Ultimate Efficiency Research Articles

A unified intelligent model for estimating the (gas + n-alkane) interfacial tension based on the eXtreme gradient boosting (XGBoost) trees

The interfacial tension (IFT) between the injecting gas and host oil is a key parameter that affects the ultimate displacement efficiency and gas injection enhanced oil recovery (EOR) performance. The accurate characterization of the IFT between varying n-alkanes and injecting gases is crucial to obtaining deeper insight into the predominating mechanisms behind the interfacial behaviors of (gas + oil) systems, and in turn ensuring the optimal design of gas injection EOR projects. Laboratory measurement of the IFT usually requires expensive experimental apparatus, time-consuming operation procedure and cumbersome data deduction. This paper proposed the use of a novel supervised learning (SL) method, namely the eXtreme gradient boosting (XGBoost) trees, for the fast estimation of (gas + n-alkane) IFT. A unified estimation model was constructed for varying injecting gas species and n-alkanes based on a large database consisting of a number of 1561 data sets. Results showed that the unified model is capable of accurately reproducing the experimental IFT based on pressure, temperature, n-alkane molecular weight and gas composition. It was also demonstrated that the new model outperforms the multi-layer perceptron (MLP), support vector regression (SVR) and existing correlations in terms of accuracy and robustness. Furthermore, the permutation importance (PI) was applied to quantify the importance of each input feature to the IFT, which concluded that the ranking of features in terms of decreasing importance to the (gas + n-alkane) IFT are: pressure ≫ n-alkane molecular weight > gas composition > temperature.

Study on AlxGa1-xAs nanocones with variable Al composition structures for highly efficient light trapping

In this study, various AlxGa1-xAs nanostructure arrays with variable Al composition are proposed and designed for highly efficient light capture. The optical properties of the proposed nanocone array with variable Al composition have been numerically investigated by COMSOL Multiphysics package based on the finite element method (FEM), and compared with the counterparts of cylinder and conical frustum. The results show that the variable composition AlxGa1-xAs nanocones with uniform sublayer distribution thickness can obtain an ultimate efficiency of 37.3%, which is higher than that of the cylindrical and conical frustum structures under the same conditions. In addition, the effects of geometric parameters of nanostructures on the light absorption of nanoarrays with different shape changing components are studied. Taking the variable component AlxGa1-xAs nanocone structure as an example, increasing the Al component range in the axial direction of the nanocone can significantly improve the absorption of short-wavelength light, which increases the overall absorption efficiency. In addition, for a specific Al composition distribution range, a uniform thickness distribution design of unit sub-layer in nanocone along the z-axis direction can provide optical absorption enhancement of more than 1.8% and 0.9% over than the decreasing and increasing distribution design. The design principles proposed in this work will provide a reference for selecting appropriate parameters in solar cell applications.

Mechanical and Microstructural Characterization of Friction Stir-Welded AA2219: TiCp-Reinforced Composites

Light materials having high strength-to-weight ratio plays a vital role in material science especially in the field of aerospace, marine transportation, military and structural applications. Composite serves the same. Aluminium matrix composite (AMC) is the aluminium matrix which has high strength-to-weight ratio. The purpose of the work is to investigate the mechanical properties of welded AA2219 aluminium alloy reinforced with titanium carbide particles (TiCp). Aluminium matrix is reinforced with TiCp using modified stir casting process. Optical colour graphs, XRD and EDX analysis reveal the presence of TiCp in cast AMC. Tensile test shows the ultimate tensile strength increases with the percentage of TiCp addition. Cut samples of size 100 mm X 50 mm X 6 mm cast AMC were friction stir welded using response surface modelling. Ultimate tensile strength and joint efficiency were calculated for the weld samples, and the effects of input parameters were investigated. Experimental results indicate that tool pin profile has a significant effect on tensile strength of friction stir-welded joints followed by welding speed. It is evident from the response that tool rotational speed had the least effect on ultimate tensile strength. The calculated joint efficiency of the most weld samples was more than 90% with respect to the ultimate tensile strength of the base metal. This work ensures defect free, high efficiency welded joints produced using a wide range of process parameters and recommends parameters for producing best joint tensile properties.

