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Gasoline compression ignition combustion has demonstrated the potential of getting high fuel efficiency. In this work, two engine models are established in the commercial software Converge 2.3 based on the experimental results of an optical engine and a modified metal engine. The effect mechanism of mixture stratification and the influence of compound control strategy on gasoline compression ignition (GCI) combustion and soot emissions under high load condition are investigated. Results show that synergistic effect of physics and chemistry is the dominant control mechanism of GCI combustion. Stronger mixture stratification can effectively reduce the maximum pressure rise rate (MPRR) and improve the indicated thermal efficiency (ITE) and emissions; applying high EGR will significantly reduce OH radical in the cylinder and subsequently weaken the soot oxidation process, resulting in high soot emission; under the premise of reasonable NOx emission and MPRR, the soot emission can be effectively reduced with a proper advanced main injection timing. The effect of temperature on the soot oxidation process is the primary mechanism for the ultimate soot emission at different main injection timings; properly increasing the interval between the pre‐ and main injection can reduce NOx and soot emissions under the premise of ensuring that the MPRR is within the upper limit. However, the effect is not significant because of the small proportion of preinjection fuel.

As a promising energy conversion technology, transient thermoelectric device has potential applications in temperature control and refrigeration. The performance is sensitive to the applied current pulse. However, the conventional current pulse is limited to regular current shapes, which cannot achieve the best super-cooling performance. There exist strong coupling effects between the parameters of pulse shape, pulse amplitude, and pulse width. Simultaneous optimization of all the variables involved in a current pulse is a prerequisite to further improve the super-cooling. To bridge this gap, a constraint-free current pulse design concept was proposed in this study, which was successfully validated by a multi-objective optimization method. The results show that, the effective cooling regime and temperature overshoot both exhibit excellent features after optimization. Compared with the current t0 (mostly employed in previous studies), the betterments are improved by 88.33% and 92.13% for the effective cooling regime and the temperature overshoot, respectively. The underlying physics reveals that, the appropriate mediation between Peltier cooling, Joule heating, and Fourier conduction effects by a wave-like irregular current pulse is responsible for the improvement. The Pareto-optimal front found in the optimized current shape is beneficial for scientists and engineers to make an appropriate decision towards specific practical application.

The effects of Sc and Zr element on the recrystallization behavior and microstructure evolution of Al-Mg alloy had been researched in this paper, and meanwhile, the microstructure and mechanical properties of the friction stir welding joints were also analyzed. The results show that the recrystallization and grain growth behavior of Al-Mg-Sc-Zr alloy can be inhibited effectively by microalloying with Sc and Zr. Compared with Al-Mg and Al-Mg-Zr alloys, the recrystallization start temperature and finish temperature of Al-Mg-Sc-Zr alloy increase significantly, and the strength of alloy sheet which subjected to stabilizing annealing is increased by more than 50MPa. Moreover, the recrystallization softening effect of the welded joints microstructure, which caused by the welding temperature field and welding heat input, can be weaken by microalloying with Sc and Zr, the width of recrystallization zone is reduced, the microstructure and properties of the welded joints are improved. The friction stir welding coefficients of Al-Mg-Sc-Zr alloy increases to 86.9%.

Thermal deformation of space-borne radar antenna caused by dramatic changes in orbit thermal environment has a serious effect on image qualities. In this paper, the NX TMG module was used to simulate the orbit thermal environment of the antenna, and a thermal control design was proposed. The thermal control structure consists of three layers; the top is a radiator with high emissivity surface, the middle is a multi-layer insulation, and the bottom is a highly reflective layer. The simulation results show that the thermal design could reduce the temperature gradient from 238.1 to 31.4 °C effectively.

A solution of Al(NO3)3.9H2O and NaOH was used to perform Mg-Al LDH plugging treatment on the LA103Z magnesium-lithium alloy micro-arc oxidation ceramic layer. The effect of treatment temperature on...

