Principle Of Conservation Of Energy Research Articles

Synchronizing Teaching Resources of Energy Conservation Principle in Mechanical Engineering Courses- Year 2 Updates

The conservation of energy, mass, and momentum are three governing laws of physics that are regularly uttered in teaching engineering courses. Mechanical energies in the form of kinetic and potential forms are the most common forms of energy in dynamics. Fluid flow energies relating to pressure, velocity, elevation, fluid friction, pump, and turbine are covered in fluid dynamics. In thermodynamics course, the first law deals with heat energy and work that can alter internal energy in a system. In all these courses, the conservation of energy states that the amount of energy remains constant, that means that energy is neither created nor destroyed but transferable from one form to another, keeping the total energy same within a fixed domain. Students are initially exposed to energy balance equation in their first Thermodynamics course. In this course, emphasis is placed upon those parameters of specific interest related to energy to this subject. We attempted to tie the concepts of the energy balance equation through 1st Law in thermodynamics to those emphasized in Fluid Mechanics. This was accomplished by taking the students from the starting point of the thermodynamics’ first law for Energy Balance equation to the finished Fluid Mechanics’ Bernoulli’s equation. In the following semester, students were again taken through the process of converting the 1st Law of thermodynamics to Bernoulli’s equation of fluid mechanics. Direct and indirect assessments were then conducted to measure students’ understanding on the energy and its conservation. Through a series of questionnaire and their feedback, Students were found to be more knowledgeable in the conservation of energy through the synchronization of energy balance concepts in these two courses. This presentation is a part of work-in-progress project that we first presented at 2022 WVAS meeting.

Gyroscope oscillation depends on a rotor speed velocity

In engineering, all moving rotating objects exhibit gyroscopic effects resulting from the action of an external torque on a rotating object. Gyroscopic effects are the action of a set of inertial moments and movements of an object around three axes of a three-dimensional Cartesian coordinate system. Moments of inertia are created by centrifugal and Coriolis forces, as well as the moment of change in angular momentum, which is expressed by their kinetic energy. The values of the moments of inertia directly depend on the speed of rotation of the object and its rotation around the axes. A short-term effect of an external load on a running gyroscope with displaced support can be manifested by its oscillations. The physics of gyroscope oscillations is not well explained in publications. This article describes the oscillations of a gyroscope by the action of the external torque which is its potential energy converting into kinetic energy of the inertial torques of the gyroscope. The conversion is carried out by the principle of mechanical energy conservation which is the same as for oscillations of a spring with a load.

Study of the Failure Mechanism of an Integrated Injection-Production String in Thermal Recovery Wells for Heavy Oil

The integrated injection-production string is the core tool used in thermal recovery wells for heavy oil, the mechanical behavior of which is complex due to the coupling effect of downhole temperature and pressure and the load induced by steam huff and puff operations. In this paper, an analysis model that calculates the temperature and pressure field during steam huff and puff operations has been established based on the basic principles of energy conservation and heat transfer. Then, the force distribution and strength check of the integrated injection-production string were analyzed. The fatigue damage of the string was evaluated by considering dynamic loads during the injection process. The corrosion life of the string was predicted. Finally, the failure mechanism of the integrated injection-production string in thermal recovery wells for heavy oil was illustrated. The results showed that the strength of the string and vibration fatigue are not the main causes of failure, but corrosion is the main reason for string failure. The residual strength of the corroded string was greatly reduced, which is the fundamental reason for the failure of the string. This paper is of guiding significance to the optimization of design and safety evaluations of the integrated injection-production string in thermal recovery wells for heavy oil.

