Change In Internal Energy Research Articles

Vehicle Body and Roll Cage Assessment involving Frontal, Side and Roll-over Crash Analysis by FEA using LS-Dyna

Simulating the vehicle collision has gained importance in the automotive sector due to its accuracy, cost effectiveness and enhanced reliability. It aids in improving the safety of driver and passenger and also examine the cause of crash or collision. This numerical analysis investigates the materials capability to enhance safety. A three-dimensional vehicle model was developed along with its roll cage using solid work tool. Hypermesh work bench was employed to discretise the sensitive parts of the body and roll cage using beam 189 element having six degree of freedom at each node. The existing structural steel members were replaced with reinforced carbon fibre in all the sensitive part of the body and roll cage and its structural stability was assessed using the frontal, side and roll over crash simulation using LS Dyna. This investigation also reveals the change in internal energy, kinetic energy absorption and momentum transfer for both structural steel and carbon fiber under all the crash scenarios. The outcomes of this numerical investigation proved that the reinforced carbon fiber can be effectively replaced with the structural steel to enhance safety.

The thermodynamics of light absorption for a two-level system

The thermodynamics of light absorption is analysed using, as model system, a two-level molecular system characterised by mirror symmetry between its absorption and emission spectra. This means that the structure of the HOMO-1 and HOMO (highest occupied molecular orbital) ground state and the LUMO, LUMO + 1 (lowest unoccupied molecular orbital) excited states are nearly identical in their vibronic structures. This is a good model for many dyes and, in particular, for chlorophyll molecules, the main chromophore presents in the photosynthetic apparatus of plants. When a photon is absorbed by this two-level system, a transition from the HOMO ground state to the LUMO excited state occurs. Then, the system rapidly relaxes to an equilibrium distribution over the excited state sublevels and this equilibrium distribution is defined by the temperature of the bath that contains the molecule. In the described scenario, taking into account the changes in internal energy and the partition function before and after the photon absorption event, it is demonstrated that no entropy change occurs upon electronic transition from the ground state to the excited state, upon photon absorption. Furthermore, the idea that the photon-induced electronic transition can be described in terms of system heating is considered. We conclude that photon energy cannot be considered as heat. Instead, when thermal excitation is taken into account, the increased system temperature leads inexorably to entropy changes.

Polarization-independent highly-efficient splitter based on the cross-shaped ridge structure

A polarization-independent highly-efficient transmission beam splitter based on the cross-shaped ridge structure is proposed in this paper. Based on the rigorous coupled-wave analysis (RCWA) and the simulated annealing (SA) algorithm, the efficiencies of 32.33% of 0th order and 32.42% of ±1st order for transverse electric (TE) polarization and 32.53% of 0th order and 32.60% of ±1st order for transverse magnetic (TM) polarization can be achieved. In addition, the simplified modal method (SMM) is applied to analysis the internal energy changes process in detail. What is more, different from the reported references only considering the case of one layer, we also used the SMM to analyze the three-port cross-array beam splitter under normal incidence with the approximation treatment. The results show that the method of which has certain reference value, which can be the guidance of the design of the gratings with similar structures in the future.

State functions/quantities in thermodynamics and heat transfer

In thermodynamics, it is essential to distinguish between state functions and process functions. The reason is that the simple compressible thermodynamic system is a bivariate-process system, and the change of internal energy, a state function, corresponds to two process functions, heat and work. Among the state functions in thermodynamics, entropy is a special one because it has to be defined through a process function, exchanged heat δQ, and a unique factor of integration, 1/T. In heat transfer, it is shown that Fourier's law and the differential equation of heat conduction are both relations of state quantities alone, and process quantities appear when an integration with respect to time is applied. Moreover, an incompressible heat conduction medium element without conversion between heat and work is a univariate-process system governed by a single variable, temperature. In this case, the change of the thermal energy (“heat content”) stored in the system, a state quantity as a function of T alone, corresponds to only one process quantity, the transferred heat. Therefore, on the one hand, it is unnecessary to strictly distinguish between state quantities and process quantities in heat transfer, and on the other hand, there is no need to use a factor of integration to prove entransy a state quantity in heat transfer. Thermodynamics and heat transfer are two parallel sub-disciplines in thermal science. It is incorrect to deny entransy as a state quantity in heat transfer by the uniqueness of the factor of integration for entropy in thermodynamics, and entransy has significant physical meaning in the analysis and optimization of heat transfer processes.

