In the thermodynamics analysis of diffusion in spark plasma sintering (SPS) welding of Cr3C2 (chromium carbide) and Ni (nickel), various thermodynamic principles and concepts are applied to understand the heat and mass transfer processes involved. SPS is a specialized technique used to consolidate powders into dense materials using pulsed direct current and pressure.
The focus of the analysis is on diffusion, which refers to the movement of atoms or molecules from regions of high concentration to regions of low concentration. Diffusion plays a crucial role in the welding process of Cr3C2 and Ni, as it influences the formation of interfacial bonds between the particles.
Thermodynamic analysis involves examining the energy changes and driving forces associated with diffusion during the SPS welding process. This analysis aims to determine the factors that govern the diffusion process, such as temperature, pressure, concentration gradients, and material properties.
By studying the thermodynamics of diffusion, researchers can gain insights into the kinetics and mechanisms of atomic or molecular movement, as well as the resulting microstructural changes and bonding at the interfaces between Cr3C2 and Ni particles. This knowledge helps optimize the SPS welding process parameters and improve the quality and properties of the welded material.
Key aspects explored in the thermodynamics analysis may include heat transfer mechanisms, such as Joule heating during SPS, and mass transfer phenomena, such as atomic diffusion of Cr, C, and Ni species. The analysis may also consider thermodynamic properties of the materials involved, such as melting points, phase diagrams, and chemical potential gradients, to understand the driving forces for diffusion.
Overall, the thermodynamics analysis of diffusion in spark plasma sintering welding of Cr3C2 and Ni provides a deeper understanding of the fundamental principles governing the welding process, aiding in the development of advanced materials with enhanced properties and performance.
Experimental Study of an Atmospheric Pressure Dielectric Barrier Discharge an...IJERA Editor
A homogeneous dielectric barrier discharge (DBD) in argon was produced by applying high voltage A.C. source of potential difference (0-20) kV operating at a frequency of 10-30 kHz across two parallel plate electrodes with glass as dielectric barrier. The discharge was characterized by optical emission spectroscopy (OES) and electrical measurement. Four argon emission lines from the discharge were analyzed and the electron temperature was estimated by line intensity ratio method. The electron density in the discharge was estimated by power balance method. An investigation of the effect of inter-electrode distance on the electron density was made. The results showed that the electron temperature is less than 1 eV and the electron density is of the order of 1011cm-3 which varied with the inter electrode distance. Discharge was applied for surface modification of polyethylene terepthalate (PET). Modified surfaces were studied by contact angle measurement and FTIR spectroscopy.
Experimental Study of an Atmospheric Pressure Dielectric Barrier Discharge an...IJERA Editor
A homogeneous dielectric barrier discharge (DBD) in argon was produced by applying high voltage A.C. source of potential difference (0-20) kV operating at a frequency of 10-30 kHz across two parallel plate electrodes with glass as dielectric barrier. The discharge was characterized by optical emission spectroscopy (OES) and electrical measurement. Four argon emission lines from the discharge were analyzed and the electron temperature was estimated by line intensity ratio method. The electron density in the discharge was estimated by power balance method. An investigation of the effect of inter-electrode distance on the electron density was made. The results showed that the electron temperature is less than 1 eV and the electron density is of the order of 1011cm-3 which varied with the inter electrode distance. Discharge was applied for surface modification of polyethylene terepthalate (PET). Modified surfaces were studied by contact angle measurement and FTIR spectroscopy.
Natural Convection and Entropy Generation in Γ-Shaped Enclosure Using Lattice...A Behzadmehr
This work presents a numerical analysis of entropy generation in Γ-Shaped enclosure that was submitted to the natural convection process using a simple thermal lattice Boltzmann method (TLBM) with the Boussinesq approximation. A 2D thermal lattice Boltzmann method with 9 velocities, D2Q9, is used to solve the thermal flow problem. The simulations are performed at a constant Prandtl number (Pr = 0.71) and Rayleigh numbers ranging from 103 to 106 at the macroscopic scale (Kn = 10-4). In every case, an appropriate value of the characteristic velocity is chosen using a simple model based on the kinetic theory. By considering the obtained dimensionless velocity and temperature values, the distributions of entropy generation due to heat transfer and fluid friction are determined. It is found that for an enclosure with high value of Rayleigh number (i.e., Ra=105), the total entropy generation due to fluid friction and total Nu number increases with decreasing the aspect ratio.
