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Topic Review
Navigation of Mobile Robot
Mobile robot navigation is a study area with several potential applications, both military and nonmilitary. Nonetheless, a great deal of problems remain, and many of them will probably need to be addressed using either a novel theory or another approach. The autonomous navigation of mobile robots has been studied by several researchers. Robots may encounter static interior environments or dynamic environments that change swiftly. The mobile robot’s goals may include reaching a particular place, following a predetermined course, or mapping out a space for later use. Many studies have been conducted throughout the world regarding this. Different methodologies were proposed on this topic, each with its advantages and disadvantages based on the recursive research. Navigation of a mobile robot involves determining the robot’s trajectory through an environment to reach a desired goal location while avoiding obstacles. 
  • 158
  • 29 Dec 2023
Topic Review
Nature-inspired optimization algorithms
Over previous decades, many nature-inspired optimization algorithms (NIOAs) have been proposed and applied due to their importance and significance. Some survey studies have also been made to investigate NIOAs and their variants and applications. However, these comparative studies mainly focus on one single NIOA, and there lacks a comprehensive comparative and contrastive study of the existing NIOAs.
  • 7.2K
  • 11 Nov 2021
Topic Review
Nature-Inspired Chiral Structures
Diverse chiral structures observed in nature find applications across various domains, including engineering, chemistry, and medicine. Particularly notable is the optical activity inherent in chiral structures, which has emerged prominently in the field of optics. This phenomenon has led to a wide range of applications, encompassing optical components, catalysts, sensors, and therapeutic interventions.
  • 159
  • 16 Nov 2023
Topic Review
Nature of the Bounce in LQC and PQM
We present a review concerning quantum cosmology in the presence of cut-off physics. We analyze how the Wheeler–DeWitt equation describes the quantum Universe dynamics when a pure metric approach is concerned, showing that the primordial singularity is not removed by the quantum effects. We then analyze the main implications of applying Loop Quantum Gravity prescriptions to the minisuperspace model, i.e., we discuss the basic features of Loop Quantum Cosmology. For the isotropic Universe dynamics, we compare the original m0 scheme and the most commonly accepted formulation, i.e. the so-called ¯m scheme. Furthermore, some fundamental results concerning the Bianchi Universes are discussed. Finally, we consider some relevant criticisms about the real link between the full theory of LQG and its minisuperspace implementation, especially with respect to the preservation of the internal SU(2) symmetry. In the second part of the review, we consider the dynamics of the isotropic Universe and of the Bianchi models in the framework of Polymer Quantum Mechanics. We first address the polymerization in termsof the Ashtekar–Barbero–Immirzi connection and show how the resulting dynamics is isomorphic to the m0 scheme of LQC with a critical energy density of the Universe that depends on the initial conditions for the dynamics. Then we analyze the polymerization of volume-like variables, both for the isotropic and Bianchi I models, and we see that if the Universe volume (the cubed scale factor) is one of the configurational variables, then the resulting dynamics is isomorphic to that for the ¯m scheme of LQC, with the critical energy density value being fixed only by fundamental constants and the Immirzi parameter. Finally, we consider the polymer quantum dynamics of the homogeneous and inhomogeneous Mixmaster model by means of a metric approach. In particular, we compare the results obtained by using the volume variable, which leads to the emergence of a singularity-free and chaos-free cosmology, to the use of the standard Misner variable. In the latter case we deal with the surprising result of a cosmology that is still singular, and its chaotic properties depend on the ratio between the lattice steps for the isotropic and anisotropic variables. We conclude the review with some considerations of the problem of changing variables in polymer cosmology. In particular, on a semiclassical level, we consider how the dynamics can be properly mapped in two different sets of variables (at the price of having to deal with a coordinate dependent lattice step), and we infer some possible implications on the equivalence of the m0 and ¯m scheme of LQC.
  • 471
  • 09 Oct 2021
Topic Review
Naturalness
In physics, naturalness is the property that the dimensionless ratios between free parameters or physical constants appearing in a physical theory should take values "of order 1" and that free parameters are not fine-tuned. That is, a natural theory would have parameter ratios with values like 2.34 rather than 234000 or 0.000234. The requirement that satisfactory theories should be "natural" in this sense is a current of thought initiated around the 1960s in particle physics. It is a criterion that arises from the seeming non-naturalness of the standard model and the broader topics of the hierarchy problem, fine-tuning, and the anthropic principle. However it does tend to suggest a possible area of weakness or future development for current theories such as the Standard Model, where some parameters vary by many orders of magnitude, and which require extensive "fine-tuning" of their current values of the models concerned. The concern is that it is not yet clear whether these seemingly exact values we currently recognize, have arisen by chance (based upon the anthropic principle or similar) or whether they arise from a more advanced theory not yet developed, in which these turn out to be expected and well-explained, because of other factors not yet part of particle physics models. The concept of naturalness is not always compatible with Occam's razor, since many instances of "natural" theories have more parameters than "fine-tuned" theories such as the Standard Model. Naturalness in physics is closely related to the issue of fine-tuning, and over the past decade many scientists argued that the principle of naturalness is a specific application of Bayesian statistics. In the history of particle physics, the naturalness principle has given correct predictions three times - in the case of electron self-energy, pion mass difference and kaon mass difference.
