286 research outputs found
Investigation of electroless nickel undercoat for duplex nickel chromium electrodeposition onto aluminium and its alloys
No full textA thesis submitted in partial fulfillment of the requirement of the University of Wolverhampton for the
Degree of Master of Philosophy.The study investigates the deposition of a multilayer coating onto two aluminium alloys: Al 1050 and Al 6061. Of particular interest has been the treatment of the surface of both these samples for deposition of metallic coatings through a zincate based immersion process. The zinc immersion layer chemically displaces the oxide film on Al 1050 and Al 6061 and then zinc is deposited followed by nickel and chromium electrodeposition. Superior adhesion was associated with uniform, thin and fine grained deposits from Bondal solution which exhibited rapid and complete coverage of both aluminium samples. The metallurgical characteristics of the aluminium alloys and the processing sequence developed had a significant influence on the growth and morphology of the deposits from the Bondal solution and affected subsequent adhesion of electroplated nickel and chromium. This engendered the treated surface with sufficient catalytic nature to be able to receive a subsequent electroless nickel layer together with finishing layers of electrolytic nickel and chromium respectively. Due to the favourable physical properties of aluminium and its alloys (density, strength to weight ratio), there is a growing demand for nickel/chromium coated aluminium components for automotive and other applications. The most common method currently is to directly electroplate nickel onto the aluminium substrate. However, this can lead to problems with components having complex geometry in that chemical attack on the pretreated aluminium can occur in low current density areas before the substrate can be completely covered with nickel due to the acidic nature and high temperature of the nickel electroplating process. One way of preventing this current density related problem is to use an electroless nickel undercoat before the nickel/chromium deposit is applied. The mechanism by which this occurs is not fully understood and it is an objective of the current research to investigate the mechanism of nucleation of the electroless nickel layer on zincated aluminium. Results of X-ray photoelectron spectroscopy showed that the zincated layer was dissolved in the electroless nickel bath but zinc was detected below 10 nm from the top surface of the homogenous nickel phosphorus film, while aluminium and alloying elements from both alloys have diffused into the film. Hexavalent chromium electroplating from chromic acid is under pressure due to its health hazard and environmental problems and is subjected to increasingly stringent control and legislation. Health and safety considerations have prompted the electroplating industry to consider alternatives to coating processes that involve hexavalent chromium. It is a further objective of the research to compare the properties of nickel/chromium coated aluminium with top coats of chromium deposited from hexavalent and trivalent (chloride based) electrolytes. Duplex nickel and chromium electrodeposition were modified with an electroless nickel undercoat, thus four coatings were studied for the aluminium samples. Results obtained from the hardness measurements of Al 1050 and Al 6061 were compared for four coatings. Hardness tests profiles obtained for Al 1050 and Al 6061 show that deposits from trivalent chromium electrolytes were not as hard as hexavalent chromium deposits. However, the hardness of duplex nickel/chromium coatings was improved by use of an electroless nickel undercoat. Scratch adhesion tests were focused on the failure mode of coatings evaluated on the basis of scratch channels, frictional force and acoustic emission signals. The adhesion test showed buckling and chipping of the coatings with no sign of spallation or delamination. Four coatings exhibited a higher critical load for both aluminium alloy samples. This confirmed that failure occurred within the coatings, rather than adhesive failure at the coating/substrate interface. Results obtained from copper acetic acid salt spray and electrochemical corrosion tests for Al 1050 and Al 6061 exhibited excellent corrosion resistance. Scanning electron microscope images showed initiation and propagation of small pits which did not coalesce to form large and deep craters that could result in the eventual failure of the coatings. Micro discontinuous chromium deposits spread the corrosion current, thus improving corrosion performance. Icorr values obtained from linear polarization corrosion tests show higher values for duplex nickel/chromium coatings on Al 1050 than Al 6061. Icorr values show similar trends for duplex nickel/chromium coating on Al 1050 and Al 6061 modified with an electroless nickel undercoat. In conclusion results showed a significant improvement in the chromium electroplating characteristics of Al 1050 and Al 6061 with an electroless nickel undercoat
Assessing the Processes of Family-To-work Spillover: A Comparison of National Guard At-Home Partners Experiencing Military Deployment and a Non-Deploying Group
