Energy Criterion Research Articles

Investigation of the thermal regime of a linear DC motor

Linear DC motors (LDPT) with a limited armature stroke are used in mechanisms that reciprocate the working body or stabilize its position in tracking systems. The use of LDPT instead of rotary motion motors with a converter in the form of a crank mechanism, a screw pair or other similar mechanical systems leads to a significant simplification of the kinematic scheme, increased efficiency and, as a rule, increased accuracy of the complex and its reliability. There are a number of problems in the creation of LDPT, which are not fully reflected in the scientific and technical literature. In particular, with parametric optimization of the engine according to weight, size and energy criteria, one of the main limiters is overheating of the winding, and in magnetoelectric machines, also overheating of permanent magnets, which are very sensitive to the magnitude of the operating temperature and thermal shocks. The article presents an analytical method for calculating the thermal state of an engine in steady state, based on the method of thermal substitution schemes. The technique is designed for use in a parametric optimization program. To clarify the values of the a priori coefficients in the analytical expressions of the proposed algorithm, the authors modeled the LDPT using the numerical finite element method. Based on the simulation results, a picture of the temperature field of the machine was obtained and the critical heating areas were determined. Verification of the theoretical provisions was carried out during experimental studies of the prototype engine. The tests showed good convergence of the calculated and experimental parameters.

Prompt Analysis and Design for Passively Mode-Locked Solid-State Lasers with Semiconductor Saturable Absorbers

The critical pump power for achieving passively continuous-wave mode-locking in a solid-state laser is analytically derived from the spatially dependent rate equations and the criterion for the intracavity pulse energy. A prompt way is proposed to straightforwardly design the cavity for passively mode-locked solid-state lasers. Complete experiments are performed to demonstrate the proposed cavity design and, simultaneously, to verify the theoretical model for the critical pump powers. It is interestingly observed that even though a larger modulation depth causes a higher critical pump power, it can generate a shorter pulse width in return.

Theoretical study of the adsorption capacity of potentially toxic Cd2+, Pb2+, and Hg2+ ions in hemicellulose matrices

Hemicellulose is widely available in nature, is a sustainable resource and has a wide range of applications. Among them, adsorption stands out for the removal of potentially toxic ions. Thus, in the study, the adsorption of Cd2+, Pb2+ and Hg2+ ions in two hemicellulose matrices were elucidated through computational simulations using density functional theory. Molecular electrostatic potential and frontier molecular orbitals demonstrated whether the interactions could happen. Four interaction complexes were highlighted due to the interaction energy criteria, ΔEBind, ΔH and ΔG < 0.00 kcal mol−1, that is: Hm1… Pb (1); Hm2… Pb (3); Hm2…Cd (4) and Hm2…Hg (4) and the results show that they occur through physisorption. In structural parameter studies, interaction distances smaller than 3000 Å were identified, which ranged from 2.253 Å to 2.972 Å. From the analysis of the topological parameters of QTAIM, it was possible to characterize the intensities of the interactions, as well as their nature, which were partially covalent or electrostatic in nature. Finally, based on the theoretical results, it can be affirmed that the hemicellulose can interact with Cd2+, Pb2+ and Hg2+ ions, evidencing that this study can support further experimental essays to remove contaminants from effluents.

Multi-scale spallation model for single-crystal ductile metals incorporating microscopic mechanism of void nucleation

Spall strength characterizes the tensile performance of materials under high strain rates. However, theoretical prediction of the spall strength has long been a big challenge since it involves information on the damage evolution at multiple length scales. In this work, a multi-scale model is proposed for the spallation of single-crystal ductile metals, which includes both a microscopic model of damage nucleation and an effective correlation between the microscopic physical mechanisms and the macroscopic mechanical behaviors. An energy criterion to predict the threshold stress for damage nucleation is firstly proposed based on a near-realistic three-dimensional configuration of dislocation emission. The statistical characteristics of the damage nucleation threshold are analyzed, based on which a multi-scale spall model is proposed to couple the physical essence at the micro-scale to the macro-scale, revealing the influences of temperature, vacancy concentration, and strain rate on spall strength. An approximate form of the multi-scale model is proposed by dimensional analysis and reasonable approximation, which is consistent with the empirical model summarized from experimental results, and further deduced to a simple scaling law that predicts the transition in the strain rate-sensitivity of spall strength.

