Energy Loss Coefficient Research Articles

Investigation of optoelectronic & thermoelectric features of ZnCrX2 (X = S Se Te) chalcopyrite semiconductor using mBJ potential

In the present investigation, we have examined the structural, optoelectronic and thermoelectric properties of the compound ZnCrX2 (X = S, Se, Te) using the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA-PBEsol) and the modified Becke–Johnson (mBJ) implemented on Wien2k code. By calculating the electronic structure, we observed that the indirect band gap was 1.76 eV, 1.68 eV, and 1.59 eV, for these selected compounds and the type of chemical bonding was ionic between Zn-X and Cr-X. For the three ternary chalcopyrites their optical properties including optical conductivity, complex dielectric functions, complex refractive index, reflectivity, energy loss, and absorption coefficient were examined. The calculated optical conductivity indicates that the studied compounds are suitable for optoelectronic applications as they have good absorbance and less energy loss in the low energy range of the electromagnetic spectrum. For ZnCrTe2, the maximum reflectivity was in the low energy range (0.48 or 48% at 9 eV). The BoltzTrap code was executed for the calculation of the thermoelectric properties and thermal efficiency of the compounds investigated, depending upon the Seebeck coefficient, thermal conductivity and electrical conductivity. The high value of the figure of merit and the Seebeck coefficient (260 uV/k) defines the high efficiency of the materials studied. Hence, the studied chalcopyrite compounds offer applications in solar cell devices and p-type semiconducting nature predictive in transport investigations.

Wall shear rate and energy loss coefficient measures using conventional Doppler ultrasound do not predict carotid plaque progression.

Background: The rate of carotid plaque progression is believed to be related to blood flow hemodynamics and shear stress. Our objective was to determine if wall shear rate (WSR) and the energy loss coefficient (ELC) measured by Doppler ultrasound could predict atherosclerotic carotid disease progression. Patients and methods: Patients at a large tertiary center with an initial ultrasound between 2016 and 2018 with a significant carotid plaque were included if they had at least one 6 months follow-up comparative study. Stenosis progression was assessed according to the NASCET (The North American Symptomatic Carotid Endarterectomy Trial) percentage criterion. Results: The average annual progression rate for the 74 plaques included was 5.7% NASCET per year. We identified 18 plaques with ≥10% NASCET progression and 56 plaques without significant progression <10% NASCET. Among the plaques with progression, only four plaques had progression greater than 20% NASCET. Median WSR was 6266 s-1 [5813-8974] in plaques with progression and 6564 s-1 [5285-8766] in stable plaques (p=0.643). Median ELC was 3.86 m2 [2.78-5.53] in plaque with progression and 4.32 m2 [3.42-6.81] in stable plaques (p=0.296). Conclusions: Although it is a widely accepted hypothesis that shear stress and hemodynamics of the carotid bifurcation contribute to plaque progression, we found that WSR and ELC estimated by Doppler ultrasound do not reliably predict atherosclerotic plaque progression in the carotid artery. Other ultrasound modalities, such as 3D imaging, may be used to assess the influence of plaque geometry and hemodynamics in plaque progression.

Wave Action Analysis of Multiple Bottom Fixed Semi-Circular Breakwaters in the Presence of a Floating Dock

Abstract The comprehensive usage of an array of natural or artificial semi-circular breakwaters (SCBs) as supporting structures to secure the floating/fixed structures are received increasingly more consideration in recent years. The performance characteristics of bottom-fixed SCB in the presence of a floating dock are investigated under the framework of linear wave theory. The edge conditions such as continuity of velocity and pressure along the SCB and zero-flow condition near rigid surfaces are adopted. The multi-domain boundary element method (MBEM) is used to examine the wave attenuation performance of the whole breakwater system in two dimensions. The correctness of the present study's numerical results is confirmed by performing the comparative study with the readily available experimental and analytical results reported by various researchers. The reflection, transmission, energy loss coefficients, and fluid force experienced by floating dock are examined as a function of incident wave properties and breakwater physical properties. The Bragg resonant reflection and performance comparison with other shapes are also studied. The study results strongly suggest that the damage of floating structures and leeward locales due to incident wave stroke is minimized with the introduction of porosity for SCB located on the seabed by dissipating the wave energy. A pair of bottom-fixed SCBs having 10–20% breakwater porosity placed far away from the dock is identified as the optimal choice to reduce the fluid force experienced by the dock and wave transmission coefficient.

