The present study was designed to determine whether differences exist between frontal tongue thrusters and normal swallowers on tasks or oral stereognosis and two-point discrimination.

<div> <div> <div> <p>As cislunar and outer space exploration regains worldwide popularity, the low-thrust spacecraft technology, whether in the form of solar sails, electric propulsion or nuclear propulsion, has seen a major increase in the last two decades, as new technologies arise that not only seek for a reduction of the size of the spacecraft —and/or the payloads— but also to minimize the cost of spaceflights, while trying to approach further destinations in our solar system. Mission designers are being challenged with the need to develop new strategies to generate rapid and informed initial guesses for low-thrust spacecraft trajectory design, that are easily converged into fully continuous solutions in position, velocity and mass states, in a high-fidelity dynamical model that incorporates the true ephemerides and perturbations of the gravitational attracting bodies acting on the spacecraft as it navigates through space. </p> <p>In an effort to explore further mission options for spacecraft traveling in the lunar vicinity, new interest arises into the problem of constructing a general framework for the initial guess generation of low-thrust trajectories in cislunar space, that is independent of the force models in which the orbits of interest are de ned. Given the efficiency of the low-thrust engines, most vehicles are equipped to perform further exploration of the cislunar space after completion of their primary science and technology demonstrations in orbits around the Moon. In this investigation, a generalized strategy for constructing initial guesses for low-thrust spacecraft traveling between lunar orbits that exist within the context of multiple dynamical models is presented. These trajectories are converged as mass-optimal solutions in lower fidelity model, that are easily transitioned and validated in the higher-fidelity ephemeris model, and, achieve large orbital plane changes while evolving entirely within the cislunar region. </p> <p>The robustness of the initial guess generation of the spacecraft’s path, depends highly on the fidelity of the dynamical model utilized to construct such trajectories, as well as on the numerical techniques employed to converge and propagate them into continuous solutions. Other researchers have extensively investigated novel techniques for the generation of initial guesses for the low-thrust spacecraft trajectory design problem including, but not limited to, patched conics strategies, methodologies for the transformation of impulsive burns into nite burns, the orbit chaining framework and, more recently, artificial intelligence schemes. This investigation develops an adaptive orbit chaining type approach that relies on the energy parametrization of periodic orbits that exist within the context of the circular restricted three-body problem, to construct informed initial guess for the low-thrust spacecraft trajectory.</p> <div> <div> <div> <p>A variety of multiple transfer applications for vehicles traveling between orbits in the cislunar region is explored for a wide range of low-thrust spacecraft with varying thrust acceleration magnitude. The examples presented in this investigation are consistent with the low-thrust parameters of previously own missions that utilized the same propulsion capabilities, such as, the DAWN mission and the Japanese Hayabusa missions 1 and 2. The trajectories presented in this work are optimized for either propellant consumption or time- of-flight in the lower-fidelity model, and later transitioned into a higher-fidelity ephemeris model that includes the gravitational attraction of the Sun, the Earth and the Moon. </p> <p>Two strategies are explored for the transition of trajectories from a lower-fidelity model to the higher-fidelity ephemeris model, both of which are successful in retaining the transfer geometry. The framework presented in this investigation is further applied to the upcoming NASA Lunar IceCube (LIC) mission to explore possible extended mission options once its primary science and technology demonstration objectives are achieved. It is demonstrated in this investigation that the strategies developed and presented in this work are not only applicable to the specific low-thrust vehicles explored, but it is applicable to any spacecraft with any type of propulsion technology. Furthermore, the energy-informed adaptive algorithm is easily transition to generate trajectories in a range of varying dynamical models. </p> </div> </div> </div> </div> </div> </div>

