12 research outputs found
Biologically-inspired control framework for insect animation.
Insects are common in our world, such as ants, spiders, cockroaches etc. Virtual representations of them have wide applications in Virtual Reality (VR), video games and films. Compared with the large volume of works in biped animation, the problem of insect animation was less explored. Their small body parts, complex structures and high-speed movements challenge the standard techniques of motion synthesis. This thesis addressed the aforementioned challenge by presenting a framework to efficiently automate the modelling and authoring of insect locomotion. This framework is inspired by two key observations of real insects: fixed gait pattern and distributed neural system. At the top level, a Triangle Placement Engine (TPE) is modelled based on the double-tripod gait pattern of insects, and determines the location and orientation of insect foot contacts, given various user inputs. At the low level, a Central Pattern Generator (CPG) controller actuates individual joints by mimicking the distributed neural system of insects. A Controller Look-Up Table (CLUT) translates the high-level commands from the TPE into the low-level control parameters of the CPG. In addition, a novel strategy is introduced to determine when legs start to swing. During high-speed movements, the swing mode is triggered when the Centre of Mass (COM) steps outside the Supporting Triangle. However, this simplified mechanism is not sufficient to produce the gait variations when insects are moving at slow speed. The proposed strategy handles the case of slow speed by considering four independent factors, including the relative distance to the extreme poses, the stance period, the relative distance to the neighbouring legs, the load information etc. This strategy is able to avoid the issues of collisions between legs or over stretching of leg joints, which are produced by conventional methods. The framework developed in this thesis allows sufficient control and seamlessly fits into the existing pipeline of animation production. With this framework, animators can model the motion of a single insect in an intuitive way by specifying the walking path, terrains, speed etc. The success of this framework proves that the introduction of biological components could synthesise the insect animation in a naturalness and interactive fashion
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Bayesian analysis of complex mutations in HBV, HCV, and HIV studies
This article provides a review of the Bayesian-inference-based methods applied to Hepatitis B Virus (HBV), Hepatitis C Virus (HCV), and Human Immunodeficiency Virus (HIV) studies with a focus on the detection of the viral mutations and various problems which are correlated to these mutations. The authors also provide a summary of the Bayesian methods' applications toward these viruses' studies, where several important and useful results have been discovered
Femtosecond Laser Filamentation in Atmospheric Turbulence
The effects of turbulence intensity and turbulence region on the distribution
of femtosecond laser filaments are experimentally elaborated. Through the
ultrasonic signals emitted by the filaments, and it is observed that increasing
turbulence intensity and expanding turbulence active region cause an increase
in the start position of the filament, and a decrease in filament length, which
can be well explained by the theoretical calculation. It is also observed that
the random perturbation of the air refractive index caused by atmospheric
turbulence expanded the spot size of the filament. Additionally, when
turbulence intensity reaches , multiple filaments are formed. Furthermore, the
standard deviation of the transverse displacement of filament is found to be
proportional to the square root of turbulent structure constant under the
experimental turbulence parameters in this paper. These results contribute to
the study of femtosecond laser propagation mechanisms in complex atmospheric
turbulence conditionsComment: 9 pages, 4 figure
Coupled air lasing gain and Mie scattering loss: aerosol effect in filament-induced plasma spectroscopy
Femtosecond laser filament-induced plasma spectroscopy (FIPS) demonstrates
great potentials in the remote sensing for identifying atmospheric pollutant
molecules. Due to the widespread aerosols in atmosphere, the remote detection
based on FIPS would be affected from both the excitation and the propagation of
fingerprint fluorescence, which still remain elusive. Here the physical model
of filament-induced aerosol fluorescence is established to reveal the combined
effect of Mie scattering and amplification spontaneous emission, which is then
proved by the experimental results, the dependence of the backward fluorescence
on the interaction length between filament and aerosols. These findings provide
an insight into the complicated aerosol effect in the overall physical process
of FIPS including propagation, excitation and emission, paving the way to its
practical application in atmospheric remote sensing.Comment: 7 pages, 4 figure
Investigation of Focusing Properties on Astigmatic Gaussian Beams in Nonlinear Medium
Ultra-short laser filamentation has been intensively studied due to its unique optical properties for applications in the field of remote sensing and detection. Although significant progress has been made, the quality of the laser beam still suffers from various optical aberrations during long-range transmission. Astigmatism is a typical off-axis aberration that is often encountered in the off-axis optical systems. An effective method needs to be proposed to suppress the astigmatism of the beam during filamentation. Herein, we numerically investigated the impact of the nonlinear effects on the focusing properties of the astigmatic Gaussian beams in air and obtained similar results in the experiment. As the single pulse energy increases, the maximum on-axis intensity gradually shifted from the sagittal focus to the tangential focus and the foci moved forward simultaneously. Moreover, the astigmatism could be suppressed effectively with the enhancement of the nonlinear effects, that is, the astigmatic difference and the degree of beam distortion were both reduced. Through this approach, the acoustic intensity of the filament (located at the tangential focal point) increased by a factor of 22.8. Our work paves a solid step toward the practical applications of the astigmatism beam as the nonlinear lidar
Meta-Analysis of the Association between Vitamin D and Autoimmune Thyroid Disease
Although emerging evidence suggests that low levels of vitamin D may contribute to the development of autoimmune disease, the relationship between vitamin D reduction and autoimmune thyroid disease (AITD), which includes Graves’ disease (GD) and Hashimoto thyroiditis (HT), is still controversial. The aim was to evaluate the association between vitamin D levels and AITD through systematic literature review. We identified all studies that assessed the association between vitamin D and AITD from PubMed, Embase, CENTRAL, and China National Knowledge Infrastructure (CNKI) databases. We included studies that compared vitamin D levels between AITD cases and controls as well as those that measured the odds of vitamin D deficiency by AITD status. We combined the standardized mean differences (SMD) or the odds ratios (OR) in a random effects model. Twenty case-control studies provided data for a quantitative meta-analysis. Compared to controls, AITD patients had lower levels of 25(OH)D (SMD: −0.99, 95% CI: −1.31, −0.66) and were more likely to be deficient in 25(OH)D (OR 2.99, 95% CI: 1.88, 4.74). Furthermore, subgroup analyses result showed that GD and HT patients also had lower 25(OH)D levels and were more likely to have a 25(OH)D deficiency, suggesting that low levels of serum 25(OH)D was related to AITD