Experimental Study of an Atmospheric Pressure Dielectric Barrier Discharge an...IJERA Editor
A homogeneous dielectric barrier discharge (DBD) in argon was produced by applying high voltage A.C. source of potential difference (0-20) kV operating at a frequency of 10-30 kHz across two parallel plate electrodes with glass as dielectric barrier. The discharge was characterized by optical emission spectroscopy (OES) and electrical measurement. Four argon emission lines from the discharge were analyzed and the electron temperature was estimated by line intensity ratio method. The electron density in the discharge was estimated by power balance method. An investigation of the effect of inter-electrode distance on the electron density was made. The results showed that the electron temperature is less than 1 eV and the electron density is of the order of 1011cm-3 which varied with the inter electrode distance. Discharge was applied for surface modification of polyethylene terepthalate (PET). Modified surfaces were studied by contact angle measurement and FTIR spectroscopy.
Experimental Study of an Atmospheric Pressure Dielectric Barrier Discharge an...IJERA Editor
A homogeneous dielectric barrier discharge (DBD) in argon was produced by applying high voltage A.C. source of potential difference (0-20) kV operating at a frequency of 10-30 kHz across two parallel plate electrodes with glass as dielectric barrier. The discharge was characterized by optical emission spectroscopy (OES) and electrical measurement. Four argon emission lines from the discharge were analyzed and the electron temperature was estimated by line intensity ratio method. The electron density in the discharge was estimated by power balance method. An investigation of the effect of inter-electrode distance on the electron density was made. The results showed that the electron temperature is less than 1 eV and the electron density is of the order of 1011cm-3 which varied with the inter electrode distance. Discharge was applied for surface modification of polyethylene terepthalate (PET). Modified surfaces were studied by contact angle measurement and FTIR spectroscopy.
Natural Convection and Entropy Generation in Γ-Shaped Enclosure Using Lattice...A Behzadmehr
This work presents a numerical analysis of entropy generation in Γ-Shaped enclosure that was submitted to the natural convection process using a simple thermal lattice Boltzmann method (TLBM) with the Boussinesq approximation. A 2D thermal lattice Boltzmann method with 9 velocities, D2Q9, is used to solve the thermal flow problem. The simulations are performed at a constant Prandtl number (Pr = 0.71) and Rayleigh numbers ranging from 103 to 106 at the macroscopic scale (Kn = 10-4). In every case, an appropriate value of the characteristic velocity is chosen using a simple model based on the kinetic theory. By considering the obtained dimensionless velocity and temperature values, the distributions of entropy generation due to heat transfer and fluid friction are determined. It is found that for an enclosure with high value of Rayleigh number (i.e., Ra=105), the total entropy generation due to fluid friction and total Nu number increases with decreasing the aspect ratio.
technoloTwo dimensional numerical simulation of the combined heat transfer in...ijmech
A numerical investigation was conducted to analyze the flow field and heat transfer characteristics in a vertical channel withradiation and blowing from the wall. Hydrodynamic behaviour and heat transfer results are obtained by the solution of the complete Navier–Stokesand energy equations using a control volume finite element method. Turbulent flow with "Low Reynolds Spalart-Allmaras Turbulence Model" and radiation with "Discrete Transfer Radiation Method" had been modeled. In order to have a complete survey, this article has a wide range of study in different domains including velocity profiles at different locations, turbulent viscosity, shear stress, suctioned mass flow rate in different magnitude of the input
Rayleigh number, blowing Reynoldsnumber, radiation parameter, Prandtl number, the ratio of length to width and also ratio of opening thickness to width of the channel. In addition, effects of variation in any of the above non-dimensional numbers on parameters of the flow are clearly illustrated. At the end resultants had been compared with experimental data which demonstrated that in the present study, results have a great accuracy, relative errors are very small and the curve portraits are in a great
agreement with real experiments.
Experiment on single-mode feedback control of oscillatory thermocapillary con...IJERA Editor
Feedback control was carried out on nonlinear thermocapillary convections in a half-zone liquid bridge of a high
Prandtl number fluid under normal gravity. In the liquid bridge, the convection changed from a two-dimensional
steady flow to a three-dimensional oscillatory flow at a critical temperature difference. Feedback control was
realized by locally modifying the free surface temperature using local temperature measured at different
positions. The present study aims to confirm whether the control method can effectively suppress oscillatory
flows with every modal structure. Consequently, the control was theoretically verified to be effective for
oscillatory flows with every modal structure in a high Marangoni number range.
