Energy Minimization Method Research Articles

Effect of Thermal State on the Mantle Composition and Core Sizes of the Moon

Based on the joint inversion of seismic and gravity data in combination with phase equilibrium calculations within the Na2O–TiO2–CaO–FeO–MgO–Al2O3–SiO2 system using the method of Gibbs free energy minimization, we estimated the influence of the thermal state on the model chemical composition of the lunar mantle and the size of the Fe–S lunar core. Models based on the Apollo seismic data and mass and moment of inertia estimates from the data of the GRAIL mission were used as boundary conditions. The solution of the inverse problem provided constraints on the chemical composition (major oxide abundances) and mineralogy of the three-layer mantle. It was shown that, independent of temperature distribution, the FeO contents (~11–14 wt %) and MG# values (80–83) of the upper, middle, and lower mantle of the Moon are approximately equal and strongly different from those of the bulk silicate Earth (BSE): FeO ~ 8% and MG# ~ 89. In contrast, the estimates of Al2O3 content in the mantle are sensitive to temperature distribution. The analysis of thermal state models with temperature differences of 100–200°C at different depths showed that the Al2O3 content increases from 1–5 wt % in the upper and middle mantle to 4–7 wt % in the lower mantle containing up to 20 wt % garnet. The lunar abundance of Al2O3 is ~(1.0–1.2) × BSE for “cold” models and may be as high as (1.3–1.7) × BSE for “hot” models. The abundance of SiO2 is less sensitive to temperature distribution and is 50–55 wt % in the upper mantle and 45–50 wt % in the lower mantle. Orthopyroxene rather than olivine is the dominant mineral of the upper mantle. Based on the modeling of Fe–S melt density at high P and T, the size of the lunar core was estimated. The radius of the Fe–S core having a mean density of 7.1 g/cm3 and a sulfur content of 3.5–6.0 wt % lies within the range 50–350 km with the most probable value of approximately 300 km and depends weakly on the thermal regime of the Moon. The results of modeling imply that the lunar mantle is chemically stratified and the compositions of the Earth and its satellite are significantly different.

Prediction of product gas composition from biomass gasification by the method of Gibbs free energy minimization

ABSTRACT Product gas composition of biomass gasification was predicted using MS-Excel Solver tool with the method of minimization of Gibbs free energy, which studies only the effect of temperature on equilibrium reaction conditions. The input required for the simulation are operating temperature, elemental analysis of biomass sample and the thermodynamic coefficients of each gas components and elements. Simulation of literature data was performed at temperatures 600°C, 700°C, 800°C, and 900°C. A close match had been observed between the values from literature and the simulated values for incomplete and complete carbon on the basis of root mean square error calculated for each data point.

The Structural and Functional Diversity of Intrinsically Disordered Regions in Transmembrane Proteins.

The intrinsically disordered proteins and protein regions (IDPs/IDPRs) do not have unique structures, but are known to be functionally important and their conformational flexibility and structural plasticity have engendered a paradigmatic shift in the classical sequence-structure-function maxim. Fundamental understanding in this field has significantly evolved since the discovery of this class of proteins about 25years ago. Though the IDPRs of transmembrane proteins (TMP-IDPRs) comply with the broad definition of typical IDPs and IDPRs found in water-soluble globular proteins, much less is explored and known about them. In this review, we assimilate the key emerging biophysical principles from the limited studies on TMP-IDPRs and provide several context-specific biological examples to highlight the ubiquitous nature of TMP-IDPRs and their functional importance in cellular functions. Besides providing a spectrum of insights from sequence to structural disorder and functions, we also review the challenges and methodological advances in studying the structure-function relationship of TMP-IDPRs. We also lay stress upon the importance of an integrative framework, where ensemble-averaged (and mostly low-resolution) data from multiple experiments can be faithfully integrated with modelling techniques such as advanced sampling, coarse-graining, and free energy minimization methods for a high-fidelity characterization of TMP-IDPRs. We close the review by providing futuristic perspective with suggestions on how we could use the ideas and methods from the exciting field of protein engineering in conjunction with integrative modelling framework to advance the IDPR field and harness the sequence-disorder-function paradigm towards functional design of proteins.