No full textScholars have characterized as “extreme” the intersection of work and family in military service (MacDermid Wadsworth & Southwell, 2011) and periods of deployment involve further stress for partners of military members (e.g. Not having enough personal time, having too many responsibilities at home, changing marital roles, and parenting hassles) that may make managing both work and family life more difficult (Chandra et al., 2011). Research with partners of deployed service members has focused primarily on mental health (Donoho et al., 2018; Mansfield et al., 2010) as well as parenting and household responsibilities (Chandra et al., 2011), but less is known about partners’ employment related outcomes. In the current study, both role strain and role enhancement processes were tested over time in a sample of employed partners of deployed Army National Guard Members (GMs) and a comparison group composed of partners of non-deploying GMs. In accordance with theories of work-family conflict (Greenhaus & Beutell, 1985) and resource drain theory (Rothbard, 2001), a model utilizing two waves of data was tested; household challenges experienced by at-home partners were hypothesized to be related to more negative family-to-work spillover, and ultimately associated with less job engagement and more depressive symptoms. In addition theories of work-family facilitation (Grzywacz & Butler, 2005) and workfamily enrichment (Greenhaus & Powell, 2006) were utilized to test whether family strengths (e.g. effective family functioning and military spouse role satisfaction) in the face of deployment were associated with positive FTW spillover, and ultimately with more job engagement and fewer depressive symptoms. Results revealed that household challenges were related to more negative family-to-work spillover, more depressive symptoms, and less job engagement. Effective family functioning was related to more positive FTW spillover, which was related to more job engagement. Results were consistent across the deploying and non-deploying group with the following exception: in the deploying group only, negative FTW spillover was associated with more depressive symptoms. The current study has implications for the field of work and family research, employers, and military family service providers. First, the current study provided evidence of cross-domain work-family conflict and work-family enrichment in a sample of partners of National Guard members. Second, the study highlighted numerous consequences for employees facing significant household challenges. The role of household challenges in employees’ lives may have implications for how employers should structure workplace culture and the employee supports they offer. Finally, only partners of deployed GMs experienced more depressive symptoms associated with negative FTW conflict. Military family service providers may use that information to better serve partners of deploying service members who are at risk of mental health concerns during deployment
A Longitudinal Examination of Couple Communication and Role Negotiations Following a Military Deployment
No full textAcross deployment cycles, individuals negotiate family roles to accommodate the absence then re-entry of service members. There is scant empirical evidence about the processes through which roles are reorganized. Guided by the family resilience framework (Walsh, 2016b) and the model of military marriage (Karney & Crown, 2007), I hypothesized that communication would be a mechanism through which couples negotiated roles during reintegration. Couple communication was conceptualized as occurring over two distinct but related temporal rhythms: established communication patterns and daily communication strategies. I expected that couples’ Time 1 (T1) established patterns (problem solving and withdrawal) would predict role negotiations at Time 3 (T3), and that these associations would be mediated by daily communication strategies at Time 2 (T2). 54 heterosexual National Guard couples were interviewed at three times across eight months after service members’ return from deployment. T1 and T3 were in-person interviews and measured participants’ established patterns of family life, including established communication patterns and ease in role negotiations. T2 was a four-day data “burst” and captured couples’ daily behaviors such as competence with daily communication strategies. Path analyses indicated that T1 problem solving (an established pattern) predicted service members’ more competent T2 daily communication and easier T3 role negotiations. While no indirect associations emerged for either partner, significant others’ T2 more competent daily communication strategies predicted easier T3 role negotiations for both partners. Results suggest that problem solving and competent daily communication strategies contribute to resilient family functioning during reintegration. This study highlights the viability and importance of adopting multiple temporal rhythms to examine processes across couple transitions
Understanding turnover intentions: The role of life course fit
No full textThe first decade of this millennium has been marked by declines in the labor force participation of women for the first time in 40 years. These declines coupled with skills shortages in key occupations, such as engineering have created concern among scholars, employers and policy makers. This dissertation utilized the recent conceptualization of life course fit to understand voluntary turnover intentions among employees in the United States by examining the predictors of life course fit (Study I) and the association between life course fit and voluntary turnover intentions (Study II). Occupation, sex, sex composition of occupation and workplace social support predicted life course fit. Life course fit significantly predicted turnover intentions accounting for 11% of the variance in turnover intentions. Life course fit partially mediated the association between organizational commitment and turnover intentions, as well as the association between job satisfaction and turnover intentions. Supervisor support and coworker support moderated the association between life course fit and turnover intentions such that higher levels of support weakened the association between fit and turnover intentions for those who experienced a lack of fit. Implications for workplace practice will be discussed