Optimizing the-performance-of-a-standing-wave-loudspeaker-driven-thermoacoust...محمود الأمير
This paper investigates the design and optimization steps of a thermoacoustic refrigerator. Matlab code will be used for
optimizing the stack length and its position. DeltaEC version 6.3b11 will be used to do the code used for simulating the refrigerator to
identify the optimized operating conditions such as the mean pressure and the oscillating pressure. Behavior of changing the operating conditions effect on the performance is discussed.
Electrical properties of Ni0.4Mg0.6Fe2O4 ferritesIJERA Editor
Ni0.4Mg0.6Fe2O4 Ceramic samples were prepared by conventional double sintering approach and sintered at 1300oC/4 h. These ferrites are further characterized using X-ray diffractometer. The diffraction study reveals that the present compound shows perfect single phase cubic spinel structure. In addition, the behavior of distinct electrical properties such as dielectric constant (ε'), dielectric loss (ε") and ac-conductivity (ζac) as a function frequency as well as temperature is analyzed using the LCR controller.
New Mexico State University 1
New Mexico State University
Mechanical & Aerospace Engineering Department
Experimental Methods II
ME 445
LAB Exercise-4
TIME FOR BRIDGEWIRE BREAK
4.1 Objective
To apply the principles of heat transfer to estimate the break time of a resistive wire through
which a constant electric current is flowing.
Through this experiment, students will theoretically estimate the time using energy
balance equations.
Apply linear regression to fit manufacturer’s data with the model to deduce unknown
heat transfer parameters.
Predictions will be verified or contradicted by experimental measurement.
4.2 Theoretical Background
The physical representation of the problem is shown in the following figure:
Figure 4.0.1: Physical representation of the wire
A wire of length L and diameter D is considered. Due to the passage of electric current through
the wire, heat is generated internally. If radiation and convective heat loss are presumed as the
principal heat loss mechanisms, the energy balance for this problem, based on lumped mass for
the wire and infinite length, can be written:
Rate of change of Internal Energy (Qstored)
= Rate of Internal Energy Generation (Qgenerated) – Rate of Heat Loss (Qloss)
In the above equation, note that the heat input is not considered since no heat is being supplied
to the wire from its boundaries.
Symbolically, we can write the energy equation as:
TThATTAi
dt
dT
mc
wireswires
442
(4.1)
New Mexico State University 2
where,
m = mass of the wire = density of the wire * volume of the wire = ρV
Twire = Surface temperature of the wire
i = Current
R = Resistance of the wire
σ = Stefan-Boltzmann constant = 5.67 X 10
8
W/m
-2
K
-4
c = Specific heat capacity of the wire material
ε = Emissivity of the wire
As = Surface area of the wire
For present purposes the assumption is made that convection around the horizontal wire is fully
developed. The quantities m, c, I, , σ, As and Ts are presumed known. However, uncertainty
exists in the emissivity of the wire because of oxidized state is not precisely known, and the
convection coefficient is known to vary somewhat with size, and mean temperature across the
thermal boundary layer.
For the case of the wire which is to be used in this experiment, the manufacturer has provided
temperature versus current data for steady state. Hence, by using a multi-variable linear
regression, it is possible to use this data along with the steady state energy equation, to obtain
estimates for h and ε. However, when such an approach is taken, it is found that the value of ε
exceeds unity, an impossible condition. In order to resolv.
Research Inventy : International Journal of Engineering and Scienceinventy
Research Inventy : International Journal of Engineering and Science
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed
»Over the last two decades several patents and research papers have reported purported practical methods to extract useful energy from the vacuum. I describe the inventions and analyze the underlying physics. From an analysis based on first principles it is clear that most of the inventions have fundamental errors and cannot work. The basic concept of harvesting zero-point energy remains viable, and at least one patented concept might work.
The vacuum is filled with a high density of zero-point energy, in the form of modes (vibrational patterns) of electromagnetic field. Over the last eight decades it has become clear that this zero-point field (ZPF) vacuum energy is not simply a mathematical formalism, but produces demonstrable effects on physical systems. Along with that realization has come the desire to extract energy from the ZPF.
