Search-Based Planning and Replanning in Robotics and Autonomous Systems

In this chapter, we present one of the most crucial branches in motion planning: search-based planning and replanning algorithms. This research branch involves two key points: first, representing traverse environment information as discrete graph form, in particular, occupancy grid cost map at arbitrary resolution, and, second, path planning algorithms calculate paths on these graphs from start to goal by propagating cost associated with each vertex in graph. The chapter will guide researcher through the foundation of motion planning concept, the history of search-based path planning and then focus on the evolution of state-of-the-art incremental, heuristic, anytime algorithm families that are currently applied on practical robot rover. The comparison experiment between algorithm families is demonstrated in terms of performance and optimality. The future of search-based path planning and motion planning in general is also discussed

An exploration of trypophobia

Images comprising clusters of objects can induce aversion and certain symptoms of anxiety, fear and disgust (so-called “trypophobia”) in about 13% of the population. This thesis is an investigation of the stimulus and response characteristics of the condition. First, a symptom questionnaire (Trypophobia Questionnaire) was developed and validated based on reports of different categories of symptoms. The questionnaire demonstrated a single construct that predicted discomfort from trypophobic images, but not neutral or unpleasant images, and did not correlate with anxiety. Second, filtering images reduced the excess energy at mid-range spatial frequencies (previously associated with both trypophobic and uncomfortable images). Relative to unfiltered trypophobic images, the discomfort from filtered images experienced by observers with high TQ scores was less than that experienced with neutral images, and by observers with low TQ scores. Clusters of concave objects (holes) did not induce significantly more discomfort than clusters of convex objects (bumps), suggesting that trypophobia (previously referred to as “fear of holes”) involves clusters not of holes but of objects with particular spectral profile involving excess energy at mid-range spatial frequencies. These visual characteristics have been previously shown to induce discomfort and a strong cortical oxygenation. The same abnormal oxygenation occurred for trypophobic images, but only for individuals with high TQ scores. Three lines of evidence suggest that trypophobia is a response of disgust rather than fear: (1) trypophobia was associated with an aversion to spiders, and not snakes; (2) trypophobic stimuli did not produce a bias in the subjective estimation of stimulus duration but (3) increased the heart rate and its variability. Fear inducing stimuli generally give effects opposite to those listed as 2 and 3. In conclusion, trypophobia is a reaction of disgust to clusters of objects with particular spectral profile that may resemble contamination sources (e.g., skin lesions)

Distributed generation diversity level for optimal investment planning

The task of improving the supply quality and maintaining supply continuity during emergencies has become more feasible for a distribution company (DISCO), owing to new developments in Distributed Generation (DG) technologies. Even though the technical issues regarding DG interconnection to the main grid are of great importance and are being addressed by on-going research, it must be clearly placed in the context of on the financial performance of the utility. In this paper, a general approach to quantify the technical benefits of DG employment is proposed. The power system economic impact is assessed by evaluating supply quality, supply reliability, system power losses and capital investment. Moreover, the rationale for this research also includes the possibility of DG diversity level in contribution to the economical benefits from DG integration. The approach is tested by a system which is developed from a Tasmanian distribution example. Simulation results and discussion are presented to illustrate the effectiveness and usefulness of the method

Maximum Likelihood Estimator for Hidden Markov Models in continuous time

The paper studies large sample asymptotic properties of the Maximum Likelihood Estimator (MLE) for the parameter of a continuous time Markov chain, observed in white noise. Using the method of weak convergence of likelihoods due to I.Ibragimov and R.Khasminskii, consistency, asymptotic normality and convergence of moments are established for MLE under certain strong ergodicity conditions of the chain.Comment: Warning: due to a flaw in the publishing process, some of the references in the published version of the article are confuse

Computational fluid dynamic modeling of 100ml and scaled-down 10ml stirred suspension bioreactors enables prediction of embryonic stem cell characteristics

There is a growing necessity for cell cultivation using bioreactors to translate laboratory based culture protocols into reproducible, scalable, and robust bioprocesses. Stirred suspension bioreactors offer several advantages over planar static cultures, including: reduced labour and operating costs, reduced space requirements, greater cellular homogeneity, and increased cell density per volume [1]. An important consideration when using stirred suspension bioreactors is mechanical stimulation. Fluid shear at the fluid-cell interface triggers cellular responses through mechanotransduction and can modulate stem cell proliferation and differentiation. However, if the shear stress caused by the impeller exceeds the tolerance limit of the cells, it causes cell damage and death, resulting in a lower quality and yield of cells. The shear rate distribution depends on bioreactor geometry, impeller agitation rate, cell density, and cell media viscosity [2]. Current scale-up protocols to predict agitation rates rely on maximum values of hydrodynamic variables, which occur only at the impeller tip. The volume averaged shear stress and maximum shear stress differ greatly, and cells dispersed within the liquid experience different local and global forces. This makes it difficult to predict how cells will respond to changes in bioreactor geometries and sizes. Profiling distributed and average forces in the bioreactor is critical to ensure quality and yield in cell manufacturing. Hydrodynamics, specifically velocities, shear rates, and energy dissipation rates, can be studied using computational fluid dynamic (CFD) modeling. Please click Additional Files below to see the full abstract

Building up spacetime with quantum entanglement

In this essay, we argue that the emergence of classically connected spacetimes is intimately related to the quantum entanglement of degrees of freedom in a non-perturbative description of quantum gravity. Disentangling the degrees of freedom associated with two regions of spacetime results in these regions pulling apart and pinching off from each other in a way that can be quantified by standard measures of entanglement.Comment: Gravity Research Foundation essay, 7 pages, LaTeX, 5 figure