  • 632
  • 28 Oct 2022
Topic Review
Natural Convection
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convection is unspecified, convection due to the effects of thermal expansion and buoyancy can be assumed. Convection may also take place in soft solids or mixtures where particles can flow. Convective flow may be transient (such as when a multiphase mixture of oil and water separates) or steady state (see Convection cell). The convection may be due to gravitational, electromagnetic or fictitious body forces. Heat transfer by natural convection plays a role in the structure of Earth's atmosphere, its oceans, and its mantle. Discrete convective cells in the atmosphere can be identified by clouds, with stronger convection resulting in thunderstorms. Natural convection also plays a role in stellar physics. Convection is often categorised or described by the main effect causing the convective flow, e.g. Thermal convection. Convection cannot take place in most solids because neither bulk current flows nor significant diffusion of matter can take place.
  • 1.4K
  • 10 Oct 2022
Topic Review
Natural Circulation
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convection is unspecified, convection due to the effects of thermal expansion and buoyancy can be assumed. Convection may also take place in soft solids or mixtures where particles can flow. Convective flow may be transient (such as when a multiphase mixture of oil and water separates) or steady state (see Convection cell). The convection may be due to gravitational, electromagnetic or fictitious body forces. Heat transfer by natural convection plays a role in the structure of Earth's atmosphere, its oceans, and its mantle. Discrete convective cells in the atmosphere can be identified by clouds, with stronger convection resulting in thunderstorms. Natural convection also plays a role in stellar physics. Convection is often categorised or described by the main effect causing the convective flow, e.g. Thermal convection. Convection cannot take place in most solids because neither bulk current flows nor significant diffusion of matter can take place.
  • 407
  • 07 Nov 2022
Topic Review
NASA Heliophysics
NASA Heliophysics is an aspect of NASA science that enables understanding the Sun, heliosphere, and planetary environments as a single connected system. In addition to solar processes, this domain of study includes the interaction of solar plasma and solar radiation with Earth, the other planets, and the galaxy. By analyzing the connections between the Sun, solar wind, and planetary space environments, the fundamental physical processes that occur throughout the universe are uncovered. Understanding the connections between the Sun and its planets will allow for predicting the impacts of solar interaction on humans, technological systems, and even the presence of life itself. This is also the stated goal of Science Mission Directorate's Heliophysics Research.
  • 389
  • 15 Nov 2022
Topic Review
Nanotechnology in Agriculture
Research has shown nanoparticles to be a groundbreaking tool for tackling many arising global issues, the agricultural industry being no exception. In general, a nanoparticle is defined as any particle where one characteristic dimension is 100nm or less. Because of their unique size, these particles begin to exhibit properties that their larger counterparts may not. Due to their scale, quantum mechanical interactions become more important than classic mechanical forces, allowing for the prevalence of unique physical and chemical properties due to their extremely high surface-to-body ratio. Properties such as cation exchange capacity, enhanced diffusion, ion adsorption, and complexation are enhanced when operating at nanoscale. This is primarily the consequence of a high proportion of atoms being present on the surface, with an increased proportion of sites operating at higher reactivities with respect to processes such as adsorption processes and electrochemical interactions. Nanoparticles are promising candidates for implementation in agriculture. Because many organic functions such as ion exchange and plant gene expression operate on small scales, nanomaterials offer a toolset that works at just the right scale to provide efficient, targeted delivery to living cells. Current areas of focus of nanotechnology development in the agricultural industry include development of environmentally conscious nanofertilizers to provide efficient ion, nutrient delivery into plant cells, and plant gene transformations to produce plants with desirable genes such as drought resistance and accelerated growth cycles. With the global population on the rise, it is necessary to make advancements in sustainable farming methods that generate higher yields in order to meet the rising food demand. However, it must be done without generating long-term consequences such as depletion of arable land or water sources, toxic runoff, or bioaccumulative toxicity. In order to meet these demands, research is being done into the incorporation of nanotechnology agriculture.
  • 587
  • 08 Nov 2022
Topic Review
Nanotechnology Education
Nanotechnology education involves a multidisciplinary natural science education with courses such as physics, chemistry, mathematics and molecular biology. It is being offered by many universities around the world. The first program involving nanotechnology was offered by the University of Toronto's Engineering Science program, where nanotechnology could be taken as an option. Here is a partial list of universities offering nanotechnology education, and the degrees offered (Bachelor of Science, Master of Science, and/or Ph.D in Nanotechnology).
  • 611
  • 14 Oct 2022
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