Octane sensitivity (OS), as one of the fuel anti-knock quality indexes, is critical with respect to the effective design of next-generation spark ignition (SI) engines. This simulation study focuses on the effects of OS on knock behavior as a function of spark timing (ST) and compression ratio (CR) under boosted high load condition. Eight fuels with identical Research Octane Number (RON) and varying OS were selected to specify the relationship between OS and fuel-specific properties, including a primary reference fuel (PRF), Ethanol Reference Fuels (ERFs), Toluene Reference Fuels (TRFs). It was found that increasing OS to decrease end-gas reactivity is conditional. The end-gas reactivity becomes less sensitive to OS with advancing ST. Analysis for the relationship between OS and fuel-specific properties illustrate that fuel-specific variations beyond OS play an important role in knock tendency when increasing CR, where OS value is insufficient to describe the fuel anti-knock performance. ERF yields better knock resistance than the corresponding OS TRF at high CR conditions. The cause for this behavior is that the decrease in the autoignition temperature moves the end-gas of high OS fuel into a long-ignition-delay region. Comparable chemical and charge cooling effects are effective to retard auto-ignition more dramatically for ERFs.

Developing highly effective photocatalytic hydrogen production in graphitic carbon nitride (g-C3N4) is still a challenging issue. Herein, for the first time, the structural engineering of g-C3N4 nanosheets with Co atoms bonded with compositional N (Co–Nx) is demonstrated to address this challenge. The structure of Co–Nx is formed through the substitution of C atoms in g-C3N4 with Co atoms, which is evidenced by X-ray absorption fine structure spectroscopy (XAFS). Therefore, by adjusting the band structure and electronic structure of g-C3N4, the separation and transfer efficiencies of photo-generated charges are significantly improved. Consequently, the catalysts exhibit a superior visible light photocatalytic hydrogen production rate (5394.35 μmol g−1 h−1) and the apparent quantum efficiency (AQE) of 1.92% at 427 nm.

Electrochemical water splitting is widely studied in the hope of solving environmental deterioration and energy shortage. The design of inexpensive metal catalysts exhibiting desired catalytic performance and durable stability for efficient oxygen evolution is the pursuit of sustainable and clean energy fields. Herein, a three-dimensional (3D) flower-like NiSe2 primary structure, modified with highly dispersed CuSe2 nanoclusters as the secondary structure, is obtained by regulating the growth trend of the nanosheets. Benefiting from the metallicity of selenides and the formation of a heterogeneous interface, NiSe2@CuSe2/NF shows comparable performance toward the oxygen evolution reaction (OER) in an alkaline environment. Upon regulating the synthesis conditions, the catalyst exhibits its optimal performance with ultralow overpotential for the OER when the Ni/Cu molar ratio is 1 : 0.2 and the hydrothermal temperature and hydrothermal time are 200 °C and 6 h, respectively. It provides a current density of 10 mA cm−2 when a potential of 201 mV is applied without iR compensation. In this work, the hierarchical heterostructures of NiSe2 and CuSe2 are synthesized, which exhibit high electrocatalytic activity towards the oxygen evolution reaction and provides a new possibility for the extensive application of copper-based compounds in advanced energy fields.

Trimethoxyoctadecylsilane (OTMS) was successfully used to decorate mesoporous silica with a self-assembly method to enhance the relative gas selectivity. A quartz crystal microbalance was employed to measure the gas-sensing properties. The content of OTMS was the crucial factor that greatly affected the adsorption capacity (q) of silica, which could be converted to relative selectivity (S) to study the sensing mechanism. With increasing OTMS content, q was far higher for small-molecule gases compared to volatile organic compounds (VOCs), which could be explained by the polarity of the bonding objects, and S reached a maximum value of 45.71%. When exposed to VOCs, S was always greater than 0 among the three alcohols. The sensing mechanisms of undecorated silica and OTMS-decorated silica were quite different; the three-state mechanism was proposed to explain the sensing mechanism of OTMS-decorated silica. When exposed to small-molecule gases, the atoms that bonded with carbon atoms on OTMS greatly influenced q. With increasing OTMS content, the bonding energy of OTMS with CO2 was far less than that with other molecules, resulting in a relative selectivity as high as 38.69%. Furthermore, macroperformance and microproperties were combined in three-dimensional coordinates, which could be applied to predict the sensing performance of silica.