Thermochemical analysis and experimental investigation of a recuperative waste heat recovery system for the tri-reforming of light oil

This paper presents a thermochemical and experimental investigation into the use of oxy-fuel exhaust gases for the tri-reforming of light oil. The thermochemical recuperation of light oil makes it possible for the furnace to burn hydrogen-rich syngas, and thereby significantly improve furnace efficiency. This study investigates three process parameters: the exhaust gas recirculation rate, the syngas temperature, and the exhaust gas temperature. (1) The more exhaust gas that is recirculated, the less oxygen is required for complete conversion into syngas, and the higher the heating value of the produced syngas. A maximum increase in the heating value of 31.6% (compared to the primary fuel) is possible if pure bi-reforming is performed. (2) The chemical equilibrium calculations showed that the syngas temperature has a strong effect on the composition of the syngas; a syngas temperature of 1265 °C is necessary to achieve a conversion rate of 99.9%. The thermodynamic analysis was performed using the Gibbs free energy minimization method. In order to prevent carbon formation, a slight oxygen excess of 1% must be present. In this case, a syngas temperature of 970 °C is sufficient for the stationary tri-reforming of light oil. (3) The energy required for reforming the primary fuel increases with increased syngas temperature, while the energy contained in the hot exhaust gas stream increases with increased exhaust gas temperature. In order to achieve a syngas temperature of at least 970 °C, both the required exhaust gas recirculation rate and the amount of oxygen for reforming and combustion are directly dependent on the temperature of the exhaust gas. An exhaust gas temperature of 1000 °C requires an exhaust gas recirculation rate of 16.2%, while a recirculation rate of 26.9% is necessary at an exhaust gas temperature of 1600 °C. In the latter case, it is possible to increase the efficiency of the oxy-fuel furnace by 22.8%.

Thermodynamic study of Ba3CuO4 (s) in Ba-Cu-O system

Ba3CuO4(s) is one of the important compounds as a proton conducting electrolyte which form due to interaction of BaO and CuO. In the present study, Ba3CuO4(s) has been synthesized by solid state route and the Gibbs energy of formation and heat capacity has been experimentally measured by Knudsen Effusion Mass Spectrometer and differential scanning calorimeter. The ΔGf (Ba3CuO4, s, T) and C°p (Ba3CuO4, s, T) is obtained as per given equations:ΔGf (Ba3CuO4, s, T) ± 7 / kJ mol−1 = −1888 + 0.4229.(T / K)C°p (Ba3CuO4, s, T)(J K−1 mol−1) ± 6 = 211 + 0.0274·(T/K) – 3039600.(T /K)−2The binary phase diagram of BaO-CuO system has been calculated based on the Gibbs energy minimization method. Using the experimental thermodynamic data, isothermal chemical potential diagram of Ba-Cu-C-O system with different axial parameter and ternary phase diagram of Ba (s) - Cu (s) - O2 (g) system has been calculated in order to study the thermodynamic stability and coexisting phases of Ba3CuO4(s).

Optimization of a laser ion source for 163Ho isotope separation.

To measure the mass of the electron neutrino, the "Electron Capture in Holmium-163" (ECHo) collaboration aims at calorimetrically measuring the spectrum following electron capture in 163Ho. The success of the ECHo experiment depends critically on the radiochemical purity of the 163Ho sample, which is ion-implanted into the calorimeters. For this, a 30 kV high transmission magnetic mass separator equipped with a resonance ionization laser ion source is used. To meet the ECHo requirements, the ion source unit was optimized with respect to its thermal characteristics and material composition by means of the finite element method thermal-electric calculations and chemical equilibrium simulation using the Gibbs energy minimization method. The new setup provides an improved selectivity of laser ionization vs interfering surface ionization of 2700(500) and an overall efficiency of 41(5)% for the ion-implantation process.

Anisotropic osmosis filtering for shadow removal in images

We present an anisotropic extension of the isotropic osmosis model that has been introduced by Weickert et al (2013 Energy Minimization Methods in Computer Vision and Pattern Recognition (Berlin: Springer)) for visual computing applications, and we adapt it specifically to shadow removal applications. We show that in the integrable setting, linear anisotropic osmosis minimises an energy that involves a suitable quadratic form which models local directional structures. In our shadow removal applications we estimate the local structure via a modified tensor voting approach (Moreno et al 2012 New Developments in the Visualization and Processing of Tensor Fields (Berlin: Springer)) and use this information within an anisotropic diffusion inpainting that resembles edge-enhancing anisotropic diffusion inpainting (Galić et al 2008 J. Math. Imaging Vis. 31 255–69; Weickert and Welk 2006 Visualization and Processing of Tensor Fields (Berlin: Springer)). Our numerical scheme combines the nonnegativity preserving stencil of Fehrenbach and Mirebeau (2014 J. Math. Imaging Vis. 49 123–47) with an exact time stepping based on highly accurate polynomial approximations of the matrix exponential. The resulting anisotropic model is tested on several synthetic and natural images corrupted by constant shadows. We show that it outperforms isotropic osmosis, since it does not suffer from blurring artefacts at the shadow boundaries.

