Ideal Efficiency Research Articles

An Ultra-High Temperature Stable Solar Absorber Using the ZrC-Based Cermets

Exploring the spectrally selective absorbers with high optical performance and excellent thermal stability is crucial to improve the conversion efficiency of solar energy to electricity in concentrated solar power (CSP) systems. However, there are limited reports on the selective solar absorbers utilized at 900oC or above. Herein, we developed a selective absorption coating based on the ultra-high temperature ceramic ZrC and the quasi-optical microcavity (QOM) optical structure, and experimentally achieved the absorber via depositing an all-ceramic multilayer films on a stainless steel substrate by magnetron sputtering. The prepared multi-layer selective absorber demonstrates an excellent high solar absorptance of ∼0.964 due to the multi absorptance mechanisms in the QOM, and a relatively low thermal emittance of ∼0.16 (82°C). Moreover, the coating can survive at 900oC in vacuum for 100 h with a superior spectral selectivity of 0.96/0.143 (82°C) upon annealing, resulting from the introduction of ultra-high temperature ceramic ZrC in the QOM structure. Under the conditions of a stable operating temperature of 900°C and a concentration ratio of 1,000 suns, the calculated ideal conversion efficiency using this absorber can reach around 68%, exceeding most solar selective absorbers in previous reports.

Shortcut-to-adiabaticity quantum tripartite Otto cycle

For an Otto cycle there always exists a trade-off between the cycle efficiency and the output power due to the requirement of cycle length. The shortcut to adiabatic (STA) technology provides an effective way to deal with the difficulty of zero-output power in conventional Otto cycle. In this paper, the Otto cycle of three-qubit system as the working substance with counterdiabatic driving has been investigated. It is demonstrated that the tripartite Otto cycle as a universal machine, in the suitable regimes of external control parameter, could work as a quantum heat engine (QHE), refrigerator or heat pump. And, the performances of QHE and refrigerator with and without STA, such as the power and efficiency of QHE and the coefficient of performance (COP) and figure of merit (FOM) of refrigerator, have been investigated. It shows the application of STA scheme can lead to an effective enhancement in the performances of Otto cycle, including achievements of a high QHE’s/refrigerator’s power associated with a moderate QHE’s efficiency/COP of refrigerator. Especially, it is interesting that even in a short-time cycle the optimization of control parameters could arise a remarkable improvement in the efficiency (or COP) of STA QHE (refrigerator), approaching the ideal efficiency or COP of conventional Otto cycle with quasi-static process. Finally, with the aid of parameter optimization the trade-off regions between the efficiency and the power (the COP and the FOM) of STA Otto engine (refrigerator) have been advised.

Dual-frequency pulse laser based on acousto-optic modulation.

Non-collinear stimulated Brillouin scattering (SBS) amplification can obtain high peak power Stokes output while ensuring the stability, but the frequency mismatch reduces the energy conversion efficiency of the system. In this paper, a dual-frequency pulse laser based on acousto-optic crystal modulation is designed. The output pulse pair can be used as pump and Stokes light, respectively, which realizes the active frequency matching of the gain medium Brillouin frequency shift during the SBS amplification process and helps to maintain ideal energy conversion efficiency. The dual-frequency laser finally produced a laser pulse pair with a pulse width adjustment range of 100 ps-50 ns, a frequency shift range of 0 GHz-2 GHz, and the polarization extinction ratio (PER) reaches 20.82dB.

The diagnostic protocol for hereditary spherocytosis-2021 update.

