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Topic Review
Power Generation Using Dielectric Elastomers
Power generation using dielectric elastomer (DE) artificial muscle is attracting attention because of its light weight, low cost, and high-efficiency. Since this method is a system that produces electricity without emitting carbon dioxide nor using rare earths, it would contribute to the goal of environmental sustainability. 
  • 1.7K
  • 30 Jun 2021
Topic Review
Power
In physics, power is the amount of energy transferred or converted per unit time. In the International System of Units, the unit of power is the watt, equal to one joule per second. In older works, power is sometimes called activity. Power is a scalar quantity. Power is related to other quantities; for example, the power involved in moving a ground vehicle is the product of the traction force on the wheels and the velocity of the vehicle. The output power of a motor is the product of the torque that the motor generates and the angular velocity of its output shaft. Likewise, the power dissipated in an electrical element of a circuit is the product of the current flowing through the element and of the voltage across the element.
  • 2.4K
  • 31 Oct 2022
Topic Review
Potential Flow Around a Circular Cylinder
In mathematics, potential flow around a circular cylinder is a classical solution for the flow of an inviscid, incompressible fluid around a cylinder that is transverse to the flow. Far from the cylinder, the flow is unidirectional and uniform. The flow has no vorticity and thus the velocity field is irrotational and can be modeled as a potential flow. Unlike a real fluid, this solution indicates a net zero drag on the body, a result known as d'Alembert's paradox.
  • 4.2K
  • 31 Oct 2022
Topic Review
Position and Momentum Space
In physics and geometry, there are two closely related vector spaces, usually three-dimensional but in general could be any finite number of dimensions. Position space (also real space or coordinate space) is the set of all position vectors r in space, and has dimensions of length. A position vector defines a point in space. If the position vector of a point particle varies with time it will trace out a path, the trajectory of a particle. Momentum space is the set of all momentum vectors p a physical system can have. The momentum vector of a particle corresponds to its motion, with units of [mass][length][time]−1. Mathematically, the duality between position and momentum is an example of Pontryagin duality. In particular, if a function is given in position space, f(r), then its Fourier transform obtains the function in momentum space, φ(p). Conversely, the inverse Fourier transform of a momentum space function is a position space function. These quantities and ideas transcend all of classical and quantum physics, and a physical system can be described using either the positions of the constituent particles, or their momenta, both formulations equivalently provide the same information about the system in consideration. Another quantity is useful to define in the context of waves. The wave vector k (or simply "k-vector") has dimensions of reciprocal length, making it an analogue of angular frequency ω which has dimensions of reciprocal time. The set of all wave vectors is k-space. Usually r is more intuitive and simpler than k, though the converse can also be true, such as in solid-state physics. Quantum mechanics provides two fundamental examples of the duality between position and momentum, the Heisenberg uncertainty principle ΔxΔp ≥ ħ/2 stating that position and momentum cannot be simultaneously known to arbitrary precision, and the de Broglie relation p = ħk which states the momentum and wavevector of a free particle are proportional to each other. In this context, when it is unambiguous, the terms "momentum" and "wavevector" are used interchangeably. However, the de Broglie relation is not true in a crystal.
  • 1.8K
  • 24 Nov 2022
Topic Review
Polymer-Based Sensors
Due to the wide application of wearable electronic devices in daily life, research into flexible electronics has become very attractive. Various polymer-based sensors have emerged with great sensing performance and excellent extensibility. It is well known that different structural designs each confer their own unique, great impacts on the properties of materials. For polymer-based pressure/strain sensors, different structural designs determine different response-sensing mechanisms, thus showing their unique advantages and characteristics. 
  • 460
  • 23 Feb 2023
Topic Review
Polymer Waveguide-Based Sensors
The optical waveguide (WG) is one of the fundamental components of integrated photonics. Polymer WGs can operate in either single-mode (with core diameters between 2 μm and 5 μm) or multimode (with core dimensions generally between 30 μm and 500 μm) regimes. They are both entirely consistent with the matching optical fiber type due to the similar mode field diameter. A WG is simply utilized as a light link to connect external instruments to a sampling point or an optical sensing element in an extrinsic sensor. In biomedicine, environmental monitoring, process control, and safety, extrinsic sensors are already widely employed.
  • 483
  • 08 Mar 2023
Topic Review
Polarization-Sensitive Digital Holographic Imaging
Polarization-sensitive digital holographic imaging (PS-DHI) is a recent imaging technique based on interference among several polarized optical beams. PS-DHI allows simultaneous quantitative three-dimensional reconstruction and quantitative evaluation of polarization properties of a given sample with micrometer scale resolution. Since this technique is very fast and does not require labels/markers, it finds application in several fields, from biology to microelectronics and micro-photonics.
  • 839
  • 10 Aug 2020
Topic Review
Polarization Lidar
Traditional lidar techniques mainly rely on the backscattering/echo light intensity and spectrum as information sources. In contrast, polarization lidar (P-lidar) expands the dimensions of detection by utilizing the physical property of polarization. By incorporating parameters such as polarization degree, polarization angle, and ellipticity, P-lidar enhances the richness of physical information obtained from target objects, providing advantages for subsequent information analysis.
  • 571
  • 12 Oct 2023
Topic Review
Polarization Holography
Polarization holography has the unique capacity to record and retrieve the amplitude, phase, and polarization of light simultaneously in a polarization-sensitive recording material and has attracted widespread attention. Polarization holography is a noteworthy technology with potential applications in the fields of high-capacity data storage, polarization-controlled optical elements, and other related fields.
  • 2.1K
  • 23 Jan 2021
Topic Review
Polarization Conversion from Anisotropy Media
Anisotropy of the transmission media exerts a strong influence on the reflection and transmission coefficients. Anomalous refraction yields the consequence of polarization conversion for the refracted wave. We discuss this important physical phenomenon by invoking practical interfaces between strongly anisotropic rocks, e.g., between O-shale and A-shale.  
  • 1.3K
  • 02 Nov 2020
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