Boron-lined gas detectors are prospective alternatives to helium-3-based neutron detectors. For boron-lined multi-wire proportional chamber (MWPC) with neutron grazing incident angle geometry, high neutron detection efficiency and 3D position sensitive can be realized. In this paper, a multi-layer boron-lined MWPC was studied. Influences of the boron coating thickness, coating layer numbers and neutron incident angle on the neutron detection efficiency were studied and optimized with Geant4 simulation. The output signal properties including induced signal width on the readout plane, the time resolution and gas gain uniformity of the detector were studied with Garfield program. The results show that the neutron detection efficiency can be significantly increased by using neutron grazing incident geometry. For 4 layers of 10B4C with thickness of 1 µm, the neutron detection efficiency can reach to 54.56%, 49.17% and 44.36% when neutron incident angle is 6°, 8° and 10°, respectively. For detector with curved geometry, the gas gain is nonuniform among the anode wires, and using separate high voltage for each anode wire or wires group can effectively reduce the nonuniform of the gas gain. The results of this work can be used to optimize the detector design.

High-pressure direct-injection (HPDI) natural gas engines continue to draw much attention for the highly efficient and clean combustion process compared to traditional diesel engines. However, the ...

Redlich-Kwong-Peng-Robinson (RK-PR) was developed in recent years as a promising generalized cubic equation of state (EoS) to allow for a good representation of fluids with different critical compressibility factors (Zc), but it cannot be mathematically applied to high Zc fluid such as H2 and CO, thus limiting its application on engine problems. In this work, the Zc ratio was modeled as a function of Zc to extend the calculable range of RK-PR and to achieve higher accuracy for various n-alkanes, liquid oxygen and nitrogen. The thermodynamic and transport properties framework based on RK-PR show superiority over those of SRK and PR for typical IC engine fuels and spray mixtures. In addition, the high-fidelity simulations of n-dodecane spray were performed to investigate qualitatively and quantitatively the effects of EoS and thermodynamic conditions on trans/supercritical spray behavior and characteristics, emphasizing the necessity of applying an accurate EoS for high fidelity spray simulations.

In order to improve the corrosion resistance of magnesium-lithium (Mg-Li) alloy, a micro-arc oxidation (MAO) ceramic layer was first prepared on LA103Z Mg-Li alloy, and then the MAO coating on LA10...

Ge films were prepared at different deposition temperatures and ion source bias voltage using the electron beam evaporation. The infrared refractive index was obtained by spectral inversion. Results show that the refractive index becomes larger as the deposition temperature increases. The maximum refractive index at the wavelength of 4 000 nm is 4.274 with the deposition temperatures of 210 °C. The refractive index of film decreases first and then increases as the bias voltage increases. When the ion source bias voltage is 120 V, the refractive index of the film is the smallest. The difference in extinction coefficient of Ge films prepared by different process parameters is small.

The micro-arc oxidization (MAO) ceramic layer on an LA103Z Mg-Li alloy substrate was treated with a hydrothermal treatment at 90 °C for various times. The effect of the hydrothermal treatment time on the microstructure and corrosion behavior of MAO/LDH composite coatings in 3.5 wt.% NaCl solution was investigated, and the mechanism of hydrothermal film formation and corrosion was discussed. The results show that MgO on the surface of the MAO ceramic coating was partially dissolved during the hydrothermal treatment, and the released Mg2+ ions combined with OH− ions in the hydrothermal solution to form Mg(OH)2 nanosheets, which were deposited on the surface of the ceramic coating and its pores. The hydrogen evolution rates of the MAO/LDH composite coatings rank as MAO/LDH-24 h

The Micro-Encapsulated Phase Change Materials (MEPCMs) with the melting point temperature of 28 °C was used as an energy storage medium to control the thermal behaviour of a heat exchanger. The NEPCM particles were mixed with Expanded Graphite (EG) microparticles to improve the heat transfer rate in the heat exchanger. The MEPCM particles are made of paraffin cores with a particle average size of 45 μm. The paraffin core of the particles can undergo a solid/liquid phase change and store a tremendous amount of thermal energy due to the latent heat of phase change. The heat exchanger is a copper pipe radiator with aluminium fins confined in either a bed of MEPCMs or a composite mixture of MEPCMs + Expanded Graphite (EG) microparticles. The thermophysical properties of MEPCMs and MEPCM + EG were measured. The outcomes show 132% enhancement in thermal conductivity and a 28% decrease in the sensible specific heat of the MEPCM + EG composite with the weight ratio of 70% MEPCM and 30% EG compared to pure MEPCM. The charging and discharging behaviour of heat exchanger for various flow rates and two cases of MEPCM and MEPCM + EG were studied experimentally. The results reveal that using EG notably enhances the heat transfer and capability of the heat exchanger during the charging and discharging process. Using MEPCM + EG reduces the temperature drop at the heat exchanger outlet about 15 °C compared to the case of pure MEPCM.

