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The slice-shaped LaO1-xBiS2 (x = 0.07) superconducting single crystal was grown by a high-temperature flux method. The X-ray diffraction analysis and symmetric M(H) curves along the H-axis indicate no any other impurities are involved in current LaO1-xBiS2 sample. The M(T) curves show the suppression of the Tconset and Tirr with increasing magnetic field applied parallel to the c-axis which is more noteworthy than that under magnetic field perpendicular to the c-axis. The Hc2(T) curves show upward curvature near Tc, which cannot be described by the one-gap model, and similar Hc2(T) curves are observed in REO1-xFxBiS2 and captured by the two-gap model, suggesting LaO1-xBiS2 may be a two-gap superconductor. The superconducting anisotropy parameter (2.8~5.58) of LaO1-xBiS2 (x = 0.07) is estimated by different methods. The structural distortion plays an important role in the smaller superconducting anisotropy parameter of LaO1-xBiS2. The critical current density in the self-field is about 5.9 × 103 Acm−2 and 6.7 × 103 Acm−2 for H//c and H⊥c, respectively.

LaO1−xBiSSe polycrystalline samples were successfully synthesized by conventional solid-state reaction method. The effects of oxygen vacancies on the crystal structure, magnetic properties under atmospheric and high pressure, and electrical property of LaOBiSSe were investigated. Polycrystalline samples LaO1−xBiSSe with x = 0–0.1 were well indexed to the tetragonal CeOBiS2-type structure with the space group P4/nmm. With increasing oxygen vacancy content, the crystal lattice contracted significantly along the c-axis, the semiconductor behavior was suppressed, and the metal-semiconductor transition temperature decreased, which is a necessary prerequisite for superconductivity in BiCh2-based (Ch = S and Se) system. However, oxygen vacancy level introduced in this work is insufficient to further contract the crystal lattice and increase carrier density. Even though external pressure (~ 1 GPa) was applied, no superconducting transition corresponding to LaO1−xBiSSe appeared except for that of manometer Pb. The reasons for the absence of superconductivity in LaO1−xBiSSe system were discussed.

Electrochemical water splitting is convinced as one of the most promising solutions to combat the energy crisis. The exploitation of efficient hydrogen and oxygen evolution reaction (HER/OER) bifunctional electrocatalysts is undoubtedly a vital spark yet challenging for imperative green sustainable energy. Herein, through introducing a simple pH regulated redox reaction into a tractable hydrothermal procedure, a hierarchical Fe3O4@MnOx binary metal oxide core–shell nano-polyhedron was designed by evolving MnOx wrapped Fe3O4. The MnOx effectively prevents the agglomeration and surface oxidation of Fe3O4 nano-particles and increases the electrochemically active sites. Benefiting from the generous active sites and synergistic effects of Fe3O4 and MnOx, the Fe3O4@MnOx-NF nanocomposite implements efficient HER/OER bifunctional electrocatalytic performance and overall water splitting. As a result, hierarchical Fe3O4@MnOx only requires a low HER/OER overpotential of 242/188 mV to deliver 10 mA cm−2, a small Tafel slope of 116.4/77.6 mV dec−1, combining a long-term cyclability of 5 h. Impressively, by applying Fe3O4@MnOx as an independent cathode and anode, the overall water splitting cell supplies a competitive voltage of 1.64 V to achieve 10 mA cm−2 and super long cyclability of 80 h. These results reveal that this material is a promising candidate for practical water electrolysis application.

In this paper, three recently updated mechanisms were compared with experimental data, and FFCM 1.0 mechanism was chosen to perform chemical kinetic investigation of laminar burning velocity (LBV) for CH4/H2 mixtures. Results show that increasing hydrogen and pressure, LBV presents opposite results, which depends on the competition between promotion and inhibition effect at different hydrogen fractions and pressures. Based on growth rate of LBV, it is possible to determine three regimes for CH4/H2 mixtures at high pressures. When hydrogen fraction is less than 60%, the LBV of CH4/H2 mixtures at high pressures is not very sensitive to hydrogen, showing complex variation. Flame structure and radical concentration imply that the enhanced LBV by adding hydrogen, which is a combined result of chemical and thermal effects, is realized by improving the active radical production. Then, quantitative analysis of contribution value found that reaction OH+H2=H+H2O plays an important role in H production with increasing hydrogen fraction at high pressure. Through this work, it not only studied the interactive effect between CH4/H2 combustion system and varied conditions (such as pressure and hydrogen fraction), but also the influence mechanism was revealed in depth. All these have provided useful suggestions on fuel design for power machines.