Calibration of the Advanced Spectral Leakage scheme for neutron star merger simulations, and extension to smoothed-particle hydrodynamics

ABSTRACT We calibrate a neutrino transport approximation, called Advanced Spectral Leakage (ASL), with the purpose of modelling neutrino-driven winds in neutron star mergers. Based on a number of snapshots, we gauge the ASL parameters by comparing against both the two-moment (M1) scheme implemented in the flash code and the Monte Carlo neutrino code sedonu. The ASL scheme contains three parameters, the least robust of which results to be a blocking parameter for electron neutrinos and antineutrinos. The parameter steering the angular distribution of neutrino heating is recalibrated compared to the earlier work. We also present a new, fast and mesh-free algorithm for calculating spectral optical depths, which, when using smoothed-particle hydrodynamics (SPH), makes the neutrino transport completely particle-based. We estimate a speed-up of a factor of ≳100 in the optical depth calculation when comparing to a grid-based approach. In the suggested calibration we recover luminosities and mean energies within $25{{\ \rm per\ cent}}$. A comparison of the rates of change of internal energy and electron fraction in the neutrino-driven wind suggests comparable accuracies of ASL and M1, but a higher computational efficiency of the ASL scheme. We estimate that the ratio between the CPU hours spent on the ASL neutrino scheme and those spent on the hydrodynamics is ≲0.8 per time-step when considering the SPH code magma2 as source code for the Lagrangian hydrodynamics, to be compared with a factor of 10 from the M1 in flash.

Influence of Moringa Leaves Extract on Hb Response to Radiation Dose Rates’ Changes: I. Permittivity and Its Thermodynamic Driven State Functions

The harm caused by ionizing radiation is well known and is performed by depositing energy from the radiation source into the irradiated material. Biosystems fight back to maintain their integrity and functions. Doing so requires external help where important supplements are provided to enable the biosystem to challenge destruction done by irradiation in the form of ionization and free radicals. This work investigates the effect of Moringa oleifera leaves extract, MOLE, on two different gamma radiation dose rates’ damages on the biosystem. This is done by estimating physical parameters that belong to dielectric factors, static permittivity, or based upon them as thermodynamic state functions; changes in Helmholtz free energy, internal energy, and entropy of the sample under assessment. Good sensitivity to factors causing changes in the studied system's net dipole moment is noticed, especially within the 1st week. The help of MOLE, a natural supplement, to the biosystem repairing the damage caused by irradiation was tested. Data indicated that MOLE has a powerful influence that could help the biosystem, based on its vast nutrients, trace elements, and antioxidants to fight radiation damage.

Can CP Be Less Than CV ?

Can CP be less than CV? This is a fundamental question in physics, chemistry, chemical engineering, and mechanical engineering. This question hangs in the minds of many students, instructors, and researchers. The first instinct is to answer “Yes, for water between 0 and 4 °C” if one knows that water expands as temperature decreases in this temperature range. The same question is asked in several Physical Chemistry and Physics textbooks. Students are supposed to answer that water contracts when heated at below 4 °C in an isobaric process. Because work is done to the contracting water, less heat is required to increase the water temperature in an isobaric process than in an isochoric process. Therefore, CP is less than CV. However, this answer is fundamentally flawed because it assumes, implicitly and incorrectly, that the internal energy change of water depends solely on its temperature change. Neglecting the variation of the internal energy with volume (internal pressure) will invalidate the Clausius inequality and violate the second law of thermodynamics. Once the internal pressure is properly taken into account, it becomes clear that CP cannot be less than CV for any substance at any temperature regardless of the sign of the thermal expansion coefficient of the substance.