One set of methods use nonlinear elements to convert the ZPF into a usable form. A rectifier (used to convert AC to DC) is a strongly nonlinear element. One patent makes use of antennas to capture the ZPF. This energy is then rectified and used. Another set of inventions simply rectify fluctuations (noise) in electronic elements as an extraction method. Using a detailed balance argument, I show that these methods cannot work.
Another set of patents describe using a Casimir cavity to mechanically extract energy from the ZPF. A Casimir cavity consists of two closely space reflecting plates that exclude ZPF electromagnetic modes having wavelengths larger than twice the gap spacing. The result is that the imbalance in the density of the ZPF inside and outside the cavity causes the plates to be attracted to each other. This attractive potential can be used, but only once. To produce power continuously, a method must be devised to form a reciprocating Casimir engine. The patents purport to switch off the Casimir attraction while the plates are pulled apart, so that they can repeatedly accelerate together and produce power. This approach is shown to be fundamentally flawed, and cannot produce power continuously.
A recently issued patent describes a method by which vacuum energy is extracted from gas flowing through a Casimir cavity. According to stochastic electrodynamics, the electronic orbitals in atoms are supported by ambient ZPF. When the gas atoms are pumped into a Casimir cavity, where long-wavelength ZPF modes are excluded, the electrons spin down into lower orbitals, releasing energy. This energy is harvested in a local absorber. When the electrons exit the Casimir cavity, they are re-energized to their original orbitals by the ambient ZPF. The process is repeated to produce continuous power. This method does not suffer from the fundamental flaws of the other approaches, and might work.«
The understanding of two-phase flow and heat transfer
with phase change in minichannels is needed for the design and
optimization of heat exchangers and other industrial
applications. In this study a three-dimensional numerical model
has been developed to predict filmwise condensation heat
transfer inside a rectangular minichannel. The Volume of Fluid
(VOF) method is used to track the vapor-liquid interface. The
modified High Resolution Interface Capture (HRIC) scheme is
employed to keep the interface sharp. The governing equations
and the VOF equation with relevant source terms for
condensation are solved. The surface tension is taken into
account in the modeling and it is evaluated by the Continuum
Surface Force (CSF) approach. The simulation is performed
using the CFD software package, ANSYS FLUENT, and an inhouse
developed code. This in-house code is specifically
developed to calculate the source terms associated with phase
change. These terms are deduced from Hertz-Knudsen equation
based on the kinetic gas theory. The numerical results are
validated with data obtained from the open literature. The
standard k-ω model is applied to model the turbulence through
both the liquid and vapor phase. The numerical results show
that surface tension plays an important role in the condensation
heat transfer process. Heat transfer enhancement is obtained
due to the presence of the corners. The surface tension pulls the
liquid towards the corners and reduces the average thermal
resistance in the cross section.
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
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Similar to Thermodynamics analysis of diffusion in spark plasma sintering welding Cr3C2 and Ni.pptx
technoloTwo dimensional numerical simulation of the combined heat transfer in...ijmech
A numerical investigation was conducted to analyze the flow field and heat transfer characteristics in a vertical channel withradiation and blowing from the wall. Hydrodynamic behaviour and heat transfer results are obtained by the solution of the complete Navier–Stokesand energy equations using a control volume finite element method. Turbulent flow with "Low Reynolds Spalart-Allmaras Turbulence Model" and radiation with "Discrete Transfer Radiation Method" had been modeled. In order to have a complete survey, this article has a wide range of study in different domains including velocity profiles at different locations, turbulent viscosity, shear stress, suctioned mass flow rate in different magnitude of the input
Rayleigh number, blowing Reynoldsnumber, radiation parameter, Prandtl number, the ratio of length to width and also ratio of opening thickness to width of the channel. In addition, effects of variation in any of the above non-dimensional numbers on parameters of the flow are clearly illustrated. At the end resultants had been compared with experimental data which demonstrated that in the present study, results have a great accuracy, relative errors are very small and the curve portraits are in a great
agreement with real experiments.