Two different ruthenium content (0.5%, 1.0%) of WC - (W, Ti, Ta) C - Co cemented carbide were prepared by conventional cemented carbide production process. The results showed that adding ruthenium powder can improve the microstructure of alloy compared with excluding ruthenium carbide. The microstructure of alloy with ruthenium addition had uniform structure with less coarse grain.The addition of ruthenium could obviously promote the transverse rupture strength of WC - (W, Ti, Ta) C-Co cemented carbide, and when the adding amount was 1.0%, transverse rupture strength increased by 30%. The addition of ruthenium slightly increased the hardness of the alloy. The results of Scanning electron microscopy and spectrum analysis showed that ruthenium mainly existed in the bonding phase Co. The cutting test showed that the alloy with Ru had better wear resistance.

A novel liquid crystal beam-steerable antenna is presented. It is a conventional liquid crystal microstrip patch antenna with a bending slot in the middle of the H-plane. Owing to the introduction of the bending slot, this antenna can work at even mode and odd mode within a frequency band. To obtain the resonant frequencies and radiation characteristics of the two modes, the method of characteristic mode analysis is utilised. It indicates that the resonant frequency of even mode is lower than that of odd mode. Therefore, by choosing liquid crystal as its substrate, this antenna can alter its operating modes by varying the permittivity of liquid crystal. Furthermore, beam steering can be realised since the radiation patterns of the two modes are divergent. An antenna prototype at Ka-band has been designed, fabricated and measured. The measured results show that the maximum radiation direction can scan from −30° to −2° continuously at 26.5 GHz in the H-plane. Published version This work was supported in part by the Guangdong Provincial Key‐Field Research Program under Grant 2018B010115001 and in part by the National Natural Science Foundation of China under Grant 61831016.

A novel beam steerable antenna employing tunable high impedance surface with liquid crystal is proposed. This antenna utilizes three microstrip patches as the radiators and a tunable high impedance surface based on liquid crystal as the ground plane. In this design, liquid crystal is deliberately disposed under the two parasitic microstrip patches to reduce the effect of relatively large dielectric loss and to improve the gain and radiation efficiency of the antenna. More importantly, this work explores a tunable high impedance surface based on liquid crystal, which has advantages of simple structure and biasing scheme as compared with other tunable high impedance surfaces based on solid-state devices. It is shown that by tuning the permittivity of liquid crystal, the high impedance surface becomes to support the propagation of TE surface waves to strengthen the mutual coupling between main and parasitic microstrip patches. Consequently, the main lobe can be steered to the desired direction and the scanning range of the antenna is enlarged. To prove this novel concept, a Ka-band prototype is fabricated and tested. Measured results show that the antenna not only has acceptable gain, but also keeps a satisfactory scanning range. In addition, this antenna consumes negligible DC power and thus is a strong antenna competitor for 5G access point applications.

In this research, a newly proposed method combining Chemkin with CONVERGE was used to study the transient in-cylinder chemical reaction process in NG-diesel dual fuel engine. The selected mechanism was verified by comparing the results of CONVERGE with experimental data, and then the calibrated model of CONVERGE was used to provide boundary conditions for Chemkin. On this basis, the detailed combustion process was simulated at different natural gas substitution ratio (NGSR). The results show that, the chain branching reaction, long-chain to short-chain reaction, and reactions associated with OH radicals have significant impacts on temperature. It can also be found that the combustion of fuel shows a distinct two-stage reaction process. During the low temperature stage, both the CO and NO emissions are little. While at the high temperature stage, the CO emissions first rapidly increase and then decrease due to the consumption reaction, and the NO emissions also have a quick increase. When the NGSR is reduced, a new path for CO generation occurs at low temperature stage, resulting in minor increase (up to 0.0019 mol fraction) of CO concentration. Meanwhile, the ignition delay is reduced significantly (by 88.5%), but the increase of diesel species does not alter the formation mechanism of emissions. All these provide guidance for improving combustion and emission performance of NG-diesel dual fuel engine.

An electrically steerable parasitic array radiator in package based on liquid crystal (LC) is presented. It consists of one main and two parasitic inverted microstrip patch elements on an embedded LC layer with direct current bias. The antenna is designed to operate under the voltage mode at Ka-band. By varying the induced voltages on parasitic elements, the main beam can be steered to the desired direction. Measured results show that the pattern can be steered from –27° to +29° continuously in the H-plane at 28 GHz. The peak realized gain is 6.03 dBi with 1 dB variation within the steering range. The array achieves an 8.3% impedance bandwidth and avoids both large direct current power consumption and complicated bias scheme, making it a good antenna candidate for millimeter-wave 5G access point applications.