BackgroundHereditary spherocytosis (HS), a commonly encountered hereditary hemolytic disease, is mostly inherited in an autosomal dominant manner. The clinical manifestations in patients with HS show obvious heterogeneity. Moreover, the sensitivity or specificity of some HS diagnostic tests are not ideal and may easily result in misdiagnosis or missed diagnosis in some patients. The objective of this study was to propose a simple and practical diagnostic protocol, which can contribute to the diagnosis of HS and its differential diagnosis with different types of hemolytic anemia such as thalassemia (THAL), autoimmune hemolytic anemia (AIHA), and glucose‐6‐phosphate dehydrogenase (G6PD) deficiency, thus, to provide an alternative simple and reliable method for better clinical diagnosis of HS.MethodsThrough combing our research with existing experimental technologies and studies, we propose a simple and practical protocol for HS diagnosis, which will help clinicians to improve HS diagnosis.ResultsCompared with the existing HS diagnostic protocols, the HS diagnostic protocol we proposed is simpler. In this new protocol, some experimental tests with ideal diagnostic efficiency are added, such as mean reticulocyte volume (MRV), mean sphered cell volume (MSCV), mean corpuscular volume (MCV), in combination with the observation of clinical manifestations, family investigation, routine tests for hemolytic anemia, genetic testing, and other screening tests.ConclusionThe HS diagnostic protocol we proposed could improve the clinical practice and efficiency of HS diagnosis.

Optical Quality of InAs/InP Quantum Dots on Distributed Bragg Reflector Emitting at 3rd Telecom Window Grown by Molecular Beam Epitaxy.

We present an experimental study on the optical quality of InAs/InP quantum dots (QDs). Investigated structures have application relevance due to emission in the 3rd telecommunication window. The nanostructures are grown by ripening-assisted molecular beam epitaxy. This leads to their unique properties, i.e., low spatial density and in-plane shape symmetry. These are advantageous for non-classical light generation for quantum technologies applications. As a measure of the internal quantum efficiency, the discrepancy between calculated and experimentally determined photon extraction efficiency is used. The investigated nanostructures exhibit close to ideal emission efficiency proving their high structural quality. The thermal stability of emission is investigated by means of microphotoluminescence. This allows to determine the maximal operation temperature of the device and reveal the main emission quenching channels. Emission quenching is predominantly caused by the transition of holes and electrons to higher QD’s levels. Additionally, these carriers could further leave the confinement potential via the dense ladder of QD states. Single QD emission is observed up to temperatures of about 100 K, comparable to the best results obtained for epitaxial QDs in this spectral range. The fundamental limit for the emission rate is the excitation radiative lifetime, which spreads from below 0.5 to almost 1.9 ns (GHz operation) without any clear spectral dispersion. Furthermore, carrier dynamics is also determined using time-correlated single-photon counting.

Interval Type-2 Fuzzy Logic Anti-Lock Braking Control for Electric Vehicles under Complex Road Conditions

To simultaneously track the ideal slip rate and realize ideal energy recovery efficiency under different complex road conditions, an electro-hydraulic compound anti-lock braking system based on interval type-2 fuzzy logic control strategy and its corresponding braking torque allocation strategy have been developed for electric vehicles. The proposed interval type-2 fuzzy logic controller aims to calculate the ideal total braking torque by four steps, namely, fuzzification, fuzzy inference, type reduction, and defuzzification. The slip rate error and the change rate of slip rate error are utilized as inputs in the fuzzification, and then, the membership degree interval of fuzzy variables determined by the upper and lower membership functions is used to calculate the activation degree interval of different fuzzy rules in the fuzzy inference process, which enhances the anti-interference ability to external uncertainties and internal uncertainties. The braking torque allocation strategy is proposed to maintain the maximum energy recovery efficiency on the premise of safe braking. The software of MATLAB/Simulink is applied to simulate the process of anti-lock braking control under two complex road conditions. Simulation results corroborate the proposed interval type-2 fuzzy logic anti-lock braking control system can not only obtain better slip rate control effect and outstanding robustness but also achieve ideal regenerative braking energy recovery efficiency under both joint-μ and split-μ road surfaces.

Synthesis and Evaluation of Al2O3_Mg/AA6061 Aluminium Foam Composite via Compaction and Sintering

In this paper compressive behaviour of an Aluminium foam composite have been evaluated and discussed. The outcome reflects that quasi static stress –strain curve of Al composite was same as to Al foams. However, within the two strain ranges from strain less than 0.03 and strain greater than 0.2, the ideal absorption energy of the composites was higher than that of parent Al foams. When the strain ranged from 0.03 to 0.2 the ideal energy absorption efficiency value of the composite was lower than the Al foams.
 There are many methods for fabricating metal foams but we preferred powder metallurgy process. This process of production allows for the production of complex shaped foam parts. Many alloys including Aluminium, zinc, tin, lead and steel can be produced using this method. The fabricated part has a closed cell microstructure and a high fraction of porosity. Mechanical properties foams are evaluated including the axial crushing, Hardness and toughness test are also carried out. Applications are such as light weight construction and energy absorption for civilians as well as military uses.