Experiment on single-mode feedback control of oscillatory thermocapillary con...IJERA Editor
Feedback control was carried out on nonlinear thermocapillary convections in a half-zone liquid bridge of a high
Prandtl number fluid under normal gravity. In the liquid bridge, the convection changed from a two-dimensional
steady flow to a three-dimensional oscillatory flow at a critical temperature difference. Feedback control was
realized by locally modifying the free surface temperature using local temperature measured at different
positions. The present study aims to confirm whether the control method can effectively suppress oscillatory
flows with every modal structure. Consequently, the control was theoretically verified to be effective for
oscillatory flows with every modal structure in a high Marangoni number range.
Optimizing the-performance-of-a-standing-wave-loudspeaker-driven-thermoacoust...محمود الأمير
This paper investigates the design and optimization steps of a thermoacoustic refrigerator. Matlab code will be used for
optimizing the stack length and its position. DeltaEC version 6.3b11 will be used to do the code used for simulating the refrigerator to
identify the optimized operating conditions such as the mean pressure and the oscillating pressure. Behavior of changing the operating conditions effect on the performance is discussed.
Electrical properties of Ni0.4Mg0.6Fe2O4 ferritesIJERA Editor
Ni0.4Mg0.6Fe2O4 Ceramic samples were prepared by conventional double sintering approach and sintered at 1300oC/4 h. These ferrites are further characterized using X-ray diffractometer. The diffraction study reveals that the present compound shows perfect single phase cubic spinel structure. In addition, the behavior of distinct electrical properties such as dielectric constant (ε'), dielectric loss (ε") and ac-conductivity (ζac) as a function frequency as well as temperature is analyzed using the LCR controller.
New Mexico State University 1
New Mexico State University
Mechanical & Aerospace Engineering Department
Experimental Methods II
ME 445
LAB Exercise-4
TIME FOR BRIDGEWIRE BREAK
4.1 Objective
To apply the principles of heat transfer to estimate the break time of a resistive wire through
which a constant electric current is flowing.
Through this experiment, students will theoretically estimate the time using energy
balance equations.
Apply linear regression to fit manufacturer’s data with the model to deduce unknown
heat transfer parameters.
Predictions will be verified or contradicted by experimental measurement.
4.2 Theoretical Background
The physical representation of the problem is shown in the following figure:
Figure 4.0.1: Physical representation of the wire
A wire of length L and diameter D is considered. Due to the passage of electric current through
the wire, heat is generated internally. If radiation and convective heat loss are presumed as the
principal heat loss mechanisms, the energy balance for this problem, based on lumped mass for
the wire and infinite length, can be written:
Rate of change of Internal Energy (Qstored)
= Rate of Internal Energy Generation (Qgenerated) – Rate of Heat Loss (Qloss)
In the above equation, note that the heat input is not considered since no heat is being supplied
to the wire from its boundaries.
Symbolically, we can write the energy equation as:
TThATTAi
dt
dT
mc
wireswires
442
(4.1)
New Mexico State University 2
where,
m = mass of the wire = density of the wire * volume of the wire = ρV
Twire = Surface temperature of the wire
i = Current
R = Resistance of the wire
σ = Stefan-Boltzmann constant = 5.67 X 10
8
W/m
-2
K
-4
c = Specific heat capacity of the wire material
ε = Emissivity of the wire
As = Surface area of the wire
For present purposes the assumption is made that convection around the horizontal wire is fully
developed. The quantities m, c, I, , σ, As and Ts are presumed known. However, uncertainty
exists in the emissivity of the wire because of oxidized state is not precisely known, and the
convection coefficient is known to vary somewhat with size, and mean temperature across the
thermal boundary layer.
For the case of the wire which is to be used in this experiment, the manufacturer has provided
temperature versus current data for steady state. Hence, by using a multi-variable linear
regression, it is possible to use this data along with the steady state energy equation, to obtain
estimates for h and ε. However, when such an approach is taken, it is found that the value of ε
exceeds unity, an impossible condition. In order to resolv.
Research Inventy : International Journal of Engineering and Scienceinventy
Research Inventy : International Journal of Engineering and Science
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed
»Over the last two decades several patents and research papers have reported purported practical methods to extract useful energy from the vacuum. I describe the inventions and analyze the underlying physics. From an analysis based on first principles it is clear that most of the inventions have fundamental errors and cannot work. The basic concept of harvesting zero-point energy remains viable, and at least one patented concept might work.