Depressive Symptomology and Partner-Directed Coping in the Context of Deployment-Induced Transitions
No full textThe relationship between marital quality and depressive symptomology has interested scholars for decades. Two prominent theories have commonly been used to inform such investigations: (1) the Stress Generation Hypothesis, which suggests that higher levels of depressive symptomology contribute to lower levels of marital quality; and (2) the Marital Discord Model of Depression, which suggests that lower levels of marital quality contribute to higher levels of depressive symptomology. It has been suggested that, when examined within a dyadic context, the Stress Generation Hypothesis may better characterize actor associations (i.e., associations between one’s own marital behavior and depressive symptomology), whereas the Marital Discord Model of Depression may better characterize partner associations (i.e., associations between one spouse’s marital behavior and the other spouse’s depressive symptomology). Thus, it may be that distressed individuals enact maladaptive marital behaviors (i.e., actor stress-generation effect) that, over time, elevate their partners’ levels of depressive symptomology (i.e., partner marital-discord effect). The main purpose of this study was to evaluate this hypothesis within a sample of military couples coping with deployment-induced transitions. Because deployment-induced transitions are likely stressful, they provide a rich landscape on which to examine associations between psychological adjustment and marital quality within a dyadic context. Data for the current study came from an ongoing, longitudinal study of National Guard families. Study analyses utilized three waves of prospective interview data per couple: (1) predeployment, (2) deployment, and (3) reintegration. Participants included 154 heterosexual, married couples in which service members identified as male. Key constructs were measured with latent variables and included service members’ and significant others’ self-reported depressive symptomology at predeployment and reintegration, as well as significant others’ self-reported partner-directed coping (i.e., active engagement and minimization) during deployment. Data were analyzed within a structural equation modeling framework. Findings provided marginal support for study hypotheses. For example, prior to accounting for stability in depressive symptomology, significant others’ minimization of service members’ concerns during deployment mediated a longitudinal association between significant others’ depressive symptomology at predeployment and service members’ depressive symptomology at reintegration. In addition, significant others were more likely to minimize service members’ concerns during deployment when service members self-reported higher levels of distress at predeployment. These findings enrich our understanding of how, in the context of stressors external to marriage, individuals’ psychological well-being is related to exchanges that take place within marriage. In being guided by both the Stress Generation Hypothesis and the Marital Discord Model of Depression, study findings elucidate specific pathways through which marital quality and individual well-being are related across time and partners. Potential implications for intervention efforts aimed at bolstering couple resilience to periods of prolonged stress and transition are discussed
The relationships between marital commitment and housework
No full textThis study assumes that spouses are motivated to make adjustments in order to maintain their marital relationship. However, not everyone shares the same motivation to maintain their relationship. Given the importance of task sharing in maintaining marital relationships, the focus of the current study is on the relationship between marital commitment and household labor. Specifically, the current study defines marital commitment as one\u27s motivation to maintain the marital relationship and relationship maintenance behavior as in the form of time spent in sharing housework. Utilizing the wave 2 data from the National Survey of Families and Households (Sweet & Bumpass, 1996), the analytic data consisted of 4051 pairs of married couples. This study applied the hierarchical linear modeling approach to manage the effect of dyadic interdependence on the relationship between individual\u27s marital commitment and housework contribution. Additionally, marital commitment was examined in three forms: personal, moral, and structural commitment. Housework was categorized as low- or high-schedule-control housework. Results from the current study enhance our knowledge about the relationships between the three types of commitment and housework contribution in two ways. First, individuals\u27 marital commitment was related to their perception of fairness in chores at home. Particular, all three types of marital commitment were positively and significantly related to the log-odds of perceiving the division of housework as fair to both (relative to unfair to wife ). Second, the relationships between marital commitment and housework contribution differed depending on gender and the type of commitment. This study revealed that one\u27s own moral commitment was most strongly related to one\u27s own low-schedule-control housework for wives but not husbands. Additionally, while husbands\u27 personal commitment had the strongest positive correlation with wives\u27 hours of low-schedule-control housework, wives\u27 moral commitment had the strongest negative correlation with husbands\u27 low-schedule-control housework
The effects of social support and network orientation in the stress-illness relationship of HIV-infected individuals