Investigation of energy dissipation of an H-type vertical axis wind turbine based on entropy production theory

In vertical axis wind turbine (VAWT) research, amount studies have been conducted about the flow field around the blades, but the effect of blade tip vortex was not revealed clearly. The present study emphasized on the effect of blade tip vortex on energy loss in wake region and employed entropy production theory to determine where and how energy loss generates quantitatively. The numerical simulation was conducted for the VAWTs versus various tip speed ratio (TSR) conditions, and the numerical results were analyzed by entropy production method. The energy loss calculated by entropy production theory in VAWTs flows increases with TSR increasing. The distribution of entropy production rate (EPR) in wake region was asymmetrical due to the influence of blade tip vortex diffusion downstream and two fluctuation peaks appeared on EPR curves. The energy loss coefficient was defined to represent the energy deficit and kinetic energy recovery in wake region quantitatively. Generally, the energy loss coefficient was reduced to 0.1 between 8D to 9D in wake region and was equal to 0.1051 at x = 8D under optimal condition TSR = 2.19. The present study can guide configuration optimization of VAWTs to improve wind energy utilization and revenue of wind farms.

DDES study on a pressure-side cutback cooling turbine blade with a whisker lip and a whisker trailing edge

In this study, the whisker structure of a harbor seal is applied to the lip and the trailing edge of a turbine cooling blade with a pressure-side cutback. Four cases are studied in this article, including a prototype, a whisker trailing edge, a PP (The lip’s peak and the trailing edge’s peak are designed at the same blade height) case, and a PV (The lip’s peak and the trailing edge’s valley are designed at the same blade height) case. The DDES method is used to simulate the flow and thermal mixing process in the cascade. The coolant mass flow ratios () of 0.5% and 1% at an outlet Mach number of 0.9 are simulated. The PP case can achieve the best aerodynamic performance, which reduces the thermodynamic energy loss coefficient of the prototype by 0.98% and 0.99% at = 0.5% and = 1%, respectively. The PP case and the PV case increase the lowest spanwise average adiabatic film cooling effectiveness on the cutback surface from 0.5 to 0.7 at = 0.5%. The film cooling effectiveness of the PP case and the PV case can remain close to 1 over the entire cutback surface at = 1%. The PP case transforms the trailing edge shedding vortices on the pressure side into hairpin vortices. The whisker lip suppresses the lip vortex and alters the closed separation bubble on the cutback surface, causing the coolant to converge toward Section 1. The convergence of coolant is more helpful for the PP case to control the pressure side shedding vortex, resulting in a lower thermodynamic energy loss.

Strong, Compressible, and Ultrafast Self‐Recovery Organogel with In Situ Electrical Conductivity Improvement

AbstractCoordination complexes are widely used to tune the mechanical behaviors of polymer materials, including tensile strength, stretchability, self‐healing, and toughness. However, integrating multivalent functions into one material system via solely coordination complexes is challenging, even using combinations of metal ions and polymer ligands. Herein, a single‐step process is described using silver‐based coordination complexes as cross‐linkers to enable high compressibility (&gt;85%). The resultant organogel displays a high compressive strength (&gt;1 MPa) with a low energy loss coefficient (&lt;0.1 at 50% strain). Remarkably, it demonstrates an instant self‐recovery at room temperature with a speed &gt;1200 mm s−1, potentially being utilized for designing high‐frequency‐responsive soft materials (&gt;100 Hz). Importantly, in situ silver nanoparticles are formed, effectively endowing the organogel with high conductivity (550 S cm−1). Given the synthetic simplification to achieve multi‐valued properties in a single material system using metal‐based coordination complexes, such organogels hold significant potential for wearable electronics, tissue‐device interfaces, and soft robot applications.