Measuring higher education performance in Brazil: government indicators of performance vs ideal solution efficiency measures

PurposeThis study extends the educational institutions' performance and efficiency literature by examining Brazil's Federal Institute of Education, Science and Technology (FIEST), which consists of educational units throughout the country that span several levels of education.Design/methodology/approachThe authors build and analyze a covariance matrix consisting of both a group of efficiency measures and a group of performance indicators used by Brazil's Ministry of Education (BME). The values in the covariance matrix are maximized through application of the Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS), in which the weights of each variable are optimized in order to capture the direction of the relationship between the two sets of efficiency measures.FindingsAlthough the authors find that the collective efficiency of the educational units analyzed did not change during the period of study, the analysis reveals that government indicators of performance do not exhibit a strong relationship to the ideal solution efficiency measures used in this study.Originality/valueThis study extends the educational institution efficiency literature by examining Brazil's FIEST, which consists of 40 educational units throughout the country that spans several levels of education, from upper high school vocational courses to higher degrees.

Application of Magnetic Composites in Removal of Tetracycline through Adsorption and Advanced Oxidation Processes (AOPs): A Review

Water pollution induced by the tetracycline (TC) has caused global increasing attention owing to its extensive use, environmental persistence, and potential harm for human health. Adsorption and advanced oxidation processes (AOPs) have been promising techniques for TC removal due to ideal effectiveness and efficiency. Magnetic composites (MCs) which exploit the combined advantages of nano scale, alternative sources, easy preparation, and separation from wastewater are widely used for catalysis and adsorption. Herein, we intensively reviewed the available literature in order to provide comprehensive insight into the applications and mechanisms of MCs for removal of TC by adsorption and AOPs. The synthesis methods of MCs, the TC adsorption, and removal mechanisms are fully discussed. MCs serve as efficient adsorbents and photocatalysts with superior performance of photocatalytic performance in TC degradation. In addition, the TC can be effectively decomposed by the Fenton-based and SO4•− mediated oxidation under catalysis of the reported MCs with excellent catalytic performance. Based on the existing literature, we further discuss the challenge and future perspectives in MCs-based adsorption and AOPs in removing TC.

Exergy and Energy Analyses of the Spirulina Microalgae Blends in a Direct Injection Engine at Variable Engine Loads

Abstract This article explores the exergy analysis of the diesel engine with the selected Spirulina microalgae bio-oil (SMBO) biodiesel. The adaptability of the biofuels as an efficient replacement to the fossil fuel has to be tested and proved. To estimate the overall efficiency of the engine with the biofuel blends, it is essential to find out the energy conversion capability of the engine. Different fuel blends were taken as B0 (100% diesel), B10 (10% SMBO + 90% diesel), B20 (20% SMBO + 80% diesel), and B30 (30% SMBO + 70% diesel). All experimental tests were conducted in a naturally aspirated directly injected engine. The brake power (BP), heat release rate (HRR), exergy destruction, ideal efficiency, actual efficiency, exergy rate and energy rate of the fuel, as well as exhaust were measured for all fuel blends. All tests were conducted at different rpm values from 0 to 3000 rpm with 500 rpm interval and also at different loads such as 0%, 25%, 50%, 75%, and 100% load. The loss of exergy of fuel and thermal was on the rise and noticed in B0, B10, B20, and B30, while the HRR and loss of exergy rate were found in exhaust as more decreasing one in B10, B20, and B30 fuel blends than B0 (pure diesel).

