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Effect of Follower Forces on Aeroelastic Stability of Flexible StructuresChae, Seungmook 09 July 2004 (has links)
Missile bodies and wings are typical examples of structures that can be represented by beam models. Such structures, loaded by follower forces along with aerodynamics, exhibit the vehicle's aeroelastic instabilities. The current research integrates a nonlinear beam dynamics and unsteady aerodynamics to conduct aeroelastic studies of missile bodies and wings subjected to
follower forces. The structural formulations are based on a geometrically-exact, mixed finite element method. Slender-body theory and thin-airfoil theory are used for the missile aerodynamics, and two-dimensional finite-state unsteady aerodynamics is used for wing aerodynamics. The aeroelastic analyses are performed using time-marching scheme for the missile body stability, and eigenvalue analysis for the wing flutter, respectively. Results from the time-marching formulation agree with published results for dynamic stability and show the development of limit cycle oscillations for disturbed flight near and above the critical thrust. Parametric studies of the aeroelastic behavior of specific flexible missile configurations are presented, including effects of flexibility on stability, limit-cycle amplitudes, and missile loads. The results do yield a significant interaction between the thrust, which is a follower force, and
the aeroelastic stability. Parametric studies based on the eigenvalue analysis for the wing
flutter, show that the predicted stability boundaries are very sensitive to the ratio of bending stiffness to torsional stiffness. The effect of thrust can be either stabilizing or
destabilizing, depending on the value of this parameter. An assessment whether or not the magnitude of thrust needed to influence the flutter speed is practical is made for one
configuration. The flutter speed is shown to change by 11% for this specific wing configuration.
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An Impact Model for the Industrial Cam-follower System: Simulation and ExperimentParadorn, Vasin 28 November 2007 (has links)
"Automatic assembly machines have many cam-driven linkages that provide motion to tooling. Newer machines are typically designed to operate at higher speeds and may need to handle products with small and delicate features that must be assembled precisely every time. In order to design a good tooling mechanism linkage, the dynamic behavior of the components must be considered; this includes both the gross kinematic motion and self-induced vibration motion. Current simulations of cam-follower system dynamics correlate poorly to the actual dynamic behavior because they ignore two events common in these machines: impact and over-travel. A new dynamic model was developed with these events. From this model, an insight into proper design of systems with deliberate impact was developed through computer modeling. To attain more precise representations of these automatic assembly machines, a simplified industrial cam-follower system model was constructed in SolidWorks CAD software. A two-mass, single-degree-of-freedom dynamic model was created in Simulink, a dynamic modeling tool, and validated by comparing to the model results from the cam design program, DYNACAM. After the model was validated, a controlled impact and over-travel mechanism was designed, manufactured, and assembled to a simplified industrial cam-follower system, the Cam Dynamic Test Machine (CDTM). Then, a new three-mass, two-degree-of-freedom dynamic model was created. Once the model was simulated, it was found that the magnitude and the frequency of the vibration, in acceleration comparison, of the dynamic model matched with the experimental results fairly well. The two maximum underestimation errors, which occurred where the two bodies collided, were found to be 119 m/s2 or 45% and 41 m/s2 or 30%. With the exception of these two impacts, the simulated results predicted the output with reasonable accuracy. At the same time, the maximum simulated impact force overestimated the maximum experimental impact force by 2 lbf or 1.3%. By using this three-mass, two-DOF impact model, machine design engineers will be able to simulate and predict the behavior of the assembly machines prior to manufacturing. If the results found through the model are determined to be unsatisfactory, modifications to the design can be made and the simulation rerun until an acceptable design is obtained."
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Det goda ledarskapet : Medarbetares värderingar av positiva ledaregenskaperOlsson, Emelie January 2012 (has links)
Studien bygger på Implicit Leadership Theory, tidigare studiers noterade ledaregenskaper samt egenskaper noterade i denna studie värderade från ett medarbetarperspektiv. Implicit Leadership Theory bygger på hur ledarskap konstrueras av medarbetaren. Deltagare var åtta medarbetare varav tre män. Kvalitativa intervjuer utfördes. Syftet konkretiserades utav önskvärda ledaregenskaper, studiens gemensamma egenskaper och egenskaper överrensstämmande med tidigare studier samt teori. De upplevda egenskaperna delades upp i kategorier som beskrev de önskvärda egenskaperna. Kategorierna var: kommunikativ förmåga, engagemang, kompetens, social kompetens, gruppledaregenskaper samt målinriktad. Resultat visade att ledaregenskaper som är gemensamma för upplevelsen av ett gott ledarskap var lyhördhet, engagemang, att vara driven och att ha en vision. Slutsatsen var att det fanns likheter och skillnader mellan tidigare studiers egenskaper och egenskaperna i denna studie. Skillnader mellan tidigare studiers noterade egenskaper och denna studie var: karisma, effektivitet, etiska värderingar, autonom och prestation. Studien bidrog med att tydliggöra önskvärda ledaregenskaper utifrån ett medarbetarperspektiv.
