The buoyancy-induced flow constitutes a core scientific issue for thermal management of electronic devices and thermal design of energy systems,where accurate characterization of flow and heat transfer is essential to...The buoyancy-induced flow constitutes a core scientific issue for thermal management of electronic devices and thermal design of energy systems,where accurate characterization of flow and heat transfer is essential to improve thermal efficiency.In this work,buoyancy-induced flow above two heating elements flush-mounted at the bottom of a square enclosure containing air is numerically investigated over a range of Rayleigh numbers(0<Ra≤1.5×10^(8)),with a focus on equal and unequal heat flux conditions under a constraint of constant total thermal energy input.Distinct flow transitions are observed in both cases,leading to the identification of three flow regimes:Steady,periodic unsteady,and chaotic unsteady.Two types of periodic flows are distinguished,in which the first is a periodic flow dominated by a fundamental frequency(FF)and its integer-multiple frequencies(INTMF),while the second is a more complex periodic flow featuring FF,INTMF,and their sub-harmonics.The transitions between these regimes are affected by the relative heat flux of the two heaters.When the heat flux of the two heaters is unequal,the range of Rayleigh numbers corresponding to periodic flow is suppressed.It is also found that the time-averaged maximum temperature of the strong heater increases more rapidly with Ra,while that of the weak heater increases more slowly,reflecting the interaction between buoyancy-driven flow dynamics and asymmetric heat input.Analysis of the time-averaged Nusselt number demonstrates that heat dissipation from the isothermal walls remains roughly equivalent,even when the heat flux of the two heaters differs by a factor of two.These findings highlight the critical roles of Rayleigh number,the number of heaters,and the heat flux ratio of the heaters in determining heat transfer and flow characteristics for buoyancy-driven convection systems,providing important theoretical support and design references for engineering scenarios such as electronic devices and design of new energy systems.展开更多
Unmanned aircraft are highly vulnerable to crosswind-induced turbulence during complex maneuvers such as turning,which can significantly compromise control and reduce autopilot effectiveness.This paper presents a nove...Unmanned aircraft are highly vulnerable to crosswind-induced turbulence during complex maneuvers such as turning,which can significantly compromise control and reduce autopilot effectiveness.This paper presents a novel control strategy to improve the controllability of unmanned aircraft in challenging wind conditions.First,the equations of motion for the aircraft are reformulated as a system of stochastic differential equations,which are subsequently transformed into a deterministic form.By modeling turbulence as a Gaussian random process and incorporating it directly into the control system,the proposed method proactively compensates for the adverse effects of turbulence.The transformation is achieved using semi-invariant techniques.Second,the control problem is formulated as an optimization task,aiming to minimize the deviation between the actual and desired turn characteristics,specifically the angular velocity.Finally,a new numerical method with proven global convergence is employed to compute the optimal autopilot parameters.Simulation results using a medium-range unmanned aircraft model under continuous turbulent gusts demonstrate that the proposed method significantly outperforms existing approaches,ensuring both stability and precision in turbulent wind conditions.展开更多
A compact low-profile dual-band Circularly Polarized(CP)microstrip antenna is proposed for the Bei Dou Navigation Satellite System(BDS).To achieve dual-band functionality,a single-layer multimode design is employed,in...A compact low-profile dual-band Circularly Polarized(CP)microstrip antenna is proposed for the Bei Dou Navigation Satellite System(BDS).To achieve dual-band functionality,a single-layer multimode design is employed,incorporating F-,L-,and T-shaped slots at the corners for CP performance.Additionally,a Defected Ground Structure(DGS)is implemented to further enhance the antenna's efficiency.A detailed parameter analysis is conducted to optimize the antenna's size and performance balance.After optimization,the final dimensions of the antenna are minimized while still meeting the design requirements.The prototype of the optimized antenna is fabricated and tested,demonstrating coverage of frequency bands from 1.182 GHz to 1.217 GHz and 1.547 GHz to 1.569 GHz.The antenna effectively supports dual-band CP for B1I and B2b frequency bands.A performance metric,the Ratio of relative Bandwidth to Volume(RBV),is introduced to evaluate the antenna's efficiency.Compared to similar designs,the proposed antenna offers a smaller size without sacrificing performance,making it well-suited for BDS airborne applications.展开更多
Experiments are performed in this paper to understand the influence of satellite radiance data on the initial field of a numerical prediction system and rainfall prediction. First, Advanced Microwave Sounder Unit A （...Experiments are performed in this paper to understand the influence of satellite radiance data on the initial field of a numerical prediction system and rainfall prediction. First, Advanced Microwave Sounder Unit A （AMSU-A） and Unit B （AMSU-B） radiance data are directly used by three-dimensional variational data assimilation to improve the background field of the numerical model. Then, the detailed effect of the radiance data on the background field is analyzed. Secondly, the background field, which is formed by application of Advanced Television and Infrared Observation Satellite Operational Vertical Sounder （ATOVS） microwave radiance assimilation, is employed to simulate some heavy rainfall cases. The experiment results show that the assimilation of AMSU-A （B） microwave radiance data has a certain impact on the geopotential height, temperature, relative humidity and flow fields. And the impacts on the background field are mostly similar in the different months in summer. The heavy rainfall experiments reveal that the application of AMSU-A （B） microwave radiance data can improve the rainfall prediction significantly. In particular, the AMSU-A radiance data can significantly enhance the prediction of rainfall above 10 mm within 48 h, and the AMSU-B radiance data can improve the prediction of rainfall above 50 mm within 24 h. The present study confirms that the direct assimilation of satellite radiance data is an effective way to improve the prediction of heavy rainfall in the summer in China.展开更多
Objective To examine the effects of exogenously administered intermedin （IMD,adrenomedullin-2） on arterial blood pressure,cardiac function and the cardiovascular IMD receptor system in spontaneously hypertensive ra...Objective To examine the effects of exogenously administered intermedin （IMD,adrenomedullin-2） on arterial blood pressure,cardiac function and the cardiovascular IMD receptor system in spontaneously hypertensive rats （SHRs） as well as to investigate the associated mechanisms.Methods Thirteen week-old male rats were divided in Wistar Kyoto （WKY） group （n =12）,SHR group （n =12）,IMD group （SHRs infused with IMD 1-47 500 ng/kg per hour,n =12）,and ADM group （SHRs infused with adrenomedullin 500 ng/kg per hour,n =12）.Results A two-week continuous administration of low dose IMD 1-47 via mini-osmotic pumps markedly reduced blood pressure,the maximal rates of increase and decrease of left-ventricle pressure development （LV ± dp/dtmax）,left ventricular systolic pressure and heart rate in SHRs.Furthermore,IMD also inhibited protein over-expression of cardiovascular IMD receptors,myocardial Receptor Activity-Modifying Proteins （RAMP1 and RAMP2）,aortic RAMP1,RAMP2,RAMP3,and calcitonin receptor-like receptor （CRLR）;suppressed up-regulation of aortic RAMP1,RAMP2,RAMP3 and CRLR gene expression; and markedly elevated the mRNA abundance of myocardial atrial natriuretic peptide （ANP） and myocardial brain natriuretic peptide （BNP）.Additionally,IMD 1-47 administration in SHRs increased aortic cAMP concentration and reduced myocardial cAMP concentration.Conclusion These findings support the speculation that IMD,as a cardiovascular active peptide,is involved in blood pressure reduction and cardiac function amelioration during hypertension.The mechanism underlying this effect may involve IMD binding of a receptor complex formed by RAMPs and CRLR,and consequential regulation of cAMP levels and other cardiovascular active factors,such as ANP and BNP.展开更多