Host-guest complexes of a cryptand based on 5H-cyclopenta[2,1-b:3,4b′]pyridine moieties: prediction of ion selectivity by quantum chemical calculations XVI

Selective alkaline and earth alkaline metal ion encapsulation by six different Lehn-type cryptands was predicted by DFT (B3LYP/LANL2DZp) computational chemistry. All cryptands contain three identical moieties connected by the aliphatic nitrogen atom, constructing a very structurally flexible system for accommodating different-sized metal cations. Inspiration for selected hosts was taken from already well-known Lehn-type Cryptand [phen.phen.phen] where one phenanthroline was substituted by 5H-cyclopenta[2,1-b:3,4b′]pyridine in which the CH2– group was replaced by a series of heteroatoms forming the selected series of investigated hosts. The ion selectivity and the ability of the hosts to adjust their structure to accommodate the metal cations successfully were based on energy and geometric criteria. Medium-size cations have been proven to be best fitted for the selected host series.

The effects of rectangular baffle angles and heights on heat transfer and pressure drop performance in cross-triangular grooved rectangular flow ducts

The improvements in heat exchangers mainly focus on rising energy efficiency. The cross-grooved rectangular flow ducts are largely used for plate heat exchangers. In this study, to enhance the heat transfer and hydraulic-thermal performance in the cross-grooved rectangular ducts with triangular grooves, rectangular baffles were located in the duct, and the influences of the rectangular baffle angles and heights on the features of the heat transfer and pressure drop were numerically analyzed in detail. The equations of Navier-Stokes and energy were solved by employing the Ansys-Fluent program with the k-ε turbulence model as steady and three-dimensional. Air used as working fluid has an inlet temperature of 293 K while the triangular groove’s wall temperature is 373 K. Rectangular baffles have various angles of 30°, 60°, and 90°, and heights of 0.25H, 0.5H, and 0.75H. The mean Nusselt number (Num), dimensionless temperature (T*), turbulence kinetic energy (TKE*), pressure (p*), and performance evaluation criterion (PEC) number of the ducts with rectangular baffles were evaluated by comparing with the cross-triangular grooved duct without baffle. Also, the contours of turbulence kinetic energy, temperature, and velocity vector were exhibited for the cross-triangular grooved rectangular ducts with different arrangements of baffle angles and heights. Results were matched with experimental and computational outcomes of the study found in the literature, and it was observed that they were fairly compatible. The increment rate of Num at 90° baffle angle and 0.75H height is 197.56 % higher for Re = 6000 compared to 0.25H. Besides, for Re = 1000, the PEC number is 84.50 % higher at 0.25H baffle height and 30° angle than at 90°.

Study on the fault slip rule and the rockburst mechanism induced by mining the panel through fault

When mining near the fault can cause the fault to slip and release energy, resulting in rockburst and posing a significant safety risk to coal mine production. This paper proposes a numerical simulation method, based on FLAC3D numerical simulation, for calculating the dynamic response of fault slip below the impact of mining. The release patterns of energy from fault slip are compared between mining via the fault from the hanging wall and mining via the fault from the footwall. The dynamic response characteristics of coal and rock mass under the disturbance of fault slip induced dynamic loading are revealed. This research suggests that the fault slip seismic moment (M0) of the panel mined via the fault from footwall is substantially higher than from hanging wall. Moreover, the disturbance of the footwall panel mining via the fault leads to a more severe disturbance of the surrounding rock mass, resulting in a higher risk of rockburst. Plastic failure of the rock surrounded in the mining area under the strong dynamic loading of fault slip leads to a significant reduction in peak abutment stress, releasing tremendous energy. When the disturbance caused by fault slip dynamic load is relatively small, the maximum abutment stress increases, and the dynamic load increases the energy storage of surrounding rock. Based on energy theory, an energy criterion for the occurrence of fault slip type rockburst has been proposed. The results suggest that strong fault slip dynamic load has an obvious inducing effect on rockburst, and the stronger the dynamic load and greater static load of the rock, the more the manifestation of rockburst.