During acidizing process in a gas field, leakage of 80SS anti-sulfur tubing occurred.The main reasons for failure of the tubing have been investigated based on analysis techniques of chemical composition analysis,Optical Microscopy (OM), Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) , X-ray Diffraction (XRD) and mechanical test. The results show that composition and mechanical properties of the tubing were all in accordance with the corresponding requirements of API Spec 5CT standards. Furthermore,leakage of tubing from inner wall was caused by combined impacts of acid corrosion, H2S corrosion, low PH value, high temperature and a certain pressure. Meanwhile, Low concentration of corrosion inhibitor was also one of the factors of corrosion perforation.

The DD6 nickel-based superalloy exhibits remarkably high temperature properties; therefore, it is employed as a crucial structural material in the aviation industry. Nevertheless, this material is difficult to process. Ultrasonic-assisted drilling (UAD) combines the characteristics of vibration processing technology and conventional drilling technology, significantly improving the machinability of difficult-to-machine materials. Thus, UAD experiments were performed on micro-hole machining of DD6 superalloy in this study. The effects of amplitude, frequency, spindle speed, and feed rate on thrust force, machining quality, and drill bit wear were studied; thereafter, a comparison was drawn between these effects and those of conventional drilling (CD). The experimental results reveal that the thrust force decreases with an increase in spindle speed or a decrease in feed rate for both UAD and CD. UAD can significantly reduce the thrust force. With the same processing parameters, the greater the amplitude, the greater the reduction of the thrust force. The surface roughness of the hole wall produced by UAD is lower than that of CD. Compared with CD, UAD reduces the burr height, improves machining accuracy, and reduces drill bit wear.

To improve the corrosion resistance of the ceramic layer prepared by micro-arc oxidation (MAO) on magnesium alloy, a hydrophobic Mg-Al-Co layered double hydroxide (LDH) coating was fabricated on MA...

A new thin-walled honeycomb structure for Li-ion battery packaging is designed and optimized in this study. Compared with other battery packaging structures, the designed honeycomb structure described here uses a grid to reinforce its strength. At the same time, the weight is reduced to improve the energy density of the entire package. Moreover, the new thin-walled structure can better protect the internal battery and improve the safety of an electric vehicle (EV). A space mapping (SM) algorithm is used to efficiently optimize the thin-walled honeycomb structure due to the expensive computational cost of each evaluation of a fine FE model. Compared with other SM algorithms, the coarse model of SM is based on a pseudo-plane-strain model. The result shows that the magnitude of stress and the distribution of stress are significantly improved compared with the initial structure. Moreover, the computational cost of optimization for the problem is also decreased significantly due to importing the coarse model.

All-inorganic lead halide perovskites are ideal platforms to investigate the fundamental physics of the light–matter interactions, due to their strong oscillator strength at room temperature and va...

The microstructure of the catalyst material is one of the most important factors affecting the photocatalytic performance. In this study, inverse opal structure strontium titanate (SrTiO3, STO) materials with different pore sizes (from 75 to 123 nm) were prepared, and employed as photocatalysts in the degradation of rhodamine B (RhB) dye. The results suggest that the highest photodegradation rate of the inverse opal structure photocatalyst reaches to 88.03%, which is greater than that of the non-inverse opal structure (50.42%) due to its complex three-dimensional porous microstructure. The effect of the pore size of the inverse opal structure STO on the photocatalytic properties was investigated. As the pore size of the inverse opal microstructure decreases, the photocatalytic degradation rate increases regularly, attributing to effective capture of light with decreasing of pore size. The photocatalytic degradation mechanism of inverse opal structure with different pore sizes is discussed in this work.

