Minimum Time Motion of a Robotic Manipulator.

This dissertation treats the modeling, analysis, and trajectory control of a robotic manipulator to execute specified point-to-point tasks. The relative coordinate representation of kinematic and dynamic variables is defined using vectors and matrices based on coordinate transformations. A kinematic modeling of a manipulator is performed using Denavit-Hartenberg link parameters. For given end-effector information (location and orientation), a stable and efficient iterative numerical algorithm for a joint solution is developed. A modified general Gauss elimination and a direct minimum search are combined with other refinements to yield fast convergency and stable results. This algorithm can be used as a routine solution for various simple structured manipulators and for general structured manipulators for point-to-point and trajectory following. Two major formulations of robot dynamic modeling, the recursive Newton-Euler and the Largrange-Euler are reviewed utilizing the results of the kinematic analysis. The motion effects of dynamic terms and their relative significance on the nominal joint torque are determined in conjunction with the minimum time motion strategy. The relative significance of dynamic terms is analyzed for a given joint space trajectory. The motion effect of dynamic terms is analyzed by comparing the minimum time motion to the conventional optimum straight line trajectory in joint configuration space. A motion trend for a manipulator under minimum time execution is inferred from the simulation results. An efficient general solution algorithm for generating the minimum time trajectory for a point-to-point task subject to the actuator torque constraints is developed. A series of parametric cubic spline segments is used to represent the continuous joint trajectory. A formulation of an n segmented cubic spline satisfying second derivative continuity at knot points is derived. A Runge-Kutta 4th order, two starting point, forward and backward numerical integration and a non-derivative multi-variable minimum search are performed with a penalty function imposing the constraints on search parameters and kinematic motion parameters. Information for manipulator structure and controller design and trajectory planning for a notable increase in dynamic performance are obtained using the algorithms developed

XeCl laser pumped iodine laser using t-C4F9I

An iodine photodissociation laser using t-C4F9I as the active material was pumped by an XeCl laser. An iodine laser output energy of 3 mJ with pulse duration of 25 ns was obtained when the pumping pulse energy was 80 mJ, the iodide pressure was 70 torr, and the reflectance of the output mirror was 85 percent. The high pumping efficiency and low threshold pump power achieved in this experiment are attributable to the high absorption cross section at the pump laser wavelength (308 nm) of the iodide used

Direct solar-pumped iodine laser amplifier

The optimum conditions of a solar pumped iodine laser are found in this research for the case of a continuous wave operation and a pulsed operation. The optimum product of the pressure(p) inside the laser tube and the tube diameter(d) was pd=40 approx. 50 torr-cm on the contrary to the case of a high intensity flashlamp pumped iodine laser where the optimum value of the product is known to be pd=150 torr-cm. The pressure-diameter product is less than 1/3 of that of the high power iodine laser. During the research period, various laser materials were also studied for solar pumping. Among the laser materials, Nd:YAG is found to have the lowest laser threshold pumping intensity of about 200 solar constant. The Rhodamine 6G was also tested as the solar pumped laser material. The threshold pumping power was measured to be about 20,000 solar constant. The amplification experiment for a continuously pumped iodine laser amplifier was performed using Vortek solar simulator and the amplification factors were measured for single pass amplification and triple pass amplification of the 15 cm long amplifier tube. The amplification of 5 was obtained for the triple pass amplification

Roles of dark energy perturbations in the dynamical dark energy models: Can we ignore them?

We show the importance of properly including the perturbations of the dark energy component in the dynamical dark energy models based on a scalar field and modified gravity theories in order to meet with present and future observational precisions. Based on a simple scaling scalar field dark energy model, we show that observationally distinguishable substantial differences appear by ignoring the dark energy perturbation. By ignoring it the perturbed system of equations becomes inconsistent and deviations in (gauge-invariant) power spectra depend on the gauge choice.Comment: 5 pages, 4 figure

A Dynamic Resource Manager with Effective Resource Isolation Based on Workload Types in Virtualized Cloud Computing Environments

To use computing resources for processing parallel algorithms on demand, cloud computing has been widely used since it is able to scale in response to load increases and decreases. Typically, cloud computing providers offer virtual machines to cloud users with static configurations, and these configurations are not changed until virtual machines are shutting down. To accelerate parallel processing computations in cloud computing environments, we design and implement a dynamic resource manager by isolating resources based on workload types. To avoid unnecessary context switching and increase CPUs affinity, our dynamic resource manager determines whether vCPU to physical CPU core pinning is required. If so, the VM’s vCPUs are pinned by our dynamic resource manager, which can guarantee the resource and performance isolation. With our proposed resource manager for virtual machines, we can achieve a performance boost and load balancing at the same time. Performance results show that our proposed method outperforms the default scheduler of Xen about 36.2% by reducing the number of context switching for VMs

Identification of a Kitaev Quantum Spin Liquid by Magnetic Field Angle Dependence

Quantum spin liquids realize massive entanglement and fractional quasiparticles with localized spins, proposed as an avenue for quantum science and technology. In particular, topological quantum computations are suggested in the non-abelian phase of Kitaev quantum spin liquid with Majorana fermions, and detection of Majorana fermions is one of the most outstanding problems in modern condensed matter physics. Here, we propose a concrete way to identify the non-abelian Kitaev quantum spin liquid by magnetic field angle dependence. Topologically protected critical lines exist on a plane of magnetic field angles, and their shapes are determined by microscopic Hamiltonian information. A chiral spin operator plays a key role to detect the critical lines varying with magnetic field angles, and experimental criteria for the non-abelian spin liquid state are provided. Our proposal may be employed as a new route to probe a non-abelian quantum spin liquid in addition to the half-quantization of thermal Hall conductivity.Comment: 12 pages, 8 figures, 2 table

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Direct solar-pumped iodine laser amplifier

A XeCl laser pumped iodine laser oscillator was developed which will be incorporated into the Master Oscillator Power Amplifier (MOPA) system. The developed XeCl laser produces output energy of about 60 mJ per pulse. The pulse duration was about 10 nsec. The kinetic model for the solar-pumped laser was refined and the algorithm for the calculation of a set of rate equations was improved to increase the accuracy and the efficiency of the calculation. The improved algorithm was applied to explain the existing experimental data taken from a flashlamp pumped iodine laser for three kinds of lasants, i-C3F7I, n-C4F9I, and t-C4F9I. Various solid laser materials were evaluated for solar-pumping. The materials studied were Nd:YAG, Nd:YLF, and Cr:Nd:GSGG crystals. The slope efficiency of 0.17 percent was measured for the Nd:YLF near the threshold pump intensity which was 211 solar constants (29W/sq cm). The threshold pump intensity of the Nd:YAG was measured to be 236 solar constants (32W/sq cm) and the near-threshold slope efficiency was 0.12 percent. True CW laser operation of Cr:Nd:GSGG was possible only at pump intensities less than or equal to 1,500 solar constants (203 W/sq cm). This fact was attributed to the high thermal focusing effect of the Cr:Nd:GSGG rod

Acronym-Expansion Disambiguation for Intelligent Processing of Enterprise Information

An acronym is an abbreviation of several words in such a way that the abbreviation itself forms a pronounceable word. Acronyms occur frequently throughout various documents, especially those of a technical nature, for example, research papers and patents. While these acronyms can enhance document readability, in a variety of fields, they have a negative effect on business intelligence. To resolve this problem, we propose a method of acronym-expansion disambiguation to collect high-quality enterprise information. In experimental evaluations, we demonstrate its efficiency through the use of objective comparisons