My work focused on the study of road effects and mitigation of negative impacts of roads on wildlife. Two different studies were conducted on Interstate 15, in southern Utah. My first study reported on road effects on small mammal communities. The results suggested that overall, there was no clear effect on small mammal populations relative to distance from the road. Most small mammal species did not appear to be negatively affected by the presence of the road. Instead, the road seemed to have either a neutral or a positive effect. The abundance and diversity of small mammals responded more markedly to microhabitat than to the presence of the highway. I suggest that other factors such as water runoff during rainy periods may be responsible for the detected patterns by increasing primary productivity in areas close to the road. I conclude that roads may often provide favorable micro-habitat in the desert landscape for many small mammals and that the disturbance caused by the highway use (e.g., noise, road surface vibration) seemed to have a negligible effect on these organisms . My second study examined the effectiveness of a mitigation strategy to reduce mule deer (Odocoileus hemionus) road mortality. Mitigation included exclusion fencing, earthen escape ramps, and underpass crossing structures . Results comparing mortality data before and after the mitigation showed 76-96% reductions of deer vehicle collisions. There was no evidence that the mitigation caused "end-of-the-fence" problems, i.e., higher mortality at the ends of the exclusion fencing . Results from underpass camera monitoring showed an increasing deer use of the underpasses over time. The volume of crossings recorded on new underpass structures approached the volume of crossings observed in a 20-year-old control underpass. My results suggest that human use and location of structures influenced deer use of underpasses. Overall results show that the mitigation strategy was effective and has reduced the number of deer-vehicle accidents while allowing easier wildlife movement across the landscape. I presented future maintenance recommendations to assure a long-term success for this strategy.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20161号 / 理博第4246号 / 新制||理||1611(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 高橋 義朗, 教授 田中 耕一郎, 教授 川上 則雄 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第21918号 / 情博第701号 / 新制||情||120(附属図書館) / 京都大学大学院情報学研究科システム科学専攻 / (主査)准教授 西原 修, 教授 大塚 敏之, 教授 加納 学 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

This thesis work investigated the advantages and disadvantages of using superquadrics (SQ) to do the collision-checking part of the Rapidly-exploring Random Trees (RRT) motion planning algorithm for higher Degree of Freedom (DoF) motion planning, comparing it with an established proximity querying method known as the Gilbert-Johnson-Keerthi (GJK) algorithm. In the RRT algorithm, collision detection is the main bottleneck, making this topic interesting to research. The SQ-based collision detection method was compared to the GJK algorithm both qualitatively and quantitatively, comparing computational speed, memory requirements, as well as the ability to handle arbitrary shapes. Furthermore, how appropriate they are in modelling a 6 DoF arm was analyzed. A qualitative comparison between the RRT algorithm and the A* algorithm was also provided, comparing their suitability for searching in higher dimensional spaces. When there were no collisions the SQ-based algorithms performed roughly at parity with the GJK algorithm in terms of computational speed. However, when a collision had occurred, the SQ-based algorithms were able to return a positive faster than the GJK algorithm, outperforming it. From a memory standpoint the SQ-based algorithms required less memory as they could leverage the explicit and implicit representations of the SQ objects, whereas the GJK algorithm requires both objects being checked for collision to be explicitly represented as convex sets of points. Regarding handling arbitrary shapes, the SQ-based algorithms have an advantage in that they can allow for certain non-convex shapes to be. Conversely, the GJK algorithm is limited to convex shapes. The GJK algorithm would thus require more geometric primitives to accurately capture the same non-convex shape. Thus, it can be concluded that the SQ-based method is more suitable for modelling a 6 DoF arm. However, a GJK-based collision detection module would in most cases be a lot more straightforward than the alternative to set up, as it is very simple to collect a set of points. Finally, both collision detection method types were implemented with the RRT algorithm. Due to the inherently random nature of the RRT algorithm the results of this set of tests could not be used to make any further conclusions beyond showing that it is possible to combine the SQbased algorithm with the RRT algorithm. Instead, one should see the RRT algorithm as a multiplicative factor applied to the inherent properties of the previously examined collision detection methods. / Detta examensarbete undersökte fördelarna och nackdelarna med att använda n:tegradsytor (NY) för att utföra kollisionsdetektion i algoritmen Raskt-utforskande Slumpmässiga Träd (RST). RST används typiskt för planeringen av system med relativt många frihetsgrader. En etablerad metod för kollisionsdetektion, Gilbert-Johnson-Keerthi-algoritmen (GJK), implementerades även i jämförelsesyfte. Då GJK-algoritmens största flaskhals ligger i kollisionsdetektionen är detta ett intressant ämne att efterforska. Den NY-baserade kollinsdetektionsmetoden jämfördes med den GJK-baserade metoden både kvantitativt och kvalitativt. Kvalitativt jämfördes beräkningshastighet och minnesåtagande, medan de kvalitativt jämfördes i deras förmåga att representera godtyckliga geometriska former. På ett högre plan diskuterades det även hur lämpliga de är för att modellera en robotarm med 6 stycken frihetsgrader. RST-algoritmen jämfördes även med en annan planeringsalgoritm, A*. Framförallt fokuserade diskussionen kring planering av system med relativt många frihetsgrader. I det fall inga kollisioner fanns presterade GJK-algoritmen ungefär lika bra som NY algoritmerna i att fastslå detta, utifrån beräkningshastighet. Men när det kom till att upptäcka existerande kollisioner presterade GJK-algoritmen sämre. Minnesmässigt använder GJK-algoritmen mer minne, då den kräver att båda objekten är explicitrepresenterade (dvs, som ett punktmoln), medan man med en NY-metod endast behöver representera ena objektet explicit och den andra implicit. Gällande förmågan att representera godtyckliga geometriska former är NY-baserade metoder bättre. Till skillnad från GJK som är begränsad till konvexa mängder kan NY uppta ickekonvexa former, exempelvis flottyrmunkformade supertoroider. En metod som använder GJKalgoritmen skulle behöva bygga upp icke-konvexa former med flera mindre konvexa komponenter. NY-metoden är således bättre för att modellera robotarmar med 6 frihetsgrader. Det är dock i praktiken lättare att implementera GJK-metoden då den endast kräver punktmoln, medan NY kräver parametrar som måste bestämmas eller finjusteras. RST-algoritmen implementerades sist, utformad så att kollisionsdetektionsmetoderna är utbytbara. Det var dock inte möjligt att dra slutsatser utifrån det testdata som erhölls, ty RSTalgoritmens slumpmässiga karaktär. RST-algoritmen kan ses som en multiplikator som endast förstorar de inneboende egenskaperna hos kollisionsdetektionsmetoderna.