Influences of welding speed on microstructure and mechanical properties of friction stir welded Al–Mg alloy with high Mg content

In this work, the influences of welding speed on microstructure and mechanical properties in friction stir welding (FSW) of the hot-rolled Al-9.2Mg-0.8Mn-0.2Zr-0.15Ti alloy plates has been investigated. Microstructures and mechanical properties of the joints are characterized by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with electron dispersive spectroscopy (EDS), hardness and tensile testing. The results show that all the joints are free of volume defects at the welding speed of 25–100 mm min−1 and the fixed rotation rate of 1000 rpm. And all the nugget zones (NZs) are characteristics of fine grains with the high angle grain boundaries (HAGBs) fraction higher than 90% at the welding speed of 25–100 mm min−1. The mean grain size in NZs and tensile properties of joints exhibit a parabolic relation with the welding speed. Furthermore, the optimal welding parameters are the welding speed of 50 mm min−1 and the rotation rate of 1000 rpm. The as-prepared joint at 50 mm min−1, featured with the smallest grain size of 3.02 μm and a uniform distribution of the fine second phase particles in NZ, exhibits the highest elongation to rupture about 45% higher than the base metal (22.2 ± 1.6%) and the highest ultimate tensile strength efficiency of 87.4%. It can be attribute to the synergetic effect of the fine-grain structure with the high HAGBs fraction and the small second phase particles with a uniform distribution.

Have countries moved towards sustainable development or not? Definition, criteria, indicators and empirical analysis

Have countries moved towards sustainable development (SD) or not? To answer the question, first, a new SD definition, i.e. “Achieving higher and more equally distributed well-being levels within ecological limits”, is proposed. Second, based on the definition and from a global perspective, four criteria are established to judge whether countries have moved towards SD, which are: (1) well-being levels have been higher and more equally distributed; (2) levels of ecological consumption have been lower; (3) ecological capacities have strengthened; and (4) the Ultimate Efficiency, which is the efficiency of transforming ecological consumption into human well-being, has improved. Developing countries with ecological consumption below global average do not have to meet the second criterion. Third, the Happy and Equal Human Development Index, the Ecological Footprint and the Biocapacity are selected to measure human well-being, ecological consumption and ecological capacities, respectively and two consistent methods are used to measure the Ultimate Efficiency. The empirical analysis of 102 countries during 2011–2016 demonstrates that 19 countries have met the required four or three criteria and moved towards SD and that 12 countries have met none of the required criteria and moved against SD. The main contribution is to provide a clear SD definition, specific criteria and reliable indicators for measuring national performance and informing decision making on moving towards SD. Therefore, whether countries have moved towards SD or not can be judged and measured continuously and regularly. Future research needs to detailedly explore why countries have met or not met one certain criterion.

Highly Efficient and Easily Recoverable Ag3PO4–TiO2–Fe2O3 Magnetic Photocatalyst with Wide Spectral Range for Water Treatment

A new magnetic Ag3PO4–TiO2–Fe2O3 photocatalyst (Ag–Ti–Fe) has been synthesized by a solid-state blending method. The sample was analyzed by XRD, FT-IR, and VSM, and its photocatalytic performance in treatment of simulated dye-contaminated wastewater was evaluated in photocatalytic tests. SEM and FT-IR results confirmed that Ag–Ti–Fe catalyst was composed of Ag3PO4, anatase and maghemite. Results of photocatalytic tests revealed that Ag–Ti–Fe exhibited the highest photocatalytic activity on water treatment compared with contrastive samples whether the light source was UV or visible light, and the ultimate degradation efficiency of orange II reached 86.71 and 78.13%, respectively. Ag–Ti–Fe could decompose chemically stable groups, rather than simply destroy chromogenic azo double bonds, and it could further effectively remove methyl orange, rhodamine B, methylene blue from water, respectively. VSM results showed that the saturation magnetization of Ag–Ti–Fe was 4.80 emu/g, and it could be separated simply and quickly with the magnetic field.