The research on advanced functional polymers is being driven by the fast-growing demand for new functional materials that can be used in revolutionary technologies. Polymers can be endowed with functions by using certain special preparation methods or by introducing functional groups or fillers into materials. These functions are either intrinsically possessed by materials or actuated by external stimuli. In this review, we present an overview of the recent developments made in the research hotspots of functional polymers, encompassing polymerization methodologies, luminescent polymers, photovoltaic polymers, other electronic and optical polymers (including low-k polyimides and second-order nonlinear optical polymers), biorelated polymers (particularly those for biomedical applications), supramolecular polymers, stimuli-responsive polymers, shape-memory polymers, separation polymer membranes, energy storage polymers, and covalent organic framework polymers. The concepts, design strategies at the molecular level, preparation methods, classifications, properties, potential applications, and recent progress made in such polymers are summarized. Challenges and future perspectives of each type of functional polymers are also addressed, including research efforts regarding the design and fabrication of functional polymers for serving the increasing demand for new materials.

A simple, in situ, and one-pot hydrothermal strategy was applied for the successful manufacturing of heterostructured 2D/2D BiOCl/g-C3N4 photocatalysts, and outstanding photodegradation of Rhodamine B in the condition of visible-light irradiation over the composites emerged. The investigation of various BiOCl/g-C3N4 ratios influencing the activity implied that the optimized B2C1 (mole ratio of BiOCl/g-C3N4 with 2:1) exhibited the higher degradation efficiency than that of the rest of the composites, even higher than that of pure BiOCl and pure g-C3N4, which yielded over 90% in the initial 30 min and reached almost 100% during the whole 70 min irradiation process. Kinds of characterizations demonstrated that the enhancement of photodegradation performance was caused by the intimate contact between BiOCl and g-C3N4 to form the heterostructure, which could benefit the generation of abundant visible-light photoinduced carriers and help enhance their separation and then promote their transportation to the surface.

The design and fabrication of efficient inexpensive electrocatalysts are critical for electrochemical energy conversion technologies. Control and understanding of electronic configuration at the ac...

In conventional electrospinning (e-spinning) process, the curing mechanism can be attributed to the volatilization of solvent or the melt cooling of the jets, which were merely physical processes. To develop novel e-spinning curing mechanism, we propose a conjugate e-spinning one, in which the e-spinning precursors, solution A containing some active monomers, oxidant and solution B containing reductant, are loaded into two different syringes connected with opposite high voltage supplier, respectively. The opposite charged jets attract each other and then meet when flying from spinneret tip to collector. The redox reaction occurs when two jets meet and radicals are produced in situ which can initiate polymerization of active monomers. Then the conjugate jets solidify into fibers under reaction curing mechanism. The new method may give a new approach to produce composite functional fibers.

This paper numerically investigated the chemical kinetic process of a reacting n-dodecane spray flame under a compression ignition combustion condition. To achieve this target, a data processing me...

Generally, photonic bandgap (PBG) would shift when photonic crystals (PCs) are exposed to different surrounding conditions. Thus, the shift of PBG could be used to study the adsorption behavior of gas on the surface of PCs. However, the amount of PBG shift only contains finite information about analyte which could cause the change of structural parameters of PCs. In this paper, we have deduced the volume fraction of adsorption vapor (Vvap) in silica PCs to quantitatively explain the effect of target gases on adsorption behavior according to Replacing model based on our previous research. In this work, the effect of volume fraction of void in silica PCs and types of target gases on gas adsorption behavior has been discussed by using Vvap.

Spray impingement has aroused more and more interests in recent years with the increase of injection pressure in internal combustion engines. In this paper, the near wall combustion after fuel spray impingement is studied based on an updated film development model and experiment in constant volume vessel. Relationship between spray injection and flame development under different ambient temperature is analyzed as well as the near wall distribution of combustion products. In the first part, a mathematical model that considered the effects of surface tension on spray impingement is built for better prediction of film development. Reasonable results are obtained at room temperature spray impingement case, and the split distribution of film depth is also well captured. In the second part, flame development in the near wall region is investigated based on the proposed numerical model and experiments. The result shows that the flame becomes circumferentially nonuniformed at lower ambient temperature (723 K) and the evolution of downstream flame become sensitive to the wall temperature. At lower ambient temperature (723 K), increasing wall temperature could enlarge the high temperature zone, which is helpful to accelerate the film evaporation and soot oxidation. At higher ambient temperature condition, the spray impact angle should be reduced to create more concentrated combustion (stronger stratification), which could improve the combustion efficiency in the near wall region.