In the presented study, the influence of lean-burn on combustion and emission performance of diesel pilot ignition natural gas engine was investigated by using the method of computational fluid dynamics coupling with the reduced chemical kinetic model. Based on bench tested results, the computational fluid dynamics model was validated in four typical conditions, and then it was used for the simulation at different excess air coefficient. Due to the visibility of computational fluid dynamics results, the combustion medium process and emissions medium products were obtained, which then were used to explain the influence mechanism of excess air coefficient. The simulated results show that, under 50% load, the maximum cylinder pressure becomes larger and the start of combustion is advanced when the excess air coefficient increases from 1.0 to 1.5, and the maximum advance of the start of combustion reaches 9.5 °CA. Nevertheless, under 100% load, the start of combustion is advanced first and then retarded. Meanwhile, the higher the excess air coefficient is, the earlier the heat release rate shoots up. When the excess air coefficient increases from 1.2, the 10–50%, 50–90% and 10–90% combustion duration become longer. The nitrogen oxide emission increases as the excess air coefficient rises from 1.0 to 1.1 but decreases if it continues to increase. The unburned methane emission decreases first and then increases with the increase of the excess air coefficient. Nevertheless, at 1500 rpm and full load, the unburned methane emission shoots up as the excess air coefficient changes from 1.3 to 1.5 and the maximum difference of unburned methane emission reaches 3233 ppm.

By combining a simplified drift-diffusion model with the density functional theory, we quantitatively explore the contributing effects of the mobile defects in perovskites on the hysteresis of pero...

Solid-state lithium-ion batteries with high safety are the encouraging next-generation rechargeable electrochemical energy storage devices. Yet, low Li

A liquid crystal frequency tunable antenna with larger tuning range is presented. It is a traditional patch antenna, which is divided into four parts by three slots. Benefiting from the slots, this antenna can operate in TM 10 mode and antiphase TM 20 mode within the same frequency band. Through choosing the tunable material liquid crystal as the dielectric of the antenna, the resonant frequency of the two modes can be tuned at the same time. Consequently, the frequency tuning range of this antenna is doubled as compared with the traditional liquid crystal microstrip patch antenna. The simulation results show that the resonant frequency tuning range of the proposed antenna is from 21.7 GHz to 23.9 GHz (9.6%), which is two times bigger than that of traditional liquid crystal microstrip patch antenna (4.8%).

Single perovskite nanocrystals have emerged as a novel type of semiconductor nanostructure capable of emitting single photons with rich exciton species and fine energy-level structures. Here we focus on single excitons and biexcitons in single perovskite ${\mathrm{CsPbI}}_{3}$ nanocrystals to show, for the first time, how their optical properties are modulated by an external electric field at the cryogenic temperature. The electric field can cause a blueshift in the photoluminescence peak of single excitons, from which the existence of a permanent dipole moment can be deduced. Meanwhile, the fine energy-level structures of single excitons and biexcitons in a single ${\mathrm{CsPbI}}_{3}$ nanocrystal can be simultaneously eliminated, thus preparing a potent platform for the potential generation of polarization-entangled photon pairs.

Hybrid perovskites have two properties that are absent in traditional inorganic photovoltaic materials, namely, polarization and mobile ionic defects, the interaction between which may introduce new features into the materials. By using the first-principles calculations, we find that the formation energies of the vacancy defects at a tetragonal MAPbI

Highlights A pancake-like morphology solid-like eletrolyte of sodium battery with high ionic conductivity (6.60 × 10–4 S cm−1) was obtained by simple hydrothermal method. Solid-like electrolyte with pancake-like morphology showed good interface contact and excellent compatibility (stable cycle over 500 h at 0.6 mA cm−2) with sodium metal. Provides possible repulsive force explanation for the restriction of ion transport by MOF. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00628-0., Solid-state electrolyte (SSE) of the sodium-ion battery have attracted tremendous attention in the next generation energy storage materials on account of their wide electrochemical window and thermal stability. However, the high interfacial impedance, low ion transference number and complex preparation process restrict the application of SSE. Herein, inspired by the excellent sieving function and high specific surface area of red blood cells, we obtained a solid-like electrolyte (SLE) based on the combination of the pancake-like metal–organic framework (MOF) with liquid electrolyte, possessing a high ionic conductivity of 6.60 × 10–4 S cm−1, and excellent sodium metal compatibility. In addition, we investigated the ion restriction effect of MOF’s apertures size and special functional groups, and the ion transference number increased from 0.16 to 0.33. Finally, the assembled Na0.44MnO2//SLE//Na full batteries showed no obvious capacity decrease after 160 cycles. This material design of SLE in our work is an important key to obtain fast ion migration SLE for high-performance sodium-ion batteries. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00628-0.

Porous microstructure pressure sensors that are highly sensitive, reliable, low-cost, and environment-friendly have aroused wide attention in intelligent biomedical diagnostics, human&ndash, machine interactions, and soft robots. Here, an all-tissue-based piezoresistive pressure sensor with ultrahigh sensitivity and reliability based on the bottom interdigitated tissue electrode and the top bridge of a microporous tissue/carbon nanotube composite was proposed. Such pressure sensors exhibited ultrahigh sensitivity (&asymp, 1911.4 kPa&minus, 1), fast response time (&lt, 5 ms), low fatigue of over 2000 loading/unloading cycles, and robust environmental degradability. These enabled sensors can not only monitor the critical physiological signals of the human body but also realize electrothermal conversion at a specific voltage, which enhances the possibility of creating wearable thermotherapy electronics for protecting against rheumatoid arthritis and cervical spondylosis. Furthermore, the sensor successfully transmitted wireless signals to smartphones via Bluetooth, indicating its potential as reliable skin-integrated electronics. This work provides a highly feasible strategy for promoting high-performance wearable thermotherapy electronics for the next-generation artificial skin.