Background:Military operation personnel often suffer from sleep difficulty because of their work requirements.In this study,we investigated the efficacy of zaleplon at two doses to induce afternoon-sleep under noise i...Background:Military operation personnel often suffer from sleep difficulty because of their work requirements.In this study,we investigated the efficacy of zaleplon at two doses to induce afternoon-sleep under noise interference and its effects on psychomotor performance and vestibular function; we subsequently established the optimal dosage regimen for military operation personnel.Methods:Twenty-two healthy young male volunteers were recruited for the study.Eight subjects took 10 mg or 15 mg of zaleplon and placebo alternately and then were exposed to noise.Changes in polysomnography(PSG) indices,including sleep latency(SL),sleep efficiency(SE) and sleep structure,were recorded after drug administration.After awakening,the volunteers' subjective judgments of sleep quality and sleepiness were measured.Eight volunteers underwent 3 psychomotor performance tests at a one-week interval,and the psychomotor performance tests were conducted before and after taking zaleplon and placebo.Six volunteers participated in the vestibular function test session,and parameters,including optokinetic nystagmus(OKN),vestibular ocular reflex(VOR),visualvestibular ocular reflex(VVOR) and vestibular ocular reflex fixation suppression(VOR-Fix),were detected by the same experimental design as described above.The data of sleep observations were subjected to one-way variance analysis.Results:Compared with the placebo group,SL was shortened significantly,and the scores of subjective sleep quality and sleep depth were clearly increased in the zaleplon 10 mg group(P<0.05).Moreover,the SE and the percent of REM(rapid eye movement) sleep were increased remarkably in the zaleplon 15 mg group(P<0.01).Furthermore,the SE,percent of REM sleep and scores of subjective sleep depth in the zaleplon 15 mg group were significantly higher than in the zaleplon 10 mg group(P<0.05).The psychomotor performance did not change significantly after ingestion of 10 mg or 15 mg of zaleplon,whereas the OKN and VOR gains were lower in the two dose groups of zaleplon(P<0.05) and restored to normal 3h after drug ingestion.Conclusion:Zaleplon is an ideal hypnotic for military personnel,and its hypnotic efficiency is dose-related under noise interference; a 15 mg dose of zaleplon could provide significantly better sleep than a 10 mg dose of zaleplon.展开更多
An analytical solution is obtained for the Functionally Graded Shape Memory Alloy （FG-SMA） composites subjected to thermo-mechanical coupling. Young＇s modulus and thermal expansion coefficient of the material are a...An analytical solution is obtained for the Functionally Graded Shape Memory Alloy （FG-SMA） composites subjected to thermo-mechanical coupling. Young＇s modulus and thermal expansion coefficient of the material are assumed to vary in different forms of power function through the thickness, with the Poisson＇s ratio being constant. An SMA constitutive model is combined with the averaging techniques of composite to determine the mechanical properties of the FG-SMA composites. Different phase transformation steps and the corresponding stress distributions through the thickness direction are given. The results show that the average stresses decrease as the transformations proceed.展开更多
LM23 is a gene specifically expressed in the testis of Rattus norvegicus, as previously reported by our laboratory. The aim of the study is to further investigate the biological function of LM23. Several bioinformatic...LM23 is a gene specifically expressed in the testis of Rattus norvegicus, as previously reported by our laboratory. The aim of the study is to further investigate the biological function of LM23. Several bioinformatic tools were utilized, including PROSITE and BLAST. To determine the subcellullar localization of LM23, a polyclonal antibody specific for LM23 was generated via the immunization of rabbits. The LM23gene was cloned from rat testis tissue, and LM23 protein was expressed in Escherichia co/i. The biological function of LM23 was analyzed with microarray analysis and immunohistochemistry, using a rat model of LM23 gene knockdown. The results suggested that LM23 belongs to the Speedy/Ringo family. LM23 regulated the GI/S and G2/M transitions of the cell cycle during spermatogenesis. Downregulation of the LM23gene during spermatogenesis could lead to the activation of both the Fas-FasL pathway and the mitochondrial pathway. These novel findings indicate that LM23 has a diverse array of functions that are important in both the life and death of the spermatogenic cell.展开更多
The integrity and regularity of pore morphology play an important role in determining the mechanical properties of the metallic foam materials.The conventional methods on refining pore morphology are mainly focused on...The integrity and regularity of pore morphology play an important role in determining the mechanical properties of the metallic foam materials.The conventional methods on refining pore morphology are mainly focused on the optimization of fabrication techniques,however,they are usually inconvenient and complicated.Recently,incorporating nano reinforcement is considered to be a suitable way to fabricate metallic composite foams accompanied by optimized pore morphology and enhanced mechanical properties.In this work,through a facile and rapid powder metallurgy foaming method,the aluminum-silicon(Al-Si)alloy composite foams reinforced by graphene nanosheets(GNSs)are successfully fabricated.The microstructure analyses reveal that,for the Al-Si alloy foams incorporating the GNSs(GNSs/Al-Si composite foams),the pore size is transformed to be smaller,the pore size distributions become more homogeneous and the pore shape is also refined to a regular and roundish state.Meanwhile,the shape of Si precipitates is found transforming from an irregular long strip(length of~20μm,width of~5μm)to a fine particle state(diameter of~5μm).Moreover,the compressive testing results show that,the 0.4wt%GNSs/Al-Si composite foams own the optimal compression stress of 11.7±0.5 MPa,plateau stress of 10.0±1.0 MPa and energy absorption capacity of 6.8±0.7 MJ/m^(3),which have improvement of 58.1%,53.8%and 51.1%in comparison with the Al-Si alloy foams counterpart,respectively.The present findings may pave a new way for developing new generation of metallic composite foams that with stable microstructure and excellent mechanical performance.展开更多
AIM： To compare the optical quality after implantation of implantable collamer lens（ICL） and wavefront-guided laser in situ keratomileusis（WG-LASIK）.METHODS： The study included 40 eyes of 22 patients with myopia...AIM： To compare the optical quality after implantation of implantable collamer lens（ICL） and wavefront-guided laser in situ keratomileusis（WG-LASIK）.METHODS： The study included 40 eyes of 22 patients with myopia who accepted ICL implantation and 40 eyes of 20 patients with myopia who received WG-LASIK. Before surgery and three months after surgery, the objective scattering index（OSI）, the values of modulation transfer function（MTF） cutoff frequency, Strehl ratio, and the Optical Quality Analysis System（OQAS） values（OVs） were accessed. The higher order aberrations（HOAs） data including coma, trefoil, spherical, 2^（nd） astigmatism and tetrafoil were also obtained. For patients with pupil size 〈6 mm, HOAs data were analyzed for 4 mm-pupil diameter. For patients with pupil size ≥6 mm, HOAs data were calculated for 6 mm-pupil diameter. Visual acuity, refraction, pupil size and intraocular pressures were also recorded.RESULTS： In both ICL and WG-LASIK group, significant improvements in visual acuities were found postoperatively, with a significant reduction in spherical equivalent（P〈 0.001）. After the ICL implantation, the OSI decreasedslightly from 2.34±1.92 to 2.24±1.18 with no statistical significance（P=0.62）. While in WG-LASIK group, the OSI significantly increased from 0.68±0.43 preoperatively to 0.91±0.53 postoperatively（Wilcoxon signed ranks test, P=0.000）. None of the mean MTF cutoff frequency, Strehl ratio, OVs showed statistically significant changes in both ICL and WG-LASIK groups. In the ICL group, there were no statistical differences in the total HOAs for either 4 mmpupil or 6 mm-pupil. In the WG-LASIK group, the HOA parameters increased significantly at 4 mm-pupil. The total ocular HOAs, coma, spherical and 2^（nd） astigmatism were 0.12±0.06, 0.06±0.03, 0.00±0.03, 0.02±0.01, respectively. After the operation, these values were increased into 0.16±0.07, 0.08±0.05,-0.04±0.04, 0.03±0.01 respectively（Wilcoxon signed ranks test, all P〈0.05）. At 6 mm-pupil, the induction of total HOAs was not statistically significant in the WG-LASIK group. CONCLUSION： ICL implantation has a less disturbance to optical quality than WG-LASIK. The OQAS is a valuable complementary measurement to the wavefront aberrometers in evaluating the optical quality.展开更多