Synthesis, antimicrobial activity and Molecular docking study of some novel isoxazole incorporated benzimidazole derivatives

A series of novel isoxazole-incorporated benzimidazole derivatives was synthesized and investigated for antimicrobial activity. The structures of all synthesized compounds were confirmed by means of elemental analysis, infrared spectroscopy (IR), proton nuclear magnetic resonance (1H-NMR), and liquid chromatography-mass spectrometry (LC-MS). All compounds were evaluated for antimicrobial activity cup plate method against Staphylococcus aureus, Bacillus anthracis, Pseudomonas aeruginosa, Escherchia coli, Candida albicans and Aspegillus niger. The 4d, 4f and 4j compounds showed significant activity against gram-positive and gram-negative bacteria. On the basis of the interaction energy criterion, compound 4f showed the best docking interactions equal to 7.0 kcal/mol.

Mechanical activation assisted of biobased encapsulated rejuvenators to promote asphalt self-healing

This research aimed to evaluate the effect of the addition of biobased encapsulated rejuvenators on the self-healing properties of asphalt mixtures. With this objective, polynuclear capsules were synthesised using alginate biopolymer as encapsulating material and sunflower oil as rejuvenator. The capsules were physically and mechanically characterised by optic and scanning electron microscopy techniques as well compressive tests. Four types of semi-dense asphalt mixtures were manufactured, varying in capsule content: 0.0%, 0.125%, 0.25%, and 0.5%wt. The self-healing properties of each mixture were evaluated based on mechanical cracking, capsule activation, and healing level quantification processes. A new confined uniaxial compression test was developed for capsule activation. The self-healing capacity of the asphalt mixtures was determined under force and fracture energy criteria. Statistically significant differences in the healing variables were analysed through one-way ANOVA and Tukey post-hoc tests. The main results showed that the capsules presented regular spherical morphology and high mechanical stability to resist the mixing process at high temperature. The new activation approach effectively activated the alginate-based capsules inside the asphalt mixtures promoting their self-healing. Force and energy crack-healing criteria improved with the addition of capsules in the asphalt matrix, with healing values being higher for the force criterion than those for the energy one. Finally, the addition of capsules in a content equal or greater than 0.25%wt. significantly improved the self-healing properties of the asphalt mixtures.

A two-stage parallel hybrid method for power system dynamic security assessment

Abstract The present paper introduces a hybrid method based on both the Lyapunov’s direct approach using the Potential Energy Boundary Surface method and parallel time-domain simulation for fast power system dynamic security assessment. The main contribution in the presented method is an approach that combines the directional derivative of the potential energy function and the maximum potential energy criterion in order to reduce the conservativeness in the estimation of the stability region at the direct method stage. For detailed investigation of the critical contingencies, a parallel approach is applied at the time-domain simulation stage. From the simulation results, the proposed method achieves a high level of accuracy in classifying network contingencies and shows great computational performance potential in light of the requirement for fast dynamic security assessment.

Influence of nearby fiber on fiber–matrix debonding: Coupled Criterion prediction and debonding shape determination

Fiber–matrix interface debonding in two-fiber specimens under remote tensile loading is studied both experimentally and numerically by means of a coupled stress and energy criterion. Depending on its relative position, the neighboring fiber induces a perturbation of both stress and energy fields at the reference fiber interface which results in asymmetrical debonding initiation and propagation. The determination of the debonding initiation and propagation shape is addressed based on either (i) stress isocontours, (ii) energy isocontours or (iii) the Coupled Criterion (CC). It was found that the debonding initiation configuration can be determined based on stress (respectively energy) isocontours for small (respectively large) enough interface brittleness number. For intermediate brittleness number, the debonding initiation configuration cannot be obtained using neither the stress nor the energy isocontours, but requires a coupling of both aspects. Despite different initiation debonding configurations, the corresponding initiation remote stresses do not differ much, which results in similar debonding configurations after unstable crack propagation following initiation.