The X-Ray Emission Effectiveness of Plasma Mirrors: Reexamining Power-Law Scaling for Relativistic High-Order Harmonic Generation

Ultrashort pulsed lasers provide uniquely detailed access to the ultrafast dynamics of physical, chemical, and biological systems, but only a handful of wavelengths are directly produced by solid-state lasers, necessitating efficient high-power frequency conversion. Relativistic plasma mirrors generate broadband power-law spectra, that may span the gap between petawatt-class infrared laser facilities and x-ray free-electron lasers; despite substantial theoretical work the ultimate efficiency of this relativistic high-order-harmonic generation remains unclear. We show that the coherent radiation emitted by plasma mirrors follows a power-law distribution of energy over frequency with an exponent that, even in the ultrarelativistic limit, strongly depends on the ratio of laser intensity to plasma density and exceeds the frequently quoted value of −8/3 over a wide range of parameters. The coherent synchrotron emission model, when adequately corrected for the finite width of emitting electron bunches, is not just valid for p-polarized light and thin foil targets, but generally describes relativistic harmonic generation, including at normal incidence and with finite-gradient plasmas. Our numerical results support the ω−4/3 scaling of the synchrotron emission model as a limiting efficiency of the process under most conditions. The highest frequencies that can be generated with this scaling are usually restricted by the width of the emitting electron bunch rather than the Lorentz factor of the fastest electrons. The theoretical scaling relations developed here suggest, for example, that with a 20-PW 800-nm driving laser, 1 TW/harmonic can be produced for 1-keV photons.

Organic Light-Emitting Diodes: Pushing Toward the Limits and Beyond.

Organic light-emitting diodes (OLEDs) are established as a mainstream light source for display applications and can now be found in a plethora of consumer electronic devices used daily. This success can be attributed to the rich luminescent properties of organic materials, but efficiency enhancement made over the last few decades has also played a significant role in making OLEDs a practically viable technology. This report summarizes the efforts made so far to improve the external quantum efficiency (EQE) of OLEDs and discusses what should further be done to push toward the ultimate efficiency that can be offered by OLEDs. The study indicates that EQE close to 58% and 80% can be within reach without and with additional light extraction structures, respectively, with an optimal combination of cavity engineering, low-index transport layers, and horizontal dipole orientation. In addition, recent endeavors to identify possible applications of OLEDs beyond displays are presented with emphasis on their potential in wearable healthcare, such as OLED-based pulse oximetry as well as phototherapeutic applications based on body-attachable flexible OLED patches. OLEDs with fabric-like form factors and washable encapsulation strategies are also introduced as technologies essential to the success of OLED-based wearable electronics.

Improving CNT-Si solar cells by metal chloride-to-oxide transformation

Transitional metal oxides (TMOs) are important functional materials in silicon-based and thin-film optoelectronics. Here, TMOs are applied in carbon nanotube (CNT)-Si solar cells by spin-coating solutions of metal chlorides that undergo favorable transformation in ambient conditions. An unconventional change in solar cell behavior is observed after coating two particular chlorides (MoCl5 and WCl6, respectively), characterized by an initial severe degradation followed by gradual recovery and then well surpassing the original performance. Detailed analysis reveals that the formation of corresponding oxides (MoO3 and WO3) enables two primary functions on both CNTs (p-type doping) and Si (inducing inversion layer), leading to significant improvement in open-circuit voltage and fill factor, with power conversion efficiencies up to 13.0% (MoO3) and 13.4% (WO3). Further combining with other chlorides to increase the short-circuit current, ultimate cells efficiencies achieve >16% with over 90% retention after 24 h, which are among the highest stable efficiencies reported for CNT-Si solar cells. The transformation of functional layers as demonstrated here has profound influence on the device characteristics, and represents a potential strategy in low-cost manufacturing of next-generation high efficiency photovoltaics.