Simulating Finite-Time Isothermal Processes with Superconducting Quantum Circuits.

Finite-time isothermal processes are ubiquitous in quantum-heat-engine cycles, yet complicated due to the coexistence of the changing Hamiltonian and the interaction with the thermal bath. Such complexity prevents classical thermodynamic measurements of a performed work. In this paper, the isothermal process is decomposed into piecewise adiabatic and isochoric processes to measure the performed work as the internal energy change in adiabatic processes. The piecewise control scheme allows the direct simulation of the whole process on a universal quantum computer, which provides a new experimental platform to study quantum thermodynamics. We implement the simulation on ibmqx2 to show the scaling of the extra work in finite-time isothermal processes.

Thermodynamics of CO2 adsorption on cellulose‐derived biochar prepared in ionic liquid

AbstractThis work focused on thermodynamic analysis of carbon dioxide (CO2) adsorption on a promising biochar as a CO2 adsorbent. The biochar was prepared by catalytic pyrolysis of cellulose material in ionic liquid at moderate temperature. The adsorption characteristics, such as adsorption capacity, interfacial potential, Gibbs free energy change, enthalpy change, entropy change, and internal energy change, influenced by adsorption temperature and gas pressure, were systematically investigated. The results indicated that CO2 adsorption on cellulose‐derived biochar was a spontaneous, physical, exothermic, and entropic decrement process, accompanied by adsorption capacity of 5.2 mmol/g and interfacial potential of −18.2 J/g at 273 K and 100 kPa. The process could be well described by adsorption potential theory. Then a quasi‐Gaussian distribution of site energy was verified for CO2 adsorption. The interfacial potential was found to be a monotropic function of the amount of CO2 adsorbed, and the latter was actually a differential of the former via adsorption potential. The positive temperature effect and negative pressure effect on negative Gibbs free energy change indicated that reducing adsorption temperature and increasing gas pressure were beneficial to CO2 uptake, accompanied by the increase of adsorption capacity and the reduction of interfacial energy, entropy, enthalpy, and internal energy. The strongest temperature effects on entropy change, enthalpy change, and internal energy change existed at given pressure or temperature. The pressure effect was stronger and more sensitive to pressure at lower adsorption pressure. More interestingly, the peak pressure or peak temperature with the strongest pressure effect possibly existed during CO2 adsorption.

Thermal behavior of crystalline and amorphous HDPE phase in the process of necking at creep deformation

Thermodynamic aspect plays an important role in the structural processes in the neck of partially crystalline polymers under tension. Method of deformation calorimetry, simultaneously recording thermal and mechanical effects allows quantitative determination of entropic and energy effects during deformation. Evaluation of such parameters in combination with structural analysis provides important information for the analysis of the deformation mechanism of various polymer systems. It was revealed that the change in internal energy is due to the contributions of several processes: the destruction of the initial lamellar structure, the formation of a “neck” (lamellae-fibrillae transition), and the formation and deformation of fibrilae. The stretching of partially crystalline polymers in an amorphous state promotes crystallization. The chains in the formed crystallites are oriented along the axis of action of the applied force. The growth of crystallites is accompanied by straightening of the folded sections of the chains, which causes stress relaxation or rapid elongation of the sample when tested for creep.

Bimodal Polymer End-Linked Nanoparticle Network Design Strategy to Manipulate the Structure-Mechanics Relation.