Discretely-supported transfer nanoimprint anti-reflection nanostructures on complex uneven surface of Fresnel lenses

Nanopatterning complex uneven surface of numerous functional devices to improve their performance is significantly appealing; however, it is extremely challenging. This study proposes a discretely-supported transfer nanoimprint technique to fabricate nanostructures on complex device surfaces containing multi-spatial frequencies. First, a discretely-supported nanoimprint template was designed based on the built energy criterion. A contact fidelity of over 99% was achieved between the designed template and the targeted complex uneven substrate surface. Next, the prefilled nanostructures on the template were transferred to the target surface after contact. By precisely controlling the amount of micro-droplet jetting on the template on-demand, the accumulation of the polymer in the micro-valley sites on the complex substrate was avoided, thus maintaining the morphology and generating function of the devices. Finally, high-quality Fresnel lenses with broadband wide-directional antireflection and excellent imaging performance were developed by imprinting subwavelength-tapered nanostructures on the relief surface.

Thermodynamic model-based specification of optimal geothermal power generation system for high-temperature liquid-dominated systems using flash and flash-binary cycles

The utilization of high-temperature geothermal fluid for power generation requires the most suitable generation system to maximize the output with the highest efficiency. Single-flash, double-flash, and flash-binary cycles are the most representative systems for a reservoir with high-temperature geofluids. This study aims to develop a thermodynamic model-based method for selecting the optimal power generation system using criteria of power output and energy and exergy efficiencies. For this purpose, a thermodynamic model of the power generation system was constructed to calculate these values for high-temperature geofluids at 230–350 °C under steady-state conditions. The critical thermodynamic parameters that control these criteria include the separator pressure for the single and double flashers, working fluid, turbine inlet pressure, brine outlet temperature, and pinch point temperature, all of which are incorporated into the calculation. The results show that the flash-binary cycle generates the highest power; 21% higher than that of a single-flash cycle at the 5 °C pinch point, and 7% higher than a double-flash cycle. In addition to this merit, a cautious temperature of 120 °C is recommended for the cold reinjection fluid of a flash-binary cycle, which is considerably lower than that for the single- and double-flash cycles (164 °C).

Energy evolution mechanism during rockburst development in structures of surrounding rocks of deep rockburst-prone roadways in coal mines

Influenced by the deep high-stress environment, geological structures, and mining disturbance in coal mines, the frequency of rockburst disasters in roadways is increasing. This research analyzed energy evolution characteristics during rockburst development in the elastic bearing zone and energy conversion in the plastic failure zone. The critical energy criteria for structural instability of roadway surrounding rocks were deduced. Numerical software was also applied to simulate the energy evolution during rockburst development in surrounding rocks of rockburst-prone roadways under conditions of different mining depths and coal pillar widths. The occurrence mechanism of rockburst deep in coal mines was analyzed from the perspective of energy in structures of deep roadway surrounding rock in coal mines. The research results show that the critical energy criteria are closely related to the elastic strain energy stored in deep roadway surrounding rocks and the energy absorbed by support systems. The impact energy in roadways is directly proportional to the square of the stress concentration factor k. Moreover, as the mining depth increases, the location of the peak point of maximum energy density gradually shifts to coal ahead of the working face. The larger the mining depth is, the more significantly the energy density is influenced by advanced abutment pressure of the working face and the wider the affected area is. With the increment of the coal pillar width, the distance from the peak point of energy density to the roadway boundary enlarges abruptly at first and then slowly, and the critical coal pillar width for gentle change in the distance is 30 m. Changes in the peak elastic energy density in coal pillars with the coal pillar width can be divided into four stages: the slow increase stage, abrupt increase stage, abrupt decrease stage, and slow decrease stage. The elastic energy density is distributed asymmetrically in deep roadway surrounding rocks in coal mines. Under the action of structures of roadway surrounding rocks, energy evolution in these structures differs greatly during rockburst development under conditions of different coal pillar widths. This research provides an important theoretical basis for the support of rockburst-prone roadways during deep coal mining.