Numerical investigation on novel water distribution for natural draft wet cooling tower

Natural draft wet cooling tower is widely used in cold end system of thermal power plants, however, the water droplets in the central area cannot be sufficiently cooled due to small air flow rate. In this paper, a novel water distribution mode is proposed for the wet cooling tower, in which the water distribution area is divided into four subdomains equally in the radius direction, with the diameters of sprayed water droplets from the inside to the outside of 4 mm, 3 mm, 1 mm and 0.5 mm, respectively. The three-dimensional numerical model of natural draft wet cooling tower is developed and validated by the published data, and the cooling performance with the novel water distribution mode is then obtained. The results show that the air velocity in the central area is significantly increased thus the velocity gets more uniformly distributed with the novel water distribution mode. Besides, the thermal performance in the external area is also improved thanks to the larger contact area between the cooling air and water droplets. By comparing the proposed water distribution with the conventional one, it can be found that the outlet water temperature decreases by up to 0.69 °C, and the tower with the proposed water distribution can achieve better heat and mass transfer performances with a lower air mass flow rate, which can be recommended in engineering applications for an ideal energy efficiency of cold end system.

Gain-Boosted Super Class AB OTAs Based on Nested Local Feedback

A new approach to design super class AB operational transconductance amplifiers (OTAs) with enhanced large-signal and small-signal performance is presented. It is based on employing two nested positive and negative feedback loops at the active load of an adaptively biased differential pair in weak inversion region. As a result, DC gain, gain-bandwidth product, settling time and noise are improved compared to conventional super class AB OTAs without extra circuit nodes or power consumption. Measurement results of a 180 nm CMOS test chip prototype show a current boosting factor higher than 5000 and a nearly ideal current efficiency. Due to the ultra-low quiescent currents and high driving capability, the circuit exhibits an excellent large-signal figure-of-merit (FOM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> ) of 236 V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . To illustrate the applicability of the proposed approach, a differential sample-and-hold (S/H) circuit was designed and fabricated on the same test chip. Measurement results of the S/H validate the advantages of the proposal.

Study on the Removal Effect of Salmonella Typhimurium Biofilm

Objective: This research focused on the effects of different disinfectants, preservatives and natural ingredients commonly used in the food industry on the biofilm of Salmonella typhimurium. Methods: By adding different kinds and concentrations of scavengers during the culture process, the influence on the formation of biofilm was determined. The mature biofilm was soaked with various selected scavengers to evaluate the clearance effect under different concentrations of each substance. The metabolic activity of bacteria cells in the biofilm was determined by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. And the number of viable bacteria was calculated by dilution plate coating method. Results: The disinfectant ethanol (50%), hydrogen peroxide (1%), benzalkonium chloride (0.6%), benzalkonium bromide (0.6%), and natural components carvol, cinnamaldehyde and thyme essential oil (1.0 μL/mL) could effectively inhibit the formation of S. typhimurium CDC3 and S. typhimurium ST34. Disinfectants detergent, hydrogen peroxide, natural ingredients (carvol, cinnamaldehyde and thyme essential oil) showed certain advantages in the removal of mature biofilm. Among them, the most ideal removal efficiency was hydrogen peroxide, which could reach about 90%, the maximum removal rate of detergent could reach 80%, and the essential oils of carvacrol, cinnamaldehyde and thyme could reach about 70%; The disinfectant ethanol, benzalkonium chloride and benzalkonium bromide, as well as the natural components carvol, cinnamaldehyde and thyme essential oil could significantly reduce the cell metabolic activity and the number of viable bacteria in biofilm, the number of viable bacteria in the biofilm could be reduced by 2 to 3 lg values. Conclusions: In contrast with the removal of mature biofilm, the addition of scavenging agent or natural ingredients at the early stage of cultivation made up for a more efficient control of the biofilm.

Deep-Learning Temporal Predictor via Bidirectional Self-Attentive Encoder–Decoder Framework for IOT-Based Environmental Sensing in Intelligent Greenhouse