The vacuum is filled with a high density of zero-point energy, in the form of modes (vibrational patterns) of electromagnetic field. Over the last eight decades it has become clear that this zero-point field (ZPF) vacuum energy is not simply a mathematical formalism, but produces demonstrable effects on physical systems. Along with that realization has come the desire to extract energy from the ZPF.
One set of methods use nonlinear elements to convert the ZPF into a usable form. A rectifier (used to convert AC to DC) is a strongly nonlinear element. One patent makes use of antennas to capture the ZPF. This energy is then rectified and used. Another set of inventions simply rectify fluctuations (noise) in electronic elements as an extraction method. Using a detailed balance argument, I show that these methods cannot work.
Another set of patents describe using a Casimir cavity to mechanically extract energy from the ZPF. A Casimir cavity consists of two closely space reflecting plates that exclude ZPF electromagnetic modes having wavelengths larger than twice the gap spacing. The result is that the imbalance in the density of the ZPF inside and outside the cavity causes the plates to be attracted to each other. This attractive potential can be used, but only once. To produce power continuously, a method must be devised to form a reciprocating Casimir engine. The patents purport to switch off the Casimir attraction while the plates are pulled apart, so that they can repeatedly accelerate together and produce power. This approach is shown to be fundamentally flawed, and cannot produce power continuously.
A recently issued patent describes a method by which vacuum energy is extracted from gas flowing through a Casimir cavity. According to stochastic electrodynamics, the electronic orbitals in atoms are supported by ambient ZPF. When the gas atoms are pumped into a Casimir cavity, where long-wavelength ZPF modes are excluded, the electrons spin down into lower orbitals, releasing energy. This energy is harvested in a local absorber. When the electrons exit the Casimir cavity, they are re-energized to their original orbitals by the ambient ZPF. The process is repeated to produce continuous power. This method does not suffer from the fundamental flaws of the other approaches, and might work.«
The understanding of two-phase flow and heat transfer
with phase change in minichannels is needed for the design and
optimization of heat exchangers and other industrial
applications. In this study a three-dimensional numerical model
has been developed to predict filmwise condensation heat
transfer inside a rectangular minichannel. The Volume of Fluid
(VOF) method is used to track the vapor-liquid interface. The
modified High Resolution Interface Capture (HRIC) scheme is
employed to keep the interface sharp. The governing equations
and the VOF equation with relevant source terms for
condensation are solved. The surface tension is taken into
account in the modeling and it is evaluated by the Continuum
Surface Force (CSF) approach. The simulation is performed
using the CFD software package, ANSYS FLUENT, and an inhouse
developed code. This in-house code is specifically
developed to calculate the source terms associated with phase
change. These terms are deduced from Hertz-Knudsen equation
based on the kinetic gas theory. The numerical results are
validated with data obtained from the open literature. The
standard k-ω model is applied to model the turbulence through
both the liquid and vapor phase. The numerical results show
that surface tension plays an important role in the condensation
heat transfer process. Heat transfer enhancement is obtained
due to the presence of the corners. The surface tension pulls the
liquid towards the corners and reduces the average thermal
resistance in the cross section.
Similar to Thermodynamics analysis of diffusion in spark plasma sintering welding Cr3C2 and Ni.pptx (20)
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This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
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Examination System is very useful for Teachers/Professors. As in the teaching profession, you are responsible for writing question papers. In the conventional method, you write the question paper on paper, keep question papers separate from answers and all this information you have to keep in a locker to avoid unauthorized access. Using the Examination System you can create a question paper and everything will be written to a single exam file in encrypted format. You can set the General and Administrator password to avoid unauthorized access to your question paper. Every time you start the examination, the program shuffles all the questions and selects them randomly from the database, which reduces the chances of memorizing the questions.
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A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
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4. particles are only 1 to 100 nm across, different properties
begin to arise.
Introduction
the surface area to volume is insignificant in relation to the
number of atoms in the bulk.
commercial grade zinc oxide has a surface area range of 2.5
to 12 m2/g while nanoparticle zinc oxide can have surface
areas as high as 54 m2/g .
superior UV blocking properties
small size, making it very important to be able to determine
their surface area.