Experimental Study of Impact of In-Service Deterioration on Aerodynamic Performance of High-Pressure Nozzle Guide Vanes

AbstractIn this paper we experimentally evaluate the impact of in-service deterioration on the aerodynamic performance of heavily film-cooled high-pressure nozzle guide vanes from large civil jet engines. We study 15 mid-life to end-of-life parts removed from operational engines, and compare their performance to those of new parts. Deterioration features included: increased surface roughness; thermal barrier coating spallation; damaged film cooling holes; and trailing edge burn-back. We characterize and present statistics for the surface roughness. Aerodynamic measurements were performed in the high technology readiness level Engine Component AeroThermal (ECAT) facility at the University of Oxford, at engine-representative conditions of exit Mach number, exit Reynolds number, coolant-to-mainstream pressure ratio, and turbulence intensity. We present detailed experimental measurements of the coolant capacity characteristics, downstream loss, and downstream flow structures. The results show that service time has the following effects on high-pressure nozzle guide vanes: increased equivalent sandgrain roughness of (up by 1056% change); reduced coolant flow capacity (maximum change of −6.27% for film cooling holes and −24.7% for the trailing edge slot); increased overall mixed-out kinetic energy loss coefficient by (up to 33% change); leads to greater downstream flow angle variation (change of −6 deg). This is one of the first significant studies of its type in the open literature, and is an important step towards whole-life engine performance assessment.

Total mechanical energy budget in open-channel transitions with turbulent flows

Abstract The issue of mechanical energy budget has received a lot of attention in open-channel flows which are frequently turbulent. Turbulent motions play a major role in the total mechanical energy of the flow field. It is difficult to evaluate total mechanical energy balance and energy loss for 3-D turbulent flows in irregular open channels due to the formation of vortices and the presence of secondary currents. In 3-D turbulent flows, the effect of these phenomena has often been considered as the empirical coefficient of energy loss. In this study, these details in the total mechanical energy budget are investigated through theoretical analysis and numerical simulation, a new form of the total mechanical energy equation and a relationship for the energy loss in 3-D turbulent flows are derived, and their applications are examined in open-channel transitions. For this purpose, the Navier-Stokes equations are solved numerically, and the results are used to obtain the various terms in the total mechanical energy balance equation and analyze the details. The relationships derived in this study generally support the concept of the total mechanical energy budget to comprehend the turbulence parameters affecting the mechanical energy balance in various open-channel flows.

A novel hybrid prediction model for PM2.5 concentration based on decomposition ensemble and error correction.

PM2.5 concentration is an important index to measure the degree of air pollution. It is necessary to establish an accurate PM2.5 concentration prediction system for urban air monitoring and control. Due to the nonlinear characteristics of PM2.5 concentration, it is difficult to predict it directly. Therefore, a novel hybrid model for PM2.5 concentration based on improved variational mode decomposition (IVMD), outlier-robust extreme learning machine (ORELM) optimized by hybrid cuckoo search (CS), and chimp optimization algorithm (ChOA), error correction (EC) is proposed named IVMD-ChOACS-ORELM-EC. First of all, an improved VMD based on energy loss coefficient, named IVMD, is proposed. IVMD decomposes the original data to obtain K IMF components. Then, a hybrid optimization algorithm based on ChOA improved by CS is proposed, named ChOACS. The hybrid optimization algorithm is used to optimize ORELM. On this basis, the prediction model ChOACS-ORELM is proposed, and the K IMF components are predicted by ChOACS-ORELM. Finally, the EC model based on decomposition ensemble is established to further improve the prediction accuracy. The PM2.5 concentration data collected at hourly intervals in Beijing, Shanghai, Shenyang, and Qingdao in China are used as experimental data. The experimental results show that the correlation coefficients between the prediction results and the actual values of the four cities are 0.9999, and the prediction performance of the proposed model is better than that of all comparison models.