One commonly used representation of complex objects in physics-based simulations are triangle meshes. This representation utilizes a collection of triangles to approximate an object. An alternative representation is a Signed Distance Field (SDF). This thesis aims to evaluate the effectiveness of representing a heavy machine bucket as an SDF, specifically in the application of collision detection with a de-formable terrain. Additionally, this thesis describes the implementation of two collision detection routines which uses SDFs to detect collisions with spheres and heightfields. The SDFs are stored using two alternative spatial data structures, a uniform grid and an octree. The implementations are compared against a triangle mesh representation. While there are limitations to the SDF representation, such as the need for high resolutions to capture fine details or that small features may become heavily distorted, the benefits of using SDFs include the ability to perform point to distance queries and provide a robust description of an object’s interior and exterior. The findings of this study showed that the SDF stored in a uniform grid demonstrated better performance in the benchmarks and was able to reproduce comparable data to the triangle mesh in the digging tests. These results indicate that the SDF representation could be a promising alternative to the triangle mesh representation. However, further development and research are required.

This thesis covers the development process of implementation, and evaluation of a softbody physics engine for convex polygon objects. The main feature is implementation of adynamic polygon collider that represents a polygons shape correctly, while still being ableto collide with other objects in the simulation. Objects are able to deform both temporarily and permanently using springs with distance constraints. Pressure simulation is alsoimplemented to simulate inflated polygons. The physics bodies does not feature frictionbetween objects, only friction against a static boundary of the simulation. The engine isthen evaluated in order to determine if it can run in real-time which is one of the goals.When it comes to the simulation, Verlet-integration will be used for updating the positions of particles, and every polygon will be built using these particles, and combinedusing certain constraints to make the particles act as one combined object. The main problem that will be solved is the interpenetration solver, which ensures that polygons do notoverlap, and two formulas will be combined to solve this problem. The collision detectionmethod uses line intersections to determine if objects are overlapping, this method endedup being quite expensive for polygons with a lot of vertices. One optimization techniqueis implemented which is axis-aligned bounding boxes around objects which improvedperformance significantly, which also makes the engine more viable for real-time simulations. The physics engine in this report is deterministic using a fixed time-step, dynamictime-step is not tested. The engine also only supports discrete collision detection.

Indiana University-Purdue University Indianapolis (IUPUI) / Traffic accidents cause millions of injuries and tens of thousands of fatalities per year worldwide. This thesis briefly reviews different types of active safety systems designed to reduce the number of accidents. Focusing on lane departure, a leading cause of crashes involving fatalities, we examine a lane-keeping system proposed by Minoiu Enache et al.They proposed a switched linear feedback (LMI) controller and provided two switching laws, which limit driver torque and displacement of the front wheels from the center of the lane. In this thesis, a state feedback (LQR) controller has been designed. Also, a new switching logic has been proposed which is based on driver's torque, lateral offset of the vehicle from the center of the lane and relative yaw angle. The controller activates assistance torque when the driver is deemed inattentive. It is deactivated when the driver regains control. Matlab/Simulink modeling and simulation environment is used to verify the results of the controller. In comparison to the earlier switching strategies, the maximum values of the state variables lie very close to the set of bounds for normal driving zone. Also, analysis of the controller’s root locus shows an improvement in the damping factor, implying better system response.