5. Hungarian chemist Stephen Brunauer (1903-
1986)
Hungarian born theoretical physicist Edward Teller (1908 –
2003)
American chemical engineer Paul H. Emmett (1900 -
1985)
American chemist and physicist Irving Langmuir (1881 - 1957)
7. The Langmuir theory is based on the
following assumptions:
• All surface sites have the same
adsorption energy for the
adsorbate
• Adsorption of the solvent at one
site occurs independently of
adsorption at neighboring sites.
• Activity of adsorbate is directly
proportional to its concentration.
• Adsorbates form a monolayer.
• Each active site can be occupied
only by one particle.
𝜃 =
𝛼. 𝑃
1 + 𝛼. 𝑃
Schematic of the adsorption of gas
molecules onto the surface of a
sample showing
(a) the monolayer adsorption model
assumed by the Langmuir theory
and
(b) (b) s the multilayer adsorption
model assumed by the BET
8. In BET surface area analysis,
nitrogen is usually used because
of its availability in high purity and
its strong interaction with most
solids. Because the interaction
between gaseous and solid
phases is usually weak, the
surface is cooled using liquid
N2 to obtain detectable amounts
of adsorption.
Highly precise and accurate
pressure transducers monitor
the pressure changes due to the
adsorption process. After the
adsorption layers are formed,
the sample is removed from the
nitrogen atmosphere and heated
to cause the adsorbed nitrogen
to be released from the material
and quantified.
9. Gas adsorption or Nitrogen adsorption
Directly measures surface area & pore size distribution
BET theory deviates from ideal to actual analysis
Homogeneous surface
No lateral interactions between molecules
Uppermost layer is in equilibrium with vapour phase
First and Higher layer: Heat adsorption
All surface sites have same adsorption energy for adsorbate
Adsorption on the adsorbent occurs in infinite layers
The theory can be applied to each layer
11. SPS current passes through the graphic die or the as-sintered
specimens and heats them through Joule heating. This endows
SPS with the following two remarkable advantages: low sintering
temperature and short sintering time relative to conventional
methods
it was sometimes found that in addition to the Coulomb force,
an extra driving force might exist enhancing the diffusion along
the direction of electron motion and inhibiting in the reverse
direction despite the type of charge owned by the diffusion
particle, thus producing a phenomenon similar to an “electron
wind.”
assumed that the bypassing current in SPS may reduce the activation energy
during processing by enhancing the mobility of defects and increasing the
point defect concentration. However, whether the small voltage of the
bypassing current, within 20V in SPS, did the same work with that in PAS,
about 10×10+3
V, was not discussed.
13. ● Initially, the plates were fine polished and
ultrasonically cleaned successively with
hydrochloric acid and alcohol. Further, the
sandwich diffusion couples were placed in the SPS
apparatus.
● To improve the precision of measuring the temperature, a K-type thermal couple
was pushed into the die as shown in Fig. 1. The tip of the K-type thermal couple
was located in line with the Cr3C2 plate and very close to it.
FIG. 1. The assembling sketch of the
specimens, graphic die, and thermal couple;
(a) with bypassing current and
(b) without bypassing current.
14. Owing to the small gap between
the heater and the specimens and
the excellent thermal conductivity
of insulating boron nitride plates, a
similar heating rate of about 100 C
min1 was achieved in this setup
(a) and (b), with or without
bypassing current, respectively.
The holding temperature varied
from 900 to 1200 C, with a
holding time of 10 min and was
followed by natural cooling to
room temperature. A small
pressure of about 5MPa was
used to ensure stable contact of
all the components described
above. Moreover, all runs were
performed under vacuum with a
residual pressure of less than 10
Pa.
15. After cutting, the microstructure of welded specimens was investigated
by scanning electron microscopy (SEM) and elemental distribution along
the height by energy dispersive X-ray spectroscopy (EDS) at the
interface. Ten parallel scanning lines were performed in the EDS
analysis in every specimen. The phase at the welding interface was
analyzed by X-ray diffraction (XRD) with the specimens prepared by
layer-by-layer polishing methods.
17. FIG. 2. The typical microstructure, phase analysis, and elemental distribution
images of the welded Cr3C2/Ni couples.
(a) SEM image of the upper interface at 1200 C;
(b) SEM image of the lower interface at 1200 C;
(c) XRD pattern of different samples;
(d) The EDS of the upper interface at 1200 C).
18. FIG. 3. Diffusion thicknesses and related empirical diffusion
coefficients vs. welding temperature
(a) Diffusion distances;
(b) Diffusion coefficients).