No full textA sample of 83 HIV-infected individuals completed a questionnaire assessing stressful life events, social support, network orientation, physical symptoms, and depression. Path analyses were conducted to examine the relationship of stressful life events, social support, and network orientation to physical symptoms and depression. Of particular interest was the relationship of the functions of social support: appraisal, belonging, self-esteem, and tangible. The results indicated a relationship between stress and physical symptoms and depression. No buffering effects of social support were found. Evidence of a main effect between social support and depression was found with self-esteem having a significant relationship with depression. No relationship between network orientation and physical symptoms and depression was found although a relationship was found between network orientation and social support
Working and caring: The relationship between women\u27s work situations and caregiving for elderly family members
No full textSeveral societal changes are related to the heightened importance of understanding work-caregiving relationships. Yet, the studies that examine the relationship between women\u27s involvement in work and in caregiving reveal conflicting results. In order to better understand the issue, the role of intervening variables was examined. Thirty-nine women who were working full-time and caring for elderly family members who lived in the community completed detailed questionnaires about work and caregiving. First, three contextual variables were tested for their role as moderators: care receiver\u27s functional status, women\u27s job flexibility and occupational role salience. Care recipient\u27s functional status did not moderate the relationship between the number of hours women worked and the extent or the quality of the care they provided. Care receiver\u27s difficulty with IADL, however, moderated the relationship between the number of hours women worked and the work interference they experienced. In addition, job flexibility moderated the association between temporal involvement in care and job interference due to care responsibilities. Next, Kohn\u27s theory of work socialization was applied to caregiving for elderly family members. The relationship between work conditions that encourage self-direction and women\u27s belief in paternalism in caregiving situations was studied using authoritarian conservatism as a mediating factor. An unexpected curvilinear relationship between self-directive work conditions and authoritarian conservative orientations was observed. Although authoritarian conservatism was found to be related to women\u27s belief in paternalism, its role as a mediating factor was not established. The strengths and limitations of the study and the implications of its findings for future research and practice are discussed
Stress and parenting among Mexican American and European American families
No full textThe purpose of this study was to investigate the process by which various stressors (economic and life event stressors) influence the parenting behaviors of Mexican American and European American parents. A model was devised that posits that family cohesion and various coping strategies (e.g., social support) mediate the influence of stressors on parenting behavior. Unlike previous studies in the literature, I also explored how the relation between stress and parenting differed for mothers and fathers and across ethnicity (European American and Mexican American parents). Data from 509 parents (150 Mexican American mothers, 150 Mexican American fathers, 105 European American mothers, 104 European American fathers) of fifth graders was collected as part of a three-wave longitudinal data collection entitled Ethnicity, Economic Stress and Adaptation in Families (Parke, 2005). Parents completed surveys, which included questions on economic hardship, economic pressure, life event stressors, coping strategies, family cohesion, and parenting behaviors. Multiple group structural equation modeling was used to assess differences in models across parent gender and ethnicity. Few ethnic or gender related differences were found across the models of stress and parenting which were tested in this study. Family cohesion was found to mediate more strongly between parents\u27 appraisals of stress and parenting behaviors than did family coping strategies. Appraisals of stress were found to be strongly and negatively related to family cohesion, and negatively related to number of coping strategies. Contrary to my hypotheses, coping strategies and family cohesion were related to parenting behaviors in unique ways. Results are discussed in terms of potential research on stress and coping, and applications for professionals working with diverse populations
The meaning of time for reduced -load workers and their families
No full textThe purpose of this study was to investigate the temporal experiences of reduced-load workers and their families. Reduced-load scheduling is a work and family issue. The social institutions of work and family are in flux and are related to other social issues such as gender roles. Gender roles have largely been assumed to follow traditional norms of men working outside the home and women taking primary responsibility for the home. Concepts and experiences of time have been assumed to be Newtonian, linear time. Using grounded theory methodology participants\u27 temporal experiences are explored. Participants use a number of means, such as time management, buying time, and using technology, to address their temporal realities. Time is mostly conceptualized as a commodity for participants, although they do deal with other meanings of time simultaneously. They value control over and flexibility in scheduling their time. Following the actions that families take there are implications that traditional gender roles are in transition
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