A kind of bimodal polymer end-linked network employing nanoparticles (NPs) as net points has been designed and constructed through coarse-grained molecular dynamics simulation. We systematically explore the effects of the molecular weight (length of the long polymer chains), chain flexibility, and temperature on the accurate distribution of the spherical NPs and the resulting mechanical properties of the bimodal network. It is found that the NPs can be dispersed well, and a larger average distance between the NPs is realized with the increase of the length of the long polymer chains, the rigidity of short and long chains, and the temperature. There is a linear relationship between the average interparticle distance of NPs and the arithmetical average of the root-mean-square end-to-end distance of long and short chains. By adopting the uniaxial deformation, the stress-strain behavior and the bond orientation are examined. The results illustrate that introducing the short chains into the uniform long chains network can notably improve the tensile stress-strain performance. The bond orientation behaviors present that short chains are more prone to be oriented and stretched, contributing to more stress during the stretching process. Furthermore, enhanced stress-strain behaviors can be observed by manipulating the chain stiffness and temperature. Interestingly, the bimodal end-linked network reveals a distinctively enhanced stress-strain behavior versus the temperature, which is opposite to that of traditional physically mixed polymer nanocomposites (PNCs), attributed to a higher entropic elasticity and the uniform dispersion of NPs of the end-linked system at high temperatures. The network exhibits a linear relationship for the stress at a fixed strain versus the temperature. Notably, it is indicated that the contribution of entropy accounts for most of the total stress, while the change of internal energy only accounts for a small part, which is consistent with the experimental observation of the classic rubber elastic theory. In general, our study demonstrates a rational route to precisely control the spatial dispersion of the NPs and effectively tailor the mechanical properties of PNCs.

A fully general, non-perturbative treatment of impulsive heating

ABSTRACT Impulsive encounters between astrophysical objects are usually treated using the distant tide approximation (DTA) for which the impact parameter, b, is assumed to be significantly larger than the characteristic radii of the subject, rS, and the perturber, rP. The perturber potential is then expanded as a multipole series and truncated at the quadrupole term. When the perturber is more extended than the subject, this standard approach can be extended to the case where rS ≪ b < rP. However, for encounters with b of order rS or smaller, the DTA typically overpredicts the impulse, Δv, and hence the internal energy change of the subject, ΔEint. This is unfortunate, as these close encounters are the most interesting, potentially leading to tidal capture, mass stripping, or tidal disruption. Another drawback of the DTA is that ΔEint is proportional to the moment of inertia, which diverges unless the subject is truncated or has a density profile that falls off faster than r−5. To overcome these shortcomings, this paper presents a fully general, non-perturbative treatment of impulsive encounters which is valid for any impact parameter, and not hampered by divergence issues, thereby negating the necessity to truncate the subject. We present analytical expressions for Δv for a variety of perturber profiles, apply our formalism to both straight-path encounters and eccentric orbits, and discuss the mass-loss due to tidal shocks in gravitational encounters between equal-mass galaxies.

Refinement and extension of COSMO-RS-trained fragment contribution models for predicting the partition properties of C10-20 chlorinated paraffin congeners.

COSMO-RS-trained fragment contribution models (FCMs) to predict the partition properties of chlorinated paraffin (CP) congeners were refined and extended. The improvement includes (i) the use of an improved conformer generation method for COSMO-RS, (ii) extension of training and validation sets for FCMs up to C20 congeners covering short-chain (SCCPs), medium-chain (MCCPs) and long-chain CPs (LCCPs), and (iii) more realistic simulation of industrial CP mixture compositions by using a stochastic algorithm. Extension of the training set markedly improved the accuracy of model predictions for MCCPs and LCCPs, as compared to the previous study. The predicted values of the log octanol/water partition coefficients (Kow) for CP mixtures agreed well with experimentally determined values from the literature. Using the established FCMs, this study provided a set of quantum chemically based predictions for 193 congener groups (C10-20 and Cl0-21) regarding Kow, air/water (Kaw), and octanol/air (Koa) partition coefficients, subcooled liquid vapor pressure (VP) and aqueous solubility (Sw) in a temperature range of 5-45 °C as well as the respective enthalpy and internal energy changes.

