Search

Knowledge of lubricant and refrigerant miscibility is necessary for the optimaldesign and function of compressors in refrigeration systems. Without adequate knowledge of mixture miscibility, compressor lubricants can drift into refrigerant systems, fail to return to the compressor and cause build-up in the pipes. This entrapped lubricant will reduce the systems efficiency by lowering the heat transfer coefficient of the system and introducing flow irregularities. To obtain data on refrigerant and lubricant miscibility a pressure vessel needed to be designed and manufactured. This pressure vessel needed to withstand a working pressure of 150 bar, a temperature range of -40 C to 160 C, and have an integrated mixer. ASME, ISO, and ASHRAE standards were referenced in the design of this vessel to ensure proper function and safety. Stress and displacement simulations were conducted using SolidWorks to help inform the final design. Additionally, ANSYS and COMSOL were leveraged for fluid mixing simulations to determine optimal mixing impeller design for our system. The rushton and hydrofoil impellers showed the greatest eddy diffusivity and mixing potential. Overall, this work has produced a functioning pressure vessel, a system for temperature regulation of the pressure vessel, and a proposed method to obtain lubricant and refrigerant miscibility data.

Purpose: Adolescent substance initiation is associated with adverse health and may place youth on a negative life trajectory. Designing effective prevention programs may be the key to decreasing early adolescent substance initiation in the US. Alcohol and cigarette initiation are of particular concern because use of these substances is normative. The present study aimed to identify factors associated with adolescent alcohol and cigarette initiation by evaluating three conceptual models: a risk model (objective social status, subjective social status, and perceived discrimination), promotive model (family cohesion, parental monitoring, parental nurturance, and peer support), and protective model (potential risk and promotive factors).Method: Data were from 4,824 participants in the Healthy Passages study, a population-based prospective longitudinal survey of diverse U.S. adolescents in fifth, seventh, and tenth grade. Self and parent-report items and scales were used to measure alcohol and cigarette initiation and hypothesized risk and promotive factors. A series of multinomial logistic regression tests were conducted for each conceptual model separately by racial/ethnic group. All analysis controlled for child’s age, gender, and parental cigarette and alcohol use, perceived peer alcohol and cigarette use. Results: The promotive factors of family cohesion, parental nurturance, parental monitoring, and peer support were associated with decreased initiation of both alcohol and cigarette use, which varied slightly by racial/ethnic group. Notably, parental nurturance and family cohesion were consistent among all racial/ethnic group and across alcohol and cigarette initiation. Among the variables examined, there were no significant risk factors detected in this 5-year prospective longitudinal study and thus there was no support for a protective model. Conclusion: Promotive factors, especially family cohesion and parental nurturance, remained consistent in being associated with reduced alcohol and cigarette initiation. Thus, prevention programs aimed at early adolescence may be most fruitful by focusing on enhancing these promotive factors.

Stressful life events (SLEs) increase allostatic load and require adaptation. Experiencing SLEs has been associated with decreased health-related quality of life (HRQOL) among adolescents. This study examined racial/ethnic and developmental differences in the relationship between SLEs and HRQOL from preadolescence to mid adolescence. Data were from 4,824 participants in the Healthy Passages project, a population-based prospective longitudinal survey of fifth, seventh, and 10th grade adolescents in the U.S. HRQOL was measured with Pediatric Quality of Life Inventory and SLEs with items addressing family-related SLEs (e.g., the parent’s death, separation, and divorce; family member’s injury/illness; residential change; new child in the household). Adolescents, regardless of race/ethnicity, reported the highest SLEs and the lowest HRQOL in early adolescence. Analysis of an autoregressive model with cross-lagged effects showed that the concurrent relationships between SLEs and HRQOL were significantly negative across preadolescence, early adolescence, and mid adolescence in African-American, Latinx, and white groups. Furthermore, adolescents had a negative cross-lagged association from SLEs in early adolescence to HRQOL in preadolescence, but this was not the case among the other racial/ethnic groups. Because the negative relationship between family-related SLEs and HRQOL persisted throughout stages of adolescent development, health services targeting adolescents should provide comprehensive family-centered care to alleviate the impact of family-related life stress. Relationships between family life stress and HRQOL varied by racial/ethnic groups, which should be considered by health professionals, teachers, and parents, and in prevention efforts. Latinx adolescents may be particularly vulnerable to time-lagged effects of such family-related stress.