Highly active, earth-abundant, and stable electrocatalysts are indispensable for overall water splitting. In this work, hierarchical dendrite-like Co0.75Ni0.25 alloy prepared by a simple hydrothermal reduction route can serve as a high-performance catalyst for hydrogen evolution reaction. The synergistic effect from Co and Ni atoms optimizes the catalytic behavior of their alloy, and the hierarchical dendrite structure enlarges the contact area with the electrolyte, exposing more active sites. Based on the dendrite-like Co0.75Ni0.25 alloy, we further fabricate a core-shell architecture with the conductive N-doped carbon shell coated dendrite-like CoNi/CoNiO2 nanocomposites via a calcination process at 600 ℃ (CoNi/CoNiO2@NC-600). The dendrite-like CoNi/CoNiO2@NC-600 displays significantly improved activity of oxygen evolution reaction due to large active surface area, high conductivity, and the continuous electron transfer among metal, metal oxide, and N-doped carbon. Furthermore, the dendrite-like Co0.75Ni0.25 alloy and CoNi/CoNiO2@NC-600 are assembled into a water splitting electrolyzer with a low voltage of 1.51 V to drive a current density of 10 mA cm−2.

The purpose of this study is to obtain a margin of safety for material and process parameters in sheet metal forming. Commonly applied forming criteria are difficult to comprehensively evaluate the forming quality directly. Therefore, an image-driven criterion is suggested for uncertainty parameter identification of sheet metal forming. In this way, more useful characteristics, material flow, and distributions of safe and crack regions, can be considered. Moreover, to improve the efficiency for obtaining sufficient statistics of Approximate Bayesian Computation (ABC), a manifold learning-assisted ABC uncertainty inverse framework is proposed. Based on the framework, the design parameters of two sheet metal forming problems, an air conditioning cover and an engine inner hood, are identified.

Purpose Currently, lubrication analysis of piston ring is generally done under engine rated operating condition. However, the engine (such as the vehicle engine) does not always operate in rated operating condition, and its operating condition changes frequently in actual use. In addition, the lubrication status of piston ring is generally assumed as the flooded lubrication or a certain form of poor lubrication in most of the lubrication analysis. Design/methodology/approach In this paper, based on the equations about the flow rate of lubricating oil and the variation of control volume, the flow model of lubricating oil in the piston ring-cylinder liner conjunction is established. The lubrication analysis of piston ring for a four-stroke engine under different engine operating conditions is done, in which the lubricating oil at the inlet of piston ring is considered as the lubricating oil attached on the relevant location of cylinder wall after the piston ring moves over at the previous stroke. Findings There is remarkable difference for the lubrication characteristics of the piston ring under different engine operating conditions. The worst lubrication status of piston ring may not take place under engine rated operating condition. Originality/value In this paper, based on the measured engine cylinder pressure, the lubrication analysis of piston ring for a four-stroke engine under different engine operating conditions is done in which the lubricating oil supply condition at the inlet of piston ring is considered. The results of this paper are helpful for the design and research of engine piston ring-cylinder liner conjunction.

Guided by oxidation-reduction reactions, we in-situ grew MnO2 coating on three novel 3D structured foams, Ni, Fe and Fe75Ni25 (written as MN, MF and MFN) for diesel soot elimination. Systematic characterizations including SEM, HRSTEM-EDS, XRD, Raman spectroscopy, FT-IR, XPS, H2-TPR and soot-TPR revealed that the substrates affected greatly the morphology, content, structure, surface and redox ability of MnO2 coatings. MnO2 of MN was thin nanoflake, but became thicker on MF and partly turned into nanowire on MFN. The contents of K stabilizer in MnO2 coatings are in proportion to the concentrations of Fe3+ and Ni3+ dopants. MF showed the best pristine activity owing to abundant surface oxygen species, bulk K+, and high-valence manganese. But MF deactivated seriously in 6% H2O (T50 increased by ~30 °C) because of excessive hydrophily and K+ loss. MN and MFN displayed splendid reusability; especially 90% of soot loaded on MFN could be removed within 1500s at 420 °C in a simulated diesel exhaust. Ni3+ could effectively stabilize K+ and tune surface hydrophily. The used catalysts displayed good adherence against exfoliation. Further, the excellent heat conductivity of metal foams and low coating weights would eliminate hot spots from soot combustion.