Optimal Proportion of Similar Materials and Rockburst Tendency of White Sandstone

To explore the tendency of rockburst, a similar material ratio was optimised based on white sandstone. Quartz sand, iron powder, gypsum, cement, retarder, and a water‐reducing agent were used as the main materials. The orthogonal test design principle was used to determine the four‐factor and four‐level orthogonal test design with the quartz sand content, iron powder content, gypsum‐cement ratio, and sand particle size as the influencing factors. Uniaxial compression tests and tensile tests were conducted on similar material models. The tensile strength and elastic modulus were analysed, the significance of each influencing factor was investigated, and the test results of the similar materials were fitted. The optimal ratios of the similar materials of white sandstone were found to be quartz sand content of 36%, iron powder content of 1.9%, gypsum‐cement ratio of 1.8 : 1, and sand particle size of 2–4 mm. The physical and mechanical properties of the similar materials were consistent with those of white sandstone. The mechanical properties of the similar materials were compared with those of the original rock. By judging the rockburst propensity and verifying the index, it is concluded that the similar materials can effectively simulate the characteristics of white sandstone, which is an ideal similar material of rockburst, and they all show strong rockburst propensity. The rock specimens with optimal proportions were produced, and the internal energy changes and rockburst mechanisms of the model at different temperatures were discussed. The results show that the rockburst process is closely related to energy, such as thermal energy and elastic strain energy, and the rock failure process can be divided into three main stages: energy accumulation, microcrack formation and propagation, and crack penetration and bursting. It provides an experimental basis for the preparation of rockburst similar materials that are more in line with the actual situation of the project and provides a basis for discussing the energy criterion of rockburst.

Analysis on the Difference of Impact Response between Single Coal‐Rock Particle and the Box Structure‐Based Tail Beam

In the process of coal caving, the basis of identifying coal and rock by the vibration signal is the difference of the tail beam response when coal‐rock impacts the tail beam, and the tail beam in the hydraulic support is a complex box structure with multiplate transverse and longitudinal welding, and the response difference of the box structure‐based tail beam under the impact of coal‐rock is not clear. Therefore, this paper studies the response difference of box structure‐based tail beam when coal‐rock particle impacts on the box structure‐based tail beam. Firstly, through the construction and analysis of the impact theoretical model of the coal‐rock particle and metal plate, it is found that the complex box structure of the tail beam makes it extremely difficult to establish the impact theoretical model of the coal‐rock and box structure‐based tail beam, so it is impossible to directly study the response of the box structure‐based tail beam when the coal‐rock impacts on the box structure‐based tail beam by the theoretical method. Therefore, the impact simulation model of coal‐rock particle and box structure‐based tail beam is further established. Through the changes of kinetic energy and internal energy of the box structure‐based tail beam system, the contact response of collision contact zone, and noncollision contact zone of the box structure‐based tail beam, the response difference of box structure‐based tail beam when coal‐rock particle impacts on the box structure‐based tail beam is analyzed. Then, by changing the impact speed and contact mode of the coal‐rock particle, the effects of impact speed and the contact mode on the response difference of the box structure‐based tail beam are studied separately. The conclusion shows that the response difference of the box structure‐based tail beam under the impact of the coal particle and rock particle is obvious, and the difference increases as the impact speed increases, and the difference increases as the contact range increases.

Internal energy change in Darcy-Forchheimer Carreau fluid model past a vertical stretching sheet with magnetic dipole and variable thermo-physical properties

In this research work, we consider a thermal energy system with a different controlling effects which impact the entire system. These controlling effects include the variable thermo-physical properties of Carreau fluid flow causing change in internal energy (viscous dissipation) of the permeable thermal conversion problem. The disturbance in fluid’s motion is created by applying magnetic dipole. After converting the thermal system from partial differential into ordinary differential, the developed system is solved by using midpoint method in combination with bisection. The thermal energy extrusion system consists of velocity and temperature fields. The related controlling parameters include variable thermal conductivity parameter, Darcy-Forchheimer parameter, Eckert number, mixed convection parameter, variable viscosity parameter, ferrohydrodynamic interaction variable, Weissenberg number, curie temperature and Prandtl number. The sketched results provides good thermal effects on entire system for small and large values of these parameters. Carreau fluid model is performed to analyse the properties of shear thinning and thickening. It is noticed that velocity distribution reduces for large values of Williamson parameter, ferrohydrodynamic interaction variable, porosity parameter and variable viscosity parameter but opposite behavior is achieved for large values of Darcy-Forchheimer parameter. The temperature profile shows great impact by emerging parameters appearing on it. The small parameter and Eckert number shows enhancement in temperature distribution, but large reduction is noticed in temperature distribution for greater values of Prandtl number and curie parameter. Comparison of current thermal system is calculated for limited values of these parameters.

