<p>Individer med hög prestationsbaserad självkänsla (pbs) har visat sig löpa ökad risk att drabbas av bland annat utbrändhet. Studien undersöker pbs longitudinellt bland förvärvsarbetande som deltog i SLOSH (Swedish Longitudinal Occupational Survey of Health) 2006 och följdes upp 2008. Syftet var att undersöka prevalens av pbs i olika grupper och dess stabilitet över tid samt om tjänsteposition predicerar graden av pbs, alternativt om pbs predicerar en hög tjänsteposition. Resultatet visade att pbs har en stor nedgående tendens och en måttlig stabilitet. Arbetare och de med oförändrad tjänsteposition skilde sig signifikant från de andra personalkategorier respektive tjänstepositioner. Chefskap predicerade en hög pbs två år efter baslinjen medan en hög pbs vid baslinjen predicerade en högre tjänsteposition två år senare. Sambandet mellan pbs och tjänsteposition bör belysas för att på organisationsnivå förebygga och åtgärda stressrelaterade sjukdomar.</p>

Individer med hög prestationsbaserad självkänsla (pbs) har visat sig löpa ökad risk att drabbas av bland annat utbrändhet. Studien undersöker pbs longitudinellt bland förvärvsarbetande som deltog i SLOSH (Swedish Longitudinal Occupational Survey of Health) 2006 och följdes upp 2008. Syftet var att undersöka prevalens av pbs i olika grupper och dess stabilitet över tid samt om tjänsteposition predicerar graden av pbs, alternativt om pbs predicerar en hög tjänsteposition. Resultatet visade att pbs har en stor nedgående tendens och en måttlig stabilitet. Arbetare och de med oförändrad tjänsteposition skilde sig signifikant från de andra personalkategorier respektive tjänstepositioner. Chefskap predicerade en hög pbs två år efter baslinjen medan en hög pbs vid baslinjen predicerade en högre tjänsteposition två år senare. Sambandet mellan pbs och tjänsteposition bör belysas för att på organisationsnivå förebygga och åtgärda stressrelaterade sjukdomar.

The Utah State University Propulsion Research Laboratory (USUPRL) has recently made significant developments in the area of hybrid rocket systems. This type of propulsion system incorporates a solid fuel and a gas or liquid oxidizer. Hybrid rocket systems are known for their inherent safety, reliability, and restart capability. Over the last several years, the USUPRL has successfully built and tested a hybrid rocket system comprising acrylonitrile butadiene styrene (ABS) plastic and gaseous oxygen (GOX). The system was demonstrated to be fully functional during ground, vacuum, and sub-orbital flight testing. Continuing forward, the USUPRL endeavors to extend the capabilities of this hybrid rocket system to in-space propulsion applications, such as an attitude control systems (ACS). This thesis investigates the feasibility of using the USU Green Hybrid Rocket as an ACS for an intermediate-sized launch vehicle. A computer simulation was developed to demonstrate the control and stability of the spacecraft under the influence of the ACS.

No description available.

<p>The aim of the thesis has been to study methods to minimize the slosh when moving liquid-filled packages in packaging machines. An automatic method for generation of the movement of a package in a packaging machine is of growing importance. The main reason is that reduced slosh leads to increased production rate. Progress within measurement technology creates possibilities for new solutions. One purpose has been to find methods and equipment to detect the height of the wave, perhaps at several places or alternatively the entire liquid surface shape. When suitable equipment for detection of the wave movements was found, collected measurements were analyzed and criteria for describing improvements of the slosh properties have been formulated. </p><p>Initially a sensor specification was written in order to simplify the search for suitable equipment. Sources of information have mainly been catalogues and Internet. The search resulted in that a number of sensors were borrowed for tests. The results of the tests supported the choice of the most suitable sensor, in this case a laser sensor. The main reason is that the sensors detection ability is good compared to its price. An analysis of the sensors most important properties confirmed the choice of the laser sensor. To be able to compare waves, criteria for what is considered to be good wave properties have been formulated and evaluated. </p><p>The work has confirmed that it is difficult to find a simple and cheap solution for wave detection given that the solution should have good detection ability. It has also been difficult to formulate simple but working criteria for wave performance, and this has led to a compromise between the complexity of the criterion functions and the result of the wave score. Ideas about how an automatic method, based on the chosen sensor and the criterion functions, can be implemented, have been introduced. During the work, some interesting discoveries have been made. These have led to better understanding of how some parameters should be chosen, to better understanding of wave movements and to better choice of future work.</p>

The aim of the thesis has been to study methods to minimize the slosh when moving liquid-filled packages in packaging machines. An automatic method for generation of the movement of a package in a packaging machine is of growing importance. The main reason is that reduced slosh leads to increased production rate. Progress within measurement technology creates possibilities for new solutions. One purpose has been to find methods and equipment to detect the height of the wave, perhaps at several places or alternatively the entire liquid surface shape. When suitable equipment for detection of the wave movements was found, collected measurements were analyzed and criteria for describing improvements of the slosh properties have been formulated. Initially a sensor specification was written in order to simplify the search for suitable equipment. Sources of information have mainly been catalogues and Internet. The search resulted in that a number of sensors were borrowed for tests. The results of the tests supported the choice of the most suitable sensor, in this case a laser sensor. The main reason is that the sensors detection ability is good compared to its price. An analysis of the sensors most important properties confirmed the choice of the laser sensor. To be able to compare waves, criteria for what is considered to be good wave properties have been formulated and evaluated. The work has confirmed that it is difficult to find a simple and cheap solution for wave detection given that the solution should have good detection ability. It has also been difficult to formulate simple but working criteria for wave performance, and this has led to a compromise between the complexity of the criterion functions and the result of the wave score. Ideas about how an automatic method, based on the chosen sensor and the criterion functions, can be implemented, have been introduced. During the work, some interesting discoveries have been made. These have led to better understanding of how some parameters should be chosen, to better understanding of wave movements and to better choice of future work.