Fragment theoretical model of concrete blocks subjected to blast loads

Concrete, a typical engineering construction material, will fracture and fragment when subjected to blast loads. In this study, the blast experiments on concrete blocks were carried out using 30kg of explosive B at different stand-off distances, and the concrete fragments were recovered, sieved, weighed, and counted to obtain information of the fragments in different particle size groups. Moreover, the propagation process of the blast energy was analyzed based on the blast theory, and the deformation energy of the concrete blocks subjected to the blast loads was calculated according to the deformation energy theory. The Griffith fracture theory was employed to estimate the energy dissipation during the fragmentation of the concrete blocks, and the initial kinetic energy of the concrete fragments was determined by combining it with the kinematics theory. Subsequently, a fragment theoretical model was developed based on the principle of energy conservation. The validity of the proposed fragment theoretical model was verified by comparing the statistical data of the blast experiments. The present fragment theoretical model can predict the fragmentation degree of concrete members reasonably and effectively and calculate the particle sizes and quantity of concrete fragments under unknown blast load conditions.

Analytical solutions for thermal effects of suspension bridges based on a surrogate model with longitudinal restraint stiffness

Ambient temperature variation has a significant influence on the deformation of main cables and the internal force of towers of long-span suspension bridges. Currently, the finite element method (FEM) is mainly used for these calculations. This paper intends to present an analytical solution of the thermal effects on suspension bridges. First, three typical temperature patterns are defined. Then, a surrogate model is established by replacing the longitudinal restraint stiffness of the main cable and the tower lateral stiffness with a set of equivalent horizontal springs. The stiffnesses of the suspended cables are formulated according to the energy conservation principle, while the tower lateral stiffnesses are obtained by incorporating the pure bending and Euler buckling solutions, namely considering the effect of the axial force placed on the tower top. Following the force equilibrium conditions, two governing equations are built, which can calculate the variations in the longitudinal displacement of the tower top caused by the temperature variation. After that, some other significant thermal effects, such as the horizontal force of the main cable, the sag of the main cable and the bending moment of the tower bottom, are obtained. Finally, the analytical solution is verified through the field test data of the Tsing Ma Bridge in Hong Kong and the FEM results of four typical examples. The proposed surrogate model offers a quick and easy approach for thermal effect analysis with acceptable accuracy. It is helpful to clarify the mechanical nature of temperature effects to facilitate the preliminary bridge design.

A model of a nonisothermal two‐phase flow of compressible fluids

We introduce a simple model of the time evolution of a binary mixture of compressible fluids including the thermal effects. Despite its apparent simplicity, the model is thermodynamically consistent admitting an entropy balance equation. We introduce a suitable weak formulation of the problem based on a combination of the entropy inequality with the total energy conservation principle. Finally, we show compactness of any bounded family of weak solutions and establish a global existence result.

A Quasi-Statistical Approach to the Boltzmann Entropy Equation Based on a Novel Energy Conservation Principle

Boltzmann entropy equation is gained according to the statistical mechanics directly and general dependence between entropy and probability is obtained. Based on the second law of thermodynamics with a glance at the Boltzmann entropy equation, it can be deduced that physical processes are done in a direction that the probability of the system and total entropy increase. In fact, the possible process performing states and their entropy variations will be determined at a specific energy level. In this paper, an entropy equation is gained by using a new quasi-statistical approach to the physical processes as well as a novel energy conservation principle. The variation of the "energy structure equation”, as an equation to formulate the performed process using activated energy components of the system and their dependence, is studied in different possible paths by using the energy conservation principle directly. Despite the classical mechanics that all particles are studied, in the novel approach, "particular processes" as all processes that have the same active independent energy components are studied at "various conditions"; in other words, all conditions that same energy amount is applied to the system. One of the advantages of this novel approach is that the volume of the needed calculations will be decreased mainly in comparison with the Boltzmann entropy equation. Dependence of the entropy and rate of the energy components is gained from the novel energy conservation principle. The gained relation, expressed by energy components of the system, is considered with no constraints on the structure of the system but has a common basis with the Boltzmann entropy equation. In fact, by using a novel macroscopic-statistical approach, the entropy variation of a physical system is studied.

Dynamic properties of the attachment oscillator arising in the nanophysics

Abstract The attachment oscillator, which plays an important role in the nanophysics such as nano/microelectromechanical systems, molecular devices, and nanofibers, is studied in this work. With the help of the semi-inverse method, the variational principle is established, and the Hamiltonian of the system is correspondingly constructed based on the obtained variational principle. Then, according to the principle of energy conservation, the energy balance theory is implemented to seek for the amplitude–frequency relationship. As predicted, the obtained solution has a good agreement with the existing results, which shows that the presented method is simple but effective, and is expected to provide a new idea for the study of the nonlinear oscillator arising in the nanophysics.