Objective Global cardiovascular risk assessment has been incorporated into current Chinese guidelines for the management of hypertension and hypercholesterolemia. The aim of our study is to determine the distribution ...Objective Global cardiovascular risk assessment has been incorporated into current Chinese guidelines for the management of hypertension and hypercholesterolemia. The aim of our study is to determine the distribution of 10-year risk for ischemic cardiovascular disease （ICVD） among middle-aged Chinese adults, and to evaluate the usefulness of global risk assessment tools in the primary prevention of ICVD in Chinese population.Methods Simplified prediction tools derived from the USA-PRC Collaborative Study of Cardiovascular Epidemiology cohort were applied to the Chinese Health Examination Database （CHED） 2008. 10-year risk for ICVD was estimated in 461 157 ICVD-free subjects （264 432 male and 196 725 female） aged 35 to 59 years. Results Among the male subjects, 82.4% had a 10-year risk for ICVD of 〈5%, 14.4% of 5% to 12.1% and 3.4 of≥ 12.2%, and in female subjects, 86.7% had a 10-year risk for ICVD of 〈5%, 12.1% of 5% to 12.0% and 1.2% of ≥ 12.1%. All subjects with predicted high level ICVD risk （≥ 12.2% in male or ≥ 12.1% in female） had either remarkably elevated （≥ 160 mmHg） blood pressure, significantly increased （≥ 6.22 mml/L） total serum cholesterol or diabetes.Conclusion Using the currently recommended prediction tools, only very small proportions of middle-aged Chinese men and women who were free of ICVD would be classified into high level risk group. These prediction tools are unlikely to help for the medical intervention decision making in Chinese adult patients with hypertension and/or hypercholesterolemia展开更多
The orbits and the dynamical symmetries for the screened Coulomb potentials and isotropic harmonic oscillators have been studied by Wu and Zeng [Z.B. Wund J.Y. Zeng, Phys. Rev. A 62 （2000） 032509]. We find similar p...The orbits and the dynamical symmetries for the screened Coulomb potentials and isotropic harmonic oscillators have been studied by Wu and Zeng [Z.B. Wund J.Y. Zeng, Phys. Rev. A 62 （2000） 032509]. We find similar properties in the corresponding systems in a sphericM space, whose dynamical symmetries are described by Higgs algebra. There exist extended Runge-Lenz vector for screened Coulomb potentials and extended quadruple tensor for screened harmonic oscillators. They, together with angular momentum, constitute the generators of the geometrical symmetry group. Moreover, there exist an infinite number of dosed orbits for suitable angular momentum values, and we give the equations of the classical orbits. The eigenenergy spectrum and corresponding eigenstates in these systems are derived.展开更多
In this work,the evolutions of stresses in both phases of the Al/SiCp composite subjected to thermal cycling during in situ compression test were measured using Time of Flight neutron diffraction.It was confirmed that...In this work,the evolutions of stresses in both phases of the Al/SiCp composite subjected to thermal cycling during in situ compression test were measured using Time of Flight neutron diffraction.It was confirmed that inter-phase stresses in the studied composite can be caused by differences in the coefficient of thermal expansion for the reinforcement and matrix,leading to a different variation of phase volumes during sample heating or cooling.The results of the diffraction experiment during thermal cycling were well predicted by the Thermo-Mechanical Self-Consistent model.The experimental study of elastic-plastic deformation was carried out in situ on a unique diffractometer EPSILON-MDS(JINR in Dubna,Russia)with nine detector banks measuring interplanar spacings simultaneously in 9 orientations of scattering vector.For the first time,the performed analysis of experimental data allowed to study the evolution of full stress tensor in both phases of the composite and to consider the decomposition of this tensor into deviatoric and hydrostatic components.It was found that the novel Developed Thermo-Mechanical SelfConsistent model correctly predicted stress evolution during compressive loading,taking into account the relaxation of thermal origin hydrostatic stresses.The comparison of this model with experimental data at the macroscopic level and the level of phases showed that strengthening of the Al/SiCp composite is caused by stress transfer from the plastically deformed A12124 matrix to the elastic SiCp reinforcement,while thermal stresses relaxation does not significantly affect the overall composite properties.展开更多
Thermal barrier coating ( TBC) consisting of a NiCoCrAlY bond coat ( BC) and a ZrO2-8 wt. % Y2O3 topcoat ( TC) was fabricated on the nickel-base superalloy by air plasma spray ( APS) . The BC was treated by supersonic...Thermal barrier coating ( TBC) consisting of a NiCoCrAlY bond coat ( BC) and a ZrO2-8 wt. % Y2O3 topcoat ( TC) was fabricated on the nickel-base superalloy by air plasma spray ( APS) . The BC was treated by supersonic fine particle bombarding ( SFPB) . Thermal cyclic failure and residual stress in thermally grown oxide ( TGO) scale were studied by SEM with EDS and ruby fluorescence spectroscopy ( RFS) . As shown in the results,after treated by SFPB,thickening of TGO was relatively slow,which reduced the level of growth stress. The TBC with SFPB treatment was still remained well undergoing 350 times of thermal cycle. However,after thermal cycle with the same times,the separation of TC was observed in TBC without SFPB treatment. The residual stress analysis by RFS showed that the residual stress of SFPB-treated TBC increased with the increasing number of thermal cycle. The residual stress of conventional TBC reached a value of 650 MPa at 350 times of cycle and that of SFPB-treated TBC only reached 532 MPa at 400 times of cycle. The BC with SFPB treatment after 400 times of cycle was analyzed by RFS,the high stress value was not observed in local thickened region of TGO. Thermal cycling resistance of TBC can be improved by the SFPB technology.展开更多
As widely used protective materials,the application of Al foams is still limited by their low intrinsic mechanical properties caused by the brittleness of struts.The introduction of Mg is recently demonstrated effecti...As widely used protective materials,the application of Al foams is still limited by their low intrinsic mechanical properties caused by the brittleness of struts.The introduction of Mg is recently demonstrated effective to improve the mechanical performance of Al foams;however,the mechanism of Mg modification is still not clear.In this work,Al-Mg foams are developed through a powder metallurgy process with excellent compression performance and high energy absorption capacity.The effects of Mg modification on the cell structure,toughness,and deformation behavior are investigated systematically.As a result,the small cell size of~1.8 mm and the high sphericity of 0.92 are achieved with 5% of Mg addition,delivering high compression stress of 8.5±0.43 MPa and energy absorption capacity of 6.9±0.36 MJ/m^(3),simultaneously.The synergistic mechanism for the improved mechanical performance is also demonstrated to be the combination of stress transfer and plastic deformation behavior of cells.The results provide a new strategy to develop high-performance foam materials by improving toughness and further promote the practical application.展开更多
To address the need for the on-site measurement of aging oil, in this paper, we propose an impedance-based microsensor for analyzing the moisture content in engine oil. Using a microfabrication process, we fabricated ...To address the need for the on-site measurement of aging oil, in this paper, we propose an impedance-based microsensor for analyzing the moisture content in engine oil. Using a microfabrication process, we fabricated an interdigitated microelectrode and integrated it with a 3 D-printed microcontainer to produce a microsensor that can detect changes in the permittivity of oil. When the moisture content in oil increases, this sensor can detect the resulting change in the oil impedance, which is related to its permittivity, and then determine the degree to which the oil has aged. The test results show that the proposed microsensor has the advantages of being small and having high sensitivity, good accuracy, and the ability to be combined with hand-held instruments.The proposed method is expected to be used for the rapid, low cost, on-site determination of oil aging.展开更多