Optical Structural and Morphological Studies of Cu0.5Zn0.5Se thin film deposited by chemical bath deposition method

Abstract The Copper Zinc chalcogenides thin films have been considered as an important material for use in optoelectronic devices. These compoundshowever, possess limitations on the ultimate efficiency and stability of devices due to weak nature ZnSebond. Themajorconsequences faced are lattice instability, poor mechanical, optical and electrical proprties.In view of this ,we report, a simple, aqueous chemical route to grow a single range of Cu0.5Zn0.5Se (x= 0.5) alloy semiconductor system on glass substrate at room temperature with special emphasis on their structural , surface morphological , optical , and electrical properties. The XRD study revealed the polycrystalline nature for all composition in a single cubic phase. The film was uniform, adherent, with color varying from faint red for ZnSe to dark red for CuSe .The high transmittance of the film in certain range of the solar spectrum and large band gap make them good material for selective coating and absorber layer for solar cell, respectively.Analysis of absorption spectra gave direct band gap is 1.9 eV.The electrical conductivity and activation energy was found to be a function of composition (x=0.5). Chemical deposition system is useful in depositing Cu0.5Zn0.5Se thin film of desired properties by careful selection of compositional parameter (x = 0.5)

The interaction between language and working memory: a systematic review of fMRI studies in the past two decades.

Language processing involves other cognitive domains, including Working Memory (WM). Much detail about the neural correlates of language and WM interaction remains unclear. This review summarizes the evidence for the interaction between WM and language obtained via functional Magnetic Resonance Imaging (fMRI) in the past two decades. The search was limited to PubMed, Google Scholar, Science direct and Neurosynth for working memory, language, fMRI, neuroimaging, cognition, attention, network, connectome keywords. The exclusion criteria consisted of studies including children, older adults, bilingual or multilingual population, clinical cases, music, sign language, speech, motor processing, review papers, meta-analyses, electroencephalography/event-related potential, and positron emission tomography. A total of 20 articles were included and discussed in four categories: language comprehension, language production, syntax, and networks. Studies on neural correlates of WM and language interaction are rare. Language tasks that involve WM activate common neural systems. Activated areas can be associated with cognitive concepts proposed by Baddeley and Hitch (1974), including the phonological loop of WM (mainly Broca and Wernicke's areas), other prefrontal cortex and right hemispheric regions linked to the visuospatial sketchpad. There is a clear, dynamic interaction between language and WM, reflected in the involvement of subcortical structures, particularly the basal ganglia (caudate), and of widespread right hemispheric regions. WM involvement is levered by cognitive demand in response to task complexity. High WM capacity readers draw upon buffer memory systems in midline cortical areas to decrease the WM demands for efficiency. Different dynamic networks are involved in WM and language interaction in response to the task in hand for an ultimate brain function efficiency, modulated by language modality and attention.

Experimental investigation on novel desalination system via gas hydrate

Freshwater scarcity has been troubling the high-quality development of many countries and regions, and seawater desalination is a vital source of freshwater. Recently, gas hydrate based desalination (GHBD) technology attracts much attention because of bringing no extra pollution to water. We developed a novel multifunctional desalination apparatus via gas hydrate with various operation modes and separation methods. In this study, the desalination characters under different separation modes were conducted using simulated seawater, and the hydrate-purging method with a desalination efficiency of more than 80% was selected to desalt the natural seawater sample. In addition, the purging method can greatly improve the desalination effects of both squeezed hydrate column and loose hydrates. The experimental results indicate that the removal efficiencies of different ions in the seawater were similar and their difference was related to the strength of ionic hydration. And above all, we designed and conducted a continuous desalination process including multiple injection, separation, washing and purging operations. The ultimate desalination efficiency using hydrate-purging method was over 80%, and the freshwater recovery was above 30% with 200 mL initial seawater in this study. The experimental proposal and results of this study are of great significance to the development of GHBD technology.

Growth of hierarchical ZnO nano flower on large functionalized rGO sheet for superior photocatalytic mineralization of antibiotic

