A Novel Model for the Prediction of Liquid Film Thickness Distribution in Pipe Gas-Liquid Flows

A model is proposed for liquid film profile prediction in gas-liquid two-phase flow,which is able to provide the film thickness along the circumferential direction and the pressure gradient in the flow direction.A two-fluid model is used to calculate both gas and liquid phases’flow characteristics.The secondary flow occurring in the gas phase is taken into account and a sailing boat mechanism is introduced.Moreover,energy conservation is applied for obtaining the liquid film thickness distribution along the circumference.Liquid film thickness distribution is calculated accordingly for different cases;its values are compared with other models and available experimental data.As a result,the newly proposed model is tested and good performances are demonstrated.The liquid film thickness distribution in small pipes and inclined pipes is also studied,and regime transition is revealed by liquid film profile evolution.The observed inflection point demonstrates that the liquid film thickness decreases steeply along the circumference,when the circle angle ranges between 30°and 50°for gas-liquid stratified flow with small superficial velocities.

Ultrathin Limit on the Anisotropic Superconductivity of Single-Layered Cuprate Films

Exploring dimensionality effects on cuprates is important for understanding the nature of high-temperature superconductivity.By atomically layer-by-layer growth with oxide molecular beam epitaxy,we demonstrate that La_(2−x)Sr_(x)CuO_(4)(x=0.15)thin films remain superconducting down to 2 unit cells of thickness but quickly reach the maximum superconducting transition temperature at and above 4 unit cells.By fitting the critical magnetic field(μ0H_(c2)),we show that the anisotropy of the film’s superconductivity increases with decreasing film thickness,indicating that the superconductivity of the film gradually evolves from weak three-to two-dimensional character.These results are helpful to gain more insight into the nature of high-temperature superconductivity with dimensionality.

Parameterization, sensitivity, and uncertainty of 1-D thermodynamic thin-ice thickness retrieval

Retrieval of Thin-Ice Thickness(TIT)using thermodynamic modeling is sensitive to the parameterization of the independent variables(coded in the model)and the uncertainty of the measured input variables.This article examines the deviation of the classical model’s TIT output when using different parameterization schemes and the sensitivity of the output to the ice thickness.Moreover,it estimates the uncertainty of the output in response to the uncertainties of the input variables.The parameterized independent variables include atmospheric longwave emissivity,air density,specific heat of air,latent heat of ice,conductivity of ice,snow depth,and snow conductivity.Measured input parameters include air temperature,ice surface temperature,and wind speed.Among the independent variables,the results show that the highest deviation is caused by adjusting the parameterization of snow conductivity and depth,followed ice conductivity.The sensitivity of the output TIT to ice thickness is highest when using parameterization of ice conductivity,atmospheric emissivity,and snow conductivity and depth.The retrieved TIT obtained using each parameterization scheme is validated using in situ measurements and satellite-retrieved data.From in situ measurements,the uncertainties of the measured air temperature and surface temperature are found to be high.The resulting uncertainties of TIT are evaluated using perturbations of the input data selected based on the probability distribution of the measurement error.The results show that the overall uncertainty of TIT to air temperature,surface temperature,and wind speed uncertainty is around 0.09 m,0.049 m,and−0.005 m,respectively.

Optimal parameter space for stabilizing the ferroelectric phase of Hf_(0.5)Zr_(0.5)O_(2) thin films under strain and electric fields

Hafnia-based ferroelectric materials, like Hf_(0.5)Zr_(0.5)O_(2)(HZO), have received tremendous attention owing to their potentials for building ultra-thin ferroelectric devices. The orthorhombic(O)-phase of HZO is ferroelectric but metastable in its bulk form under ambient conditions, which poses a considerable challenge to maintaining the operation performance of HZO-based ferroelectric devices. Here, we theoretically addressed this issue that provides parameter spaces for stabilizing the O-phase of HZO thin-films under various conditions. Three mechanisms were found to be capable of lowering the relative energy of the O-phase, namely, more significant surface-bulk portion of(111) surfaces, compressive c-axis strain,and positive electric fields. Considering these mechanisms, we plotted two ternary phase diagrams for HZO thin-films where the strain was applied along the in-plane uniaxial and biaxial, respectively. These diagrams indicate the O-phase could be stabilized by solely shrinking the film-thickness below 12.26 nm, ascribed to its lower surface energies. All these results shed considerable light on designing more robust and higher-performance ferroelectric devices.