First-principles calculations based on the density functional theory（DFT） and ultra-soft pseudopotential are employed to study the atomic configuration and charge density of impurity P in Ni Al Σ5 grain boundary（G...First-principles calculations based on the density functional theory（DFT） and ultra-soft pseudopotential are employed to study the atomic configuration and charge density of impurity P in Ni Al Σ5 grain boundary（GB）. The negative segregation energy of a P atom proves that a P atom can easily segregate in the Ni Al GB. The atomic configuration and formation energy of the P atom in the Ni Al GB demonstrate that the P atom tends to occupy an interstitial site or substitute a Al atom depending on the Ni/Al atoms ratio. The P atom is preferable to staying in the Ni-rich environment in the Ni Al GB forming P–Ni bonds. Both of the charge density and the deformation charge imply that a P atom is more likely to bond with Ni atoms rather than with Al atoms. The density of states further exhibits the interactions between P atom and Ni atom, and the orbital electrons of P, Ni and Al atoms all contribute to P–Ni bonds in the Ni Al GB. It is worth noting that the P–Ni covalent bonds might embrittle the Ni Al GB and weakens the plasticity of the Ni Al intermetallics.展开更多
Highly concentrated hydrogen peroxide has been widely used as a rocket mono-propellant and oxidiser since 1940＇s. Although the relevant specialist literature concerning HTP is relatively extensive, one can still find...Highly concentrated hydrogen peroxide has been widely used as a rocket mono-propellant and oxidiser since 1940＇s. Although the relevant specialist literature concerning HTP is relatively extensive, one can still find many myths about highly concentrated hydrogen peroxide, especially concerning safety aspects about its preparation by different techniques, handling or further utilisation. Such ambiguities can result in rather apprehensive approach towards preparing, utilising or even handling of HTP in relevant industry or research fields. The paper contains modern approach to laboratory preparation of highly concentrated solutions of hydrogen peroxide of HTP class （concentration 98%＋） that is intended for propulsive （rocket） applications. Authors, who have gained extensive experience in the field of HTP preparation, handling and utilisation, concisely explain facts and disprove some common myths concerning HTP. Additionally, advantages and possible application of 98%＋ solutions of HTP in various propulsive systems such as small satellites are described. The attention is also paid to the possibility of replacing currently used toxic and corrosive rocket propellants, such as hydrazine and its derivatives, RFNA （red fuming nitric acid）, MON （mixed oxides of nitrogen） or NTO （dinitrogen tetroxide）, by 98%＋ HTP. The potential of the medium as green and easy to handle propellant that can act both, as monopropellant or strong liquid oxidiser with hypergolic capability, is outlined briefly as well.展开更多
A concise analytical model for the static dipole polarizability of ionized atoms and molecules is created for the first time.As input,it requires,alongside the polarizability of neutral counterpart of a given ion,only...A concise analytical model for the static dipole polarizability of ionized atoms and molecules is created for the first time.As input,it requires,alongside the polarizability of neutral counterpart of a given ion,only the charge and elemental composition.This physically motivated semiempirical model is based on a number of established regularities in polarizability of charged monatomic and polyatomic compounds.In order to adjust it,the results of quantum chemistry calculations and gas-phase measurements available for a broad range of ionized multielectron species are employed.To counteract the appreciable bias in the literature data toward polarizability of monoatomic ions,for some molecular ions of general concern the results of the authors'own density functional theory calculations are additionally invoked.A total of 541 data points are used to optimize the model.It is demonstrated that the model we suggested has reasonable(given the substantial uncertainties of the reference data)accuracy in predicting the static isotropic polarizability of arbitrarily charged ions of any size and atomic composition.The resulting polarizability estimates are found to achieve a coefficient of determination of 0.93 for the assembled data set.The created analytic tool is universally applicable and might be advantageous for some applications where there is an urgent need for rapid low-cost evaluation of the static gas-phase polarizability of ionized atoms and molecules.This is especially relevant to constructing the complex models of nonequilibrium chemical kinetics aimed at precisely describing the observable refractive index(dielectric permittivity)of plasma flows.The data sets that support the findings of this study are openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.07526.展开更多
We present a semiempirical analytical model for the static polarizability of electronically excited atoms and molecules,which requires very few readily accessible input data,including the ground-state polarizability,e...We present a semiempirical analytical model for the static polarizability of electronically excited atoms and molecules,which requires very few readily accessible input data,including the ground-state polarizability,elemental composition,ionization potential,and spin multiplicities of excited and ground states.This very simple model formulated in a semiclassical framework is based on a number of observed trends in polarizability of electronically excited compounds.To adjust the model,both accurate theoretical predictions and reliable measurements previously reported elsewhere for a broad range of multielectron species in the gas phase are utilized.For some representative compounds of general concern that have not yet attracted sufficient research interest,the results of our multireference second-order perturbation theory calculations are additionally engaged.We show that the model we developed has reasonable(given the considerable uncertainties in the reference data)accuracy in predicting the static polarizability of electronically excited species of arbitrary size and excitation energy.These findings can be useful for many applications,where there is a need for inexpensive and quick assessments of the static gas-phase polarizability of excited electronic states,in particular,when building the complex nonequilibrium kinetic models to describe the observed optical refractivity(dielectric permittivity)of nonthermal reacting gas flows.展开更多
基金supported by the Tianjin Education Commission Research Program Project(No.2024KJ105)。
文摘The buoyancy-induced flow constitutes a core scientific issue for thermal management of electronic devices and thermal design of energy systems,where accurate characterization of flow and heat transfer is essential to improve thermal efficiency.In this work,buoyancy-induced flow above two heating elements flush-mounted at the bottom of a square enclosure containing air is numerically investigated over a range of Rayleigh numbers(0<Ra≤1.5×10^(8)),with a focus on equal and unequal heat flux conditions under a constraint of constant total thermal energy input.Distinct flow transitions are observed in both cases,leading to the identification of three flow regimes:Steady,periodic unsteady,and chaotic unsteady.Two types of periodic flows are distinguished,in which the first is a periodic flow dominated by a fundamental frequency(FF)and its integer-multiple frequencies(INTMF),while the second is a more complex periodic flow featuring FF,INTMF,and their sub-harmonics.The transitions between these regimes are affected by the relative heat flux of the two heaters.When the heat flux of the two heaters is unequal,the range of Rayleigh numbers corresponding to periodic flow is suppressed.It is also found that the time-averaged maximum temperature of the strong heater increases more rapidly with Ra,while that of the weak heater increases more slowly,reflecting the interaction between buoyancy-driven flow dynamics and asymmetric heat input.Analysis of the time-averaged Nusselt number demonstrates that heat dissipation from the isothermal walls remains roughly equivalent,even when the heat flux of the two heaters differs by a factor of two.These findings highlight the critical roles of Rayleigh number,the number of heaters,and the heat flux ratio of the heaters in determining heat transfer and flow characteristics for buoyancy-driven convection systems,providing important theoretical support and design references for engineering scenarios such as electronic devices and design of new energy systems.