Effects of cutting speed and feed per knife on energy requirements for processing black spruce logs with a chipper-canter

The effects of cutting speed (CS), feed per knife (FK), and temperature condition on energy requirements for processing black spruce logs by a chipper-canter were assessed. Nine groups of 15 logs were tested at three CS (20, 25, and 30 m/s) and three FK (19, 25, and 32 mm). Each log was processed under frozen (−13 °C) and unfrozen (19 °C) conditions. Mean power increased as CS and FK increased. This behavior is explained by the mechanical relationships between the parameters and the rotation and feed speeds, as well as by the increase in the volume of wood cut. The energy consumption and the specific energy consumption increased as CS increased and FK decreased. For the three electrical criteria, more energy was consumed when processing frozen logs, which is due to the greater mechanical properties of wood. A positive relationship was identified between sapwood and heartwood moisture content, basic density, grain angle, and wood volume transformed into chips, as covariates, and the three energy criteria. These results give useful information on energy requirements to adjust cutting parameters of chipper-canters for a better energy management in sawmills.

Electrochemical cycling durability of platinum overlayers formed by self-terminating electrodeposition

Platinum thin films comprising nominally 1 to 20 atomic overlayers were formed on a gold-coated substrate using the self-terminating electrodeposition (STED) method. The platinum overlayer loading and morphology were characterized using X-ray Photoelectron Spectroscopy (XPS), Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES), Field Emission Scanning Electron Microscopy (FESEM), Cyclic Voltammetry (CV) and Chronoamperometry (CA). The durability of these platinum overlayer samples was estimated by subjecting the samples to ex-situ electrochemical potential cycling. The extent of platinum overlayer growth is lower than expected till four STED cycles and then increases non-linearly, leading to increased roughness. The shifts of platinum redox peaks in CVs and Pt4f signals in XPS spectra indicate surface-alloying of gold and platinum. After the durability test, the morphological evolution of platinum overlayers conforms with the extent of platinum dissolution estimated from CVs. Our results reveal that more than four STED cycles are needed to form platinum overlayers that meet the US Department of Energy (DOE) criteria for durability.

Developing structural sandwich panels for energy-efficient wall applications using laminated oil palm wood and rubberwood-based plywood/oriented strand board

In this work, a new type of structural sandwich panels made with laminated oil palm wood core and rubberwood-based oriented strand board (OSB)/plywood faces were introduced for energy-efficient wall applications in Thailand. Effect of the manufacturing process and material parameters including adhesive content (250 g/m2 and 500 g/m2), core configuration (cross or parallel laminated oil palm lumber) and density (low and medium) and face material type (rubberwood-based OSB/plywood) on panel’s properties were explored. The panels were produced using two-component polyurethane adhesive and a constant clamping pressure of 0.6 MPa. Adhesive content of 250 g/m2 was found to be sufficient for gluing all layers, with wood failure percentage of more than 80% as required by the standard. In-plane dimensional stability of the panels was mainly affected by the core configuration; it was better for cross laminated oil palm wood core sandwich panel. Higher core density resulted in increased density, thermal conductivity and compressive strength in the major direction but lower thermal resistance of the panel. The plywood face sandwich panels provided slightly higher compressive strength than OSB face sandwich panel, and their failure mechanisms were also different. The heat loss of these panels was about one-third of concrete and brick walls, hence, they can provide better insulation for indoor space. Based on the measured thermal conductivity, it was expected that these panels would pass the energy criteria according to Building Energy Code of Thailand. Thus, from the energy saving and sustainability perspectives, these panels can potentially be used as energy efficient wall panels for buildings, not only for Thailand but also for other tropical countries, where the oil palm wood and rubberwood resource is available.

Study on the Stress Evolution and Strengthening Support Timing of the Retracement Channel under the Super-Thick Nappe