Numerical Analysis on the Effect of n-Si on Cu(In, Ga)Se2 Based Thin-Films for High-Performance Solar Cells by 1D-SCAPS

We report the performances of a chalcopyrite Cu(In, Ga)Se2 CIGS-based thin-film solar cell with a newly employed high conductive n-Si layer. The data analysis was performed with the help of the 1D-Solar Cell Capacitance Simulator (1D-SCAPS) software program. The new device structure is based on the CIGS layer as the absorber layer, n-Si as the high conductive layer, i-In2S3, and i-ZnO as the buffer and window layers, respectively. The optimum CIGS bandgap was determined first and used to simulate and analyze the cell performance throughout the experiment. This analysis revealed that the absorber layer’s optimum bandgap value has to be 1.4 eV to achieve maximum efficiency of 22.57%. Subsequently, output solar cell parameters were analyzed as a function of CIGS layer thickness, defect density, and the operating temperature with an optimized n-Si layer. The newly modeled device has a p-CIGS/n-Si/In2S3/Al-ZnO structure. The main objective was to improve the overall cell performance while optimizing the thickness of absorber layers, defect density, bandgap, and operating temperature with the newly employed optimized n-Si layer. The increase of absorber layer thickness from 0.2 - 2 µm showed an upward trend in the cell’s performance, while the increase of defect density and operating temperature showed a downward trend in solar cell performance. This study illustrates that the proposed cell structure shows higher cell performances and can be fabricated on the lab-scale and industrial levels.

Numerical and experimental study on the falling film flow characteristics with the effect of co-current gas flow in hydrogen liquefaction process

Liquid hydrogen storage and transportation is an effective method for large-scale transportation and utilization of hydrogen energy. Revealing the flow mechanism of cryogenic working fluid is the key to optimize heat exchanger structure and hydrogen liquefaction process(LH2). The methods of cryogenic visualization experiment, theoretical analysis and numerical simulation are conducted to study the falling film flow characteristics with the effect of co-current gas flow in LH2spiral wound heat exchanger.The results show that the flow rate of mixed refrigerant has a great influence on liquid film spreading process, falling film flow pattern and heat transfer performance. The liquid film of LH2mixed refrigerant with column flow pattern can not uniformly and completely cover the tube wall surface. As liquid flow rate increases, the falling film flow pattern evolves into sheet-column flow and sheet flow, and liquid film completely covers the surface of tube wall. With the increase of shear effect of gas-phase mixed refrigerant in the same direction, the liquid film gradually becomes unstable, and the flow pattern eventually evolves into a mist flow.

Pipeline thickness estimation using the dispersion of higher-order SH guided waves

Thickness measurement plays an important role in the monitoring of pipeline corrosion damage. However, the requirement for prior knowledge of the shear wave velocity in the pipeline material for popular ultrasonic thickness measurement limits its widespread application. This paper proposes a method that utilizes cylindrical shear horizontal(SH) guided waves to estimate pipeline thickness without prior knowledge of shear wave velocity. The inversion formulas are derived from the dispersion of higher-order modes with the high-frequency approximation. The waveform of the example problems is simulated using the real-axis integral method. The data points on the dispersion curves are processed in the frequency domain using the wave-number method. These extracted data are then substituted into the derived formulas. The results verify that employing higher-order SH guided waves for the evaluation of thickness and shear wave velocity yields less than1% error. This method can be applied to both metallic and non-metallic pipelines, thus opening new possibilities for health monitoring of pipeline structures.