基金co-supported by the Fund of Robot Technology Used for Special Environment Key Laboratory of Sichuan Province(No.22kftk01)the Key Research and Development Program of Heilongjiang,China(No.2024ZXJ07B05)the National Natural Science Foundation of China(No.92471103)。
文摘Unmanned aircraft are highly vulnerable to crosswind-induced turbulence during complex maneuvers such as turning,which can significantly compromise control and reduce autopilot effectiveness.This paper presents a novel control strategy to improve the controllability of unmanned aircraft in challenging wind conditions.First,the equations of motion for the aircraft are reformulated as a system of stochastic differential equations,which are subsequently transformed into a deterministic form.By modeling turbulence as a Gaussian random process and incorporating it directly into the control system,the proposed method proactively compensates for the adverse effects of turbulence.The transformation is achieved using semi-invariant techniques.Second,the control problem is formulated as an optimization task,aiming to minimize the deviation between the actual and desired turn characteristics,specifically the angular velocity.Finally,a new numerical method with proven global convergence is employed to compute the optimal autopilot parameters.Simulation results using a medium-range unmanned aircraft model under continuous turbulent gusts demonstrate that the proposed method significantly outperforms existing approaches,ensuring both stability and precision in turbulent wind conditions.
基金co-supported by the Natural Science Foundation of Tianjin,China(No.21JCZDJC00860)the Civil Aviation Security Capacity Building Funding Project,China(No.2020[142])。
文摘A compact low-profile dual-band Circularly Polarized(CP)microstrip antenna is proposed for the Bei Dou Navigation Satellite System(BDS).To achieve dual-band functionality,a single-layer multimode design is employed,incorporating F-,L-,and T-shaped slots at the corners for CP performance.Additionally,a Defected Ground Structure(DGS)is implemented to further enhance the antenna's efficiency.A detailed parameter analysis is conducted to optimize the antenna's size and performance balance.After optimization,the final dimensions of the antenna are minimized while still meeting the design requirements.The prototype of the optimized antenna is fabricated and tested,demonstrating coverage of frequency bands from 1.182 GHz to 1.217 GHz and 1.547 GHz to 1.569 GHz.The antenna effectively supports dual-band CP for B1I and B2b frequency bands.A performance metric,the Ratio of relative Bandwidth to Volume(RBV),is introduced to evaluate the antenna's efficiency.Compared to similar designs,the proposed antenna offers a smaller size without sacrificing performance,making it well-suited for BDS airborne applications.
文摘Experiments are performed in this paper to understand the influence of satellite radiance data on the initial field of a numerical prediction system and rainfall prediction. First, Advanced Microwave Sounder Unit A （AMSU-A） and Unit B （AMSU-B） radiance data are directly used by three-dimensional variational data assimilation to improve the background field of the numerical model. Then, the detailed effect of the radiance data on the background field is analyzed. Secondly, the background field, which is formed by application of Advanced Television and Infrared Observation Satellite Operational Vertical Sounder （ATOVS） microwave radiance assimilation, is employed to simulate some heavy rainfall cases. The experiment results show that the assimilation of AMSU-A （B） microwave radiance data has a certain impact on the geopotential height, temperature, relative humidity and flow fields. And the impacts on the background field are mostly similar in the different months in summer. The heavy rainfall experiments reveal that the application of AMSU-A （B） microwave radiance data can improve the rainfall prediction significantly. In particular, the AMSU-A radiance data can significantly enhance the prediction of rainfall above 10 mm within 48 h, and the AMSU-B radiance data can improve the prediction of rainfall above 50 mm within 24 h. The present study confirms that the direct assimilation of satellite radiance data is an effective way to improve the prediction of heavy rainfall in the summer in China.
文摘Objective To examine the effects of exogenously administered intermedin （IMD,adrenomedullin-2） on arterial blood pressure,cardiac function and the cardiovascular IMD receptor system in spontaneously hypertensive rats （SHRs） as well as to investigate the associated mechanisms.Methods Thirteen week-old male rats were divided in Wistar Kyoto （WKY） group （n =12）,SHR group （n =12）,IMD group （SHRs infused with IMD 1-47 500 ng/kg per hour,n =12）,and ADM group （SHRs infused with adrenomedullin 500 ng/kg per hour,n =12）.Results A two-week continuous administration of low dose IMD 1-47 via mini-osmotic pumps markedly reduced blood pressure,the maximal rates of increase and decrease of left-ventricle pressure development （LV ± dp/dtmax）,left ventricular systolic pressure and heart rate in SHRs.Furthermore,IMD also inhibited protein over-expression of cardiovascular IMD receptors,myocardial Receptor Activity-Modifying Proteins （RAMP1 and RAMP2）,aortic RAMP1,RAMP2,RAMP3,and calcitonin receptor-like receptor （CRLR）;suppressed up-regulation of aortic RAMP1,RAMP2,RAMP3 and CRLR gene expression; and markedly elevated the mRNA abundance of myocardial atrial natriuretic peptide （ANP） and myocardial brain natriuretic peptide （BNP）.Additionally,IMD 1-47 administration in SHRs increased aortic cAMP concentration and reduced myocardial cAMP concentration.Conclusion These findings support the speculation that IMD,as a cardiovascular active peptide,is involved in blood pressure reduction and cardiac function amelioration during hypertension.The mechanism underlying this effect may involve IMD binding of a receptor complex formed by RAMPs and CRLR,and consequential regulation of cAMP levels and other cardiovascular active factors,such as ANP and BNP.