A convenient and efficient path to bead foam parts: Restricted cell growth and simultaneous inter-bead welding

Wide density range and flexible geometry design make bead foam parts capture a large share of the polymeric foams market. However, traditional steam-chest molding process used to prepare bead foams involves complex molding facilities and high energy consumption. Herein, a novel in-mold foaming and molding (IMFM) method using supercritical CO2 as blowing agent was developed for the preparation of bead foam parts. TPU pellets were loaded in a special mold and TPU bead foam parts were fabricated in-mold after pressure quench. The molded parts with a density of 0.2 g/cm3 presented an elongation at break of 217 % and a ball rebound of 58 %. The energy loss coefficients of the bead foams remained lower than 12 % during the 100-time cyclic compression process. Restricted cell growth and simultaneous inter-bead welding in limited space were the key elements for this novel method. This method opens a new route to the production of bead foams with high performance in a convenient and efficient process.

Solvothermal imidization to polyimide composite aerogels by vacuum drying

Facile techniques that are time- and cost-saving nowadays are required for preparing PI aerogels with low density, structural stability, high mechanical performance, and thermal stability in wide practical applications. In this work, a strategy of solvothermal imidization followed by vacuum drying, using electrospun short polyimide (PI) fiber as supporting skeleton, was reported to prepare high-performance PI aerogels without the implementations of special drying instruments. The mechanism of “self-gluing” of the fiber-constructed skeleton of PI during preparation process was applied to enhance the strength of the precursor gels and achieve structural stability. PI aerogels with hierarchically cellular structure possessed bimodal interconnected pores, tunable densities (From 39.1 mg cm−3 to 55.8 mg cm−3), and high porosity (>96%) are reported. The aerogels showed low energy-loss coefficients for 103 cyclic compressive tests and initial degradation temperature high than 400 and 500 °C in air and nitrogen atmosphere, respectively.

Experimental studies of noise and vibration during milling of cast iron parts

Machining processes of cast iron parts are accompanied by significant noise and vibration. Exceeding the standard values of vibration and noise adversely affects the health of the operator and reduces the quality of the final product. The article deals with the scientific problem associated with the study of the causes of increased vibrations and noise during the milling of cast iron products. It has been experimentally shown that the existing ones create increased sound pressure in the range from 250 to 8000 Hz, while the sound pressure level reaches 80-92 dBa, which is 15-20 dBa higher than the maximum allowable. In the higher frequency part of the spectrum, the decrease in the intensity of sound radiation is from 4 to 7 dB per octave. The data obtained are the initial information for the calculation of noise reduction systems, based on compliance with sanitary standards. To simplify engineering calculations, vibrational energy loss coefficients for cast iron solid and hollow products are given.

Research on Leak Location Method of Water Supply Pipeline Based on MVMD

At present, the leakage rate of the water distribution network in China is still high, and the waste of water resources caused by water distribution network leakage is quite serious every year. Therefore, the location of pipeline leakage is of great significance for saving water resources and reducing economic losses. Acoustic emission technology is the most widely used pipeline leak location technology. The traditional non-stationary random signal de-noising method mainly relies on the estimation of noise parameters, ignoring periodic noise and components unrelated to pipeline leakage. Aiming at the above problems, this paper proposes a leak location method for water supply pipelines based on a multivariate variational mode decomposition algorithm. This method combines the two parameters of the energy loss coefficient and the correlation coefficient between adjacent modes, and adaptively determines the decomposition mode number K according to the characteristics of the signal itself. According to the correlation coefficient, the effective component is selected to reconstruct the signal and the cross-correlation time delay is estimated to determine the location of the pipeline leakage point. The experimental results show that this method has higher accuracy than the cross-correlation method based on VMD and the cross-correlation method based on EMD, and the average relative positioning error is less than 2.2%.

Studying the Effect of the Tangential Nonuniformity of Flow Parameters on Gas Dynamic Performances of the Nozzle Cascades of Turbine Machines