Currently used turbulent lubrication model that considers the effects of surface roughness can only handle the isotropic rough surfaces and cannot handle the rough surfaces with directional properties. In this paper, based on the stochastic method and the Ng-Pan turbulent model, the stochastic turbulent lubrication models of one-dimensional longitudinal rough surface, one-dimensional transverse rough surface and isotropic rough surface are derived. The turbulent lubrication performance of a journal bearing with isotropic rough surface is calculated by the stochastic turbulent lubrication model. The results are in good agreement with the corresponding experimental data. Moreover, the proposed stochastic turbulent lubrication models are also suitable for parts of friction pairs such as journal bearing and thrust bearing.

GaN nano/microwires, due to their large surface-to-volume ratio and the reduced dimensionality, have been widely used in high-performance ultraviolet (UV) photodetectors (PDs). However, there has been a fundamental trade-off between the photocurrent gain and the speeds of PDs, which have limited their practical applications. In this work, highly ordered GaN microwire array based Schottky UV PDs have been fabricated, and optimizing Si doping concentrations can entirely improve the performances of the devices. The results show that output photocurrent increases monotonously as increasing doping concentration, while the dark current experiences a decrease followed by an increase, resulting in an optimized value under a certain doping concentration. At doping concentration of 1 × 1018 cm–3 with 2.2 mW cm–2 illuminating intensity, the sensitivity, responsivity, and detectivity of the devices are greatly enhanced by 1.84 × 104%, 163%, and 2103%, respectively. Meanwhile, the time-dependent response in Si-doped d...

Defects in layered semiconductors cause large variation of electric and catalysis properties, and exploiting defect-involved reaction can deeply excavate unearthed characteristics with significant performances. Mo-terminated defects of MoS2 spontaneously guide the oriented growths of ultrasmall Au nanocrystals on specific sites of liquid-exfoliated (LE) nanosheets, which are experimentally and theoretically performed with programmable heterostructures. The conjugated construction of Au plasmonics and MoS2 semiconductors is manipulated with the aim of the optimal synergistic activity. Additionally, with photonic irradiation, hot electrons excited from attached plasmonic nanostructures are injected into MoS2 semiconductors, which remarkably increases the carrier density of catalyst to match the energy level of hydrogen evolution reaction (HER). Obeying the principle of proximity, localized MoS2 defect-adjacent Au plasmonics exhibit a more valid pathway, transferring hot electrons from donators to receptors of catalytic sites, in comparison to planar Au decoration. Meanwhile, Au nanostructures located at basal planes are essential for accelerated electron transport rates between catalysts and electrodes, and high stabilities in plasmonic-motivated electrocatalytic performances are guaranteed. The dual function of location-discriminated Au nanostructures accounts for superior electrocatalytic HER performances with photonic excitation, which imparts high inspiration in expanded heterostructures and integrated plasmonic techniques for catalysis and devices.

Micro/nanowire light-emitting diodes have inspired considerable research interests due to their wide range of potential applications, such as in micro/nanoscale display, optical communication and optical logics. To realize a single wire light-emitting diode, however, it is usually faced with low-efficiency or wavelength uncontrollable. Herein, we report on an individual coaxial core/shell InGaN/GaN microwire light-emitting diode with tunable dual-/single-wavelength light emission, which can be feasibly realized by controlling growth rate of microwires using MOCVD. The unique cross-sectional morphologies of synthesized microwires can simplify the device fabrication process and are in favor of vertical current injection and spreading simultaneously. Thus, the microwire light-emitting diodes show advantages at the suppression of efficiency droop under large current injection, with a drop ratio of 19.6%, as increasing the injection current from 2.4 A cm−2 to 92.6 A cm−2. This study proposes a core/shell multiple quantum wells microwire structure to fabricate micro light-emitting diodes which may act as a reliable light source for micro/nanoscale integrated photonic systems.

Developing the cost-effective catalyst based on earth-abundant materials is a crucial demand for water oxidation. Doping heteroatom into catalysts is regarded as an effective strategy to regulate electronic configuration and improve the catalytic performance of water oxidation. In this work, N-doped CoS2 on carbon cloth is fabricated by one-step synthesis, in which thiourea acts as both sulfur and nitrogen sources. The N-doped cobalt disulfide shows superior catalytic activity for oxygen evolution, with a low overpotential of 240 mV for 10 mA cm−2, small Tafel slope (56 mV dec−1) and high turnover frequency due to the modification with electronic structure after incorporation of N atom. Moreover, the incorporation of N atom provides a distinctive perspective of doping other heteroatom into the material for modifying the electrochemical properties.