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The Effects of Transformational and Transactional Leadership on Individual Creative Performance: Role of Follower's Motivation, Identity and Self-esteemKuzmenko, Tetyana 03 1900 (has links)
Leadership behaviors play an important role in followers' performance. In today's competitive world, organizations gain advantage from creativity of their employees. Yet, there has been little research done on the effects of transformational and transactional leadership on followers' creative performance. The present study investigates the relationships between the components of transformational leadership (charisma, intellectual stimulation, and individualized consideration), transactional leadership (e.g. contingent reward behavior) and followers' creative performance. The proposed model examines the role of followers' intrinsic motivation, self-esteem and identity (e.g. personal and collective) in these relationships. While the study's hypotheses were not supported, charisma (β = .39, ρ < .01) and transactional leadership (β = .36, ρ < .05) positively predicted creativity in the absence of any controls. The effect of charisma was not consistent with expectations, though that associated with transactional leadership was. / Thesis / Doctor of Philosophy (PhD)
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Employing an Implicit Task to Measure the Effects of Contextual Constraints on Perceptions of LeadershipBoyd, Kathleen Benton-Snead 03 September 2015 (has links)
A laboratory experiment was conducted to test the effects of follower behaviors (passive or active) and affect (positive or negative) on leadership perception within the context of an implicit association task (IAT). Individuals watched either a positive or negative affect inducing video, were placed in a leader role, and were asked to read a brief scenario detailing the behavior of their followers. The results indicated that: 1) active follower behavior information activated leadership perceptions that reflect an implicit preference for Visionary Leadership, and 2) positive affect activated leadership perceptions that reflect an implicit preference for Visionary Leadership. It was hypothesized that there would be an interaction between follower behavior and leader affect such that negative affect would lead to more detailed follower behavior information processing and therefore follower behavior would have stronger effects on leadership perceptions. The interaction was not significant; however the main effects provide support for the Connectionist Model of Leadership, such that contextual constraints do influence perceptions of leadership. Limitations and future research directions are discussed. / Ph. D.
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Charismatic Leadership Perceptions from K-12 Administrators: Phenomena of Follower and Leader InterdependencyMartinez, Lucinda G 20 December 2017 (has links)
A greater understanding of the nature of leadership can be gained by empirical analyses, such as this quantitative study, addressing the influence executive administrators have on their message recipients, their followers. This study sampled 64 non-teaching K-12 school, district, and state administrators and measured their perceptions of their immediate supervisors’ leadership behaviors by completing the ©Conger-Kanungo Charismatic Leadership Scale (Conger, Kanungo, Menon, & Mathur, 1997) and the ©Perceived Leadership Behavior Measures Inventory (Conger, Kanungo, & Menon, 2000). Analyses of variables measuring perceived leadership behaviors and those effects on the attitudes and perceptions of their followers may contribute to a better understanding of the phenomena of non-teaching administrator follower and leader interdependency in K-12 organizations. Leaders can develop more refined leadership skill characteristics that might enhance ones’ abilities in communicating exemplary characteristics and charismatic behaviors. In turn, these refined abilities can contribute to an organization’s effectiveness by lowering leader and teacher attrition, promoting team building and bonding, and contribute to K-12 administrative leadership development program effectiveness. A General Linear Model with multivariate tests analyses were used to examine correlations between the charismatic leadership behavioral components and the followers’ perceptions of their own motivation, trust, and satisfaction. A significant correlation existed (p =p =
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A Dyadic Approach to Leadership EmergenceMcCusker, Maureen E. 13 July 2015 (has links)
Leadership emergence is best conceptualized as a complex, multi-level process arising from the dynamic interplay of all elements in the process: group members, relations, and context (Day, 2014). This study seeks to simultaneously examine to the role of each in the leadership emergence process by assessing leader and follower traits, their trait similarity, task, behaviors, and the network itself. Using a rotation design, 99 cadets in groups of three completed four tasks with alternating partners and subsequently provided sociometric ratings of each of their group members. Data was analyzed using Exponential Random Graph Modeling, which controls for endogenous group effects. In general, there was a tendency toward nominating others as leaders. High scores on dominance and intelligence predicted leadership emergence, and low scores on dominance predicted follower emergence. The type of task did not affect leadership emergence. Perceived leader behavior unexpectedly reduced the likelihood of nominating another as a leader. Results from this study highlight the importance of studying all components of leadership process and are once step closer toward doing so completely and accurately. / Master of Science
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An Investigation of Incipient Jump in Industrial Cam Follower SystemsBelliveau, Kenneth D 19 August 2002 (has links)