<div>In recent decades the revolutionary possibilities of low-thrust electric propulsion have been demonstrated by the success of missions such as Dawn and Hayabusa 1 and 2. The efficiency of low-thrust engines reduces the propellant mass required to achieve mission objectives and this benefit is frequently worth the additional time of flight incurred, particularly for robotic spacecraft. However, low-thrust trajectory design poses a challenging optimal control problem. At each instant in time, spacecraft control parameters that minimize an objective, typically propellant consumption or time of flight, must be determined. The characteristics of low-thrust optimal solutions are often unintuitive, making it difficult to develop an <i>a priori</i> estimate for the state and control history of a spacecraft that can be used to initialize an optimization algorithm. This investigation seeks to develop a low-thrust trajectory design framework to address this challenge by combining the existing techniques of orbit chaining and direct collocation. Together, these two methods offer a novel approach for low-thrust trajectory design that is intuitive, flexible, and robust.</div><div><br></div><div>This investigation presents a framework for the construction of orbit chains and the convergence of these initial guesses to optimal low-thrust solutions via direct collocation. The general procedure is first demonstrated with simple trajectory design problems which show how dynamical structures, such as periodic orbits and invariant manifolds, are employed to assemble orbits chains. Following this, two practical mission design problems demonstrate the applicability of this framework to real world scenarios. An orbit chain and direct collocation approach is utilized to develop low-thrust transfers for the planned Gateway spacecraft between a variety of lunar and libration point orbits (LPOs). Additionally, the proposed framework is applied to create a systematic method for the construction of transfers for the Lunar IceCube spacecraft from deployment to insertion upon its destination orbit near the Moon. Three and four-body dynamical models are leveraged for preliminary trajectory design in the first and second mission design applications, respectively, before transfers are transitioned to an ephemeris model for validation. Together, these realistic sample applications, along with the early examples, demonstrate that orbit chaining and direct collocation constitute an intuitive, flexible, and robust framework for low-thrust trajectory design. </div>

Mylonitic rocks of the Shoo Fly Complex form a region of epidote-amphibolite grade quartzose and granitoid gneiss, subordinate schist and calcareous rocks, and rare amphibolite in the foothills of the Sierra Nevada range in central California. The Shoo Fly has endured a complicated Phanerozoic structural development involving seven superposed deformations at variable crustal depths. The first four of these (D1-D4) involved tight to isoclinal folding and shearing under medium grade metamorphic conditions. The last three (D5-D7) are marked by open folding and retrograde metamorphism of older fabric elements. The Shoo Fly is in ductile fault contact with east-dipping argillite, chert, and marble of the Calaveras Complex. The Calaveras-Shoo Fly thrust formed during D3 and is a 1-2 km wide syn-metamorphic ductile shear zone. Recognition of D3 overprinting of older Dl+D2 fabrics along the thrust zone indicates that upper plate Shoo Fly rocks record an earlier and more complex structural history than the lower plate Calaveras rocks. Paleozoic gneissic granitoids, an important lithologic component of the Shoo Fly, were intruded as a series of plutons ranging from calc-alkaline gabbro to granitoid (predominate) to syenite. They truncated the early S1 foliation in the Shoo Fly and were folded during regional D2 and D3 events when they were penetratively deformed into augen gneiss, blastomylonite, and ultramylonite. The Sonora dike swarm occurs as an areally extensive (> 1500 km2) subvertical consanguineous suite of andesite, lamprophyre, and basalt dikes that trend east-west across the Calaveras and Shoo Fly Complexes. The metamorphic complexes form the basement to a middle Jurassic calc-alkaline plutonic arc (Jawbone granitoid sequence). A middle Jurassic K-Ar age on the dikes (157-159 m.y.) together with the data of this report indicate that they are petrogenetically related to the Jawbone granitoid sequence and that the dikes probably formed during subduction beneath a continental arc. The dikes provide an important structural marker in the Shoo Fly and Calaveras Complexes. Intrusion of the dike swarm was sensitive to a structural anisotropy in the basement complexes. Since they intruded east-west along a spaced regional schistosity developed during folding of the Calaveras-Shoo Fly thrust, thrusting and subsequent folding were clearly pre-middle Jurassic events. Available geochronologic data sets middle Ordovician to late Devonian intrusive ages for the gneissic granitoids, establishing a pre-late Devonian depositional age for the Shoo Fly. D1 and intrusion of the orthogneiss protoliths may have been precursors of the Late Devonian to Early Mississippian Antler orogeny or, alternatively, may have occurred significantly earlier than the Antler orogeny. Based on cross-cutting relations, D2 formed during the Antler orogeny, D3 and possibly D4 during the Sonoma orogeny, and D5 and D6 during the Nevadan orogeny.

No description available.

No description available.