The quantum-dot light-emitting diodes (QLEDs) that emit near-infrared (NIR) light may be important optoelectronic synaptic devices for the realization of artificial neural networks with complete optoelectronic integration. To improve the performance of NIR QLEDs, we take advantage of their low-energy light emission to explore the use of poly(3-hexylthiophene) (P3HT) as the hole transport layer (HTL). P3HT has one of the highest hole mobilities among organic semiconductors and essentially does not absorb NIR light. The usage of P3HT as the HTL indeed significantly mitigates the imbalance of carrier injection in NIR QLEDs. With the additional incorporation of an interlayer of poly [9,9-bis(3ʹ-( N , N -dimethylamino)propyl)-2,7-flourene]- alt -2,7-(9,9-dioctylfluorene)], P3HT obviously improves the performance of NIR QLEDs. As electroluminescent synaptic devices, these NIR QLEDs exhibit important synaptic functionalities such as short- and long-term plasticity, and may be employed for image recognition.

The characteristic of an all-optical electromagnetically induced transparency (EIT) analogue generated on GaAs substrate in terahertz (THz) region has been investigated. By increasing power of pump laser, a phenomena of EIT analogue emerged. It was found that the resonance frequency as well as the time delay can be dynamic tuned by controlling the power of pump laser, which displayed a blue shift by increasing the conductivity. Furthermore, the coupled Lorentz oscillator model has been used to analyze the physical mechanism of photo-generated EIT analogue as well. This approach may provide a reference for the design of the rapid tuning device.

The role of chemical mechanisms in studying the combustion phenomenon is very important. These mechanisms, if formulated properly, can make a numerical investigation more accurate and time-saving. In this study, a multi-component surrogate has been presented after integrating two previous mechanisms to study the combustion chemical kinetics. The mechanism contains a total of six components, 168 species and 680 reactions and has been validated extensively. The validations have been carried out for individual and mixture of components over a wide range of temperatures and pressures. The mechanism showed a good overall agreement with the experimental data. In order to do an application-based kinetic study, this mechanism was later used to study the combustion characteristics of Reactivity Controlled Compression Ignition (RCCI), which is a low-temperature and dual fuel combustion concept. The combustion characteristics have then been investigated considering the impact of single and multi-component surrogates on chemical and physical properties. First, only chemical properties and then physical properties have been changed followed by a change in both properties by a multi-component mechanism. The in-cylinder pressure and heat release rates have been captured well by multi-component surrogate fuel representing both physical and chemical properties of multi-component surrogate. The NOx and soot emissions have been predicted well by using a combination of physical and chemical properties of multi-component and single component surrogates for diesel and gasoline, respectively. The chemical kinetics analysis was performed at points of five percent (CA5) and fifty percent (CA50) of total heat release using sensitivity and consumption reaction pathways analyses. These analyses showed an overall more production of OH, CH2O and CO2 in multi-component surrogate fuel which enhanced the overall heat release rate. Toluene and cyclohexane were observed to inhibit the reactivity of multi-component surrogate fuel. They, on the other hand, also control the low-temperature heat release rates and enhance the high-temperature heat release rates.

The pyramid–prism interface in “point-seed” rapidly grown DKDP (KDxH2–xPO4) crystals affects the quality of tripler-cut samples used in inertial confinement fusion devices. In this study, a cuboid DKDP crystal without a pyramidal sector was rapidly grown. The quality of the cuboid DKDP crystal was evaluated by measuring the deuterium homogeneity, crystalline quality, transmission spectrum, and laser-induced damage performance. The total number N of tripler-cut samples that can be obtained from the cuboid DKDP crystal is easily calculated. The size of the tripler-cut sample is approximately equal to the cross-section of this cuboid DKDP crystal. Moreover, as this cuboid DKDP crystal has a regular shape, calculating the mass of the crystal and accurately controlling the supersaturation of the solution during growth is easy. The successful crystal growth using this proposed approach establishes the possibility of growing large-aperture cuboid DKDP crystals. Currently, research on the rapid growth of a cuboid...