基金supported by a grant from the Military Medical Research Foundation of PLA,China (AWS14J011)
文摘Background:Military operation personnel often suffer from sleep difficulty because of their work requirements.In this study,we investigated the efficacy of zaleplon at two doses to induce afternoon-sleep under noise interference and its effects on psychomotor performance and vestibular function; we subsequently established the optimal dosage regimen for military operation personnel.Methods:Twenty-two healthy young male volunteers were recruited for the study.Eight subjects took 10 mg or 15 mg of zaleplon and placebo alternately and then were exposed to noise.Changes in polysomnography(PSG) indices,including sleep latency(SL),sleep efficiency(SE) and sleep structure,were recorded after drug administration.After awakening,the volunteers' subjective judgments of sleep quality and sleepiness were measured.Eight volunteers underwent 3 psychomotor performance tests at a one-week interval,and the psychomotor performance tests were conducted before and after taking zaleplon and placebo.Six volunteers participated in the vestibular function test session,and parameters,including optokinetic nystagmus(OKN),vestibular ocular reflex(VOR),visualvestibular ocular reflex(VVOR) and vestibular ocular reflex fixation suppression(VOR-Fix),were detected by the same experimental design as described above.The data of sleep observations were subjected to one-way variance analysis.Results:Compared with the placebo group,SL was shortened significantly,and the scores of subjective sleep quality and sleep depth were clearly increased in the zaleplon 10 mg group(P<0.05).Moreover,the SE and the percent of REM(rapid eye movement) sleep were increased remarkably in the zaleplon 15 mg group(P<0.01).Furthermore,the SE,percent of REM sleep and scores of subjective sleep depth in the zaleplon 15 mg group were significantly higher than in the zaleplon 10 mg group(P<0.05).The psychomotor performance did not change significantly after ingestion of 10 mg or 15 mg of zaleplon,whereas the OKN and VOR gains were lower in the two dose groups of zaleplon(P<0.05) and restored to normal 3h after drug ingestion.Conclusion:Zaleplon is an ideal hypnotic for military personnel,and its hypnotic efficiency is dose-related under noise interference; a 15 mg dose of zaleplon could provide significantly better sleep than a 10 mg dose of zaleplon.
基金Project supported by the National Natural Science Foundation of China(No.11502284)the Tianjin Natural Science Foundation(No.15JCQNJC42600)+1 种基金the Fundamental Research Funds for the Central Universities of China(No.3122014C015)the open fund of the airport project(No.JCGC2015KFJJ005)
文摘An analytical solution is obtained for the Functionally Graded Shape Memory Alloy （FG-SMA） composites subjected to thermo-mechanical coupling. Young＇s modulus and thermal expansion coefficient of the material are assumed to vary in different forms of power function through the thickness, with the Poisson＇s ratio being constant. An SMA constitutive model is combined with the averaging techniques of composite to determine the mechanical properties of the FG-SMA composites. Different phase transformation steps and the corresponding stress distributions through the thickness direction are given. The results show that the average stresses decrease as the transformations proceed.
基金The authors thank Xin-Quan Shi, De-Yu Liu, Da-Guang Sun, Hong-Fei Xia, Qian-Xin Wang, Chong Wang, Dan Li, Xiang-Bo Xu, Yong-Jie Chang and Nan Yao for technical assistance. This work was supported by the National Natural Science Foundation of China （No. 30670784）.
文摘LM23 is a gene specifically expressed in the testis of Rattus norvegicus, as previously reported by our laboratory. The aim of the study is to further investigate the biological function of LM23. Several bioinformatic tools were utilized, including PROSITE and BLAST. To determine the subcellullar localization of LM23, a polyclonal antibody specific for LM23 was generated via the immunization of rabbits. The LM23gene was cloned from rat testis tissue, and LM23 protein was expressed in Escherichia co/i. The biological function of LM23 was analyzed with microarray analysis and immunohistochemistry, using a rat model of LM23 gene knockdown. The results suggested that LM23 belongs to the Speedy/Ringo family. LM23 regulated the GI/S and G2/M transitions of the cell cycle during spermatogenesis. Downregulation of the LM23gene during spermatogenesis could lead to the activation of both the Fas-FasL pathway and the mitochondrial pathway. These novel findings indicate that LM23 has a diverse array of functions that are important in both the life and death of the spermatogenic cell.
基金financially supported by the National Natural Science Foundation of China(No.51971242)the Tianjin Science and Technology Planning Project(No.20YDTPJC01600)。
文摘The integrity and regularity of pore morphology play an important role in determining the mechanical properties of the metallic foam materials.The conventional methods on refining pore morphology are mainly focused on the optimization of fabrication techniques,however,they are usually inconvenient and complicated.Recently,incorporating nano reinforcement is considered to be a suitable way to fabricate metallic composite foams accompanied by optimized pore morphology and enhanced mechanical properties.In this work,through a facile and rapid powder metallurgy foaming method,the aluminum-silicon(Al-Si)alloy composite foams reinforced by graphene nanosheets(GNSs)are successfully fabricated.The microstructure analyses reveal that,for the Al-Si alloy foams incorporating the GNSs(GNSs/Al-Si composite foams),the pore size is transformed to be smaller,the pore size distributions become more homogeneous and the pore shape is also refined to a regular and roundish state.Meanwhile,the shape of Si precipitates is found transforming from an irregular long strip(length of~20μm,width of~5μm)to a fine particle state(diameter of~5μm).Moreover,the compressive testing results show that,the 0.4wt%GNSs/Al-Si composite foams own the optimal compression stress of 11.7±0.5 MPa,plateau stress of 10.0±1.0 MPa and energy absorption capacity of 6.8±0.7 MJ/m^(3),which have improvement of 58.1%,53.8%and 51.1%in comparison with the Al-Si alloy foams counterpart,respectively.The present findings may pave a new way for developing new generation of metallic composite foams that with stable microstructure and excellent mechanical performance.