Isotopic dependence of the yield ratios of light fragments from different projectiles and their unified neutron skin thicknesses

The yield ratios of neutron-proton(R(n/p))and^(3)H-^(3)He(R(^(3)H∕^(3)He))with reduced rapidity from 0 to 0.5 were simulated at 50 MeV/u even-even ^(36−56)Ca+^(40)Ca,even-even ^(48−78)Ni+^(58)Ni,and ^(100−139)Sn(every third isotopes)+112 Sn for full reduced impact parameters using the isospin-dependent quantum molecular dynamics(IQMD)model.The neutron and proton density distributions and root-mean-square radii of the reaction systems were obtained using the Skyrme-Hartree-Fock model,which was used for the phase space initialization of the projectile and target in IQMD.We defined the unified neutron skin thickness asΔRnp=<r^(2)>^(1∕2) n−<r^(2)>^(1∕2)p,which was negative for neutron-deficient nuclei.The unifiedΔRnp values for nuclei with the same relative neutron excess from different isotopic chains were nearly equal,except for extreme neutron-rich isotopes,which is a type of scaling behavior.The yield ratios of the three isotopic chain-induced reactions,which depended on the reduced impact parameter and unified neutron skin thickness,were studied.The results showed that both R(n/p)and R(^(3)H∕^(3)He)decreased with a reduced impact parameter for extreme neutron-deficient isotopes;however,they increased with reduced impact parameters for extreme neutron-rich isotopes,and increased with theΔRnp of the projectiles for all reduced impact parameters.In addition,a scaling phenomenon was observed betweenΔR np and the yield ratios in peripheral colli-sions from different isotopic chain projectiles(except for extreme neutron-rich isotopes).Thus,R(n/p)and R(^(3)H∕^(3)He)from peripheral collisions were suggested as experimental probes for extracting the neutron or proton skin thicknesses of non-extreme neutron-rich nuclei from different isotopic chains.

Structure characterization of the oxide film on FGH96 superalloy powders with various oxidation degrees

The structure of the oxide film on FGH96 alloy powders significantly influences the mechanical properties of superalloys.In this study,FGH96 alloy powders with various oxygen contents were investigated using high-resolution transmission electron microscopy and atomic probe technology to elucidate the structure evolution of the oxide film.Energy dispersive spectrometer analysis revealed the presence of two distinct components in the oxide film of the alloy powders:amorphous oxide layer covering the γ matrix and amorphous oxide particles above the carbide.The alloying elements within the oxide layer showed a laminated distribution,with Ni,Co,Cr,and Al/Ti,which was attributed to the decreasing oxygen equilibrium pressure as oxygen diffused from the surface into the γ matrix.On the other hand,Ti enrichment was observed in the oxide particles caused by the oxidation and decomposition of the carbide phase.Comparative analysis of the oxide film with oxygen contents of 140,280,and 340 ppm showed similar element distributions,while the thickness of the oxide film varies approximately at 9,14,and 30 nm,respectively.These findings provide valuable insights into the structural analysis of the oxide film on FGH96 alloy powders.

Structural and magnetic properties of micropolycrystalline cobalt thin films fabricated by direct current magnetron sputtering

Pure cobalt(Co)thin films were fabricated by direct current magnetron sputtering,and the effects of sputtering power and pres-sure on the microstructure and electromagnetic properties of the films were investigated.As the sputtering power increases from 15 to 60 W,the Co thin films transition from an amorphous to a polycrystalline state,accompanied by an increase in the intercrystal pore width.Simultaneously,the resistivity decreases from 276 to 99μΩ·cm,coercivity increases from 162 to 293 Oe,and in-plane magnetic aniso-tropy disappears.As the sputtering pressure decreases from 1.6 to 0.2 Pa,grain size significantly increases,resistivity significantly de-creases,and the coercivity significantly increases(from 67 to 280 Oe),which can be attributed to the increase in defect width.Corres-pondingly,a quantitative model for the coercivity of Co thin films was formulated.The polycrystalline films sputtered under pressures of 0.2 and 0.4 Pa exhibit significant in-plane magnetic anisotropy,which is primarily attributable to increased microstress.

Enhanced ferroelectric and improved leakage of BFO-based thin films through increasing entropy strategy

