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Units and Measurements
Published in Daniel H. Nichols, Physics for Technology, 2019
Mass: The mass of an object is the measure of how much force is required to change the motion of the object. Its basic unit of measurement is the gram. A small paper clip has the mass of about 1 g. The kilogram is currently defined in terms of the mass of a platinum-iridium cylinder stored in a vault in France. Imagine having to travel to France to determine whether your scale is correct or not! This definition of the kilogram that is going to be replaced with a method based on fundamental constants of nature, like the speed of light or the charge on an electron. The definition of the kilogram will be based on a constant called Planck’s constant, a value from an area of physics called quantum mechanics that describes the physics of atoms, see www.nist.gov for more details.
Soil constituents
Published in Ivan Gratchev, Dong-Sheng Jeng, Erwin Oh, Soil Mechanics Through Project-Based Learning, 2018
Ivan Gratchev, Dong-Sheng Jeng, Erwin Oh
Answer: In our daily life, mass and weight often mean the same thing; however, in soil mechanics, they are different. Unlike the term mass (which is measured in kilograms), weight is force measured in Newton (N).
Elementary Heat Transfer
Published in Anthony F. Mills, Heat and Mass Transfer, 2018
In this text, we will use the SI system, with which the student has become familiar from physics courses. For convenience, this system is summarized in the tables of Appendix B. Base and supplementary units, such as length, time, and plane angle, are given in Table B.1a; and derived units, such as force and energy, are given in Table B.1b. Recognized non-SI units (e.g., hour, bar) that are acceptable for use with the SI system are listed in Table B.1c. Multiples of SI units (e.g., kilo, micro) are defined in Table B.1d. Accordingly, the property data given in the tables of Appendix A are in SI units. The student should review this material and is urged to be careful when writing down units. For example, notice that the unit of temperature is a kelvin (not Kelvin) and has the symbol K (not °K). Likewise, the unit of power is the watt (not Watt). The symbol for a kilogram is kg (not KG). An issue that often confuses the student is the correct use of Celsius temperature. Celsius temperature is defined as (T − 273.15) where T is in kelvins. However, the unit “degree Celsius” is equal to the unit “kelvin” (1°C = 1 K).
Accurate nanoparticle size determination using electrical mobility measurements in the step and scan modes
Published in Aerosol Science and Technology, 2022
Kaleb Duelge, George Mulholland, Michael Zachariah, Vincent A. Hackley
Nanoparticle “size,” typically a method-defined measurement and frequently based on the diameter of an equivalent sphere, is an important characteristic that impacts particle transport properties, such as mobility, diffusion, friction, coagulation, and charging. Size also plays an important role in optically active materials and is a critical factor in biodistribution. It is therefore important to accurately measure the size of nanoparticles, which is why size standards are relied on heavily in research and industry. A common method for certifying standards in industry is based on electron microscopy (Particle Technology Technical Notes and Reference Guide – Strategies and Procedures for Bead Optimization 2018). In some cases, the known and unknown particles are mixed and deposited together on a microscope grid. Well-characterized methods, such as light scattering (Mulholland et al. 1985), the calibrated atomic force microscope of the National Institute of Standards and Technology (NIST) (Dixson et al. 1999), and electro-gravitational aerosol balance (Takahata, Sakurai, and Ehara 2020), where the key uncertainty terms have been calculated, can be used for primary certification. It is also ideal for a method to be traceable, where a direct connection is made to an international system of units (SI): most often the meter, but potentially the kilogram if particle mass or volume and density are determined.
Probabilistic tracking control of dissipated Hamiltonian systems excited by Gaussian white noises
Published in International Journal of Systems Science, 2021
Ying Yang, Yong Wang, Zhilong Huang
As a typical non-smooth system, Coulomb frictional system is constituted by a mass block, a linear damper, a nonlinear spring, and a complex contact surface. The contact surface hinders the motion of the mass block by providing a constant frictional force with the direction against the velocity. It is extensively adopted to illustrate the stick slip behaviour of a mass block moving on a moving belt (Jin et al., 2019). The motion of equation of controlled frictional system is as, where denotes the sign of argument, the term denotes the Coulomb frictional force and is the amplitude of friction. In accordance with the convention in the field of nonlinear dynamics, the mass of block is set as 1 kg (kilogram). The physical SI units of Q, P, t, , c, and are m (metre), kg.m/s (kilogram times metre/second), s (second), N/m (Newton over metre), kg/s (kilogram/second), N (Newton) and N (Newton), respectively. The feedback control is set as the separated form , in which the controlled Hamiltonian . The additional potential and energy-dependent damping coefficient are expanded as and , respectively.