Robust Frequency Domain Spline Adaptive Filtering Based on the Half-Quadratic Criterion: Performance Analysis and Applications

Frequency domain spline adaptive filters (FDSAF) have attracted a great deal of attention because of their enhanced computational efficiency. However, their performance will be extremely degraded in practical environments where non-Gaussian phenomena exist. In order to attain good robustness to non-Gaussian noises while ensuring a low computational burden, this paper proposes a frequency domain spline adaptive filtering algorithm based on the half-quadratic criterion (HQC), named FDSAF-HQC. Further, to offer a theoretical foundation for the proposed FDSAF-HQC, a detailed performance analysis based on the principle of energy conservation is conducted and then validated by simulations. Moreover, the computational complexity of FDSAF-HQC is evaluated and compared with other similar algorithms. Simulation results of nonlinear system identification corroborate the outstanding performance of the proposed FDSAF-HQC, i.e., better robustness and computational efficiency. The superiority of the proposed FDSAF-HQC is also supported by practical applications of echo cancellation and biological signal denoising.

A Uniform Model for Correcting Shortwave Downward Radiation Over Rugged Terrain at Various Scales

Shortwave downward radiation (SWDR) plays a major role in the material and energy balance of the Earth’s climate system. However, most of existing SWDR research and products assume that the surface is flat, ignoring the effect of topography. This approach introduces significant uncertainties in the calculated fluxes and smooths the spatial distribution of SWDR. This paper proposes a uniform shortwave topographic radiation model (USWTRM) based on the principle of energy conservation. To evaluate the USWTRM, we compared it with the large-scale remote sensing data and image simulation framework (LESS). The USWTRM performed better than the traditional method in most conditions. For clear-sky, when the SZA=0°, the relative root-mean-square error (rRMSE), relative bias (rbias), and R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of the USWTRM at 1-km were 0.1 %, 0.0 %, and 1.000, respectively. At SZAs of 20°, 40°, and 60°, the USWTRM also showed better results than the traditional method. Moreover, the USWTRM performed similarly at 3-km and 5-km as that of 1-km. For cloudy-sky, the rRMSE and rbias of the USWTRM at fine-scale were 3.5%, and 0.0%, respectively. At 1-km, the rRMSE and rbias of the USWTRM were 0.9%, and 0.5%, respectively. In particular, the USWTRM outperformed previous studies in accurately quantifying the SWDR over rugged areas, under both clear and cloudy skies. Overall, the analysis reveals that the USWTRM works well over mountainous regions in terms of reliable accuracy, applicability, and generalization. It provides a new perspective for accurately deriving topographic SWDR at various scales and significantly reduces radiation uncertainties over rugged terrain.

A New Virtual Inductance Control Method for Frequency Stabilization of Grid-Forming Virtual Synchronous Generators

Frequency stabilization is the premise of guaranteeing grid-friendly integration of virtual synchronous generator (VSG). Based on that premise, this article, focused on frequency stability, establishes the small signal model of grid-forming VSG system. At first, the mechanism of frequency oscillation occurring in system of active- and reactive-power coupling is analyzed by the defined feedback effect factor in this article. Besides, a new dynamic model is established for identifying dynamic interaction of voltage magnitudes and frequency by means of feedback effect. The analytical results of established models agree with that of eigenvalue analysis. Furthermore, a new virtual inductance control strategy is proposed to mitigate the unstable oscillation of frequency and powers, enhance damping performance, and improve stability margins. Unlike the conventional virtual inductance control, which is reliable on dual-loop control framework, the proposed virtual inductance control in this article is based on principle of energy conservation and can be applicable for the grid-forming inverter without inner dual-loop control structure. Finally, the proposed modeling as well as virtual inductance control method is experimentally verified.