Biological scaffolds based stem cell delivery methods have emerged as a promising approach for tissue repair and regeneration. Here we developed a hydrogel biological scaffold from human decellularized adipose matrix (hDAM) for human adipose-derived stem cells (hASCs) delivery to accelerate chronic wound healing. The hDAM hydrogel was prepared by pepsin mediated digestion and pH controlled neutralization. The morphology, survival, proliferation and angiogenic paracrine activity of hASCs cultured in the hydrogel were assessed. Moreover, the therapeutic efficacy of the hASCs-hydrogel composite for impaired wound healing was evaluated by using a full-thickness wound model on diabetic mouse. The developed hDAM hydrogel was a thermosensitive hydrogel, presented the biochemical complexity of native extracellular matrix (ECM) and formed a porous nanofiber structure after gelation. The hydrogel can support hASCs adhesion, survival and proliferation. Compared to standard culture condition, hASCs cultured in the hydrogel exhibited enhanced paracrine activity with increased secretion of hepatocyte growth factor (HGF). In the diabetic mice model with excisional full-thickness skin wounds, mice treated with the hASCs-hydrogel composite displayed accelerated wound closure and increased neovascularization. Our results suggested that the developed hDAM hydrogel can provide a favorable microenvironment for hASCs with augmented regeneration potential to accelerate chronic wound healing. This article is protected by copyright. All rights reserved.

A novel beam scanning antenna based on liquid crystal is proposed. It is a conventional liquid crystal microstrip patch antenna with a row of shorting pins in the middle of E-plane. Owing to the introduction of shorting pins, this antenna can work at even mode and odd mode within the frequency band. The resonant frequency of even mode is lower than that of odd mode. Therefore, through choosing liquid crystal as its substrate, this antenna can alter its operation modes by varying the permittivity of liquid crystal. More importantly, beam scanning can be achieved since the radiation patterns of two modes are divergent. By using characteristic mode analysis method, an antenna model at Ka-band has been investigated. The simulation results show that the main beam can scan from -10 to broadside continuously at 28 GHz in E-plane.

Binderless cemented carbide contains very little (

The scaling relations between adsorption energies of different reaction intermediates on a variety of surfaces simplify the catalyst design, but meanwhile they make it difficult to achieve the optimal catalyst. The oxygen reduction reaction (ORR) at the cathode of fuel cells, for instance, cannot attain the ideal efficiency even with the nowadays best-performed catalysts, due to the correlation between the adsorption energies of O, OH and OOH. In this work, based on the nitrogen doped graphene, we compare the ORR reaction on active sites with different deformation while in similar structural and chemical environments. Since both the tensile strain and the adsorption of O tend to stretch and even break the N-C∗ bond, tensile strain enhances the adsorption strength of O atom while leaving that of OH and OOH approximately unchanged. In contrast, the local curvature cannot uncouple the correlation between the adsorption strength of O, OH and OOH. The results suggest that it is possible to improve the catalytic performance by tuning the structure of catalyst to be in selective resonance with adsorption of a specific intermediate, which provides a new way to design optimal catalysts.

A compact solid-state UV flame sensing system is developed and tested. We have addressed two approaches for obtaining additional six orders of long-wavelength rejection power on top of that of the built-in UV sensor based on a wide-bandgap II–VI Schottky-barrier structure. An op-amp-based amplification circuit with an average gain of 16 600 is used for signal amplification. It is demonstrated that the developed sensing system could detect a standard butane-air flame with excellent solar-blind characteristics, potentially capable for monitoring industrial boilers. Several feasible approaches were discussed for further improvement in the performance of the developed sensing system targeting its general usage in fire-safety applications.

In this study, the thermodynamics, combustion and emission characteristics of a NG-diesel dual fuel engine with varying pilot injection degree at low speed and low load were investigated by computational fluid dynamics (CFD) simulation and bench test. Based on tested in-cylinder pressure, the in-cylinder combustion process of NG-diesel dual fuel engine was quantitatively analyzed. On this basis, both the one-dimensional and three-dimensional CFD simulated models were built and then validated by tested data, which were used to analyze the combustion and emission characteristics of NG-diesel dual fuel engine. From this study, the effects of advanced pilot injection degree (APID) on the thermodynamics, combustion and emission characteristics of NG-diesel dual fuel engine were found. With the advancing of pilot injection degree, both the SOC and 50% combustion position are advanced, which leads the maximum in-cylinder pressure and heat release rate (HRR) to increase. The 10–50% combustion duration decreases slightly but the 50–90% combustion duration increases obviously. Meanwhile, both the effective expansion efficiency (EEE) and the percent of heat transfer loss increase, while their increase rates are different, which make the brake thermal efficiency (BTE) firstly increase and then decrease. The BSNOx increases largely while the BSTHC is almost unchanged with the advance of injection timing. Although more HC is generated in the early stage as the pilot injection degree is retarded, the post-combustion becomes clear which accelerates the oxidation of HC. All these have provided theoretical guidance and data support for improving the performance of NG-diesel dual fuel engine.