BiFeO_(3)(BFO)has received considerable attention as a lead-free ferroelectric film due to its large theoretical remnant polariza-tion.However,BFO suffers from a large leakage current,resulting in poor ferroelectric properties.Herein,the sol-gel method was used to deposit a series of BFO-based thin films on fluorine-doped tin oxide substrates,and the effects of the substitution of the elements Co,Cu,Mn(B-site)and Sm,Eu,La(A-site)on the crystal structure,ferroelectricity,and leakage current of the BFO-based thin films were invest-igated.Results confirmed that lattice distortion by X-ray diffraction can be attributed to the substitution of individual elements in the BFO-based films.Sm and Eu substitutions contribute to the lattice distortion in a pseudo-cubic structure,while La is biased toward pseudo-tet-ragonal.Piezoelectric force microscopy confirmed that reversible switching of ferroelectric domains by nearly 180°can be realized through the prepared films.The ferroelectric hysteresis loops showed that the order for the polarization contribution is as follows:Cu>Co>Mn(B-site),Sm>La>Eu(A-site).The current density voltage curves indicated that the order for leakage contribution is as follows:Mn<Cu<Co(B-site),La<Eu<Sm(A-site).Scanning electron microscopy showed that the introduction of Cu elements facilitates the formation of dense grains,and the grain size distribution statistics proved that La element promotes the reduction of grain size,leading to the increase of grain boundaries and the reduction of leakage.Finally,a Bi_(0.985)Sm_(0.045)La_(0.03)Fe_(0.96)Co_(0.02)Cu_(0.02)O_(3)(SmLa-CoCu)thin film with a qualitative leap in the remnant polarization from 25.5(Bi_(0.985)Sm_(0.075)FeO_(3))to 98.8µC/cm^(2)(SmLa-CoCu)was prepared through the syner-gistic action of Sm,La,Co,and Cu elements.The leakage current is also drastically reduced from 160 to 8.4 mA/cm^(2)at a field strength of 150 kV/cm.Thus,based on the increasing entropy strategy of chemical engineering,this study focuses on enhancing ferroelectricity and decreasing leakage current,providing a promising path for the advancement of ferroelectric devices.

Local thermal conductivity of inhomogeneous nano-fluidic films:A density functional theory perspective

Combining the mean field Pozhar-Gubbins(PG)theory and the weighted density approximation,a novel method for local thermal conductivity of inhomogeneous fluids is proposed.The correlation effect that is beyond the mean field treatment is taken into account by the simulation-based empirical correlations.The application of this method to confined argon in slit pore shows that its prediction agrees well with the simulation results,and that it performs better than the original PG theory as well as the local averaged density model(LADM).In its further application to the nano-fluidic films,the influences of fluid parameters and pore parameters on the thermal conductivity are calculated and investigated.It is found that both the local thermal conductivity and the overall thermal conductivity can be significantly modulated by these parameters.Specifically,in the supercritical states,the thermal conductivity of the confined fluid shows positive correlation to the bulk density as well as the temperature.However,when the bulk density is small,the thermal conductivity exhibits a decrease-increase transition as the temperature is increased.This is also the case in which the temperature is low.In fact,the decrease-increase transition in both the small-bulk-density and low-temperature cases arises from the capillary condensation in the pore.Furthermore,smaller pore width and/or stronger adsorption potential can raise the critical temperature for condensation,and then are beneficial to the enhancement of the thermal conductivity.These modulation behaviors of the local thermal conductivity lead immediately to the significant difference of the overall thermal conductivity in different phase regions.

Effects of gallium surfactant on AlN thin films by microwave plasma chemical vapor deposition

In this work, AlN films were grown using gallium (Ga) as surfactant on 4° off-axis 4H-SiC substrates via microwave plasma chemical vapor deposition (MPCVD). We have found that AlN growth rate can be greatly improved due to the catalytic effect of trimethyl-gallium (TMGa), but AlN crystal structure and composition are not affected. When the proportion of TMGa in gas phase was low, crystal quality of AlN can be improved and three-dimensional growth mode of AlN was enhanced with the increase of Ga source. When the proportion of TMGa in gas phase was high, two-dimensional growth mode of AlN was presented, with the increase of Ga source results in the deterioration of AlN crystal quality. Finally, employing a two-step growth approach, involving the initial growth of Ga-free AlN nucleation layer followed by Ga-assisted AlN growth, high quality of AlN film with flat surface was obtained and the full width at half maximum (FWHM) values of 415 nm AlN (002) and (102) planes were 465 and 597 arcsec.