Hamiltonian-based minimum-energy trajectory planning and tracking control for a motor-table system: part I minimum-energy methods in trajectory planning

In this paper, we propose the minimum energy control input based on Hamiltonian strategy for the motor-table system. The energy equation of the motor-table system contains of the input energy, dissipation energy, potential energy and output energy, and includes electrical and mechanical energies. The methods of the minimum control effort (MCE), minimum input energy control (MIEC), minimum dissipation energy control (MDEC) and trapezoidal trajectory energy control are compared for the motor-table system. From the numerical results, we can find that the MIEC and MDEC approaches can obtain the same minimum input energy. Traditionally, the MCE approach was regarded as the minimum energy control in the previous study. However, we have demonstrated that the MCE approach is not the minimum energy control in this paper.

Optimization of planar mechanisms by using a minimum distance function

The paper examines the application of a general minimum distance error function to the dimensional kinematic synthesis of bidimensional mechanisms. The minimum distance approach makes it possible to solve the problem maintaining the same generality as that of the minimum deformation energy method while solving the problems that occasionally appear in the former method involving low stiffness mechanisms. It is a general method that can deal both with unprescribed and prescribed timing problems, and is applicable for path generation problems, function generation, solid guidance, and any combination of the aforementioned requirements as introduced in the usual precision point scheme. The method exhibits good convergence and computational efficiency. The minimum distance error function is solved with a sequential quadratic programming (SQP) approach. In the study, the synthesis problem is also optimized by using SQP, and the function can be easily adapted to other methods such as genetic algorithms.In the study, the minimum distance approach is initially presented. Subsequently, an efficient SQP method is developed by using analytic derivatives for solving. The next point addresses the application of the concept for the synthesis of mechanisms by using an SQP approach with approximate derivatives. This delivers a situation where the optimization is performed on an error function that itself consists of an inner optimization function. A few examples are presented and are also compared with the minimum deformation energy method. Finally, a few conclusions and future studies are discussed.

Comparison of traditional and flash pyrolysis of different carbon content silicon oxycarbides

This study is to understand the effect of carbon content on the pyrolysis behaviors and phase contents of silicon oxycarbides (SiOCs). Flash pyrolysis conditions, evolution of different SiOC phases, and free carbon types/amounts are compared for C-rich and less C-rich precursors. The C-rich system experiences the flash event at a much lower pyrolysis temperature with a much higher current density even though the internal temperatures at flash are very similar. SiC formation is more obvious for the C-rich samples along with a much higher carbon content under both flash and traditional pyrolysis conditions. The phase contents of SiO2, SiC, and other SiOC intermediates can be calculated using a Gibbs energy minimization method, showing that the C-rich sample has more C-rich SiOC intermediates while the less C-rich sample has more Si-rich intermediates. This research provides a general framework in assessing the pyrolysis behaviors of different SiOC materials.

Carbon content and pyrolysis atmosphere effects on phase development in SiOC systems

In this study, bulk silicon oxycarbides (SiOCs) were fabricated from base polysiloxane (PSO) systems with different carbon content by using Ar or Ar + H2O pyrolysis atmosphere. Compared to the Ar pyrolysis condition, the SiOC samples pyrolyzed with water vapor plus Ar generally show lower ceramic yield except for the Tospearl (polymethylsilsesquioxane) sample at 1400 °C. The SiOC ceramics contain significantly less SiC and carbon after pyrolysis under Ar + H2O atmosphere compared to pure Ar atmosphere. The carbon-poor Tospearl sample shows a crystalline SiO2 structure (cristobalite) after pyrolysis at 1400 °C in Ar + H2O, which is also confirmed using TEM diffraction pattern analysis. TEM microstructures indicate little change in microstructures for the carbon-rich samples. The fundamentals, such as total Gibbs free energy, the driving force for crystallization, and phase contents at different pyrolysis temperatures can be calculated based on a Gibbs free energy minimization method. The phase content calculations predict considerable decrease in the amounts of SiC and C and significant increase in the percent of SiO2 after pyrolysis in Ar + H2O compared to Ar. The thermodynamic calculation results match with our experimental observations. This work provides a guided method to synthesize high temperature SiOCs with desired phases.