Eu3+-Doped CaMoO4 single-crystal fibers with concentrations from 0.01 to 1 at% have been grown by the micro-pulling-down method in an air atmosphere. The origin of the coloration of the crystals can be attributed to the charge compensations. In the air or H2 annealing process, the absorption spectra combined with XPS proved the coexistence of Eu2+ and interstitial O (Oi2-). The density functional theory was simulated to display the absorption spectra of Eu2+-doped and (Eu2+-Oi2-) co-doped CaMoO4, consistent with the experimental data. The low-temperature polarized absorption and emission spectra illustrated the charge compensations. The luminescence spectra of the Eu3+ probe were used to study the Oi2- species. Luminescence decay curves of 5D0 were measured. To the best of our knowledge, this is the first report on the growth and charge compensations of Eu3+:CaMoO4 single-crystal fibers grown by the micro-pulling-down method and the reduction phenomenon of Eu3+ to Eu2+ in an oxidizing atmosphere at high temperature in molybdates. On excitation by near ultraviolet or blue light, the molybdates could be potential hosts for white-light-emitting diodes.

The single-phase Nd1-xSrxNiO3 (x = 0–0.3) polycrystalline samples were successfully synthesized, and the structure, resistivity, and magnetic property were investigated. All of samples were well indexed to an orthorhombic structure with Pnma space group. With increasing Sr concentration x, the lattice parameter a decreased, the lattice parameter b and c increased, the obtained unit-cell volume systematically increased due to the larger ion radius of Sr2+ than Nd3+. Sr partial substitution for Nd suppressed the metal-insulator and antiferromagnetic transition until x = 0.2. However, as the Sr content increased to 0.3, some abnormal phenomena were observed. The present work shows that physical properties are correlated with the evolution of perovskite tolerance factor in Nd1-xSrxNiO3 system.

A novel approach was proposed to improve the performance of liquefied natural gas (LNG) engine. The LNG is first purified into liquefied methane and then used as engine fuel. Since the octane number of methane is higher than other compositions of natural gas, the compression ratio of liquefied methane engine (LME) can be increased for improving thermal efficiency. To verify the performance improvement potential of this approach, the experiment was conducted under varied compression ratios, and then the effects of compression ratio on in-cylinder combustion and heat-work conversion processes were analyzed. The results show that, peak heat release rate of LME is not very sensitive to compression ratio, so does the 10–90% combustion duration. With the rise of compression ratio, ignition delay period is reduced and start of combustion (SOC) is advanced. LME torque is increased by 9.5% at most while BSFC is reduced by a maximum of 10.9% under the studied conditions. NOX emissions ascend obviously with compression ratio increasing but this problem can be solved by retarding ignition timing. When other parameters are unchanged, the available compression ratio of LME can be increased to 15.6 or so without obvious knocking, which indicates great performance improvement potential for LME.

Cylinder-to-cylinder variation is unavoidable in multi-cylinder engine and has a severe impact on engine performance. To explore the cylinder-to-cylinder variation of engine under transient conditions, a hybrid method of dynamic signal measurement coupling with gas dynamics and thermodynamics processes simulation is presented to detect the parameters of engine. Then, this method is applied to an automobile engine under road test conditions, and the continuous state and performance parameters of each cylinder were obtained from cycle to cycle. On this basis, the range and influence factors of non-uniform of engine performance parameters were analyzed. The results show that, under transient conditions, the relative deviation of excess air coefficient in each cylinder is within ±5%, which is mainly affected by intake average pressure in low to medium speed operating regions but influenced by exhaust pressure wave and residual gas fraction in high-speed and high-load operating regions. There appears a symmetry relation between the non-uniform of RGF and excess air coefficient. The relative deviation of indicated mean effective pressure in each cylinder depends largely on the gas exchange performance, including excess air coefficient and residual gas fraction, and the maximum is larger than ±30%.

It is a potential approach to improve the fuel efficiency that the liquid methane gas (LMG) purified from liquefied natural gas (LNG) is fueled with the high compression ratio (CR) engine, while the actual effect is restricted by the low combustion velocity of methane. To solve this problem and further improve the LMG engine performance, the approach of hydrogen addition to LMG engine was investigated by combining experiment with numerical simulation. Based on experimental data, the computational fluid dynamics (CFD) model coupled with reduced chemical kinetic mechanism was built and calibrated, which was then employed to study the effects of different hydrogen energy fraction (HEF) on combustion, thermodynamic and emission of LMG engine. The results show that, the peak of heat release rate (HRR) increases sharply with the HEF rising and leads the maximum in-cylinder pressure to increase. The indicated thermal efficiency of LMG engine first increases and then decreases, and the maximum falls in the HEF range between 8% and 12%. Although the combustion velocity of mixture gas is obviously increased by hydrogen addition, the detonation trend still becomes larger and it increases by 10 times as HEF changes from 12% to 20%. As the HEF increases from 0 to 20%, NOx emission increases continuously, while CO and CH4 emissions decrease due to the higher combustion temperature. All these provided direction for improving LMG engine performance, and offered theoretical basis for selecting technology routes to meet emission regulations.