基金Supported by the Research Grant of Guangxi Natural Science Foundation(No.2015GXNSFCB139012No.2017GXNSFBA198320)the Research Grant of Guangxi Technology and Science Agency(No.Z2015316)
文摘AIM： To compare the optical quality after implantation of implantable collamer lens（ICL） and wavefront-guided laser in situ keratomileusis（WG-LASIK）.METHODS： The study included 40 eyes of 22 patients with myopia who accepted ICL implantation and 40 eyes of 20 patients with myopia who received WG-LASIK. Before surgery and three months after surgery, the objective scattering index（OSI）, the values of modulation transfer function（MTF） cutoff frequency, Strehl ratio, and the Optical Quality Analysis System（OQAS） values（OVs） were accessed. The higher order aberrations（HOAs） data including coma, trefoil, spherical, 2^（nd） astigmatism and tetrafoil were also obtained. For patients with pupil size 〈6 mm, HOAs data were analyzed for 4 mm-pupil diameter. For patients with pupil size ≥6 mm, HOAs data were calculated for 6 mm-pupil diameter. Visual acuity, refraction, pupil size and intraocular pressures were also recorded.RESULTS： In both ICL and WG-LASIK group, significant improvements in visual acuities were found postoperatively, with a significant reduction in spherical equivalent（P〈 0.001）. After the ICL implantation, the OSI decreasedslightly from 2.34±1.92 to 2.24±1.18 with no statistical significance（P=0.62）. While in WG-LASIK group, the OSI significantly increased from 0.68±0.43 preoperatively to 0.91±0.53 postoperatively（Wilcoxon signed ranks test, P=0.000）. None of the mean MTF cutoff frequency, Strehl ratio, OVs showed statistically significant changes in both ICL and WG-LASIK groups. In the ICL group, there were no statistical differences in the total HOAs for either 4 mmpupil or 6 mm-pupil. In the WG-LASIK group, the HOA parameters increased significantly at 4 mm-pupil. The total ocular HOAs, coma, spherical and 2^（nd） astigmatism were 0.12±0.06, 0.06±0.03, 0.00±0.03, 0.02±0.01, respectively. After the operation, these values were increased into 0.16±0.07, 0.08±0.05,-0.04±0.04, 0.03±0.01 respectively（Wilcoxon signed ranks test, all P〈0.05）. At 6 mm-pupil, the induction of total HOAs was not statistically significant in the WG-LASIK group. CONCLUSION： ICL implantation has a less disturbance to optical quality than WG-LASIK. The OQAS is a valuable complementary measurement to the wavefront aberrometers in evaluating the optical quality.
文摘Objective Global cardiovascular risk assessment has been incorporated into current Chinese guidelines for the management of hypertension and hypercholesterolemia. The aim of our study is to determine the distribution of 10-year risk for ischemic cardiovascular disease （ICVD） among middle-aged Chinese adults, and to evaluate the usefulness of global risk assessment tools in the primary prevention of ICVD in Chinese population.Methods Simplified prediction tools derived from the USA-PRC Collaborative Study of Cardiovascular Epidemiology cohort were applied to the Chinese Health Examination Database （CHED） 2008. 10-year risk for ICVD was estimated in 461 157 ICVD-free subjects （264 432 male and 196 725 female） aged 35 to 59 years. Results Among the male subjects, 82.4% had a 10-year risk for ICVD of 〈5%, 14.4% of 5% to 12.1% and 3.4 of≥ 12.2%, and in female subjects, 86.7% had a 10-year risk for ICVD of 〈5%, 12.1% of 5% to 12.0% and 1.2% of ≥ 12.1%. All subjects with predicted high level ICVD risk （≥ 12.2% in male or ≥ 12.1% in female） had either remarkably elevated （≥ 160 mmHg） blood pressure, significantly increased （≥ 6.22 mml/L） total serum cholesterol or diabetes.Conclusion Using the currently recommended prediction tools, only very small proportions of middle-aged Chinese men and women who were free of ICVD would be classified into high level risk group. These prediction tools are unlikely to help for the medical intervention decision making in Chinese adult patients with hypertension and/or hypercholesterolemia
基金Supported by the National Natural Science Foundation of China under Grant Nos.11105097,10975075,and 11175089the National Basic Research Program of China under Grant No.2012CB921900the National Research Foundation and Ministry of Education,Singapore under Grant No.WBS:R-710-000-008-271
文摘The orbits and the dynamical symmetries for the screened Coulomb potentials and isotropic harmonic oscillators have been studied by Wu and Zeng [Z.B. Wund J.Y. Zeng, Phys. Rev. A 62 （2000） 032509]. We find similar properties in the corresponding systems in a sphericM space, whose dynamical symmetries are described by Higgs algebra. There exist extended Runge-Lenz vector for screened Coulomb potentials and extended quadruple tensor for screened harmonic oscillators. They, together with angular momentum, constitute the generators of the geometrical symmetry group. Moreover, there exist an infinite number of dosed orbits for suitable angular momentum values, and we give the equations of the classical orbits. The eigenenergy spectrum and corresponding eigenstates in these systems are derived.
基金supported by grants from the National Science Centre,Poland(NCN)No.UMO-2017/25/B/ST8/00134 and UMO2015/19/D/ST8/00818supported by the Polish-JINR Programme 2017(item 24)supported by the Federal Ministry for Education and Research in Germany。
文摘In this work,the evolutions of stresses in both phases of the Al/SiCp composite subjected to thermal cycling during in situ compression test were measured using Time of Flight neutron diffraction.It was confirmed that inter-phase stresses in the studied composite can be caused by differences in the coefficient of thermal expansion for the reinforcement and matrix,leading to a different variation of phase volumes during sample heating or cooling.The results of the diffraction experiment during thermal cycling were well predicted by the Thermo-Mechanical Self-Consistent model.The experimental study of elastic-plastic deformation was carried out in situ on a unique diffractometer EPSILON-MDS(JINR in Dubna,Russia)with nine detector banks measuring interplanar spacings simultaneously in 9 orientations of scattering vector.For the first time,the performed analysis of experimental data allowed to study the evolution of full stress tensor in both phases of the composite and to consider the decomposition of this tensor into deviatoric and hydrostatic components.It was found that the novel Developed Thermo-Mechanical SelfConsistent model correctly predicted stress evolution during compressive loading,taking into account the relaxation of thermal origin hydrostatic stresses.The comparison of this model with experimental data at the macroscopic level and the level of phases showed that strengthening of the Al/SiCp composite is caused by stress transfer from the plastically deformed A12124 matrix to the elastic SiCp reinforcement,while thermal stresses relaxation does not significantly affect the overall composite properties.
基金Sponsored by the National Natural Science Foundation of China ( Grant No 60879018)
文摘Thermal barrier coating ( TBC) consisting of a NiCoCrAlY bond coat ( BC) and a ZrO2-8 wt. % Y2O3 topcoat ( TC) was fabricated on the nickel-base superalloy by air plasma spray ( APS) . The BC was treated by supersonic fine particle bombarding ( SFPB) . Thermal cyclic failure and residual stress in thermally grown oxide ( TGO) scale were studied by SEM with EDS and ruby fluorescence spectroscopy ( RFS) . As shown in the results,after treated by SFPB,thickening of TGO was relatively slow,which reduced the level of growth stress. The TBC with SFPB treatment was still remained well undergoing 350 times of thermal cycle. However,after thermal cycle with the same times,the separation of TC was observed in TBC without SFPB treatment. The residual stress analysis by RFS showed that the residual stress of SFPB-treated TBC increased with the increasing number of thermal cycle. The residual stress of conventional TBC reached a value of 650 MPa at 350 times of cycle and that of SFPB-treated TBC only reached 532 MPa at 400 times of cycle. The BC with SFPB treatment after 400 times of cycle was analyzed by RFS,the high stress value was not observed in local thickened region of TGO. Thermal cycling resistance of TBC can be improved by the SFPB technology.