Two topics relating to low gravity fluid behavior in satellite propellant tanks are considered. In the first, static case, the problem of liquid trapping is examined. Satellite propellant tank end caps optimized for weight are generally shallower and more oblate than hemispherical end caps of the same radius. However, these shallower end caps pose an interesting challenge for propellant management. In the absence of vanes, it is possible for liquid propellant to be trapped in the tank and become unusable. Understanding of how propellant tends to distribute itself in the bare, vaneless tank can be used to drive vane design to counteract these tendencies and ensure propellant remains where desired. The first section of this thesis aims to demonstrate methods that can be used to identify when, how, and why liquid trapping occurs in a given tank geometry. A fluid statics code called Surface Evolver is used to calculate possible fluid configurations for different propellant volumes, contact angles, and end cap designs. The specific case of a cylindrical tank with 2:1 ellipsoidal end caps is studied extensively for ranges of fill fractions and contact angles to illustrate the methods used. Results are computed for each possible propellant configuration: a spherical liquid-gas interface, an asymmetric liquid-gas interface, and a liquid ring. Analytical solutions are found and compared against Surface Evolver results for the spherical liquid-gas interface and liquid ring, showing excellent agreement. Results are also found for other aspect ratio ellipsoidal end caps, superellipsoidal end caps, and torispherical end caps. Each non-hemispherical dome design is found to be able to trap liquid away from the axis of the tank regardless of contact angle. The second part of this thesis, focusing on the dynamic case, details the development of an experimental payload designed to fly on Virgin Galactic’s SpaceShipTwo. This experiment is designed to obtain data on sloshing behavior of liquids in microgravity in response to rotation. The payload contains eight scaled down propellant tanks that are rotated while in microgravity, and the resulting slosh is recorded by video cameras inside the payload. The video will be analyzed after the experiment to extract data on damping rates and potentially positional data of the liquid-gas interface. The impact of constraints on the design of the overall experiment are discussed. The purpose of each component in the experiment is explained and justified relative to the design constraints. The remaining work that must be completed before flight on SpaceShipTwo is reviewed, highlighting the most significant unknowns.<br>

No description available.

Command shaping creates reference commands that reduce residual vibrations in a flexible system. This thesis examines the use of command shaping for flexible system control in three industrial applications: cam-follower systems, sloshing liquids, and cherrypickers. One common type of command shaping is command smoothing which creates a smooth transition between setpoints. A specific type of command smoothing used in cam-follower systems is the polynomial profile. An alternative technique to reduce vibration in flexible systems is input shaping. In this thesis, input-shaped commands are compared to polynomial profiles for applications requiring both vibration suppression and fast motion. Simulation and experimental results show that input shaping is faster than polynomial profiles and provides a simple approach to suppressing residual vibration. Secondly, significant experimental contributions have been made in the area of slosh control. The oscillation of liquids in a container can cause liquid spillage or can cause stability issues, especially in space vehicles. In the past, a number of control techniques have been proposed, but only a few recommend the use of input shaping. This thesis describes the use of command shaping to limit slosh. Results are supported by numerical and experimental testing. Input-shaped commands reduce residual slosh amplitude compared to unshaped commands and polynomial profiles. Input-shaped commands can also accommodate uncertainties and changes in the sloshing frequencies. Lastly, a small-scale cherrypicker was constructed to study the use of input-shaping control on these types of aerial lifts. Cherrypickers have flexible dynamic effects that can cause dangerous and life-threatening situations. To study this class of machines and to provide future students an experimental testbed, several design criteria were established before construction began. The resulting machine achieved most design objectives, including a simple-to-use graphical user interface and accurate state measurements. Robust input-shaping controllers were implemented to limit endpoint vibration. The design of the cherrypicker is discussed and experimental results are reported.

<div>As small satellites are increasingly used in the space industry, creative solutions for the use of their limited volume will be required. Conformal tanks are one idea to better make use of this volume. These tanks are non-traditionally shaped and non-axisymmetric. Because slosh can have detrimental effects on a spacecraft, it should be understood. However, slosh in these more complicated geometries has not been thoroughly investigated in the past.</div><div><br></div><div>This research looks at slosh within six geometries, five of which are conformal tanks. These geometries are evaluated in both an experiment and using CFD simulations. It was found that the total slosh motion appears to be the sum of slosh behavior along each dimension. Slosh along a line of symmetry will have center of mass movement that stays along that line. Slosh off the line of symmetry will deviate from that line unless slosh frequency is the same in each direction.</div>