Understanding the different effects of CO2 dilution on the laminar premixed flame is an effective strategy for combustion control. Thus, a chemical kinetic modeling study of laminar burning velocity (LBV) for CH4/air/CO2 mixtures coupling with a detailed chemical reaction mechanism was employed under a wide range of initial conditions. After validation and comparison, the FFCM 1.0 was selected for this study. Based on the numerical prediction of LBV, the decoupling method was carried out to separate the effects of diluent CO2, including dilution, thermal and chemical effects, whose variations show that the rising initial temperature facilitates the three effects whereas the elevated pressure shows the opposite impact. In order to explain the particular process physically and chemically, the parameters analysis, sensitivity analysis and mole fraction analysis methods were conducted, and the LBV enhancement made by per unit of fuel, relevant thermal parameters and the important active radicals were proved to be responsible for the variation of the three effects, respectively. Furthermore, the domain reactions contributing to chemical effect are reactions (R32) and (R62), respectively, as temperature and pressure vary. Through this work, it not only completes the research on the effect of CO2 dilution on the laminar premixed flame, but also expands the commonly exploring initial conditions to a wide range, which provides the reference for the research on the operation condition and intensity setting of exhaust gas recirculation (EGR).

In this study, a thermodynamic analysis for the liquefied methane gas (LMG) engine with the variation of compression ratio (CR) was conducted through theoretical and experimental investigations. Firstly, the equations for thermodynamic cycle efficiency were further corrected based on the previous studies, in which the losses due to heat release rate (HRR), exhaust valve opening (EVO) timing, specific heat ratio, incomplete combustion and heat transfer were considered. Then, the sweeping test of CR was conducted on an LMG engine. On this basis, the thermodynamic cycle process was studied and various kinds of energy losses were analyzed. The results show that the improvement of indicated thermal efficiency by increasing CR mainly depends on engine operating conditions, the maximum of which occurs at high load and is close to the theoretical value (4.2 percent points). The actual cycle efficiency of LMG engine is mainly influenced by the specific heat ratio of medium gas, followed by the heat transfer loss and the effective expansion ratio (EER) loss. Compared with combustion duration, the combustion phase plays a much more important role in EER loss. All these have provided theoretical basis and direction for the improvement of actual thermal efficiency of LMG engine.

In this research, a novel structure of methanol cracking device was designed for methanol decomposition by using internal combustion (IC) engine exhaust heat. To evaluate and optimize its performance, the flow and heat transfer processes in methanol cracking device were investigated by computational fluid dynamics (CFD) simulation. The results show that methanol flow rate has important effects on the pressure loss, temperature distribution and heat flux. In general, the flow velocity and pressure in methanol cracking device are not well-proportioned and it results in the asymmetrical distributions of temperature and heat transfer coefficient. The maximum heat transfer coefficient is close to 100 W/(m2·K) while the minimum almost equals to zero because of flow stagnant zone. The average heat transfer coefficient increases as methanol flow rate rises, and it reaches to 51.63 W/(m2·K) at the methanol flow rate of 0.06 kg/s. When methanol flow rate increases from 0.03 kg/s to 0.06 kg/s, the average outlet temperature decreases from 615 K to 560 K and meets the requirements for methanol cracking reaction. All these indicate that the designed methanol cracking device can be used for IC engine exhaust heat cracking methanol, and also provide theoretical guidance for further optimizing the geometry structure.

The mechanism of fluid slip on a solid surface has been linked to surface diffusion, by which mobile adsorbed fluid molecules perform hops between adsorption sites. However, slip velocity arising from this surface hopping mechanism has been estimated to be significantly lower than that observed experimentally. In this paper, we propose a re-adsorption mechanism for fluid slip. Slip velocity predictions via this mechanism show the improved agreement with experimental measurements. Published version

The problem of steady mixed convection boundary layer flow on a cooled vertical permeable circular cylinder embedded in a fluid-saturated porous medium is studied. Here, we evaluate the flow and heat transfer characteristics numerically for various values of the governing parameters and demonstrate the existence of dual solutions beyond a critical point.