On the Field Energy of Two Charges With Application to Electric Dipoles

This paper revisits the topic of electrostatic field energy due to a pair of the electric charges. Not only point-like charges but also charged spheres of radius R are studied. The self-energies as well as the interaction field energy are discussed in full detail. By combining two alternative didactic paths (one mathematical and the other based on energy conservation principles), it is shown that the interaction field energy (which is a volume integral of the energy density over the infinite space) is always equal to the potential energy, regardless of the nature of the electrical charges. For these two characteristic cases of electric charges (i.e., point-like and uniformly charged spheres), the location and the amount of the major part of the interaction field energy is discussed; the relevant factoids are documented in the form of two compact theorems in the Appendix. The case of non-uniformly charged spheres (i.e., spherical conductors) is also discussed to some extent. In addition to this general presentation, the particular case of the electric dipole is discussed, as a special case, accompanied with many numerical results.

Diagnosing Mental Models of Undergraduate Student and Physics Teachers: Study Case in the Momentum and Energy Conservation Principles Using Newton's Cradle

The Newton’s Cradle comprises a series of pendulums often used in physics classrooms to demonstrate the principles of conservation of momentum and kinetic energy in elastic collisions. By utilizing open-ended questions and several Newton’s cradle scenarios, this study aims to clarify how the Newton’s cradle can be used for assessing the mental models of the principles of conservation of momentum and energy. Interviews with 18 college students and five physics professors each lasted 30 to 45 minutes. Firstly, they were asked to explain how the Newton’s cradle works. Next, a scenario started with three balls with equal masses where one collides with the other two, they were asked to explain if the possible outcomes for a collision with initial momentum = mv1 + 0 + 0 and the final momentum = (-mv1/3) + (2mv1/3) + (2mv1/3). With a five-ball Newton’s Cradle, students were asked to explain the outcomes when 1) one collides with the other four, 2) two collide with the other three, 3) three collide with the other two, and 4) four collide with the last one. Their drawings and explanations dealing with the Newton’s cradle during the interviews were analyzed for their mental models and categorized into patterns. The results showed that both university students and physics teachers hold misinformed conceptions about conservation of momentum and energy and have unsound mental models in the context of Newton’s Cradle. We also found that they did not recognize that sound and heat or lack of exact alignment of the balls are factors accountable for loss of energy causing the Newton’s Cradle to depart from idealized situation. Based on the interview data, teaching principles of the conservation of momentum and energy through use of Newton’s cradle are deficient and curriculum review is suggested.

Deep-learning optimization and environmental assessment of nanomaterial's boosted hydrogen and power generation system combined with SOFC

Renewable energy sources are unquestionably required, given that the world's energy consumption is anticipated to increase significantly in the next decades. Besides, fuel cell converts chemical energy directly into electricity, making it the most efficient and environmentally friendly power source. This study examines the viability of producing electricity using a supercritical CO2 cycle, a methane digester, and a gas turbine. Applying the principles of exergetic balance, mass, energy conservation, and component-specific exergetic balance to each part of the power unit allow for a simulation of the power unit's efficiency. Furthermore, a parametric analysis is performed to establish how the relevant factors will affect the unit's functioning. The optimization algorithms are generated with the help of deep learning methods. It was found that the ratio of the compressor's pressure to the current density was the most crucial element in determining output power. Nanoparticles are used in fuel cells to enhance heat transfer and, thus, the generated power. Through optimization, one might find a product that is both the most cost-effective and energy-efficient option available. Artificial neural networks may be used as a mediator to help expedite the process of reaching optimum performance across several criteria. The optimal settings for the planned power plant are now being determined by studying the correlation between design factors and objective functions. Therefore, the second law's efficiency at its sweet spot was calculated at 61.8%. In the end, the system at its optimum point was found to have an exergo-environmental index of 0.436.

Depth Model and 5-Axis Variable-Angle Laser Engraving Experiment Based on the Energy Conservation Principle.