19. ∁(0,0)= 1 = ∁0
∁(𝑥,𝑡)= ∁0erfc(𝑥
2 𝐷𝑡
)
● Clearly, the diffusion distance and the diffusion coefficient both increase with
temperature in all runs, and exhibit obvious dependence on the current and its direction.
● At the welding temperature of 1200 ℃ and holding time of 10 min, the diffusion distance
and the diffusion coefficient with bypassing current were found to be 18 𝜇𝑚 and 8.25×
10−18
𝑚2
𝑠−1
, respectively, for the upper interfaces, and 12 𝜇𝑚 and 2.52× 10−18
𝑚2
𝑠−1
,
for the lower interfaces.
𝐷 = 𝐷0exp(
−𝐸𝐴
𝐾𝑇
)
● in which EA is the activation energy for diffusion, T is the absolute
temperature, and k is the Boltzmann constant. Obviously, there
must be some other factor besides the temperature relating the
current which also affects the diffusion; therefore, the EA also
changed.
20. An effect depending on current direction, for e.g., coulomb
force or “electron wind,” and an effect independent of current
direction possibly both occurred in this study. Moreover, the
contribution of the effect independent of current direction
offsets that of the effect depending on current direction at the
lower interface with bypassing current. It is extremely difficult
to separate the contribution of the bypassing current
(Coulomb force, the “electron wind,” the inducing defect, and
the local high temperature or temperature gradient) to the
atomic diffusion qualitatively; therefore, quantitative analysis
is usually required.
22. Herein, we proposed a new model based on the Coulomb force and the local
high temperature and LTG. According to Fick’s equation relative to steady
diffusion, the atomic flux with bypassing current can be written as follows:
𝐽𝑖 = −
𝐷𝐶𝑖
𝑅
𝜕
𝜇𝑖
𝑇
𝜕𝑥
±
𝐹𝑍𝑖
∗
𝐸
𝑇
1
2
3
4
5
6
𝜕
𝜇𝑖
𝑇
𝜕𝑥
=
1
𝑇
𝜕𝜇𝑖
𝜕𝑥 𝑇
−
𝜇𝑖𝜕𝑇
𝑇2𝜕𝑥
𝜇𝑖|𝑇 = 𝑅𝑇𝑙𝑛𝐶𝑖
𝜕𝜇𝑖
𝜕𝑥 𝑇
=
𝑅𝑇𝜕𝐶𝑖
𝐶𝑖𝜕𝑥
𝐽𝑖 = −
𝐷𝐶𝑖
𝑇𝑅
𝑅𝑇𝜕𝐶𝑖
𝐶𝑖𝜕𝑥
− 𝑅𝑙𝑛𝐶𝑖
𝜕𝑇
𝜕𝑥
± 𝐹𝑍𝑖
∗
𝐸
𝐾𝑐𝐴𝑐
𝜕𝑇
𝜕𝑥
= 𝐼2
𝑅∗
24. FIG. 4. Electric resistance of the couple Ni-x%Cr3C2/Ni (X=10,
30, 50, 70, 90, and 100) welded at 800℃
FIG. 5. The experimental and calculated diffusion
coefficient ratios as functions of temperature.
FIG. 6. Profile of ∆D ~ 𝐼2
with the experimental data from
Fig. 5.
26. Results showed that the Ni diffusion coefficient in
Cr3C2 with a bypassing current of 1086A at a
temperature of 1200℃was 8.25× 10−18
𝑚2
𝑠−1
and
2.52 × 10−18
𝑚2
𝑠−1
at the upper and lower
interfaces of the sandwich couple, respectively.
The diffusion coefficient for both interfaces without
a bypassing current was 1.69× 10−18
𝑚2
𝑠−1
.
the bypassing current on the diffusion
involved a symmetric contribution from the
Coulomb force and a directionally
independent positive contribution from an
unknown driving force. this unknown X-
force was explained through a newly
proposed model based on the LTG.
A mass diffusion equation with
contributions from the traditional
concentration gradient, Coulomb force,
and LTG, which was caused by the
bypassing current, was derived within the
traditional physical theory.
Both the qualitative and quantitative analyses of
the as-deduced equation showed good
consistency with the experimental results in the
present study and with previous results from the
literature reports.