The effect of self-producing heat and external radiation on the insulating property of wire are studied experimentally in this paper. In the experiments of self-producing heat of wire, 6 types of wires are used under the situation of overloading. The results show that the effect of the temperature rise of wire on insulating property of wire is remarkable. Under the situation of having electric current wired to produce heat by itself, the insulation resistance of wire decreases and the leakage of electricity electric current enhances. Under the situation that electric current is relatively stable, the temperature becomes stable when rising to a certain value, conducting wire heat dissipating and fever heat are in an equilibrium state. In the experiments of external radiation, such as the situation of building fire, RV sheathed wires present a similar regulation to the self-producing heat experiments. The difference is that the effect of external factor (such as air flow, voltaic instability, etc.) on temperature of wire is more obvious than that on the insulation resistance of wire. When external factor makes the wire temperature decrease to a certain value, the insulation resistance value is higher than that out of the effect.

Stress corrosion cracking behaviour of ferritic stainless steels with copper and molybdenum additions in 42 wt-% boiling magnesium chloride at 143 ± 1°C has been determined. The nature of the corrosion products was analysed by X-ray photoelectron spectroscopy (XPS). XPS results show that the presence of Fe(0), Cr(0) and Mo(0) unoxidised states on the crack tips of (copper+molybdenum) addition ferritic stainless steel cannot form the stable passive film and causes the further corrosion in the chloride solution. The addition of both copper and molybdenum to 19% Cr ferritic stainless steel causes stress corrosion cracking. The susceptibility to stress corrosion cracking increases with the growth of e-copper precipitates, and the fracture mode changes from transgranular to intergranular with the increasing aging time. Stress corrosion cracking initiates from pitting of e-copper phases, then propagates to molybdenum atoms, and finally propagates to the other e-copper precipitations perpendicular to the directi...

We clarify the physical origin of the dc voltage generation in a bilayer of a conducting polymer film and a micrometer-thick magnetic insulator Y_{3}Fe_{5}O_{12} (YIG) film under ferromagnetic resonance and/or spin wave excitation conditions. The previous attributed mechanism, the inverse spin Hall effect in the polymer [Nat. Mater. 12, 622 (2013)NMAACR1476-112210.1038/nmat3634], is excluded by two control experiments. We find an in-plane temperature gradient in YIG which has the same angular dependence with the generated voltage. Both vanish when the YIG thickness is reduced to a few nanometers. Thus, we argue that the dc voltage is governed by the Seebeck effect in the polymer, where the temperature gradient is created by the nonreciprocal magnetostatic surface spin wave propagation in YIG.

We report on the first growth, spectroscopy, and visible laser operation of a single-crystal fiber (SCF) of KY3F10 (KYF) grown by the micro-pulling-down (µ-PD) method, doped with Pr3+ ions. This material has a cubic lattice, which makes it appealing for use in the industry. However, KYF crystals are considered difficult to grow with high optical quality, even with well-established methods. Nevertheless, we grew a 50-mm-long SCF of Pr:KYF, which was transparent in its inner part. We studied the spectroscopic features of it in comparison with existing literature and with samples of the same crystal grown by the Czochralski method, and we did not notice any large differences. These characterizations confirmed that is indeed possible to grow high-quality crystals of Pr:KYF by the µ-PD method. Unfortunately, the crystal proved to be more brittle than typical KYF and especially difficult to polish, leading to rough and irregular facets, as evidenced by transmission measurements. Despite these issues, we obtained continuous-wave laser operation in the orange, red, and deep red regions, using a sample carved from the SCF as active medium and an InGaN-based laser diode as pump source, though with lower performances than in existing reports on this crystal. © 2017 by the authors. Licensee MDPI, Basel, Switzerland.

We report a postgrowth aging mechanism of ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$(111) films with scanning tunneling microscopy in combination with density functional theory calculation. It is found that a monolayered structure with a squared lattice symmetry gradually aggregates from the surface steps. Theoretical calculations indicate that the van der Waals (vdW) gap not only acts as a natural reservoir for self-intercalated Bi and Te atoms, but also provides them easy diffusion pathways. Once hopping out of the gap, these defective atoms prefer to develop into a two-dimensional BiTe superstructure on the ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$(111) surface driven by positive energy gain. Considering the common nature of weak bonding between vdW layers, we expect such unusual diffusion and aggregation of the intercalated atoms may be of general importance for most kinds of vdW layered materials.

The influence of cerium addition on the isothermal oxidation behavior of 00Cr17NbTi ferritic stainless steel was studied at temperature up to 1,000 °C for 100 h in air. The results show that cerium additions can reduce the grain size of this ferritic stainless steel, improve the diffusion of chromium and decrease the critical concentration of chromium to form protective Cr2O3 layer. With the increasing of cerium addition, the oxide particles become smaller and this can increase the rupture strength and spalling resistance of oxide layers. The transport mechanism through the oxide layer is varied from metal transport outward from steel to principally oxygen transport inward with the increase of cerium content, which leads to the lower oxidation rate and the better scale adherence of 00Cr17NbTi ferritic stainless steel.