基金financially supported by the National Natural Science Foundation of China(No.51971242)the Provincial School Science and Technology Cooperation Development Fund Project of Hebei Province of China。
文摘As widely used protective materials,the application of Al foams is still limited by their low intrinsic mechanical properties caused by the brittleness of struts.The introduction of Mg is recently demonstrated effective to improve the mechanical performance of Al foams;however,the mechanism of Mg modification is still not clear.In this work,Al-Mg foams are developed through a powder metallurgy process with excellent compression performance and high energy absorption capacity.The effects of Mg modification on the cell structure,toughness,and deformation behavior are investigated systematically.As a result,the small cell size of~1.8 mm and the high sphericity of 0.92 are achieved with 5% of Mg addition,delivering high compression stress of 8.5±0.43 MPa and energy absorption capacity of 6.9±0.36 MJ/m^(3),simultaneously.The synergistic mechanism for the improved mechanical performance is also demonstrated to be the combination of stress transfer and plastic deformation behavior of cells.The results provide a new strategy to develop high-performance foam materials by improving toughness and further promote the practical application.
基金the financial support provided by the National Natural Science Foundation of China (NSFC No. U1733120, 61601469, 61674114, 61701475, 91743110, 21861132001)National Key R&D Program of China (2017YFF0204604, 2018YFE0118700)+4 种基金Tianjin Applied Basic Research and Advanced Technology (17JCJQJC43600)the 111 Project (B07014)the Initial Scientific Research Fund of State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University (No. Pilq1902)the Foundation for Talent Scientists of Nanchang Institute for Micro-technology of Tianjin Universitythe Open Research Fund of Key Laboratory of MEMS of Ministry of Education, Southeast University。
文摘To address the need for the on-site measurement of aging oil, in this paper, we propose an impedance-based microsensor for analyzing the moisture content in engine oil. Using a microfabrication process, we fabricated an interdigitated microelectrode and integrated it with a 3 D-printed microcontainer to produce a microsensor that can detect changes in the permittivity of oil. When the moisture content in oil increases, this sensor can detect the resulting change in the oil impedance, which is related to its permittivity, and then determine the degree to which the oil has aged. The test results show that the proposed microsensor has the advantages of being small and having high sensitivity, good accuracy, and the ability to be combined with hand-held instruments.The proposed method is expected to be used for the rapid, low cost, on-site determination of oil aging.
基金Project supported by the National Natural Science Foundation of China(Grant No.51201181)the Scientific Research Fund of Civil Aviation University of China(Grant No.08QD14X)
文摘First-principles calculations based on the density functional theory（DFT） and ultra-soft pseudopotential are employed to study the atomic configuration and charge density of impurity P in Ni Al Σ5 grain boundary（GB）. The negative segregation energy of a P atom proves that a P atom can easily segregate in the Ni Al GB. The atomic configuration and formation energy of the P atom in the Ni Al GB demonstrate that the P atom tends to occupy an interstitial site or substitute a Al atom depending on the Ni/Al atoms ratio. The P atom is preferable to staying in the Ni-rich environment in the Ni Al GB forming P–Ni bonds. Both of the charge density and the deformation charge imply that a P atom is more likely to bond with Ni atoms rather than with Al atoms. The density of states further exhibits the interactions between P atom and Ni atom, and the orbital electrons of P, Ni and Al atoms all contribute to P–Ni bonds in the Ni Al GB. It is worth noting that the P–Ni covalent bonds might embrittle the Ni Al GB and weakens the plasticity of the Ni Al intermetallics.
文摘Highly concentrated hydrogen peroxide has been widely used as a rocket mono-propellant and oxidiser since 1940＇s. Although the relevant specialist literature concerning HTP is relatively extensive, one can still find many myths about highly concentrated hydrogen peroxide, especially concerning safety aspects about its preparation by different techniques, handling or further utilisation. Such ambiguities can result in rather apprehensive approach towards preparing, utilising or even handling of HTP in relevant industry or research fields. The paper contains modern approach to laboratory preparation of highly concentrated solutions of hydrogen peroxide of HTP class （concentration 98%＋） that is intended for propulsive （rocket） applications. Authors, who have gained extensive experience in the field of HTP preparation, handling and utilisation, concisely explain facts and disprove some common myths concerning HTP. Additionally, advantages and possible application of 98%＋ solutions of HTP in various propulsive systems such as small satellites are described. The attention is also paid to the possibility of replacing currently used toxic and corrosive rocket propellants, such as hydrazine and its derivatives, RFNA （red fuming nitric acid）, MON （mixed oxides of nitrogen） or NTO （dinitrogen tetroxide）, by 98%＋ HTP. The potential of the medium as green and easy to handle propellant that can act both, as monopropellant or strong liquid oxidiser with hypergolic capability, is outlined briefly as well.
基金Project supported by the grant of the Russian Science Foundation(Project No.22-29-00124)。
文摘A concise analytical model for the static dipole polarizability of ionized atoms and molecules is created for the first time.As input,it requires,alongside the polarizability of neutral counterpart of a given ion,only the charge and elemental composition.This physically motivated semiempirical model is based on a number of established regularities in polarizability of charged monatomic and polyatomic compounds.In order to adjust it,the results of quantum chemistry calculations and gas-phase measurements available for a broad range of ionized multielectron species are employed.To counteract the appreciable bias in the literature data toward polarizability of monoatomic ions,for some molecular ions of general concern the results of the authors'own density functional theory calculations are additionally invoked.A total of 541 data points are used to optimize the model.It is demonstrated that the model we suggested has reasonable(given the substantial uncertainties of the reference data)accuracy in predicting the static isotropic polarizability of arbitrarily charged ions of any size and atomic composition.The resulting polarizability estimates are found to achieve a coefficient of determination of 0.93 for the assembled data set.The created analytic tool is universally applicable and might be advantageous for some applications where there is an urgent need for rapid low-cost evaluation of the static gas-phase polarizability of ionized atoms and molecules.This is especially relevant to constructing the complex models of nonequilibrium chemical kinetics aimed at precisely describing the observable refractive index(dielectric permittivity)of plasma flows.The data sets that support the findings of this study are openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.07526.
基金supported by the grant of the Russian Science Foundation(project No.22-29-00124)。
文摘We present a semiempirical analytical model for the static polarizability of electronically excited atoms and molecules,which requires very few readily accessible input data,including the ground-state polarizability,elemental composition,ionization potential,and spin multiplicities of excited and ground states.This very simple model formulated in a semiclassical framework is based on a number of observed trends in polarizability of electronically excited compounds.To adjust the model,both accurate theoretical predictions and reliable measurements previously reported elsewhere for a broad range of multielectron species in the gas phase are utilized.For some representative compounds of general concern that have not yet attracted sufficient research interest,the results of our multireference second-order perturbation theory calculations are additionally engaged.We show that the model we developed has reasonable(given the considerable uncertainties in the reference data)accuracy in predicting the static polarizability of electronically excited species of arbitrary size and excitation energy.These findings can be useful for many applications,where there is a need for inexpensive and quick assessments of the static gas-phase polarizability of excited electronic states,in particular,when building the complex nonequilibrium kinetic models to describe the observed optical refractivity(dielectric permittivity)of nonthermal reacting gas flows.