Effects of Mg-doping temperature on the structural and electrical properties of nonpolar a-plane p-type GaN films

Nonpolar(11–20) a-plane p-type GaN films were successfully grown on r-plane sapphire substrate with the metal–organic chemical vapor deposition(MOCVD) system. The effects of Mg-doping temperature on the structural and electrical properties of nonpolar p-type GaN films were investigated in detail. It is found that all the surface morphology, crystalline quality, strains, and electrical properties of nonpolar a-plane p-type GaN films are interconnected, and are closely related to the Mg-doping temperature. This means that a proper performance of nonpolar p-type GaN can be expected by optimizing the Mg-doping temperature. In fact, a hole concentration of 1.3×10^(18)cm^(-3), a high Mg activation efficiency of 6.5%,an activation energy of 114 me V for Mg acceptor, and a low anisotropy of 8.3% in crystalline quality were achieved with a growth temperature of 990℃. This approach to optimizing the Mg-doping temperature of the nonpolar a-plane p-type GaN film provides an effective way to fabricate high-efficiency optoelectronic devices in the future.

Surface Deposition of Ni(OH)_(2) and Lattice Distortion Induce the Electrochromic Performance Decay of NiO Films in Alkaline Electrolyte

NiO,an anodic electrochromic material,has applications in energy-saving windows,intelligent displays,and military camouflage.However,its electrochromic mechanism and reasons for its performance degradation in alkaline aqueous electrolytes are complex and poorly understood,making it challenging to improve NiO thin films.We studied the phases and electrochemical characteristics of NiO films in different states(initial,colored,bleached and after 8000 cycles)and identified three main reasons for performance degradation.First,Ni(OH)_(2)is generated during electrochromic cycling and deposited on the NiO film surface,gradually yielding a NiO@Ni(OH)_(2)core-shell structure,isolating the internal NiO film from the electrolyte,and preventing ion transfer.Second,the core-shell structure causes the mode of electrical conduction to change from first-to second-order conduction,reducing the efficiency of ion transfer to the surface Ni(OH)_(2)layer.Third,Ni(OH)_(2)and NiOOH,which have similar crystal structures but different b-axis lattice parameters,are formed during electrochromic cycling,and large volume changes in the unit cell reduce the structural stability of the thin film.Finally,we clarified the mechanism of electrochromic performance degradation of NiO films in alkaline aqueous electrolytes and provide a route to activation of NiO films,which will promote the development of electrochromic technology.

Study on crustal thickness and the prediction of prolific depressions:the Bohai Basin as an example

The deep crustal structure is closely related to oil and gas reserves.Predicting the oil and gas enrichment of depressions based on the Moho depth and crustal thickness is a promising research topic with significant implications for guiding exploration in petroliferous basins.In this study,seismic data were used as a constraint on the use of satellite gravity anomaly inversion to obtain the distribution of Moho depth and crustal thickness in the Bohai Basin.Stretching factors were calculated to analyze the differential distribution of deep crustal structural activity.Four indicators,including the minimum Moho depth,minimum crustal thickness,sum of Moho stretching factors,and sum of crustal stretching factors,were selected.Principal component analysis was applied to reduce the dimensionality of the multi-indicator system and obtain an oil and gas enrichment score for quantitative prediction of favorable prolific depressions.The deviation between the inverted Moho depth and seismic constraints was small;thus,the data effectively reflect the variations in the characteristics of each depression.The analysis revealed significant statistical features related to the minimum Moho depth/crustal thickness and the sum of Moho/crustal stretching factors associated with prolific depressions.Based on the oil and gas enrichment score,the depressions were classified into four categories related to their different deep crustal structural characteristics.Highly active ClassⅠ,ClassⅡ,and ClassⅢdepressions are predicted to be favorable prolific depressions.This study expands the research on quantitatively predicting favorable prolific depressions in the Bohai Basin using the deep crustal structure and can contribute to reducing production costs and improving exploration efficiency in future explorations.

Epitaxial growth of ultrathin gallium films on Cd(0001)

Growth and electronic properties of ultrathin Ga films on Cd(0001) are investigated by low-temperature scanning tunneling microscopy(STM) and density functional theory(DFT) calculations. It is found that Ga films exhibit the epitaxial growth with the pseudomorphic 1×1 lattice. The Ga islands deposited at 100 K show a ramified shape due to the suppressed edge diffusion and corner crossing. Furthermore, the majority of Ga islands reveal flat tops and a preferred height of three atomic layers, indicating the electronic growth at low temperature. Annealing to room temperature leads to not only the growth mode transition from electronic growth to conventional Stranski–Krastanov growth, but also the shape transition from ramified islands to smooth compact islands. Scanning tunneling spectroscopy(STS) measurements reveal that the Ga monolayer exhibits metallic behavior. DFT calculations indicate that all the interfacial Ga atoms occupy the energetically favorable hcp-hollow sites of the substrate. The charge density difference analysis demonstrates that the charge transfer from the Cd substrate to the Ga atoms is negligible, and there is weak interaction between Ga atoms and the Cd substrate. These results shall shed important light on fabrication of ultrathin Ga films on metal substrates with novel physical properties.