Smart agricultural greenhouses provide well-controlled conditions for crop cultivation but require accurate prediction of environmental factors to ensure ideal crop growth and management efficiency. Due to the limitations of existing predictors in dealing with massive, nonlinear, and dynamic temporal data, this study proposes a bidirectional self-attentive encoder–decoder framework (BEDA) to construct the long-time predictor for multiple environmental factors with high nonlinearity and noise in a smart greenhouse. Firstly, the original data are denoised by wavelet threshold filter and pretreatment operations. Secondly, the bidirectional long short-term-memory is selected as the fundamental unit to extract time-serial features. Then, the multi-head self-attention mechanism is incorporated into the encoder–decoder framework to improve the prediction performance. Experimental investigations are conducted in a practical greenhouse to accurately predict indoor environmental factors (temperature, humidity, and CO2) from noisy IoT-based sensors. The best model for all datasets was the proposed BEDA method, with the root mean square error of three factors’ prediction reduced to 2.726, 3.621, and 49.817, and with an R of 0.749 for temperature, 0.848 for humidity, and 0.8711 for CO2 concentration, respectively. The experimental results show that the favorable prediction accuracy, robustness, and generalization of the proposed method make it suitable to more precisely manage greenhouses.

Conformational Freedom‐Enhanced Optomechanical Energy Conversion Efficiency in Bulk Azo‐Polyimides

AbstractAzobenzene‐doped glassy polyimides (azo‐polyimides) offer some of the most efficient optomechanical power densities to date rivaling electrostrictive polymers. Despite such potential attributes, the optomechanical efficiency remains low in comparison to other smart materials. Using high‐fidelity coarse‐grained molecular dynamics simulations, the authors reconcile both experimental and theoretical challenges to understand the limiting factors for the optomechanical conversion in photostrictive polymers. Interestingly, the ideal optomechanical efficiency of 10–24% for a single‐chain azo‐imide monomer predicted here is equal to or a little higher than experimental reports, suggesting experimental design space. The time‐dependent optomechanical efficiency of bulk azo‐polyimide is quantified, for the first time, to be strongly correlated with the initial free volumes, a measure of polymer conformational freedom. This trend is elaborated by conformational order parameters and viscoelastic relaxation moduli. Resembling the role of porosity in azobenzene‐contained metal/covalent organic frameworks to enhance the photo‐switching efficiency, a larger conformational freedom enables &gt;10 times increase in optomechanical efficiency comparing to existing experiments. This is primarily due to facilitated viscoelastic relaxation after photo‐switching which alleviates residual stresses quickly and reduces heat dissipation. These findings suggest opportunities to improve the optomechanical performance through targeted strategies, such as porosity control and thermal annealing.

Efficient coupling between an integrated photonic waveguide and an optical fiber.

Because on-chip integration of light sources cannot be realized effectively now, integrated nanophotonic chips must couple external light to the integrated photonic waveguide with high efficiency. Realizing high efficiency coupling requires a low-loss coupling structure. In this paper, the factors allowing high efficiency coupling to be realized are analyzed theoretically and the coupling between a lensed fiber and a tapered silicon nitride (Si3N4) waveguide is realized experimentally. Because the coupling efficiency of this structure is not ideal in the experiment, a scheme of direct alignment between the lensed fiber and a cantilever waveguide is proposed. Although the scheme offers a very high coupling efficiency in theory, because of the warpage of the waveguide they cannot be directly aligned experimentally. Finally, this paper advances a scheme for the tapered fiber to be directly overlapped onto the Si3N4/SiO2 cantilever. It is found that the coupler maintains an ideal coupling efficiency for wavelength from 1530 nm to 1600 nm, laying a foundation for the integration of nano-photonic devices and optical fibers.

Performance analyses and optimizations of desiccant wheel-assisted atmospheric water harvesting systems based on ideal thermodynamic cycles

This study proposes a novel atmospheric water harvesting system that uses desiccant wheels to transfer vapor from one air stream (Adeh) to another (Ahum), and the humidified Ahum is cooled to obtain water. First, the ideal air handling processes of desiccant wheels are introduced, and the heating temperature and ideal humidification efficiency are compared among the three humidification configurations. The system with multi-stage desiccant wheels and independent Adeh performs best, with an ideal humidification efficiency that is 0.4 to 2.2 times higher than that of the other two systems. The ideal water harvesting efficiency of the system is much higher than that of the direct cooling water harvesting method. A two-stage humidification system using actual desiccant wheels is then designed. Driven by ideal heating and cooling systems, water harvesting rates and water harvesting efficiencies are calculated under typical dry and mild working conditions. When the heating temperature is from 40 °C to 90 °C, and the cooling source temperature ranges from 0 °C to 12 °C, diagrams are drawn to assist the selection of the heating temperature and cooling source temperature to obtain the highest water harvesting efficiency for different water harvesting rates. Finally, vapor compression cycles are used as heating and cooling sources, and the performance of the system is compared with that of the direct cooling method. Although this system has higher water harvesting rates, water harvesting efficiencies can be higher when the ambient relative humidity ratio is lower than 60%. With solar thermal energy, water harvesting efficiencies are higher than those of the direct cooling method, especially when the relative humidity ratio is high.