In this study, reduced graphene oxide supported mesoporous zinc oxide ([email protected]) was synthesized and applied for the photocatalytic mineralization of ofloxacin, an antibiotic, in the aqueous solution. In-situ [email protected] nano-photocatalysts with different rGO content (0.2%, 0.5%, 1% and 2%) were synthesized using a reflux column method. The nano-photocatalyst was characterized by its structural (crystallinity), morphological, as well as optical properties with the help of powdered X-ray diffraction (P-XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, Brauner Emmet Teller (BET), thermo-gravimetric/differential thermal analysis (TGA/DTA) and UV–vis diffuse reflectance spectroscopy (DRS). The influences of pH (5–9) and catalyst dose (400–1400 mg/dm3) with irradiation time were studied. At optimum conditions (0.5% [email protected] dose of 1200 mg/dm3 for ofloxacin, pH = 7, and time = 300 min), ultimate degradation efficiency was found to be ≈99%, under UV light irradiation. The degradation kinetics fitted well with the first-order kinetic model. The photocatalytic mechanism of the enhanced photo-degradation in the presence of rGO was studied by comparing band structure with the potentials of the main reactive species (O2− and OH), which result in the mineralization of ofloxacin. The intermediates and pathways during the mineralization were determined using liquid chromatography, which is coupled with mass spectrometry (LC–MS) analysis and a possible pathway was also proposed on the basis of identified intermediates.

Hexylammonium Iodide Derived Two-Dimensional Perovskite as Interfacial Passivation Layer in Efficient Two-Dimensional/Three-Dimensional Perovskite Solar Cells.

Defects locating within grain boundaries or on the film surface, especially organic cation vacancies and iodine vacancies, make the fabrication of perovskite solar cells (PSCs) with superior performance a challenge. Organic ammonium iodide is a promising candidate and has been frequently used to passivate these defects by forming two-dimensional (2D) perovskite. In this work, it is found that the chain length of organic ammonium iodide is a crucial factor on the defect passivation effect. Compared to butylammonium iodide, the hexylammonium iodide (HAI)-derived 2D perovskite is more efficient in decreasing interfacial defects, resulting in a notably enhanced photoluminescence lifetime and a more suppressed interfacial charge recombination process. As a consequence, the ultimate power conversion efficiency (PCE) has reached 20.62% (3D + HAI) as compared to 18.83% (3D). Moreover, the long-term durability of the corresponding PSCs against humidity and heat is simultaneously improved. This work once again demonstrates that the 2D/3D structure is promising for further improving the PCE and stability of PSCs.

Electrical characteristics of modified truncated cone nanowire for efficient light trapping

In this paper, a novel design of truncated cone nanowires (NWs) solar cell (SC) with air gap is studied and analyzed. The optical and electrical characterizations are obtained using Lumerical finite difference time domain (FDTD) and Lumerical Device software packages. The modified truncated cone NWs have an upper air hole gap to increase the light confinement through the suggested design. In this study, ultimate efficiency, short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE) are calculated to compute the optoelectronics performance of the reported NWs. Moreover, the geometrical parameters of the studied design are adjusted to maximize the absorption through the modified structure. Furthermore, the Shockley-Read-Hall (SRH) lifetimes and doping concentrations are tuned to increase the PCE. The investigated NWs achieve an optical ultimate efficiency and Jsc of 42.74 % and 34.98 mA/cm2, respectively with an enhancement of 18.15 % over conventional conical NWs. Further, the radial doping of the reported design shows short circuit current density of 32.16 mA/cm2, open circuit voltage of 0.66 V and PCE of 15.36 %. An electronic implementation of the suggested NWs SC is also made using single diode model which shows a good agreement with the simulation results. Therefore, the suggested NWs design is a promising design for developing low cost and highly efficient SC.

Fundamental limits of hot carrier injection from metal in nanoplasmonics

Abstract The evolution of non-equilibrium carriers excited in the process of decay of surface plasmon polaritons (SPPs) in metal is described for each step – from the generation of carriers to their extraction from the metal. The relative importance of various carrier-generating mechanisms is discussed. It is shown that both the generation of carriers and their decay are inherently quantum processes as, for realistic illumination conditions, no more than a single SPP per nanoparticle exists at a given time. As a result, the distribution of non-equilibrium carriers cannot be described by a single temperature. It is also shown that the originally excited carriers that have not undergone a single electron-electron scattering event are practically the only ones that contribute to the injection. The role of momentum conservation in carrier extraction is discussed, and it is shown that, if all the momentum conservation rules are relaxed, it is the density of states in the semiconductor/dielectric that determines the ultimate injection efficiency. A set of recommendations aimed at improving the efficiency of plasmonic-assisted photodetection and (to a lesser degree) photocatalysis is made in the end.