Deformation characteristics of sinusoidally-corrugated laminated composite panel – A higher-order finite element approach

In this article, the deformation characteristics of sinusoidally-corrugated laminated composite panels are examined under uniform and sinusoidally distributed transverse loads. The sinusoidal corrugation in laminate structure is achieved using the general curvature method. The displacement field is based on the third-order shear deformation mid-plane kinematics theory with nine degrees-of-freedom. The minimum total potential energy method is employed to obtain the governing equation. The solutions are obtained using two-dimensional finite element approximation via nine-noded isoparametric quadrilateral Lagrangian element. The convergence and comparison studies reveal the consistency and accuracy of present model. The new numerical illustrations reflect the significance of corrugation ratios, edge constraints, side-to-thickness ratios and aspect ratios on the deformation behavior of the corrugated and non-corrugated laminated composite panels.

Frequency-splitting dynamic MRI reconstruction using multi-scale 3D convolutional sparse coding and automatic parameter selection.

In this paper, we propose a novel image reconstruction algorithm using multi-scale 3D convolutional sparse coding and a spectral decomposition technique for highly undersampled dynamic Magnetic Resonance Imaging (MRI) data. The proposed method recovers high-frequency information using a shared 3D convolution-based dictionary built progressively during the reconstruction process in an unsupervised manner, while low-frequency information is recovered using a total variation-based energy minimization method that leverages temporal coherence in dynamic MRI. Additionally, the proposed 3D dictionary is built across three different scales to more efficiently adapt to various feature sizes, and elastic net regularization is employed to promote a better approximation to the sparse input data. We also propose an automatic parameter selection technique based on a genetic algorithm to find optimal parameters for our numerical solver which is a variant of the alternating direction method of multipliers (ADMM). We demonstrate the performance of our method by comparing it with state-of-the-art methods on 15 single-coil cardiac, 7 single-coil DCE, and a multi-coil brain MRI datasets at different sampling rates (12.5%, 25% and 50%). The results show that our method significantly outperforms the other state-of-the-art methods in reconstruction quality with a comparable running time and is resilient to noise.

Analytical results for the equilibrium configurations of a three-phase elastic material

This paper describes some analytical results for the equilibrium configurations of a three (one austenitic and two martensitic) phase elastic isotropic material. Constitutive relations in each of the material phase are provided explicitly. Direct methods in the calculus of variations are employed to compute the relaxed energy. An analytical expression of the relaxed energy envelope is derived for a particular case where both the martensitic and austenitic phase share the same value of the shear modulus and the chemical energy of the austenitic phase becomes negative. The computed relaxed energy afterward is used in the energy minimization method for finding the equilibrium-state solution of the three phase elastic material. Deformations when computed using exact relaxed constitutive relations exhibit mesh independence and this property is also illustrated in a specific case by computing the deformation of a single crystal in tension and compression by using Finite Element Method.

Experimental and modeling analysis of Air and CO2 biomass gasification in a reverse lab scale downdraft gasifier

Abstract This research work aims at investigating the effect of carbon dioxide feed in biomass gasification as a possible way to directly exploit the exhaust gas from the engine of combined heat and power systems to convert carbon dioxide to carbon monoxide via Boudouard reaction and consequently increase the carbon conversion and reduce char yield. The effects on biomass gasification using air, and air diluted with carbon dioxide were assessed in a reverse downdraft lab-scale gasifier utilizing 2 kg of pelletized biomass. This reactor is mounted on a digital weighing balance which enables the recording of mass loss during the gasification process. Furthermore, the mixture of air and CO2 is obtained from two mass flow controllers which enable constant and desired flux of gasifying agents across the gasifier. At the same time, an in-house developed thermodynamic equilibrium model was applied to predict the gas composition and char output. Unlike the classical equilibrium strategy that calculates the gasification products using the Gibbs energy minimization method at fixed temperature and pressure, the current approach is based on the enthalpy of the reactants, analogous to the adiabatic combustion temperature. Also, a correction factor accounting for the heat losses, was implemented. The model outcome shows a good agreement with the experimental results, especially in terms of predicted char yields and trends of the dominant producer gas species. The same strategy was used to describe the behavior of the gasification system and estimate the quality of producer gas and the cold gas efficiency of the system.

Unsupervised texture reconstruction method using bidirectional similarity function for 3-D measurements

The developments of three-dimensional (3-D) imaging and display technology have created important demands for 3-D model with realistic texture. Due to texture misalignment and inconsistent illumination, texture reconstruction is subject to degradation like blurring, ghosting and color discontinuity. A composite weight texture blending approach is proposed to mitigate the artifacts. For inaccurate geometric model, bidirectional similarity function based multi-scale energy minimization method is proposed to correct texture misalignment. The average processing time of the proposed method is only 40% of existing method. The optical experiments demonstrate that photorealistic texture could be achieved for inaccurate geometric model and inconsistent illumination.