Concept for Realizing High Output Power Density Thermionic Energy Convertor by Field-Assisted Thermionic Emission Using a Direct-Tunneling Metal–Insulator–Graphene Cathode

The usage of waste heat is an effective way to satisfy the great demand for energy in modern human society. A thermionic energy convertor (TEC) can directly produce electricity from thermal energy with high efficiency. However, high working temperature is one of the major challenges in TEC. In this work, a concept based on field-assisted thermionic emission (FTE) has been proposed to solve this problem. Basically, the field-assisted thermionic energy convertor (FTEC) uses a metal-insulator-graphene (MIG) structure as the cathode to produce direct-tunneling FTE current for the conversion. The fundamental performance of FTEC has been theoretically studied. The penetration field within the MIG structure that controls both the FTE current and the hot electron energy is the key for the performance optimization. By engineering the MIG cathode band structure to balance the above mentioned effects of the penetration field, the ideal efficiency of ~10% and the corresponding output power density of ~5 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> can be obtained simultaneously under 700 K. Further comparison between FTEC and conventional TEC indicates that the output power density can be improved by at least four orders of magnitude under a mild temperature (600-700 K). These results provide a universal approach for realizing compact high output power density TEC and its combined system.

High-Performance and Stable Perovskite-Based Photoanode Encapsulated by Blanket-Cover Method

Perovskite-based photoelectrodes have demonstrated great potential in the field of solar energy conversion and solar fuel owing to the excellent optoelectronic properties of organic–inorganic hybrid halide perovskites. However, the instability of perovskite limits its development. Herein, a double-layer graphite sheet/nickel (GS/Ni) is introduced as an efficient waterproof to encapsulate the perovskite-based photoanode for solar-to-fuel generation directly in an aqueous solution. The photoanodes, which are fabricated by perovskite solar cell as a light harvester, exhibit outstanding performance with an onset potential shift of 1100 mV, photocurrent density of 17.4 mA/cm2 at 1.23 VRHE, and ideal ratiometric power-saved efficiency of 5.82%. The perovskite-based photoanode demonstrates enhanced stability for over 40 h in 1 M KOH. The active area of photoanode is expanded to 0.7 cm2 via scalable encapsulation technique with outstanding photoelectrochemical performance. The photoanodes encapsulated by GS/Ni show remarkable stability and photocurrent density, which indicates that it is a promising candidate for photoelectrochemical solar fuel generation.

Assessing Flare Combustion Efficiency using Imaging Fourier Transform Spectroscopy

Flaring plays a critical role in reducing the environmental impact of upstream oil and gas processing by converting methane and other gaseous hydrocarbons into CO2, which has a lower global warming potential. This process is highly efficient under ideal conditions but efficiency may be significantly lower under certain scenarios such as fuel stripping under crosswind and emission of volatile organic compounds and unburned fuels due to over-aeration or over-steaming in assisted flares. This study assesses the potential of using imaging Fourier transform spectrometers (IFTSs) to directly measure combustion efficiency by combining species column densities estimated from a spectroscopic model with intensity-weighted velocities found using an optical flow model. Simulated measurements using a computational fluid dynamics (CFD)-large eddy simulation of a flare in a crosswind are used to establish the technique's viability, followed by experimental measurements on a heated gas vent to validate the optical flow model. Finally, preliminary measurements are carried out on a laboratory-scale steam- and air-assisted flare. While the simulated measurements and heated vent experiments support the feasibility of this approach, experimentally-derived spectra from the lab-scale flare were contaminated with artifacts attributed to turbulent fluctuations, which complicates the quantitative interpretation of the IFTS data.