself. Policy implications regarding sex offender registration and notification laws extended to juveniles are discussed.
|
490 |
Involvement of abscisic acid and H2O2 in antioxidant enzyme activities mediated by nitric oxide synthase-like activity in maizeHlatshwayo, Siphiwe Gift January 2018 (has links)
>Magister Scientiae - MSc / In recent years, nitric oxide (NO) has emerged as an important endogenous plant
signalling molecule that mediates many developmental and physiological
processes. NO regulates the activity of antioxidant enzymes in response to droughtinduced
stress by controlling the expression of the genes that encode these enzymes.
Antioxidant enzymes function in scavenging reactive oxygen species like
superoxide ion (O2
-) and hydrogen peroxide (H2O2) that are generated in response
to drought-induced stress and other abiotic stresses. Abscisic acid, a phytohormone
that acts as a stress-related hormone in plants, also stimulates production of H2O2,
thus further triggering the antioxidant enzyme activity in order to scavenge the
excess H2O2. Accumulated data indicate that NO interacts with reactive oxygen
species, notably hydrogen peroxide and superoxide. This study was aimed at
clarifying the role of NO derived from nitric oxide synthase-like (NOS-like)
enzymatic activity in scavenging of H2O2 and to establish if this is dependent or
independent of ABA signaling. This was achieved by using Nω-Nitro-L-Arginine
methyl ester (L-NAME), an inhibitor of NOS to control the amount of NO in maize
tissue. The study investigated the effect of L-NAME on the accumulation of
superoxide, which is scavenged by superoxide dismutase. Furthermore, the study
determined the role of NOS-like activity in ABA-mediated production of H2O2.
Lastly, the effect of L-NAME on H2O2 accumulation and antioxidant enzyme
activity was also investigated. Application of L-NAME altered the enzymatic
activity of superoxide dismutase, ascorbate peroxidase and catalase. These changes
in enzymatic activity were coupled with altered levels of O2
- and H2O2 in leaves
and roots. Treatments with ABA in combination with L-NAME resulted in reversal
of H2O2 content to basal levels. These results suggest that nitric oxide, produced by
nitric oxide synthase-like activity, is important in regulation of antioxidant enzyme
activity and cross-talks with ABA.
|
Page generated in 0.0417 seconds