Aerodynamic efficiency of the nozzle cascades of steam and gas turbines is defined by many factors and one of them is the tangential and radial nonuniformity degree of the parameters of a spatial flow behind the cascades. The averaging of these parameters enables the determination of the integral parameters of the cascades, in particular two flow angles and the velocity angle or the kinetic energy loss coefficient. The angle that takes into account the level of the averaged radial component of the velocity defines the level of kinematic losses in the cascade. Even in the case of the cylindric boundaries of the cascade this angle differs from zero and kinematic losses decrease the cascade efficiency by 30 to 50 percent. This scientific paper gives the results of experimental investigations of the effect of the circumferential nonuniformity of the velocity and the angles of the spatial flow on kinematic losses at different radii of the nozzle cascade of the last stage of the steam turbine and the nozzle cascade of the first stage of the gas turbine. The kinetic energy loss coefficient and the coefficient of total losses were suggested as the integral characteristics of the cascades. In the case of cylindric boundaries of the stage the total loss-to-kinetic energy loss ratio is noticeably decreased during the transition from the average zone to the zone of end losses. However, in the peripheral zone of the nozzle cascade of the last stage of steam turbine total losses are three times higher than kinetic energy losses due to the fact that the radial component of the velocity behind the cascade is much higher than the flow rate component and the level of the losses of kinetic energy is not high.

Computational Fluid Dynamics Analysis of Blood Flow Changes during the Growth of Saccular Abdominal Aortic Aneurysm.

Computational fluid dynamics analysis of the growth process of saccular abdominal aortic aneurysm was performed. A 3D model of aortic aneurysm was created based on CT images. Properties in terms of wall shear stress, mean flow velocity, mean pressure, energy loss, and pressure loss coefficient were calculated using thermal fluid analysis software "ANSYS CFX." As the aneurysm expanded, the mean flow velocity decreased and the wall shear stress, mean pressure, energy loss, and pressure loss coefficient increased. Wall shear stress increased when the aneurysm was small, suggesting that is related to the development and growth of the aneurysm. (This is secondary publication from J Jpn Coll Angiol 2021; 61: 3-10.).

Quadruple perovskite CaCu3Fe2Re2O12: A potential actuator based on a multiscale model

In this study, the magnetic structure of CaCu 3 Fe 2 Re 2 O 12 is analyzed combined on a macro to micro-scale. To combine first-principles calculations and finite element methods, the magnetic properties, Young's modulus and Poisson's ratio are used as input parameters in the finite element methods calculations. As a function of applied magnetic field and actuator structure, the energy loss and magnetostrictive coefficient of an magnetostrictive actuator are identified. When the voltage and frequency are specified, a small bar radius and narrow air gap are preferred for a high magnetostrictive coefficient. The total range of simulation parameters results in a large magnetostrictive coefficient of 2700 ppm, which is higher than the one for Tb-Dy-Fe alloys. According to our results, CaCu 3 Fe 2 Re 2 O 12 can be designed to be used as actuators by controlling the structures and applying magnetic fields.

Impact of pressure recovery on the assessment of pulmonary homograft function using Doppler ultrasound.

Relevant pressure recovery (PR) has been shown to increase functional stenotic aortic valve orifice area and reduce left ventricular load. However, little is known about the relevance of PR in the pulmonary artery. The study examined the impact of PR using 2D-echocardiography in the pulmonary artery distal to the degenerated homograft in patients after Ross surgery. Ninety-two patients with pulmonary homograft were investigated by Doppler echocardiography (mean time interval after surgery 31 ± 26 months). PR was measured as a function of pulmonary artery diameter determined by computed tomography angiography. Homograft orifice area, valve resistance, and transvalvular stroke work were calculated with and without considering PR. PR decreased as the pulmonary artery diameter increased (r=-0.69, p < 0.001). Mean PR was 41.5 ± 7.1% of the Doppler-derived pressure gradient (Pmax ), which resulted in a markedly increased homograft orifice area (energy loss coefficient index [ELCOI] vs. effective orifice area index [EOAI], 1.3 ± 0.4 cm2 /m2 vs. 0.9 ± 0.4 cm2 /m2 , p < 0.001). PR significantly reduced homograft resistance and transvalvular stroke work (822 ± 433 vs. 349 ± 220 mmHg × ml, p < 0.0001). When PR was considered, the correlations of the parameters used were significantly better, and 11 of 18 patients (61%) in the group with severe homograft stenosis (EOAI <0.6 cm2 /m2 ) could be reclassified as moderate stenosis. Our results showed that the Doppler measurements overestimated the degree of homograft stenosis and thus the right ventricular load, when PR was neglected in the pulmonary artery. Therefore, Doppler measurements that ignore PR can misclassify homograft stenosis and may lead to premature surgery.