The superposition effect of the advanced support pressure of the working face in the final mining stage and the lateral support stress of the roadway is a key factor affecting the stability of the retracement channel. To study the stress evolution of the retracement channel under the super-thick nappe and the timing of strengthening support, this paper takes the mining of the 360808 working face in Xinji No. 1 Mine as the engineering background, analyzes the occurrence conditions of the working face and the measured rock pressure law, and constructs a roof structure model of the retreat area. The UDEC discrete element numerical simulation software was used to analyze the evolution characteristics of concentrated stress and the failure law of surrounding rock around the retracement channel under gradual excavation conditions. Based on the relationship between the position of the main roof fracture and the stability of the surrounding rock of the retracement channel, the instability mechanism of the surrounding rock of the retracement channel was revealed. A mechanical model of the surrounding rock of the retracement channel under the condition of a gradient coal pillar was established, and the energy criterion K for the instability of the surrounding rock was obtained. The method of adding anchor cables to strengthen the support of the surrounding rock of the retracement channel was proposed. The results indicate that the accumulation of energy in the surrounding rock of the retracement channel is greater than the internal consumption of energy, which is the direct reason for the instability of the surrounding rock of the retracement channel. The time to strengthen the support of the roof is when the working face is 15 m away from the retracement channel. According to the analysis of on-site monitoring results, the roof convergence and the two-sides convergence before and after strengthening the support were reduced by 90 mm and 140 mm, respectively. Under the strengthening of support, the slope of the retracement channel in the 360808 working face is slight, without roof fall, and the surrounding rock of the channel is effectively controlled, which is of great significance for ensuring the safe application of the retracement channel. It has reference value for the safety production of surrounding mines and is conducive to promoting the sustainable development of local resource-based society and economy.

Surface functionalization of graphene-like boron arsenide monolayer: a first-principles study

In this work, the effects of hydrogen (H) and oxygen (O) adsorption on the electronic and magnetic properties of graphene-like boron arsenide (BAs) monolayer are investigated using first-principles calculations. Pristine monolayer is a non-magnetic two-dimensional (2D) material, exhibiting direct gap semiconductor character with band gap of 0.75 (1.18) eV as calculated by generalized gradient approximation with Perdew–Burke–Ernzerhof (HSE06) functional. Four high-symmetry adsorption sites are considered, including on-top of B atom (), on-top of As atom (), on-top of hollow site (), and on-top of bridge site (). Using the criterion of adsorption energy, it is found that and sites are favorable adsorption sites for H and O adatom, respectively. The analysis of electronic interactions indicate the charge transfer from host BAs monolayer to both adatoms. H adsorption conducts to the emergence of magnetic semiconductor nature in BAs monolayer with a total magnetic moment of 1.00 . Herein, the magnetism is originated mainly from H adatom and its neighbor As atoms. In contrast, the non-magnetic nature of BAs monolayer is preserved upon absorbing O atoms. In this case, the energy gap exhibits a slight reduction of 4%. Further, the effects of adatom coverage are also analyzed. The presented results suggest an effective modification of ground state electronic properties, as well as induction of new feature-rich properties to make new multifunctional 2D materials from non-magnetic BAs monolayer.

Accelerating inverse inference of ensemble Kalman filter via reduced-order model trained using adaptive sparse observations

The implementation of data assimilation often struggles with low computational efficiency due to the complexity of high-fidelity numerical modeling and the large size of the observation vectors. To address this challenge, it is necessary to employ reduced-order strategies for both the full-order dynamical model and observation operator. Proper orthogonal decomposition (POD) based reduced-order model (ROM) and discrete empirical interpolation method (DEIM) based sparse observation identification are often considered as primary solutions. However, their effective combination requires the determination of high-quality POD reduced-order basis vectors. The current research focuses on incorporating the ROM and DEIM into a Kalman filter framework, resulting in a reduced-order Kalman filter with sparse observations. The key aspect is identifying the optimal POD basis, which can be achieved iteratively by introducing a relative root-mean-square-error (RMSE) for a near-optimal exploration of both the desired low-order POD basis and observation locations. The singular value decomposition (SVD) of the snapshots is performed in a low-dimensional subspace, leading to significant computational savings. This improved POD basis not only enhances the reconstruction of the ROM, but also helps build the DEIM observation matrix, resulting in simultaneous dimensionality reduction of the state and observation space. The effectiveness of this algorithm is demonstrated through the retrieval of initial conditions for one-dimensional tsunami wave equations with real data scenarios. Experiments are conducted for both smooth and nonsmoothed initial conditions. The results show that when the observation data is available at 3 and 6 spatial observation locations, our method only requires fewer vectors with the first 45 and 90 dominant modes derived using the RMSE, compared to as many as 210 and 252 derived from the relative energy criterion. Our method enables a low-modal ROM to effectively reconstruct the wave height field, leading to considerable prediction capability for potential long-wave dynamics with comparable accuracy. The CPU time savings achieved through our method is at least one to two orders of magnitude compared to the CPU time required by the full-order model.