The kinematic evolution and along-strike variation in contractional deformation in overthrust belts are poorly understood, especially in three dimensions. The Sevier-age Cordilleran overthrust belt of southwestern Wyoming, with its abundance of subsurface data, provides an ideal laboratory to study how this deformation varies along the strike of the belt. We have performed a detailed structural interpretation of dual vergent thrusts based on a 3D seismic survey along the Wyoming salient of the Cordilleran overthrust belt (Big Piney-LaBarge field). The complex evolution of the thrust faults that parallel the overthrust belt is demonstrated by the switching of the direction of thrust fault vergence nearly 180° from east to west. The variation in thrust-fault geometry suggests additional complexities in bulk translation, internal strains, and rotations. The thrust zone is composed of two sub-zones, each with an opposing direction of fault vergence, located on the eastern toe of the Hogsback thrust in southwestern Wyoming. The northern west-vergent thrust is a wedge thrust and forms a triangle zone between its upper thrust plane and the lower detachment that has formed in a weak shale layer (the Cretaceous K-Marker bed). Thrusts to the south have a frontal ramp geometry and are consistent with the overall thrust orientation of the Cordilleran overthrust belt located immediately to the west. The two thrust sub-zones are small, relative to the main Hogsback thrust to the west, and adjacent to each other, being separated by a transfer zone measuring in the hundreds of meters along strike. The transfer zone is relatively undisturbed by the faults (at the scale of seismic resolution), but reflections are less coherent with some very small offsets. The thrusts are thin-skinned and located above a shallow-dipping single detachment (or décollement) that is shared by faults in both sub-zones. Lateral growth of the thrust faults link along strike to form an antithetic fault linkage. Structural restoration of thrust faults shows varied amounts of shortening along strike as well as greater shortening in stratigraphic layers of the west-vergent fault to the north. Results from a waveform classification and spectral decomposition attribute analysis support our interpretations of how the variations in the detachment may govern the structural development above it. The kinematic evolution of the dual-verging thrust faults is likely controlled by local pinning within the transfer zone between the thrust-fault sub-zones as well as by changes in the competence of the strata hosting the detachment and in the thickness of the thrust sheet. The analysis and interpretation of dual-vergent thrust structures in the Cordilleran overthrust belt serve as an analog to better understand complex fold, fault, and detachment relations in other thrust belts.

M. S.

Introduktion: Ländryggssmärta är en av de vanligaste åkommorna och är en anledning till att individer söker kontakt med vården. Forskning visar att personer med ländryggssmärta har en annorlunda EMG-amplitud (muskelaktivering) samt rekryteringsordning jämfört med personer utan ländryggssmärta. Syfte: Syftet med denna studie var att jämföra EMG-amplitud samt rekryteringsordning av rygg- och höftextensorer hos personer med eller utan ländryggssmärta vid utförande av övningen hip thrust. Metod: Sex stycken deltagare varav tre stycken med ländryggssmärta och tre stycken utan ländryggssmärta deltog i studien. Deltagarna utförde övningen hip thrust samtidigt som man mätte EMG från gluteus maximus, erector spinae och semidentinousus. Insamling av data gjordes med Noraxon, utfallsvariabler som jämfördes mellan grupperna var EMG-amplitud och rekryteringsordning. Resultat: De med ländryggssmärta hade en annorlunda rekryteringsordning med större variation jämfört med personer utan ländryggssmärta. Det var även en variation i EMG-amplituden mellan grupperna där deltagare med ländryggssmärta hade en högre aktivering av semitendinosus jämfört med kontrollgruppen vid utförande av övningen hip thrust. Konklusion: Personer med ländryggssmärta har en avvikande EMG-amplitud samt rekryteringsordning av rygg-och höft-extensorer jämfört med personer utan ländryggssmärta vid utförande av en hip thrust. Resultatet av denna studie kan endast påvisa att det finns en skillnad av EMG-amplitud samt rekryteringsordning mellan personer med ländryggssmärta jämfört med utan. En slutsats kan ej göras om ländryggssmärtan är den bakomliggande orsaken till detta. Vidare forskning inom området behöver göras med metodologiska förändringar för att förstärka resultatet av studien.

Compound aerospike nozzles were designed and tested as part of an ongoing experimental study to determine the feasibility of thrust vectoring an aerospike nozzle with the addition of a secondary port. Earlier phases of the study have indicated that a compound aerospike nozzle could provide sufficient thrust vectoring. The addition of a hole-type secondary port was found to provide effective thrust vectoring. Experiments were carried out to determine the effects of secondary port size, secondary port inlet geometry and compound aerospike nozzle chamber pressure. Results show good predictability, axisymmetric flow, and emphasize the importance of a radius on secondary port inlet geometry.