No description available.

We exhibit multiple periodic, collision-based orbits of the Newtonian n-body problem. Many of these orbits feature regularizable collisions between the masses. We demonstrate existence of the periodic orbits after performing the appropriate regularization. Stability, including linear stability, for the orbits is then computed using a technique due to Roberts. We point out other interesting features of the orbits as appropriate. When applicable, the results are extended to a broader family of orbits with similar behavior.

Our group has been studying chiral recognition in gas phase using mass spectrometry for more than 10 years. We are interested in gas phase studies of fundamental interactions because the gas phase avoids complications and masking effects that may arise upon solvation. Therefore, the results of gas phase experiments can be directly compared with those of high-level computational studies. In chapter 2, I studied the roles of hydrogen bonding and pi stacking in gas phase chiral recognition between aromatic crown molecules and aromatic amines. High affinity between host and guest doesn't necessarily result in better recognition. If the affinity is too high, both host enantiomers will bind to the chiral guest very tightly so little discrimination is observed. In order to build an efficient chiral recognition system, we need to select a host and guest that have intermediate binding affinity. Hydrogen bonding is another significant factor that controls the host-guest affinity. In the case of host 1, more hydrogen bonds results in better recognition. We also find that the degree of chiral recognition is greater in the gas phase than in solution. Modeling at the B3LYP/6-31G* level is qualitatively correct, but quantitative agreement with experiment is poor. Inspired by Rekharsky's work which shows successful induced chiral recognition with an achiral host (cucurbituril) in solution, we tested the possibility of applying cucurbiturils as gas phase chiral recognition containers in chapter 5. Conferring chirality on cucurbiturils makes the chiral recognition happen in a restricted space, which might strengthen or hinder the discrimination. By comparing our results with Rekharsky's, we showed the role of solvent in this chiral recognition process. In the gas phase, the enantiodiscrimination does not happen between the "leaving MP" and the "approaching" stronger chiral binder. Because hydrophobic effects are absent in the gas phase, it is possible that the hydrophobic methyl substituent of 2-methylpiperazine and the stronger chiral binder might not be simultaneously included inside the cavity. Therefore, we do not observe enantiodiscrimination in gas phase. The dissociation experiment for the CB[7] ternary complex shows that sec-butylamine binds externally to the CB[7] host. Further, the heterochiral diastereomer is more stable than the homochiral diastereomer. This conclusion is consistent with Rekharsky's result in solution. For more than 15 years, the most common ionization method in our lab has been electrospray ionization. However, ESI is subject to problems with ion suppression, especially when the sample is a mixture or it has a high concentration of salt. The easily ionized molecules tend to scavenge the available charges in the spray solution and dominate the resulting ion population even though other compounds may be present in high abundance. Nanoelectrospray usually yields cold ionization, and analyte suppression can be greatly reduced at nanospray flow rates. Therefore, we constructed a porous polymer monolith (PPM) nanospray emitter similar to that described by Oleschuk et al. and characterized the properties of the PPM emitter. This work is described in chapter 3. Our tests show that this PPM nanospray emitter possesses some special analytical properties: decreased ion suppression, quite stable spray, strong signal intensity and good reproducibility in emitter performance. Chapter 4 deals with the application of the new CRAFTI method to negative ions. CRAFTI stands for cross-sectional areas by Fourier transform ICR. The CRAFTI technique measures collision cross sections, providing a probe of the gas phase conformations of supramolecular complexes. Our preliminary work has shown that CRAFTI is applicable to positive ions, so we further demonstrate the application of the newly-developed method to negative ions in this work. Based on the fact that the experimental cross sections correlate linearly with the theoretical values, we have obtained evidence that CRAFTI is a valid method for negative ions. However, some problems remain. First, we are still working to understand the physical meaning of the CRAFTI cross sections. The absolute values we obtain are generally greater than those obtained from momentum transfer cross section calculations modeled in helium. Second, the precision of the measurements (currently about 2-3%) is still larger than we desire. We need to carefully tune the excitation and isolation amplitudes to make the signal strong and monoisotopic for weak ions. CRAFTI is a very promising and attractive method because FT-ICR provides accurate mass-to-charge measurement along with the cross section measurement. In other words, one technique is sufficient to obtain the shape, size and mass of a molecule simultaneously.