To ensure the consistency of laser engraving depth in chemical milling, the precise control of 5-axis variable-angle laser engraving was the focus of research. Based on the energy conservation principle, the depth model of 5-axis variable-angle laser engraving is established, and the relationships among the laser engraving depth, laser power, scanning velocity, and beam axis angle are proposed. A depth-constraint real-time adaptive control method of laser power is proposed considering the variable scanning velocity and beam axis angles. The depth model parameters are identified by an orthogonal experiment, and a variable-angle laser engraving experiment with adaptive control of laser power is carried out. The coefficient of determination of the proposed depth model is 0.977, which means that the engraving depth model established in this paper predicts the engraving depth effectively and reliably. The depth-constraint adaptive control method of laser power obtains stable and uniform machining results under abrupt changes in scanning velocity and beam axis angles.

Feasibility Analysis of Coupling Hydrogen-Derived Fuel on a Coal-Fired Boiler for Power Generation

As an alternative to hydrogen, hydrogen-derived fuel (NH3, CH3OH, or CH3OCH3) is considered to be an ideal secondary energy source. The effects of coupling hydrogen-derived fuels with coal on the thermodynamic parameters of a boiler are analyzed through thermal calculations according to the principles of mass and energy conservation. A 300 MW tangentially fired boiler is selected for a case study. The results show that the variations of boiler thermodynamic parameters depend on the properties of hydrogen-derived fuels and coupling mass percentage. After the coupling, the furnace exit flue gas temperature changes, which results in alterations in heat distribution of radiation and convection for the water-cooled walls and the convective heating surfaces. The furnace exit flue gas temperature drops for coupling H2 or NH3 but rises for coupling CH3OH or CH3OCH3 with the growth of the coupling mass percentage. The variations of boiler thermal efficiency with different coupling mass percentages under BMCR load are 0.55% to 0.90% for H2, −0.32% to −1.16% for NH3, −0.22% to −2.03% for CH3OH, and −0.08% to −0.59% for CH3OCH3. The acid dew point rises and then drops as the coupling mass percentage grows. The flow rate of the total flue gas increases at the outlet of the air preheater. Thus, the current forced draft fan could not meet the requirements, and its retrofit should be performed. After the large proportion of cofiring, the coal consumption rate drops. The annual emissions reductions of CO2 are up to 0.734 million tons for H2, 0.231 million tons for NH3, 0.062 million tons for CH3OH, and 0.101 million tons for CH3OCH3 under BMCR load at a 20% coupling mass percentage. The lifecycle CO2 reduction potential should be considered for better illustrating the benefits of cocombustion in future studies.

Metabolic responses of predators to prey density

The metabolic cost of foraging is the dark energy of ecological systems. It is much harder to observe and to measure than its beneficial counterpart, prey consumption, yet it is not inconsequential for the dynamics of prey and predator populations. Here I define the metabolic response as the change in energy expenditure of predators in response to changes in prey density. It is analogous and intrinsically linked to the functional response, which is the change in consumption rate with prey density, as they are both shaped by adjustments in foraging activity. These adjustments are adaptive, ubiquitous in nature, and are implicitly assumed by models of predator–prey dynamics that impose consumption saturation in functional responses. By ignoring the associated metabolic responses, these models violate the principle of energy conservation and likely underestimate the strength of predator–prey interactions. Using analytical and numerical approaches, I show that missing this component of interaction has broad consequences for dynamical stability and for the robustness of ecosystems to persistent environmental or anthropogenic stressors. Negative metabolic responses – those resulting from decreases in foraging activity when more prey is available, and arguably the most common – lead to lower local stability of food webs and a faster pace of change in population sizes, including higher excitability, higher frequency of oscillations, and quicker return times to equilibrium when stable. They can also buffer the effects of press perturbations, such as harvesting, on target populations and on their prey through top-down trophic cascades, but are expected to magnify bottom-up cascades, including the effects of nutrient enrichment or the effects of altering lower trophic levels that can be caused by environmental forcing and climate change. These results have implications for any resource management approach that relies on models of food web dynamics, which is the case of many applications of ecosystem-based fisheries management. Finally, besides having their own individual effects, metabolic responses have the potential to greatly alter, or even invert, functional response-stability relationships, and therefore can be critical to an integral understanding of predation and its influence on population dynamics and persistence.

Development of a multi-layer quality assurance program to evaluate the uncertainty of deformable dose accumulation in adaptive radiotherapy.