Deformation infrared calorimetry for materials characterization applied to study cyclic superelasticity in NiTi wires

In this article, we introduce the Deformation Infrared Calorimetry (DIRC) technique for resolving spatial distributions of heat and work in samples subjected to uniaxial loading under isothermal conditions. Heat and work distributions are computed from synchronized temperature and strain fields obtained by infrared thermography (IRT) and digital image correlation (DIC). The DIRC data acquisition and processing are described in the first part of the article. Then, we show the relevance and usage of DIRC by employing it to characterize the cyclic evolution of the thermomechanical response of a superelastic NiTi wire termed functional fatigue. Particularly, we evaluated the evolution of the heat, work, and internal energy changes upon the repeated propagation of stress-induced martensitic transformations (SIMTs) shear-bands, producing a highly heterogeneous deformation scenario. Further postprocessing of DIRC allowed us to associate the functional fatigue of the material with the evolution of the production/recovery of martensite and the energy storage and dissipation during the propagation of SIMT shear-bands.

Thermoelastic characterization of carbon nanotube reinforced PDMS elastomer

Abstract Internal energy and entropy contribution to the elasticity of carbon nanotube reinforced polydimethylsiloxane (PDMS) is evaluated using statistical theory of rubber elasticity. Stress–temperature measurements were performed and the data was used to calculate the internal energy contribution to elastic stress. Interesting aspects such as increase in energy and low entropy contribution to the elasticity of carbon nanotube reinforced PDMS is observed. This can be related t o the deformation behavior of the network chains of pristine elastomers and the directional reorientation of nanotube entanglements. While the entropy change is associated with reorientation or directional preference of the carbon nanotube entanglements, the internal energy change is associated with structural bending or stretching of the nanotubes. A reversible deformation of nanotube entanglements complements rubber like elasticity and the present study gives insights into the thermoelasticity of reinforced elastomers as well as the elastic behavior of carbon nanotube entanglements inside a polymer matrix.

Analysis of the mechanism dissipation of mechanical energy flow in adiabatic throttling incompressible liquid

The differences arising in the analysis of the throttling process in different reference systems are considered. It is shown that it is convenient to analyze the change in internal energy when throttling a certain volume of gas in a system of counting that is rigidly connected to its center of mass. In this system, gas expansion works, resulting in energy being diverted to the environment. At the same time, energy is transferred from the environment to the gas by the movement of the throttle device. The sign of the increment of the internal energy of the considered volume of ideal gas in the non-equilibrium process adiabatic throttling is determined by the ratio between the two named energy exchange processes. From the first law of thermodynamics, an expression is obtained for the value of the increment of specific internal energy when throttling an ideal gas.

Change in internal energy of viscoelastic fluid flow between two rotating parallel plates having variable fluid properties

In this study, second-grade fluid is taken into account in order to examine its rotating behavior with heat and mass transfer effects. The analysis is carried out between two parallel plates. The study of heat and mass transfer is accomplished by taking the effects of non-constant diffusivity, conductivity and viscosity. A chemical reaction is taken in the form of activation energy. Moreover, it is assume that the kinetic energy of the fluid particles is converted into internal energy. Signifying fundamental equations are tracked by constructing numerical form solutions for velocity, temperature and concentration distributions, while assuming variable fluid properties and internal energy change. Bvp4c technique is employed by considering second-grade fluid parameter and variable fluid properties to be very small. The impact of emerging parameters on velocity, temperature and concentration distributions is examined through graphical depiction. A direct relation is taken between concentration and diffusivity, temperature and thermal conductivity, whereas the indirect relation is assumed for viscosity. Heat transfer is minor for a fluid with variable conductivity and viscosity as likened to the fluid with constant conductivity and viscosity. For uplifting values of rotation parameter, the fluid velocity magnifies.