Gasoline compression ignition combustion has been regarded as a potential technology for future vehicle power source. Understanding the relationship between gasoline properties and its auto-ignition behaviors is critical to the development of this new combustion technology. Aiming at this goal, a comprehensive parametric study was conducted to investigate the influence mechanism of gasoline octane number, fuel sensitivity and equivalence ratio on the combustion behaviors of an advanced compression engine. A hybrid analysis method was proposed in the study; a reaction kinetics model coupled with a new-developed gasoline surrogate mechanism was used to trace the engine’s combustion characteristics, while a density-based global sensitivity analysis method was applied to decode the composite effect of each factor. Results demonstrate two distinct combustion modes in low temperature conditions and give separation functions in the input space of three factors (R-Squares are above 97%). The reaction kinetics analysis points out the shift of dominant reaction groups is the main reason for incomplete combustion phenomenon. Then the global sensitivity result shows octane number is the dominant factor controlling the rate of the combustion heat release under all conditions (the averaged sensitivity index exceeds 0.7); fuel sensitivity only makes a considerable effect on combustion performances under low temperature regions, with sensitivity indices of 0.2–0.3. Besides, the local sensitivity of each factor on combustion behaviors at specific points is also given to understand the influence mechanism resulted from the variations of fuel properties. This study provides a useful method for getting deeper insights into the combustion dynamics and kinetic reaction in gasoline compression ignition engines.

Knocking combustion for spark-ignition engine is related to auto-ignition of a portion of the unburned fuel-air mixture. In this investigation, the detailed chemical kinetic mechanism was engaged to numerically study the auto-ignition characteristics of hydrogen-enriched methane under engine-relevant conditions. Compared with the experimental data, the USC Mech 2.0 mechanism obtained the closest agreement, and it was adopted in the sensitivity analysis, the rate of production (ROP) analysis and the reaction pathway analysis. Results showed that at high temperature and high pressure, the ignition delay times (IDs) of CH4/H2 fuel blends reduce significantly (by two orders of magnitude at most) with rising hydrogen fraction, but the decline rate is not so obvious (within 37.3%) at low temperature. The sensitivity analysis indicated that at high temperature the reaction (R1) and reactions (R2, R3) promote each other while at low temperature only the reaction (R3) unilaterally facilitates the reaction (R12). The ROP analysis implied that the decrease of IDs of methane by hydrogen addition is realized through increasing the H, O, and OH radical production. Interestingly, the IDs for CH4/H2 fuel blends show different trends at different temperature, which decrease (by 47.5% at most) at low temperature but increase (by 132.7% at most) at high temperature as the equivalence ratio rises. The sensitivity analysis showed that the ignition kinetics for CH4/H2 fuel blends more depend on the CH4 concentration at low temperature but oxygen concentration at high temperature. This investigation not only supplements the fundamental combustion studies of CH4/H2 fuel blends in elevated pressures, but also reveals the influence mechanism of hydrogen addition and equivalence ratio on the IDs of CH4/H2 fuel blends at high pressure. More importantly, it may offer fundamental insights for the control of knocking combustion of spark-ignition (SI) engine.

The thermal protection materials enveloping hypersonic vehicles ablate. This paper develops a numerical methodology of thermochemical nonequilibrium flow and structure temperature field to study the key flow and structure parameters of a hypersonic hemispherical nose under the condition of carbon-based thermal protection material ablation. The multi-species chemical reaction model of flow field and the corresponding numerical algorithm are constructed. Oxidation and sublimation ablation process are considered in ablation model coupled with flow field solver by gas-solid interaction method. The computational results of a hemispherical nose indicate that carbon-based thermal protection material ablation has significant effects on thermochemical nonequilibrium flow. Details of the ablation flow characteristics are reported to highlight the influences of ablation on microcosmic reaction species and macroscopic flow parameters including shock wave position, pressure and temperature.

We investigate the strong coupling phenomenon between a circular cavity and a rectangular cavity based on a metal–insulator–metal (MIM) structure. Finite difference time domain method is employed to well describe the strong coupling phenomenon and the simulation results show that two splitting peaks are observed in our proposed structure, while only one resonant peak is found in MIM structure involving only a circular cavity. The coupling between the circular cavity and the rectangular cavity is manipulated by the geometry of the cavities and the symmetry of the whole structure. An asymmetric lineshape of the transmission spectrum is observed with a narrow linewidth and a deep valley, which has potential applications in plasmon sensor.

In an effort to create an environmentally-friendly flame retardant system for rigid polyisocyanurate-polyurethane foams, expandable graphite (EG) combined with aluminum hydroxide (ATH) was firstly used to effectively improve the flame retardancy. Limited oxygen index (LOI) increased to 84.2 with an incorporation of 24 phr (parts per hundred of matrix) EG and 50 phr ATH into the matrix. Based on scanning electronic microscopy observation and thermogravimetric analysis, it was speculated that ATH could effectively induce “villi” like particles on the surface of EG, which made the intumescent char denser. The compact char layer could effectively impede the bubbles and heat transport. ATH and EG accelerated the initial degradation and fluffy char was quickly generated on the surface, which results in the slowed down degradation products of the composite and the delayed diffusion of volatile combustible fragments to flame zone.