Deformable dose accumulation (DDA) has uncertainties which impede the implementation of DDA-based adaptive radiotherapy (ART) in clinic. The purpose of this study is to develop a multi-layer quality assurance (MLQA) program to evaluate uncertainties in DDA. A computer program is developed to generate a pseudo-inverse displacement vector field (DVF) for each deformable image registration (DIR) performed in Accuray's PreciseART. The pseudo-inverse DVF is first used to calculate a pseudo-inverse consistency error (PICE) and then implemented in an energy and mass congruent mapping (EMCM) method to reconstruct a deformed dose. The PICE is taken as a metric to estimate DIR uncertainties. A pseudo-inverse dose agreement rate (PIDAR) is used to evaluate the consequence of the DIR uncertainties in DDA and the principle of energy conservation is used to validate the integrity of dose mappings. The developed MLQA program was tested using the data collected from five representative cancer patients treated with tomotherapy. DIRs were performed in PreciseART to generate primary DVFs for the five patients. The fidelity index and PICE of these DVFs on average are equal to 0.028mm and 0.169mm, respectively. With the criteria of 3mm/3% and 5mm/5%, the PIDARs of the PreciseART-reconstructed doses are 73.9±4.4% and 87.2±3.3%, respectively. The PreciseART and EMCM-based dose reconstructions have their deposited energy changed by 5.6±3.9% and 2.6±1.5% in five GTVs, and by 9.2±7.8% and 4.7±3.6% in 30 OARs, respectively. A pseudo-inverse map-based EMCM program has been developed to evaluate DIR and dose mapping uncertainties. This program could also be used as a sanity check tool for DDA-based ART.

Data center energy conservation study utilizing loop heat pipes as a chip-level cooling technique and its industrial application

The thermal management and energy consumption for data centers became an increasing challenge due to a significant increase in their number, size and power density in modern information and digitization age. The electricity using by cooling system contributed the important fraction of energy consumption in datacenters, and it is of great significance to carry out the research of new cooling technologies to improve the cooling efficiency of datacenters. This paper initiatively presents the basic energy conservation principle of chip-level cooling technique based on the loop heat pipe (LHP) for natural cooling throughout a year. An energy-saving theoretical evaluation model based on the LHP chip-level cooling method is developed for assessing the energy utilizing efficiency and energy-saving levels in datacenters. Two kinds of real computer servers using two water-cooling LHPs with flat evaporator are introduced. The evaporator volume of a LHP is 54 × 44 × 12 mm3. The tests show that the servers work safely with the inlet water temperature of 40 °C and flow rate of 0.027 m3/h in the condenser of LHP. Lastly, the applications in two industrial data centers based on the LHP chip-level cooling technique are practiced. The annual cooling-PUE of a cloud-computing datacenter in Hohhot city is 1.053, and the annual PUE of a supercomputer-center in Beijing city is 1.15. Their operation data both show that the energy savings of the cooling system and the whole data center could be up to 81 % and 30 % respectively compared to the traditional CRAH cooling technique, which are in accordance with the predicted results of theoretical evaluation model.

A novel approach for 3D discrete element modelling the progressive delamination in unidirectional CFRP composites

This study proposed a novel approach based on the 3D discrete element method (DEM) to simulate the progressive delamination in unidirectional carbon fibre reinforced polymer (CFRP) composite laminates. A hexagonal packing strategy was used for modelling 0∘ representative plies, the interface between different plies was modelled with one bond and seven bonds following the conservation of energy principle and a power law. The number of representative layers and the stiffness of bonds within these layers were calibrated with a comparison of results obtained from finite element method and theoretical analysis. DEM simulations of delamination with both interface models were conducted on unidirectional composites for double cantilever beam (DCB), end-loaded split (ELS) and fixed-ratio mixed-mode (FRMM) tests. It was found that the seven-bond interface model has a better agreement with experimental data in all three tests than the one-bond interface model by adopting the proposed seven-bond arrangement in terms of the progressive delamination process. The main advantages of the present interface model are its simplicity, robustness and computational efficiency when elastic bonds are used in the DEM models.