Intermetallic WSi2–W5Si3 Alloy by Magnesiothermic SHS Reaction

Intermetallic tungsten silicide alloy WSi2–W5Si3 was successfully synthesized via magnesiothermic SHS reaction in the WO3–Si–Mg system. Equilibrium composition of combustion products was calculated by standard Gibbs energy minimization method and the combustion products were characterized by XRD, SEM, and EDX. The synthesized alloy had a density of 8.97 g/cm3 (96.4% of theoretical). The process can be readily recommended for practical implementation.

Cost Aggregation for Stereo Matching Using Total Generalized Variation With Fusion Tensor

Stereo matching methods have achieved remarkable improvements by exploiting various attempts. However, most stereo matching algorithms still suffer from problems such as ambiguous region and inherent ambiguities. In particular, some problems affecting cost aggregation step have the greatest impact on depth results. To resolve the above-mentioned problems, we propose a new cost aggregation method using the modified total generalized variation with fusion tensor. First, two kinds of diffusion tensors are extracted from the guidance color image and the guidance depth map. They are incorporated into an energy functional to obtain the total generalized variation. After formulating the final energy functional, it is optimized via a primal-dual energy minimization method. The performance of the proposed method is experimentally verified by qualitatively and quantitatively comparing the results to those of other algorithms.

Numerical simulation of EWOD on a printed circuit board for cleanroom-less digital fluidic manufacturing applications

PurposeDigital microfluidic devices have been demonstrated to have great potential for a wide range of applications. These devices need expensive photolithography process and clean room facilities, while printed circuit board (PCB) technology provides high configurability and at low cost. This study aims to investigate the mechanism of electrowetting-on-a-dielectric (EWOD) on PCB by solving the multiphysics interaction between fluid droplet and electric field. The performance of system will be improved by inducing an efficient electric field inside the droplet.Design/methodology/approachTo induce an electric field inside the droplet on a PCB and change the initial contact angle, the mechanism of EWOD is studied based on energy minimization method and a set of simulations are carried out by considering multiphysics interaction between the fluid droplet and external electric field. The performance of EWOD on a PCB system is investigated using different electrode structures.FindingsSurface tension plays an efficient role in smaller sizes and can be used to move and control a fluid droplet on a surface by changing the interfacial surface tension. EWOD on a PCB system is studied. and it revealed that any change in electric field affects the droplet contact angle and as a result droplet deformation and movement. The electrode pattern is an important parameter which could change the electric potential distribution inside the droplet. Array of electrodes with square, zigzag interdigitated and crescent shapes are studied to enhance the EWOD force on a PCB substrate. Based on the results, the radial shape of the crescent electrodes keeps almost the same actuated contact line, applies uniform force on the droplet periphery and prevents the droplet from large deformation. A droplet velocity of 0.6 mm/s is achieved by exciting the crescent electrodes at 315 V. Furthermore, the behavior of system is characterized for process parameters such as actuation voltage, dielectric constant of insulator layer, fluidic material properties and the resultant velocity and contact angle. The study of contact angle distribution and droplet motion revealed that it is helpful to generate EWOD mechanism on a PCB which does not need more complicated fabrication processes.Originality/valueThe ability to handle and manipulate the droplets is very important for chemistry on-chip analysis such as immunoassay chips. Furthermore, a PCB-based electrowetting-on-dielectric device is of high interest because it does not need cleanroom facilities and avoids additional high-cost fabrication processes. In the present research, the EWOD mechanism is studied on a PCB by using different electrode patterns.

Accurate prediction of secondary structure of tRNAs

RNA structure plays a key role in understanding its biological function. Currently, the most successful de novo methods for RNA secondary structure prediction are based on free energy minimization. Existing free energy minimization methods focus more on building energy calculation models and optimizing energy parameters while paying less effort on developing structure space search algorithm. This study proposes a de novo method, namely DPARSS, for RNA secondary structure prediction. DPARSS proposes a novel dynamic programming algorithm for structure space search and intends to generate predictions with minimal free energy. An evaluation on a benchmark dataset consisting of tRNAs indicates that the DPARSS method achieves better predictive performance than existing free energy minimization methods. Additionally, case studies suggest that the improvement achieved by the DPARSS algorithm is likely due to the fact that the predictions generated by DPARSS algorithm form more base pairs, contain less mismatches and form longer base pair segments.