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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).
Basic Mathematics and Systems of Measurement Units
Published in Muhammad H. Rashid, Ahmad Hemami, Electricity and Electronics for Renewable Energy Technology, 2017
In the metric system the unit for measuring force is Newton (N). But, occasionally kilogram is used for measuring force (in the same fashion that pound is used for both mass and force), because in an older system, kilogram was the unit for force. Moreover, although lbm is frequently used as a unit of mass, the official unit for mass in the imperial system is slug (not heard by many people). For this reason the following lines are very fundamental to the realization of mass and force units: If the mass of an object is 1 lbm, its weight on Earth is1 lbF. Its official mass is 1/32.17 slug (32.17 ft/sec2 is the gravity acceleration in the imperial system).If the mass of an object is 1 kg, its weight on Earth is 1 kg, which is 9.81 N (9.81 m/sec2 is the gravity acceleration in the metric system). The three principal units in each system can be used to define and derive other units.
Units and Significant Figures
Published in Patrick F. Dunn, Michael P. Davis, Measurement and Data Analysis for Engineering and Science, 2017
Patrick F. Dunn, Michael P. Davis
The SI base unit of mass is the kilogram (kg). This is the only base unit still defined in terms of an artifact. The international standard is a cylinder of platinum-iridium alloy kept by the International Bureau of Weights and Measures in Sèvres, France. A copy of this cylinder, a secondary standard, is at the NIST in Gaithersburg, Maryland, where it serves as the primary standard in the United States. The kilogram is the only SI base unit linked to a unique physical object. This will end soon when the kilogram is redefined in terms of a more accurate, atom-based standard [4].
Controllability of bilinear quantum systems in explicit times via explicit control fields
Published in International Journal of Control, 2021
In the current section, we briefly propose a possible application of Theorem 1.1. Let us consider an electron trapped in a one-dimensional guide of length m and represented by the quantum state ψ. We suppose that the electron is subjected to an external time-depending electromagnetic field with and a positive time. Let kg be the mass of the electron and with ℏ the reduced Planck constant. The dynamics of ψ is modelled by the Schrödinger equation We substitute , and Now, are dimensionless (without unit of measurement) and (20) corresponds to If the potential is equal to , then we obtain the (BSE) We point out that the last equation can be used to model the dynamics of an electron subjected to two external fields. The first one forces its behaviour to a quantum harmonic oscillator with time dependent intensity. The second field instead traps the electron in a potential well.
Improvement of existing railway subgrade by deep mixing
Published in European Journal of Environmental and Civil Engineering, 2020
Alain Le Kouby, Antoine Guimond-Barrett, Philippe Reiffsteck, Anne Pantet, Jean-Francois Mosser, Nicolas Calon
Where T is the blade rotation number per metre, M is the total number of mixing blades, N is the rotational speed of the blades (rpm) and Vd is the penetration rate in metres per minute (m/min). The blade rotation number for the columns in Vernouillet was between 700 and 1500 rotations/m. The binder used was a slag cement containing 85% of granulated ground blastfurnace slag (CEM III/C 32.5 PMES). Bentonite was added to stabilise the cement grouts. The cement factors (mass of dry binder per cubic metre of soil) tested varied between 200 and 400 kg/m3. It is important to note that these cement contents represent the amount of binder injected into the columns. The actual binder contents are probably slightly lower as spoil returns to the surface during mixing operations. This spoil is immediately pumped and evacuated as the column installation process continues.
Effect of coal particle density on combustion kinetics of Indian coal
Published in International Journal of Coal Preparation and Utilization, 2023
Pritam Kumar, Barun Kumar Nandi
Where λB is the Boltzmann constant (1.3806 × 10−23 m2 kg/s2 K) and ξ is the Planck constant (6.6261 × 10−34 m2 kg/s). Table 9 reported the average value of ΔH, ΔG and ΔS. It is seen from Table 9 that ΔH for 1.25 MRD coal is maximum (95.39 kJ/mol) compared to 1.325 MRD coal, indicating lighter MRD coal decomposition requires higher endothermic energy. Further, ΔH reduces from 93.98 to 85.39 kJ/mol with the increase of coal’s MRD from 1.325 to 2.20. The lower ΔH value for heavier MRD coal is due to the inadequacy of combustible material. Analysis of ΔG values infers that 1.25 MRD coal required lower (178.51 kJ/mol) heat input during decomposition compared to 1.325 MRD coal, signifying ease of combustion of 1.25 MRD coal. With the increase of MRD from 1.25 to 2.20, ΔG value increased from 182.97 to 219.22 kJ/mol. Such an increase in ΔG value with MRD is due to the increase in ash layer thickness and porosity blockage and the reduction of basic oxides and VM. Such results signified that the combustion of heavier MRD coal is challenging compared to lighter MRD coal. The higher value of ΔS infers that a chemical reaction is far away from its thermodynamic equilibrium. The higher ΔS containing fuel requires a shorter reaction time and rapidly produces an activated complex. ΔS value for 1.25 MRD coal is higher (−114.80 J/mol.K) and decreases from −114.80 to −182.07 J/mol.K with the increase of MRD from 1.25 to 2.20. Such a decrease in ΔS was due to higher ash thickness, which creates hurdles in oxygen diffusion. Overall, thermodynamic parameters indicate that lighter coal ignition and combustion are easier than heavier coal.