Influence of liquid film shape on evaporation performance of agitated thin film evaporator

The agitated thin film evaporator(ATFE),which is known for its high efficiency,force the material to form a film through the scraping process of a scraper,followed by evaporation and purification.The complex shape of the liquid film inside the evaporator can significantly affect its evaporation capability.This work explores how change in shape of the liquid films affect the evaporation of the materials with non-Newtonian characteristics,achieved by changing the structure of the scraper.Examining the distribution of circumferential temperature,viscosity,and mass transfer of the flat liquid film shows that the film evaporates rapidly in shear-thinning region.Various wavy liquid films are developed by using shear-thinning theory,emphasizing the flow condition in the thinning area and the factors contributing to the exceptional evaporation capability.Further exploration is conducted on the spread patterns of the wavy liquid film and flat liquid film on the evaporation wall throughout the process.It is noted that breaking the wavy liquid film on the evaporating wall during evaporation is challenging due to its film-forming condition.For which the fundamental causes are demonstrated by acquiring the data regarding the flow rate and temperature of the liquid film.The definitive findings of the analysis reveal a significant improvement in the evaporation capability of the wavy liquid film.This enhancement is attributed to increasing the shear-thinning areas and maintaining the overall shape of the film throughout the entire evaporation process.

Theoretical and Experimental Study on the Performance of Hermetic Diaphragm Squeeze Film Dampers for Gas-Lubricated Bearings

Low damping characteristics have always been a key sticking points in the development of gas bearings.The application of squeeze film dampers can significantly improve the damping performance of gas lubricated bearings.This paper proposed a novel hermetic diaphragm squeeze film damper(HDSFD)for oil-free turbomachinery supported by gas lubricated bearings.Several types of HDSFDs with symmetrical structure were proposed for good damping performance.By considering the compressibility of the damper fluid,based on hydraulic fluid mechanics theory,a dynamic model of HDSFDs under medium is proposed,which successfully reflects the frequency dependence of force coefficients.Based on the dynamic model,the effects of damper fluid viscosity,bulk modulus of damper fluid,thickness of damper fluid film and plunger thickness on the dynamic stiffness and damping of HDSFDs were analyzed.An experimental test rig was assembled and series of experimental studies on HDSFDs were conducted.The damper fluid transverse flow is added to the existing HDSFD concept,which aims to make the dynamic force coefficients independent of frequency.Although the force coefficient is still frequency dependent,the damping coefficient at high frequency excitation with damper fluid supply twice as that without damper fluid supply.The results serve as a benchmark for the calibration of analytical tools under development.

Ultrafast Laser-Induced Excellent Thermoelectric Performance of PEDOT:PSS Films

Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)is water processable,thermally stable,and highly conductive,PEDOT:PSS and its composites have been considered to be one of the most promising flexible thermoelectric materials.However,the PEDOT:PSS film prepared from its commercial aqueous dispersion usually has very low conductivity,thus cannot be directly utilized for TE applications.Here,a simple environmental friendly strategy via femtosecond laser irradiation without any chemical dopants and treatments was demonstrated.Under optimal conditions,the electrical conductivity of the treated film is increased to 803.1 S cm^(-1)from 1.2 S cm^(-1)around three order of magnitude higher,and the power factor is improved to 19.0μW m^(-1)K^(-2),which is enhanced more than 200 times.The mechanism for such remarkable enhancement was attributed to the transition of the PEDOT chains from a coil to a linear or expanded coil conformation,reduction of the interplanar stacking distance,and the removal of insulating PSS with increasing the oxidation level of PEDOT,facilitating the charge transportation.This work presents an effective route for fabricating high-performance flexible conductive polymer films and wearable thermoelectric devices.