Power Management for Multicore Processors via Heterogeneous Voltage Regulation and Machine Learning Enabled Adaptation

This work is based on the vision that the ultimate power integrity and efficiency may be best achieved via a heterogeneous chain of voltage processing starting from onboard switching voltage regulators (VRs), to on-chip switching VRs, and finally to networks of distributed on-chip linear VRs. As such, we propose a heterogeneous voltage regulation (HVR) architecture encompassing regulators with complimentary characteristics in response time, size, and efficiency. By exploring the rich heterogeneity and tunability in HVR, we develop systematic workload-aware power management policies to adapt heterogeneous VRs with respect to workload change at multiple temporal scales to significantly improve system power efficiency while providing a guarantee for power integrity. The proposed techniques are further supported by hardware-accelerated machine learning (ML) prediction of nonuniform spatial workload distributions for more accurate HVR adaptation at fine time granularity. Our evaluations based on the PARSEC benchmark suite show that the proposed adaptive three-stage HVR reduces the total system energy dissipation by up to 23.9% and 15.7% on average compared with the conventional static two-stage voltage regulation using off-chip and on-chip switching VRs. Compared with the three-stage static HVR, our runtime control reduces system energy by up to 17.9% and 12.2% on average. Furthermore, the proposed ML prediction offers up to 4.1% reduction of system energy.

The PMI Predictor app to enable green-by-design chemical synthesis

The development of sustainable processes for the synthesis of new clinical candidates is a priority for every pharmaceutical company. The ultimate efficiency of a molecule’s synthesis results from a combination of the sequence of steps to assemble the molecule and the efficiency of each of the steps. While multiple approaches are available to aid the development of efficient processes, far fewer methods to guide route innovation have been described. Here we present a ‘green-by-design’ approach to route selection and development, assisted by predictive analytics and historical data. To aid the selection of more efficient strategies, we created a user-friendly web application, the ‘PMI Predictor’ (accessible from https://acsgcipr-predictpmi.shinyapps.io/pmi_calculator/), to predict the probable efficiencies of proposed synthetic routes before their evaluation in the laboratory. We expect that use of this app will bring greater awareness of sustainability during the initial phase of route design and will contribute to a reduced environmental impact of pharmaceutical production. Sustainable processes for the synthesis of new clinical candidates is a priority in pharmaceutical manufacturing. This study presents a web application to predict the likely efficiencies of proposed synthetic routes before their evaluation in the laboratory.

Effect of a conformal layer on the photonic crystal for light extraction of scintillator

Abstract In this paper, we have investigated the light extraction of scintillator using by the photonic crystal consisting of an array of monolayer polystyrene nanospheres and a conformal layer. The effect of the conformal layer on the extraction efficiency was systematically analyzed. It is found that the conformal layer will strongly affect the optical properties of the photonic crystal. The coupling efficiency can be controlled by increasing mode number through varying the thickness and refractive index of the conformal layer. When the mode number increases, the multi-extraction process plays an important role in the ultimate extraction efficiency. Thus, at this situation, the extraction efficiency is more favorable for a thin scintillator. This conclusion is also applicable to other solid-state light-emitting devices.

Thin and low light-induced degradation passivated emitter and rear cells based on boron-aluminum pre-gettering

In the present work, B/Al pre-gettering technique was proposed to suppress the light-induced degradation (LID) of thin (150 μm) monocrystalline passivated emitter and rear cell (PERC). B/Al co-doping technique raised the acceptor concentration in p + doping area by more than one magnitude, contributing to the superior gettering effect with the interstitial iron concentration decreased from 9.58e10 cm−3 to a minimal value of 4.93e9 cm−3. By employing pre-gettering process in the thin PERC solar cells fabrication, LID was suppressed dramatically, with the efficiency loss improvement of 0.63% and 0.44% for the maximum degradation and ultimate degradation, respectively. Accordingly, although B/Al pre-gettering degraded the electrical performance slightly, the ultimate efficiency after LID was 0.06% higher than the samples without pre-gettering, reaching 20.68%. The present work will be helpful to deepen the understanding of B/Al gettering effect as well as suppress LID induced by iron atoms.