"The goal of this project was to investigate the dynamic effects of incipient separation of industrial cam-follower systems. Typical industrial cam-follower systems include a force closed cam joint and a follower train containing both substantial mass and stiffness. Providing the cam and follower remain in contact, this is a one degree-of-freedom (DOF) system. It becomes a two-DOF system once the cam and follower separate or jump, creating two new natural frequencies, which bracket the original. The dynamic performance of the system as it passed through the lower of the two post-separation modes while on the verge of jump was investigated. A study was conducted to determine whether imperfections in the cam surface, while the contact force is on the brink of incipient separation, may cause a spontaneous switch to the two-DOF mode and begin vibration at resonance. A force-closed translating cam-follower train was designed for the investigation. The fixture is a physical realization of the two-mass mathematical model. Pro/Engineer was used to design the follower train, Mathcad and TK Solver were used to analyze the linkage and DYNACAM & Mathcad were used to dynamically model the system. The system is designed to be on the cusp of incipient separation when run. Experiments were carried out by bringing the system up to jump speed and then backing off the preload to get the system on the cusp of separation. Data were collected at the prejump, slight jump, and violently jumping stages. The time traces show the acceleration amplitudes grow to large peaks when the system is jumping. The frequency spectrum shows the two new natural frequencies growing in amplitude from non-existant in the prejump stage, to higher values in the violently jumping stage. The peak amplitudes of the phenomenon are small in magnitude compared to the harmonic content of the cam. It is concluded that the contribution of the two-DOF system natural frequencies is not a significant factor from a practical aspect. Although the actual jump phenomenon is of concern in high-speed applications, calculations show that if the follower system is designed sufficiently stiff then the two-DOF situation will not occur."
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True North or Traveled Terrain? An Empirical Investigation of Authentic LeadershipTuttle, Matthew D. 17 November 2009 (has links)
Authentic leadership is a new concept that is gaining both popularity and notoriety in the leadership literature. It is argued as a positive form of leadership that goes beyond traditional leadership styles in order to influence followers through genuine, ethical behavior. However, as a concept in its infancy, authentic leadership has yet to receive much empirical attention, and many researchers are skeptical of its value in what is seen as a saturated domain of leadership styles. This study offers a comprehensive approach to addressing this need. A new measure for authentic leadership was developed and validated through pilot testing. Through additional analyses using this new measure, it was discovered that authentic and transformational leadership were not empirically distinct. However, by combining these two measures into an authentic-transformational leadership construct, it was still possible to examine the effect of greater amounts of authenticity in the leadership role. It was found that authentic-transformational leadership was directly related to a number of employee attitudes, and these, in turn, were related to positive employee behaviors. Results of this study are discussed both in terms of future research in the area of authentic-transformational leadership as well as its impact on organizational effectiveness.
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Slide-to-Roll Ratio in Automotive Valve Train Cam and Oscillating Roller FollowerDaniel Jonathan Korn (16407771) 26 June 2023 (has links)
<p>The objectives of this investigation were to experimentally and analytically evaluate the performance of a valve train cam and oscillating roller follower mechanism. Of particular interest was the effect of operating conditions on the slide-to-roll ratio (SRR) of the roller follower. In order to experimentally measure the SRR at the cam-roller contact, a valve train test rig (VTTR) was utilized. The VTTR contained a section of a heavy-duty diesel engine valve train that was instrumented with encoders and Hall effect sensors to measure the camshaft and roller follower angular velocities as a function of operating parameters. To corroborate the experimental with analytical results, a numerical model for the cam and oscillating roller follower was developed. In this modeling approach, the roller angular velocity was determined via a torque balance between the frictional torque of the pin-roller follower and cam-roller follower interfaces. The pin-roller friction was obtained by developing a time-dependent hydrodynamic journal bearing model with variable speed and load. Friction maps were developed for the cam-roller follower interface using a ball-on-disk EHD2 rig to capture the friction behavior across a range of entraining velocities, contact pressures, and SRRs. Additional areas of investigation included thermal effects and wear in the pin-roller contact. Overall, good agreement was obtained between the experimental and analytical roller follower angular velocity, with the normalized RMS errors less than 7%, across all operating conditions investigated. The analytical investigation determined that thermal effects in the pin-roller contact are insignificant for the typical operating conditions. However, it was shown that the pin-roller friction torque is critical in causing roller follower slip, as the SRR greatly increases once the pin-roller friction torque is greater than the cam-roller friction torque. Finally, pin-roller local wear was demonstrated to have detrimental effects on the SRR of the roller follower once a critical wear depth was reached. </p>
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