The effectiveness of a double-stem injection valve in controlling combustion in a compression-ignition engine

An investigation was made to determine to what extent the rates of combustion in a compression-ignition engine can be controlled by varying the rates of fuel injection. The tests showed that the double-stem valve operated satisfactorily under all normal injection conditions; the rate of injection has a definite effect on the rate of combustion; the engine performance with the double-stem valve was inferior to that obtained with a single-stem valve; and the control of injection rates permitted by an injection valve of two stages of discharge is not sufficient to effect the desired rates of combustion

Environmental effects on polymeric matrix composites

Current epoxy resins utilized in high performance structural composites absorb moisture from high humidity environments. Such moisture absorption causes plasticization of the resin to occur with concurrent swelling and lowering of the glass transition temperature. Similar effects are observed in composites. Data are presented showing the effects of absorbed moisture on Hercules AS/3501-5 graphite/epoxy composites. Prediction of moisture content and distribution in composites, along with reduction in mechanical properties, are discussed

Examining the Longitudinal Effects of the PE Class' Climate on Students' Goal Orientations and Intrinsic Motivation to be Physically Active

Nicholls' Achievement Goal Perspective Theory (AGPT) research has been examined within the PE and sport domains (Roberts & Treasure, 2012). However, very limited longitudinal research has been conducted, particularly with youth and adolescents. Research is needed to examine the impact of the PE motivational class climate on students' goal orientations toward PE and intrinsic motivation to be physically active. The first study assessed a professional development (PD) session with a school district's PE teachers focused on maximizing their development of a caring and task-involving climate. The effect of this session was assessed by comparing the secondary students' perceptions of the motivational climate for two semesters prior to the PD with student perceptions the semester immediately after the PD. Three important findings were revealed by analyzing each teacher's (N=8) multi-group SEM: a) significant effects from the PD were not found, b) experienced, individual PE teacher's motivational climate development is very consistent over time, and c) 75% of the teachers' models showed no significant correlation between intrinsic motivation and ego-involving climate perceptions. Together these results suggest that future PD for current PE teachers should emphasize ways to enhance the caring and task-involving climate, because these aspects were consistently correlated with the students' reported intrinsic motivation to be physically active. The second study tracked sixth grade students into their first seventh grade semester. The purpose of this study was to examine the influence of the seventh grade PE class climate on students' goal orientations, competence, and effort in PE. Enrolled PE students (N=376) were surveyed twice in sixth grade, and twice the following fall semester (N=216). Importantly, significant, positive within time correlations were found between the students' perceptions of the caring climate and their PE competence, effort, and task goal orientation adoption. The majority of the within time correlations were constrainable across the four time-points. This preliminary finding suggests that when students perceive a caring climate, they are also more likely to report greater competence, effort, and task orientation in PE. The findings support that these outcome variables are uniquely related to caring climate above and beyond their relationships with the task-involving climate

Developing a Caring Coaching Climate Fosters Confidence

When athletes buy-in to a positive training climate their training effort, enjoyment, and desire to continue all increase. This article focuses on practical approaches coaches can use today to promote a safe, personalized, and respect-filled atmosphere – integral building blocks for developing a successful caring climate

Planned Missingness Study Design: Two Methods to Developing the Study Survey Versions

A planned missingness data study design takes advantage of modern techniques for handling data missingness that is MCAR (Missing Completely at Random) and MAR (Missing at Random) (Brown, 2006; Enders, 2010). As modern data imputation techniques have improved, this study design option has become a powerful, cost-effective option for collecting the most data across the largest sample possible, while keeping the fatigue effect and expense of the study minimized (Little, 2010a, 2010b, 2012). The purpose of this guide is to provide an applied example for designing the surveys necessary when conducting a planned missingness research study design

Developing Youth\u27s Positive View of Physical Activity

Many youth start withdrawing from voluntary physical activity and physical education programs as they approach adolescence. Developmentally, this is also when youth can become more aware of their ability compared to others, and the amount of work it may take to improve their ability level. This focus on comparative performance standards can be affected by our coaching emphasis. This article highlights the characteristics and impacts of two coaching approaches. Particular emphasis is given to the specific behaviors adolescents have reported as fostering their effort, enjoyment, sportspersonship, and interest in continuing to be active

Construct-Validity of the Engagement with Challenge Measure for Adolescents: Structural- and Criterion-Validity Evidence

For adolescents, engaging with challenge is a key developmental task, hypothesized to support development of adult-like competencies (e.g., agency and self-direction; Larson, 2000). This study aimed to assess the construct-validity (structural- and concurrent-validity) of a new self-report measure assessing adolescents’ engagement with challenge to help researchers understand how different settings and the conditions in these settings support adolescents’ development. The sample consisted of 337 adolescents in 10 FFA programs along with the adult advisors in each program. Adolescents completed a questionnaire, which included the Engagement with Challenge measure and the following criterion variables: number of contests completed, participation frequency, and leadership roles. In addition to the self-reported criterion variables, the adult advisor evaluated Engagement with Challenge for each FFA student member in that program using a single item. The findings of this study provided strong evidence for the structural-validity of the engagement with challenge construct measured by the new scale, including having passed confirmatory factor analysis configural, weak, and strong invariance tests across four grade groupings. The findings also provided further evidence of construct-validity, as Engagement with Challenge correlated in the a priori hypothesized direction and magnitude. Suggestions for analysis with the new measure and for future research are presented

Strategies to Increase Athletes\u27 Transformational Leadership Behaviors During Strength and Conditioning Sessions

Often, leadership is presumed to naturally result from athletic experiences. However, leadership behaviors require practice. Strength and conditioning coaches (SCCs) can provide opportunities for all athletes to practice transformational leadership behaviors, which can increase team cohesion and performance. This article reviews athlete leadership, including leadership roles and four transformational leadership behaviors (idealized influence, inspirational motivation, individualized consideration, and intellectual stimulation). Then, daily strategies SCCs can incorporate into training to foster athletes’ transformational leadership are presented. Followed by strategies for larger, rotating leadership experiences. These strategies can work with athletes across age, gender, and competitive level