Sustainable Governance, Energy Security, and Energy Losses of Europe in Turbulent Times

The article aims to identify the relationship between energy efficiency and particular indicators of energy losses in Europe. The results of the bibliographic analysis showed a knowledge gap in energy losses in Europe regarding the new challenges of energy security. For the analysis, annual panel data from 32 European countries were collected from 1990 to 2019. The authors used the Jarque–Bera test to assess the normality of the residuals, utilized the Breush–Pagan test for heteroskedasticity check, and applied regression analysis to determine the relationship between energy efficiency and energy loss rates in Europe. To assess the effects of energy losses, the authors performed OLS modeling using the stats model’s package in Python. According to the modeling results, an increase in distribution losses (% of available energy from all sources) by 1% in Europe leads to an increase in energy consumption by 17.16% under other constant conditions. There is significant heterogeneity between European countries concerning energy efficiency and energy loss coefficients. Such a situation requires the development of new strategies and mechanisms to reduce energy losses, considering the challenges of energy security in Europe in turbulent times. Further research can be devoted to clustering European countries according to the main groups of energy losses: in the extraction, distribution, storage, and transformation of energy.

Corrugated thermoplastic polyurethane foams with high mechanical strength fabricated by integrating fused filament fabrication and microcellular foaming using supercritical CO2

Thermoplastic polyurethane (TPU) has been widely implemented in many fields due to its good elasticity. Microcellular foaming not only can achieve weight reduction, but also can enhance the elasticity of TPU products. However, the enhancement of elasticity by foaming is limited, while the introduction of corrugated structures can significantly improve the elasticity of TPU foams. Considering the difficulties to produce TPU parts with corrugated structures for conventional processes, fused filament fabrication (FFF) combined with microcellular foaming was developed to fabricate TPU foams with high elasticity. An FFF 3D printer was used to prepare solid TPU samples with corrugated structures, and microcellular foaming was used to fabricate foamed TPU samples. As expected, the corrugated structures have been successfully and precisely preserved in the obtained TPU foams, and further, the TPU foams have expansion ratio of more than 7 and cell density of higher than 1012 cells/cm3. Thanks to the corrugated structures and refined cellular morphology, the 7.09 expanded TPU foams exhibited outstanding compressive properties with an energy loss coefficient of 28% and a maximum stress of higher than 0.25 MPa. It is further found that introducing the corrugated structures or enlarging cell sizes could improve the elasticity and buffering performance of TPU foams.

The vibroacoustic characteristics and regulation rules of Panel–Cavity–Panel System controlled by Piezoelectric Shunt Oscillators with negative capacitors

Piezoelectric Shunt Oscillators (PSOs) are widely used in the passive and semi-active control of the vibration and acoustic radiation of flexible structures, due to PSOs’ high electromechanical coupling coefficients, robustness, effectiveness and adjustability at low frequencies. Panel–Cavity–Panel System (PCPS) is a common type of flexible structures, such as interior panels and windows of automobiles. In this paper, a theoretical model of PCPS controlled by PSOs and its vibration equations are established. The vibroacoustic characteristics of PCPS, including sound absorption coefficient (SAC), energy loss coefficient (ELC) and transmission loss (TL), are calculated using a unified mathematical form based on the vibroacoustic radiation impedance matrix, damping matrix and displacement response of PCPS, while a lumped parameter model of PCPS is derived to simplify the comprehension and extension of PCPS. Then the finite element simulation is used to calculate the vibroacoustic characteristics of the PCPS, which achieves good agreement with theoretical results, while three basic regulation modes are also summarized and verified. The regulation mechanism of PCPS controlled by PSOs is further analyzed by the velocity response of each panel. Finally, experiments of PCPS controlled by PSOs with negative capacitors are conducted in a standing wave tube, at non-eigenfrequencies ranging from 70 Hz to 220 Hz. It is found in experiments that PSOs with negative capacitor can increase the TL of PCPS about 8 dB to 25 dB, which depends on the target frequency. SAC and ELC can also be increased, which means less acoustic energy is reflected and more acoustic energy is dissipated in the shunt circuits.